AAOS & ABOS Orthopedics MCQs (Set 1): Lower Extremity Trauma & Arthroplasty Complications | 2026 Board Prep

Cell activation and transcription varies with the target cell, the growth factor-receptor combination, and the biologic state of the cell. The growth factors in the transforming growth factor-beta (TGF-ß) superfamily signal through serine/threonine kinase receptors. Fibroblast growth factors, insulin-like growth factors, and platelet-derived growth factors signal through tyrosine kinase receptors. Growth hormone is released by the pituitary and circulates to the liver where target cells are stimulated to release insulin-like growth factor. Lieberman J, Daluiski A, Einhorn TA: The role of growth factors in the repair of bone: Biology and clinical applications. J Bone Joint Surg Am 2002;84:1032-1044.

A winged scapula is most often associated with Parsonage-Turner syndrome, a condition thought to be due to an inflammatory or immune-mediated mechanism. Certain muscles are predisposed, particularly the serratus anterior muscle innervated by the long thoracic nerve. Other less common nerve lesions (eg, the spinal accessory and dorsal scapular nerves) may also cause winged scapulae. Kline DG, Hudson AR: Nerve Injuries: Operative Results for Major Nerve Injuries, Entrapments and Tumors. Philadelphia, PA, WB Saunders, 1995.

In a retrospective review of 10 patients treated with hemivertebra excision for hemivertebra in the levels of T12 to L3, the procedure was found to be safe and effective. The procedure provided an average curve correction of 67 degrees and was greatest in patients who were younger than age 4 years at the time of surgery. Long anterior and posterior fusion with instrumentation is not the treatment of choice at this age. Either anterior hemiepiphyseodesis or posterior hemiarthrodesis in this isolated hemivertebra setting would be inadequate. Brace treatment is ineffective in management of the primary curvature.

The radiograph reveals a Crowe IV deformity in a patient with developmental dysplasia of the hip. If hip arthroplasty is performed, then some degree of limb lengthening is anticipated. Excessive limb lengthening can result in sciatic nerve palsy in these patients. The peroneal branch of the sciatic nerve is most often affected. Of the muscles listed, only the extensor hallucis longus is innervated by the peroneal branch of the sciatic nerve. Eggli S, Hankemayer S, Muller ME: Nerve palsy after leg lengthening in total replacement arthroplasty for developmental dysplasia of the hip. J Bone Joint Surg Br 1999;81:843-845.

The A2 and A4 pulleys are considered the most important parts of the pulley system. If these two structures are preserved, 80% of finger flexion can be maintained. If the pulley system is not left intact or is not reconstructed, "bow-stringing" of the flexor tendons occurs with loss of full flexion. The A2 pulley is over the proximal phalanx and the A4 pulley is over the middle phalanx. Doyle JR: Anatomy of the finger flexor tendon sheath and pulley system. J Hand Surg Am 1988;13:473-484.

V-Y advancement flaps are ideal for fingertip amputations that are transverse or dorsal oblique in nature. Healing by secondary intention is contraindicated with exposed bone. Shortening of exposed bone to allow primary skin closure is a possible alternative, as long as significant shortening of the index finger is avoided. A Moberg flap is useful only for distal amputations of the thumb. The first dorsal metacarpal artery-island pedicled flap uses tissue from the dorsum of the proximal index finger, and is typically used to resurface defects of the thumb. Fassler PR: Fingertip injuries: Evaluation and treatment. J Am Acad Orthop Surg 1996;4:84-92.

The patient has the dystrophic type of scoliosis seen in patients with neurofibromatosis type I (NF-1). The NF-1 gene is located on chromosome 17 and codes for neurofibromin, believed to be a tumor-suppresser gene. Abnormalities in the dystrophin gene are seen in Duchenne muscular dystrophy and Becker muscular dystrophy. A mutation in the frataxin gene is responsible for Friedreich ataxia. The most common type of hereditary motor and sensory neuropathy (Charcot-Marie-Tooth), HMSN type IA is caused by a complete duplication of the peripheral myelin protein gene. A defect in the cellular sulfate transport protein results in undersulfation of proteoglycans seen in diastrophic dysplasia.

The posttraumatic lumbar kyphotic deformity will not remodel and is likely to worsen with time because the central line of gravity lies anterior to the deformity and the ligamentous disruption will not heal. The worsening deformity also puts the patient at some risk for future neurologic damage. Ebraheim NA, Savolain ER, Southworth SR, et al: Pediatric lumbar seat belt injuries. Orthopedics 1991;14:1010-1013.

Gentamycin and the aminoglycosides (ie, streptomycin, tobramycin, amikacin, and neomycin) work by binding to the 30s ribosome subunit, leading to the misreading of mRNA. This misreading results in the synthesis of abnormal peptides that accumulate intracellularly and eventually lead to cell death. These antibiotics are bactericidal. Cephalosporins, vancomycin, and penicillins interfere with cell wall synthesis by inhibiting the transpeptidase enzyme. Polymyxin, nystatin, and amphotericin increase cell membrane permeability by disrupting the functional integrity of the cell membrane. The quinolones inhibit the enzyme, DNA gyrase. Lastly, metronidazole forms oxygen radicals that are toxic to anaerobic organisms because they lack the protective enzymes, superoxide dismutase and catalase.

IV broad-spectrum antibiotics should be administered for 7 days. This regimen, when compared to fragment removal or other antibiotic regimens, has been shown to reduce the incidence of spinal infections and reduce the need for metallic fragment removal with perforation of a viscus. Roffi RP, Waters RL, Adkins RH: Gunshot wounds to the spine associated with a perforated viscus. Spine 1989;14:808-811.

Most patients lose elbow range of motion after open reduction and internal fixation of a distal humeral fracture. Ulnar nerve dysfunction, nonunion, and infection all occur less commonly. Webb LX: Distal humerus fractures in adults. J Am Acad Orthop Surg 1996;4:336-344.

Age of menarche is the most accurate clinical factor to assess the degree of skeletal maturity in the female athlete. Such an assessment is necessary prior to ACL reconstruction in a skeletally immature female because of the risk of damage to the distal femoral and proximal tibial physes. Height of an older male sibling is not relevant to the female athlete. Parental height and recent change in shoe size are only moderately useful in predicting final growth, and hence, skeletal maturity. The presence of breast buds occurs early in adolescent development; therefore, its presence suggests a high likelihood of future growth. Micheli LJ, Foster TE: Acute knee injuries in the immature athlete. Instr Course Lect 1993;42:473-481. Stanitski CL: Anterior cruciate ligament injury in the skeletally immature patient: Diagnosis and treatment. J Am Acad Orthop Surg 1995;3:146-158.

The MRI scan shows an obvious talocalcaneal coalition of the medial facet. Because nonsurgical management has failed, surgical resection of the coalition is indicated. Arthrodesis would be indicated only if resection fails to relieve pain or if advanced degeneration of the hindfoot joints is present. McCormack TJ, Olney B, Asher M: Talocalcaneal coalition resection: A 10-year follow-up. J Pediatr Orthop 1997;17:13-15.

When external rotation at the side is limited, the most likely diagnosis is contracture of the rotator cuff interval, including the superior glenohumeral and coracohumeral ligaments. Therefore, the treatment of choice is arthroscopic release of the rotator cuff interval.

The radiographic findings are classic for synovial chondromatosis because of the small calcified opacities within the joint surrounding the synovium. The histologic findings show cartilaginous foci of metaplasia, which may be markedly cellular. However, unlike low-grade chondrosarcoma, it lacks cellular and nuclear pleomorphism. Murphy FP, Dahlin DC, Sullivan CR: Articular synovial chondromatosis. J Bone Joint Surg Am 1982;44:77-86.

