Orthopedic MCQs: Fracture, Spine, Tumor Board Prep - Part 32

Question 1

Which of the following tumors is most likely to present with a pathologic fracture in a child?

Explanation

DISCUSSION: In nearly 50% of patients with a unicameral bone cyst, the lesion remains asymptomatic until a fracture occurs, usually as the result of relatively minor trauma. If the lesion expands, the bone is weakened and may cause pain. Fibrous cortical defects are usually an incidental finding and typically asymptomatic. Malignant bone tumors such as osteosarcoma and Ewing’s sarcoma most commonly cause pain, and pathologic fracture occurs in less than 10% of patients. Giant cell tumors are uncommon in children and usually are painful.
REFERENCES: Wilkins RM: Unicameral bone cysts. J Am Acad Orthop Surg 2000;8:217-224.
Dormans JP, Pill SG: Fractures through bone cysts: Unicameral bone cysts, aneurysmal bone cysts, fibrous cortical defects, and nonossifying fibromas. Instr Course Lect 2002;51:457-467.
Hecht AC, Gebhardt MC: Diagnosis and treatment of unicameral and aneurysmal bone cysts in children. Curr Opin Pediatr 1998;10:87-94.

Question 2

A 60-year-old woman has a mass in the right scapula. Figures 25a and 25b show a CT scan and a biopsy specimen. The cells are lymphocyte common antigen positive, Ewing’s specific antigen (CD99) negative, and keratin negative. What is the next step in management?

Explanation

DISCUSSION: The clinical history, CT scan, and histology are most consistent with a lymphoma of bone. An important part of the staging is bone marrow aspiration and biopsy. The other studies listed are not indicated. Lymphoma of bone, when localized, is usually treated with chemotherapy and radiation therapy and has excellent survival rates. Widespread lymphoma has a worse prognosis.
REFERENCES: Finiewicz K, van Biesen K: Non-Hodgkins lymphoma, in Golomb H, Vokes E (eds): Oncologic Therapies, ed 2. Berlin, Germany, Springer, 2003, pp 295-318.
Lems P, Primus G, Anastas J, Doherty D, Montag AG, Peabody TD, Simon MA: Oncologic outcomes of primary lymphoma of bone in adults. Clin Orthop 2003;415:90-97.

Question 3

The use of multiagent adjuvant chemotherapy is associated with a clear survival benefit in which of the following diseases?

Explanation

DISCUSSION: The use of multiagent chemotherapy has been shown to be associated with a survival benefit in patients with osteosarcoma. The use of chemotherapy in adults with soft-tissue sarcoma remains somewhat controversial. It has not been associated with improved survival rates in patients with renal carcinoma, dedifferentiated chondrosarcoma, or melanoma.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 53.
Link M, Goorin A, Miser A, et al: The effect of adjuvant chemotherapy and relapse free survival in patients with osteosarcoma of the extremity. N Engl J Med 1986;314:1600-1606.

Question 4

Which of the following definitions best describes Batson’s vertebral vein system?

Explanation

DISCUSSION: The venous plexus was described by Batson and helps to explain the common distribution of metastatic cells to the vertebrae, skull, ribs, and proximal long bones. Batson studied the vertebral vein system extensively by using contrast agents in human cadavers and live monkeys. Batson’s plexus is a valveless system that allows retrograde embolism from the major organs such as the breast, prostate, lung, kidney, and thyroid. It is located within the thoracoabdominal cavity and has connections to the proximal long bones and an intercommunicating network of thin-walled veins with a low intraluminal pressure.
REFERENCES: Batson OV: Function of vertebral veins and their role in spread of metastases. Ann Surg 1940;112:138-149.
Coman DR, de Long RP: Role of vertebral venous system in metastasis of cancer to spinal column: Experiments with tumor-cell suspensions in rats and rabbits. Cancer 1951;4:610-618.

Question 5

Figure 26 shows the radiograph of a 48-year-old woman who has right arm pain and hematuria. A bone scan reveals increased uptake in the left ribs and thoracic spine. A needle biopsy specimen shows that the lesion is highly keratin positive and composed primarily of clear cells. What is the best course of action?

Explanation

DISCUSSION: The lesion has the typical “blown out” lytic radiographic appearance that is most commonly found in thyroid or renal cell metastases. Given the history of hematuria and histology findings, the most likely diagnosis is metastatic renal cell carcinoma. This tumor is relatively resistant to chemotherapy. Radiation therapy is used as a postoperative adjuvant treatment with varying response rates. Surgery should be performed after preoperative embolization to decrease the risk of intraoperative bleeding, as no tourniquet can be used in this location. Patients with metastatic renal cell carcinomas may survive for years, resulting in a higher likelihood of local tumor progression with ineffective adjuvant therapy. Intramedullary fixation combined with curettage and cementation will provide the best chance of local control while maintaining the patient’s native shoulder and elbow joints. A total humeral resection is an extensive surgery with considerable morbidity and is not indicated for this patient because less extensive surgery is likely to be effective.
REFERENCES: Harrington KD, Sim FH, Enis JE, Johnston JO, Diok HM, Gristina AG: Methylmethacrylate as an adjunct in internal fixation of pathological fractures: Experience with three hundred and seventy-five cases. J Bone Joint Surg Am 1976;58:1047-1054.
Sun S, Lang EV: Bone metastases from renal cell carcinoma: Preoperative embolization. J Vasc Interv Radiol 1998;9:263-269.
Katzner M, Schvingt E: Operative treatment of bone metastases secondary to renal carcinoma: Basic research and treatment of renal cell carcinoma metastasis. Prog Clin Biol Res EORTC 1990;348:151-168.

Question 6

A 15-year-old boy has had pain in the right shoulder for the past 3 months. He denies any history of trauma and has no constitutional symptoms. Examination reveals a large firm mass in the proximal arm. A radiograph and MRI scan are shown in Figures 27a and 27b. Biopsy specimens are shown in Figures 27c and 27d. Management should consist of

Explanation

DISCUSSION: The patient has an aneurysmal bone cyst. The fluid-fluid levels seen on the MRI scan are typical for aneurysmal bone cyst, and the histology is consistent with a cystic lining. Vascular lakes, multinucleated giant cells, reactive bone, fibrovascular tissue, and an absence of atypical cells or numerous mitoses are seen histologically. Aneurysmal bone cysts will typically continue to grow and cause further bone destruction; therefore, observation is not recommended. Steroid injections are not effective. A thorough curettage of the cyst lining and bone grafting are required. Wide resection and chemotherapy are reserved for more aggressive tumors. There is no evidence of infection radiographically or histologically. Telangiectatic osteosarcoma should also be considered in the differential diagnosis; therefore, biopsy is an important part of the work-up.
REFERENCES: Wold LA, et al: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 232-233.
Simon M, et al: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, pp 194-196.

Question 7

A 38-year-old woman with metastatic thyroid carcinoma has had increasing pain in the left hip for the past 3 months. An AP radiograph and coronal T 1 -weighted MRI scan are shown in Figures 28a and 28b. Management should consist of

Explanation

DISCUSSION: The radiograph and MRI scan reveal a lytic lesion in the left femoral neck region that extends to the lesser trochanter. Although external beam radiation and radioactive iodine infusion may be helpful in controlling the local disease, the patient is at high risk for femoral neck fracture given the location of the lesion. Prophylactic surgery is indicated; therefore, the treatment of choice is a cemented bipolar hemiarthroplasty. The use of a compression hip screw and side plate or an intramedullary nail has a high likelihood of failure with disease progression. Postoperative treatment with radiation therapy and bisphosphonates is also indicated.
REFERENCES: Mirels H: Metastatic disease in long bones: A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop 1989;249:256-264.
Swanson KC, Pritchard DJ, Sim FH: Surgical treatment of metastatic disease of the femur. J Am Acad Orthop Surg 2000;8:56-65.
Clarke HD, Damron TA, Sim FH: Head and neck replacement endoprosthesis for pathologic proximal femoral lesions. Clin Orthop 1998;353:210-217.

Question 8

What is the most common location of osteosarcoma?

Explanation

DISCUSSION: The most common location of osteosarcoma is the knee area (50% to 55%), followed by the proximal humerus and iliac wing. The most commonly involved long bone is the femur (40% to 45%), followed by the tibia (15% to 25%). Within these bones, tumors are typically adjacent to the epiphyses in most patients. The flat bones of the pelvis and spine are less frequently involved.
REFERENCES: Malawer MM, Sugarbaker PH, Malawer M: Musculoskeletal Cancer Surgery: Treatment of Sarcomas and Allied Diseases. Kluwer Academic Publishers, 2001.
Wold LA, et al: Osteogenic Sarcoma: Atlas of Orthopedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 14-15.

