100 Orthopedic MCQs: Trauma, Spine, Adult Recon & Sports Medicine | Comprehensive Board Review

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.

The dial or spherical osteotomy leaves the medial wall or teardrop in its original position and, as a result, is intra-articular. The other pelvic osteotomies (except Chiari) redirect the acetabulum, including the medial wall. The Chiari osteotomy improves coverage without redirecting the acetabulum within the pelvis, and it leaves the teardrop in the same place. Lack W, Windhager R, Kutschera HP, Engel A: Chiari pelvic osteotomy for osteoarthritis secondary to hip dysplasia: Indications and long-term results. J Bone Joint Surg Br 1991;73:229-234. Ganz R, Klaue K, Vinh TS, Mast JW: A new periacetabular osteotomy for the treatment of hip dysplasias: Technique and preliminary results. Clin Orthop 1988;232:26-36.

Patients with peripheral neuropathy will often initially see an orthopaedic surgeon and report symptoms of burning, numb, dead, or wooden feet. A simple diagnostic evaluation with a tuning fork (to test vibratory sensibility) or use of the Semmes-Weinstein monofilaments will help make the diagnosis. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 113-121.

Type II collagen in articular cartilage is amazingly stable. This is important to know because matrix homeostasis generally is associated with minimal synthesis and degradation of type II collagen. Passive glycation has a consistent rate and occurs over decades. The relative amount of glycation in cartilage with age has been used as a measure of stability. Also, the rate of racemization of aspartic acid from the L to D form occurs spontaneously at a very slow rate. The relative stability of collagen can be estimated by calculating the percentage of D aspartic acid per dry weight of type II collagen. Maroudas A, Palla G, Gilav E: Racemization of aspartic acid in human articular cartilage. Connect Tissue Res 1992;28:161-169.

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

Cervical myelopathy involves compression of the spinal cord and presents as an upper motor neuron disorder. Patients commonly have extremity spasticity and problems with ambulation and balance. Hoffman's sign is often present and is elicited by suddenly extending the distal interphalangeal joint of the middle finger; reflexive finger flexion represents a positive finding. The extremities are usually hyperreflexic with myelopathy. With cervical radiculopathy (lower motor neuron disorder), reflexes are hyporeflexic, and patients report pain along a dermatomal distribution. A hyperactive jaw jerk reflex indicates pathology above the foramen magnum or in some cases, systemic disease. Flaccid paraparesis suggests a lower motor neuron problem. Sachs BL: Differential diagnosis of neck pain, arm pain and myelopathy, in Clark CR (ed): The Cervical Spine, ed 3. Philadelphia, PA, Lippincott Raven, 1998, pp 741-742.

Basilar invagination is best defined as vertical or compressive instability at the occiput-C1 joint. Such invaginations most commonly occur in patients with rheumatoid arthritis but also can occur secondary to trauma or tumor. A Chamberlain line is used as a method to determine basilar invagination. The odontoid tip should not be more than 5 mm above a Chamberlain line. Wiesel SW, Rothman RH: Occipito-atlantal hypermobility. Spine 1979;4:187-191.

Diminished hip abduction can occur in normal children and is not always associated with hip pathology; therefore, initial management should consist of observation.

Successful antibiotic treatment of osteomyelitis should lead to a rapid decline in the CRP. The CRP should decline after 48 to 72 hours of appropriate treatment. Imaging studies will take much longer to show resolution of bone infection. Unkila-Kallio L, Kallio MJ, Eskola J, et al: Serum C-reactive protein, erythrocyte sedimentation rate, and white blood cell count in acute hematogenous osteomyelitis of children. Pediatrics 1994;93:59-62.

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

Continuous fluoroscopy and cine radiography expose the patient and personnel to markedly increased levels of direct and scatter radiation exposure. Continuous fluoroscopy should be limited to only what is absolutely needed for safe completion of the procedure. By orienting the cathode ray tube beneath the patient and placing the image intensifier as close as clinically possible to the patient, scatter radiation exposure to the personnel is minimized.

An increased density of the talar body compared to the distal tibia following fracture of the talar neck is highly suggestive of vascular compromise of the talar body. Subchondral osteopenia of the talus at 6 to 8 weeks (Hawkins sign) is a favorable sign but does not eliminate the possibility of osteonecrosis. Elgafy H, Ebraheim NA, Tile M, Stephen D, Kase J: Fractures of the talus: Experience of two level 1 trauma centers. Foot Ankle Int 2000;21:1023-1029.

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.

This is a typical presentation of the patellar clunk syndrome. The syndrome usually follows implantation of a posterior stabilized prosthesis. It is thought to be the result of femoral component design and altered extensor mechanics. The condition usually resolves with arthroscopic debridement of the suprapatellar fibrous nodule. Arthrotomy or revision is seldom warranted. Beight JL, Yao B, Hozack WJ, Hearn SL, Booth RE Jr: The patellar "clunk" syndrome after posterior stabilized total knee arthroplasty. Clin Orthop 1994;299:139-142.

Incomplete corticotomy may result from osteotomy with limited soft-tissue stripping and exposure. When the patient begins distraction, tension develops at all wire/half-pin and bone interfaces, leading to increasing difficulty in distraction and limb pain. Sudden spontaneous completion of the osteotomy with continued tension applied by the fixator results in acute distraction of the osteotomy with severe pain. Premature consolidation is unlikely this early following the initial surgery. Birch JG, Samchukov ML: Use of the Ilizarov method to correct lower limb deformities in children and adolescents. J Am Acad Orthop Surg 2004;12:144-154.

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.

The patient has a classic type II SLAP tear that will respond best to arthroscopic repair. Labral debridement has been shown to lead to predictably poor results, and biceps tenodesis and tenotomy may be appropriate for an older patient who is not a competitive overhead athlete. Snyder SJ, Karzel RP, Del Pizzo W, et al: SLAP lesions of the shoulder. Arthroscopy 1990;6:274-279.

Stress fractures of the navicular are often seen in running and jumping sports. Whereas most individuals heal with nonsurgical management consisting of 6 weeks of casting, this gymnast has had pain for 1 year and nonsurgical management has failed. Open reduction with bone grafting is the preferred treatment. Quirk RM: Stress fractures of the navicular. Foot Ankle Int 1998;19:494-496.

