Orthopedic Board Review: 100 High-Yield MCQs - Set 501

The radiographs show increased density and reactive bone formation. A faint nidus can be seen on the radiograph but is obvious on the CT scan. The initial therapy for an osteoid osteoma should be oral anti-inflammatory drugs. A biopsy or SPECT bone scan is not indicated because the osteoid osteoma is clearly seen on the CT scan. If the patient fails to respond to nonsurgical therapy, CT-guided radiofrequency ablation or surgical excision is indicated depending on the anatomic location. Frassica FJ, Waltrip RL, Sponseller PD, Ma LD, McCarthy EF Jr: Clinicopathologic features and treatment of osteoid osteoma and osteoblastoma in children and adolescents. Orthop Clin North Am 1996;27:559-574. Kneisl JS, Simon MA: Medical management compared with operative treatment for osteoid osteoma. J Bone Joint Surg Am 1992;74:179-185.

The indications for high tibial valgus osteotomy include a physiologically young age, arthritis confined to the medial compartment, 10 to 15 degrees of varus alignment on weight-bearing radiographs, a preoperative arc of motion of at least 90 degrees, flexion contracture of less than 15 degrees, and a motivated, compliant patient. Contraindications include lateral compartment narrowing of the articular cartilage, lateral tibial subluxation of greater than 1 cm, medial compartment bone loss, ligamentous instability, and inflammatory arthritis. Naudie D, Bourne RB, Rorabeck CH, Bourne TT: The Insall Award: Survivorship of the high tibial valgus osteotomy. A 10- to 22-year followup study. Clin Orthop 1999;367:18-27.

Posttraumatic osteolysis of the distal portion of the clavicle is a condition that can be a complication of acute or repetitive trauma. The distal end of the clavicle is frayed and resorbed. Resorption may occur after weeks or months. The end of the clavicle may reconstitute over a period of months, or the acromioclavicular joint may remain widened. The differential diagnosis for distal clavicular erosion also includes rheumatoid arthritis, hyperparathyroidism, neoplastic destruction, cleidocranial dysplasia, and pyknodysostosis. Acutely, a type 2 acromioclavicular joint injury does not result in erosion or resorption of the clavicle. Periosteal sleeve injuries radiographically mimic acromioclavicular joint dislocation. Rickets occurs only in childhood.

28b 28c 28d Osteochondral fractures involving the talar dome have been classified based on radiographic and MRI findings. A nondisplaced and incomplete fracture may be treated effectively with a short leg cast and no weight bearing for 6 weeks. This patient has a complete, separated, and displaced osteochondral fragment involving the midlateral talar dome that will most likely cause pain, mechanical symptoms, and effusion if treated nonsurgically. In addition, there is very little bone remaining on the fragment, making the likelihood of healing with open reduction and internal fixation problematic. The treatment of choice includes arthroscopy, removal of the loose fragment, curettage or drilling of the base, and a rehabilitation program that emphasizes peroneal strengthening, range of motion, and proprioceptive training. Lutter LD, Mizel MS, Pfeffer GB (eds): Orthopaedic Knowledge Update: Foot and Ankle. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 205-226.

39b 39c 39d 39e The lesion is a chondroblastoma. The plain radiographs show a well-defined radiolucent lesion in the distal femoral epiphysis of a skeletally immature patient. The margins are well defined, suggesting a benign growth. The epiphysis is an unusual location for bone tumors, except for chondroblastomas. Of all chondroblastomas, 95% are located within the epiphysis. The MRI scans show a punctate appearance that is commonly seen in cartilage lesions. The biopsy specimen shows a chondroid lesion with polygonal chondrocytes. These findings are consistent with a chondroblastoma. The natural history of chondroblastomas is for continued growth and bone destruction if left untreated. Treatment should consist of curettage, with or without the use of physical or chemical adjuvants, and bone grafting.

A semiconstrained prosthesis can provide excellent results in carefully selected patients. Because the radiographs show extensive joint destruction with loss of the capitellum and trochlea, a capitellocondylar total elbow (unconstrained) prosthesis is contraindicated. Elbow fusion is poorly accepted, and the radiographs show too much articular destruction for a radial head excision, synovectomy, or interposition arthroplasty to be effective. Ewald FC, Simmons ED Jr, Sullivan JA, et al: Capitellocondylar total elbow replacement in rheumatoid arthritis: Long-term results. J Bone Joint Surg Am 1993;75:498-507.

The radiograph shows a diastasis of the scapholunate interval, caused by certain failure of the scapholunate interosseous ligament. The lunotriquetral interosseous ligament stabilizes the lunotriquetral joint. The long radiolunate ligament originates in the volar radius and inserts in the lunate. The short radiolunate ligament originates on the ulnar margin of the radius and inserts on the ulnar margin of the lunate. The ulnolunate ligament originates at the ulnar styloid base and inserts on the volar aspect of the lunate. Linscheid RL, Dobyns JH, Beabout JW, et al: Traumatic instability of the wrist: Diagnosis, classification, and pathomechanics. J Bone Joint Surg Am 1972;54:1612-1632. Mayfield JK, Johnson RP, Kilcoyne RK: Carpal dislocations: Pathomechanics and progressive perilunar instability. J Hand Surg Am 1980;5:226-241.

A true compression fracture is a single-column injury that does not create canal compromise. A burst fracture is a two- or three-column injury that disrupts the middle column and thereby narrows the spinal canal. This patient has a burst fracture. The mechanism of injury is usually vertical compression or flexion compression. Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 197-217.

The radiograph reveals that an insufficient amount of the proximal humerus was excised in the index procedure, resulting in malalignment of the humeral component, overstuffing of the glenohumeral joint, and glenoid arthritis. It is unlikely that physical therapy or soft-tissue releases alone will be adequate. Revision of the humeral component, recutting of the proximal humerus to allow a more anatomic alignment of the humeral component, appropriate soft-tissue releases, and glenoid arthroplasty will offer the best chance of improvement in this difficult situation. Neer CS II, Kirby RM: Revision of humeral head and total shoulder arthroplasties. Clin Orthop 1982;170:189-195.

A discoid meniscus is a large disk-like meniscus. It is seen in the lateral meniscus in 3% of the population; a discoid medial meniscus is much less common. It can be identified on the coronal view by noting meniscal tissue extending into the tibial spine at the intercondylar notch. The average width of a normal meniscus is less than 11 mm. A bow-tie appearance should not be seen on more than two consecutive sagittal images because the conventional thickness of the sagittal slices is 3 mm and the interval between two consecutive slices is 1.5 mm. Two sagittal slices will cover a 9-mm thickness. A discoid meniscus can be diagnosed on the sagittal views by noting a bow-tie appearance on more than two consecutive images. Helms CA: MR image of the knee, in Fundamentals of Skeletal Radiology, ed 2. Philadelphia, PA, WB Saunders, 1995, pp 172-191.

Branches of the medial antebrachial cutaneous nerve can often be identified during routine ulnar nerve surgery crossing the medial aspect of the elbow. It should be preserved to avoid development of painful paresthesias.

12b 12c The CT scans reveal an occipital-cervical dissociation with subluxation of the occipitocervical joints bilaterally. Definitive management should consist of an occipital-cervical fusion with instrumentation. Immobilization in a Philadelphia collar is inadequate for this highly unstable injury, and halo immobilization, while affording adequate temporary immobilization, is not appropriate definitive management for this ligamentous injury. The patient does not have an injury at C4-C5 or C6-C7. Jackson RS, Banit DM, Rhyne AL III, et al: Upper cervical spine injuries. J Am Acad Orthop Surg 2002;10:271-280.