Question 9

A 40-year-old man with an acetabular chondrosarcoma has a small soft-tissue mass. Treatment should consist of

Explanation

DISCUSSION: The treatment of choice for pelvic chondrosarcoma is wide resection via an internal hemipelvectomy. Chondrosarcoma requires surgical resection for control and does not respond to traditional chemotherapy or external beam radiation. Hip arthroplasty with acetabular reconstruction and curettage and cementation of the lesion are intralesional procedures that result in a higher incidence of local recurrence of tumor.
REFERENCES: Pring M, Weber KL, Unni K, Sim FH: Chondrosarcoma of the pelvis: A review of sixty-four cases. J Bone Joint Surg Am 2001;83:1630-1642.
Sheth DS, Yasko AW, Johnson ME, Ayala AG, Murray JA, Romsdahl MM: Chondrosarcoma of the pelvis: Prognostic factors for 67 patients treated with definitive surgery. Cancer 1996;78:745-750.

Question 10

Figures 29a and 29b show the AP radiograph and CT scan of a 70-year-old man who has left thigh pain. Serum protein electrophoresis shows a monoclonal gammopathy. Additional radiographs of the femur show other lesions. Management should consist of

Explanation

DISCUSSION: The underlying diagnosis is multiple myeloma. Because the patient has a large lucent lesion in the peritrochanteric region of the left proximal femur, the risk of pathologic fracture is high. Consideration should be given to prophylactic internal fixation with a locked intramedullary rod. The lesion does not appear to be a sarcoma requiring wide resection and endoprosthetic reconstruction. Neither chemotherapy nor radiation therapy alone is likely to result in long-term stabilization of the proximal femur. Postoperative treatment with bisphosphonates and radiation therapy is indicated to decrease the risk of future pathologic fractures. The patient should also be referred to a medical oncologist for medical management.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 364.
Mirels H: Metastatic disease in long bones: A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop 1989;249:256-264.

Question 11

What pharmacologic agents are preferred for the treatment of symptomatic active Paget’s disease?

Explanation

DISCUSSION: Recent medical literature supports the use of bisphosphonates as the treatment of choice for active Paget’s disease.
REFERENCE: Delman PD, Meunier PJ: The management of Paget’s disease. N Eng J Med 1997;336:558-566.

Question 12

A 7-year-old girl has pain and a mass in the left scapula. A MRI scan and biopsy specimen are shown in Figures 30a and 30b. After staging studies, initial management should consist of

Explanation

DISCUSSION: The histology shows small round blue cells that are uniform in appearance; these findings are consistent with Ewing’s sarcoma. The MRI scan shows infiltration of the marrow and a large surrounding soft-tissue mass. Based on these findings, the management of choice is systemic chemotherapy. Local control of the primary lesion is addressed by either surgical resection or radiation therapy or a combination of the two after the patient receives systemic chemotherapy. The clinical, radiographic, and histologic presentation of Ewing’s sarcoma often can be confused with osteomyelitis. The histology shows an absence of inflammatory cells.
REFERENCES: Grier HE: The Ewing family of tumors: Ewing’s sarcoma and primitive neuroectodermal tumors. Pediatr Clin North Am 1997;44:991-1004.
Arndt CA, Crist WM: Common musculoskeletal tumors of childhood and adolescence. N Engl J Med 1999;341:342-352.

Question 13

A 73-year-old man reports increasing back and lower extremity pain. A bone scan is shown in Figure 31. What is the most likely diagnosis?

Explanation

DISCUSSION: The bone scan reveals lesions throughout the skeleton. The patient’s age, gender, and pain pattern are consistent with metastatic prostate cancer. Multiple myeloma typically does not have enough osteoblastic activity to produce this bone scan. The patient’s age is not consistent with metastatic neuroblastoma (a pediatric disease). Polyostotic fibrous dysplasia may involve multiple active lesions in younger patients but does not have such a widespread distribution of lesions. Hodgkin’s lymphoma can involve bone, but the widespread discrete appearance on this bone scan is most consistent with metastatic prostate cancer. In a patient with widespread bone metastases from prostate cancer, bisphosphonates may play a critical role in treatment by decreasing pain and the number of fractures.
REFERENCES: Roudier MP, Vesselle H, True LD, Higano CS, Ott SM, King SH, Vessella RL: Bone histology at autopsy and matched bone scintigraphy findings in patients with hormone refractory prostate cancer: The effect of bisphosphonate therapy on bone scintigraphy results. Clin Exp Metastasis 2003;20:171-180.
Sartor O: Radioisotopic treatment of bone pain from metastatic prostate cancer. Curr Oncol Rep 2003;5:258-262.

Question 14

A 16-year-old girl has had pain in the left groin for the past 4 months. She notes that the pain is worse at night; however, she denies any history of trauma and has no constitutional symptoms. There is no history of steroid or alcohol use. Examination reveals pain in the left groin with rotation of the hip. There is no associated soft-tissue mass. A radiograph and MRI scan are shown in Figures 32a and 32b, and biopsy specimens are shown in Figures 32c and 32d. What is the most likely diagnosis?

Explanation

DISCUSSION: Based on the epiphyseal location and sharp, well-defined borders, the radiograph suggests chondroblastoma. Histologically, multinucleated giant cells are scattered among mononuclear cells. The nuclei are homogenous and contain a characteristic longitudinal groove. Although not seen here, “chicken-wire calcification” with a bland giant cell-rich matrix is also typical for chondroblastoma. Clear cell chondrosarcoma occurs in epiphyseal locations but has a more aggressive histologic pattern and occurs in an older age group. Giant cell tumors occur in the epiphysis but have a more uniform giant cell population histologically. Aneurysmal bone cyst often results in bone remodeling and has a different pathologic appearance. Osteonecrosis has a typical histologic pattern of empty lacunae and necrotic bone.
REFERENCES: Springfield DS, Capanna R, Gherlinzoni F, et al: Chondroblastoma: A review of seventy cases. J Bone Joint Surg Am 1985;67:748-755.
Simon M, Springfield D, et al: Chrondroblastoma: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, p 190.
Wold LA, et al: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990,
pp 62-67.

Question 15

Ewing’s sarcoma of bone most commonly occurs in which of the following locations?

Explanation

DISCUSSION: Ewing’s sarcoma typically occurs in the major long tubular bones, with the femur the most common location. The flat bones of the pelvis are the second most common location. Ewing’s sarcoma occurs in the fibula but with a lower incidence than that seen in the major tubular bones. Ewing’s sarcoma infrequently occurs in the metacarpals or the vertebral bodies.
REFERENCES: Simon M, Springfield D, et al: Ewing’s Sarcoma: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, p 287.
Wold LA, et al: Ewing’s Sarcoma: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 210-211.

Question 16

A previously healthy 14-year-old boy now reports fatigue, and has a bilateral Trendelenburg gait, right hip pain, and bilateral knee and foot pain. Biopsy of a right sacral mass reveals intermediate grade osteosarcoma. There are no metastases. Laboratory studies reveal a serum calcium level of 7.7 mg/dL (normal 8.5 to 10.5), a phosphate level of 2.0 mg/dL (normal 2.7 to 4.5), a 1,25-dihydroxyvitamin D level of less than 10 pg/mL (normal 18 to 62), a parathyroid hormone level of 19 pg/mL (normal 10 to 60), and an alkaline phosphatase level of 428 U/L (normal 15 to 351). What is the most likely cause of the patient’s symptoms?

Explanation

DISCUSSION: The laboratory findings are typical for rickets. Oncogenic rickets is a paraneoplastic syndrome that results from a substance secreted by the tumor that interferes with renal tubule reabsorption of phosphate. This substance previously had been called phosphatonin but recently has been identified as fibroblast growth factor 23. Nutritional rickets is rare in developed countries. Delayed onset familial hypophosphatemic rickets is possible, but the likelihood of having two rare diseases is unlikely. Osteosarcoma does not sequester calcium. Alkaline phosphatase levels can be elevated in osteosarcoma but does not cause muscle weakness. Tumor cachexia would occur only with advanced metastatic disease. A unilateral sacral mass would not cause a bilateral L5 neuropathy or the abnormal laboratory findings.
REFERENCES: Case records of the Massachusetts General Hospital. Weekly clinicopathological exercises. Case 29-2001. A 14-year-old with abnormal bones and a sacral mass. N Engl J Med 2001;345:903-908.
Jonsson KB, Zahradnik R, Larsson T, White KE, Sugimoto T, Imanishi Y, et al: Fibroblast growth factor 23 in oncogenic osteomalacia and X-linked hypophosphatemia. N Engl J Med 2003;348:1656-1663.

Question 17

Which of the following staging studies should be obtained for an adult with an 8-cm deep, high-grade malignant fibrous histiocytoma of the extremity?