The radiograph reveals a reverse obliquely subtrochanteric/intertrochanteric fracture. Open reduction and internal fixation should be accomplished with a 95-degree fixed angle device. An intramedullary nail with screw fixation into the head is another possible technique. Either method should correct the varus deformity. Exchange of a high-angled screw and plate device to a longer side plate and bone grafting does not afford any improvement in the mechanical stability. Hardware removal and retrograde intramedullary nailing is not indicated for this level of a proximal femoral injury. Placement of an implantable bone stimulator may change local biologic factors but would not enhance mechanical stability. The patient's femoral head is intact without signs of collapse; therefore, hardware removal, proximal femoral resection, and total hip arthroplasty are not warranted. Haidukewych GJ, Israel TA, Berry DJ: Reverse obliquity fractures of the intertrochanteric region of the femur. J Bone Joint Surg Am 2001;83:643-650.

Conversion TKA following a previous HTO can be successful; however, it is associated with poorer clinical results when compared with other primary TKAs. There is an increased likelihood of poor range of motion that is partially affected by patella infera created from the osteotomy. Patella infera also results in difficulty with surgical exposure. There has been no reported increase in the rate of infection, fracture, or loosening.

The patient appears to be a borderline or unstable surgical patient following her initial trauma and spleenectomy (high base excess and low urine output). She needs continued resuscitation and minimal additional blood loss. This is best accomplished with irrigation and debridement of the ankle, external fixation of the ankle, foot, and femur, and splinting of the forearm. A traction pin for the femoral fracture will not control bleeding as well as an external fixator. Intramedullary nailing of the femur and open reduction and internal fixation of the forearm would be appropriate in patients that are euvolemic and stable. 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. Taeger G, Ruchholtz S, Waydhas C, et al: Damage control orthopedics in patients with multiple injuries is effective, time saving, and safe. J Trauma 2005;59:409-416. Harwood PJ, Giannoudis PV, van Griensven M, et al: Alterations in the systemic inflammatory response after early total care and damage control procedures for femoral shaft fracture in severely injured patients. J Trauma 2005;58:446-452.

The central one third has been established as the watershed zone by angiographic studies, and has been borne out in clinical conditions involving the navicular, such as stress fractures and osteonecrosis. These findings account for the susceptibility to injury at this level. Nunley JA, Pfeffer GB, Sanders RW, et al (eds): Advanced Reconstruction: Foot and Ankle. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 239-242.

The radiograph and MRI scan show osteochondritis dissecans of the capitellum, and the patient's history suggests a loose body. The treatment of choice is arthroscopic removal of the loose body and microfracture of the crater. Excision of the radial head, a cortisone injection, or tennis elbow release does not treat the pathology in the capitellum. Nonsurgical treatment would not relieve the mechanical symptoms of the loose body or promote healing in the crater. Baumgarten TE, Andrews JR, Satterwhite YE: The arthroscopic classification and treatment of osteochondritis dissecans of the capitellum. Am J Sports Med 1998;26:520-530. Jackson DW, Silvino N, Reiman P: Osteochondritis in the female gymnast's elbow. Arthroscopy 1989;5:129-136.

The obturator artery lies closest to the transverse acetabular ligament. The femoral artery is closest to the anterior rim of the acetabulum. No named vessel lies within the substance of the gluteus minimus or superior to the piriformis tendon. The medial femoral circumflex artery lies medial or deep to the quadratus femoris muscle. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach, ed 1. Philadelphia, PA, JB Lippincott, 1984, Figure 7-53, p 346.

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

The CT scans show large cystic lesions in the talus and calcaneus with complete subluxation of the subtalar joint, allowing the calcaneus to slide laterally until it becomes blocked by the fibula. The cause of this subluxation is severe posterior tibial tendon dysfunction. Although no fibular fracture has yet appeared, it can occur with continued stress from the calcaneus. There is, however, a pathologic fracture in the medial calcaneus through a medial degenerative cyst. The joint space is irregular and not symmetrical as would be seen in an inflammatory arthropathy. Cystic lesions are not present in the tibia. No stress fracture is seen in the talus. Coughlin MJ: Sesamoids and accessory bones of the foot, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, pp 437-499.

A concern in the multiply injured patient who has a pulmonary contusion is the potential for further pulmonary compromise because of embolization of marrow, blood clot, or fat during manipulation of the medullary canal. Recent evidence has shown that the presence of a lung injury is the most important determining factor in future deterioration. However, despite the lung injury and its potential consequences, this patient's femur fracture needs stabilization. Because damage control in the multiply injured patient requires a technique that can be performed rapidly and consistently, the treatment of choice is application of an external fixator. By placing two pins above and below the fracture and with longitudinal traction, the fracture is quickly realigned and stabilized. This allows the patient to be resuscitated and treated at a later date when definitive management of the fracture can be carried out. There is little difference between plate fixation and intramedullary nailing. Bosse MJ, MacKenzie EJ, Riemer BL, et al: Adult respiratory distress syndrome, pneumonia, and mortality following thoracic injury and a femoral fracture treated with either intramedullary nailing with reaming or with a plate: A comparative study. J Bone Joint Surg Am 1997;79:799-809. Scalea TM, Boswell SA, Scott JD, Mitchell KA, Kramer ME, Pollak AN: External fixation as a bridge to intramedullary nailing for patients with multiple injuries and with femur fractures: Damage control orthopedics. J Trauma 2000;48:613-623.

The enthusiasm with which dorsal rhizotomy was received led to the broadening of selection criteria with poorer results. The ideal candidate is an ambulatory 4- to 8-year-old child with spastic diplegia who does not use assistive devices or have joint contractures. The child must be old enough to actively participate in the rigorous postoperative physical therapy program. The use of the procedure in an ambulatory 16-year-old patient is less desirable because joint contractures will most likely have developed to a varying degree. The hemiplegic child is best treated by orthopaedic interventions. Oppenheim WL: Selective posterior rhizotomy for spastic cerebral palsy: A review. Clin Orthop 1990;253:20-29. Renshaw TS, Green NE, Griffin PP, Root L: Cerebral palsy: Orthopaedic management. J Bone Joint Surg Am 1995;77:1590-1606.

