General Orthopedics Board Review 2026: High-Yield MCQs (Set 10)

<span class="exp-title">Detailed Explanation</span><div markdown="1">When markedly diminished space available for the cord (demonstrated by a posterior atlantoaxial interval of less than 10 mm) is seen, there is a poor prognosis for recovery (25% of Ranawat class IIIb patients) following surgery. A posterior atlantoaxial interval of 14 mm or less is a predictor of increased risk of paralysis, but patients with an interval between 10 mm and 14 mm have a greater chance of recovery. Space available for the cord that is at least 14 mm is not associated with an increased risk of neurologic deficit. Boden SD, Dodge LD, Bohlman HH, et al: 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.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The fracture is a both-column fracture in the Judet/Letournel classification and a C3 in the AO classification. There is extension into the sacroiliac joint along the pelvic brim and comminution along the posterior column above the sciatic notch. Both the anterior and posterior columns are separately broken and displaced. However, the defining feature of a both-column pattern, as seen in this patient, is that all articular fragments are on fracture fragments and no joint surface is left intact to the axial skeleton above. The use of three-dimensional images makes it easier to view the location of the fracture fragments and the amount and direction of displacement. Helfet DL, Beck M, Gautier E, et al: Surgical techniques for acetabular fractures, in Tile M, Helfet DL, Kellam JF (eds): Fractures of the Pelvis and Acetabulum. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 533-603. Tile M: Describing the injury: Classification of acetabular fractures, in Tile M, Helfet DL, Kellam JF (eds): Fractures of the Pelvis and Acetabulum, ed 3. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 427-475.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In adults, a direct blow on the acromion usually results in an acromioclavicular dislocation. In children, however, the usual injury from this mechanism is a physeal fracture of the lateral clavicle. The clavicular shaft fragment, analogous to the metaphyseal portion of a physeal fracture, herniates through the periosteum, leaving the distal periosteal sleeve in contact with the lateral (distal) physeal fragment. The treatment of choice is immobilization until the patient is pain-free. Falstie-Jensen S, Mikkelsen P: Pseudodislocation of the acromioclavicular joint. J Bone Joint Surg Br 1982;64:368-369.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a Charcot arthropathy of the knee, which is associated with amyloidosis. The rapid joint destruction shown in the radiographs is most consistent with that diagnosis. Drennan D, Fahey J, Maylahn D: Important factors in achieving arthrodesis of the Charcot knee. J Bone Joint Surg Am 1971;53:1180-1193. Soudry M, Binazzi R, Johanson N, et al: Total knee arthroplasty in Charcot and Charcot like joints. Clin Orthop 1986;208:199-204.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Although the Holstein-Lewis fracture, described as an oblique distal one third fracture, is best known for its association with neurologic injury, radial nerve palsy is most commonly associated with middle one third humeral fractures. Most nerve injuries are neurapraxias or axonotmeses, with up to 90% resolving in 3 to 4 months. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 271-286.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The anterior band of the ulnar collateral ligament provides the greatest restraint to valgus stress in the elbow. The posterior band is taut in flexion and resists stress between 60 degrees and full flexion. The annular ligament stabilizes the radial head. The flexor/pronator mass are important dynamic stabilizers of the medial elbow. Ahmad CS, ElAttrache NS: Elbow valgus instability in the throwing athlete. J Am Acad Orthop Surg 2006;14:693-700. Regan WD, Korinek SL, Morrey BF, et al: Biomechanical study of ligaments around the elbow joint. Clin Orthop Relat Res 1991;271:170-179.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Mild scoliosis is not a painful condition, but it usually presents during adolescence. Intermittent back pain is reported by 25% to 30% of adolescents whether or not scoliosis is present. Such pain is often attributed to muscle strain from tight muscles, poor posture, or heavy school backpacks. The clinician must distinguish typical pain (mild, intermittent, nonlimiting) from atypical pain. The latter requires more careful examination and imaging studies (bone scan or MRI) to determine the source of pain. The patient's age and right thoracic curve pattern are typical for idiopathic scoliosis; therefore, imaging of the neuroaxis is not necessary to look for cord syrinx, tethering, or tumor. Brace treatment is not required for this small curve unless future progression is demonstrated. Ramirez N, Johnston CE, Browne RH: The prevalence of back pain in children who have idiopathic scoliosis. J Bone Joint Surg Am 1997;79:364-368. Hollingworth P: Back pain in children. Br J Rheum 1996;35:1022-1028.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In examining a traditional Muslim woman, a male physician should have another woman present, and the patient's husband, if possible. Only the affected limb or area needing examination should be exposed.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Transphyseal fractures of the proximal femur at birth are more likely to occur in large newborns after a difficult delivery. At rest, the patients are comfortable and show a pseudoparalysis; however, passive motion of the lower extremity results in discomfort. Teratologic hip dislocations will have a positive Galeazzi sign, but are not painful. Development of a septic hip would be unlikely within 12 hours postpartum. Congenital coxa vara is typically painless. Postpartum ligamentous laxity might account for a positive Ortolani sign, but is painless. Weinstein JN, Kuo KN, Millar EA: Congenital coxa vara: A retrospective review. J Pediatr Orthop 1984;4:70-77.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Anterior coverage of the hip may be best estimated by the anterior center edge angle of Lequesne and de Seze (analogous to Wiberg's angle), which is measured on the well-defined faux profil view. Evaluation with CT scans also has been described. Klaue K, Wallin A, Ganz R: CT evaluation of coverage and congruency of the hip prior to osteotomy. Clin Orthop 1988;232:15-25.

<span class="exp-title">Detailed Explanation</span><div markdown="1">A periosteal desmoid lesion is a tumor simulator. It is characterized by a bone irregularity along the posteromedial aspect of the distal femur at the insertion of the adductor magnus or the origin of the gastrocnemius muscle. It most commonly occurs in patients who are age 10 to 15 years. The lesions are asymptomatic, with no palpable mass, pain, or swelling. They are frequently an incidental finding when radiographs are obtained for nonspecific symptoms or trauma about the knee. Following recognition of the characteristic imaging findings, observation is the management of choice. Dunham WK, Marcus NW, Enneking WF, et al: Developmental defects of the distal femoral metaphysis. J Bone Joint Surg Am 1980;62:801-806.

