100 Orthopedic MCQs: Basic Science, Trauma, Spine & Arthroplasty | Comprehensive ABOS Board Review

Tuberculosis of the spine is seen in 50% to 60% of skeletal disease and is most commonly found in the lower thoracic or upper lumbar spine. Typically two or more adjacent bodies are involved as seen in this MRI scan. The disk space is narrowed but still relatively preserved as opposed to pyogenic infections (black arrow). Epidural extensions often spread from vertebrae to vertebrae (white arrow); however, the posterior elements are not frequently involved (arrowhead). Tumors rarely spread to adjacent vertebrae. The anterior and posterior spread of the infectious process rules out trauma. Boachie-Adjei O, Squillante RG: Tuberculosis of the spine. Orthop Clin North Am 1996;27:95-103.

The radiograph shows a pathologic fracture through a destructive lesion of the distal femur metaphysis with osteolytic and osteoblastic features. The lateral cortex is destroyed, and there is periosteal new bone formation. These findings are consistent with malignancy, most likely an osteogenic sarcoma. Patients with suspected malignant tumors are best managed by surgeons with specific expertise in orthopaedic oncology. The biopsy of a malignant lesion should be deferred to the surgeon who is capable of definitive management of the patient. Enneking W: Principles of musculoskeletal oncologic surgery, in Evarts C (ed): Surgery of the Musculoskeletal System. New York, NY, Churchill Livingston, 1990.

Studies on older systems, as well as newer designs, have confirmed that metal-on-metal bearing surfaces undergo linear wear of 2 to 5 um per year. Ceramic bearing surfaces produced with recent technology perform even better, with a wear rate of 0.5 to 2.5 um per year. Clinical wear rates of metal-on-crosslinked polyethylene have not yet been determined. McKellop H, Park SH, Chiesa R, et al: In vivo wear of three types of metal on metal hip prostheses during two decades of use. Clin Orthop 1996;329:S128-S140.

The patient's history and physical examination findings are consistent with a lumbar disk herniation at the L4-5 level. Weakness of the extensor hallucis longus and gluteus medius are consistent with an L5 lumbar radiculopathy. Nerve root tension signs are also consistent with sciatica from a lumbar disk herniation. The MRI scans confirm a posterolateral disk herniation at L4-5, which typically affects the exiting L5 nerve root. Hoppenfeld S: Orthopedic Neurology. Philadelphia, PA, JB Lippincott, 1977, pp 45-74.

Even though the patient has a grade 3 ankle ligament injury, studies have shown that 95% of patients with a grade 3 injury that may include a complete tear of the ligaments will heal successfully with conservative functional management. Extensive diagnostic evaluation with stress radiographs, CT, and MRI is not indicated. Surgical reconstruction is not indicated because of the overwhelming success of conservative management; however, in the few patients where late instability develops, surgical reconstruction offers an excellent outcome. Carne P: Nonsurgical treatment of ankle sprains using the modified Sarmiento brace. Am J Sports Med 1989;17:253-257.

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.

The major criteria for the diagnosis of fat embolism syndrome include hypoxemia (PaO2 of less than 60 mm Hg), central nervous system depression, and a petechial rash that is most often located in the axillae, conjunctivae, and palate. The rash is often transient. Tachycardia, pyrexia, anemia, thrombocytopenia, and the presence of fat in the urine are all considered minor criteria. To establish the diagnosis of fat embolism syndrome, one major and four minor signs should be present. Pulmonary embolism, which is the major differential diagnosis, usually is not associated with conjunctival petechia or thrombocytopenia.

Risk factors can suggest the existence of osteoporosis. However, definitive testing, based on the use of bone densitometry measurements, uses the T score in which an average score is taken from a normal population of young women. The presence of increased osteoid in lamellar bone is seen in osteomalacia but not osteoporosis. The presence of fractures is evidence of a risk factor for osteoporosis and can predict future fractures, but it does not definitively confirm the diagnosis. The Singh index is a radiographic finding that is not as accurate as bone mineral density scores.

The superior ulnar collateral, inferior ulnar collateral, and posterior ulnar recurrent arteries provide consistent vascular supply to the ulnar nerve. This supply is segmental in nature. No identifiable direct anastomosis is seen between the superior ulnar collateral and the posterior ulnar recurrent arteries. The inferior ulnar collateral artery provides the only direct vascularization to the nerve and is located in the region just proximal to the cubital tunnel. The segmental nature of the blood supply to the ulnar nerve underscores the importance of its preservation during transposition.

Approximately 65% of cervical subluxations occur at C1-C2. Of these, 50% are anterior, with the remainder being lateral and posterior. The second most common type is basilar invagination, occurring in 40% of patients. The third most common type is subaxial, occurring in 20% of patients with rheumatoid arthritis. Subluxation at more than one level is common. Boden S, Clark CR: Rheumatoid arthritis of the cervical spine, in Clark CR (ed): The Cervical Spine, ed 3. Philadelphia, PA, Lippincott Raven, 1998, p 693. Boden SD, Dodge LD, Bohlman HH, Rechtine GR: Rheumatoid arthritis of the cervical spine: A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am 1993;75:1282-1297.

Ewing's sarcoma has an 11;22 translocation that creates the EWS/FLI1 fusion gene, and synovial sarcoma has an X;18 translocation that creates the STT/SSX fusion gene. The other tumors do not have consistent translocations. Sandberg AA: Cytogenetics and molecular genetics of bone and soft-tissue tumors. Am J Med Genet 2002;115:189-193.

The radiographs show a displaced ankle fracture with widening of the syndesmosis. Open reduction and internal fixation is indicated with fixation of the mortise with syndesmotic screws. Wuest TK: Injuries to the distal lower extremity syndesmosis. J Am Acad Orthop Surg 1997;5:172-181.

Unwitnessed spiral fractures should raise the possibility of child abuse, especially prior to walking age. With nonaccidental trauma being considered in the differential diagnosis, a skeletal survey is indicated to determine if there are other fractures in various stages of healing. Kempe CH, Silverman FN, Steele BF, et al: The battered-child syndrome. JAMA 1962;181:17-24.

The MRI scans show a mesoacromion with tendonopathy of the supraspinatus. The history and physical findings indicate that the patient has a symptomatic os acromiale. Simple excision of the unstable os acromiale has not yielded consistently good results. Meticulous internal fixation using tension banding with cannulated screws and autologous bone grafting has shown good results for this problem. Hutchinson MR, Veenstra MA: Arthroscopic decompression of shoulder impingement secondary to os acromiale. Arthroscopy 1993;9:28-32.

The patient has not undergone a trial of foot-specific patient education and accommodative/therapeutic shoe wear. He must use therapeutic shoe wear at all times, as even the occasional use of pressure-concentrating shoe wear has a high likelihood of leading to the development of a diabetic foot ulcer. Pinzur MS, Kernan-Schroeder D, Emmanuele NV, et al: Development of a nurse-provided health system strategy for diabetic foot care. Foot Ank Int 2001;22:744-746. Pinzur MS, Shields N, Goelitz B, et al: American Orthopaedic Foot & Ankle Society shoe survey of diabetic patients. Foot & Ankle Int 1999;20:703-707.