Explanation

DISCUSSION: MRI is the preferred imaging study to evaluate the local tumor extension for soft-tissue lesions, but CT can be used if MRI is contraindicated (eg, patients with pacemakers). CT of the chest is always recommended in patients with high-grade sarcomas because 80% of metastases occur in the lungs. CT of the abdomen and pelvis is indicated in patients with lower extremity liposarcoma because some patients also have synchronous retroperitoneal liposarcoma. Lymph node metastasis occurs in up to 5% of patients with soft-tissue sarcoma. If the nodes are clinically enlarged, biopsy is indicated. Routine sentinel node biopsy currently is not recommended. Bone scan is not used in the staging of soft-tissue sarcoma as it has not been shown to be cost-effective.
REFERENCES: Demetri GD, Pollock R, Baker L, Balcerzak S, Casper E, Conrad C, et al: NCCN sarcoma practice guidelines: National Comprehensive Cancer Network. Oncology (Huntingt) 1998;12:183-218.
Pollack R, Brennan M, Lawrence W, Jr: Society of Surgical Oncology practice guidelines: Soft-tissue sarcoma surgical practice guidelines. Oncology (Huntingt) 1997;11:1327-1332.

Question 18

An 18-year-old boy has had pain in the right knee for the past 6 months. Examination reveals some fullness behind the knee but no significant palpable soft-tissue mass. There is no effusion, and he has full knee range of motion. The remainder of the examination is unremarkable. A radiograph and MRI scans are shown in Figures 33a through 33c, and biopsy specimens are shown in Figures 33d and 33e. What is the most likely diagnosis?

Explanation

DISCUSSION: The patient has parosteal osteosarcoma. The posterior aspect of the distal femur is the typical location for this variant of osteogenic sarcoma. The imaging studies indicate a surface lesion with no involvement of the adjacent intramedullary canal. The histologic appearance is that of a low-grade fibroblastic osteosarcoma, consisting of relatively mature bone and a bland fibroblastic stroma lacking cytologic atypia and mitotic activity. A cartilaginous component is also frequently seen. Classic osteosarcoma typically has a more aggressive radiologic and histologic appearance. Sessile osteochondromas, while common behind the knee, have a presence of hematopoietic marrow and fat. The cartilage found in the associated cartilaginous cap is oriented. Chondrosarcomas are more typical in an older age group and have a histologic pattern consisting of malignant chondroid.
REFERENCES: Wold LA, et al: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 20-21.
Unni KK, Dahlin DC, Beabout JW, Ivins JC: Parosteal osteogenic sarcoma. Cancer 1976;37:2466-2475.

Question 19

A 30-year-old patient has wrist pain. A radiograph and biopsy specimen are shown in Figures 34a and 34b. What is the most likely diagnosis?

Explanation

DISCUSSION: Aneurysmal bone cysts typically present as radiolucent lesions with an expansile remodeled cortex. The histologic appearance consists of blood-filled lakes surrounded by a benign lining that contains fibroblasts, giant cells, and hemosiderin. Although the other lesions are in the radiographic differential diagnosis, these histologic findings indicate an aneurysmal bone cyst.
REFERENCES: Bieselker JL, Marcove RC, Huvos AG, Mike V: Aneurysmal bone cyst: A Clinico-pathologic study of 66 cases. Cancer 1973;26:615.
Martinez V, Sissons HA: A review of 123 cases including primary lesions and those secondary to other bone pathology. Cancer 1988;61:2291.

Question 20

Mutations of what gene are associated with subsequent development of osteosarcoma?

Explanation

DISCUSSION: The mutation of the retinoblastoma gene has been associated with an increased prevalence of osteosarcoma. The mutation resulting in EWS-FLI1 is associated with Ewing’s sarcoma. The other mutations are associated with tumor formation and proliferation but not necessarily with osteosarcoma formation.
REFERENCES: Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 4.
Scholz R, Kabisch H, Delling G, Winkler K: Homozygous deletion within the retinoblastoma gene in a native osteosarcoma specimen of a patient cured of a retinoblastoma of both eyes. Pediatr Hematol Oncol 1990;72:65.
Hovig E, Lothe R, Farrants G, et al: Chromosome thirteen alterations in osteosarcoma cell lines derived from a patient with previous retinoblastoma. Cancer Genet Cytogenet 1991;57:31-40.

Question 21

A 12-year-old girl has painless bowing of the tibia. Radiographs and a biopsy specimen are shown in Figures 35a through 35c. What is the most likely diagnosis?

Explanation

DISCUSSION: The patient has osteofibrous dysplasia. The radiographic differential diagnosis includes osteofibrous dysplasia, fibrous dysplasia, and adamantinoma. Histology shows a fibro-osseous lesion with prominent osteoblastic rimming but a lack of epithelial nests. Adamantinoma is a low-grade malignancy that typically is located in the anterior tibial cortex and has a soap bubble appearance. Histologically, it is similar to osteofibrous dysplasia but includes epithelial nests of cells. Treatment requires resection. Fibrous dysplasia usually does not require biopsy; however, in this patient the radiographs do not distinguish it from adamantinoma. The radiographic findings are not typical of Ewing’s sarcoma or osteosarcoma. Repeat biopsy should be considered if clinical or radiographic features change.
REFERENCE: Mirra J: Bone Tumors: Clinical, Radiologic, and Pathologic Correlations. Philadelphia, PA, Lea & Febiger, 1989, vol 2, ch 18.

Question 22

A 54-year-old man with metastatic renal cell carcinoma has had increasing pain in the left hip for the past 6 weeks. A radiograph is shown in Figure 36. Prophylactic stabilization will most likely result in

Explanation

DISCUSSION: Prophylactic stabilization of impending fractures does not directly affect the overall survival rate, but it does improve factors related to intraoperative and postoperative complications and decreased recovery time.
REFERENCES: Mirels H: Metastatic disease in long bones: A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop 1989;249:256-264.
Harrington KD: Impending pathologic fractures from metastatic malignancy: Evaluation and management. Instr Course Lect 1986;35:357-381.

Question 23

Which of the following is considered the treatment of choice for a 3-cm chondroblastoma of the distal femoral epiphysis with no intra-articular extension?

Explanation

DISCUSSION: Curettage and bone grafting typically are the preferred treatment of chondroblastoma, yielding acceptable local recurrence rates of less than 10%. Some surgeons advocate adjuvant therapies such as phenol, liquid nitrogen, or argon beam coagulation. Untreated, these lesions can destroy bone and invade the joint to a significant degree. Large intra-articular lesions may require major joint reconstruction. Wide local excision is rarely required to control the tumor. Radiation therapy is indicated only in unresectable lesions.
REFERENCES: Springfield DS, Capanna R, Gherlinzoni F, et al: Chondroblastoma: A review of seventy cases. J Bone Joint Surg Am 1985;67:748.
Simon M, Springfield D, et al: Chrondroblastoma: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, p 190.

Question 24

A radiograph, MRI scans, and a biopsy specimen of a 9-year-old boy with thigh pain are shown in Figures 37a through 37d. Management should consist of

Explanation

DISCUSSION: The patient has Ewing’s sarcoma. Management options for local tumor control include radiation therapy, resection, or a combination; however, in this patient wide resection is preferred over radiation therapy. Radiation therapy is associated with damage to the growth plate, pathologic fracture, radiation-induced sarcomas, and a local recurrence rate of approximately 10% to 12%. Radiation therapy is used for positive margins, unresectable tumors, or for tumors that have a poor response to chemotherapy. Amputation is not necessary since the tumor is resectable. Chemotherapy has improved overall survival rates to over 60% of patients.
REFERENCES: Sailer SL: The role of radiation therapy in localized Ewing’ sarcoma. Semin Radiat Oncol 1997;7:225-235.
Shankar AG, Pinkerton CR, Atra A, Ashley S, Lewis I, Spooner D, et al: Local therapy and other factors influencing site of relapse in patients with localised Ewing’s sarcoma. United Kingdom Children’s Cancer Study Group (UKCCSG). Eur J Cancer 1999;35:1698-1704.
Carrie C, Mascard E, Gomez F, Habrand JL, Alapetite C, Oberlin O, et al: Nonmetastatic pelvic Ewing sarcoma: Report of the French society of pediatric oncology. Med Pediatr Oncol 1999;33:444-449.
Terek RM, Brien EW, Marcove RC, Meyers PA, Lane JM, Healey JH: Treatment of femoral Ewing’s sarcoma. Cancer 1996;78:70-78.

Question 25

A 47-year-old woman has had a 1-month history of left hip and medial thigh pain that is exacerbated by sitting. Laboratory studies show a total protein level of 8.2 g/dL (normal 6.0 to 8.0) and an immunoglobulin G (IGG) level of 2,130 mg/dL (normal 562 to 1,835). A radiograph, CT scan, and biopsy specimen are shown in Figures 38a through 38c. What is the most likely diagnosis?