<span class="exp-title">Detailed Explanation</span><div markdown="1">A complete tear of the distal biceps brachii most often occurs from a large, rapid eccentric elbow extension load. A pop or tearing sensation usually occurs, and a palpable defect in the antecubital fossa is often present on examination. The treatment of choice is a direct primary repair by a two-incision technique. If left unrepaired, the most disabling consequence is the loss of forearm supination strength. It is unlikely that significant elbow or forearm motion will be lost if the rupture is left unrepaired and early motion exercises are initiated. Elbow flexion strength tends to return with time, but the loss of forearm supination strength remains problematic. D'Alessandro DF, Shields CL Jr, Tibone JE, Chandler RW: Repair of distal biceps tendon ruptures in athletes. Am J Sports Med 1993;21:114-119.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Major advances in diagnostic imaging, neoadjuvant chemotherapy, and surgical techniques have allowed limb salvage to be performed as an alternative to amputation in children with osteosarcoma. The outcome of treatment of nonmetastatic, high-grade osteosarcoma of the distal femur was studied in 227 patients from 26 institutions. The authors found no difference in the long-term survival or quality of life between patients treated with limb salvage and those treated with amputation. Patients treated with limb salvage had a higher rate of reoperation, but a better functional outcome. Rougraff BT, Simon MA, Kneisl JS, Greenberg DB, Mankin HJ: Limb salvage compared with amputation for osteosarcoma of the distal end of the femur: A long-term oncological, functional, and quality-of-life study. J Bone Joint Surg Am 1994;76:649-656.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Although osteochondromas can occur in almost every bone in patients with MHE, proximally located lesions are more likely to undergo malignant transformation. Annual radiographs of the shoulder girdles and pelvis are indicated in patients with MHE. Any enlarging osteochondromas are a concern as possible malignancies. Peterson HA: Multiple hereditary osteochondromata. Clin Orthop 1989;239:222.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The modified posterior approach with elevation of the medial and lateral heads of the triceps can provide exposure of 94% of the humeral shaft. The traditional posterior triceps-splitting approach exposes 55% of the humeral shaft. DeFranco MJ, Lawton JN: Radial nerve injuries associated with humeral fractures. J Hand Surg Am 2006;31:655-663.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Collagen type X is produced only by hypertrophic chondrocytes during enchondral ossification (growth plate, fracture callus, heterotopic ossification) and is associated with calcification of cartilage in the deep zone of articular cartilage. Collagen type I is the predominant collagen in bone, ligament, and tendon. Collagen type II is the predominant collagen in articular cartilage. Proteoglycan aggrecan and hyaluronic acid are components of the extracellular matrix and are involved in the compressive strength characteristics of articular cartilage. Buckwalter JA, Mankin HJ: Articular cartilage: Tissue design and chondrocyte matrix interactions. Instr Course Lect 1998;47:477-486.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Secondary chondrosarcomas are most common in patients with multiple hereditary exostosis. Dedifferentiated chondrosarcoma is less common and refers to bone lesions in which a high-grade spindle cell sarcoma component is located immediately adjacent to a low-grade cartilage neoplasm. Mesenchymal chondrosarcoma, clear cell chondrosarcoma, and periosteal osteosarcoma are no more common in patients with multiple hereditary exostosis than in the general population. Mirra JM: Bone Tumors: Clinical, Radiologic, and Pathologic Correlations. Philadelphia, PA, Lea and Febiger, 1989, pp 1660-1669.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In approximately 15% of children with Down syndrome, atlantoaxial instability develops because of ligament laxity, making them susceptible to spinal cord injury with relatively minor trauma. The American Academy of Pediatrics recommends lateral flexion-extension views of the cervical spine in any patient with Down syndrome who wishes to participate in sports. A normal ADI is up to 4 mm. Patients with Down syndrome with an ADI of more than 5 mm should not participate in contact sports or sports with a high risk for neck injury, such as diving, gymnastics, high jump, or butterfly stroke. Cervical fusion has a very high rate of complications in patients with Down syndrome and is recommended only for patients who have myelopathic signs or symptoms. Atlantoaxial instability in Down syndrome: Subject review. American Academy of Pediatrics Committee on Sports Medicine and Fitness. Pediatrics 1995;96:151-154. Tredwell SJ, Newman DE, Lockitch G: Instability of the upper cervical spine in Down syndrome. J Pediatr Orthop 1990;10:602-606.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Sternoclavicular hyperotosis is a seronegative and HLA-B27 negative rheumatic disease. In this condition, hyperostosis may appear in the spine, long bones, sacroiliac joints, and the sternoclavicular region. This entity is also associated with palmoplantar pustulosis. Wirth MA, Rockwood CA: 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 608-609.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The radiographs show narrowing of the medial joint space, which indicates polyethylene wear and progressive varus alignment. Wear particles incite osteolytic lesions like the one seen on the lateral radiograph. O'Rourke MR, Callaghan JJ, Goetz DG, et al: Osteolysis associated with a cemented modular posterior-cruciate-substituting total knee design. J Bone Joint Surg Am 2002;84:1362-1371.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has an open fracture of the physis of the distal phalanx with a portion of the nail bed interposed in the physis. Seymour initially described this injury in the distal phalanges of fingers. Optimal treatment consists of removing the interposed tissue, irrigating the fracture, and a short course of antibiotics. The nail should be preserved to provide stability. Kensinger DR, Guille JT, Horn BD, et al: The stubbed great toe: Importance of early recognition and treatment of open fractures of the distal phalanx. J Pediatr Orthop 2001;21:31-34. Pinckney LE, Currarino G, Kennedy LA: The stubbed great toe: A cause of occult compound fracture and infection. Radiology 1981;138:375-377.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a dislocation of the elbow with displaced coronoid process and radial head fractures. The elbow is extremely unstable after this injury, and recurrent dislocation in a splint is the most common early complication. Skeletal stabilization of the fractures is required to restore stability of the joint. Characteristics of the fractures will determine the techniques required to restore stability. Ring D, Jupiter JB, Zilberfarb J: Posterior dislocation of the elbow with fractures of the radial head and coronoid. J Bone Joint Surg Am 2002;84:547-551.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Persistent Horner's sign (ptosis, myosis, and anhydrosis) is a sign of proximal injury, usually avulsion of the roots from the cord which disrupts the sympathetic chain. Root rupture or avulsion proximal to the myelin sheath has less chance of healing. Two-month-old infants with persistent weakness in the other areas described may still have a good prognosis for recovery. Concurrent clavicle fracture has been shown to have no prognostic value. Clarke HM, Curtis CG: An approach to obstetrical brachial plexus injuries. Hand Clin 1995;11:563-581.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Vascular invasion, histologically similar to granulation tissue, has been noted between the columns in the zone of hypertrophy, leading to the theory of microtrauma as an etiology. SCFE is also associated with conditions that increase the height of the zone of hypertrophy, including the adolescent growth spurt and endocrinopathies. The perichondral ring has been shown to decrease in thickness with age. Normal undulations in the growth plate also decrease during this time, possibly further destabilizing the physis. Abnormal accumulations of proteoglycan have been reported. Chung SM, Batterman SC, Brighton CT: Shear strength of the human femoral capital epiphyseal plate. J Bone Joint Surg Am 1976;58:94-103.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The average location of the anterior portal is 6.3 cm distal to the anterior superior iliac spine. The lateral femoral cutaneous nerve typically has divided into three or more branches at the level of the anterior portal. The portal usually passes within several millimeters of the most medial branch. Injury to the nerve can lead to meralgia paresthetica. The femoral nerve lies an average minimum distance of 3.2 cm from the anterior portal. The ascending branch of the lateral circumflex artery lies approximately 3.7 cm inferior to the anterior portal. Neither the ascending branch of the medial circumflex artery nor the superior gluteal nerve are at risk. Byrd JWT: Operative Hip Arthroscopy. New York, NY, Thieme Medical Publishers, 1998, pp 83-91.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Patients who are in compensated shock have normal vital signs but still have hypoperfusion of organ beds such as the splanchnic circulation due to preferential perfusion of the heart and brain. The response to this continued hypoperfusion may be the development of a systemic inflammatory response that may lead to multiple organ failure. The patients are thought to be at risk for a "primed" immune system due to the ongoing stimulation of the immune system and may have an exaggerated response to a second stimulus such as surgery or infection. Other markers of resuscitation should be used besides vital signs to determine when resuscitation has been completed. The use of temporizing fixation has been shown to lower systemic complication rates, and the infection and union rate after staged fixation is not altered. Schulman AM, Claridge JA, Carr G, et al: Predictors of patients who will develop prolonged occult hypoperfusion following blunt trauma. J Trauma 2004;57:795-800.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In the Smith-Petersen approach to the hip, dissection is carried out between the tensor fascia lata laterally (supplied by the superior gluteal nerve) and the sartorius and rectus femoris medially (both supplied by the femoral nerve). Crenshaw AH Jr: Surgical techniques and approaches, in Canale ST (ed): Campbell's Operative Orthopaedics, ed 9. St Louis, MO, Mosby-Year Book, 1998, vol 1, pp 82-85.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has extensive degenerative changes in both the medial and lateral compartments within the knee; therefore, arthroscopic debridement or an osteotomy will not be helpful. A patellar arthroplasty will not address the medial and lateral compartments. Because the extensor mechanism provides a significant amount of anteroposterior stability, a posterior cruciate-substituting total knee arthroplasty is the treatment of choice for this patient. Martin SD, Haas SB, Insall JN: Primary total knee arthroplasty after patellectomy. J Bone Joint Surg Am 1995;77:1323-1330.