Fractures of the distal one third of the clavicle have a high incidence of delayed union (45% to 67%) and nonunion (22% to 33%) with nonsurgical management. Surgical stabilization with tension band techniques or a combination of plate and screw techniques is indicated, especially in young, active patients. In this patient, significant displacement of the fracture implies injury to the coracoclavicular ligaments with a higher risk of delayed union or nonunion. Various surgical treatments have been recommended, but the use of smooth wires is not indicated because of the potential for hardware migration. Jupiter JB, Ring D: Fractures of the clavicle, in Ianotti JP, Williams GR (eds): Disorders of the Shoulder: Diagnosis and Management, ed 1. Philadelphia, PA, Lippincott, Williams and Wilkins, 1999, pp 709-736.

The radiograph shows excessive thoracic kyphosis (normal 20 degrees to 50 degrees) with multiple contiguous vertebral wedging and end plate irregularity, all consistent with the diagnosis of Scheuermann's kyphosis. The patient is skeletally immature; therefore, there is the potential for progression of the kyphotic deformity. Extension bracing has shown efficacy in the treatment of Scheuermann's kyphosis that measures 50 degrees to 74 degrees, and has actually reduced the curvature permanently in some patients. A thoracolumbosacral orthosis may be used if the apex of kyphosis is at T7 or lower. Indications for surgical treatment are controversial, but spinal fusion most likely should not be considered for a painless kyphosis measuring less than 75 degrees. Murray PM, Weinstein SL, Spratt KF: The natural history and long-term follow-up of Scheuermann kyphosis. J Bone Joint Surg Am 1993;75:236-248. Wenger DR, Frick SL: Scheuermann kyphosis. Spine 1999;24:2630-2639.

41b 41c The radiographic appearance shows a slightly expansile lesion in the proximal phalanx of the fifth digit typical of an enchondroma. There is a stippled appearance within the bone and no evidence of cortical destruction. The biopsy reveals a cartilage lesion with basophilic cytoplasm. There are some hypercellular areas but no evidence of pleomorphism. Enchondromas in the tubular bones of the hand are usually more cellular than their counterparts in the femur and humerus and should not be considered malignant. No other lesions are noted in the radiograph, so a diagnosis of Ollier's disease cannot be made. An osteochondroma is a benign surface cartilage tumor. Brown tumor and osteomyelitis can be differentiated from enchondroma based on the histology. Wold LE, Adler CP, Sim FH, et al: Atlas of Orthopedic Pathology, ed 2. Philadelphia, PA, WB Saunders, 2003, p 225.

The presence of any curve greater than 20 degrees in a nonambulatory patient with Duchenne muscular dystrophy is an indication for posterior fusion with instrumentation. Because of progressive cardiomyopathy and pulmonary deficiency, waiting until the curve is larger can increase the risk of pulmonary or cardiac complications during or following surgery. There is some disagreement as to whether all such fusions must extend to the pelvis. Bracing or other nonsurgical management is ineffective and is not indicated in this situation. Sussman M: Duchenne muscular dystrophy. J Am Acad Orthop Surg 2002;10:138-151.

Although this patient had a hemothorax, the bleeding has stopped and he has been resuscitated to a euvolemic status with a small base deficit and good urine output. External fixation of both femurs is an option but an unnecessary step in the treatment algorithm. Nork SE, Agel J, Russell GV, et al: Mortality after reamed intramedullary nailing of bilateral femur fractures. Clin Orthop Relat Res 2003;415:272-278.

The findings are most consistent with a rupture of the anterior tibial tendon. The damaged area of tendon should be resected, followed by tendon reconstruction or tenodesis. The histology is not consistent with giant cell tumor of the tendon sheath, gout, or synovial sarcoma. Fibromatosis is characterized by a large number of spindle cells within the collagen background. Otte S, Klinger HM, Loreaz F, Haerer T: Operative treatment in case of closed rupture of the anterior tibial tendon. Arch Orthop Traum Surg 2002;122:188-190.

An avulsion fracture from the lateral tibial margin carries the eponym Segond fracture and is pathognomonic for an anterior cruciate ligament (ACL) tear. The fragment is located posterior to Gerdy's tubercle and is superior and anterior to the fibular head. It represents an avulsion of the lateral capsular ligament of the knee and is caused by the same mechanism that causes the ACL tear. The pes anserinus is the insertion point of the medial hamstrings and would not be affected in a lateral avulsion injury. The posterior cruciate ligament may be seen on a lateral view if associated with an avulsion fragment, but a tear of the PCL generally cannot be diagnosed on an AP view. The insertion of the iliotibial band is broad and is unlikely to produce an avulsion injury such as that seen in the radiograph. This view is not consistent with the appearance of a lateral collateral ligament injury. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 533-557.

The patient has the typical history and presentation of transient synovitis of the hip, a condition that is more common in children age 2 to 5 years but which may affect children up to 12 years. The discomfort typically is noted on awakening, and the child will refuse to walk. Later in the day, the pain commonly improves and the child can walk but will have a limp. Mild to moderate restriction of hip abduction is the most sensitive range-of-motion restriction. The extent of the evaluation for transient synovitis depends on the intensity and duration of symptoms. Because she has been afebrile for the past 24 hours, observation is the management of choice. In the differential diagnosis of suspected transient synovitis, septic arthritis of the hip is the primary disorder to exclude. Osteomyelitis of the proximal femur also should be considered. In most patients, clinical examination will differentiate of these disorders to a reasonable certainty. Plain radiographs are normal in the early stage of an infectious process. Ultrasonography shows increased fluid in the hip joint in both transient synovitis and septic arthritis. MRI can differentiate the two conditions; however, this test would require general anesthesia and is not required in most patients in this age group. If a child with transient synovitis has a concurrent infectious process such as an upper respiratory tract infection or otitis media, the temperature will most likely be elevated. In this situation, a full evaluation for an infectious process and initiation of IV antibiotics should be considered. This would include radiographs, CBC count, erythrocyte sedimentation rate, blood cultures, aspiration of the hip joint, and IV antibiotics. Del Beccaro MA, Champoux AN, Bockers T, Mendelman PM: Septic arthritis versus transient synovitis of the hip: The value of screening laboratory tests. Annals Emerg Med 1992;21:1418-1422.

Both the AAOS and AdvaMed, the medical device manufacturer's trade organization, have written guidelines that address potential conflicts of interest regarding interactions between physicians and manufacturer's representatives when it comes to patients' best interest. The AAOS feels that the orthopaedic profession exists for the primary purpose of caring for the patient and that the physician-patient relationship is the central focus of all ethical concerns. When an orthopaedic surgeon receives anything of significant value from industry, a potential conflict of interest exists. The AAOS believes that it is acceptable for industry to provide financial and other support to orthopaedic surgeons if such support has significant educational value and has the purpose of improving patient care. All dealings between orthopaedic surgeons and industry should benefit the patient and be able to withstand public scrutiny. A gift of any kind from industry should in no way influence the orthopaedic surgeon in determining the most appropriate treatment for his or her patient. Orthopaedic surgeons should not accept gifts or other financial support with conditions attached. Subsidies by industry to underwrite the costs of educational events where CME credits are provided can contribute to the improvement of patient care and are acceptable. A corporate subsidy received by the conference's sponsor is acceptable; however, direct industry reimbursement for an orthopaedic surgeon to attend a CME educational event is not appropriate. Special circumstances may arise in which orthopaedic surgeons may be required to learn new surgical techniques demonstrated by an expert or to review new implants or other devices on-site. In these circumstances, reimbursement for expenses may be appropriate. AAOS Standard of Professionalism -Orthopaedist -Industry Conflict of Interest (Adopted 4/18/07), Mandatory Standard numbers 6, 9, 12-15. www3.aaos.org/member/profcomp/SOPConflictsIndustry.pdf The Orthopaedic Surgeon's Relationship with Industry, in Guide to the Ethical Practice of Orthopaedic Surgery, ed 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2007. www.aaos.org/about/papers/ethics/1204eth.asp

The development of arthritis in SLAC wrist follows a consistent pattern. Beginning at the radial styloid to the scaphoid articulation, it progresses through the entire radioscaphoid joint and the midcarpal joint. In all stages, the radiolunate joint is spared, which is the basis for a scaphoid excision and four-corner fusion performed as a motion-sparing procedure for treatment of this condition. Wyrick JD: Proximal row carpectomy and intercarpal arthrodesis for the management of arthritis. J Am Acad Orthop Surg 2003;11:277-281. Watson HK, Ballett FL: The SLAC wrist: Scapholunate advanced collapse pattern of degenerative arthritis. J Hand Surg Am 1984;9:358-365.