Explanation

DISCUSSION: The laboratory studies and histology are both consistent with myeloma. Infection should show white blood cells other than plasma cells on histology. Lymphoma would show lymphocytes, not plasma cells. The lack of bone formation on the imaging studies and the lack of osteoid on histology rule out osteosarcoma. The cells have too much cytoplasm and nuclear chromatin to be Ewing’s sarcoma cells.
REFERENCE: Mirra J: Bone Tumors: Clinical, Radiologic, and Pathologic Correlations. Philadelphia, PA, Lea & Febiger, 1989, vol 2, ch 16.

Question 26

A 14-year-old boy has an anteromedial distal thigh mass. A radiograph and MRI scan are shown in Figures 39a and 39b. An open biopsy of the mass should include

Explanation

DISCUSSION: Biopsy of the soft-tissue component is often diagnostic. Alternatively, in centers with pathologists familiar with bone tumors, needle biopsy is usually successful. The principles of biopsy of bone tumors include avoiding contamination of uninvolved structures and compartments, taking the most direct path to the tumors, making an excisable biopsy tract, and obtaining diagnostic tissue. Transverse biopsy incisions should be avoided because they hinder the definitive surgical procedure.
REFERENCES: Peabody TD, Simon MA: Making the diagnosis: Keys to a successful biopsy in children with bone and soft-tissue tumors. Orthop Clin North Am 1996;27:453-459.
Mankin HJ, Mankin CJ, Simon MA: The hazards of the biopsy, revisited. Members of the Musculoskeletal Tumor Society. J Bone Joint Surg Am 1996;78:656-663.
Skrzynski MC, Biermann JS, Montag A, Simon MA: Diagnostic accuracy and charge-savings of outpatient core needle biopsy compared with open biopsy of musculoskeletal tumors. J Bone Joint Surg Am 1996;78:644-649.

Question 27

A 60-year-old man has pain at the tip of the index finger. A radiograph and biopsy specimen are shown in Figures 40a and 40b. Management should consist of

Explanation

DISCUSSION: The radiograph and histology findings are most consistent with squamous cell carcinoma. This tumor is best treated with wide surgical resection margins alone in the absence of metastasis; in this patient, management should consist of amputation through the distal interphalangeal joint. The other treatments are not indicated.
REFERENCE: Soltani K, Krunic A: Non melanoma skin neoplasms, in Vokes E, Golomb H (eds): Oncologic Therapies, ed 2. Berlin, Germany, Springer, pp 646-647.

Question 28

An infant is born with a mass that involves both the volar and dorsal compartments of the left arm. A clinical photograph and biopsy specimen are shown in Figures 41a and 41b. What is the best initial course of action?

Explanation

DISCUSSION: The patient has infantile fibrosarcoma. For unresectable lesions, the treatment of choice is chemotherapy with vincristine, actinomycin-D, and cyclophosphamide, followed by excision if there is an adequate decrease in the size of the lesion.
REFERENCE: Kurkchubasche AG, Halvorson EG, Forman EN, Terek RM, Ferguson WS: The role of preoperative chemotherapy in the treatment of infantile fibrosarcoma. J Pediatr Surgery 2000;35:880-883.

Question 29

Which of the following processes does not account for decreased hematopoiesis in patients with metastatic disease?

Explanation

DISCUSSION: Paucytopenia is a common problem in patients with metastatic disease. Causes include chemotherapy, external beam radiation, marrow replacement by tumor, and anemia of chronic disease. There is no correlation with decreased calcium and a decrease in hematopoiesis. Supportive care with granulocyte-colony stimulating factor (G-CSF) and neupogen can stimulate hematopoiesis.
REFERENCE: Frassica FJ, Gitelis S, Sim FH: Metastic bone disease: General principles, pathophysiology, evaluation, and biopsy. Instr Course Lect 1992;41:293-300.

Question 30

A 43-year-old woman has an enlarging mass in the left groin. A radiograph, CT scan, and a biopsy specimen are shown in Figures 42a through 42c. Treatment should consist of

Explanation

DISCUSSION: The patient has a pelvic chondrosarcoma. The radiograph shows a lytic bone lesion emanating from the left inferior pubic ramus and extending into the soft tissues. Punctate calcifications are revealed on the radiograph and CT scan. The histology is consistent with a malignant cartilage lesion. Appropriate treatment for a pelvic chondrosarcoma is wide resection. In this location, wide resection of the ischiopelvic region (type 3 internal hemipelvectomy) is the treatment of choice. A type 2 internal hemipelvectomy involves resection of the periacetabular region. A type 1 internal hemipelvectomy involves resection of the ilium. No reconstruction is required for a type 3 resection. A classic hemipelvectomy is not necessary because the tumor can be removed with an adequate margin while maintaining the neurovascular structures and hip joint.
REFERENCES: Pring M, Weber KL, Unni K, Sim FH: Chondrosarcoma of the pelvis: A review of sixty-four cases. J Bone Joint Surg Am 2001;83:1630-1642.
Sheth DS, Yasko AW, Johnson ME, Ayala AG, Murray JA, Romsdahl MM: Chondrosarcoma of the pelvis: Prognostic factors for 67 patients treated with definitive surgery. Cancer 1996;78:745-750.
Enneking WF, Dunham WK: Resection and reconstruction for primary neoplasms involving the innominate bone. J Bone Joint Surg Am 1978;60:731-746.

Question 31

A 66-year-old man has a high-grade angiosarcoma of the right tibia. A radiograph is shown in Figure 43. Treatment should consist of

Explanation

DISCUSSION: Angiosarcoma is a locally aggressive sarcoma. The radiograph shows extensive multiple discontinuous lesions throughout the entire tibia. The extent of bone involvement precludes resection; therefore, the treatment of choice is amputation, either above the knee or through the knee. Radiation therapy is not needed after amputation, and chemotherapy remains investigational for soft-tissue sarcoma.
REFERENCE: Simon MA, Springfield DA: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott-Raven, 1998, ch 29.

Question 32

Figures 44a and 44b show the radiographs of a 28-year-old woman who has had progressive hip pain for the past 3 months. What is the most likely diagnosis?

Explanation

DISCUSSION: The patient has multiple hereditary exostoses and a secondary chondrosarcoma arising from a proximal femoral exostosis. The radiograph of the knee shows multiple osteochondromas typical in a patient with multiple hereditary exostoses. Patients with this diagnosis are at an increased risk for malignant degeneration of an osteochondroma. The lateral radiograph of the hip shows a bony lesion emanating from the anterior aspect of the femoral neck that is not well defined in the surrounding soft tissues. There are punctate calcifications and a large soft-tissue mass. The most likely diagnosis is a secondary chondrosarcoma developing from a benign osteochondroma. An enchondroma is an intramedullary benign cartilage lesion. Ollier’s disease and Maffucci’s syndrome involve multiple enchondromas.
REFERENCES: Scarborough M, Moreau G: Benign cartilage tumors. Orthop Clin North Am 1996;27:583-589.
Garrison R, Unni K, McLeod RA, Pritchard DJ, Dahlin DC: Chondrosarcoma arising in osteochondroma. Cancer 1982;49:1890-1897.

Question 33

A 19-year-old girl has had pain and swelling in the right ankle for the past 4 months. She denies any history of trauma. Examination reveals a small soft-tissue mass over the anterior aspect of the ankle and slight pain with range of motion of the ankle joint. The examination is otherwise unremarkable. A radiograph and MRI scan are shown in Figures 45a and 45b, and biopsy specimens are shown in Figures 45c and 45d. What is the most likely diagnosis?

Explanation

DISCUSSION: Giant cell tumors typically occur in a juxta-articular location involving the epiphysis and metaphysis of long bones, usually eccentric in the bone. The radiographs show a destructive process within the distal tibia and an associated soft-tissue mass. The histology shows multinucleated giant cells in a bland matrix with a few scattered mitoses. Osteosarcoma can have a similar destructive appearance but a very different histologic pattern with osteoid production. Ewing’s sarcoma also can have a diffuse destructive process in the bone. The histologic pattern of Ewing’s sarcoma is diffuse round blue cells. Aneurysmal bone cysts typically are seen as a fluid-filled lesion on imaging studies and have only a scant amount of giant cells histologically. Metastatic adenocarcinoma does not demonstrate the pattern shown in the patient’s histology specimen.
REFERENCES: Wold LA, et al: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 198-199.
Simon M, et al: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, pp 200-202.

Question 34

A 13-year-old boy has had a painless mass in the arm for the past 2 months. An MRI scan and biopsy specimens are shown in Figures 46a through 46c. What is the most likely diagnosis?

Explanation

DISCUSSION: Nodular fasciitis is a benign soft-tissue lesion that usually arises from the fascia and is often misdiagnosed as a sarcoma. Desmoid tumors (aggressive fibromatosis) are also benign tumors with a greater tendency for local recurrence. Desmoid tumors have more spindle-shaped fibroblasts in an abundant collagenous matrix. Malignant fibrous histiocytoma is a hypercellular pleomorphic sarcoma more commonly found in adults. The histology is not consistant with a fatty tumor.
REFERENCE: Bernstein KE, Lattes R: Nodular (pseudosarcomatous) fasciitis, a nonrecurrent lesion: Clinicopathologic study of 134 cases. Cancer 1982;49:1668-1678.