<span class="exp-title">Detailed Explanation</span><div markdown="1">While it is recommended that a patient gain full range of motion, pain-free function, and symmetric strength prior to returning to vigorous activities, it is absolutely essential that radiographs of the fracture site reveal a circumferential external bridging callus to prevent refracture. This is particularly important for comminuted femoral fractures with various sized fragments. It is also recommended that a return to rodeo riding be postponed for at least 1 year. Brumback RJ, Ellison TS: Intermedullary nailing of femoral stress fractures. J Bone Joint Surg Am 1992;74:106-112. Bucholz RW, Jones A: Fractures of the shaft of the femur. J Bone Joint Surg Am 1991;73:1561-1566.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The radiograph shows a purely radiolucent lesion without matrix mineralization in the epiphysis of the distal radius. The lesion is "hot" on bone scan, and the MRI scan reveals cortical destruction with a soft-tissue mass. These findings are most consistent with giant cell tumor. The distal radius is a common location for giant cell tumors. The other options would be very uncommon in this location in a 45-year-old patient. The photomicrograph demonstrates multinucleated giant cells in a sea of mononuclear cells. The nuclei of the giant cells and the nuclei of the mononuclear stromal cells are identical. This feature helps distinguish giant cell tumor from other lesions that might contain giant cells. Cheng CY, Shih HN, Hsu KY, et al: Treatment of giant cell tumor of the distal radius. Clin Orthop Relat Res 2001;383:221-228.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has Kienbock's disease (osteonecrosis of the lunate), which presents with boggy synovitis of the wrist, decreased range of motion, and often normal radiographs. The patient's radiographs reveal small fragments from the lunate, with increased density in the lunate body. While a traumatic event may precede the patient's pain, often an insidious increase in pain is found. Repetitive trauma has been suggested as a possible cause. This disease process is classically associated with an ulnar-negative variant. An MRI scan, revealing a low-intensity signal in the lunate, is the best diagnostic tool for early Kienbock's disease. Green DP, Hotchkiss RN, Pederson WC: Green's Operative Hand Surgery, ed 4. Philadelphia, PA, Churchill Livingstone, 1999, pp 837-848.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has osteosarcoma. The radiograph suggests an aggressive primary tumor of bone, and the histology shows malignant cells surrounded by osteoid, classic for osteosarcoma. Ewing's sarcoma histologically consists of small round blue cells. Osteochondroma and periosteal chondroma occur in the shoulder but have a different histologic pattern and a less aggressive radiographic appearance. Chondrosarcomas rarely occur in children. Simon MA, Springfield DS, et al: Osteogenic Sarcoma: Surgery for Bone and Soft Tissue Tumors. Philadelphia, PA, Lippincott Raven, 1998, p 266.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Absence of the rotator cuff results in superior migration of the humeral head because of unopposed deltoid function. This proximal migration results in eccentric loading of glenoid components with early loosening. Hemiarthroplasty yields good pain relief with limited goals of active elevation of 90 degrees. The coracoacromial arch should be preserved. Achieving satisfactory subscapularis tension is preferred to the use of an oversized humeral component. Zeman CA, Arcand MA, Cantrell JS, Skedros JG, Burkhead WZ Jr: The rotator cuff-deficient arthritic shoulder: Diagnosis and surgical management. J Am Acad Orthop Surg 1998;6:337-348. Arntz CT, Jackins S, Matsen FA III: Prosthetic replacement of the shoulder for the treatment of defects in the rotator cuff and the surface of the glenohumeral joint. J Bone Joint Surg Am 1993;75:485-491. Williams GR Jr, Rockwood CA Jr: Hemiarthroplasty in rotator cuff-deficient shoulders. J Shoulder Elbow Surg 1996;5:362-367.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Conus medullaris syndrome describes isolated loss of bowel and bladder function, usually at T12-L1 but can include T11-L2. In central cord syndrome, lower extremity motor function is better than upper extremity function. Cauda equina syndrome generally involves injury at the lumbar levels, with some degree of lower extremity motor loss. Posterior cord syndrome is characterized by preservation of motor function below the level of injury and position/vibratory sensory loss. In anterior cord syndrome, the lower extremity findings include loss of light touch, sharp/dull, and temperature sensations below the level of injury, as well as motor function. Apple DF Jr: Spinal cord injury rehabilitation, in Rothman RH, Simeone FA (eds): The Spine, ed 3. Philadelphia, PA, WB Saunders, 1992, Chapter 31.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a cavovarus deformity that has resulted in lateral foot overload and stressing of the lateral ligaments. Further treatment depends on the ability to correct the deformity. The Coleman block test indicates whether a deformity is fixed or supple. A supple deformity will respond to orthotic management or soft-tissue procedures, while a fixed deformity requires corrective osteotomy or fusion. Physical therapy, casting, and injection will not address the underlying pathophysiology. There is no indication that this is a neuropathic problem.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Kondrashov and associates noted stable good outcomes at 4 years in 14 of 18 patients treated with X-STOP interspinous process decompression as defined as an improvement over preoperative Oswestry scores of 15 points or more. Similar results were seen after 1 year in a European study by Siddiqui and associates. Exclusion and inclusion criteria for these studies varied somewhat, but cauda equina syndrome was the only exclusion criteria listed in both studies. All of the other choices did not represent exclusion criteria in either study. Kondrashov DG, Hannibal M, Hsu KY, et al: Interspinous process decompression with the X-STOP device for lumbar spinal stenosis: A 4-year follow-up study. J Spinal Disord Tech 2006;19:323-327.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The nerve to the abductor digiti quinti is the first branch of the lateral plantar nerve. It branches off while the nerve is still on the medial side of the foot and also innervates a portion of the plantar fascia. It can become entrapped beneath the deep fascia of the abductor hallucis muscle and has been associated with some forms of chronic heel pain. Baxter DE, Pfeffer GB: Treatment of chronic heel pain by surgical release of the first branch of the lateral plantar nerve. Clin Orthop 1992;279:229-236.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Open release allows lengthening of the shortened subscapularis and is preferred when there are extra-articular contractures. Arthroscopic release, combined with the use of an interscalene catheter postoperatively, is an excellent treatment for capsular contractures but is contraindicated after procedures that result in extracapsular shortening (ie, Magnuson-Stack, Putti-Platt). Additional physical therapy or manipulation under anesthesia is not likely to be helpful. Shoulder hemiarthroplasty is contraindicated with normal articular surfaces, but prosthetic arthroplasty is sometimes necessary for arthritis associated with instability or overly tight instability repairs. Harryman DT II, Matsen FA III, Sidles JA: Arthroscopic management of refractory shoulder stiffness. Arthroscopy 1997;13:133-147. Warner JJ: Frozen shoulder: Diagnosis and management. J Am Acad Orthop Surg 1997;5:130-140. Warner JJ, Allen AA, Marks PH, Wong P: Arthroscopic release of postoperative capsular contracture of the shoulder. J Bone Joint Surg Am 1997;79:1151-1158.