The patient has a prefractured stage of congenital pseudarthrosis of the tibia and is at risk for fracture. The PTB orthosis may prevent or delay the fracture. Osteotomy is frequently complicated by nonunion. When established nonunion does not respond to intramedullary nailing and bone grafting, vascularized grafting may succeed. Amputation is a salvage procedure. Murray HH, Lovell WW: Congenital pseudarthrosis of the tibia: A long-term follow-up study. Clin Orthop 1982;166:14-20.

The diagnosis is synovial chondromatosis. While the plain radiograph fails to show any calcifications, the MRI scan shows an intra-articular mass that involves the capsule. Grossly multiple granular cartilage nodules are seen. Management should consist of removing all loose bodies along with the synovial membrane.

The patient has a Bado type 2 variant Monteggia fracture with a radial head fracture. The type 2 variant is associated with a higher nonunion rate and poorer outcomes compared to other Bado-type Monteggia fractures. While it is potentially acceptable to repair the radial head, factors such as higher degrees of comminution and older age lead toward replacement as the treatment of choice. Plate and screw fixation is favored over Kirschner wire/tension band fixation because this is not a simple olecranon fracture. Plate placement in a type 2 fracture is dorsal to counteract very high tensile forces associated with fixation failure. Egol KA, Tejwani NC, Bazzi J, et al: Does a Monteggia variant lesion result in a poor functional outcome? A retrospective study. Clin Orthop Relat Res 2005;438:233-238. Jupiter JB, Leibovic SJ, Ribbans W, et al: The posterior Monteggia lesion. J Orthop Trauma 1991;5:395-402.

Posterior sternoclavicular dislocations are commonly associated with tracheal compression, which can be a life-threatening condition requiring immediate reduction. The other listed complications are less common. Brooks AL, Henning GD: Injury to the proximal clavicular epiphysis, abstracted. J Bone Joint Surg Am 1972;54:1347-1348.

The imaging studies show a comminuted lateral talar process fracture. This injury is often missed on plain radiographs; therefore, CT provides the best method of diagnostic evaluation. The most likely long-term sequela of this injury is subtalar joint arthrosis. Although this injury involves the fibular gutter region, progression to true ankle arthritis is unlikely. There does not appear to be any association with this injury and chronic mechanical instability of the ankle or disruption of the superior peroneal retinaculum and subsequent peroneal tendon instability. Entrapment of the flexor hallucis longus tendon may occur with fractures of the sustentaculum tali but not with injuries of the lateral talar process. Surgical management includes open reduction and internal fixation versus excision; the goal is preservation of the large articular surface fragments. In this patient, there is significant comminution and early fragment excision may be the best option for acute treatment. Tucker DJ, Feder JM, Boylan JP: Fractures of the lateral process of the talus: Two case reports and a comprehensive literature review. Foot Ankle Int 1998;19:641-646.

A 32-mm head design results in less linear wear but more volumetric wear particles. Modular components that allow motion between the polyethylene insert and the shell can result in backside wear. The oxidative degradation of gamma-irradiated polyethylene stored in air leads to increased wear. All of these factors lead to a greater particulate load and more osteolysis. Circumferential porous coating blocks ingrowth of particle-laden fluid and decreases osteolysis. Bartel DL, Bicknell VL, Wright TM: The effect of conformity, thickness, and material on stresses in ultra-high molecular weight components for total joint replacement. J Bone Joint Surg Am 1986;68:1041-1051. Fisher J, Hailey JL, Chan KL, et al: The effect of aging following irradiation on the wear of UHMWPE. Trans Orthop Res Soc 1995;20:12.

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.

The patient has a persistent diabetic foot ulcer without evidence of osteomyelitis. He has evidence of a sensory peripheral neuropathy and a concomitant motor neuropathy, leading to a dynamic motor imbalance. Use of a total contact cast would offer a high probability of healing the resistant ulcer but with a high potential for recurrence. Combining the total contact cast with Achilles tendon lengthening allows wound healing without a high risk for recurrence. Excision of the noninfected metatarsal head would make the patient vulnerable to the development of a transfer lesion under one of the remaining metatarsal heads. Robertson DD, Mueller MJ, Smith KE, et al: Structural changes in the forefoot of individuals with diabetes and a prior plantar ulcer. J Bone Joint Surg Am 2002;84:1395-1404.

The patient has end-stage arthritis of the elbow with advanced joint destruction. At this point, nonsurgical management is unlikely to provide much relief of symptoms. Arthroscopic procedures can provide relief, but it is likely to be incomplete and unpredictable. The most reliable surgical option is total elbow arthroplasty. Currently, semiconstrained components are generally preferred because constrained components have been associated with a high rate of early prosthetic loosening. Little CP, Graham AJ, Karatzas G, et al: Outcomes of total elbow arthroplasty for rheumatoid arthritis: Comparative study of three implants. J Bone Joint Surg Am 2005;87:2439-2448.

The standard practice in the pharmacologic treatment of a spinal cord injury in the United States has been the administration of methylprednisolone with an initial bolus of 30 mg/kg followed by 5.4 mg/kg for 24 hours, in accordance with the findings of the second and third National Acute Spinal Cord Injury Studies (NASCIS). Although the studies have subsequently drawn criticism for their methodology and outcomes, it has been generally accepted that beneficial neurologic outcomes were anticipated in patients who were able to start the protocol within 8 hours of their initial injury. Further improvement was noted in patients receiving the methylprednisolone within 3 hours of their injury and continuing an infusion for 48 hours. In this patient, who is outside the 8-hour treatment window, no studies have supported starting the methylprednisolone protocol at this time. Braken MB, Shepard MJ, Holford TR, et al: Administration of methylprednisolone for 24 or 48 hours or tirilazad mesylate for 48 hours in the treatment of acute spinal cord injury: Results of the third National Acute Spinal Cord Injury Randomized Controlled Trial. National Acute Spinal Cord Injury Study. JAMA 1997;277:1597-1604.

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.

Urbaniak and Harvey reported donor site morbidity following free vascularized fibular graft in 198 consecutive patients. At a 5-year follow-up, they reported overall complications in 24% of the patients. The most common complication was a sensory deficit (11.8%), followed by motor weakness (2.7%), flexor hallucis longus contracture (2%), and deep venous thrombosis (less than 1%).