Neurilemoma is a benign tumor of nerve sheath origin, and peak incidence is in the third through sixth decades. The tumor is well encapsulated on the surface of a peripheral nerve. MRI findings may be significant for a "string sign." A positive Tinel's sign in the distribution of the nerve affected may be present. Grossly, the lesion is well encapsulated in a nerve sheath. Microscopically, there are structures referred to as Antoni A (a pattern of spindle cells arranged in intersecting bundles) and Antoni B (areas with less cellularity with loosely arranged cells). These lesions are benign, and treatment should consist of marginal excision. Nerve function may be preserved by careful dissection, excising the lesion parallel to the nerve fascicles so the lesion may be extruded. Recurrence is rare. Walling AK: Soft tissue and bone tumors, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, pp 1007-1032.

Proper hydration prior to an athletic event is the most important determinant of performance. It is virtually impossible to keep pace with fluid loss during an athletic competition. When a net loss of fluid occurs and the athlete is properly prehydrated, this fluid loss will not adversely affect performance. It is not necessary to load up on carbohydrates prior to a 10K race, or to replace calories burned during the race. Hyponatremia can develop in ultra-endurance athletes, especially marathoners, if they hydrate without replacing electrolytes lost through sweating; however, this is highly unlikely for a 10K race. Newmark SR, Toppo FR, Adams G: Fluid and electrolyte replacement in the ultramarathon runner. Am J Sports Med 1991;19:389-391.

The rotator cuff interval consists of the superior glenohumeral and coracohumeral ligaments. Injury to this ligament complex leads to posteroinferior shoulder instability. Tightening of these tissues through surgical means has been shown to result in a significant reduction in posteroinferior translation of the humerus in relation to the glenoid. Harryman DT II, Sidles JA, Harris SL, et al: The role of the rotator interval capsule in passive motion and stability of the shoulder. J Bone Joint Surg Am 1992;74:53-66. O'Brien SJ, Schwartz RS, Warren RF, et al: Capsular restraints to anterior-posterior motion of the abducted shoulder: A biomechanical study. J Shoulder Elbow Surg 1995;4:298-308.

The patient has a ligamentous Lisfranc injury. Diastasis seen between the bases of the second metatarsal and medial cuneiform is pathognomonic for a rupture of the Lisfranc's ligament. This injury is best treated surgically with either open reduction and internal fixation or possibly closed manipulation and percutaneous screw fixation if anatomic alignment can be achieved closed. Pin fixation has been shown to be inferior to screw fixation due to the length of time that fixation is required for adequate ligament healing. Chiodo CP, Myerson MS: Developments and advances in the diagnosis and treatment of injuries of the tarsometatarsal joint. Orthop Clin North Am 2001;32:11-20.

The traditional treatment of a reduced type II fracture is a halo vest. A 20-year-old man will tolerate a halo vest better than the elderly or women. Anterior screw fixation has gained increasing support; however, it too has risks and requires a significant learning curve. More recently, C1 lateral mass screws have become more popular. The long-term results and benefits have not yet been determined. Spivak JM, Connolly PF (eds): Orthopaedic Knowledge Update: Spine 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, p 193. Kiovikko MP, Kiuru MJ, Koskinen SK, et al: Factors associated with nonunion in conservatively-treated type-II fractures of the odontoid process. J Bone Joint Surg Br 2004;86:1146-1151. Herkowitz HN, Garfin SR, Eismont FJ: Rothman-Simone The Spine, ed 5. Philadelphia, PA, Saunders Elsevier, 2006, p 1091.

The radiograph reveals a periprosthetic fracture at the tip of the stem with a stable cemented implant. This is classified as a Vancouver type B1 periprosthetic fracture. An attempt at internal fixation has already failed; therefore, the most predictable results would be achieved with distal fixation. After removal of the well-fixed cemented implant, the proximal bone may not be suitable for proximal fixation. Adequate bone stock is available such that an allograft prosthetic composite or a tumor prosthesis is not necessary. The best option is a long stem implant with distal fixation, which serves as an intramedullary device to restore alignment and increase the likelihood of union. Cortical onlay strut grafts are used as an adjunct to definitive fixation. Younger AS, Dunwoody I, Duncan CP: Periprosthetic hip and knee fractures: The scope of the problem. Inst Course Lect 1998;47:251-256.

The MRI scan shows a massive tear of the supraspinatus tendon with medial retraction to the level of the glenoid. This is most likely an attritional tear with a high risk of failure of the repair. The preferred treatment is nonsurgical management for pain and stiffness. Acromioplasty and coracoacromial ligament release in this setting are controversial, as they can result in the devastating complication of anterosuperior subluxation of the humerus. Rockwood CA Jr, Williams GR Jr, Burkhead WZ Jr: Debridement of degenerative, irreparable lesions of the rotator cuff. J Bone Joint Surg Am 1995;77:857-866.

The patient has an oligotrophic nonunion of the distal femoral fracture. Although the proximal fracture appears incompletely united, it was stable at exchange nailing. The treatment of choice is exchange reamed nailing to at least 2 mm above the nail in place. Bone grafting is debatable. Recent studies have shown a 70% to 75% success rate with exchange nailing only, so in nonhypertrophic nonunions, bone grafting can be considered. Nonsurgical management consisting of observation or external stimulation runs the risk of implant failure. Plate fixation is acceptable but is considered a second choice because of the need to consider stabilization of the proximal fracture until union is achieved. Also, plate fixation definitely requires bone grafting. Webb LX, Winquist RA, Hansen ST: Intramedullary nailing and reaming for delayed union or nonunion of the femoral shaft: A report of 105 consecutive cases. Clin Orthop 1986;212:133-141. Weresh MJ, Hakanson R, Stover MD, et al: Failure of exchange reamed intramedullary nailing for ununited femoral shaft fractures. J Orthop Trauma 2000;14:335-338.

Improved medical management has changed musculoskeletal outcomes for individuals with hemophilia. Patients with severe hemophilia receiving prophylactic administration of factor VIII may never develop a target joint that requires further orthopaedic intervention. Patients with moderate hemophilia and those patients with severe hemophilia not receiving prophylactic treatment will still develop joints that have recurrent hemarthroses. When recurrent hemarthrosis continues despite optimal medical management, synovectomy is indicated. While synovectomy is predictable in its ability to decrease joint bleeding, it does not necessarily improve joint range of motion or prevent the development of hemophilic arthropathy over time. It will not reverse articular damage to the joint once it has developed. Dunn AL, Busch MT, Wyly JB; et al: Arthroscopic synovectomy for hemophilic joint disease in a pediatric population. J Pediatr Orthop 2004;24:414-426.

Fractures with a posterior wall fragment that makes up less than one third of the surface generally are stable. Conversely, fractures with a fragment making up more than 50% of the surface are unstable. Patients with an intermediate fracture fragment should undergo a fluoroscopic examination under sedation or anesthesia to determine if the fragment is truly stable. If so, the patient can be treated nonoperatively and safely mobilized. Tornetta P III: Non-operative management of acetabular fractures: The use of dynamic stress views. J Bone Joint Surg Br 1999;81:67-70.