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Traditionally, patients have been viewed as ignorant about medical matters and ill-equipped to determine what is in their best interest. This has been especially true for minors. However, recent informed consent policies are now based on the patient's right to self-determination. While most spinal surgeons would agree that spinal fusion improves pulmonary function, sitting balance, and comfort, they would also agree that this comes at considerable risk in a patient with compromised pulmonary function and ultimately, a terminal condition. With increasing frequency, young people older than age 14 years are gaining greater autonomy in decision making about their health care matters. This includes do not resuscitate orders when young patients are terminally ill, as well as in less serious situations. Surgery could be performed with the permission of the legal guardians; however, in this situation it is preferable to follow the patient clinically until he consents to surgery along with the legal guardians. Bracing is contraindicated. Reich WT (ed): Encyclopedia of Bioethics. New York, NY, Simon and Schuster, 1995, pp 1256-1265. Confidential health services for adolescents. Council on Scientific Affairs, American Medical Association. JAMA 1993;269:1420-1424.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The main consequence of tumor invading the bone is activation of both osteoblasts and osteoclasts. However, the osteoclastic effect predominates in the majority of tumors early after the invasion of bone by tumor cells, causing resorption of bone. Cramer SF, Fried L, Carter KJ: The cellular basis of metastatic bone disease in patients with lung cancer. Cancer 1981;48:2649-2660.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Treatment of congenital pseudarthrosis of the tibia is problematic. To achieve union, a resection of the pseudarthrosis, stabilization, and bone grafting must be performed. Simple cast immobilization does not yield union. There are various options for the resection, immobilization, and grafting. On the first surgical attempt, retrograde intramedullary nailing offers the best chance for success by transfixing the ankle and subtalar joints with abundant autogenous bone grafting. Distraction osteogenesis and vascularized free fibular graft are reserved as salvage procedures. Gilbert A, Brockman R: Congenital pseudarthrosis of the tibia: Long-term follow-up of 29 cases treated by microvascular bone transfer. Clin Orthop 1995;314:37-44. Boero S, Catagni M, Donzelli O, Facchini R, Frediani PV: Congenital pseudarthrosis of the tibia associated with neurofibromatosis - 1: Treatment with Ilizarov's device. J Pediatr Orthop 1997;17:675-684.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Severely displaced acromioclavicular injuries disrupt the deltotrapezial fascia and muscular origin in addition to the ligaments (acromioclavicular and coracoclavicular or trapezoid and conoid). When the deltoid is still attached to the clavicle, an isometric shoulder shrug will tend to reduce the displacement. When the deltoid is detached but the trapezius is attached, this manuever will increase the deformity and surgery may be indicated.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Pauciarticular juvenile rheumatoid arthritis (JRA) is the most common subgroup of JRA. It typically presents between the ages of 2 to 4 years with a mild swelling of one to four joints. Girls are affected four times more often than boys. The ankle and knee are commonly involved, and limping is typically worse in the morning and after extended activity. The diagnosis of pauciarticular JRA is typically one of exclusion because laboratory studies, including erythrocyte sedimentation rate and rheumatoid factor, are usually within normal limits. Pauciarticular JRA has the highest incidence of chronic uveitis, and in the subgroup with elevated antinuclear antibody (ANA) titers, the incidence is 75%. In JRA, uveitis usually occurs after the onset of synovitis but may precede the joint symptoms. At the early stage of uveitis, the patient is asymptomatic. If the eye condition is not detected and treated, progressive loss of vision may occur. Orthopaedic surgeons may be instrumental in making the diagnosis of pauciarticular JRA. Pauciarticular JRA is not associated with conditions that require input from the other specialists. Carey TP: Inflammatory arthritides: Juvenile rheumatoid arthritis, seronegative spondyloarthropathies, transient synovitis, hemophilic arthropathy, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 1315-1321.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Children with JRA frequently have valgus in association with hypervascularity because of chronic inflammation. This is normally caused by overgrowth of the medial femoral epiphysis. Staple hemiepiphyseodesis, if done early, can reverse the deformity. Osteotomy is usually unnecessary at this age, and there is a risk of stiffness of the knee following the procedure. Synovectomy may be helpful but will not prevent or correct a deformity.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a cauda equina syndrome. The fact that he has decreased rectal tone and urinary retention suggests the need for urgent surgery. Patients who are left untreated will have a poor prognosis for return of function. Although most patients who have insidious onset of symptoms with urinary retention will regain normal motor function following decompression, nearly one third will continue to have abnormal voiding patterns or sexual dysfunction of varying degrees. Kostuik JP, Harrington I, Alexander D, Rand W, Evans D: Cauda equina syndrome and lumbar disc herniation. J Bone Joint Surg Am 1986;68:386-391.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a grade 4 spondylolisthesis. Optimal surgical management is posterior spinal fusion from L4 to the sacrum. The use of instrumentation is controversial. Vertebrectomy is typically reserved for spondylo-optosis (grade 5) cases. Spinal fusion from L5 to S1 usually is not successful for a slip that is greater than 50%. Isolated anterior spinal fusion has not been successful, and direct repair of the pars defect is only useful for spondylolysis without spondylolisthesis. Lenke LG, Bridwell KH: Evaluation and surgical treatment of high-grade isthmic dysplastic spondylolisthesis. Instr Course Lect 2003;52:525-532.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The photomicrograph shows a synovial cell sarcoma with a characteristic histology of a biphasic pattern of pleomorphic spindle cells and well-differentiated cuboidal to columnar cells forming gland-like spaces. The glandular zones contain mucous-like material that stains positively with periodic acid Schiff. Microscopic calcifications are usually found. Synovial cell sarcoma has a high rate of local recurrence as well as metastases. It is the most common malignancy found in the foot. Krall RA, Kostianovsky M, Patchefsky AS: Synovial sarcoma: A clinical, pathological and ultrastructural study of 26 cases supporting the recognition of a monophasic variant. Am J Surg Pathol 1981;5:137-151.