Typically, posterior spinal fusion to the pelvis is recommended for patients with spinal muscular atrophy and advanced scoliosis. Examination for lower extremity muscle contractures is important because the contractures may interfere with good sitting balance. Anterior release and fusion usually are not advised. Diaphragmatic pacing is not indicated because diaphragm function usually is not affected. Patients with spinal muscular atrophy usually are not ambulatory or only marginally ambulatory at the time of scoliosis surgery; therefore, gait analysis usually is not relevant. While a muscle biopsy may have a role in the diagnosis of this disorder, it plays no subsequent role in determining life expectancy or the value of spinal surgery. Daher YH, Lonstein JE, Winter RB, Bradford DS: Spinal surgery in spinal muscular atrophy. J Pediatr Orthop 1985;5:391-395.

The history and radiographs indicate a Lisfranc fracture-dislocation of the foot. The radiographs show the classic "fleck sign," which is an avulsion of the Lisfranc ligament from the base of the second metatarsal. Most authors recommend open reduction and internal fixation of this injury. Closed reduction can be attempted, but anatomic reduction is unlikely because of the interposed bone fragments and soft tissues. Standard radiographs are not reliable in identifying 1 to 2 mm of subluxation of the tarsometatarsal joint. The tarsometatarsal joint has a poor tolerance to even mild subluxation, and the resulting decrease in joint contact area increases the likelihood of posttraumatic arthritis. Open reduction with the joint visible allows more anatomic reduction and internal fixation of larger osteochondral fragments or excision of smaller interposed fragments. Bellabarba C, Sanders R: Dislocations of the foot, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, vol 2, pp 1539-1558.

During the initial healing phases of a dural tear, pia and arachnoid from adjacent nerve roots migrate, fill the dural defect, and create a pia-arachnoid plug. It is this initial plugging of the defect that is believed to prevent further egress of cerebrospinal fluid through the defect. The plug has been shown to develop by the second postoperative day. Fibroblastic proliferation occurs within the dura itself and accounts for the bulbous ends of the dura seen in the photomicrograph. The appearance of the material within the dural edges is inconsistent with the appearance of neural elements, and scar tissue formation occurs later in the healing process. Cain JE Jr, Dryer RF, Barton BR: Evaluation of dural closure techniques: Suture methods, fibrin adhesive sealant, and cyanoacrylate polymer. Spine 1988;13:720-725.

For the parachute test, the examiner holds the child prone and then lowers the child rapidly toward the floor. The parachute reaction is normal or positive if the child reaches toward the floor. The Moro or startle reflex should not be present beyond age 6 months. Asymmetric tonic neck reflex, extensor thrust, and absent foot placement are abnormal findings at any age. Bleck EE: Orthopaedic Management in Cerebral Palsy. Lavenham, Suffolk, The Lavenham Press, 1987, pp 121-139.

Intravenous fluid administration is the best first step to treat the hypercalcemia of malignancy. Many of these patients are dehydrated, and the increased serum calcium impairs the ability of the kidney to concentrate the urine. The decreased glomerular filtration rate secondary to the hypovolemia also leads to increased tubular resorption of calcium. The establishment of normovolemia will help promote increased urinary excretion of calcium. Lasix can also be used to help promote calciuria. Mithramycin is an antibiotic derived from Streptomyces plicatus. It is part of a group of drugs referred to as chromomycin antibiotics and is the only one of this group used clinically in the United States. It is rarely used in cancer chemotherapy because of its toxicity. A number of drug-related deaths have occurred from the use of mithramycin. Its use is now limited to the treatment of hypercalcemia associated with malignancy where it is used in lower dosage than that used for the treatment of tumors. Methotrexate has no role in the treatment of hypercalcemia of malignancy. While intravenous bisphosphonates are helpful in slowing progression of metastases and may help lower cerum calcium, they are not appropriate in the emergent treatment of hypercalcemia in the metastatic cancer patient.

Errors in timing are by far the most common in this technically safe procedure. Incomplete growth arrest has been reported in up to 15% of patients versus timing errors in 61%. Fracture through the site has been reported rarely. Neurovascular and cartilaginous injury are extremely uncommon but always need to be considered when performing surgery in the vicinity of these structures. Blair VP III, Walker SJ, Sheridan JJ, Schoenecker PL: Epiphysiodesis: A problem of timing. J Pediatr Orthop 1982;2:281-284.

Cell surface glycoproteins present in the heterogeneous population of the cells within the graft are primarily responsible for the antigenicity. Macromolocules of the matrix have also been implicated. Cryopreserved grafts have less antigenicity than fresh. Freezing, freeze-drying, or chemical sterilization and antigen extraction of the bone allograft have all been shown to reduce the antigenicity of the graft. Freeze-drying of retroviral-infected cortical bone and tendon does not inactivate retrovirus. Immunosuppression has been shown to decrease response. Hematopoietic elements along with osteogenic, chondrogenic, fibrous, and vascular cells have been shown to be antigenic. Crawford MJ, Swenson CL, Arnoczky SP, et al: Lyophilization does not inactivate infectious retrovirus in systemically infected bone and tendon allografts. Am J Sports Med 2004;32:580-586. Stevenson S, Li XQ, Davy DT, et al: Critical biological determinants of incorporation of non-vascularized cortical bone grafts: Quantification of a complex process and structure. J Bone Joint Surg Am 1997;79:1-16.

The radiographic and clinical findings suggest a scapulothoracic dissociation with a widely displaced clavicular fracture and a laterally displaced scapula. These injuries have a high association with neurovascular injuries to the brachial plexus and subclavian artery. Emergent vascular evaluation with arteriography and possible vascular repair are indicated. This repair can be combined with open reduction and internal fixation of the clavicle to improve stability. Delay in treatment of these vascular injuries can be devastating. Iannotti JP, Williams GR (eds): Disorders of the Shoulder. Philadelphia, PA, Lippincott, 1999, pp 632-635.

Chordomas are very radio- and chemotherapy resistant; therefore, en bloc resection with a negative margin is the preferred treatment. Lesions at or below S3 can be resected without compromising pelvis stability, and continence usually is maintained. The mean survival rate for patients with sacral chordomas is approximately 7 years. Patients with chordoma of the mobile (cervical, thoracic, or lumbar) spine have a mean survival rate of approximately 5 years. This difference is most likely the result of an earlier diagnosis. Fardin DF, Garfin SR, Abitbol J, et al (eds): Orthopaedic Knowledge Update: Spine 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 123-133. Stener B, Gunterberg B: High amputation of the sacrum for extirpation of tumors: Principles and technique. Spine 1978;3:351-366.

Although considered benign bone lesions, lung metastases can develop in giant cell tumors and chondroblastomas. These often can be treated with multiple thoracotomies, resulting in long-term survival. Roberts PF, Taylor JG: Multifocal benign chondroblastomas: Report of a case. Hum Pathol 1980;11:296-298.

Malrotation of the foot is frequently overlooked in this clinical setting. This can be judged by evaluating and comparing the transmalleolar axes of the affected and unaffected legs. The rotation occurs through the physis and frequently is not recognized until the patient has been walking for a few months. The other conditions are not expected to occur in the clinical setting described. Phan VC, Wroten E, Yngve DA: Foot progression angle after distal tibial physeal fractures. J Pediatr Orthop 2002;22:31-35.

Early postoperative wound infections after open reduction and internal fixation should be treated with aggressive debridement and maintenance of stability of the fracture. If infection persists following healing of the fracture, the hardware should be removed. Carragee EJ, Csongradi JJ, Bleck EE: Early complications in the operative treatment of ankle fractures: Influence of delay before operation. J Bone Joint Surg Br 1991;73:79-82.