The incidence of injury associated with horseback rising is estimated to be one per 350 riding hours to one per 1,000 riding hours. Of these injuries, approximately 15% to 27% are severe enough to warrant hospital admission. Significant and serious injuries in equestrian activities are associated with recreational riders and those not wearing a helmet. Head and spine injuries are more common in recreational and nonhelmeted riders. Extremity injuries are more common in professional and helmeted riders. Professional riders are less likely to be admitted to the hospital than recreational riders, and are about half as likely to be disabled at 6 months after injury as recreational riders. Lim J, Puttaswamy V, Gizzi M, et al: Pattern of equestrian injuries presenting to a Sydney teaching hospital. ANZ J Surg 2003;73:567-571.

The radiograph reveals that the femoral component is grossly loose as evidenced by disruption of the cement column; therefore, retention of the original components will not yield a successful outcome. A cementless revision is the procedure of choice. A strut graft and/or plate may be added at the surgeon's discretion. A resection arthroplasty would only be considered in a nonambulatory patient. Cemented fixation of the revision component would be problematic given the numerous fracture fragments and the inability to contain the cement. Springer BD, Berry DJ, Lewallen DG: Treatment of periprosthetic fractures following total hip arthroplasty with femoral component revision. J Bone Joint Surg Am 2003;85:2156-2162.

The radiographs show classic hinge abduction. The diagnostic feature is the failure of the lateral epiphysis to slide under the acetabular edge with abduction, and the abduction view shows medial dye pooling because of distraction of the hip joint. Persistent hinge abduction has been shown to prevent femoral head remodeling by the acetabulum. Radiographic changes are characteristic of severe involvement with Legg-Calve-Perthes disease.The Catterall classification cannot be well applied without a lateral radiograph, but this degree of involvement would likely be considered a grade III or IV. Because the lateral pillar is involved, this condition would be classified as type C using the Herring lateral pillar classification scheme.

The fracture pattern shown in the radiographs is a fracture of the posterior column. The only line interrupted on the AP pelvis is the ilioischial line. The obturator oblique view shows that the iliopectineal line is intact as is the outline of the posterior wall. The iliac oblique view shows an interruption of the ilioischial line and an intact anterior wall. Therefore, this fracture is a fracture of the posterior column. Letournel E, Judet R: Fractures of the Acetabulum, ed 2. Berlin, Germany, Springer Verlag, 1993.

The child sustained a brachial plexus injury at birth, and internal rotation/adduction contractures frequently develop at the shoulder. Initial treatment should consist of physical therapy to increase the range of motion. If this fails, as in this patient, MRI is used to evaluate the glenohumeral joint. Commonly, there is joint deformity with increased retroversion of the glenoid and even posterior shoulder subluxation. If the deformity is mild, an anterior release, coupled with teres major and latissimus transfers, is very effective. If the deformity is severe and the shoulder is unreconstructable, then humeral derotation osteotomy is the procedure of choice. MRI of the brain, a radiograph of the elbow, and aspiration of the shoulder would not be helpful. Waters PM: Update on management of pediatric brachial plexus palsy. J Pediatr Orthop B 2005;14:233-244. Waters PM, Bae DS: Effect of tendon transfers and extra-articular soft-tissue balancing on glenohumeral development in brachial plexus birth palsy. J Bone Joint Surg Am 2005;87:320-325.

The patient has a both-bone fracture with a comminuted radial shaft. Open reduction and internal fixation of both bones is the treatment of choice. In the past, Chapman and associates recommended bone grafting radial shaft fractures with more than 30% comminution of the circumference. This has remained the recommendation in most textbooks. More recent studies, where modern biologic plating techniques were used, found that the addition of bone graft to comminuted fractures was not necessary because the union rate did not differ from that of nongrafted comminuted fractures. Anderson LD, Sisk TD, Tooms RE, Park WI III: Compression-plate fixation in acute diaphyseal fractures of the radius and ulna. J Bone Joint Surg Am 1975;57:287-297. Chapman MW, Gordon JE, Zissimos AG: Compression-plate fixation of acute fractures of the diaphyses of the radius and ulna. J Bone Joint Surg Am 1989;71:159-169. Wright RR, Schmeling GJ, Schwab JP: The necessity of acute bone grafting in diaphyseal forearm fractures: A retrospective review. J Orthop Trauma 1997;11:288-294.

Pelvic osteotomies that redirect hyaline cartilage over the femoral head offer the potential for long-term preservation of the hip; however, salvage procedures such as the Chiari osteotomy are indicated in patients without a concentrically reducible hip. Ito and associates reported that moderate dysplasia and moderate subluxation without complete obliteration of the joint space and a preoperative center-edge angle of at least minus 10 degrees are desirable selection criteria. Ohashi H, Hirohashi K, Yamano Y: Factors influencing the outcome of Chiari pelvic osteotomy: A long-term follow-up. J Bone Joint Surg Br 2000;82:517-525.

C-reactive protein declines rapidly as the clinical picture improves. Failure of the C-reactive protein to decline after 48 to 72 hours of treatment should indicate that treatment may need to be altered. Blood culture is positive only 50% of the time and will be negative soon after antibiotics are administered, even if treatment is not progressing satisfactorily. WBC count is highly variable and poorly correlated with treatment. The ESR rises rapidly but declines too slowly to guide treatment. Radiographic findings may not change but can take up to 2 weeks to show changes.

The severe depression of the proximal medial tibial epiphysis is most consistent with the diagnosis of neglected infantile Blount's disease. Blount's disease in adolescents produces a deformity in the metaphyseal region. Septic arthritis and JRA affect both sides of the joint. Hemophilia produces a characteristic widening of the intercondylar notch. Thompson GH, Carter JR: Late-onset tibia vara (Blount's Disease). Clin Orthop 1990;255:24-35.

The radiograph shows a displaced calcaneal beak fracture, a tongue-type fracture variant. The fracture fragment typically includes the insertion point of the Achilles tendon, which places marked tension on the thin overlying soft-tissue envelope and can lead to full-thickness necrosis if not acutely addressed. Cast immobilization does not adequately address the increased soft-tissue tension, as the fragment will be difficult to control. Arthroscopic-assisted techniques or primary arthrodesis are not indicated because calcaneal beak fractures are typically extra-articular. Sanders RW, Clare MP: Fractures of the calcaneus, in Coughlin MJ, Mann RA, Saltzman CL (eds): Surgery of the Foot and Ankle, ed 8. Philadelphia, PA, Mosby-Elsevier, 2007, vol 2, pp 2017-2073.

The radiograph shows a benign-appearing cortically based lesion eroding the underlying cortex, producing a saucer-shaped defect typical of a periosteal chondroma. The histology shows benign-appearing neoplastic cartilage. Although enchondroma would have the same histologic appearance, radiographs generally show a lesion with a central medullary epicenter. The benign-appearing histology does not support chondrosarcoma. Chondromyxoid fibroma will generally show histologic elements of its fibrous and myxoid components. Chondroblastoma typically demonstrates histologic findings of polyhedral cells separated by a chondroid matrix with pericellular, lattice-like "chicken wire" calcification. Schajowicz F: Tumors and Tumorlike Lesions of Bone: Pathology, Radiology, and Treatment, ed 2. Berlin, Springer-Verlag, 1994, pp 147-151.