<span class="exp-title">Detailed Explanation</span><div markdown="1">With a full-thickness articular cartilage injury, a healing response is initiated with hematoma, stem cell migration, and vascular ingrowth. This response produces type I collagen and resultant fibrous cartilage rather than desired hyaline cartilage as produced by chondrocytes. This repair cartilage has diminished resiliency, stiffness, poor wear characteristics, and the predilection for arthritis. Type I collagen is also found in the annulus of intervertebral disks, tendon, bone, meniscus, and skin. Type II is found in articular cartilage and nucleus pulposus of intervertebral disks. Type III is found in skin and blood vessels, type IV is found in basement membranes, and type X is found in the calcified layer of cartilage. Arendt EA (ed): Orthopaedic Knowledge Update: Sports Medicine 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 19-28.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has several indications that he is not ready for definitive fixation of the femoral shaft fracture at this point. He is cold with a core temperature of 93 degrees F, and hypothermia of less than 95 degrees F (35 degrees C) has been shown to be associated with an increased mortality rate in trauma patients. The patient has also not been resuscitated based on his increasing lactate levels and although controversial, it has been shown that temporary external fixation leads to a lower incidence of multiple organ failure and acute respiratory distress syndrome. Shafi S, Elliot AC, Gentilello L: Is hypothermia simply a marker of shock and injury severity or an independent risk factor for mortality in trauma patients? Analysis of a large national trauma registry. J Trauma 2005;59:1081-1085. Pape HC, Hildebrand F, Pertschy S, et al: Changes in the management of femoral shaft fractures in polytrauma patients: From early total care to damage control orthopedic surgery. J Trauma 2002;53:452-461.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Intravenous antibiotics alone will not adequately treat this infection. At 8 weeks after surgery, the hardware must be removed because Staphylococcus aureus is a virulent microbe. VAC therapy alone is not adequate without debridement and hardware removal, but it may play a role in postoperative wound care. Calcanectomy is a salvage procedure for calcaneal osteomyelitis or recalcitrant heel ulceration. Benirschke SK, Kramer PA: Wound healing complications in closed and open calcaneal fractures. J Orthop Trauma 2004;18:1-6. Lim EV, Leung JP: Complications of intra-articular calcaneal fractures. Clin Orthop 2001;391:7-16.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The peroneus brevis is easily identified by its location behind the fibula and its distal muscle belly. Axial MRI images provide a reliable guide even when one of the peroneals is completely ruptured, subluxated out of the peroneal groove, or absent. Sarrafian SK: Anatomy of the Foot and Ankle: Descriptive, Topographic, Functional, ed 2. New York, NY, Lippincott, 1993, pp 234-235.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The diagnosis is myositis ossificans resulting from an injury. The initial radiograph reveals a small amount of mineralization in the soft tissues overlying the left hip. The MRI scan shows signal abnormality of the entire gluteus minimus muscle with a mineralized mass in the center. The current radiograph shows a lesion within the abductor musculature with mature ossification peripherally. The imaging studies are diagnostic and the patient is asymptomatic; therefore, the management of choice is observation with no further evaluation or treatment indicated. Miller AE, Davis BA, Beckley OA: Bilateral and recurrent myositis ossificans in an athlete: A case report and review of treatment options. Arch Phys Med Rehabil 2006;87:286-290.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The results are statistically significant (at the arbitrary level of P < 0.05). That is, they indicate a probability of only 1/10,000 that the observation that the drug is effective in reducing healing time by 0.3 weeks occurred by chance selection of the study subjects. However, because the statistical power of a study increases with the number of subjects included (sample size), a difference that is trivial clinically can occur with a very high level of statistical significance (a very small P-value) if enough patients are included in the study. Because of this, the P-value alone, no matter how small, does not establish clinical significance or importance. Rather, the clinical significance of the observed difference must be assessed taking into consideration the medical importance of the difference if it is, in fact, true in the general population. In this example, the reduction in healing time of only a few days is probably clinically unimportant, particularly if the use of the new growth factor is expensive, complex, and/or has substantial side effects.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The five major compartments of the foot are medial, lateral, central, interosseous, and calcaneal. There is no dorsal compartment in the foot. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 262-264.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Corrective osteotomy of fibular malunions, with appropriate lengthening, even in the presence of early arthritis, has been shown to decrease ankle pain and increase stability. Reduction and bone grafting of the medial malleolar nonunion is also needed. There is no evidence supporting the use of intra-articular steroids or hyaluronic acid in the ankle joint. Lateral talar displacement of even 1 mm has been reproducibly shown to decrease tibiotalar contact by 40% to 42%, causing a predisposition to arthritis. Weber D, Friederich NF, Muller W: Lengthening osteotomy of the fibula for post-traumatic malunion: Indication, technique and results. Int Orthop 1998;22:149-152. Lloyd J, Elsayed S, Hariharan K, et al: Revisiting the concept of talar shift in ankle fractures. Foot Ankle Int 2006;27:793-796. Offierski CM, Graham JD, Hall JH, et al: Later revision of fibular malunion in ankle fractures. Clin Orthop Relat Res 1982;171:145-149.

<span class="exp-title">Detailed Explanation</span><div markdown="1">With the arm in the abducted, externally rotated position, the anterior band of the inferior glenohumeral ligament complex moves anteriorly, preventing anterior humeral head translation. Both the coracohumeral ligament and the superior glenohumeral ligament restrain the humeral head to inferior translation of the adducted arm, and to external rotation in the adducted position. The middle glenohumeral ligament is a primary stabilizer to anterior translation with the arm abducted to 45 degrees. The posterior band of the inferior glenohumeral ligament complex resists posterior translation of the humeral head when the arm is internally rotated. 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.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a complex fracture-dislocation of the elbow. The radial head is fractured, and there is a displaced coronoid fracture. These associated fractures indicate that the elbow is at high risk for recurrent instability after initial treatment. To prevent this complication, surgical treatment will most likely be required and will consist of some or all of the following: radial head open reduction and internal fixation or replacement, coronoid open reduction and internal fixation, medial and lateral ligament repairs, and even articulated external fixation. This patient was treated with open reduction and internal fixation of the radial head, and the elbow redislocated postoperatively. Ring D, Jupiter JB: Reconstruction of posttraumatic elbow instability. Clin Orthop 2000;370:44-56. O'Driscoll SW: Classification and evaluation of recurrent instability of the elbow. Clin Orthop 2000;370:34-43.