Question 35

A 20-year-old man has a symptomatic lesion of fibrous dysplasia in the femoral neck. Management should consist of

Explanation

DISCUSSION: Fibrous dysplasia in the femoral neck frequently warrants treatment because of the risk of pathologic fracture. Cortical strut grafts reduce the risk of local recurrence compared with cancellous bone grafting. Because of the consequences associated with fracture in this location, prophylactic fixation is recommended. Radiation therapy and chemotherapy are not used for this benign condition.
REFERENCES: Simon M, et al: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, pp 197.
Enneking WF, Gearen PF: Fibrous dysplasia of the femoral neck: Treatment by cortical bone grafting. J Bone Joint Surg Am 1986;68:1415.

Question 36

In addition to radiographs of the primary lesion and chest, MRI of the primary lesion, and CT of the chest, staging studies for Ewing’s sarcoma should include which of the following?

Explanation

DISCUSSION: A bone scan and bone marrow biopsy are part of the staging studies for Ewing’s sarcoma. Whole body MRI and PET scans are investigational and show promise of greater sensitivity than a bone scan.
REFERENCES: Schleiermacher G, Peter M, Oberlin O, Philip T, Rubie H, Mechinaud F, et al: Increased risk of systemic relapses associated with bone marrow micrometastasis and circulating tumor cells in localized ewing tumor. J Clin Oncol 2003;21:85-91.
Daldrup-Link HE, Franzius C, Link TM, Laukamp D, Sciuk J, Jurgens H, et al: Whole-body MR imaging for detection of bone metastases in children and young adults: Comparison with skeletal scintigraphy and FDG PET. Am J Roentgenol 2001;177:229-236.

Question 37

Which of the following conditions is transmitted by an autosomal dominant trait?

Explanation

DISCUSSION: Multiple hereditary exostosis is transmitted by an autosomal dominant trait. Li-Fraumeni syndrome and retinoblastoma are autosomal recessive or associated with autosomal recessive mutations. No genetic predisposition to Ollier’s disease or Maffucci’s syndrome has been identified.
REFERENCES: Mirra J (ed): Bone Tumors: Clinical, Radiologic and Pathologic Correlations. Philadelphia, PA, Lea and Febiger, 1989, p 1627.
Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, p 107.

Question 38

A previously healthy 13-year-old girl has had thigh pain for the past 3 weeks. The radiograph shown in Figure 47a reveals a lesion in the right femur. A bone scan and CT scan of the chest show no evidence of other lesions. A biopsy specimen is shown in Figure 47b. What is the most likely diagnosis?

Explanation

DISCUSSION: The patient has Langerhans cell histiocytosis that may be solitary (eosinophilic granuloma) or associated with systemic illness (Hand-Schuller-Christian disease and Letterer-Siwe disease). The solitary form of the disease, eosinophilic granuloma, typically affects patients in the first three decades of life. Radiographically, it is characterized as a well-defined, lytic, “punched out” intramedullary lesion. Histologically, two cell types, eosinophils and Langerhans cells, are seen. The Langerhans cells are seen as mononuclear histiocyte-like cells with oval nuclei with well-defined round or oval cytoplasm. A prominent nuclear groove can be seen in most of the nuclei (coffee bean nuclei). A mixture of inflammatory cells and lipid-laden foam cells with nuclear debris may be present as well. The lack of nuclear atypia and atypical mitoses excludes malignant conditions such as Ewing’s sarcoma, lymphoma of bone, and metastatic neuroblastoma. The lack of acute inflammatory cells excludes the diagnosis of osteomyelitis. The eosinophils have bi-lobed nuclei and granular eosinophilic cytoplasm.
REFERENCES: Dorfman H, Czerniak B: Bone Tumors. St Louis, MO, Mosby, 1988.
Mirra, JM: Bone Tumors: Clinical, Radiologic, and Pathologic Correlations. Philadelphia, PA, Lea & Febiger, 1989.

Question 39

A 50-year-old man with metastatic renal cell carcinoma has right hip pain. A radiograph and CT scan are shown in Figures 48a and 48b. The first step in management should consist of

Explanation

DISCUSSION: These lesions are extremely vascular and can cause uncontrolled intraoperative bleeding; therefore embolization is the appropriate first treatment. Because the radiograph and CT scan show a lytic lesion in the supra-acetabular region that affects the weight-bearing dome and medial wall, the next step in treatment would most likely be a total hip arthroplasty and acetabular reconstruction. Treatment with bisphosphonates and radiation therapy will not prevent an acetabular fracture. Cementoplasty is an emerging technique in which cement is injected percutaneously into a lesion, but no long-term results have been reported. Radiofrequency ablation of bone metastases is also an emerging technique that provides palliative pain control.
REFERENCES: Layalle I, Flandroy P, Trotteur G, Dondelinger RF: Arterial embolization of bone metastases: Is it worthwhile? J Belge Radiol 1998;81:223-225.
Chatziioannou AN, Johnson ME, Pneumaticos SG, Lawrence DD, Carrasco CH: Preoperative embolization of bone metastases from renal cell carcinoma. Eur Radiol 2000;10:593-596.

Question 40

What is the most common benign bone tumor in childhood?

Explanation

DISCUSSION: The most common benign bone tumor in childhood is a nonossifying fibroma. It is estimated that 30% of children have a nonossifying fibroma. In most patients, the lesion is not identified until a radiograph is obtained for unrelated reasons. Similarly, most identified cases of fibrous cortical defect are not biopsied because the radiographic and clinical presentations are diagnostic.
REFERENCES: Aboulafia AJ, Kennon RE, Jelinek JS: Benign bone tumors of childhood. J Am Acad Orthop Surg 1999;7:377-388.
Biermann JS: Common benign lesions of bone in children and adolescents. J Pediatr Orthop 2002;22:268-273.

Question 41

A 13-year-old patient has foot drop and lateral knee pain. AP and lateral radiographs and an MRI scan are shown in Figures 49a through 49c. A biopsy specimen is shown in Figure 49d. What is the preferred method of treatment?

Explanation

DISCUSSION: The “sunburst” radiographic appearance suggests an osteosarcoma, and the histologic findings confirm the diagnosis with malignant cells surrounded by pink osteoid. MRI scans are not particularly helpful in the diagnosis of osteosarcoma but are mandatory for surgical planning. Osteosarcomas are high-grade sarcomas that are best treated with chemotherapy and wide resection. Even though the peroneal nerve is involved, limb salvage is indicated. Survival after limb salvage is equivalent to amputation, with better function.
REFERENCES: Goorin AM, Abelson HT, Frei E: Osteosarcoma: Fifteen years later. N Engl J Med 1985;313:1637.
Link MP, Goorin AM, Miser AW, et al: The effect of adjuvant chemotherapy on relapse-free survival in patients with osteosarcoma of the extremity. N Engl J Med 1986;314:1600.
Davis AM, Bell RS, Goodwin PJ: Prognostic factors in osteosarcoma: A critical review. J Clin Oncol 1994;12:423.

Question 42

A 13-year-old girl is diagnosed with a stage IIB osteosarcoma of the proximal tibia. Following neoadjuvant chemotherapy, local control should consist of

Explanation

DISCUSSION: Local control of osteosarcoma consists of wide resection and reconstruction. Radiation therapy is not recommended except in unresectable lesions or for palliation. Curettage and bone grafting result in intralesional resection with an unacceptable high rate of local recurrence. Chemotherapy alone is not adequate for local control.
REFERENCES: Simon M, Springfield D, et al: Osteogenic Sarcoma: Surgery for Bone and Soft Tissue. Philadelphia, PA, Lippincott Raven, 1998, p 274.
Wold LA, et al: Osteogenic Sarcoma: Atlas of Orthopaedic Pathology. Philadelphia, PA, WB Saunders, 1990, pp 14-15.

Question 43

A 23-year-old woman has had vague left knee pain for the past 6 months. A radiograph and CT scan are shown in Figures 50a and 50b. What is the most likely diagnosis?

Explanation

DISCUSSION: The radiographic appearance of the lesion emanating from the posterior cortex of the left distal femur is consistent with a surface bone-producing lesion; therefore, the most likely diagnosis is a parosteal osteosarcoma. In an osteochondroma, the cortex and medullary cavity of the lesion are in continuity with that of the native bone. A dedifferentiated chondrosarcoma has histologic components of a high-grade sarcoma plus a benign or low-grade malignant cartilage tumor. Tumoral calcinosis is characterized by amorphous calcium in the soft tissues and does not emanate from the bone itself. While often confused with parosteal osteosarcoma, myositis ossificans is usually more mature at the periphery of the lesion rather than the center. In addition, myositis ossificans does not involve the underlying cortex but remains separate from the bone.
REFERENCES: Unni KK: Dahlin’s Bone Tumors: General Aspects and Data on 11,087 Cases, ed 5. Philadelphia, PA, Lippincott-Raven, 1996, pp 185-196.
Okada K, Frassica FJ, Sim FH, Beabout JW, Bond JR, Unni KK: Parosteal osteosarcoma. A clinicopathological study. J Bone Joint Surg Am 1994;76:366-378.