The first rule of total knee arthroplasty is to restore the joint line to its original location. This will ensure optimal patellofemoral biomechanics and will facilitate ligament balancing. Changes on the tibial side affect both the flexion and extension gaps equally. Changes in femoral component sizing or position affect the flexion gap only. Tibial changes affect both the flexion and extension gaps. To convert a tight extension gap to a normal flexion gap, more distal femur needs to be resected. Vince KG: Revision knee arthroplasty technique. Instr Course Lect 1993;42:325-339.

The first branch of the lateral plantar nerve innervates the abductor digiti quinti, and more distal branches of the lateral plantar nerve supply the quadratus plantae and the interossei. The medial plantar nerve supplies the abductor hallucis brevis and the flexor digitorum brevis. Pansky B, House EH: Review of Gross Anatomy, ed 3. New York, NY, Macmillan, 1975, pp 464-476.

Traumatic dislocation of the hip in sports injuries is uncommon, and 85% to 92% occur in a posterior direction. In dislocations without fractures, osteonecrosis is the most common complication occurring in 10% to 20% of patients. MRI should be performed at 3 months postreduction to rule out osteonecrosis. Nerve injuries are rare in this setting, and recurrent dislocations are unusual without acetabular fractures. Chondrolysis has been reported as a rare occurrence. Anderson K, Strickland S, Warren R: Hip and groin injures in athletes. Am J Sports Med 2001;29:521-533.

At the level of L2, the liver and the vena cava lie to the right. The pancreas and duodenum are anterior to the aorta. The aorta lies in the midline just in front of the vertebral body. Clement CD: Anatomy: A Regional Atlas of Human Anatomy, ed 3. Baltimore, MD, Munich, Germany, Urban and Schwarzberg, 1987, Figure 331.

The most common causes of posterior ankle pain in ballet dancers are flexor hallucis longus tenosynovitis and os trigonum syndrome. Flexor hallucis longus tenosynovitis differs from a symptomatic os trigonum by the absence of pain with forced plantar flexion and the presence of pain with resisted plantar flexion of the great toe. The pain is often felt in the posterior ankle and can be associated with a snapping or triggering sensation. Os trigonum syndrome commonly occurs in ballet dancers who perform in a position of extreme plantar flexion. The pain occurs from entrapment of the os trigonum between the posterior portion of the talus and calcaneus. Hamilton WG, Geppert MJ, Thompson FM: Pain in the posterior aspect of the ankle in dancers: Differential diagnosis and operative treatment. J Bone Joint Surg Am 1996;78:1491-1500.

In this age group, bayonet apposition can produce very good results. Healing occurs rapidly, and remodeling usually is complete in less than 1 year. All of the other methods have significant risks of complications and are unnecessary for this fracture. Martin RF: Fractures of the proximal humerus and humeral shaft, in Letts RM (ed): Management of Pediatric Fractures. New York, NY, Churchill Livingstone, 1994, pp 144-148.

The patient's clinical signs (fever and flank, hip, and abdominal pain) suggest a primary iliopsoas abscess. With an increased patient population who abuse drugs and/or who are HIV-positive, iliopsoas abscess may be more prevalent because of systemic bacterial seeding and may be potentially unrecognized. Diagnostic imaging studies provide a better understanding of the anatomic magnitude of the infection, give concrete confirmation of the diagnosis, and may suggest an underlying cause. Neither standard abdominal radiographs nor ultrasound studies are sensitive enough to be diagnostic of this disease process. CT has been established as the standard study for identifying the underlying cause of this abscess. The hip infection has most likely developed as a result of hematogenous spread from an infected skin lesion from the patient's IV drug use. Santaella RO, Fishman EK, Lipsett PA: Primary vs secondary iliopsoas abscess: Presentation, microbiology, and treatment. Arch Surg 1995;130:1309-1313.

The history and presentation are consistent with type I Charcot-Marie-Tooth (CMT), the most common form of hereditary peripheral motor sensory neuropathy. Type I CMT is the most common, occurring in 50% of patients with CMT, and is characterized by marked slowing of motor neuron velocities, and inconsistent slowing of sensory neuron velocities. Peroneus longus to brevis transfer is indicated to release the overpull of the peroneus longus, and restore the eversion and dorsiflexion function of the peroneus brevis. A lateralizing calcaneal osteotomy with proximal translation is indicated to correct heel varus given that the Coleman block only allows for partial correction of heel varus. Proximal translation of the posterior tuber corrects for the increased calcaneal dorsiflexion, improving the lever arm for the triceps surae. A medial column closing wedge osteotomy is often required to correct a rigid, or semirigid plantar flexed first ray to allow for a balanced, plantigrade foot. Triple arthrodesis is indicated for rigid, arthritic hindfoot deformities. Transfer of the posterior tibial tendon to the tibialis anterior is not indicated since it is an out-of-phase transfer. Transfer of the posterior tibial tendon, when performed, should be to the lateral aspect of the foot. A medializing calcaneal osteotomy would accentuate the heel varus. There is no indication for Botox in CMT; Botox injection of the calf would further weaken push-off during gait. Bracing of a progressive semirigid or rigid deformity is not recommended. Younger AS, Hansen ST Jr: Adult cavovarus foot. J Am Acad Orthop Surg 2005;13:302-315. Sammarco GJ, Taylor R: Cavovarus foot treated with combined calcaneus and metatarsal ostetotomies. Foot Ankle Int 2001;22:19-30.

52b 52c 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. Unni KK: Dahlin's Bone Tumors: General Aspects and Data on 11,087 Cases, ed 5. Philadelphia, PA, Lippincott-Raven, 1996, pp 143-160.

Impaction grafting is an alternative for severe femoral bone deficiency; however, stem subsidence is commonly observed during the first few months. Slight subsidence is felt to be integral to the success of the procedure. Predictable bone graft incorporation and stable stem fixation have been reported in the medium-term. The incidence of periprosthetic fractures has been reported as high as 24%. Mikhail MWE, Weidenhielm L, Jazrawi LM, et al: Collarless, polished, tapered stem failure. J Bone Joint Surg Am 2000;82:1513-1514.

Ganglion cysts are the most common mass or mass-like lesions seen in the hand and wrist. They arise in a variety of locations, including synovial joints or tendon sheaths. The most common location is the dorsal/radial wrist arising from the dorsal scapholunate interosseous ligament.

Traumatic posterior instability is a common finding in football players, especially in the blocking positions as well as in the defensive linemen and linebackers. A traumatic blow to the outstretched arm results in posterior glenohumeral forces. Labral detachment at the glenoid rim is common. Patients report slipping or pain with posteriorly directed pressure. Rarely do these patients have true dislocations that require reduction; however, recurrent episodes of subluxation or pain are not uncommon. Posterior repair has been shown to be successful in the treatment of traumatic instability. Bottoni CR, Franks BR, Moore JH, et al: Operative stabilization of posterior shoulder instability. Am J Sports Med 2005;33:996-1002. Williams RJ III, Strickland S, Cohen M, et al: Arthroscopic repair for traumatic posterior shoulder instability. Am J Sports Med 2003;31:203-209.