<span class="exp-title">Detailed Explanation</span><div markdown="1">A patient with an infected total hip arthroplasty may lack the symptoms of fever, chills, redness, or increased warmth typical of septic arthritis. Sensitivity for ESR and CRP ranges from 61% to 96%, and specificity ranges from 85% to 100%. Technetium Tc 99m bone scans are costly and time-consuming and will not differentiate between septic and aseptic loosening. Hip aspiration has a false-positive rate of up to 15%, although it may be useful in this patient to further complement the clinical picture if the ESR and CRP are elevated. The WBC count is rarely elevated in infected total hip arthroplasty. MRI is expensive and is not indicated for the diagnosis; however, it can aid in identifying intrapelvic extension of a periprosthetic abscess. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 455-492.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The work-up for a patient with an unknown primary lesion that is metastatic to bone includes a search for the primary tumor and other sites of metastasis. This involves conducting a thorough history and physical examination, appropriate laboratory studies, bone scan, chest radiograph, and CT of the chest, abdomen, and pelvis. In women, a mammogram may be indicated. CT of the brain is not necessary in the early stages of a metastatic work-up. Simon MA, Bartucci EJ: The search for the primary tumor in patients with skeletal metastases of unknown origin. Cancer 1986;58:1088-1095.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a type IIIB patellar fracture (inferior pole fracture with an intact patellar tendon). Nonsurgical management is the treatment of choice if there is little displacement and the extensor mechanism is intact. Brown TE, Diduch DR: Fractures of the patella, in Insall JN, Scott WN (eds): Surgery of the Knee, ed 3. Philadelphia, PA, Churchill Livingstone, 2001, vol 2, pp 1290-1312.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In the absence of a cauda equina syndrome or progressive weakness, the best indication for surgical management is refractory radicular pain. Surgical decision-making should not be based on the size of the herniation. Large extruded herniations tend to resolve more predictably than smaller herniations. Stable motor weakness and numbness resolve similarly in both surgical and nonsurgical management, although surgery hastens the process. When intractable radicular pain is the strict indication for surgery, surgical intervention provides substantial and more rapid pain relief than nonsurgical care. Rhee JM, Schaufele M, Abdu WA: Radiculopathy and the herniated lumbar disc: Controversies regarding pathophysiology and management. J Bone Joint Surg Am 2006;88:2070-2080.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The os peroneum is an accessory ossicle located within the peroneus longus tendon. It is typically located at the level of the cuboid groove in the lateral hindfoot and midfoot region. Proximal migration of the os peroneum indicates disruption of the peroneus longus tendon and is an important clue to diagnosis. This unusual condition can cause chronic lateral ankle pain, and surgical repair may be indicated. Active eversion indicates that the peroneus brevis is clinically intact. Disruption of the extensor digitorum brevis, plantar fascia, or syndesmosis would have no effect on the position of the os peroneum. Thompson FM, Patterson AH: Rupture of the peroneus longus tendon: Report of three cases. J Bone Joint Surg Am 1989;71:293-295.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Because the patient has chronic pain, a possible lateral recess stenosis of the C7 root, and no neurologic deficits, keyhole foraminotomy is the treatment of choice for decompressing the exiting nerve root and offering an early return to play, especially when using a muscle-splitting posterior approach. Henderson and associates reported excellent results with posterolateral foraminotomy in patients with radicular symptoms. Although anterior cervical diskectomy and fusion is equally effective in the long term, a period of 6 to 12 weeks is required to allow the anterior fusion to heal prior to a return to play. Chen and associates reported that keyhole foraminotomy maintains cervical motion segment dynamics better than compared to anterior limited diskectomy and foraminotomy or anterior diskectomy with fusion. Henderson, CM, Hennessy RG, Shuey HM Jr, Shackelford EG: Posterior-lateral foraminotomy as an exclusive operative technique for cervical radiculopathy: A review of 846 consecutively operated cases. Neurosurgery 1983;13:504-512. Dillin W, Booth R, Cuckler J, Balderston R, Simeone F, Rothman R: Cervical radiculopathy: A review. Spine 1986;11:988-991.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The meniscofemoral ligaments connect the posterior horn of the lateral meniscus to the intercondylar wall of the medial femoral condyle. The ligament of Humphrey (arrow) passes anterior to the posterior cruciate ligament, whereas the ligament of Wrisberg passes posterior to the posterior cruciate ligament. One or the other has been identified in 71% to 100% of cadaver knees, with the ligament of Wrisberg being more common. Clarke HD, Scott WN, Insall JN, et al: Anatomy, in Insall JN, Scott WN (eds): Surgery of the Knee, ed 4. Philadelphia, PA, Churchill Livingstone, 2006, vol 1, pp 3-66.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The most common anatomic location of chondrosarcoma is the pelvis (30%), followed by the proximal femur (20%). Chondrosarcomas appear in the shoulder girdle in 15% of patients but rarely affect the spine or hands. Marcove RC, Mike V, Hutter RV, et al: Chondrosarcoma of the pelvis and upper end of the femur: An analysis of factors influencing survival time in one hundred and thirteen cases. J Bone Joint Surg Am 1972;54:561-572.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The dynamic forces acting to maintain the position of the proximal phalanx at the head of the metatarsal are a balance between the extensor digitorum longus and the weaker intrinsic muscles. With hyperextension at the metatarsophalangeal joint, the intrinsic muscles become less efficient as plantar flexors. Consequently, the hyperextension deformity progresses in the metatarsophalangeal joint as the opposition of the intrinsic muscles to the extensor tendon lessens. This is in contrast to the situation in the interphalangeal joints, where the stronger flexors overpower the weaker intrinsic muscles, which act as the extensors. This combination of events leads to hyperextension at the metatarsophalangeal joint and flexion deformities at the interphalangeal joints, resulting in claw toe. Mizel MS, Yodlowski ML: Disorders of the lesser metatarsophalangeal Joints. J Am Acad Orthop Surg 1995;3:166-173.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has diskitis. Administration of IV antibiotics speeds resolution and minimizes recurrence. Bed rest and cast immobilization have been successfully used to treat this disorder but can be associated with prolonged recovery and frequent recurrence, even when oral antibiotics are administered. A perivertebral abscess seen in association with this condition usually resolves without surgery. Ring D, Johnston CE II, Wenger DR: Pyogenic infectious spondylitis in children: The convergence of discitis and vertebral osteomyelitis. J Pediatr Orthop 1995;15:652-660.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Pelvic trauma in women has been shown to increase the risk of sexual dysfunction and dyspareunia. Additionally, caesarean section childbirth is almost universal following pelvic trauma regardless of whether anterior pelvic hardware is present or not. Copeland CE, Bosse MJ, McCarthy ML et al: Effect of trauma and pelvic fracture on female genitourinary, sexual, and reproductive function. J Orthop Trauma 1997;11:73-81.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The lower extremity symptoms are consistent with a sympathectomy that is the result of an injury to the sympathetic chain, ipsilateral to the approach along the anterior border of the lumbar spine. This results in a warm, red foot, which creates the appearance that the normal cooler foot may have compromised circulation. The latter generally attracts greater attention because of the risks associated with limb ischemia. The condition usually is self-limited and does not require any specific treatment. Rothman RH, Simeone FA (eds): The Spine, ed 4. Philadelphia PA, WB Saunders, 1999, p1550.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Bilateral flattening of the femoral heads suggests multiple epiphyseal dysplasia; therefore, a skeletal survey is indicated to look for involvement of other epiphyses. Unilateral flattening of the femoral head would suggest Legg-Perthes disease. Sponseller PD: Skeletal dysplasias, in Morrissy RT, Weinstein SL (eds): Lovell and Winter's Pediatric Orthopaedics, ed 5. Philadelphia, PA, Lippincott Williams & Wilkins, 2001, pp 269-270.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Manipulative treatment and casting of talipes equinovarus has become popular because of disappointing surgical results and enthusiasm for the Ponseti method of manipulation. In this technique, the primary goal is to rotate the foot laterally around a talus that is held fixed by the manipulating surgeon's hands. While the navicular may be rotated anterolaterally with this technique, the primary focus is on the calcaneus. The calcaneus is rotated laterally and superiorly, not translated. Some dorsiflexion of the calcaneus can be obtained by manipulation, but the primary focus is on the rotational relationship of the talus and calcaneus, not the degree of calcaneal dorsiflexion. Ponseti IV: Common errors in the treatment of congenital clubfoot. Int Orthop 1997;21:137-141.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The arthroscopic image shows a tear through more than 50% of the biceps tendon; therefore, treatment should consist of tenodesis or tenotomy of the tendon. However, because this patient is relatively young and active, the treatment of choice is tenodesis of the biceps tendon. Sethi N, Wright R, Yamaguchi K: Disorders of the long head of the biceps tendon. J Shoulder Elbow Surg 1999;8:644-654. Eakin CL, Faber KJ, Hawkins RJ, et al: Biceps tendon disorders in athletes. J Am Acad Orthop Surg 1999;7:300-310.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Severe osteoporosis is a contraindication to manipulation under anesthesia in patients with a resistant frozen shoulder because of the higher risk of humeral fracture. Manipulation is considered for frozen shoulder in patients who are symptomatic despite undergoing a reasonable course of appropriate physical therapy. Harryman DT II: Shoulder: Frozen and stiff. Instr Course Lect 1997;42:247-257.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Sudden death during total hip arthroplasty has been reported. In a report from the Mayo Clinic, intraoperative death occurred during cemented total hip arthroplasty in 23 patients. Fat and marrow embolization during preparation of the femur or cementing of the femoral component was believed to be responsible for the cardiopulmonary collapse that occurred during arthroplasty. Although fat and marrow emboli were found in the pulmonary capillaries of most of the patients on autopsy, this histologic section shows two particles of cement in the pulmonary capillaries. Parvizi J, Holiday AD, Ereth MH, et al: The Frank Stinchfield Award. Sudden death during primary hip arthroplasty. Clin Orthop 1999;369:39-48.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The figures show an open tibial fracture, a femoral shaft fracture, and femoral head dislocation. The most urgent treatment is reduction of the femoral head, as timing to reduction has been correlated with preventing osteonecrosis. After reduction of the femoral head, the next priority is wound management, followed by stabilization of the femoral and tibial fractures with either splinting, traction, or external fixation. Sahin V, Karakas ES, Aksu S, et al: Traumatic dislocation and fracture-dislocation of the hip: A long-term follow-up study. J Trauma 2003;54:520-529.