Question 44

What is the preferred treatment of a patient with breast cancer and a pathologic fracture of the clavicle in her dominant arm?

Explanation

DISCUSSION: Closed management should be attempted for upper extremity pathologic fractures, particularly the clavicle. If nonunion or pain persists, surgery may be indicated. Radiofrequency ablation is not indicated for subcutaneous bones. Early motion is likely to cause increased pain and disability.
REFERENCES: Weber KC, Lewis VO, Randall RL, Lee AK, Springfield D: An approach to the management of the patient with metastatic bone disease. Instr Course Lect 2004;53:663-676.
Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons 2002, p 331.

Question 45

A 14-year-old boy has an asymptomatic mass on the right arm. MRI scans and biopsy specimens are shown in Figures 51a through 51d. Immunostaining is positive for desmin. Additional staging studies should include

Explanation

DISCUSSION: The patient has rhabdomyosarcoma. Axilliary node and bone marrow biopsy are part of the staging because about 12% of patients with rhabdomyosarcoma of the extremity have evidence of lymph nodes metastases at presentation. Bone marrow metastases have been shown to portend a worse prognosis.
REFERENCES: Lawrence W, Jr., Hays DM, Heyn R, Tefft M, Crist W, Beltangady M, et al: Lymphatic metastases with childhood rhabdomyosarcoma: A report from the Intergroup Rhabdomyosarcoma Study. Cancer 1987;60:910-915.
Schleiermacher G, Peter M, Oberlin O, et al: Increased risk of systemic relapses associated with bone marrow micrometastasis and circulating tumor cells in localized ewing tumor. J Clin Oncol 2003;21:85-91.

Question 46

A 15-year-old girl has left knee pain and an enlarging mass in the distal thigh. AP and lateral radiographs are shown in Figures 52a and 52b, and a biopsy specimen is shown in Figure 52c. What is the most likely diagnosis?

Explanation

DISCUSSION: A bone-producing lesion in the metaphysis of an adolescent is most likely an osteosarcoma. The radiographs show a distal femoral bone-producing lesion extending into the surrounding soft tissues. The histologic appearance consists of pleomorphic cells producing osteoid. Ewing’s sarcoma and metastatic neuroblastoma do not produce a matrix. Chondrosarcoma is a radiographically destructive lesion with calcification and cartilage cells on histologic section. An osteochondroma is a benign cartilage lesion that is continuous with the medullary cavity of the underlying bone and extends into a bony lesion and covered by a cartilage cap.
REFERENCES: Unni KK: Dahlin’s Bone Tumors: General Aspects and Data on 11,087 Cases, ed 5. Philadelphia, PA, Lippincott-Raven, 1996, pp 143-160.
Gibbs CP, Weber K, Scarborough MT: Malignant bone tumors. Instr Course Lect 2002;51:413-428.

Question 47

Survival rates for children with soft-tissue sarcoma other than rhabdomyosarcoma are best correlated with

Explanation

DISCUSSION: In review of 154 patients with nonrhabdomyosarcoma, Rao reported that histologic grade, tumor invasiveness, and adequate surgical margin were the most important prognostic factors. Histologic subtype, use of adjuvant chemotherapy, and patient age were not as important. Size related to degree of invasiveness was not statistically significant.
REFERENCES: Rao BN: Nonrhabdomyosarcoma in children: Prognostic factors influencing survival. Semin Surg Oncol 1993;9:524-531.
Andrassy R, et al: Non-rhabdomyosarcoma Soft-Tissue Sarcomas: Pediatric Surgical Oncology. Philadelphia, PA, WB Saunders, p 221.

Question 48

A 25-year-old woman has had pain and stiffness in her knee following a motor vehicle accident 9 months ago. The radiograph, CT scan, MRI scan, and biopsy specimen are shown in Figures 53a through 53d. What is the most likely diagnosis?

Explanation

DISCUSSION: Heterotopic ossification may occur spontaneously or following trauma. The imaging studies and histology reveal mature fatty bone marrow and trabecular bone. Osteochondromas are cortically based with the medullary canal extending into the lesion. This is not evident in this patient. Also, no obvious cartilage cap is present. Parosteal osteosarcoma commonly occurs in the posterior distal femoral cortex but is ruled out by the lack of the typical fibrous stromal cells forming the low-grade malignant osteoid. The histology and clinical presentation eliminate osteomyelitis and osteoblastoma.
REFERENCES: Horne LT, Blue BA: Intra-articular heterotopic ossification in the knee following intramedullary nailing of the fractured femur using a retrograde method. J Orthop Trauma 1999;13:385-388.
Stannard JP, Wilson TC, Sheils TM, McGwin G Jr, Volgas DA, Alonso JE: Heterotopic ossification associated with knee dislocation. Arthroscopy 2002;18:835-839.
Mills WJ, Tejwani N: Heterotopic ossification after knee dislocation: The predictive value of the injury severity score. J Orthop Trauma 2003;17:338-345.

Question 49

Which of the following lesions most closely resembles Ewing’s sarcoma histologically?

Explanation

DISCUSSION: Ewing’s sarcoma is characterized by small round blue cells. Lesions with a similar appearance include lymphoma, primitive neuroectodermal tumor, rhabdomyosarcoma, small cell lung tumor, and metastatic neuroblastoma. Karyotyping, immunohistochemistry, and electron microscopy can help differentiate these lesions.
REFERENCE: Wold LE, McLeod RA, Sim FH, Unni KK: Atlas of Orthop Pathology. Philadelphia, PA, WB Saunders, 1990.

Question 50

Primary chondrosarcoma of bone most commonly occurs in which of the following locations?

Explanation

DISCUSSION: The most common location of chondrosarcoma is the pelvis (30%), followed by the proximal femur (20%) and shoulder girdle (15%). Chondrosarcoma rarely affects the spine or hand.
REFERENCES: Lee FY, Mankin HJ, Fondren G, et al: Chondrosarcoma of bone: An assessment of outcome. J Bone Joint Surg Am 1999;81:326-338.
Simon M, Springfield D, et al: Chondrosarcoma: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, p 276.

Question 51

A 10-year-old child who survived bilateral retinoblastoma in infancy presents with a new onset of pain and swelling in the distal femur. Radiographs reveal a mixed lytic and sclerotic lesion with a Sunburst periosteal reaction. Given the patient's genetic history, what is the most likely diagnosis of this secondary malignancy?

Explanation

Patients with hereditary retinoblastoma possess a germline mutation in the RB1 tumor suppressor gene. This mutation places them at a significantly increased risk for secondary malignancies, most commonly osteosarcoma.

Question 52

A 35-year-old man sustains an APC-III pelvic ring injury. During the ilioinguinal approach for internal fixation, massive hemorrhage occurs near the superior pubic ramus. This bleeding is most likely originating from the 'corona mortis', which represents an anastomosis between which two vascular systems?

Explanation

The corona mortis is a vascular anastomosis between the external iliac system (typically via the inferior epigastric artery) and the internal iliac system (via the obturator artery). It is highly vulnerable to injury during approaches to the superior pubic ramus and acetabulum.

Question 53

A 25-year-old man dives into a shallow pool and sustains a C1 burst fracture (Jefferson fracture). An open-mouth odontoid radiograph demonstrates that the combined lateral overhang of the C1 lateral masses on C2 is 8 mm. What does this finding indicate and what is the recommended management?

Explanation

According to the Spence rule, a combined lateral overhang of the C1 lateral masses on C2 greater than 6.9 mm indicates a rupture of the transverse ligament. This renders the injury highly unstable, necessitating rigid immobilization with a halo vest or surgical C1-C2 fusion.

Question 54

A 55-year-old man presents with an incidental finding of a proximal humeral lesion. Radiographs show 'pop-corn' calcifications and endosteal scalloping involving greater than two-thirds of the cortical thickness. Biopsy confirms a Grade II chondrosarcoma. What is the most appropriate definitive management?

Explanation

Grade II and III chondrosarcomas exhibit aggressive local behavior and metastatic potential, requiring wide surgical resection. Unlike osteosarcoma or Ewing sarcoma, chondrosarcomas are generally resistant to chemotherapy and radiation.

Question 55

A 28-year-old high-speed trauma patient presents with a vertically oriented Pauwels type III femoral neck fracture. To provide the best biomechanical stability against vertical shear forces, which fixation construct is most appropriate?