Convex hemiarthrodesis and hemiepiphysiodesis are procedures designed to gradually reduce curve magnitude in congenital scoliosis because of hemivertebrae. They are used to surgically create an anterior and posterior bar to arrest growth on the convexity of the existing deformity. Success of the technique is predicated on continued growth on the concave side of the deformity. Prerequisites for this procedure include curves of limited length (less than or equal to five vertebrae), curves of reasonable magnitude (less than 70 degrees), absence of kyphosis, concave growth potential, and appropriate age (younger than age 5 years).

The recurrent laryngeal nerve lies between the trachea and the esophagus. The vagus nerve lies in the carotid sheath. The sympathetic trunk lies anterior to the longus colli muscles. The hypoglossal and superior laryngeal nerves are both at risk during the exposure but are not located between the trachea and the esophagus. Flynn TB: Neurologic complications of anterior cervical interbody fusion. Spine 1982;7:536-539.

The histology shows eosinophils with a background of larger cells (Langerhans' cells). This is consistent with eosinophilic granuloma. Localized sites are best treated with curettage, steroid injection, or observation. Chemotherapy is used only if there is systemic involvement. Mirra JM: Eosinophilic granuloma, in Bone Tumors: Clinical, Radiologic, and Pathologic Correlations. London, England, Lea and Febiger, 1989, pp 1023-1060. Sessa S, Sommelet D, Lascombes P, Prevot J: Treatment of Langerhans-cell histiocytosis in children: Experience at the Children's Hospital of Nancy. J Bone Joint Surg Am 1994;76:1513-1525.

27b The patient sustained a very distal supracondylar fracture of the humerus. Fractures in this area can disrupt the blood vessels supplying the lateral ossification center of the trochlea. With disturbance of the blood supply in this area, local osteonecrosis occurs and disrupts the support for the overlying articular surface, producing joint incongruity and localized degenerative arthritis. Haraldsson S: The interosseous vasculature of the distal end of the humerus with special reference to the capitellum. Acta Orthop Scand 1957;27:81-93.

Recent literature supports retention of well-fixed cemented femoral components when revising loosened cemented acetabular components. Current literature also supports the use of cementless components for revision of loosened cemented acetabular components. Peters CL, Kull L, Jacobs JJ, Rosenberg AG, Galante JO: The fate of well fixed cemented femoral components left in place at the time of revision of the acetabular component. J Bone Joint Surg Am 1997;79:701-706. Poon ED, Lachiewicz PF: Results of isolated acetabular revisions: The fate of the unrevised femoral component. J Arthroplasty 1998;13:42-49. Moskal JT, Shen FH, Brown TE: The fate of stable femoral components retained during isolated acetabular revision: A six- to twelve-year follow-up study. J Bone Joint Surg Am 2002;84:250-255.

Nonsurgical modalities remain the mainstay for treatment of herniated disks. Spontaneous resorption of herniated disks frequently is detected by MRI. Marked infiltration by macrophages and neovascularization are observed on histologic examination of herniated disks, and the resorption is believed to be related to this process. Many cytokines such as vascular endothelial growth factor, tumor necrosis factor-alpha, and metalloproteinases have been implicated in this process, but none has been found to be singularly responsible. Haro H, Kato T, Kamori H, et al: Vascular endothelial growth factor (VEGF)-induced angiogenesis in herniated disc resorption. J Orthop Res 2002;20:409-415.

Persistent pain following an ankle sprain can present a diagnostic dilemma. All of the injuries listed should be considered in the differential diagnosis. The superficial peroneal nerve courses in the lateral compartment and exits the crural fascia 12 to 15 cm above the level of the ankle. Muscle herniation through the fascial defect has been reported to be associated with entrapment of this nerve. The fascial hiatus also may serve as a potential tether in cases of inversion injuries causing injury to the superficial peroneal nerve. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 101-111.

The imaging studies reveal findings typical of the os trigonum syndrome. This condition results from inflammation between the os trigonum and the adjacent talus. The symptoms of posterior ankle pain are exacerbated by plantar flexion, which stresses the fibrous union between these two bones. Definitive management of the high-level athlete involves excision of the os trigonum from a medial approach, although arthroscopic excision has also been described. The os trigonum is not an intra-articular structure; therefore, ankle arthroscopy is neither diagnostic nor therapeutic. Abramowitz Y, Wollstein R, Barzilay Y, et al: Outcome of resection of a symptomatic os trigonum. J Bone Joint Surg Am 2003;85:1051-1057. Mouhsine E, Crevoisier X, Leyvraz P, et al: Post-traumatic overload or acute syndrome of the os trigonum: A possible cause of posterior ankle impingement. Knee Surg Sports Traumatol Arthrosc 2004;12:250-253.

Thumb adduction is powered by the adductor pollicis (ulnar nerve). Testing involves having the patient forcibly hold a piece of paper between the thumb and radial side of the index proximal phalanx. When this muscle is weak or nonfunctioning, the thumb interphalangeal joint flexes with this maneuver, resulting in a positive Froment sign. The paper is held by action of the thumb flexion (flexor pollicis longus and flexor pollicis brevis; median innervated).

The radiographs show a significant loss of the proximal anterior tibial cortex, consistent with an extensively damaged or deficient extensor mechanism. Such a deficit precludes insertion of another knee arthroplasty. Arthrodesis is the treatment of choice for this patient and is indicated for loss of the extensor mechanism and knee instability. A recent report on arthrodesis following removal of an infected prosthesis showed a union rate of 91% using a short intramedullary nail. Insertion of an antibiotic-impregnated PMMA spacer is not indicated because the rationale for using a spacer is to maintain a space for reinsertion of another prosthesis. Reconstruction of the extensor mechanism would not address the loss of the joint. Amputation is the final treatment option if the arthrodesis fails. Rand JA: Alternatives to reimplantation for salvage of the total knee arthroplasty complicated by infection. J Bone Joint Surg Am 1993;75:282-289. Lai KA, Shen WJ, Yang CY: Arthrodesis with a short Huckstep nail as a salvage procedure for failed total knee arthroplasty. J Bone Joint Surg Am 1998;80:380-388.

Radiography is the best initial study for the evaluation of diskogenic low back pain. The normal degenerative process can be evaluated. Vacuum phenomenon may be found within the disk space. Other possible sources for back pain should also be evaluated. The other tests may be beneficial but represent later imaging options.

Conus medullaris syndrome describes isolated loss of bowel and bladder function, usually at T12-L1 but can include T11-L2. In central cord syndrome, lower extremity motor function is better than upper extremity function. Cauda equina syndrome generally involves injury at the lumbar levels, with some degree of lower extremity motor loss. Posterior cord syndrome is characterized by preservation of motor function below the level of injury and position/vibratory sensory loss. In anterior cord syndrome, the lower extremity findings include loss of light touch, sharp/dull, and temperature sensations below the level of injury, as well as motor function. Apple DF Jr: Spinal cord injury rehabilitation, in Rothman RH, Simeone FA (eds): The Spine, ed 3. Philadelphia, PA, WB Saunders, 1992, Chapter 31.

Most of these injuries occur in young, active patients. Success rates for nonsurgical management are only marginally better than 50%. The treatment of choice is early surgery for patients who desire a quick return to a sport or active lifestyle. Subluxation of the peroneal tendons leads to longitudinal tears over time. McLennan JG: Treatment of acute and chronic luxations of the peroneal tendons. Am J Sports Med 1980;8:432-436.

Changing from a solid keel to a keel with a sagittal split allows an amputee to navigate uneven terrain more easily. Changing the length of the keel affects the responsiveness of the prosthesis but does not address the surface conditions for ambulation. The SACH is not used as frequently anymore, because overload problems to the nonamputated foot have been observed. Koval K (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 31-45.