The history, physical examination, and radiographic findings are consistent with type IV sacral agenesis or caudal regression syndrome. These children are born with no lumbar spine or sacrum. The T12 vertebra is often prominent posteriorly. Popliteal webbing and knee flexion contractures are common with this diagnosis. There is a higher incidence of this diagnosis when the mother has diabetes mellitus. Maternal drug abuse and alcoholism can produce phenotypically unique children but without the findings described here. Maternal idiopathic scoliosis is not associated with caudal regression syndrome. Chan BW, Chan KS, Koide T, et al: Maternal diabetes increases the risk of caudal regression caused by retinoic acid. Diabetes 2002;51:2811-2816.

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 patient has grade IV heterotopic ossification with the limb in an abnormal nonfunctional position. Treatment should consist of excision of the bone to restore hip motion and prophylaxis to prevent recurrent formation. The best time to excise the bone is controversial, with no conclusive evidence supporting early or late excision. Pellegrini VD Jr, Koniski AA, Gastel JA, Rubin P, Evarts CM: Prevention of heterotopic ossification with irradiation after total hip arthroplasty: Radiation therapy with a single dose of eight hundred centigray administered to a limited field. J Bone Joint Surg Am 1992;74:186-200.

In an atrophic nonunion with a good soft-tissue envelope, adequate plating with cancellous bone graft can be used to span defects of up to 6 cm. Cortical graft from the fibula or iliac crest is not necessary. BMP-7 is a bone graft substitute and should not be used alone in this patient because the hardware is loose.

Compression plating remains the treatment of choice for most established humeral nonunions. Autograft is felt to be superior to allograft. Electrical stimulation has not been found to improve healing rates in patients with nonunion after intramedullary nailing. Retrograde nailing with flexible nails gives inadequate rotational control to promote healing in this patient. Adding cancellous graft alone will not stabilize the nonunion site. Dynamic locking has been successful only in the lower extremity because the bone can be loaded axially. McKee MD, Miranda MA, Riemer BL, et al: Management of humeral nonunion after the failure of locking intramedullary nails. J Orthop Trauma 1996;10:492-499.

The radiographs reveal a severely comminuted distal humerus fracture. A long arm cast, functional bracing, and closed reduction and percutaneous pin fixation all have a poor outcome and could result in a nonunion that will be very difficult to treat. Open reduction and internal fixation is indicated in most supracondylar humerus fractures, but total elbow arthroplasty is a good alternative in elderly patients who have multiple medical problems and when the fracture pattern may preclude stable enough internal fixation to allow postoperative motion. Cobb TK, Morrey BF: Total elbow arthroplasty as primary treatment for distal humeral fractures in elderly patients. J Bone Joint Surg Am 1997;79:826-832.

Acetabular protrusion in patients with rheumatoid arthritis moves the center of hip rotation medially and posteriorly. Positioning of the acetabular component in a patient with protrusion is best accomplished in the normal (anterior and inferior) position and not in a protruded position. This has been shown both clinically and in a finite-element analysis. Any medial positioning will produce impingement of the prosthesis neck on the rim, and superior placement produces improper hip mechanics. Crowninshield RD, Brand RA, Pedersen DR: A stress analysis of acetabular reconstruction in protrusio acetabuli. J Bone Joint Surg Am 1983;65:495-499.

If the Buford complex is mistakenly reattached to the neck of the glenoid, severe painful restriction of external rotation will occur. Williams MM, Snyder SJ, Buford D Jr: The Buford complex - the "cord-like" middle glenohumeral ligament and absent anterosuperior labrum complex: A normal anatomic capsulolabral variant. Arthroscopy 1994;10:241-247.

Although many hematologic and electrolyte abnormalities may be present in a patient with advanced metastatic cancer, an elevated serum calcium level is most commonly associated with confusion. Treatment with hydration, diuretics, and bisphosphonates is recommended. Clohishy D: Management of skeletal metastasis in clinical orthopaedics, in Craig E (ed): Operative Orthopaedics. Philadelphia, PA, Lippincott Williams & Wilkins, 1999, pp 994-997.

A recent randomized trial of surgical versus nonsurgical management of calcaneal fractures showed that patients who were on workers' compensation did poorly with surgical care. These patients had less favorable outcomes regardless of their initial management. Factors such as age, smoking, and vasculopathies compromise skin healing, leading to greater surgical risks. The best results were obtained in patients who are younger than age 40 years, have unilateral injuries and are injured during noncompensable activities. Women tend to do better with surgery than men. Howard JL, Buckley R, McCormack R, et al: Complications following management of displaced intra-articular calcaneal fractures: A prospective randomized trial comparing open reduction internal fixation with nonoperative management. J Orthop Trauma 2003;17:241-249.

Cryopreservation uses chemicals to remove cellular water and controlled rate freezing to prevent ice crystal formation. The tissue is procured, cooled to wet ice temperature for quarantine, and then stored in a container with cryoprotectant solution of dimethyl sulfoxide or glycerol which displaces the cellular water. The controlled rate freezing is then done to prevent ice crystal formation. Fresh allografts are not frozen in order to maintain maximum cellular viability, and this process limits the shelf life of osteochondral allografts. Freeze-drying involves replacement of water in the tissue with alcohol to a moisture level of 5% and then uses a vacuum process to remove the alcohol from the tissue. Preparation of fresh frozen grafts involves freezing the graft twice and packaging the tissue without solution at minus 80 degrees C. American Association of Tissue Banks: Standards for Tissue Banking. MacLean, VA, American Association of Tissue Banks, 1999. Vangsness CT Jr, Triffon MJ, Joyce MJ, et al: Soft tissue allograft reconstruction of the human knee: A survey of the American Association of Tissue Banks. Am J Sports Med 1996;24:230-234.

In a type III supracondylar distal humerus fracture of the elbow, the brachial artery can become incarcerated, yielding a pulseless extremity. In this situation, closed reduction may not be effective; therefore, open management is often necessary. The preferred surgical approach to the brachial artery and to this fracture is the anterior approach to the cubital fossa. The lacertus fibrosis is incised, and the dissection is carried out between the brachialis (musculocutaneous nerve) and the pronator teres (median nerve), mobilizing the brachial artery. Once the brachial artery is mobilized, the anterior elbow joint capsule may be exposed. The interval between the brachialis and the biceps describes the anterolateral approach to the elbow more commonly used for exposure of the proximal aspect of the posterior interosseous nerve. The dissection interval between the brachioradialis and the pronator teres describes the proximal extent of the anterior approach to the radius. Tubiana R, McCullough CJ, Masquelet AC: An Atlas of Surgical Exposures of the Upper Extremity. Philadelphia, PA, JB Lippincott, 1990, p 115.

Based on her symptoms and prior shoe wear modifications, the treatment of choice is surgical correction of the hallux valgus with a chevron osteotomy. There are no data to support the use of a custom orthosis to delay the progression of a hallux valgus deformity. Steroid injection would only risk infection, as well as joint and capsule damage. Extra-depth shoes are an option; however, the patient is interested in surgical options. Chou LB, Mann RA, Casillas MM: Biplanar chevron osteotomy. Foot Ankle Int 1998;19:579-584. Coughlin MJ: Roger A. Mann Award: Juvenile hallux valgus. Etiology and treatment. Foot Ankle Int 1995;16:682-697.

Bisphosphonates are stable analogues of pyrophosphate that have a strong affinity for bone hydroxyapatite; these agents inhibit bone resorption by reducing the recruitment and activity of osteoclasts and increasing apoptosis. Bone formed while patients are receiving bisphosphonate treatment is histologically normal. Bisphosphonates have been shown to be effective in decreasing pathologic fractures, bone pain, and the need for radiation therapy in patients with multiple myeloma and metastatic carcinoma to bone. The most effective method of administration is via monthly intravenous infusion. Osteonecrosis of the mandible is sometimes a complication of this treatment. Gass M, Dawson-Hughes B: Preventing osteoporosis-related fractures: An overview. Am J Med 2006;119:S3-S11.