The number one cause of sudden death in the young athlete is myocardial pathology, with hypertrophic cardiomyopathy being most common. Because of cardiac muscle hypertrophy, the ventricular capacity is diminished and can result in decreased cardiac output. During exertional activities, the increased demand may not be able to be met and leads to sudden death. While the other choices can be the cause of sudden death in an otherwise healthy young athlete, their incidence is even more rare. Van Camp SP, Bloor CM, Mueller FO, et al: Nontraumatic sports death in high school and college athletes. Med Sci Sports Exerc 1995;27:641-647. Maron BJ, Shirani J, Pollac LC, et al: Sudden death in young competitive athletes: Clinical, demographic, and pathological profiles. JAMA 1996;276:199-204.

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

The finding of a unilateral absent pedicle is often referred to as a winking owl sign and is a manifestation of pedicle destruction from metastatic disease. As the vertebral body is destroyed from the neoplastic process, it extends into the pedicle and destroys the cortical rim that normally creates the oval ring of the pedicle on an AP image. McLain R, Weinstein J (eds): Rothman-Simeone: The Spine, ed 4. Philadelphia, PA, WB Saunders, 1999, p 1173.

Spondylolysis may develop as a stress fracture resulting from repetitive hyperextension during athletic activities. In young people, the pars interarticularis is thin, the neural arch has not yet reached maximum strength, and the intravertebral disk is less resistant to shear. While clinical symptoms may lead to the suspicion of spondylolysis, radiographic confirmation may be difficult in early cases. Plain radiographs may be negative initially, and the plain MRI scan may not offer good visualization of the pars. A bone scan with SPECT is very sensitive initially. CT scans with regular axial and reverse-gantry angled cuts may help determine the type of fracture and the course of treatment. Congeni J, McCulloch J, Swanson K: Lumbar spondylolysis: A study of natural progression in athletes. Am J Sports Med 1997;25:248-253.

Triplane fractures generally occur in children who are near skeletal maturity. The injury is generally caused by a supination external rotation mechanism. The number of fracture fragments present (two or three) depends on what part of the physes is closed at the time of injury. Articular congruity is the major concern in the management of these injuries since the patient has almost reached skeletal maturity. The goal is to restore articular congruity to minimize the development of posttraumatic arthritis. Vaccaro A (ed): Orthopaedic Knowledge Update 8. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 757-765. Kling TF Jr, Bright RW, Hensinger RN: Distal tibial physeal fractures in children that may require open reduction. J Bone Joint Surg Am 1984;66:647-657.

The photomicrograph demonstrates a wedge-shaped infarct with femoral head collapse; therefore, the diagnosis is osteonecrosis of the femoral head. Perthes disease and osteoarthritis do not involve a wedge-shaped defect. Tuberculosis of the hip joint results in greater destruction of the articular cartilage. Basset LW, Mirra JM, Cracchiolo A III: Ischemic necrosis of the femoral head: Correlation between magnetic resonance imaging and histologic sections. Clin Orthop 1987;223:181-187.

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.

The brachialis muscle typically receives dual innervation. The major portion is innervated by the musculocutaneous nerve. Its inferolateral portion is innervated by the radial nerve. The others listed have single innervation. The anterior approach to the humerus, which requires splitting of the brachialis, capitalizes on this dual innervation.

Bracing for spina bifida paraplegia provides both support and improved function of the movable limb. An orthosis has value in controlling unstable joints. The three-point pressure effect applies a force above and below the joint to prevent it from buckling. A four-point pressure effect is only required for a two-joint system (this patient has problems only at the ankle). A longer lever arm brace and a brace with a greater area of support provide better stability. Finally, a straighter limb, without contracture, applies less pressure to the brace and lessens overload to the skin. Gage JR: An overview of normal walking. Instr Course Lect 1990;39:291-303. Bleck EE: Current concepts review: Management of the lower extremities in children who have cerebral palsy. J Bone Joint Surg Am 1990;72:140-144.

Arthrodesis of the failed infected total knee arthroplasty may be accomplished by external fixation, intramedullary rod fixation, and dual plates and screws. External fixation runs the risk of pin tract infection, although after its removal, there are no metal surfaces left in place. Intramedullary rods have been used successfully in the treatment of infected total knees, although they also leave metal within the region of the infection. The dual plate technique of knee fusion is useful in patients with rheumatoid arthritis who require fusion in the absence of infection because it provides good initial stability and avoids the use of external pins. However, in the face of infection, the large surface area of the screws and plates may serve as a site for bacteria to hide within a glycocalyx and make eradication of the infection almost impossible.

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

Based on the radiographic findings, the patient has a metallic foreign body in her foot that is consistent with a needle. She has local infection secondary to the continued presence of the foreign body. CT is not necessary to localize the foreign body as it is adequately visualized on the plain radiographs. The infection cannot be adequately treated until the foreign body is removed. Attempted removal of foreign bodies without proper anesthesia and fluoroscopy frequently results in frustration because of the inability to localize the foreign body. Removal in a surgical suite with proper anesthesia and fluoroscopy is the preferred option. Once the foreign body is removed, the local infection will resolve rapidly. Combs AH, Kernek CB, Heck DA: Orthopedic grand rounds: Retained wooden foreign body in the foot detected by computed tomography. Orthopedics 1986;9:1434-1435.

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

Instability following unconstrained elbow arthroplasty occurs in 10% of patients. Subluxation is twice as common as frank dislocation; however, only 20% of these patients undergo revision. Instability following unconstrained elbow arthroplasty can be caused by component malposition or ligament insufficiency. King GJ, Itoi E, Niebur GL, et al: Motion and laxity of the capitellocondylar total elbow prosthesis. J Bone Joint Surg Am 1994;76:1000-1008.

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

The reported failure rate is in the range of 15%, which may be the result of incorrect diagnosis, improper web space selection, or formation of a stump neuroma. Therefore, the procedure should be approached with caution, measures should be taken to ensure that the diagnosis is accurate, and nonsurgical options should be exhausted. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 101-111. Beskin JL: Nerve entrapment syndromes of the foot and ankle. J Am Acad Orthop Surg 1997;5:261-269.