In the presence of a supination external rotation-type fracture of the distal fibula (Weber type B), stability of the ankle is best assessed by performing an external rotation stress AP view of the ankle. This test is used to assess the integrity of the deltoid ligament. The presence of a deltoid ligament rupture results in instability and generally is best managed surgically. The gravity stress test can also be used. Egol KA, Amirtharajah M, Tejwani NC, et al: Ankle stress test for predicting the need for surgical fixation of isolated fibular fractures. J Bone Joint Surg Am 2004;86:2393-2398. McConnell T, Creevy W, Tornetta P III: Stress examination of supination external rotation-type fibular fractures. J Bone Joint Surg Am 2004;86:2171-2178.

This skeletally immature patient has a small OCD lesion that appears stable, and he has not undergone any treatment. Therefore, a trial of immobilization until pain resolves is the best initial choice. Thereafter, cessation of sport activities for 4 to 6 months may allow healing of the lesion. Surgical treatment of juvenile OCD lesions is reserved for unstable lesions, patients who have not shown radiographic evidence of healing and are still symptomatic after 6 months of nonsurgical management, or patients who are approaching skeletal maturity. Good results with stable in situ lesions that have failed to respond to nonsurgical management have been reported with both transarticular and retroarticular drilling. Results after excision alone are poor at 5-year follow-up, and it is unclear if microfracture will improve the long-term outcome. Mosaicplasty may be the next best option for patients who remain or become symptomatic after excision of the fragment and microfracture. Wall E, Von Stein D: Juvenile osteochondritis dissecans. Orthop Clin North Am 2003;34:341-353.

Although there is strong clinical and laboratory evidence that suggests smaller head size is linked with lower rates of polyethylene wear, moving to the use of 22-mm heads from larger sizes would tend to increase the dislocation rate. The key premise to this argument is that the absolute size of the femoral neck remains unchanged. While neck diameters were appropriate for the early monoblock femoral components, the use of modular femoral stems allows the surgeon to place 22-mm heads onto the same neck and trunion as used by larger heads. This has the effect of lessening the head-to-neck diameter ratio, which then accentuates the rate of impingement and dislocation. Reducing the neck diameter in proportion to the head diameter would eliminate the range-of-motion penalty accompanying head size reduction. Scifert and associates used a three-dimensional finite element model to study various combinations of femoral head size and neck ratios. They found that increasing the diameter of the femoral head while maintaining a constant head-to-neck diameter had the effect of significantly increasing the resisting moment necessary to induce a dislocation. The higher the head-to-neck ratio, the greater the range of motion until impingement and the greater the range of motion to dislocation.

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. 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.

A posterolateral approach to the posterior malleolus proceeds between the lateral and deep posterior compartments. Distally, the peroneus brevis muscle lies most medially within the lateral compartment, and the flexor hallucis longus lies most laterally in the deep posterior compartment. Henry AK: Extensile Exposure, ed 2. Edinburgh, UK, Churchill Livingstone, 1973, pp 269-270.

Patellar clunk syndrome is usually the result of a fibrous nodule that forms on the undersurface of the distal quadriceps tendon. It may get entrapped in the intercondylar notch of the femoral component during flexion, and lead to a sudden snap as the nodule is pulled out of the notch during active extension. Nonsurgical management is rarely successful. Surgical debridement is usually curative, with only rare recurrence. More aggressive procedures such as realignment, revision, or patellectomy are usually not necessary, and are reserved for cases resistant to soft-tissue debridement. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, p 329. Diduch DR, Scuderi GR, Scott WN, et al: The efficacy of arthroscopy following total knee replacement. Arthroscopy 1997;13:166-171.

The posterior medial approach through the semimembranosus/medial gastrocnemius interval is used in the inlay technique for PCL reconstruction. Exposure of the posterior capsule of the knee through this interval provides the greatest margin of safety to avoid injury to the tibial nerve, motor branch of the medial gastrocnemius, and the peroneal nerve. The direct posterior approach using the medial sural cutaneous nerve allows exposure of the popliteal neurovascular structures, but deep dissection through this interval places the motor branch of the medial gastrocnemius at risk. The interval between the semitendinosus and semimembranosus is used in accessory incisions with medial meniscus repairs but does not allow exposure of the PCL insertion. Berg EE: Posterior cruciate tibial inlay reconstruction. Arthroscopy 1995;11:69-76.

The patient has a stable flexion-compression injury of the cervical spine. The fracture occurs as a result of compression failure of the vertebral body. If the force continues, a tension failure of the posterior structures occurs, leading to potential dislocation. Immobilization in a rigid cervical orthosis will allow this fracture to heal. Clark CR (ed): The Cervical Spine, ed 3. Philadelphia, PA, Lippincott-Raven, 1998, pp 457-464.

As a side effect of treatment, phenytoin induces osteomalacia, or rickets, in growing children, through interference with metabolism of vitamin D. Oral supplementation of vitamin D can minimize this effect in patients who are undergoing prolonged treatment with phenytoin.

Indications for open reduction of glenoid intra-articular fractures include those fractures with a 5-mm articular surface displacement or when the humeral head is subluxated with the fracture fragment. Kavanaugh and associates and Leung and Lam have shown that the posterior approach with plate fixation is best for most glenoid fractures, including the Ideberg type II fracture shown here. The anterior approach is best used for anterior rim and transverse fractures. Kavanagh BF, Bradway JK, Cofield RH: Open reduction and internal fixation of displaced intra-articular fractures of the glenoid fossa. J Bone Joint Surg Am 1993;75:479-484. Leung KS, Lam TP: Open reduction and internal fixation of ipsilateral fractures of the scapular neck and clavicle. J Bone Joint Surg Am 1993;75:1015-1018.

In an acute first-time dislocation, arthroscopy has been shown to reveal a Bankart lesion in most shoulders. The classic finding of labral detachment from the anterior inferior glenoid along with occasional hemorrhage within the inferior glenohumeral ligament is the most common sequelae of a traumatic anterior inferior dislocation. Acute treatment, if chosen, is repair of the labral tissue back to the glenoid plus or minus any capsular plication to address potential plastic deformation of the glenohumeral ligament. Acute treatment of a patient sustaining a first-time dislocation remains controversial. The potential indications may be patients whose dislocation occurs at the end of a season and when the desire to minimize risk of future instability outweighs the risks of surgical intervention. Taylor DC, Arciero RA: Pathologic changes associated with shoulder dislocations: Arthroscopic and physical examination findings in first-time, traumatic anterior dislocations. Am J Sports Med 1997;25:306-311. DeBerardino TM, Arciero RA, Taylor DC, et al: Prospective evaluation of arthroscopic stabilization of acute, initial anterior shoulder dislocations in young athletes: Two- to five-year follow-up. Am J Sports Med 2001;29:586-592.

Prior to transport, the face mask should be removed so that the airway can be easily accessible. If serious injury is suspected, the helmet and shoulder pads should be left in place until he is assessed at the hospital and radiographs are obtained. Leaving the helmet and shoulder pads in place helps to keep the spine in the most neutral alignment. Removal of the helmet will result in extension of the neck, whereas removal of the shoulder pads will most likely result in flexion of the neck. Clark CR (ed): The Cervical Spine, ed 3. Philadelphia, PA, Lippincott Williams & Wilkins, 1998, p 376. Thomas B, McCullen GM, Yuan HA: Cervical spine injuries in football players. J Am Acad Orthop Surg 1999;7:338-347. Waninger KN, Richards JG, Pan WT, et al: An evaluation of head movement in backboard-immobilized helmeted football, lacrosse, and ice hockey players. Clin J Sport Med 2001;11:82-86. Donaldson WF III, Lauerman WC, Heil B, et al: Helmet and shoulder pad removal from a player with suspected cervical spine injury: A cadaveric model. Spine 1998;23:1729-1732.