Animal studies assessing the influence of fibrin glue supplementation have detected a markedly greater inflammatory response at the site of application. An increased incidence of infection and delays in healing were not noted. Cain JE Jr, Rosenthal HG, Broom MJ, Jauch EC, Borek DA, Jacobs RR: Quantification of leakage pressures after durotomy repairs in the canine. Spine 1990;15:969-970.

Anteromedial displacement of the tibial tubercle unloads the distal and lateral facets of the patella and shifts the forces to the proximal and medial facets. Therefore, if findings indicate arthrosis predominately in the medial and proximal areas of the patella, this is considered a relative contraindication because it may accentuate arthritic symptoms. Fulkerson JP: Anteromedialization of the tibial tuberosity for patellofemoral malalignment. Clin Orthop 1983;177:176-181. Bellemans J, Cauwenberghs F, Witvrouw E, et al: Anteromedial tibial tubercle transfer in patients with chronic anterior knee pain and a subluxation-type patellar malalignment. Am J Sports Med 1997;25:375-381.

In the early 1990s, a transition was made from a two-incision ACL reconstruction to a single-incision ACL reconstruction, and there was concern over divergence of the femoral screws. It was shown radiographically that approximately 5% of the time, divergence of the screw was greater than 15 degrees from the bone plug. In a bovine model, there was significant loss of pull-out strength with an increase in divergence from 15 degrees to 30 degrees. Therefore, attempts should be made to minimize divergence to 15 degrees or less. Lemos MJ, Jackson DW, Lee TO, et al: Assessment of initial fixation of endoscopic interference femoral screws with divergent and parallel placement. Arthroscopy 1995;11:37-41.

The patient has a symptomatic os trigonum caused by impingement that occurs with maximal plantar flexion of the ankle in the demi-pointe or full-pointe position. Patients frequently report posterolateral pain localized behind the lateral malleolus that may be misinterpreted as a disorder of the peroneal tendon. Pain with passive plantar flexion (the plantar flexion sign) indicates posterior impingement, not a problem with the peroneal tendon. The symptoms are not characteristic of a stress fracture, nor do the radiographs show a stress fracture or an osteochondritis dissecans lesion. The os trigonum is modest in its dimensions. The incidence or magnitude of symptoms does not correlate with the size of the fragment. Large fragments may be asymptomatic, while small lesions may create significant symptoms. Marotta JJ, Micheli LJ: Os trigonum impingement in dancers. Am J Sports Med 1992;20:533-536.

The figure shows the missing pedicle or "winking owl" sign that is characteristic of tumor involvement of the cortical bone of the pedicle. None of the other pathologic processes commonly gives this radiographic picture. Thinned, but not missing pedicles, have been described as a normal variant. McLain R, Weinstein J: Tumors of the spine, in Herkowitz HH (ed): The Spine, ed 4. Philadelphia, PA, WB Saunders, 1992, p 1173.

Only three thromboembolic treatment protocols have reached Grade 1A status for the American College of Chest Physicians Guidelines for thromboembolic prophylaxis after total hip arthroplasty and total knee arthroplasty. Grade 1A evidence shows a clear benefit/risk improvement with supportive data from randomized clinical trials, which are strongly applicable in most clinical circumstances. Warfarin is recommended but at an INR level of 2 to 3. Low-molecular-weight heparin and fondaparinox are also acceptable treatment options. Aspirin, adjusted dose unfractionated heparin, and elastic compressive stockings are not recommended as stand-alone options. Colwell C: Evidence based guidelines for prevention of venous thromboembolism: Symposia. Proceedings of the 2005 AAOS Annual Meeting. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 15-18.

The MRI scans reveal a large posterior paralabral cyst associated with a posterior-superior labral tear. The cyst appears as a well-defined, smoothly marginated mass with low signal intensity on T1-weighted MRI scans and with high signal intensity on T2-weighted MRI scans. MRI also reveals changes in the supraspinatus and infraspinatus muscles secondary to denervation, including decreased muscle bulk and fatty infiltration. MRI has the added advantage, compared with other imaging modalities, of detecting intra-articular lesions, such as labral tears, which are frequently associated with ganglion cysts of the shoulder. In this case of a professional baseball player with a space-occupying lesion causing nerve compression with an associated labral tear, the treatment of choice is arthroscopic decompression of the cyst and repair of the tear. Acromioplasty would not address the primary pathology in this patient. Cummins CA, Messer TM, Nuber GW: Suprascapular nerve entrapment. J Bone Joint Surg Am 2000;82:415-424.

A pure bending force produces a transverse fracture pattern. Spiral fractures are mainly rotational, oblique are uneven bending, segmental are four-point bending, and comminuted are either a high-speed torsion or crush mechanism. Tencer AF, Johnson KD: Biomechanics in Orthopaedic Trauma: Bone Fracture and Fixation. Philadelphia, PA, JB Lippincott, 1994. Gonza ER: Biomechanical long bone injuries, in Gonza ER, Harrington IJ (eds): Biomechanics of Musculoskeletal Injury. Baltimore, MD, Williams & Wilkins, 1982, pp 1-30.

Dickman and associates reported a greater than 10% incidence of vertebral artery anomalies at the C1-2 junction that would preclude the use of either unilateral or bilateral transarticular screw placement. They noted that 13 of 105 patients had a high-riding transverse foramen that precluded bilateral screw placement. In another series, 17 of 94 patients had unilateral high-riding transverse foramina and three had bilateral anomalies. Thin-cut CT with sagittal reconstructions offers the best visualization of the anomalous position of the vertebral artery. They noted that single screw placement in combination with posterior C1-2 fusion was an effective means to secure C1-2 stability. MRI gives excellent visualization of soft tissues and spinal cord compression but is not as clear as thin-cut CT for visualization of the vertebral artery foramina. Vertebral artery angiography is an invasive study with an inherent potential for complications. Electromyography does not correlate with vertebral artery anatomy. Paramore CG, Dickman CA, Sonntag VK: The anatomic suitability of the C1-2 complex for transarticular screw fixation. J Neurosurg 1996;85:221-224. Dickman CA, Sonntag VK: Posterior C1-C2 transarticular screw fixation for atlantoaxial arthrodesis. Neurosurgery 1998;43:275-280.

Older individuals ingest less Vitamin D and are unable to generate as much as younger people via the skin in response to ultraviolet exposure; thus, there is a decrease in the levels of serum 25(OH) D. This reduction in 25(OH)D leads to a reduction in calcium absorption. There is also decreased conversion in the kidney of 25(OH)D to 1,25(OH)D. This all leads to an increase in the daily requirements of both calcium and Vitamin D. It also results in a responsive increase in PTH secretion in the elderly, as well as renal function impairment and possible renal resistance to PTH. Dawson-Hughes B, Harris SS, Krall EA, et al: Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age and older. N Engl J Med 1997;337:670-676. Recker RR, Hinders S, Davies M, et al: Correcting calcium nutritional deficiency prevents spine fractures in elderly women. J Bone Miner Res 1996;11:1961-1966.

The radius of curvature of the distal femur is greater over the distal aspect of the lateral femoral condyle than the distal aspect of the medial femoral condyle. As the femur rolls posteriorly during early knee flexion, both condyles undergo similar angular changes equal to the amount of flexion. With a similar amount of angular rotation, the sphere with the larger radius experiences greater net rollback, producing a pivoting motion. Although the anterior cruciate ligament plays a role in producing tibial rotations, the posterior cruciate ligament does not play a significant role in producing such rotations. Similarly, the tibial tubercle does not play a significant role in producing normal rotations of the femur relative to the tibia. The popliteus may also play a role in producing rotational pivots, as might differential laxity of the medial and lateral collateral ligaments in early knee flexion. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 239-240.

