100 Orthopedic MCQs: Trauma, Spine, Sports & Arthroplasty | Comprehensive ABOS Review Mock Exam

Power analysis is used to determine the minimum number of specimens (sample size) such that, if a difference is found that is large enough to be clinically important, the associated level of statistical reliability will be high enough (ie, the P-value will be small enough) for the investigators to conclude that the difference observed in the study also holds in general. For the statistician to do a power analysis, the investigators must first decide on the minimum difference that they consider to be clinically important, for example, a reduction of 3% in the rate of infection. It is important to recognize that the choice of what constitutes the minimum difference in the rate of infection that is clinically (ie, medically) important cannot and should not be done by the statistician. Rather, this is a clinical-medical issue and must be done by the physician researcher based on a comprehensive assessment of the medical risks and benefits. The power analysis also requires an estimate of the variance in the data, which may be based on previous similar studies, if available. A statistician can then calculate the minimum sample size (number of patients) required such that, if a clinically important difference does, in fact, exist between the full populations, there is a reasonable probability or power (typically 80% to 90%) that a difference this large also will occur between the sample populations at the desired level of statistical significance (usually, but not necessarily, P < 0.05). The other answers refer to types of analyses that are usually conducted after the data are collected.

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

The patient requires an arthrodesis of the first metatarsophalangeal joint because of the abnormal neuromuscular forces. The more traditional bunionectomies such as a distal chevron bunionectomy, a proximal first metatarsal osteotomy, and a double osteotomy have a high failure rate because of the underlying Down syndrome. The Keller procedure is indicated for older, sedentary individuals and has little role in the management of a neuromuscular bunion. Coughlin MJ, Abdo RV: Arthodesis of the first metatarsophalangeal joint with Vitallium plate fixation. Foot Ankle Int 1994;15:18-28.

Muscle contractions can be classified by tension, length, and velocity. Isometric contractions involve changing tension in the muscle while the muscle stays at a constant length. An example would be pushing against a wall. Isokinetic contractions occur when the muscle maximally contracts at a constant velocity. Isotonic contractions involve constant tension throughout the range of motion. Eccentric contraction is when the muscle lengthens during contraction. Eccentric contractions have the highest risk of injury. Plyometrics are eccentric contractions at a rapid rate. Simon SR (ed): Orthopaedic Basic Science. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1994, pp 89-125.

Patients with significant joint malalignment place increased stresses on the allograft, and this malalignment must be corrected to decrease the likelihood of meniscal allograft failure. None of the other options would lead to failure of the allograft.

The transfemoral approach, also known as the extended trochanteric osteotomy, is an important technique to master for revision hip surgery. When performed correctly, it allows excellent exposure of the femoral canal and aids in exposure of the acetabulum. As demonstrated in the study cited, however, it markedly reduces the torque that the composite can withstand without failure. This type of basic science study is important to guide postoperative rehabilitation.

Following repair of a displaced intra-articular distal humerus fracture, the ability to regain full elbow range of motion is rare. Recent reports of olecranon osteotomy have yielded healing rates of between 95% to 100%. According to McKee and associates, patients can be expected to have residual loss of elbow flexion strength of 25%. McKee MD, Wilson TL, Winston L, et al: Functional outcome following surgical treatment of intra-articular distal humeral fractures through a posterior approach. J Bone Joint Surg Am 2000;82:1701-1707.

Findings in patients with McCune-Albright syndrome include polyostotic fibrous dysplasia, multiple cafe-au-lait spots, and precocious puberty. The bone changes in NF-1 resemble nonossifying fibromas, not fibrous dysplasia. NF-2 has little bony change with typical ocular abnormalities. Paget's disease occurs in older individuals and does not present with cafe-au-lait spots. Ollier's disease (multiple enchondromatosis) may show bone changes but not the other findings. Albright F, Butler AM, Hampton AO, et al: Syndrome characterized by osteitis fibrosa disseminata, areas of pigmentation and endocrine dysfunction with precocious puberty in females. N Engl J Med 1937;216:727-746. Danon M, Robboy SJ, Kim S, Scully R, Crawford JD: Cushing syndrome, sexual precocity, and polyostotic fibrous dysplasia (Albright syndrome) in infancy. J Pediatr 1975;87:917-921.