According to Morgan and associates, a type II SLAP lesion can create or is associated with a superior instability pattern. They suggest that this can exist without a co-existing anteroinferior instability pattern. They reported that repair of the SLAP lesion alone resulted in satisfactory outcomes in 90% of patients and a return to throwing in more than 90% of pitchers. The arthroscopic findings in this patient do not support a diagnosis of anteroinferior laxity or instability; therefore, thermal capsular shift or capsular placation is not necessary. Morgan CD, Burkhart SS, Palmeri M, et al: Type II SLAP lesions: Three subtypes and their relationships to superior instability and rotator cuff tears. Arthroscopy 1998;14:553-565. Mileski RA, Snyder RJ: Superior labral lesions in the shoulder: Pathoanatomy and surgical management. J Am Acad Orthop Surg 1998;6:121-131.

During the late acceleration phase of throwing, the triceps forcibly contracts, extending the elbow as the ball is released. Normally, this force is absorbed by the anterior capsule and the brachialis and biceps muscles. However, if the ulnar collateral ligament is insufficient, the elbow will be in a subluxated position during extension and cause impaction of the olecranon and the olecranon fossa posteromedially. Over time, osteophyte formation is likely to occur. Conway JE, Jobe FW, Glousman RE, Pink M: Medial instability of the elbow in throwing athletes: Treatment by repair or reconstruction of the ulnar collateral ligament. J Bone Joint Surg Am 1992;74:67-83.

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. Scarborough M, Moreau G: Benign cartilage tumors. Orthop Clin North Am 1996;27:583-589.

The risk of infection in a 3B open tibia fracture is most directly related to the timing of the soft-tissue coverage and less related to the size or location of the wound. The wound VAC does not lower or raise the risk of infection in open fractures. It does appear to increase the window of time to obtain coverage without increasing the risk of infection. Additionally, the wound VAC may decrease the probability of needing free tissue coverage. Intramedullary nailing has not been shown to lower the risk of infection in 3B fractures. Godina M: Early microsurgical reconstruction of complex trauma of the extremities. Plast Reconstr Surg 1986;78:285-292. Dedmond BT, Kortesis B, Punger K, et al: The use of negative-pressure wound therapy (NPWT) in the temporary treatment of soft-tissue injuries associated with high-energy open tibia shaft fractures. J Orthop Trauma 2007;21:11-17.

23b The radiographs show the osteophytic build-up of the posteromedial corner of the elbow that occurs with valgus extension overload in the pitching elbow. This is the result of excessive valgus forces during the acceleration and deceleration phases of throwing. These forces, coupled with medial elbow stresses, cause a wedging of the olecranon into the medial wall of the olecranon fossa. Valgus instability of the elbow may further stimulate osteophyte formation. Repetitive impact of a spur within the olecranon fossa may cause fragmentation and eventual formation of loose bodies. Azar FM, Wilk KE: Nonoperative treatment of the elbow in throwers. Oper Tech Sports Med 1996;4:91-99. Field LD, Savoie FJ: Common elbow injuries in sport. Sports Med 1988;26:193-205.

Throwing athletes, particularly pitchers, have a high incidence of shoulder pain. Recent evidence suggests that posteroinferior capsular tightness and scapular dyskinesis may play a substantial role in the pathologic cascade, culminating in the development of articular surface rotator cuff tears and tearing of the posterosuperior labrum. These patients have posterosuperior shoulder pain primarily. Furthermore, these athletes are susceptible to a muscular fatigue syndrome, the SICK (Scapular malposition, Inferior medial border prominence, Coracoid pain and malposition, and dysKinesis of scapular movement) scapula syndrome. This patient has an internal rotation deficit and tenderness over the coracoid. The internal rotation deficit is addressed by stretching the posterior capsule. The tenderness over the coracoid has been attributed to a contracture of the pectoralis minor tendon secondary to scapular malposition. The initial phase of the rehabilitation regimen is directed at stretching the posterior capsule and pectoralis minor tendon. Burkhart SS, Morgan CD, Kibler WB: The disabled throwing shoulder: Spectrum of pathology. Part III. Arthroscopy 2003;19:641-661.

A Hawkins III fracture-dislocation generally presents with posteromedial displacement with the deltoid ligament intact. Therefore, the only remaining blood supply is the deltoid branch of the artery of the tarsal canal originating from the posterior tibial artery. Often, the medial malleolus is fractured, assisting in reduction and visualization of fracture reduction. If the medial malleolus is intact, a medial malleolus osteotomy allows visualization of the reduction without compromising the last remaining blood supply to the talus. Mulfinger GL, Trueta J: The blood supply of the talus. J Bone Joint Surg Br 1970;52:160-167.

20b The projectile entered the left shoulder and traveled to the right neck; therefore, a high incidence of suspicion must be directed to the airway, great vessels of the neck, and contents of the mediastinum. Immediate assessment of airway, breathing, and circulation takes priority, followed by examination of the neurologic status and other systems, as determined by the examination findings. Subcommittee on ATLS of the American College of Surgeons Committee on Trauma 1993-1997, Spine and Spinal Cord Trauma; Advanced Trauma Life Support Student Manual, ed 6, 1997. International Standards for Neurological and Functional Classification of Spinal Cord Injury. American Spinal Injury Association and International Medical Society of Paraplegia (ASIA/IMSOP).

Transient ulnar nerve palsy is the most common palsy following elbow arthroscopy. The ulnar nerve is most frequently affected, followed by the radial nerve. Injury to the other nerves has been reported but less frequently. Kelly EW, Morrey BF, O'Driscoll SW: Complications of elbow arthroscopy. J Bone Joint Surg Am 2001;83:25-34.

38b The patient has a flexible hallux varus that is a complication of the bunion surgery. With joints that are not arthritic and still flexible, a medial release is necessary to realign the joint. The extensor hallucis longus split transfer helps maintain position and still preserve motion at the interphalangeal joint level. Arthrodesis is a salvage procedure. Soft-tissue releases alone are most likely inadequate. Excision of the lateral sesamoid is contraindicated because that further compromises the forces resisting hallux varus. Phalangeal osteotomy would not address the medial subluxation at the metatarsophalangeal joint. Richardson EG (ed): Orthopaedic Knowledge Update: Foot and Ankle 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 27-32.

27b 27c 27d 27e The clinical photographs and radiographs reveal a distal phalangeal amputation with soft-tissue coverage over nonexposed bone. This is an ideal circumstance to allow healing by secondary intention with wet-to-dry dressing changes. There are few complications and the aesthetics surpass that of any soft-tissue reconstruction procedure. Volar advancement flaps (Moberg flaps) are limited to small defects about the thumb. A thenar flap will provide good coverage; however, the results are not comparable to simple dressing changes. A V-Y flap is useful when there is more tissue loss dorsally. Jebson PL, Louis DS: Amputations, in Green DP, Hotchkiss RN, Pederson WC, et al (eds): Green's Operative Hand Surgery, ed 5. Philadelphia, PA, Elsevier, 2005, p 1947.

Total elbow arthroplasty has become the treatment of choice for complex, comminuted distal humeral fractures in patients older than age 70 years. It yields a faster recovery with more predictable functional outcomes, although limitations of lifting weight of more than 5 pounds must be followed to avoid loosening. Kamineni S, Morrey BF: Distal humeral fractures treated with noncustom total elbow replacement. J Bone Joint Surg Am 2004;86:940-947.

Flexor digitorum profundus rupture or "rugger jersey finger" often occurs in the ring finger after the player misses a tackle and catches the digit on the shirt of the opposing player. Surgical repair is required for zone I-type injuries. Moiemen NS, Elliot D: Primary flexor tendon repair in zone I. J Hand Surg Br 2000;25:78-84.

Because of the long disease-free interval, it cannot be assumed that this is breast cancer. The lesion could represent metastasis from a new primary tumor or could itself be a primary tumor. CT-guided biopsy will most effectively identify the lesion and guide treatment options. Depending on the specific diagnosis, any of the other options may be appropriate.