Polyethylene wear debris can result in significant synovitis and subsequent cloudy appearing synovial fluid. Typically, laboratory studies show a WBC of less than 30,000/mm3 no left shift. Cytologic examination can reveal intra-articular polyethylene particles. Infected total knee arthroplasty is extremely uncommon in a healthy, immune-competent patient who has a normal preoperative erythrocyte sedimentation rate and C-reactive protein level.

At the ankle level, the anterior tibial artery lies medial to the EHL tendon. The artery becomes the dorsalis pedis after crossing onto the dorsum of the foot. At this point, the artery lies lateral to the tendon. Resch S: Functional anatomy and topography of the foot and ankle, in Myerson M (ed): Foot and Ankle Disorders. Philadelphia, PA, WB Saunders, 2000, vol 1, pp 25-49.

Minimally displaced fractures of the proximal humerus have a good outcome if physical therapy is initiated within 2 weeks of the injury. Results are not affected by age, open reduction and internal fixation, or involvement of the greater tuberosity. Immobilization for longer than 3 weeks will often result in stiffness. Koval KJ, Gallagher MA, Marsicano JG, et al: Functional outcome after minimally displaced fractures of the proximal part of the humerus. J Bone Joint Surg Am 1997;79:203-207.

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.

This patient appears to have adequate blood supply to heal a Syme's ankle disarticulation but is currently malnourished because of the systemic infection, and is likely to progress to wound failure. Therefore, the initial management of choice is culture-specific antibiotic therapy, open wound management, and nutritional supplementation. If his serum albumin rises to a minimum of 2.5 gm/dL, he can undergo elective Syme's ankle disarticulation. If the serum albumin does not rise within a short period of time, he should undergo transtibial amputation.

This is the first occurrence of diabetic foot-specific morbidity. The patient has a foot deformity, a history of a diabetic foot ulcer, and is insensate to the monofilament. He is at moderate risk for the development of a recurrent ulcer. This is best avoided with therapeutic footwear. Commercially available depth-inlay shoes should be combined with a custom accommodative foot orthosis to accommodative the deformity. Pinzur MS, Slovenkai MP, Trepman E, et al: Guidelines for diabetic foot care: Recommendations endorsed by the Diabetes Committee of the American Orthopaedic Foot and Ankle Society. Foot Ankle Int 2005;26:113-119.

The radiograph shows hardware that was used for fixation of a prior femoral fracture. The mechanical axis of the lower extremity in this patient is nearly normal (3 degrees valgus), and the deformity at the healed fracture site (14 degrees) does not appear to affect the joint alignment and is acceptable. Use of a routine knee prosthesis will be possible in this patient. To avoid hardware removal, extramedullary jigs and/or computerized navigation may be used to measure and restore the long axis of the femur. The use of a hinged prosthesis does not influence the mechanical axis directly. Extra-articular osteotomy is occasionally needed to reverse severe deformities. Papadopoulos EC, Parvizi J, Lai CH, et al: Total knee arthroplasty following distal femoral fractures. Knee 2002;9:267-274.

The patient sustained a bimalleolar ankle fracture with a syndesmosis disruption. The initial open reduction and internal fixation did not successfully reduce the distal tibiofibular joint. The patient may need a derotational distraction osteotomy of the fibula to reduce the syndesmosis. The other procedures do not address the primary problem of the fibular malunion and syndesmosis malreduction. There is no radiographic evidence of significant arthritis; therefore, ankle arthrodesis is not indicated.

The semitendinosus and gracilis tendons lie beneath the superficial fascia and superficial to the medial collateral ligament. The semitendinosus is located more inferior to the gracilis tendon. The sartorius is more posterior and distal as is the medial collateral ligament. The semimembranosus is posterior. Pagnani MJ, Warner JJ, O'Brien SJ, Warren RF: Anatomic considerations in harvesting the semitendinosus and gracilis tendons and a technique of harvest. Am J Sports Med 1993;21:565-571.

In general, soft-tissue metastases to regional nodes are a relatively rare occurrence (less than 5% overall). The incidence of lymphatic metastasis is highest for synovial sarcoma, rhabdomyosarcoma, clear cell sarcoma, and epithelioid sarcoma. Regional nodes should be assessed clinically. CT is not used to routinely assess regional nodes. Evaluation of a sentinal node is not indicated because of the low incidence of regional nodal involvement. Fine needle aspiration may be indicated to assess clinically suspicious nodes. Prophylactic inguinal node dissection is contraindicated because it may lead to unnecessary complications such as lymphedema.

From proximal to distal, the brachial plexus is divided into roots, trunks, divisions, and cords before forming specific peripheral nerve branches. The structure marked Q is called the posterior cord because it lies posterior to the axially artery at the level of the cords. Its terminal branches are the upper subscapular (V), thoracodorsal (W), lower subscapular (X), axillary (F), and radial (G) nerves. Anderson JE (ed): Grant's Atlas of Anatomy, ed 7. Baltimore, MD, Williams and Wilkins, 1978, pp 6-24.

Curettage and bone grafting typically is the preferred method of treatment for chondroblastoma, with local recurrence rates of approximately 10%. Some clinicians advocate the addition of adjuvants such as phenol. Left alone, these lesions can destroy bone and invade the joint. Large intra-articular lesions may require major joint reconstruction. Wide local excision rarely is required to eradicate the tumor. Radiation therapy rarely is indicated and only for unresectable or multiply recurrent lesions. Springfield DS, Capanna R, Gherlinzoni F, Picci P, Campanacci M: Chondroblastoma: A review of seventy cases. J Bone Joint Surg Am 1985;67:748-755.

Children with hypothyroidism have delayed bone age, reduced thickness of the physis, disorganization of the cartilage columns of the physis, and impaired differentiation of proliferating chondrocytes into hypertrophic cells. As a result, these children have severe growth retardation, and slipped capital femoral epiphysis may develop because of mechanical weakening of the physis. Thyroid hormone regulates terminal differentiation of the growth plate chondrocytes, with a resultant increase in type X collagen and alkaline phosphatase. These substances are important factors in matrix mineralization. Insulin-like growth factors and FGF-2 appear to act synergistically to stimulate mitotic activity of the growth plate chondrocytes. TGF-beta= and PTHrP stimulate proteoglycan synthesis and mitotic activity of the chondrocytes and inhibit type X collagen and alkaline phosphatase activity. Ballock RT: Regulation of skeletal growth and maturation by thyroid hormone, in Buckwalter JA, Ehrlich MG, Sandell LJ, Trippel SB (eds): Skeletal Growth and Development: Clinical Issues and Basic Science Advances. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1998, pp 301-317. Rosier RN, O'Keefe RJ, Reynolds PR, Hicks DG, Puzas JE: Expression and function of TGF-beta= and PTHrP in the growth plate, in Buckwalter JA, Ehrlich MG, Sandell LJ, Trippel SB (eds): Skeletal Growth and Development: Clinical Issues and Basic Science Advances. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1998, pp 285-299.