<span class="exp-title">Detailed Explanation</span><div markdown="1">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.

<span class="exp-title">Detailed Explanation</span><div markdown="1">This is a classic situation for a distal phalanx tuft fracture with associated nail bed injury and subungual hematoma. In general, when the subungual hematoma is greater than 50% of the surface area under the nail plate, treatment should consist of nail plate removal, nail bed repair, oral antibiotics, and a fingertip splint. Oral antibiotics and fingertip splinting alone do not address the nail bed laceration, which will most likely lead to nail plate deformity if not repaired. Kirschner pin stabilization is not indicated because these fractures are nondisplaced and usually are inherently stable after nail bed repair. The use of IV antibiotics alone does not address the nail bed laceration surgically. Casting, followed by hydrotherapy and topical antibiotics, is not indicated because it does not address the nail bed laceration. Further, a nondisplaced distal phalangeal tuft fracture does not require cast immobilization. Stern PJ: Fractures of the metacarpals and phalanges, in Green DP, Hotchkiss RN, Pederson WC (eds): Green's Operative Hand Surgery, ed 4. Philadelphia, PA, 1999, pp 711-771.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Heat stroke consists of hyperthermia (greater than 105.8 degrees F [41 degrees C]), central nervous system dysfunction, and cessation of sweating with hot, dry skin. It is a medical emergency that results from failure of the thermoregulatory mechanisms of the body. It has a high death rate and requires rapid reduction in body core temperature. Heat syncope is characterized by a transient loss of consciousness with peripheral vasodilation and decreased cardiac output with normal body temperature. Heat cramps involve painful contractions of large muscle groups because of decreased hydration and a decrease of serum sodium and chloride. Heat exhaustion is distinguished by a core temperature of less than 102.2 degrees F (39 degrees C) and an absence of central nervous system dysfunction. Hypernatremic heat exhaustion results from inadequate water replacement. Knochel JP: Environmental heat illness: An eclectic review. Arch Intern Med 1974;133:841-864. Hubbard RW, Gaffin SL, Squire DL: Heat related illness, in Wilderness Medicine, ed 3. St Louis, MO, Mosby, 1995, p 167.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The superior gluteal nerve is located approximately 7.82 cm above the tip of the greater trochanter as it courses through the gluteus medius. This anatomic consideration is relevant during a Hardinge approach to the hip, where excessive proximal dissection or retraction could result in nerve injury. A split of the gluteus medius of no more than 4 cm above the greater trochanter is considered safe. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, pp 333-335.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Although there is strong clinical and laboratory evidence that suggests smaller head size is linked with lower rates of polyethylene wear, moving to the use of 22-mm heads from larger sizes would tend to increase the dislocation rate. The key premise to this argument is that the absolute size of the femoral neck remains unchanged. While neck diameters were appropriate for the early monoblock femoral components, the use of modular femoral stems allows the surgeon to place 22-mm heads onto the same neck and trunion as used by larger heads. This has the effect of lessening the head-to-neck diameter ratio, which then accentuates the rate of impingement and dislocation. Reducing the neck diameter in proportion to the head diameter would eliminate the range-of-motion penalty accompanying head size reduction. Scifert and associates used a three-dimensional finite element model to study various combinations of femoral head size and neck ratios. They found that increasing the diameter of the femoral head while maintaining a constant head-to-neck diameter had the effect of significantly increasing the resisting moment necessary to induce a dislocation. The higher the head-to-neck ratio, the greater the range of motion until impingement and the greater the range of motion to dislocation.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Developmental dysplasia of the hip (DDH) leads to early arthritis of the hip as seen in this patient. Although DDH is believed to mostly affect the acetabulum, most patients with DDH also have anatomic aberrations of the femur. Using three-dimensional computer models generated by reconstruction of CT scans, dysplastic femurs were shown to have shorter necks and smaller, straighter canals than the controls. The shape of the canal became more abnormal with increasing subluxation. The studies also have shown that the primary deformity of the dysplastic femur is rotational, with an increase in anteversion of 5 degrees to 16 degrees, depending on the degree of subluxation of the hip. The rotational deformity of the dysplastic femur arises within the diaphysis between the lesser trochanter and the isthmus and is not attributable to a torsional deformity of the metaphysis. Osteopenia is not a concern in a patient with an excellent cortical index (thick cortices and narrow canal). Femoral varus or bowing of the femur is not a typical finding in patients with DDH. Noble PC, Kamaric E, Sugano N, et al: Three-dimensional shape of the dysplastic femur: Implications for THR. Clin Orthop 2003;417:27-40.

<span class="exp-title">Detailed Explanation</span><div markdown="1">A volar lunate fragment of a distal radial fracture is considered a critical component to overall joint stability and function. Obtaining a reduction is difficult through a standard volar approach to the radius between the flexor carpi radialis and radial artery. Visualization and reduction of the ulnar volar facet is not possible from this approach. An extended carpal tunnel incision provides access to the entire articular surface, except for the distal radial styloid component. Hanel DP, Jones MD, Trumble TE: Wrist fractures. Orthop Clin North Am 2002;33:35-57.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The history and MRI findings indicate the presence of anterior tibiotalar osteophytes. This is frequently observed in soccer, rugby, and football athletes who play on grass or turf surfaces and repetitively push off and change directions. Examination may reveal an effusion but no loss of subtalar motion. A positive external rotation (Klieger) test is described as pain at the distal ankle with external rotation of the foot and is observed in patients with syndesmosis sprains. This patient may have an increased anterior drawer because of a history of sprains; however, this finding is not specific for anterior impingement of tibiotalar osteophytes. The most specific finding on physical examination is pain with forced dorsiflexion. Ogilvie-Harris DJ, Mahomed N, Demaziere A: Anterior impingement of the ankle of the ankle treated by arthroscopic removal of bony spurs. J Bone Joint Surg Br 1993;75:437-440.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The radiograph shows an osteolytic eccentric lesion in the metaphyseal-diaphyseal region of the bone, and the photomicrographs show an aneurysmal bone cyst. The low-power photomicrograph shows large empty spaces with fibrous stroma and multinucleated giant cells. The red area in the center is hemorrhage in the stroma. The large empty spaces are cysts, which would be filled with blood in vivo. The medium-power photomicrograph shows a large cyst-like space and hemorrhage in the surrounding stoma. Giant cell tumors have "sheets" of giant cells. A nonossifying fibroma would have spindle cells, and a unicameral bone cyst may have a few giant cells, but blood is rare. Springfield DS, Gebhardt MC: Bone and soft tissue tumors, in Morrissy RT, Weinstein SL (eds): Lovell and Winter's Pediatric Orthopaedics, ed 5. Philadelphia, PA, Lippincott Williams and Wilkins, 2001, pp 540-542.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Impaction grafting is an alternative for severe femoral bone deficiency; however, stem subsidence is commonly observed during the first few months. Slight subsidence is felt to be integral to the success of the procedure. Predictable bone graft incorporation and stable stem fixation have been reported in the medium-term. The incidence of periprosthetic fractures has been reported as high as 24%. Mikhail MWE, Weidenhielm L, Jazrawi LM, et al: Collarless, polished, tapered stem failure. J Bone Joint Surg Am 2000;82:1513-1514.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The appropriate staging studies should consist of MRI and a radiograph of the primary lesion and CT of the chest. MRI is superior to CT for soft-tissue imaging. CT may be useful for evaluating the cortex of bone for invasion by tumor. Bone scans are not commonly used because soft-tissue sarcomas rarely metastasize to bone. CT of the abdomen and pelvis is not typically ordered except for possible liposarcoma. With liposarcoma, there may be a synchronous or metastatic retroperitoneal liposarcoma. Demetri GD, Pollock R, Baker L, et al: NCCN sarcoma practice guidelines: National Comprehensive Cancer Network. Oncology (Huntingt) 1998;12:183-218.