The differential diagnosis includes septic hip and transient synovitis. Both disorders may present with a joint effusion. The increased teardrop distance and loss of range of motion implies that there is excess fluid in the joint. While the other tests can confirm this, only aspiration can characterize the fluid further, thereby indicating the etiology of the effusion. Provided there is enough fluid obtained at aspiration, the joint fluid should be sent for Gram stain, culture, cell count, glucose, and protein studies.

This cuboid compression fracture ("nutcracker" injury) is associated with subtle injury to the Lisfranc complex. This diagnosis must be made to ensure proper treatment.

The indications of bisphosphonate therapy in breast cancer patients range from the correction of hypercalcemia to the prevention of cancer treatment-induced bone loss. Bisphosphonates reduce metastatic bone pain in at least 50% of patients and can reduce the frequency of skeletal-related events by 30% to 40%. Osteonecrosis of the jaw could occur in up to 2.5% of breast cancer patients during long-term bisphosphonate therapy.

Using an infraspinatus-splitting incision allows for excellent exposure of the posterior capsule and minimizes the risk of injury to the axillary nerve which lies inferior to the teres minor in the quadrilateral space. Dreese J, D'Alessandro D: Posterior capsulorrhaphy through infraspinatus split for posterior instability. Tech Shoulder Elbow Surg 2005;6:199-207. Shaffer BS, Conway J, Jobe FW, et al: Infraspinatus muscle-splitting incision in posterior shoulder surgery: An anatomic and electromyographic study. Am J Sports Med 1994;22:113-120.

Long-term survivorship studies have attempted to clarify patient factors related to good outcomes in HTO. One particular study showed that a patient age of less than 50 years was related to good outcomes in those who had good preoperative knee flexion. The same study found no relation between HTO failure and the presence of postoperative infection or deep venous thrombosis. The presence of a lateral tibial thrust is a contraindication to performing this surgery. As expected, good patient selection is critical to obtaining good long-term results with HTO. Naudie D, Borne RB, Rorabeck CH, Bourne TJ: Survivorship of the high tibial valgus osteotomy: A 10- to 22-year followup study. Clin Orthop 1999;367:18-27. Rinonapoli E, Mancini GB, Corvaglia A, Musiello S: Tibial osteotomy for varus gonarthrosis: A 10- to 21-year followup study. Clin Orthop 1998;353:185-193.

The findings are consistent with an osteoblastoma. The radiographs show a bone-forming lesion of the distal humerus. The lesion has an osseous component extending out of the native cortex with a thin sclerotic border. The T2-weighted MRI scan shows the lesion extending anteriorly beyond the native cortex. No fluid-fluid levels are seen. Histology shows large osteoblasts producing osteoid and woven bone. The tissue between the spicules of bone and osteoid contains thin fibrous tissue and capillaries. Osteoid osteoma is a smaller lesion usually with sclerotic reactive bone around a small nidus. The histology differentiates osteoblastoma from osteosarcoma because no malignant cells are seen. There is no cartilage production or chondroblasts in the histologic specimen, eliminating chondroblastoma. Giant cell tumors of bone typically occur in a epiphyseal metaphyseal location, most commonly after skeletal maturity, and contain numerus giant cells. Menendez LR (ed): Orthopaedic Knowledge Update: Musculoskeletal Tumors. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 87-102.

Radiographic abnormalities such as coxa magna, coxa breva secondary to growth arrest, and coxa plana and acetabular deformities are associated with healed Legg-Calve-Perthes disease. Femoral heads that were flat yet congruent with the acetabulum are at risk for disabling arthritis in the sixth decade of life in 50% of these untreated patients. As the normal ball-and-socket joint deforms to a flattened cylinder, the hip loses abduction and rotation capability, while retaining flexion and extension potential. If the femoral head is flat and is not concentric with the acetabulum, early severe arthritis occurs. Hinge abduction and anterior impingement are known sequelae of a flat, incongruent femoral head.

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

Prophylactic stabilization of impending fractures does not directly affect the overall survival rate, but it does improve factors related to intraoperative and postoperative complications and decreased recovery time. Mirels H: Metastatic disease in long bones: A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop 1989;249:256-264.

The radiograph reveals the classic "bump" that is seen in patients with femoroacetabular impingement (FAI). Ganz and associates described two types of FAI. This patient has cam impingement, which describes a nonspherical femoral head being forced into the acetabulum during hip motion and resulting in labral and chondral injury. Hip arthroscopy and labral debridement is unlikely to control the symptoms because the underlying anatomic abnormality is often difficult to address with arthroscopy. The treatment involves surgical dislocation of the hip with preservation of the blood supply to the femoral head, removal of the asphericity on the femoral side (femoral osteoplasty), and removal of the acetabular rim (acetabular osteoplasty) if the latter is found to contribute to impingement. Ganz R, Gill TJ, Gautier E, et al: Surgical dislocation of the adult hip a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001;83:1119-1124. Ganz R, Parvizi J, Beck M, et al: Femoroacetabular impingement: A cause for early osteoarthritis of the hip. Clin Orthop 2003;417:112-120.

Because the patient has sustained a tarsometatarsal injury with midfoot sag, the treatment of choice is a tarsometatarsal arthrodesis. The cause of his flatfoot deformity is secondary to the tarsometatarsal injury and not from posterior tibialis tendon deficiency. Lateral column lengthening, double arthrodesis, and calcaneal osteotomy are not indicated. Although open reduction and internal fixation may be performed late when arthritis is present, these procedures are less likely to succeed. Komenda GA, Myerson MS, Biddinger KR: Results of arthrodesis of the tarsometatarsal joints after traumatic injury. J Bone Joint Surg Am 1996;78:1665-1676.

Gunshot wounds to the spine present relatively little risk of infection in most cases. When there has been an injury to the colon, the risk of infection can be minimized with a 7-day course of broad-spectrum antibiotics. Fragment removal is not indicated. Roffi RP, Waters RL, Adkins RH: Gunshot wounds to the spine associated with a perforated viscus. Spine 1989;14:808-811.