The radiograph reveals an avulsion of the ischial apophysis, most likely the result of violent contraction of the attached hamstring tendons (semimembranosus, semitendinosus, and long head of the biceps femoris). The short head of the biceps femoris arises from the linea aspera on the posterior femur. The pectineus and adductor longus attach to the pubic portion of the pelvis. The piriformis runs from the sacrum to the femur. Woodburne RT (ed): Essentials of Human Anatomy. New York, NY, Oxford University Press, 1978, pp 542-545.

The obturator internus muscle originates from the internal pelvic wall and passes laterally through the lesser sciatic foramen, banking around the ischium below the sacrospinous ligament before inserting on the medial aspect of the greater trochanter. Higuchi T: Normal anatomy and magnetic resonance appearance of the pelvis, in Takahashi HE, Morita T, Hotta T, Ogose A (eds): Operative Treatment of Pelvic Tumors. Tokyo, Japan, Springer-Verlag, 2003, pp 4-21.

Multiple hereditary exostoses (MHE) is an autosomal dominant disorder manifested by multiple osteochondromas and characteristic skeletal involvement. EXT1 on 8q24.1 and EXT2 on 11p13 are the two genes most strongly associated with MHE. Mutations in these genes affect proper development of endochondral bone, such that in all affected individuals exostoses develop adjacent to the growth plates of long bones, and some exhibit additional bone deformities. Defects in the EXT genes result in increased chondrocyte proliferation and delayed hypertrophic differentiation. Stieber JR, Dormans JP: Manifestations of hereditary multiple exostoses. J Am Acad Orthop Surg 2005;13:110-120.

The area shown in the arthroscopic view and MRI scan is referred to as a Buford complex and represents a normal labral variant. It consists of a thickened, cord-like middle glenohumeral ligament, a superior labral attachment of the middle glenohumeral ligament just anterior to the biceps tendon, and absence of the anterosuperior labrum. This combination of findings can be confusing and may simulate labral pathology. Mistaken repair of the lesion back to the glenoid rim can result in significant loss of external rotation. A Bankart lesion would be located at the inferior anterior glenoid rim. The subscapularis is seen anterior to the labrum. Normal variations that occur in the anterosuperior labrum can simulate pathology. Gusmer PB, Potter HG, Schatz JA, et al: Labral injuries: Accuracy of detection with unenhanced MR imaging of the shoulder. Radiology 1996;200:519-524. Griffin LY (ed): Orthopaedic Knowledge Update: Sports Medicine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 47-63.

Pedicle subtraction osteotomy is the preferred osteotomy technique for the treatment of many patients with iatrogenic flatback syndrome. In the presence of an anterior pseudarthrosis, however, it must be done in conjunction with an anterior procedure. Prior laminectomy is not a contraindication. Significant correction, usually averaging about 30 degrees, can be obtained through each osteotomy. Osteotomies should be performed at L2 or below in the presence of kyphosis at the thoracolumbar junction. The pedicle subtraction technique is preferred with vascular calcifications because it does not lengthen the anterior column, which could risk vascular injury. Potter BK, Lenke LG, Kuklo TR: Prevention and management of iatrogenic flatback deformity. J Bone Joint Surg Am 2004;86:1793-1808.

The patient has a volar displaced two-part intra-articular distal radial fracture-dislocation of the wrist. Although a closed reduction is usually easily obtained, it is very difficult to maintain the reduction without internal fixation. The approach is determined by the direction of the dislocation, in this case volar. Stabilization with a buttress plate neutralizes the axial loading forces on the fractured fragment. A dorsal placed angular stable plate will not provide this buttress effect and will make the reduction difficult.

Celiac sprue results in rapid gastrointestinal transit and fatty stools that impair the absorption of calcium and vitamin D and result in nutritional-deficiency osteomalacia with secondary hyperparathyroidism. The radiographs show marked osteopenia with brown tumors. A pathologic fracture is seen in the proximal humerus through a large brown tumor. Serum findings include low or normal calcium, low phosphate, elevated alkaline phosphatase, low 1,25(OH)2D, and increased PTH levels. Secondary hyperparathyroidism is associated with a variety of conditions including malabsorption syndromes. Potts JT: Parathyroid hormone: Past and present. J Endocrinol 2005;187:311-325. Corazza GR, Di Stefano M, Maurino E, et al: Bones in coeliac disease: Diagnosis and treatment. Best Pract Res Clin Gastroenterol 2005;19:453-465.

The TcPO2 measures the O2 delivering capacity of the local vasculature. Values above 40 mm Hg have been shown to correlate with positive healing potential. The hemoglobin A1c is a good indicator of long-term glucose levels; however, it has no direct correlation with wound healing potential. Serum albumin is an indirect measure of nutritional status, and deficiencies in nutrition must be addressed before any surgery. Adequate hemoglobin levels are also necessary to promote adequate oxygenation to the amputation site. The ankle-brachial index may be falsely elevated as a result of calcified vessels in patients with diabetes mellitus. Wyss CR, Harrington RM, Burgess EM, et al: Transcutaneous oxygen tension as a predictor of success after amputation. J Bone Joint Surg Am 1988;70:203-207.

The popliteal tendon arises from the posterior aspect of the tibia and courses through the knee joint through the popliteus hiatus of the lateral meniscus before attaching on the lateral femur anterior to the lateral collateral ligament. It is the only tendon in the knee joint that can be viewed directly on arthroscopy. Kimura M, Shirakura K, Hasegawa A, Kobayashi Y, Udagawa E: Anatomy and pathophysiology of the popliteal tendon area in the lateral meniscus: 1. Arthroscopic and anatomical investigation. Arthroscopy 1992;8:419-423.

Chronic subscapularis tendon ruptures preclude primary repair. In such instances, subcoracoid pectoralis major tendon transfers may improve function and diminish pain. The subcoracoid position of the transfer allows redirection of the pectoralis major in a direction recreating the vector of the subscapularis tendon. Shoulder fusion is a salvage procedure, and corticosteroid injection may reduce pain but will not improve function. Jost B, Puskas GJ, Lustenberger A, et al: Outcome of pectoralis major transfer for the treatment of irreparable subscapularis tears. J Bone Joint Surg Am 2003;85:1944-1951.

The radiographs reveal a scaphoid fracture with displacement and comminution and an unstable fracture pattern. Treatment should consist of open reduction and internal fixation. In displaced scaphoid fractures and fractures with unstable fracture patterns, closed reduction is ineffective and is likely to lead to nonunion. Limited intercarpal fusion and proximal row carpectomy are used to correct a variety of traumatic and posttraumatic problems of the wrist. Amadio PC, Taleisnik J: Fractures of the carpal bone, in Green DP, Hotchkiss RN, Pederson WC (eds): Green's Operative Hand Surgery, ed 4. Philadelphia, PA, 1999, pp 809-823. Rettig ME, Kozin SH, Cooney WP: Open reduction and internal fixation of acute displaced scaphoid waist fractures. J Hand Surg Am 2001;26:271-276. Cooney WP, Dobyns JH, Linscheid RL: Fractures of the scaphoid: A rational approach to management. Clin Orthop 1980;149:90-97.