<span class="exp-title">Detailed Explanation</span><div markdown="1">A recent review of 200 consecutive distal radius fractures noted that the overall incidence of extensor pollicis longus rupture was 3%. The causes are believed to be mechanical irritation, attrition, and vascular impairment. The fracture is usually nondisplaced and the patient notes weeks to months after injury the sudden, painless inability to extend the thumb. Treatment involves extensor indicis proprius tendon transfer or free palmaris longus tendon grafting. Skoff HD: Postfracture extensor pollicis longus tenosynovitis and tendon rupture: A scientific study and personal series. Am J Orthop 2003;32:245-247. Bonatz E, Kramer TD, Masear VR: Rupture of the extensor pollicis longus tendon. Am J Orthop 1996;25:118-122.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Prosthetic shoulder arthroplasty has been shown to provide predictable results for treating stage III and stage IV osteonecrosis of the humeral head. The decision to resurface the glenoid (total shoulder arthroplasty versus humeral hemiarthroplasty) usually is made based on the radiographic and intraoperative appearance of the glenoid. Core decompression of the humeral head has been reported to be effective for earlier stages (pre collapse) but would not be appropriate for a patient with stage IV disease. Hattrup SJ, Cofield RH: Osteonecrosis of the humeral head: Results of replacement. J Shoulder Elbow Surg 2000;9:177-182. L'Insalata JC, Pagnani MJ, Warren RF, et al: Humeral head osteonecrosis: Clinical course and radiographic predictors of outcome. J Shoulder Elbow Surg 1996;5:355-361.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Chronic anterior inferior tibiofibular ligament sprains can lead to thickening and synovitis that catches or impinges dorsiflexion; patients often note painful clicking with dorsiflexion eversion. The other structures are not affected by this injury. Hopkinson WJ, St Pierre P, Ryan JB, Wheeler JH: Syndesmosis sprains of the ankle. Foot Ankle 1990;10:325-330. Amendola A: Controversies in diagnosis and management of syndesmosis injuries of the ankle. Foot Ankle 1992;13:44-50. Baxter DE: The Foot and Ankle in Sports. St Louis, MO, Mosby-Year Book, 1995, p 30.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The MRI scans clearly show an extruded L4-5 disk that is affecting the L5 root on the left side. In addition, the L5 root has a cutaneous distribution in the first dorsal web space. S1 affects the lateral foot, and L4 affects the medial calf. An HS: Principles and Techniques of Spine Surgery. Baltimore, MD, Williams and Wilkins, 1998, pp 98-100.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Despite the negative radiographic findings, the child's age and presentation are most consistent with a toddler's fracture. There is often not a witnessed injury. The differential diagnosis of infection is unlikely given that the child is afebrile and shows no signs of illness. Immobilization will make the child more comfortable and will often allow weight bearing. Repeat radiographs at the end of treatment will show a healing fracture and confirm the diagnosis. Aspiration of the tibial metaphysis would be indicated to obtain material for culture. The bone scan and MRI would show abnormalities, but these studies are nonspecific, costly, and time-consuming. Occasionally, oblique radiographs will show the fracture. Halsey MF, Finzel KC, Carrion WV, Haralabatos SS, et al: Toddler's fracture: Presumptive diagnosis and treatment. J Pediatr Orthop 2001;21:152-156.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Absolute toe pressures greater than 40 to 50 mm Hg are a good sign of healing potential. An ABI of greater than 0.45 favors healing, but indices greater than 1 are falsely positive due to calcifications in the vessels. Normal albumin is an overall indication of nutritional status. A transcutaneous oxygen level should be greater than 40 mm Hg for healing. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 113-122.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The primary change that takes place in the aging spine is degeneration of the lumbar disks and loss of the overall lumbar lordosis. This also may be associated with osteopenic-related compression fractures. With these changes, the sagittal vertical line moves anteriorly relative to the sacrum; cervical scoliosis is uncommon and not part of the normal aging process. Overall kyphosis in the thoracic spine gradually increases, but the coronal balance remains essentially the same unless scoliosis develops. Gelb DE, Lenke LG, Bridwell KH, et al: An analysis of sagittal spinal alignment in 100 asymptomatic middle and older aged volunteers. Spine 1995;20:1351-1358.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Injuries to the ulnar collateral ligament of the MCP joint of the thumb commonly occur in recreational skiers. Historically, this injury has been referred to as "gamekeeper's thumb." The ligament consists of the proper collateral ligament and the more volar accessory collateral ligament. In extension, the accessory ligament is taut, and in flexion, the proper ligament is taut. For a complete tear of the ligament complex to occur, there must be laxity in full extension. Incomplete tears respond well to thumb spica splinting or casting for 2 to 3 weeks and gradual resumption of range of motion. Prolonged immobilization of incomplete injuries leads to higher rates of MCP joint stiffness. Stener B: Displacement of the ruptured ulnar collateral ligament of the metacarpo-phalangeal joint of the thumb: A clinical and anatomical study. J Bone Joint Surg Br 1971;44:869.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Schwannomas (neurilemomas) occur at all ages but are most frequently seen in persons between the ages of 20 and 50 years. MRI features of schwannomas are fairly nonspecific, but when they are associated with a large named nerve, the identification of a mass in continuity with that nerve is highly suggestive of a schwannoma. Most have a fairly homogeneous appearance with a high water content and often fusiform shape. Classically, the histology shows alternating Antoni A (dense spindle cell region) areas and Antoni B (loose myxoid tissue) areas. They also demonstrate uniform intense immunostaining with S-100 protein. Damron TA, Sim FH: Soft-tissue tumors about the knee. J Am Acad Orthop Surg 1997;5:141-152.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Because the radiographs reveal poor regenerate bone, especially anteriorly and laterally, the first step in management is to slow the distraction rate. If this does not solve the problem, temporary reversal of the distraction, or "accordionization," can be used to induce a greater healing response. Maintaining the same distraction rate will further impair regenerate formation and delay healing. Bone grafting should be reserved as an option if decreasing the distraction rate or alternating a week of compression with a week of distraction fails to improve the callus formation. Repeat corticotomy is performed in patients with premature consolidation. Raney EM: Limb-length discrepancy, in Fitzgerald RH, Kaufer H, Malkani AL (eds): Orthopaedics. St Louis, MO, Mosby, 2002, pp 1519-1526.