The child has an up-to-date tetanus; therefore, a booster is not recommended. Pseudomonas coverage is most likely not needed because the child was barefoot. It is too early to evaluate for abscess or osteomyelitis with MRI, and a formal debridement is rarely indicated without signs of an abscess or a retained foreign body. Radiographs with soft-tissue penetration should be obtained to check for a retained foreign body. Richardson EG (ed): Orthopaedic Knowledge Update: Foot and Ankle 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 199-205.

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

Combination drugs with activity against both aerobic and anaerobic organisms have been determined to be the best approach. The first-generation cephalosporins do not provide adequate coverage for gram-negative and anaerobic organisms. Gentamicin alone would not provide adequate activity against anaerobes, and there is the risk of renal and auditory toxicity. Pinzur MS, Slovenkai MD, Trepman E: Guidelines for diabetic foot care. Foot Ankle Int 1999;20:695-702.

With a gap of less than 4 cm, a V-Y repair would be appropriate without a tendon transfer. For gaps greater than 5 cm, a lengthening with augmentation is the most appropriate treatment. Therefore, the treatment of choice is an Achilles tendon turndown with flexor hallucis longus tendon transfer. The plantaris tendon is not a strong enough repair, and direct repair is not possible given the large defect in the Achilles tendon. Continued use of the ankle-foot orthosis will not provide adequate relief for this patient.

Pectoralis major ruptures typically occur in avid weightlifters (often on supplements) and typically while bench-pressing. Clinically there is significant discoloration/bruising over the pectoralis and into the axilla. MRI helps confirm the diagnosis and may help determine if the tear is in the muscle belly or at the bone-tendon junction. Bal GK, Basamania CJ: Pectoralis major tendon ruptures: Diagnosis and treatment. Tech Shoulder Elbow Surg 2005;6:128-134.

The patient has a very low T-type acetabular fracture; however, the head is not congruent under the dome so surgical reduction is necessary. The anterior and posterior columns are displaced and will move independent from each other. The extended iliofemoral is the only approach allowing for visualization and reduction of each column. A combined anterior and posterior approach may also be used. The timing of surgery should be within the first 3 weeks of injury to optimize chances of obtaining an accurate reduction because this is an important factor in determining outcome. Letournel E, Judet R (eds): Fractures of the Acetabulum, ed 2. Berlin, Germany, Springer-Verlag, 1991.

Pagnano and associates revised 25 painful primary posterior cruciate-retaining total knee arthroplasties for flexion instability. The patients shared typical clinical presentations that included a sense of instability without frank giving way, recurrent knee joint effusion, soft-tissue tenderness involving the pes anserine tendons and the retinacular tissue, posterior instability of 2+ or 3+ with a posterior drawer or a posterior sag sign at 90 degrees of flexion, and above-average motion of the total knee arthroplasty. Twenty-two of the knee replacements were revised to posterior stabilized implants, and three underwent tibial polyethylene liner exchange only. Nineteen of the 22 knee replacements revised to a posterior stabilized implant showed marked improvement after the revision surgery. Only one of the three knee replacements that underwent tibial polyethylene exchange was improved. Flexion instability can be a cause of persistent pain and functional impairment after posterior cruciate-retaining total knee arthroplasty. Revision surgery that focuses on balancing the flexion and extension spaces, in conjunction with a posterior stabilized knee implant, seems to be a reliable treatment for symptomatic flexion instability after posterior cruciate-retaining total knee arthroplasty.

The history, examination, and MRI scan findings are consistent with a midsubstance partial rupture of the rectus femoris muscle. This is an injury masquerading as a "pseudo tumor." The lack of an appreciable mass effect on the T1-weighted MRI scan, the defined fluid signal on the T2-weighted scans, and the lack of significant contrast enhancement after gadolinium are all most consistent with injury rather than a neoplasm. Most of these injuries respond to nonsurgical management; a few will benefit from late debridement and repair if symptoms fail to resolve in 3 to 6 months. The treatment of choice is nonsurgical management with a follow-up MRI scan to verify that the findings are resolving. Hughes C IV, Hasselman CT, Best TM, et al: Incomplete, intrasubstance strain injuries of the rectus femoris muscle. Am J Sports Med 1995;23:500-506.

The patient has chronic tibial osteomyelitis that is due to low virulent bacteria. The history and studies do not suggest the need for an amputation or a free-flap procedure. This is a localized tibial infection that is in a healed bone; there is no need to resect the entire area of the tibia bone around the infection. The most appropriate treatment is curettage, debridement of nonviable bone, and placement of absorbable antibiotic beads, followed by a course of IV antibiotics from 1 to 4 weeks and a 6-week course of oral antibiotics. Studies have shown that in cases of localized osteomyelitis that are of low virulence, as little as 1 week of IV antibiotics followed by 6 weeks of oral antibiotics is successful. Patzakis MJ, Zalavras CG: Chronic posttraumatic osteomyelitis and infected nonunion of the tibia: Current management concepts. J Am Acad Orthop Surg 2005;13:417-427.

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

The ratio of displacement from CD to AB normally equals 1.0. If the ratio is greater than 1.0, an anterior atlanto-occipital dislocation may exist. Ratios slightly less than 1.0 are normal except in posterior dislocations, fractures of the odontoid process or ring of the atlas, or congenital abnormalities of the foramen magnum. In these conditions, the ratio may approach 0.7. Powers B, Miller MD, Kramer RS, et al: Traumatic anterior atlanto-occipital dislocation. Neurosurgery 1979;4:12-17.

Open clavicular fractures are rare and result from high-energy trauma. In a series of 20 patients with open clavicular fractures, 13 (65%) sustained a closed head injury. Fifteen (75%) had associated pulmonary injuries and 35% had a cervical or thoracic spine fracture. Only one demonstrated scapulothoracic dissociation. Screening for pulmonary and closed head injuries should be considered in the setting of traumatic open clavicular fractures.

The most common deleterious side effect of ketamine is increased salivation and tracheobronchial secretions. For this reason, an antisialagogue agent should be given. While lack of sufficient respiratory depression is one of the major advantages of using ketamine, apnea can occur if the drug is given too rapidly intravenously. Emergence phenomena is common in adults but relatively rare in children. Furman JR: Sedation and analgesia in the child with a fracture, in Rockwood CA Jr, Wilkins KE, Beaty JH (eds): Fractures in Children, ed 4. Philadelphia, PA, Lippincott-Raven, 1996, vol 3, pp 62-63. White PF, Way WL, Trevor AJ: Ketamine: Its pharmacology and therapeutic uses. Anesthesiology 1982;56:119-136.