The best initial test for this patient is to assess the vascular supply to the foot. An elderly smoker with diabetes mellitus has a high risk of peripheral vascular disease. Decreased weight bearing has not been successful. Although a bone scan might be helpful, it would take secondary consideration to the patient's vascular supply, especially in the absence of any acute infection. Monofilament testing would help diagnosis neuropathy, which is a root cause behind the ulcer forming, but does not prevent it from healing. The Thompson's test is used to diagnosis an Achilles tendon rupture.

The most important aspect of management of any open fracture, and in particular the tibia, is the degree and the completeness of the debridement of the soft tissue and most importantly, the muscle. The ultimate function is determined by the amount of muscle left, as well as the ability to heal. The amount of necrotic muscle left in the wound also determines the predisposition to infection. The method of fixation, the size of the wound, and the amount of contamination are controlled by the surgeon or the injury and have little to do with the long-term outcome. Initial wound cultures have little predictive value. Clifford P: Open fractures, in Ruedi TP, Murphy WM (eds): AO Principles of Fracture Management. Stuttgart, Thieme, 2000, pp 617-638.

The symptoms and MRI scan indicate dislocated peroneal tendons. In this patient, the structure that needs to be repaired is the superior peroneal retinaculum. If the popping was coming from a torn peroneal tendon, repair would involve the peroneal longus or brevis tendon, but this is not shown in the MRI scan. The anterior talofibular ligament or the calcaneofibular ligament would need to be repaired if the patient had ankle instability due to an ankle sprain. Jones DC: Tendon disorders of the foot and ankle. J Am Acad Orthop Surg 1993;1:87-94.

A C6-7 herniation affects the C7 root. The C7 root has the middle finger as its predominant sensory distribution. Its motor function is the triceps, wrist extension, and finger metacarpophalangeal extension. The reflex is the triceps. Magee D: Principles and concepts, in Orthopedic Physical Assessment, ed 3. Philadelphia, PA, WB Saunders, 1997, pp 1-18.

The radiographs show nonunion of both the greater and lesser tuberosities. Tuberosity pull-off and nonunion remain among the most common causes of failed humeral head arthroplasty for fracture. Strict attention to securing the tuberosities to each other and to the shaft, and autogenous bone grafting from the excised humeral head will decrease the incidence of pull-off and improve healing rates. Active-assisted range-of-motion and strengthening exercises should be delayed until tuberosity healing is noted radiographically, usually at 6 to 8 weeks postoperatively. Hartsock LA, Estes WJ, Murray CA, et al: Shoulder hemiarthroplasty for proximal humeral fractures. Orthop Clin North Am 1998;29:467-475. Hughes M, Neer CS: Glenohumeral joint replacement and postoperative rehabilitation. Phys Ther 1975;55:850-858.

The differential diagnosis of genu varum includes physiologic genu varum, Blount's disease, skeletal dysplasia, and metabolic bone disease. Children with Blount's disease are generally in the 95th percentile for height and weight, and usually multiple family members are not affected. The radiographs show widening of the physis and metaphyseal flaring. In Blount's disease, the characteristic radiographic changes involve only the tibia, and at this age, most commonly show beaking of the medial metaphysis. Skeletal dysplasias, such as chondrometaphyseal dysplasia, are associated with short stature, and the radiographic changes are similar to those seen here. However, laboratory studies in these children will be within normal limits. Children with chronic renal disease will often be of short stature, and the radiographic findings are again similar to those shown here. However, BUN and creatinine levels are elevated and phosphate levels are elevated rather than decreased in children with renal disease. The absence of dietary deficiencies and positive family history rules out vitamin D-deficient rickets. There are four types of vitamin D-resistant rickets: failure of production of 1,25-dihydroxy vitamin D, phosphate diabetes (hypophosphatemic rickets), end organ insensitivity to vitamin D, and renal tubular acidosis. All types of vitamin D-resistant rickets are resistant to treatment with physiologic doses of vitamin D. The patient's clinical picture, family history, laboratory studies, and radiographs are most consistent with hypophosphatemic rickets. This entity is inherited as a sex-linked dominant trait. Evans GA, Arulanantham K, Gage JR: Primary hypophosphatemic rickets: Effect of oral phosphate and vitamin D on growth and surgical treatment. J Bone Joint Surg Am 1980;62:1130-1138. Loeffler RD Jr, Sherman FC: The effect of treatment on growth and deformity in hypophosphatemic vitamin D-resistant rickets. Clin Orthop 1982;162:4-10. Loder RT, Johnston CE II: Infantile tibia vara. J Pediatr Orthop 1987;7:639-646.

The ulcer occurred as the result of a mismatch between the shape of the residual limb and the prosthetic socket. With the mismatch, the residual limb pistoned and the tissue failed because of the applied shear forces. The most predictable short- and long-term solution is reconstruction of the residual limb. Refraining from use of the prosthesis will prevent the patient from walking for months. It is unlikely that prosthetic socket modification will allow resolution of this large ulcer.

Cervical laminectomy is an accepted treatment for multilevel cervical spondylotic myelopathy. When the compression is posterior, laminectomy addresses it directly; when the compression is anterior, it is addressed indirectly (the spinal cord floats posteriorly away from the anterior compression). Preexisting kyphosis is a contraindication to laminectomy because the cord is unable to float posteriorly away from the anterior compression, and the risk for increasing kyphosis is significant. Kyphosis after laminectomy is more likely to develop in younger patients who have fewer degenerative changes to stabilize the spine. Malone DG, Benzyl EC: Laminotomy and laminectomy for spinal stenosis causing radiculopathy or myelopathy, in Clark CR (ed.): The Cervical Spine, ed 3. Philadelphia, PA, Lippincott Raven, 1998, pp 817-825.

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.

The patient has a calcaneonavicular tarsal coalition. Symptoms of calcaneonavicular coalitions typically are seen between the ages of 10 and 14 years. The cause of pain has not been clearly established. It has been postulated that the coalition stiffens with maturity and microfractures can result, producing pain. Resection of a calcaneonavicular coalition generally has been associated with a satisfactory result. Soft-tissue interposition, most commonly using the extensor digitorum brevis muscle, appears to be helpful. A hindfoot arthrodesis (usually triple) would be reserved if coalition resection proves to be unsuccessful. Achilles tendon lengthening and orthotic support, as well as debridement of the sinus tarsi, are not expected to result in a satisfactory outcome. The patient does not have a flatfoot deformity. Vaccaro AR (ed): Orthopaedic Knowledge Update 8. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 757-765.

The patient has symptoms of synovitis that are most likely the result of the release of particles from the tibial polyethylene. While observation may be warranted in a completely asymtomatic knee, some intervention is indicated for this patient as there is clear radiographic evidence of lysis in both the tibia and femur. The decision about the extent of the revision should be made at the time of surgery. A limited incision technique is not indicated. Grafting (or using graft substitute) the defect is the most appropriate approach for treating the osteolytic lesions. While a posterior stabilized prosthesis might be the solution, surgical findings might dictate otherwise.

The patient has degeneration of an adjacent segment with resultant kyphosis and stenosis. Because he is healthy, has responded well to previous surgery, and has a potentially correctable lesion, he is not a good candidate for an end-stage failed back procedure such as a morphine pump. The stenosis is exacerbated by the deformity; therefore, a simple decompression will contribute to instability. Because of the kyphosis and the patient's relatively young age, the treatment of choice is restoration of sagittal alignment and posterior decompression.