Explanation

Pauwels type III femoral neck fractures are highly vertical and experience massive shear forces, leading to high rates of nonunion and varus collapse. A fixed-angle device like a sliding hip screw with a derotational screw provides superior biomechanical resistance to these shear forces compared to multiple cancellous screws.

Question 56

The Spinal Instability Neoplastic Score (SINS) is utilized to assess the need for surgical stabilization in patients with spinal metastasis. Which of the following is an explicit component of the SINS criteria?

Explanation

The SINS criteria assess spinal instability based on six components: location, pain, bone lesion type (lytic/blastic), radiographic alignment, vertebral body collapse, and posterolateral involvement. Tumor histology and systemic status dictate overall survival but are not part of the mechanical SINS score.

Question 57

A 14-year-old boy presents with a diaphyseal femur lesion showing an 'onion-skin' periosteal reaction. Cytogenetic testing reveals a t(11;22) chromosomal translocation. What is the resulting fusion gene critical for the pathogenesis of this tumor?

Explanation

The clinical picture describes Ewing sarcoma, which is classically associated with the t(11;22)(q24;q12) translocation. This chromosomal abnormality results in the EWS-FLI1 fusion gene, acting as an aberrant transcription factor.

Question 58

A 45-year-old heavy smoker underwent intramedullary nailing for a tibial shaft fracture 8 months ago. Radiographs now show an 'elephant foot' hypertrophic nonunion. What is the primary underlying cause of this specific type of nonunion?

Explanation

Hypertrophic nonunions (characterized by abundant callus formation or an 'elephant foot' appearance) possess adequate biological healing capacity and blood supply but lack sufficient mechanical stability. Treatment typically involves augmenting mechanical stability, such as exchanging the nail for a larger diameter.

Question 59

A 12-year-old female gymnast complains of persistent lower back pain. Imaging demonstrates an L5-S1 isthmic spondylolisthesis with 35% slippage (Grade II). She has failed 6 months of physical therapy and bracing. What is the most appropriate surgical intervention?

Explanation

For pediatric patients with symptomatic low-grade (<50%) isthmic spondylolisthesis failing conservative management, an in situ L5-S1 posterolateral fusion is the gold standard. Decompression without fusion is contraindicated in children due to the high risk of further slippage.

Question 60

A 30-year-old woman presents with a lytic epiphyseal lesion of the distal femur. Biopsy reveals multinucleated giant cells in a background of mononuclear stromal cells. In the pathogenesis of this tumor, the true neoplastic cells express high levels of which of the following?

Explanation

In a Giant Cell Tumor of bone, the mononuclear stromal cells are the actual neoplastic elements. They overexpress RANKL, which recruits and activates the abundant, reactive osteoclast-like multinucleated giant cells that cause the characteristic bone destruction.

Question 61

A 32-year-old man falls from a height and sustains a Hawkins Type III talar neck fracture. What joint disruptions characterize this injury, and what is the approximate risk of developing avascular necrosis (AVN) of the talar body?

Explanation

A Hawkins Type III fracture involves a fracture of the talar neck with dislocation of both the subtalar and tibiotalar joints. Because of the severe disruption of the retrograde blood supply to the talar body, the risk of AVN is exceedingly high, approaching 80-100%.

Question 62

A 40-year-old man presents to the emergency department with acute urinary retention, saddle anesthesia, and progressive bilateral leg weakness due to a massive L4-L5 disc herniation. To optimize the chance of neurologic recovery, surgical decompression must ideally occur within what timeframe?

Explanation

This patient has acute cauda equina syndrome, an absolute surgical emergency. Literature demonstrates that surgical decompression performed within 48 hours of symptom onset yields the best outcomes for bladder and motor function recovery.

Question 63

A 20-year-old man presents with a 'shepherd's crook' deformity of his proximal femur. Radiographs display a ground-glass appearance. This skeletal pathology is associated with a somatic activating mutation in the GNAS1 gene. If accompanied by cafe-au-lait spots, what endocrine disorder is most classically associated?

Explanation

The patient has fibrous dysplasia. When polyostotic fibrous dysplasia occurs with cafe-au-lait spots and endocrine hyperfunction, it is known as McCune-Albright syndrome. The most common endocrine abnormality in this syndrome is precocious puberty.

Question 64

A 25-year-old man sustains a Galeazzi fracture. Radiographs show a fracture of the distal third of the radial shaft with dislocation of the distal radioulnar joint (DRUJ). Which structure is the primary stabilizer of the DRUJ that is disrupted in this injury pattern?

Explanation

The triangular fibrocartilage complex (TFCC) is the primary stabilizing structure of the DRUJ. In a Galeazzi fracture-dislocation, the DRUJ is disrupted, implying a significant tear or avulsion of the TFCC that must be addressed if the joint remains unstable after radius fixation.

Question 65

A 65-year-old man presents with dysphagia and severe cervical stiffness. Radiographs demonstrate flowing ossification along the anterolateral aspect of four contiguous cervical vertebral bodies with preserved disc spaces and normal sacroiliac joints. What is the most likely diagnosis?

Explanation

DISH is characterized by flowing anterolateral ossification across at least four contiguous vertebrae, preservation of disc height, and absence of sacroiliac joint fusion. The bulky anterior cervical osteophytes can compress the esophagus, leading to dysphagia.

Question 66

A 15-year-old girl with distal femur osteosarcoma undergoes neoadjuvant chemotherapy followed by wide resection. Which of the following histologic findings from the resected specimen most accurately predicts her long-term survival?

Explanation

The histologic percentage of tumor necrosis following neoadjuvant chemotherapy is the most significant prognostic factor for survival in osteosarcoma. Greater than 90% necrosis is considered a good response and correlates with improved long-term survival.

Question 67

A 60-year-old man presents with a destructive lesion in the proximal humerus. Biopsy confirms metastatic clear cell renal carcinoma. Prophylactic internal fixation is planned. What is the most appropriate step immediately prior to surgery?

Explanation

Metastatic renal cell carcinoma and thyroid carcinoma are notoriously hypervascular tumors. Pre-operative angiographic embolization within 24-48 hours of surgery is highly recommended to minimize catastrophic intraoperative blood loss.

Question 68

A 25-year-old female presents with a large sacral mass. Biopsy confirms Giant Cell Tumor of bone. Because wide surgical resection would result in severe neurological morbidity, medical therapy is indicated. Which of the following is the most appropriate primary medical treatment?

Explanation

Denosumab is a monoclonal antibody against RANKL. It is highly effective in treating Giant Cell Tumor of bone by inhibiting the osteoclast-like giant cells, leading to tumor consolidation and calcification, which can facilitate surgery or serve as definitive therapy for unresectable lesions.

Question 69

A 10-year-old boy is diagnosed with Ewing sarcoma of the femoral diaphysis. Which chromosomal translocation is classically pathognomonic for this tumor?

Explanation

Ewing sarcoma is classically associated with the t(11;22)(q24;q12) translocation. This results in the EWS-FLI1 fusion protein, which acts as an oncogenic transcription factor.

Question 70

A 45-year-old man has a progressively enlarging, painful mass in his right ilium. Biopsy reveals atypical chondrocytes in a myxoid stroma with a characteristic popcorn-like calcification pattern. What is the primary treatment modality for this disease?

Explanation

This patient has a chondrosarcoma. Chondrosarcomas are generally resistant to both chemotherapy and radiation therapy; therefore, wide surgical excision is the primary and most effective treatment for intermediate to high-grade lesions.

Question 71

A 70-year-old man with advanced Ankylosing Spondylitis suffers a low-energy ground-level fall. He complains of severe neck pain but is neurologically intact. Standard lateral cervical radiographs are obscured by his shoulder anatomy. What is the mandatory next step in his workup?

Explanation

Patients with Ankylosing Spondylitis have a rigid, osteopenic spine that acts like a long bone, making it highly susceptible to unstable hyperextension fractures even from minor trauma. A CT or MRI of the entire spine is mandatory due to the high risk of occult, highly unstable fractures and epidural hematomas.

Question 72

A 35-year-old construction worker falls from a height and sustains an L1 burst fracture. In the Thoracolumbar Injury Classification and Severity (TLICS) score, which of the following parameters is assigned the highest individual point value?

Explanation

In the TLICS scoring system, a disrupted Posterior Ligamentous Complex (PLC) is assigned 3 points. This is the highest individual score for structural integrity, pushing the total score toward a surgical indication (total score > 4).

Question 73

An 80-year-old man sustains a Type II odontoid fracture with 6 mm of anterior displacement. He has severe medical comorbidities preventing surgery. He is treated non-operatively. Which of the following is the most significant risk factor for non-union in this patient?

Explanation

Risk factors for non-union of Type II odontoid fractures include age > 50 years, initial displacement > 5 mm, and posterior displacement. Age > 50 is consistently identified in the literature as the single most significant predictor of non-union.