Split posterior tibial tendon transfers are best performed in patients with spastic cerebral palsy who are between the ages of 4 and 7 years and have flexible equinovarus deformities. Rigid deformities typically require bony reconstruction procedures. Tendon transfers in patients with athetosis are unpredictable. Green NE, Griffin PP, Shiavi R: Split posterior tibial-tendon transfer in spastic cerebral palsy. J Bone Joint Surg Am 1983;65:748-754.

The most common location of osteosarcoma is the knee area (50% to 55%), followed by the proximal humerus and iliac wing. The most commonly involved long bone is the femur (40% to 45%), followed by the tibia (15% to 25%). Within these bones, tumors are typically adjacent to the epiphyses in most patients. The flat bones of the pelvis and spine are less frequently involved. Malawer MM, Sugarbaker PH, Malawer M: Musculoskeletal Cancer Surgery: Treatment of Sarcomas and Allied Diseases. Kluwer Academic Publishers, 2001.

Most humeral fractures will heal with nonsurgical functional brace management. When the initial pain has subsided in a coaptation splint, the patient is converted to a functional brace and allowed to use the arm for activities. The fracture should heal within 6 weeks to 12 weeks with acceptable results. Surgery is indicated if there is vascular injury, open injury, floating elbow, chest injury, bilateral humeral fractures, or if a reduction cannot be obtained or maintained. The surgical treatment of choice is either antegrade reamed locked intramedullary nailing or plate osteosynthesis. Plate osteosynthesis appears to offer better results with respect to union, function, and risk of complications. Schemitsch EH, Bhandari M: Fractures of the humeral shaft, in Browner BD: Skeletal Trauma, ed 3. Philadelphia, PA, WB Saunders, 2003, pp 1481-1511.

The radiograph and intraoperative photograph show osteonecrosis with near complete head loss/collapse. A stemmed implant is more appropriate in this patient because there is very little bone to support a resurfacing implant. In a younger patient, a glenoid implant should be delayed as long as possible because of the eventual need for revision secondary to glenoid loosening and wear, especially in a young active male. The hemiarthroplasty may be converted to a total shoulder arthroplasty in the future. Levy O, Copeland SA: Cementless surface replacement arthroplasty of the shoulder: 5- to 10-year results with the Copeland mark-2 prosthesis. J Bone Joint Surg Br 2001;83:213-221.

Varus position of the stem is most commonly associated with failure of the cemented femoral component because of association with an inadequate cement mantle in the proximal medial and distal lateral zones. An inadequate cement mantle and obesity have been associated with increased loosening but not as frequently as a varus deformity. The influences of gender and osteoporotic bone on the outcome of cemented femoral components have not been established. Maloney WJ III: Primary cemented total hip arthroplasty, in Callaghan JJ, Dennis DA, Paprosky WG, Rosenberg AG (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1995, pp 179-189.

Coxa saltans (snapping hip syndrome) can occur in two forms: external/lateral or interior/medial/anterior. This patient has the external/lateral form. The external/lateral form involves the iliotibial band, tensor fascia, or gluteus medius, which snaps over the greater trochanter. The external form usually can be treated with physical therapy alone; however, several recent studies report satisfactory results with surgical treatment. Faraj and associates reported good results from surgical Z-plasty in a series of 10 patients. White and associates reported good results in a series of 16 patients with 17 hips who underwent surgical release of an external snapping hip. The interior/medial/anterior form can involve the iliopsoas tendon, acetabular labrum, subluxation of the hip, and loose bodies. White RA, Hughes MS, Burd T, et al: A new operative approach in the correction of external coxa saltans: The snapping hip. Am J Sports Med 2004;32:1504-1508. Faraj AA, Moulton A, Sirivastava VM: Snapping iliotibial band: Report of ten cases and review of the literature. Acta Orthop Belg 2001;67:19-23.

The incidence of osteonecrosis following displaced talar neck fractures is most related to the extent of initial fracture displacement. With increasing fracture displacement, the tenuous vascular supply to the talar body is more at risk for damage, thereby increasing the risk of osteonecrosis. Although displaced talar neck fractures have historically been considered a surgical emergency, recent studies have shown that the timing of surgical intervention bears no impact on the development of osteonecrosis. While nicotine use has an influence on fracture healing, it has never been shown to be a factor in osteonecrosis, nor has posterior-to-anterior screw fixation or the quality of fracture reduction. Lindvall E, Haidukewych G, Dipasquale T, et al: Open reduction and stable fixation of isolated, displaced talar neck and body fractures. J Bone Joint Surg Am 2004;86:2229-2234.

When treating thoracolumbar spine fractures, the major advantage of using the TLSO is greater rotational control. Levine AM (ed): Orthopaedic Knowledge Update: Trauma. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1996, pp 347-349. Krompinger WJ, Fredrickson BE, Mino DE, Yuan HA: Conservative treatment of fractures of the thoracic and lumbar spine. Orthop Clin North Am 1986;17:161-170.

Normal articular cartilage is composed of three zones that are based on the shape of the chondrocytes and the distribution of the type II collagen. The tangential zone has flattened chondrocytes, condensed collagen fibers, and sparse proteoglycan. The intermediate zone is the thickest layer with round chondrocytes oriented in perpendicular or vertical columns paralleling the collagen fibers. The basal layer is deepest with round chondrocytes. The tidemark is deep to the basal layer and separates the true articular cartilage from the deeper cartilage that is a remnant of the cartilage anlage, which participated in endochondral ossification during longitudinal growth in childhood. The tidemark divides the superficial uncalcified cartilage from the deeper calcified cartilage and also is the division between nutritional sources for the chondrocytes. The tidemark is the zone in which chondrocyte renewal took place in childhood. The tidemark is found only in joints and not in the cap of an enchondroma. It is seen most prominently in the adult, nongrowing joint.