The radiograph reveals osteonecrosis of both femoral heads with reasonably maintained joint surfaces. There may be some slight flattening of the femoral heads. Hip arthrodesis is difficult to perform because of the necrotic bone. Its use in patients with osteonecrotic hips is limited because of the 80% bilaterality; therefore, it is not an acceptable alternative. All the other options are acceptable interventions. Mont MA, Jones LC, Sotereanos DG, et al: Understanding and treating osteonecrosis of the femoral head. Instr Course Lect 2000;49:169-185.

Although thoracic disk herniations have been reported at all levels of the thoracic spine, more than two thirds are found at T9-T12, which is the more mobile lower third of the thoracic region. Belanger TA, Emery SE: Thoracic disc disease and myelopathy, in Frymoyer JW, Wiesel SW (eds): The Adult and Pediatric Spine. Philadelphia, PA, Lippincott Williams and Wilkins, 2004, pp 855-864.

Ford and associates studied 81 high school basketball players and found that females landed with greater total valgus knee loading and a greater maximum valgus knee angle than male athletes. Hewett and associates reported in a study of 205 female athletes that those with increased dynamic valgus and high abduction loads were at increased risk of anterior cruciate ligament injury. Hewett TE, Myer GD, Ford KR, et al: Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: A prospective study. Am J Sports Med 2005;33:492-501.

The lateral radiograph shows 8 mm of atlantoaxial translation. In the absence of a bony injury, this represents rupture of the transverse atlantal ligament. The MRI scan reveals soft-tissue swelling posterior to the odontoid and a high intensity zone in the atlanto-dens interval consistent with acute injury. These injuries require arthrodesis because nonsurgical measures will not provide stability. Techniques for C1-2 fusion include Gallie, Brooks, or triple wiring. Transarticular screw fixation across the C1-2 articulation provides the most rigid means of fixation and the highest arthrodesis rates but is technically demanding. Anterior C2-3 arthrodesis will not address the level of instability. The normal atlanto-dens interval is 3 mm in an adult and 4 mm in a child. Kurz LT: Transverse atlantal ligament insufficiency, in Clark CR (ed): The Cervical Spine. Philadelphia, PA, Lippincott-Raven, 1998, pp 401-407.

Following anterior dislocation of the shoulder, the affected arm is typically placed in a sling with the shoulder in adduction and internal rotation. A recent study has shown that placement in this position actually results in laxity of the anterior supporting structures of the shoulder, allowing the postinjury hemarthrosis to push the labrum and capsular ligaments away from the anterior glenoid rim. Thus, immobilization in this position may actually impede healing of these structures. Alternatively, resting the arm in a position of adduction and external rotation allows the anterior supporting structures to abut against the anterior glenoid rim by forcing the hemarthrosis posteriorly. Placing the arm in this position following anterior dislocation is believed to allow for better healing of the anterior labrum and ligaments.

The patient has an early prosthesis infection as a result of hematogenous seeding from dental surgery. Irrigation and debridement with polyethylene exchange and IV antibiotics have been successful in early postoperative infections; it is less likely to be effective for a late hematogenous infection. Immediate total component exchange also may be effective, but it should be reserved for failure of irrigation and 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, pp 323-337.

The muscle transfer procedure most commonly performed for trapezius paralysis is the Eden-Lange procedure. Trapezius paralysis in this patient is secondary to iatrogenic injury to the spinal accessory nerve during lymph node biopsy. In this procedure, the levator scapulae and rhomboid minor and major muscles are transferred laterally. Pectoralis transfer to the inferior border of the scapula is used as a dynamic transfer for serratus anterior winging. Kuhn JE, Plancher KD, Hawkins RJ: Scapular winging. J Am Acad Orthop Surg 1995;3:319-325. Langenskiold A, Ryoppy S: Treatment of paralysis of the trapezius muscle by Eden-Lange operation. Acta Orthop Scand 1973;44:383-388.

The etiology of osteochondritis dissecans of the capitellum is somewhat unclear. However, trauma has been implicated in this disease process. Gymnasts who load their upper extremities during tumbling and throwing athletes with repetitive trauma during the throwing motion are common patient subgroups in which osteochondritis dissecans of the elbow is seen. This often occurs in the adolescent age population. Baumgarten TE, Andrews JR, Satterwhite YE: The arthroscopic classification and treatment of osteochondritis dissecans of the capitellum. Am J Sports Med 1998;26:520-523.

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.

The radiographs do not show an articular malunion. Treatment is directed at the soft-tissue contracture and should begin with formal physical therapy and static progressive splinting. Radiation therapy is effective in the perioperative period and is indicated when ectopic bone formation is a concern. Morrey BF: The posttraumatic stiff elbow. Clin Orthop Relat Res 2005;431:26-35.

The MRI findings show highly increased signal through the entire femoral head and neck on STIR imaging, diagnostic of transient osteoporosis of the femoral head. This disease entity can be seen in middle-aged men, and should be treated nonsurgically. The natural history is that of self-resolution. Guerra JJ, Steinberg ME: Distinguishing transient osteoporosis from avascular necrosis of the hip. J Bone Joint Surg Am 1995;77:616-624.

Scapular body fractures in children are rare and are often associated with other injuries of the chest and thorax. Management is generally nonsurgical, unless the injury is open, and usually consists of support with a sling and gentle range-of-motion exercises to minimize shoulder stiffness. Green N, Swiontkowski M: Skeletal Trauma in Children, ed 2. Philadelphia, PA, WB Saunders, 1998, vol 3, pp 319-341.

The plain radiographs show a defect in the lateral femoral condyle and narrowing of the lateral joint space. The MRI scan shows a lesion consistent with osteonecrosis of the lateral femoral condyle. The treatment alternatives for this condition are an osteotomy or a total knee replacement, but a total knee replacement is the treatment of choice for a 72-year-old patient. Arthroscopy or an osteochondral bone graft will not address her symptoms. A valgus osteotomy will exacerbate the problem by overloading the lateral joint, which is already diseased. Lotke PA, Ecker ML: Osteonecrosis of the knee. J Bone Joint Surg Am 1988;70:470-473.

Arthrodesis is indicated for severe bunion and hallux valgus deformities, but particularly with extensive degenerative disease of the first metatarsophalangeal joint. The other bunionectomy procedures have different indications, none of which include symptomatic first metatarsophalangeal degenerative disease. Richardson EG(ed): Orthopaedic Knowledge Update: Foot and Ankle 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 3-15.

Passive stretching is contraindicated during rehabilitation as it may potentiate the severity of the myositis ossificans. Electrical stimulation, iontophoresis, isometric exercise, and ice/heat contrast are not known to exacerbate this process. Brunet ME, Hontas RB: The thigh, in DeLee JC, Drez D (eds): Orthopaedic Sports Medicine. Philadelphia, PA, WB Saunders, 1994, pp 1086-1112.