In patients with an osteomyelitic infection, radiographic findings at 1 to 5 days usually show soft-tissue swelling only. Seven to 14 days after symptoms begin, radiographs will most likely show the classic signs of acute osteomyelitis. Reactive bone formation would be expected by 6 months. Kasser JR (ed): Orthopaedic Knowledge Update 5. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1996, pp 149-161.

The first ossification center to appear in the pediatric elbow is the capitellum. This ossification center generally appears between the first month and the 11th month in girls and between the first month and the 26th month in boys. The other ossification centers in the elbow appear in the following progression: radial head (3.8 to 4.5 years), medial epicondyle (5 to 6 years), olecranon (6 to 7 years), trochlea (9 to 10 years), and the lateral epicondyle (10 years). Wilkins KE, Beaty JH, Chambers HG, et al: Fractures and dislocation of the elbow region, in Rockwood CA, Green DP, Bucholz RW, et al (eds): Rockwood and Green's Fractures in Adults, ed 4. Philadelphia, PA, Lippincott-Raven, 1996, pp 657-662.

The femoral nerve is the most lateral structure in the anterior neurovascular bundle. The femoral artery and vein lie medial to the nerve. Retractors placed in the anterior acetabular lip should be safe, although neurapraxia of the femoral nerve may occur if retraction is prolonged or forceful leading to quadriceps weakness. The femoral artery and nerve are well protected by the interposed psoas muscle. Damage to the lateral femoral cutaneous nerve, causing numbness over the anterolateral thigh, can occur while developing the interval between the tensor fascia latae and sartorious in the anterior (Smith-Petersen) approach but less likely in the Watson-Jones approach. Superior gluteal injury and accompanying abductor insufficiency may occur during excessive splitting of the glutei during the direct lateral (Hardinge) approach. Foot drop secondary to sciatic injury is more common with a posterior exposure or posterior retractor placement. Hoppenfeld S, deBoer P: Surgical Exposures in Orthopaedics: The Anatomic Approach. Philadelphia, PA, JB Lippincott, 1984, p 325.

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

Multidisciplinary treatment combining systemic chemotherapy and adequate surgical resection has resulted in a 5-year survival rate of 70% in patients with nonmetastatic osteosarcoma of the extremity . The advent of effective chemotherapy has increased the overall survival rate from 20% to 70% in current studies. Arndt CA, Crist WM: Common musculoskeletal tumors of childhood and adolescence. N Engl J Med 1999;341:342-352.

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

Deep infections after plating of closed fractures of the forearm are unusual. However, the risk increases with repeat surgeries. Debridement of all infected, nonviable tissue is the initial step in management. The fixation may be retained if it is stable, but if the plate and screws are loose, they should be removed and revision performed after removal of nonviable bone. Either external fixation or repeat plating may be performed. Late infections after fracture union may be treated with plate and screw removal, debridement, and IV antibiotics. Kellam JF, Fischer TJ, Tornetta P III, Bosse MJ, Harris MB (eds): Orthopaedic Knowledge Update: Trauma 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 53-63. Moed BR, Kellam JF, Foster RJ, Tile M, Hansen ST Jr: Immediate internal fixation of open fractures of the diaphysis of the forearm. J Bone Joint Surg Am 1986;68:1008-1017.

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

Poland's syndrome has four main features: 1) short digits as the result of absence or shortening of the middle phalanx; 2) syndactyly of the short digits usually consisting of a simple, complete type; 3) hypoplasia of the hand and forearm; and 4) absence of the sternocostal head of the pectoralis major on the same side. Wilson MR, Louis DS, Stevenson TR: Poland's syndrome: Variable expression and associated anomalies. J Hand Surg 1988;13:880-882.