The radiographs show ankylosing spondylitis with sclerosis of the sacroiliac joints and a "bamboo spine" in the lumbar region. HLA-B27 is positive in 80% to 90% of patients with ankylosing spondylitis and in about 8% of the general population. The findings do not represent diffuse idiopathic skeletal hyperostosis (DISH), which is a radiographic diagnosis in which there are three consecutive levels of nonmarginated osteophytes without disk degeneration. Calin A: Ankylosing spondylitis. Clin Rheum Dis 1985;11:41-60. Booth R, Simpson J, Herkowitz H: Arthritis of the spine, in Herkowitz HH (ed): The Spine, ed 4. Philadelphia, PA, WB Saunders, 1992, p 431.

The dorsomedial cutaneous nerve of the hallux, which is a distal branch of the superficial peroneal nerve, supplies sensation to the skin on the dorsal and medial half of the hallux and may be injured during a chevron bunionectomy. Injury to the nerve leads to particularly painful neuromas that directly impinge on the shoe. For this reason, direct medial approaches are typically preferred for access to the medial aspect of the metatarsophalangeal joint.

The major risk of performing a high tibial osteotomy is neurovascular injury. The new version of the high tibial osteotomy makes a transverse osteotomy at the level of the tibial tubercle. The osteotome is protected by the oblique belly of the popliteus muscle. The popliteal artery and vein and tibial nerve all lie posterior to the muscle. The soleus muscle originates below this level. Clement CD: Anatomy: A Regional Atlas of Human Anatomy, ed 3. Baltimore, MD, Munich, Germany, Urban and Schwarzberg, 1987, Figure 422.

The plain radiographs reveal a pedunculated osteochondroma with a fracture. There is a bony growth in the metaphysis of a long bone, on a stalk that is directed away from the nearby epiphysis. On the AP view, the host cortical and medullary bone are shown as "blending" with lesional bone. There is also a fracture through the lesion. Based on these radiographic findings, the diagnosis is an osteochondroma; therefore, initial management of an acute fracture of an osteochondroma is symptomatic treatment alone. Additional imaging studies are not indicated in this patient. At times it may be difficult to distinguish a sessile osteochondroma from a parosteal osteosarcoma. In the latter case, the host medullary bone and lesion bone are not confluent. A CT scan may be helpful to distinguish if the host medullary and cortical bone are confluent with the lesion.

The epiphyseal location on the radiograph and MRI scan and the histologic findings of polyhedral cells separated by a chondroid matrix with pericellular, lattice-like "chicken wire" calcification all suggest chondroblastoma. Although giant cell tumors of bone typically occupy an epiphyseal location, they are rare in children and when present are often metaphyseal in skeletally immature patients. Enchondromas and osteoblastomas are generally metaphyseal and, along with giant cell tumors, have very different histology than seen here. Chondromyxoid fibromas are typically metaphyseal in location. Huvos AG: Bone Tumors: Diagnosis, Treatment, and Prognosis. Philadelphia, PA, WB Saunders, 1991, pp 295-313.

The patient has a posterior dislocation. The radiograph reveals marked internal rotation, but fails to show whether the humeral head is posteriorly displaced. Therefore, an axillary radiograph should be obtained to help confirm the diagnosis. Transverse view CT or MRI scans also may be useful. The other studies will not help confirm the diagnosis. In addition to a direct posterior blow, a shoulder dislocation may be caused by a seizure disorder or electrocution. Bloom MH, Obata WG: Diagnosis of posterior dislocation of the shoulder with the use of Velpeau axillary and angle-up roentgenographic views. J Bone Joint Surg Am 1967;49:943-949.

Glassman and associates reported a significantly higher pseudarthrosis rate when ketorolac was used postoperatively compared to a similar group of patients who were not given ketorolac. Animal studies from the same institution support these clinical findings. To reduce narcotic dosage, nonsteroidal anti-inflammatory drugs (NSAIDs) have been promoted as an adjunct for postoperative analgesia in patients undergoing spinal fusion. However, a high failure rate of arthrodesis has been associated with postoperative use of NSAIDs. The analgesics oxycodone hydrochloride, hydrocodone/acetaminophen, and tramadol, as well as the tricyclic antidepressant imipramine, have not been shown to inhibit fusion. Glassman SD, Rose SM, Dimar JR, et al: The effect of postoperative nonsteroidal anti-inflammatory drug administration on spinal fusion. Spine 1998;23:834-838.

Recently Harwood and associates investigated the principles of damage control orthopaedics (DCO) as they apply to patients with femoral shaft fractures. When they compared those who underwent initial external fixation of femoral shaft fractures with conversion to an intramedullary nail to those who underwent intramedullary nailing as their initial treatment, they found the following: overall infection rates were comparable in patients receiving DCO versus primary intramedullary fixation; open fracture was an independent risk factor for infection regardless of the treatment method; contamination rates in external fixator pin sites rose considerably when left in place more than 2 weeks and logistic regression analysis suggests that infection rates may increase when conversion to an intramedullary nail occurs after 2 weeks following external fixation; and there was no significant difference in time to union among treatment groups. Harwood PJ, Giannoudis PV, Probst C, et al: The risk of local infective complications after damage control procedures for femoral shaft fracture. J Orthop Trauma 2006;20:181-189.

Neurofibromatosis type 1 (NF-1) is an autosomal-dominant disorder affecting about 1 in 4,000 people. NF-1 causes tumors to grow along various types of nerves and affects the development of non-nervous tissues, such as bone and skin. The gene for NF-1 is located on the long arm of chromosome 17 and codes the protein neurofibromin. Research indicates that NF-1 acts as a tumor-suppressor gene and, as such, plays an important role in the control of cell growth and differentiation. Axillary and inguinal freckling is considered a good diagnostic marker for NF-1. The hyperpigmented spots that measure from 2 mm to 4 mm may be congenital, but these typically appear and increase later in life. Scoliosis is the most common musculoskeletal disorder of NF-1. The curves are frequently dystrophic, kyphotic, and have a high risk of pseudarthrosis following spinal fusion. Anterior and posterior spinal fusion with rigid posterior segmental instrumentation is the treatment of choice. Goldberg Y, Dibbern K, Klein J, Riccardi VM, Graham JM Jr: Neurofibromatosis type 1: An update and review for the primary pediatrician. Clin Pediatr 1996;35:545-561.

The wound described indicates loss of soft tissue directly to the level of the tendon, precluding use of skin grafts if excursion of the tendon is desired. A cross-finger flap is ideal for small wounds on the volar aspect of digits. A thenar flap is suitable for tip injuries. A lateral arm flap will not reach the fingers. A Moberg flap is limited to distal injuries of the thumb. Kappel DA, Burech JG: The cross-finger flap: An established reconstructive procedure. Hand Clin 1985;1:677-683.

Fractures of the hook of the hamate frequently are not identified in the acute phase. Because the fracture can be difficult to see on plain radiographs, the lack of findings can lead to a painful nonunion. A carpal tunnel view may show the fracture, but a CT scan will best detect the injury. Immobilization is the treatment of choice and will result in union in most patients unless the diagnosis is delayed. However, excision of the fragment may be necessary for patients who have nonunion, persistent pain, or ulnar nerve palsy. Carroll RE, Lakin JF: Fracture of the hook of the hamate: Acute treatment. J Trauma 1993;34:803-805.

The radiographs reveal a Monteggia injury, with a proximal ulnar shaft fracture and a radial head dislocation. Treatment involves open reduction and internal fixation of the ulnar fracture. With correct reduction of the ulna, the radial head is reducible and remains stable, despite an obvious soft-tissue injury around the elbow. Problems with persistent radial head subluxation are almost always attributed to malreduction of the ulnar fracture. Rare causes of persistent radial head subluxation are interposition of soft tissues in the joint and lateral ligamentous injuries. Jupiter JB, Kellam JF: Diaphyseal fractures of the forearm, in Browner B, Jupiter J, Levine A, Trafton P (eds): Skeletal Trauma, ed 2. Philadelphia, PA, WB Saunders, 1992, pp 1421-1454.