The CT scan reveals a left-sided psoas abscess. Irritation of the saphenous division of the femoral nerve can cause paresthesias along the medial aspect of the knee. Pain is usually improved with hip flexion. Cellier C, Gendre JP, Cosnes J, et al: Psoas abscess complication Crohn's disease. Gastroenterol Clin Biol 1992;16:235-238.

Water is the most abundant component of articular cartilage with a wet weight of 65% to 80%. Of the water, 80% is at the surface and 65% at the deep zone. Collagen accounts for 10% to 20% of the wet weight, with type II collagen accounting for 90% to 95% of the total collagen content. Small amounts of types V, VI, IX, X, and XI collagen are also present. Proteoglycans comprise 10% to 15% of the wet weight of collagen. The remainder of the wet weight is made up of other collagens, noncollagenous proteins, and chondrocytes.

Isometric quadriceps contraction between 15 and 30 degrees of flexion creates significant strain in the ACL and potential damage to the reconstructed graft. Isolated quadriceps contraction with knee flexion of greater than 60 degrees, hamstring contraction at any angle of knee flexion, and active knee motion between 35 and 90 degrees of flexion create substantially less strain in the properly implanted ACL graft. Beynnon BD, Gleming BC, Johnson RL, Nichols CE, Renstrom PA, Pope MH: Anterior cruciate ligament strain behavior during rehabilitation exercises in vivo. Am J Sports Med 1995;23:24-34.

The valgus stress at the elbow caused by throwing strains the medial collateral ligament. The medial epicondyle, on which the ligament inserts, is the last ossification center to fuse to the distal humerus, and acute avulsion of the medial epicondyle can occur in adolescents. If the elbow is allowed to heal in a displaced position, valgus instability and loss of elbow extension may result. Valgus instability is especially problematic for the throwing athlete. Surgical treatment with rigid internal fixation is the treatment of choice for displaced medial epicondyle avulsion fractures. Valgus instability is prevented, and the rigid fixation allows for early range of motion. Case SL, Hennrikus WL: Surgical treatment of displaced medial epicondyle fractures in adolescent athletes. Am J Sports Med 1997;25:682-686.

The compaction of FDBA is faster than that of fresh-frozen bone. The maximal stiffness reached by both materials when tested was the same (55 MPa), but the FDBA required fewer impactions to achieve that stiffness. Because it is easier to impact, the FDBA may be mechanically more efficient than the fresh-frozen bone in surgical conditions. The brittleness of irradiated FDBA, caused by loss of the capacity to absorb energy in a plastic way, increases the compactness and stiffness of morcellized grafts. The failure rate of fusion in adolescent idiopathic scoliosis has been shown to be much higher in FDBA than in either iliac crest bone graft or composite autograft with demineralized bone matrix. There is a greater erosive surface response to allograft when compared to autograft or frozen allograft, with a larger number of osteoclast and osteoblast nuclei seen microscopically. Cornu O, Libouton X, Naets B, et al: Freeze-dried irradiated bone brittleness improves compactness in an impaction bone grafting model. Acta Orthop Scand 2004;75:309-314. Price CT, Connolly JF, Carantzas AC, et al: Comparison of bone grafts for posterior spinal fusion in adolescent idiopathic scoliosis. Spine 2003;28:793-798.

The arterial supply to the hand is abundant and normally duplicated. The deep palmar arch as shown in this arteriogram typically receives its primary contribution from the radial artery which travels deep to the first dorsal compartment tendons and then returns to the volar aspect of the palm through the first web space. The superficial palmar arch receives its supply from the ulnar artery and is not visualized in this patient.

The patient has primary scapulotrapezius winging caused by surgical damage to the spinal accessory nerve during a lymph node biopsy. Other causes include blunt trauma, traction, and penetrating injuries. With spinal accessory palsy, the shoulder appears depressed and laterally translated because of unopposed serratus anterior muscle function. With primary serratus anterior winging that is the result of long thoracic nerve palsy, the scapula assumes a position of elevation and medial translation with the inferior angle rotated medially. The thoracodorsal nerve innervates the latissimus dorsi and is not associated with scapular winging. Kuhn JE, Plancher KD, Hawkins RJ: Scapular winging. J Am Acad Orthop Surg 1995;3:319-325.

The spinal cord and spinal canal undergo dynamic changes during neck flexion and extension. In neck flexion, the spinal cord initially unfolds and then undergoes elastic deformation with full flexion; the spinal canal lengthens. This may explain the presence of Lhermitte's sign as the cord is pulled anteriorly over an anterior osteophyte or disk, generating a compressive force on the spinal cord. During neck extension, the spinal cord relaxes (folding like an accordion) and the spinal canal shortens. Breig A: Biomechanics of the Central Nervous System: Some Basic Normal and Pathologic Phenomena. Stockholm, Sweden, Almquist and Wiksell, 1960.

For the fibula (or any bone) to bow, a long-standing process needs to be present. Pressure from a rapid process would cause erosion, not allowing the bone to remodel. The other features are helpful confirmatory findings but also may be associated with aggressive processes. In this patient, the fibular deformity is caused by a sessile osteochondroma of the tibia. Lodwick GS, Wilson AJ, Farrell C, Virtama P, Dittrich F: Determining growth rates of focal lesions of bone from radiographs. Radiology 1980;134:577-583.

The patient has snapping hip syndrome of the internal type, which is more common in ballet dancers. It is caused by the iliopsoas tendon gliding over the iliopectineal line or the femoral head. The diagnosis usually can be made by the history and physical examination. Snapping is reproduced by hip flexion and extension or flexion with external rotation and abduction. Conventional and dynamic ultrasonography will confirm the snapping structure. Radiographs occasionally show calcifications near the lesser trochanter. MRI can be used to rule out other diagnoses that can simulate snapping hip. Gruen GS, Scioscia TN, Lowenstein JE: The surgical treatment of internal snapping hip. Am J Sports Med 2002;30:607-613.

The flexor sheaths are in continuity with the deep spaces of the hand. The flexor sheaths of the thumb and little finger communicate with the radial and ulnar bursae, respectively, and these two bursae commonly communicate. The central digits do not communicate as readily with deep spaces of the hand but if flexor tendon sheath infection of the index, long, and right fingers is neglected, the potential exists for rupture into the deep midpalmar spaces. Peimer CA (ed): Surgery of the Hand and Upper Extremity: Acute and Chronic Sepsis. New York, NY, Mcgraw Hill, 1996, pp 1735-1741.

The tibia has grown into valgus secondary to the proximal fracture. This occurs in about one half of these injuries, and maximal deformity occurs at 18 months postinjury. The deformity gradually improves over several years, with minimal residual deformity. Therefore, treatment at this age is unnecessary as there is a high rate of recurrence and complications regardless of technique. The valgus deformity is not a result of physeal injury or growth arrest. Medial proximal tibial hemiepiphysiodesis is an excellent method of correcting the residual deformity but is best reserved until close to the end of growth. Brougham DI, Nicol RO: Valgus deformity after proximal tibial fractures in children. J Bone Joint Surg Br 1987;69:482. McCarthy JJ, Kim DH, Eilert RE: Posttraumatic genu valgum: Operative versus nonoperative treatment. J Pediatr Orthop 1998;18:518-521.

The failure load of an evenly tensioned four-stranded hamstring tendon autograft has been reported to be 4,500 Newtons. The failure load of a 10-mm patellar tendon autograft has been estimated at 2,600 Newtons. The intact anterior cruciate ligament failure load has been calculated at 1,725 Newtons. Corry IS, Webb JM, Clingeleffer AJ, Pinczewski LA: Arthroscopic reconstruction of the anterior cruciate ligament: A comparison of patellar tendon autograft and four-strand hamstring tendon autograft. Am J Sports Med 1999;27:448-454. Hamner DL, Brown CH Jr, Steiner ME, et al: Hamstring tendon grafts for reconstruction of the anterior cruciate ligament: Biomechanical evaluation of the use of multiple strands and tensioning techniques. J Bone Joint Surg Am 1999;81:549-557.