Owens and Thordardson cautioned surgeons not to release the conjoined tendon from the base of the proximal phalanx of the great toe because of an increased risk of iatrogenic hallux varus. Release of the transverse and oblique heads of the adductor hallucis is largely accomplished by releasing the soft tissue adjacent to the lateral sesamoid, without releasing tissue from the base of the proximal phalanx. The conjoined tendon is made up of the flexor hallucis brevis and the adductor hallucis. Owens S, Thordardson DB: The adductor hallucis revisited. Foot Ankle Int 2001;22:186-191.

Patient safety and prevention of medical errors is a major focus of recent national advocacy groups. Analysis has shown that the most common sentinel event in spine surgery is surgery on the wrong level. Therefore, it is recommended that every patient have the surgical site signed, the level of surgery marked intraoperatively, and a radiograph taken. Surgery on the wrong level is most likely to occur in single-level decompressive procedures. Wong DA, Watters WC III: To err is human: Quality and safety issues in spine care. Spine 2007;32:S2-S8.

Osteochondritis dissecans of the capitellum is seen most commonly in adolescent athletes. It should be distinguished from osteochondrosis of the capitellum (Panner's disease), a self-limiting condition seen in younger patients. Lesions are graded I through V based on radiographic and arthroscopic appearance. Grade I lesions show intact but soft cartilage. Grade II lesions show fissuring of the overlying cartilage. Grade III lesions show exposed bone or an attached osteoarticular flap that is not loose. Grade IV lesions show a loose but nondisplaced osteoarticular flap. Grade V lesions show a displaced fragment. Simple excision of the loose osteoarticular flap is the treatment of choice for grade IV and V lesions. More complex procedures such as drilling of the in situ lesion, bone grafting, or internal fixation are associated with significantly worse results. While some authors advocate abrasion chondroplasty, the long-term benefits of the procedure are yet to be proven. Baumgarten TE: Osteochondritis dissecans of the capitellum. Sports Med Arthroscopy Rev 1995;3:219-223.

The patient has a posterior fracture-dislocation of the hip and following reduction, an incarcerated fragment of bone resulted in an incongruent reduction. Whereas expedient removal of the fragment is required to limit articular cartilage damage, this situation is not an emergency and the procedure may be performed when the appropriate surgical team is available and the patient is stabilized. Skeletal traction through either the femur or tibia may relieve some pressure on the joint and prevent articular damage. Nonsurgical care for incarcerated fragments is contraindicated. Tile M, Olson SA: Decision making: Non operative and operative indications for acetabular fractures, in Tile M, Helfet DL, Kellam JF (eds): Fractures of the Pelvis and Acetabulum. Philadelphia, PA, Lippincott Williams and Wilkins, 2003, pp 496-532.

The MRI scans show Modic changes in the L4-L5 vertebral bodies due to spondylosis. There is no increased fluid signal or enhancement in the L4-L5 disk to suggest infection or any other pathologic process. Therefore, the patient's pain should be treated with a course of physical therapy and rehabilitation. There is no infection; therefore, IV antibiotics and debridement are not indicated. Similarly, a pseudomeningocele is not present. A revision diskectomy is useful for recurrent radiculopathy but would not be helpful for degenerative low back pain. Spivak JM, Connolly PJ (eds): Orthopaedic Knowledge Update: Spine 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, pp 319-329.

Patients with chronic ACL-deficient knees typically have lower than normal net quadriceps activity during the middle portion of the stance phase; the net moment about the knee reverses from one that demands quadriceps activity to one that demands increased hamstring activity. This type of gait is termed "quadriceps avoidance." This avoidance is believed to be a functional adaptation to reduce anterior tibial translation, and it is most prevalent as the knee moves from 45 degrees of flexion toward full extension, the arc of motion through which the ACL is most responsible for stability. Hurwitz DE, Andriacchi TP, Bush-Joseph CA, Bach BR Jr: Functional adaptations in patients with ACL-deficient knees. Exerc Sport Sci Rev 1997;25:1-20. Andriacchi TP, Birac D: Functional testing in the anterior cruciate ligament-deficient knee. Clin Orthop 1993;288:40-47.

CMT is characterized by a cavovarus foot position that increases weight-bearing stresses along the lateral border. Removal of the fifth metatarsal head carries the risk of creating a transfer lesion at the fourth metatarsal head, particularly with a cavovarus foot. Claw toes are common in CMT, but the fifth toe would be flail in this situation. Ulceration is unlikely given the lack of underlying bone. Peroneal atrophy is associated with CMT but would not be a complication of this procedure. Charcot arthropathy is a neuropathic process frequently seen in individuals with diabetes mellitus. Kitaoka HB, Holiday AD Jr: Metatarsal head resection for bunionette: Long-term followup. Foot Ankle 1991;11:345-349.

Morphologic and anatomic studies confirm the pedicle is smaller on the concave side of thoracic curves. The dura is also closer to the pedicle on the concave side of the curves. Liljenqvist U, Allkemper T, Hackenberg L, et al: Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction. J Bone Joint Surg Am 2002;84:359-368.

Patients who sustain grade III open fractures that are related to a farm environment require ampicillin or penicillin for Clostridium coverage. Holton PD, Mader J, Nelson CL, Osmon DR, Patzakis MJ: Antibiotics for the practicing orthopaedic surgeon. Instr Course Lect 2000;341:36-42.

It is generally accepted that reconstructions of the proximal tibia are associated with the highest incidence of failure, probably because of poor soft-tissue coverage, the need for extensor mechanism reconstruction, and other anatomic issues. It also may be related to the fact that patients with tumors of the proximal tibia, in general, have a better prognosis and better survival rates than patients with tumors located elsewhere in the body. Reconstructions of the proximal humerus may be more durable because they are not involved in weight-bearing activities.

In local gigantism, a ray resection allows proper fitting of shoes. The ray resection narrows the foot and shortens the length. The foot may require further surgery with growth. Debulking, physeal arrest, and distal phalanx amputation are unlikely to be effective. Turra S, Santini S, Cagnoni G, Jacopetti T: Gigantism of the foot: Our experience in seven cases. J Pediatr Orthop 1998;18:337-345.

The radiograph reveals disruption of the syndesmosis with lateral displacement of the talus and widening of the medial ankle clear space. No fibular fracture is noted, although radiographs of the entire tibia and fibula are necessary to rule out a more proximal fibula fracture. There is clear instability of the syndesmosis, and surgical stabilization is needed, either by direct repair of the ligaments or more commonly with surgical stabilization of the fibula to the tibia with screws. Functional rehabilitation and early range of motion are indicated with anterior-lateral ankle sprains but not with true instability of the syndesmosis. In anterior syndesmotic injuries in which there are no signs of instability on plain radiographs or with stressing, cast immobilization and protected weight bearing until tenderness subsides is warranted. Long leg cast immobilization is unlikely to be adequate in maintaining reduction of the syndesmosis. Repair of the talofibular ligaments or fibular osteotomy does not address the pathology at the syndesmosis. Chronic syndesmotic disruption is likely to lead to chronic ankle pain and early arthrosis. Wuest TK: Injuries to the distal lower extremity syndesmosis. J Am Acad Orthop Surg 1997;5:172-181.