The knee is the most common location of spontaneous bleeding in children with hemophilia. Treatment generally requires replacement to 40% to 50% of normal. For surgery, the replacement should be to 100%. The plasma level generally rises 2% for every unit (per kg body weight) of factor VIII administered. Rodriquez-Merchan EC: Management of the orthopaedic complications of hemophilia. J Bone Joint Surg Br 1998;80:191-196.

Femoral neck fracture nonunion is a challenging problem for orthopaedic surgeons. Vertical fractures are more prone to nonunion due to shear stress rather than compressive forces across the fracture site. Several authors have suggested these fractures are more common in young adults due to injury type and bone composition. It is widely regarded that an effort should be made to salvage the femoral head if vascularity remains. The most common method to treat this complication is valgus intertrochanteric osteotomy of the femur. This functionally makes a vertical fracture more horizontal, converting shear into compressive forces. It also helps correct the varus position of the fracture nonunion. Hartford JM, Patel A, Powell J: Intertrochanteric osteotomy using a dynamic hip screw for femoral neck nonunion. J Orthop Trauma 2005;19:329-333.

A Weber type B ankle fracture occurs with a supination external rotation mechanism of injury. The fibula generally fails with a spiral fracture pattern. The lag screws provide compression, and the plate acts to neutralize rotational and angular bending forces. A buttress plate resists vertical shear forces. A tension band is used over areas that may fail in tension, such as an olecranon fracture. Compression is provided by the lag screws, and distraction is again resisted by the lag screws.

Instability is a leading cause of failure following total knee arthroplasty. Instability can present as global instability, extension gap (varus/valgus) instability, or flexion gap (anterior/posterior) instability. Treatment options are numerous based on the exact pathology. The radiograph reveals anterior/posterior instability with dislocation consistent with flexion gap instability. A loose flexion gap can allow the femoral component to ride above the tibial cam post mechanism, resulting in dislocation. Distal femoral augments treat extension gap instability, whereas tibial augments can treat both flexion and extension gap instability. Posterior condyle augments at the distal femur can also be used to treat flexion gap instability. Flexion gap instability is further aggravated by extension mechanism incompetence. Note the excessively thin patella on the lateral radiograph. Pagnano MW, Hanssen AD, Lewallen DG, et al: Flexion instability after primary cruciate retaining total knee arthroplasty. Clin Orthop 1998;356:39-46. McAuley J, Engh GA, Ammeen DJ: Treatment of the unstable total knee arthroplasty. Inst Course Lect 2004;53:237-241.

Any large (greater than 5 cm), deep, heterogeneous mass in the extremities should be considered a sarcoma until proven otherwise. Sarcomas are rare, and without a high index of suspicion, the lesions may be misdiagnosed or there may be a delay in diagnosis. Needle biopsies can obtain sufficient tissue for diagnosis and are associated with less morbidity than open biopsy. Marginal resections or excisional biopsies should be reserved for a few select benign lesions and locations. Damron TA, Beauchamp CP, Rougraff BT, et al: Soft-tissue lumps and bumps. Instr Course Lect 2004;53:625-637.

Injury to the latissimus dorsi tendon recently has been reported as a cause of pain in the thrower's shoulder. The etiology of this injury is felt to be eccentric overload during the follow-through of the throwing motion. Recommended management for this unusual injury consists of a short period of rest, followed by physical therapy to restore shoulder motion and strength. Throwing is allowed when the athlete demonstrates full, pain-free motion and good strength and balance of the rotator cuff and scapular rotator muscles. Currently there are no defined indications for surgical repair. Schickendantz MS, Ho CP, Keppler L, et al: MR imaging of the thrower's shoulder: Internal impingement, latissimus dorsi/subscapularis strains and related injuries. Magn Reson Imaging Clin N Am 1999;7:39-49.

Shufflebarger and others have reported that the placement of anterior interbody structural support at the lumbosacral junction increases the overall construct stiffness and reduces the strain on posterior instrumentation, thereby reducing the risk of screw pull-out or fracture. The stiffness of the posterior instrumentation actually increases, whereas the actual strength of the instrumentation remains the same. Actual strain measured at an adjacent intervertebral disk to a fusion construct is expected to increase. Shufflebarger HL: Moss-Miami spinal instrumentation system: Methods of fixation of the spondylopelvic junction, in Margulies JI, Floman Y, Farcy JPC, et al (eds): Lumbosacral and Spinal Pelvic Fixation. Philadelphia, PA, Lippincott-Raven, 1996, pp 381-393. Cunningham BW: A biomechanical approach to posterior spinal instrumentation: principles and applications, in DeWald RL (ed): Spinal Deformities: A Comprehensive Text. New York, NY, Thieme, 2003, pp 588-600.

The relocation test is most accurate when true apprehension is produced with the arm in combined abduction and external rotation and then relieved when posterior pressure is placed on the humeral head. Pain with this test is a less specific response and may occur with other shoulder disorders such as impingement.

The diagnosis of bone and joint sepsis in a newborn is difficult because of the relative lack of obvious signs and symptoms. Fever is usually absent. A study of 34 newborns with osteomyelitis identified prematurity and delivery by cesarean section as predisposing factors. In that study, the most common clinical findings were pseudoparalysis, local swelling, and pain on passive movement. Because early diagnosis is so important, any infant who exhibits these findings should be suspected as having bone or joint sepsis. Once the area of involvement is identified, aspiration is mandatory. In newborns who have an infection about the hip, radiographs may reveal subluxation. In this patient, septic arthritis must be ruled out by aspiration of the hip. Developmental dysplasia of the hip is not painful and is not accompanied by localized swelling. If no purulent material is obtained at the time of hip aspiration, an arthrogram should be obtained to rule out epiphysiolysis of the proximal femur. Because the area of involvement has been identified by clinical examination, a gallium scan or MRI scan of the spine is not indicated. Knudsen CJ, Hoffman EB: Neonatal osteomyelitis. J Bone Joint Surg Br 1990;72:846-851.

Naranja and associates reviewed 37 knees (35 patients, with 28 women and 7 men) without any motion that were converted to total knee arthroplasties. After an average follow-up of 90 months, the patients lacked an average of 7 degrees of extension and had 62 degrees of flexion. Results showed a short-term complication rate of 24% (stiffness requiring manipulation, delayed wound healing, and recurrent hemarthrosis), a major complication rate of 35% (patellar tendon or tibial tubercle avulsion, persistent pain requiring arthrodesis, loosening, and joint stiffness requiring arthrotomy for excision of scar tissue), and an infection rate of 14%. The total complication rate was 57%. A satisfactory outcome (no pain and an unlimited ambulation distance) was obtained in only 10 patients (29%). There was no relationship between results and the angle at which the knee was ankylosed preoperatively. This study revealed that although success in reconstructing a previously ankylosed or arthrodesed knee is possible, the lack of consistent adequate motion and the complication rate may suggest that the surgeon reconsider the risks and benefits of this difficult procedure.

Without stabilization, progressive kyphosis will develop between the spine and pelvis. The kyphosis progresses to the point that the child must use his or her hands to support the trunk, and therefore is unable to use his or her hands for other activities. Neck extension contracture does not usually develop. Neurologic deficit, including sexual dysfunction, is generally present at birth and static. Tachdjian MO: The spine: Congenital absence of the sacrum and lumbosacral vertebrae (lumbosacral agenesis), in Wickland EH Jr (ed): Pediatric Orthopaedics, ed 2. Philadelphia, PA, WB Saunders, 1990, vol 3, p 2228.