The nerve roots of S2-5 are positioned dorsally and in the midline relative to the L5 and S1 nerve roots. The L5 nerve root is located lateral to S1 as it prepares to exit under the L5 pedicle. The S1 nerve root is located lateral and ventral to the S2-5 nerve roots. Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 3-17.

Ewing's sarcoma typically can occur in the diaphysis of the long bones (50% to 55%). It is often accompanied by a large soft-tissue mass. Abnormal findings are common, including a low-grade fever, an elevated ESR, and leukocytosis. The histology is consistent with a small round blue cell tumor. The unique pathology and other findings exclude osteosarcoma. Giant cell tumor and chondrosarcoma have a different histologic appearance and typically are more metaphyseal in location. Chondrosarcoma typically is found in older age groups, has a different histologic pattern, and rarely occurs in the midshaft of the femur.

During transaxillary resection of the first rib, the long thoracic nerve is at risk as it passes either through or posterior to the middle scalene muscle. Injury to this nerve may occur as the result of overly aggressive retraction of the middle scalene during the procedure. Leffert RD: Thoracic outlet syndrome. J Am Acad Orthop Surg 1994;2:317-325.

This fracture, known as a pilon fracture, represents comminution of the base of the middle phalanx with both palmar and dorsal cortical disruption. The treatment method that allows the best function and fewest complications is indirect reduction achieved through specific dynamic splinting or the use of specifically designed proximal interphalangeal joint external fixators. Early mobilization can be achieved by either of these techniques. Volar plate arthroplasty is indicated for a simple fracture-dislocation of the proximal interphalangeal joint with comminution of the volar fracture fragment and dorsal dislocation of the remaining articular surface. Open reduction and internal fixation or percutaneous pinning adds surgical risks and scarring and typically will not provide added stability. Cast immobilization will not achieve the goal of early range of motion. Stern PJ, Roman RJ, Kiefhaber TR, McDonough JJ: Pilon fractures of the proximal interphalangeal joint. J Hand Surg Am 1991;16:844-850.

Prospective studies, including randomized and randomized multicenter reports, have shown that percutaneous or mini-open acute Achilles tendon repair has comparable functional results when compared to traditional open techniques. Calder and Saxby reported one superficial infection out of 46 patients with a mini-open repair; Assal and associates and Cretnik and associates had no wound complications or infections. The other complications have not proved to be less likely with the mini-open or percutaneous technique. Assal M, Jung M, Stern R, et al: Limited open repair of Achilles tendon ruptures: A technique with a new instrument and findings of a prospective multicenter study. J Bone Joint Surg Am 2002;84:161-170. Calder JD, Saxby TS: Early, active rehabilitation following mini-open repair of Achilles tendon rupture: A prospective study. Br J Sports Med 2005;39:857-859.

Congenital anomalies of the spine, including failure of formation and failure of segmentation, are associated with other anomalies in other organ systems that develop at the same time. These include anomalies in the genitourinary system, cardiac anomalies, Sprengel's deformity, radial hypoplasia, and gastrointestinal anomalies including imperforate anus and trachealesophageal fistula. Spinal dysraphism is the most common associated abnormality. McMaster found an 18% incidence before the common use of MRI. Bradford and associates reported on 16 of 42 patients with congenital spinal anomalies and spinal dysraphism using MRI. Neural axis lesions may be associated with visible midline abnormalities such as a hairy patch or nevus. The child has already had a cardiac and renal work-up, and based on the findings of the hairy patch and congenital vertebral anomalies, MRI of the entire spine is prudent at this time. Spinal fusion is indicated for progressive congenital scoliosis or kyphosis. Physical therapy does not affect the natural history of congenital scoliosis. McMaster MJ: Occult intraspinal anomalies and congenital scoliosis. J Bone Joint Surg Am 1984;66:588-601. Bradford DS, Heithoff KB, Cohen M: Intraspinal abnormalities and congenital spine deformities: A radiographic and MRI study. J Pediatr Orthop 1991;11:36-41.

The imaging studies reveal a predominantly blastic lesion in the distal femur with posterolateral periosteal changes. The bone scan shows increased uptake in the distal femur, beyond that expected with radiography. Cross-sectional imaging confirms the presence of a soft-tissue mass extending from the lateral aspect of the femur, with diffuse intramedullary signal changes. This aggressive presentation, particularly in this location and in a patient of this age, is most consistent with osteosarcoma. The mineralization in the soft tissue strongly suggests neoplasm, not the reactive bony changes seen in an infectious process. Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 175-186.

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. 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.

The long-term effect of transient quadriplegia is unknown. Based on a history of one brief episode of transient quadriplegia and normal examination and MRI findings, the risk of permanent spinal cord injury with a return to play is low. There is a risk of recurrent episodes of transient quadriplegia after the initial episode. Morganti C, Sweeney CA, Albanese SA, et al: Return to play after cervical spine injury. Spine 2001;26:1131-1136. Odor JM, Watkins RG, Dillin WH, et al: Incidence of cervical spinal stenosis in professional and rookie football players. Am J Sports Med 1990;18:507-509. Torg JS, Naranja RJ Jr, Palov H, et al: The relationship of developmental narrowing of the cervical spinal canal to reversible and irreversible injury of the cervical spinal cord in football players. J Bone Joint Surg Am 1996;78:1308-1314.

When the arm is adducted, the superior structures, including the superior glenohumeral ligament, are responsible in limiting the inferior translation. With the arm abducted, the inferior glenohumeral ligament complex is responsible for limiting inferior subluxation. Rotator cuff activity can actually depress the humeral head and does not play a role in preventing inferior subluxation. The long head of the biceps and the posterior glenohumeral ligament do not play a role in protecting the shoulder from inferior instability. Warner JJ, Deng XH, Warren RF, Torzilli PA: Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint. Am J Sports Med 1992;20:675-685.

The status of the hips (located or dislocated) in children with thoracic-level myelomeningocele has no effect on the functional outcome of these patients. Management of unstable hips in this population should be limited to treatment of the contractures that may lead to poor limb positioning in either braces or a wheelchair. The use of the Pavlik harness and/or spica cast is contraindicated because they would promote flexion and abduction contractures. In the past, open reduction either through an anterior or medial approach had been performed with a high incidence of redislocation and other complications, with little functional gain for the child. Gabriel KG: Natural history of hip deformity in spina bifida, in Sarwark JR, Lubicky JP (eds): Caring for the Child With Spina Bifida. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2001, pp 89-103.

Bone destruction is primarily mediated by osteoclastic bone resorption, and cancer cells stimulate the formation and activation of osteoclasts next to metastatic foci. Increasing evidence suggests that receptor activator of NF-kB ligand (RANKL) is the ultimate extracellular mediator that stimulates osteoclast differentiation into mature osteoclasts. In contrast, OPG inhibits osteoclast development. IL-8 but not IL-5 is known to play a role in osteoclastogenesis. MMP-2 and collagen type I do not have a direct role in osteoclastogenesis. Kitazawa S, Kitazawa R: RANK ligand is a prerequisite for cancer-associated osteolytic lesions. J Pathol 2002;198:228-236.

Following a radial nerve neurapraxia above the elbow, muscle recovery can be expected in a predictable pattern. Although variations will occur, the return of function or reinnervation usually occurs in the following order: brachioradialis, extensor carpi radialis longus, supinator, extensor carpi radialis brevis, extensor carpi ulnaris, extensor digitorum comminus, extensor digiti minimi, extensor indicis proprious, extensor pollicis longus, abductor pollicis longus, and extensor pollicis brevis. Netter F: The Ciba Collection of Medical Illustrations: The Musculoskeletal System. Part 1, Anatomy, Physiology and Metabolic Disorders. West Caldwell, NJ, Ciba-Geigy, 1991, vol 8, p 53.