The possibility of an open joint injury should be considered in any patient who has a small periarticular laceration. Failure to promptly diagnose and treat such injuries may lead to septic arthritis. The diagnosis of an open joint is easily made when there is visible communication of the joint through the traumatic wound, or when intra-articular air is present on a radiograph. In the absence of these findings, the diagnosis of an open joint may be established by the saline load test, in which a volume of saline is injected into the joint under sterile conditions. If fluid extravasates through the traumatic wound, the diagnosis of an open joint is established. Voit and associates used a saline load test in 50 patients with periarticular lacerations suggestive of joint penetration. When they compared the clinical prediction of whether or not the laceration had penetrated the joint and the test results, the authors reported a false-positive clinical result in 39% of patients and a false-negative clinical result in 43%. The authors concluded that the saline load test was valuable in evaluating periarticular lacerations. Voit GA, Irvine G, Beals RK: Saline load test for penetration of periarticular lacerations. J Bone Joint Surg Br 1996;78:732-733.

Transcription factors regulate the activation or repression of cartilage-specific genes. Sox-9, considered a major regulator of chondrogenesis, regulates several cartilage-specific genes during endochondral ossification, including collagen types II, IV, and XI and aggrecan. Li J, Sandell LJ: Transcriptional regulation of cartilage-specific genes, in Rosier RN, Evans C (eds): Molecular Biology in Orthoapedics, Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 21-24.

This patient has shoulder laxity without apprehension. Because there is a wide range of normal laxity in asymptomatic shoulders, the physician should inform the student of these findings, recommend shoulder strengthening exercises, and allow unrestricted sports participation unless symptoms develop. Harryman DT, Sidles JA, Harris SL, Matsen FA III: Laxity of the normal glenohumeral joint: A quantitative in vivo assessment. J Shoulder Elbow Surg 1992;1:66-76. Hawkins RJ, Bokor RJ: Clinical evaluation of shoulder problems, in Rockwood CA Jr, Matsen FA III (eds): The Shoulder. Philadelphia, PA, WB Saunders, 1998, vol 1, p 186. McFarland EG, Campbell G, McDowell J: Posterior shoulder laxity in asymptomatic athletes. Am J Sports Med 1996;24:468-471.

The coupled action of the rotator cuff prevents superior migration and controls anterior and posterior translation by depressing the humeral head. Poppen NK, Walker PS: Normal and abnormal motion of the shoulder. J Bone Joint Surg Am 1976;58:195-201.

The rate of wound complications is significantly increased after total knee arthroplasty in obese patients. Knee scores and the rate of aseptic loosening or patellar subluxation do not appear to be significantly altered. Winiarsky R, Barth P, Lotke P: Total knee arthroplasty in morbidly obese patients. J Bone Joint Surg Am 1998;80:1770-1774. Stern SH, Insall JN: Total knee arthroplasty in obese patients. J Bone Joint Surg Am 1990;72:1400-1404.

In patients with infected implants, treatment usually involves debridement and exchange of the infected components. In rare cases, when there is severe comorbidity and immune system compromise, as there is with this patient, a form of chronic suppression is indicated. This patient's function is quite satisfactory and, even though there is only a 21% to 38% chance of success (Hirawaka as quoted by Mulvey and Thornhill), an attempt at suppression therapy is indicated. The patient must be followed closely to monitor the potential complications of long-term antifungal therapy and to monitor the integrity of the joint, looking for bone or soft-tissue destruction. Because the patient has satisfactory motion and quadriceps strength, no bracing or other assistive device (except for the walker he is now using) is indicated.

It is not uncommon for patients with ankylosing spondylitis to sustain extension-type fractures, most typically of the cervicothoracic junction. These fractures can appear nondisplaced or minimally displaced initially, making them difficult to diagnose. Because there is no mobility between vertebrae, fractures tend to occur more like those of a transverse fracture of a long bone. In addition, the vertebral bodies are vascular and their canals are relatively enclosed, making them vulnerable to epidural bleeding. The MRI scan reveals an epidural hematoma located posteriorly on the cord; therefore, the treatment of choice is surgical evacuation and a posterior laminectomy. Because of the intrinsic instability of such fractures at the time of the laminectomy, internal fixation and stabilization with a posterior fusion is warranted. A simple laminectomy will only increase instability, and control is unlikely with halo vest immobilization. An anterior procedure will not effectively treat the problem given the location of the hematoma. Consideration can be given to methylprednisolone and observation; however, this will not eradicate the problem. Bohlman HH: Acute fractures and dislocations of the cervical spine. J Bone Joint Surg Am 1979;61:1119-1142.

The imaging studies show a permeative lesion of the left hemipelvis with a large soft-tissue mass. The photomicrograph demonstrates a small blue cell tumor with pseudorosettes. The most likely diagnosis is primitive neuroectodermal tumor (Ewing's sarcoma family of tumors). MIC-2 is a highly sensitive and specific marker for this family of tumors. Cytokeratin is an epithelial marker. Vimentin is a mesenchymal marker. Thus, Ewing's sarcomas are cytokeratin negative and vimentin positive. Before discovery of the MIC-2 antigen, PAS and reticulin stains were commonly used to help differentiate Ewing's sarcoma from lymphoma. In contrast to lymphoma, Ewing's sarcomas are typically PAS positive and reticulin negative. Halliday BE, Slagel DD, Elsheikh TE, et al: Diagnostic utility of MIC-2 immunocytochemical staining in the differential diagnosis of small blue cell tumors. Diagn Cytopathol 1998;19:410-416.

Osteopenia, decreased bone mass without fracture risk as defined by the WHO criteria for diagnosis of osteoporosis, is when a woman's T-score is within -1 to -2.5 SD. The T-score represents a comparison to young normals or optimum peak density. The Z-score represents a comparison of BMD to age-matched normals. Measurements of bone mineral density (BMD) at various skeletal sites help in predicting fracture risk. Hip BMD best predicts fracture of the hip, as well as fractures at other sites.

Although pin loosening generally has not been considered a major problem, it has been cited as the most common complication in two published series of halo vest complications. The other possible complications are all significantly less common. Baum JA, Hanley EN Jr, Pullekines J: Comparison of halo complications in adults and children. Spine 1989;14:251-252. Garfin SR, Botte MJ, Waters RL, Nickel VL: Complications in the use of the halo fixation device. J Bone Joint Surg Am 1986;68:320-325.