Following a CVA and with the resumption of upright posture, downward subluxation of the glenohumeral joint may occur. Although usually painless, some patients may report pain secondary to stretching of the brachial plexus. This is the result of flaccid paralysis of the deltoid muscle, and it will persist until some motor tone or spasticity returns to the shoulder girdle musculature. Early sling support and range-of-motion exercises to prevent contracture will provide the best relief. Surgical procedures are not indicated. Braun RM, Botte MJ: Treatment of shoulder deformity in acquired spasticity. Clin Orthop 1999;368:54-65.

The patient has a dynamic varus deformity secondary to spasticity of the tibialis anterior during stance phase with inverter/everter imbalance. The patient still has active motion of the tibialis anterior; therefore, an out-of-phase posterior tibial tendon transfer should not be performed. The same is true of the Bridle procedure. Transfer of the posterior tibialis in this patient may also result in subsequent planovalgus deformity. Lengthening of the Achilles tendon through a percutaneous tenotomy will restore dorsiflexion and decrease clonus from the stretch response. If adequate dorsiflexion is not obtained intraoperatively, then posterior tibialis tendon lengthening may be considered. A split tibialis anterior tendon transfer to the lateral cuneiform, or, transfer of the entire tendon to the cuneiform should correct the varus component and compensate for the weakened peroneals. Yamamoto H, Okumura S, Morita S, et al: Surgical correction of foot deformities after stroke. Clin Orthop Relat Res 1992;282:213-218. Piazza SJ, Adamson RL, Moran MF, et al: Effects on tensioning errors in split transfers of tibialis anterior and posterior tendons. J Bone Joint Surg Am 2003;85:858-865.

The most common inherited neuromuscular disease seen by orthopaedic surgeons is CMT, which is an inherited autosomal-dominant disease. It is more commonly seen in men due to the nature of the inheritance. Identification of cavus deformity in the foot of a child should arouse suspicion. Richardson EG (ed): Orthopaedic Knowledge Update: Foot and Ankle 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 135-143. Charcot-Marie-Tooth Disease (CMT) Penn State Hershey Medical Center. www.hmc.psu.edu/healthinfo/c/cmt.htm

As long as the patient is alert and cooperative, an attempt can be made to reduce the dislocation. This should not be attempted in a patient who is obtunded, comatose, or uncooperative. If any neurologic changes are noted during the reduction maneuver, the attempt should be stopped, appropriate radiographic studies obtained, and open reduction and stabilization planned in the operating room.

The lateral cord terminates as the musculocutaneous nerve and also contributes sensory fibers to the median nerve. Involvement of the C6 root or upper trunk could potentially cause weakness of the infraspinatus and the brachioradialis. The middle trunk and the posterior cord do not contribute motor fibers to the thumb or sensory fibers to the thumb.

The saphenous nerve follows the saphenous vein, giving off the infrapatellar branch that crosses the knee anteriorly to supply the peripatellar skin. A longitudinal incision can interrupt the nerve, leaving the terminal distribution without sensation.

Penetrating sharp wounds in proximity to major nerve or vascular structures should always be acutely explored. Because this patient did not seek treatment for a potentially treatable injury, interosseous wasting implies injury to the C8 and T1 nerve roots that contribute to ulnar nerve function. The most likely location for the brachial plexus injury is the location marked L or the inferior trunk. A wrist drop that is the result of radial nerve dysfunction would be expected with an injury at K or O. An upper brachial plexus palsy with loss of elbow flexion and shoulder abduction would be expected with an injury at B. A loss of elbow flexion alone would be expected following an injury at C. 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, pp 28-29. Wolock B, Millesi H: Brachial plexus-applied anatomy and operative exposure, in Gelberman RH (ed): Operative Nerve Repair and Reconstruction. Philadelphia, PA, JB Lippincott, 1991, vol 2, pp 1255-1272.

Paget's disease of bone is a metabolic disorder of bone remodeling. The normally coupled process of bone resorption and deposition is lost, resulting in excessive localized bone resorption and compensatory increased bone formation. Pagetic bone tends to be more brittle; therefore, it is susceptible to pathologic fractures and subsequent deformities. Lander PH, Hadjipavlou AG: A dynamic classification of Paget's disease. J Bone Joint Surg Br 1986;68:431-438.

Localized PVNS is a form of the disease in which synovial proliferation is restricted to one area of a joint and causes the formation of a small mass-like lesion. The true incidence of this is unknown but is probably less common than the diffuse form of the disease. PVNS presents as a usually painful discrete mass. The anterior compartment of the knee is the most common location. Tyler WK, Vidal AF, Williams RJ, et al: Pigmented villonodular synovitis. J Am Acad Orthop Surg 2006;14:376-385.

A total hip arthroplasty using the posterior approach has resulted in hip dislocation under certain circumstances. Reconstruction of the external rotator/capsular complex is recognized as a stability-enhancing mechanism for the posterior approach. During the procedure, the acetabular component should be placed in 15 to 20 degrees of anteversion and approximately 45 degrees of abduction. Relative retroversion is a risk factor for posterior dislocation. High abduction angles result in edge loading of the polyethylene and possible early failure, as well as an increased risk of dislocation. Smaller diameter heads and skirted neck extensions used together decrease the range of motion that is allowed before impingement occurs, and this can result in dislocation. Shorter neck lengths generally result in soft-tissue envelope laxity. If laxity occurs, increased offset, neck length, or both can improve stability. Pellicci PM, Bostrom M, Poss R: Posterior approach to total hip replacement using enhanced posterior soft tissue repair. Clin Orthop 1998;355:224-228.

The optimal conditions for bony ingrowth include a pore size of 100 to 400 um, interface micromotion of 50 um or less, intimate contact between the bone and the implant, circumferential porous coating of the implant, and use of a biocompatible material. Stem designs with patch coatings have a poor record of bony ingrowth, especially in the revision setting. Failure of ingrowth in the previous stem would be the result of its own mechanical milieu and would not necessarily predict results for the new stem. Berry DJ, Harmsen WS, Ilstrup D, Lewallen DG, Cabanela ME: Survivorship of uncemented proximally porous-coated femoral components. Clin Orthop 1995;319:168-177. Cook SD, Thomas KA, Haddad RJ Jr: Histologic analysis of retrieved human porous-coated total joint components. Clin Orthop 1988;234:90-101.

There is no identifiable thoracic, abdominal, or long bone source of ongoing bleeding. The patient has a lateral compression Burgess-Young type I pelvic ring injury. This injury does not increase the pelvic volume because it is not unstable in external rotation. Application of a PASG, a pelvic clamp, or an external fixator may be helpful if the patient has a pelvic injury that is unstable in external rotation or translation but would be of little use in this injury pattern. Persistent hemodynamic instability after administration of 4 units of blood is the decision point where most authors would recommend angiography and embolization. If the pelvis is unstable in external rotation or translation, inflation of the PASG trousers or application of an external fixator is recommended before angiography. Attributing the hemodynamic instability to the head injury before ruling out the pelvis as a source is not indicated. Burgess AR, Eastridge BJ, Young JW, et al: Pelvic ring disruptions: Effective classification system and treatment protocols. J Trauma 1990;30:848-856. Evers BM, Cryer HM, Miller FB: Pelvic fracture hemorrhage: Priorities in management. Arch Surg 1989;124:422-424.

The radiograph shows calcific deposits within the substance of the supraspinatus tendon. Patients with this condition are prone to recurrent bouts of acute inflammation in the shoulder. While the response to cortisone injection is often dramatic, repeated injections are not recommended because of injury to the collagen fibers. Good results have been obtained with arthroscopic evacuation of the calcium deposits. In one study, the addition of a subacromial decompression did not improve the results. Jerosch J, Strauss JM, Schmiel S: Arthroscopic treatment of calcific tendinitis of the shoulder. J Shoulder Elbow Surg 1998;7:30-37.