Spontaneous swelling with the appearance of joint subluxation may be associated with an acute, subacute, or chronic bacterial infection of the sternoclavicular joint. Common causes of infection include bacteremia, rheumatoid arthritis, alcoholism, intravenous drug use, and chronic debilitating diseases. Subclavian vein catheterization and renal dialysis can predispose patients to sepsis and osteomyelitis of the sternoclavicular joint. Renoult B, Lataste A, Jonon B, et al: Sternoclavicular joint infection in hemodialysis patients. Nephron 1990;56:212-213.

Exposure of polyethylene to radiation and then heating it to quench the free radicals leads to a cross-linked material. It converts a high molecular weight polyethylene macromolecule to an interpenetrating network structure of polymer chains. The ductility of the material is decreased, hence the greater risk of fracture. While the wear rate (measured as fewer and smaller particles) against a smooth counterface is markedly reduced, cross-linked polyethylene has shown a larger increase in wear rate when a rougher counterface is used compared to noncross-linked material. Due to reduced mechanical strength, highly cross-linked polyethylene is less resistant to abrasive wear.

A rotator cuff tear is the most common cause of recurrent instability following a first-time dislocation in patients older than age 40 years. Dislocations occur through a posterior mechanism rather than by an isolated labral avulsion or a Bankart lesion as seen in younger patients. Nevaiser RJ, Nevaiser TJ: Recurrent instability of the shoulder after age 40. J Shoulder Elbow Surg 1995;4:416-418.

Although the imaging reveals generalized lumbar spondylosis and stenosis, in particular at L4-5, the MRI scan of the left hip clearly reveals a stress fracture of the femoral neck. Therefore, the treatment of choice is non-weight-bearing of the left lower extremity. During the evaluation of acute back pain, clinicians must include other possibilities within the differential diagnosis that may mimic mechanical axial back pain; thus, potential complications from a missed diagnosis can be avoided. Wong DA, Transfeldt E: Macnab's Backache, ed 4. Philadelphia, PA, Lippincott Williams and Wilkins, 2007, pp 339-361.

Joint contact pressure is a stress and as such is defined as the load transferred across the joint divided by the contact area between the joint surfaces (the area over which the joint load is distributed). Therefore, any mechanism that decreases the load across the joint (eg, a walking aid) will decrease the stress. Similarly, any mechanism that increases the area over which the load is distributed (eg, using a more conforming set of articular surfaces in a knee joint arthroplasty) will also decrease the stress. Other mechanisms that influence joint contact pressure include the elastic modulus of the materials (cartilage in the case of natural joints and polyethylene in joint arthroplasty) and the thickness of the structures through which the joint loads pass. Bartel DL, Bicknell VL, Wright TM: The effect of conformity, thickness, and material on stresses in UHMWPE components for total joint replacement. J Bone Joint Surg Am 1986;68:1041-1051.

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.

Reverse oblique intertrochanteric femoral fractures account for 5% of all intertrochanteric or subtrochanteric fractures. They are uncommon but not rare and will be encountered in practice. The sliding hip screw is associated with the most problems because of its design. When reverse oblique fractures are fixed with a sliding hip screw, the action of the construct causes medial displacement of the distal fragment rather than compression of the proximal and distal fragments. All of the other implants prevent medial displacement of the distal segment. It should not be assumed that simply using one of the other implants is reason for success. There is a significant failure rate for each of these implants with reverse oblique fractures. The implant must be ideally placed and the fracture must be reduced. Haidukewych GJ, Israel TA, Berry DB: Reverse obliquity fractures of the intertrochanteric region of the femur. J Bone Joint Surg Am 2001;83:643-650. Sanders RW, Regazzoni P: Treatment of subtrochanteric femur fractures using the dynamic condylar screw. J Orthop Trauma 1989;3:206-213.

Eighty percent of giant cell tumors occur in patients older than age 20 years, with the peak incidence in the third decade of life. Most of these tumors are eccentrically located and epiphyseal in location. They are lytic in nature as in this patient. Although named for the hallmarked multinucleated giant cells seen in the lesion, the basic cell type is the spindle-shaped stromal cell. Chondroblastoma is highly cellular and contains large multinucleated giant cells with intercellular chondroid material, some of which is calcified. Chondromyxoid fibroma has chondroid tissue separated by strands of more cellular tissue with occasional multinucleated giant cells. Desmoplastic fibroma is characterized by poorly cellular fibrous tissue, and lymphoma is highly cellular with characteristic round cells. Campanacci M, Baldini N, Boriani S, et al: Giant cell tumor of bone. J Bone Joint Surg Am 1987;69:106-114.

In secondary amenorrhea, women do not receive the estrogen needed to maintain adequate bone mineralization. This hypoestrogenic state affects bone density, and there is evidence that stress fractures are more frequent in amenorrheic than eumenorrheic athletes. The other conditions are not seen with increased frequency in amenorrheic athletes. Warren MP: Health issues for women athletes: Exercise-induced amenorrhea. J Clin Endocrinol Metab 1999;84:1892-1896.

The patient has entrapment of the superficial peroneal nerve against its fascial opening in the distal leg. It is typically exacerbated by passive or active plantar flexion and inversion of the foot, which leads to traction of the nerve as it exits this opening. Treatment involves release of the fascial opening to reduce this traction phenomenon. Closure of the defect will only aggravate the condition and potentially result in an exertional compartment syndrome. A four-compartment fasciotomy is only indicated for an established compartment syndrome of the leg. Styf J: Diagnosis of exercise-induced pain in the anterior aspect of the lower leg. Am J Sports Med 1988;16:165-169. Sridhara CR, Izzo KL: Terminal sensory branches of the superficial peroneal nerve: An entrapment syndrome. Arch Phys Med Rehabil 1985;66:789-791.

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.

This lytic lesion is in the epiphyseal-metaphyseal region of the distal tibia. The most common lesion in this area is a giant cell tumor. Although these lesions are most commonly seen in adults, they can also occur in the skeletally immature patient. The photomicrograph shows a lesion with multiple giant cells, the nuclei of which are similar to those in the background stroma; this finding is characteristic of giant cell tumors. Giant cells can be seen in many benign lesions, including aneurysmal bone cysts, Brown tumors, and eosinophilic granuloma. These lesions usually have fewer giant cells with less nuclei. The location of this lesion in the epiphyseal-metaphyseal area is not seen in aneurysmal bone cysts, unicameral bone cysts, Ewing's sarcoma, or eosinophilic granuloma.

Spontaneous subluxation of the sternoclavicular joint occurs without any significant trauma. It is usually accentuated by placing the extremity in an overhead position. Discomfort usually resolves within 4 to 6 weeks with nonsurgical management. Rockwood CA, Wirth MA: Disorders of the sternoclavicular joint, in Rockwood CA, Matsen FA, Wirth MA, et al (eds): The Shoulder. Philadelphia, PA, WB Saunders, 2004, vol 2, pp 1078-1079.