Question 74

A 14-year-old gymnast presents with persistent low back pain. Radiographs reveal a Grade II isthmic spondylolisthesis at L5-S1. She has failed 6 months of conservative management including bracing and physical therapy. What is the recommended surgical intervention?

Explanation

For symptomatic Grade I or II isthmic spondylolisthesis that fails conservative treatment in adolescents, an in situ posterolateral fusion of L5-S1 is the gold standard. It offers excellent clinical outcomes without the high neurological risk associated with reduction.

Question 75

A 65-year-old female presents with severe myelopathy symptoms. MRI reveals Ossification of the Posterior Longitudinal Ligament (OPLL) from C3-C6 with K-line negative (kyphotic) alignment. What is the preferred surgical approach?

Explanation

In OPLL with a negative K-line (cervical kyphosis), posterior decompression alone (laminoplasty) will not allow the spinal cord to drift backward away from the OPLL mass. A combined anterior-posterior approach or anterior corpectomy is preferred to decompress the cord and restore lordosis.

Question 76

A 25-year-old male sustains a vertical shear pelvic ring injury. He is hypotensive in the ED. A pelvic binder is applied, but his blood pressure remains 70/40 mmHg despite 2 units of PRBCs. The FAST exam is negative. What is the most appropriate next step in management?

Explanation

In a hemodynamically unstable patient with a pelvic ring injury and a negative FAST (ruling out intra-abdominal hemorrhage), preperitoneal pelvic packing or emergent angiography is indicated. Packing is rapid, can be done immediately in the OR, and controls the venous bleeding that is the most common source of hemorrhage.

Question 77

A 30-year-old man sustains a high-energy Pauwels Type III femoral neck fracture. What is the optimal surgical construct to minimize the risk of varus collapse and non-union in this specific fracture pattern?

Explanation

Pauwels Type III fractures (>50 degrees vertical angle) are highly unstable due to significant shear forces. A fixed-angle device, such as a sliding hip screw (often supplemented with a derotation screw) or a cephalomedullary nail, provides superior biomechanical stability compared to multiple cannulated screws.

Question 78

Six weeks after ORIF of a Hawkins Type III talar neck fracture, an AP radiograph of the ankle shows a subchondral radiolucent band in the dome of the talus. What does this radiographic finding indicate?

Explanation

This finding is known as the Hawkins sign. The subchondral radiolucent band represents subchondral atrophy from disuse, which can only occur if there is an intact blood supply to the bone. It strongly suggests that avascular necrosis will not occur.

Question 79

During a minimally invasive percutaneous plate osteosynthesis (MIPPO) of a distal tibia fracture via an anteromedial approach, which neurovascular structure is at highest risk of iatrogenic injury at the distal insertion site?

Explanation

The great saphenous vein and saphenous nerve course superficially along the anteromedial aspect of the distal tibia. They are at significant risk of iatrogenic injury during the insertion and distal screw fixation of medial tibial plates.

Question 80

A 22-year-old male sustains a mid-shaft clavicle fracture with 2.5 cm of shortening and significant displacement. He is highly active. What is the primary indication for open reduction and internal fixation in this specific patient scenario?

Explanation

Significant shortening (> 2 cm) or severe displacement of mid-shaft clavicle fractures in active adults is associated with a higher rate of symptomatic non-union, loss of shoulder strength, and altered shoulder biomechanics. ORIF significantly decreases the non-union rate and improves functional return.

Question 81

A 14-year-old boy presents with a distal femur osteosarcoma and undergoes neoadjuvant chemotherapy prior to surgical resection. What histologic finding on the final resection specimen is the most important prognostic factor for overall survival?

Explanation

The degree of tumor necrosis following neoadjuvant chemotherapy is the most significant prognostic indicator for overall survival in osteosarcoma. Greater than 90% necrosis indicates a good response to chemotherapy and correlates with improved long-term survival.

Question 82

A 65-year-old man with metastatic renal cell carcinoma presents with mechanical back pain and an isolated L3 vertebral body lesion without neurologic deficit. The Spinal Instability Neoplastic Score (SINS) is 14. What is the most appropriate management?

Explanation

A SINS score of 13 or greater indicates spinal instability, warranting surgical stabilization regardless of neurologic status. Because renal cell carcinoma metastases are highly vascular, preoperative embolization is strongly recommended to minimize intraoperative hemorrhage.

Question 83

A 72-year-old woman on long-term alendronate therapy sustains an atypical subtrochanteric femur fracture. Prophylactic fixation of the contralateral femur is being considered. Which of the following radiographic findings in the contralateral femur is the strongest indication for prophylactic surgical fixation?

Explanation

A radiolucent line (dreaded black line) in the thickened lateral cortex of a bowed femur signifies an impending atypical femur fracture in a patient on bisphosphonates. This finding is a strong indication for prophylactic intramedullary nailing to prevent catastrophic completion of the fracture.

Question 84

A 30-year-old pregnant woman presents with an aggressively expanding, painful lytic lesion in the distal radius. Biopsy confirms Giant Cell Tumor (GCT) of bone. What is the primary mechanism of action of Denosumab, and why is it contraindicated in this patient?

Explanation

Denosumab is a monoclonal antibody against RANKL, which disrupts osteoclast function and is highly effective for GCT of bone. It is contraindicated in pregnancy because RANKL inhibition can cross the placenta and cause severe fetal skeletal malformations and impaired tooth eruption.

Question 85

A 55-year-old man undergoes a multilevel anterior cervical discectomy and fusion (ACDF) for severe cervical stenosis and myelopathy. Postoperatively, he wakes up with a prominent C5 motor palsy, unable to abduct his shoulder. What is the most likely etiology of this complication?

Explanation

Postoperative C5 palsy is a well-described complication following extensive cervical spinal decompression. It is most commonly attributed to the posterior drift of the spinal cord following decompression, leading to traction and tethering of the relatively short, horizontally oriented C5 nerve roots.

Question 86

A 35-year-old man is brought to the trauma bay after a motorcycle accident. He remains hemodynamically unstable despite aggressive initial fluid resuscitation. Radiographs show a 4 cm pubic symphysis diastasis with intact posterior sacroiliac ligaments. A pelvic binder is applied but he remains hypotensive. What is the next most appropriate step in management?

Explanation

The patient has an APC-II pelvic ring injury and is in hemorrhagic shock. Following mechanical stabilization with a pelvic binder, persistent hemodynamic instability dictates immediate intervention for hemorrhage control via preperitoneal pelvic packing or angiography with embolization.

Question 87

A 60-year-old man presents with progressive bowel and bladder dysfunction. MRI reveals a large, destructively expansile, T2-hyperintense midline mass in the sacrum. Histology shows physaliferous cells with bubbly cytoplasm. What is the most appropriate surgical management for this lesion?

Explanation

The clinical and histologic findings (physaliferous cells) are pathognomonic for a sacral chordoma. Chordomas are locally aggressive and highly radio- and chemo-resistant, making wide en bloc surgical resection with negative margins the gold standard for treatment to minimize recurrence.

Question 88

A 42-year-old woman presents with acute-onset bilateral sciatica, saddle anesthesia, and urinary retention with overflow incontinence. MRI shows a massive central disc herniation at L4-L5. Which of the following urodynamic findings is most characteristic of her bladder dysfunction?

Explanation

Cauda equina syndrome causes a lower motor neuron lesion affecting the sacral parasympathetic nerve roots (S2-S4). This results in an areflexic (flaccid) bladder with decreased detrusor tone and absent voluntary sphincter control, leading to urinary retention and overflow incontinence.

Question 89

A 45-year-old man sustains a closed, displaced, intra-articular calcaneus fracture after a fall. Surgery via an extensile lateral approach is planned. Which of the following patient factors is the strongest predictor of postoperative wound complications?

Explanation

Cigarette smoking is the single most significant modifiable risk factor for wound complications following the extensile lateral approach for calcaneus fractures. Smokers have a substantially increased risk of edge necrosis, deep infection, and the subsequent need for soft tissue coverage.

Question 90

A 10-year-old girl presents with pain and swelling in her mid-diaphyseal femur. Radiographs demonstrate a permeative destructive lesion with an "onion-skin" periosteal reaction. Biopsy confirms Ewing sarcoma. Which of the following genetic translocations is most commonly associated with this tumor?

Explanation

Ewing sarcoma is classically driven by a fusion of the EWSR1 gene on chromosome 22 with the FLI1 gene on chromosome 11. This t(11;22)(q24;q12) translocation is found in approximately 85% of cases.

Orthopedic Surgery Board Review MCQs: Arthroplasty, Trauma & Spine Part 255

Orthopedic Board Review MCQs: Fracture, Spine & Tumor | Part 32

Key Takeaway

Orthopedic Board Review MCQs: Fracture, Spine & Tumor | Part 32

Chapter Index