Pain secondary to an osteochondroma is usually from soft-tissue irritation and bursal formation. This is particularly common for proximal medial tibia osteochondromas that irritate the pes anserine tendons. Malignant degeneration into a chondrosarcoma rarely occurs, is usually associated with multiple hereditary exostoses, and usually occurs after skeletal maturity. Borges AM, Huvos AG, Smith J: Bursa formation and synovial chondrometaplasia associated with osteochondromas. Am J Clin Pathol 1981;75:648-653.

The association of a nail puncture wound with a gram-negative infection (Pseudomonas aeruginosa) has been attributed to the local environmental factors in shoes. Osteomyelitis is rare, occurring only in about 1% of patients. Tetanus prophylaxis should be given if it is not up to date. While the remaining organisms listed are periodically involved, they are more common in patients who are immunocompromised or who have diabetes mellitus. Therefore, obtaining a culture of the infected wound is appropriate in such individuals because of the multifactorial nature of the infection. Green NE, Bruno J III: Pseudomonas infections of the foot after puncture wounds. South Med J 1980;73:146-149.

In patients with facet dislocations and an incomplete neurologic deficit, early decompression of the canal via reduction of the dislocation generally is considered safe if the patient is alert and can cooperate. However, patients who cannot cooperate with serial neurologic examinations during the reduction are at risk for increased deficit secondary to herniated nucleus pulposus, and MRI should be performed prior to either closed or open reduction. Star AM, Jones AA, Cotler JM, et al: Immediate closed reduction of cervical spine dislocations using traction. Spine 1990;15:1068-1072.

Radiation therapy is commonly used as an adjuvant in the treatment of soft-tissue sarcomas, but a controversy exists whether it should be preoperative or postoperative. Radiation therapy can be given prior to or following resection of the tumor. Postoperative radiation is usually given in a higher dose to a larger treatment field. This commonly results in a higher incidence of fibrosis and lymphedema. There is no statistical difference in local recurrence rate between the two radiation treatment plans. Neuropathy is more commonly a complication of chemotherapy. Preoperative radiation therapy has been shown to have a higher wound complication rate than postoperative radiation. Vaccaro AR (ed): Orthopaedic Knowledge Update 8. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2005, pp 197-215.

Mapping of a physeal bar from biplane polytomography or CT helps to identify lesions that should be treated surgically and aids in planning the surgical approach and resection. Criteria for surgical excision are at least 2 years of longitudinal growth remaining and involvement of no more than 50% of the physis. Osteotomy is required if angular deformity is greater than 20 degrees. Although this physeal bar is large, it is slightly less than 50% of the total area of the physis. Limb lengthening in this case should be reserved for failure of bar resection. Physiodesis of the opposite distal tibia at this age would result in disproportionate shortening of both tibiae. Carlson WO, Wenger DR: A mapping method to prepare for surgical excision of a partial physeal arrest. J Pediatr Orthop 1984;4:232-238.

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

The ratio of scapulothoracic to glenohumeral motion with elevation has been shown to vary depending on what portion of elevation is examined, how much load is on the arm, and the technique used to measure increments of elevation. However, almost every study shows that the ratio of scapulothoracic to glenohumeral motion is 1:2 for the contributions over a full range of elevation to 170 degrees. In the first 30 degrees of elevation, there is significant variability in the ratio, and there may be significant variability up to around 60 degrees. Inman VT, Saunders JR, Abbott LC: Observations of the function of the shoulder joint. Clin Orthop 1996;330:3-12.

Diabetes mellitus, obesity, and exposure to steroids have all been associated with the development of Achilles tendinopathy. In addition, Achilles tendinopathy has been associated with a history of hormone replacement therapy and the use of oral contraceptives. Quinolone antibiotics have also been linked to Achilles tendinopathy. Holmes GB, Lin J: Etiologic factors associated with symptomatic Achilles tendinopathy. Foot Ankle Int 2006;27:952-959.

The patient has bilateral subluxated hips, with nearly vertical neck shaft angles; therefore, the treatment of choice is varus derotation osteotomy. Shortening of the bone on one or both sides may be necessary to allow adequate range of motion postoperatively. In patients this age and with this degree of bony deformity, soft-tissue releases are not likely to lead to hip stability. Botulinum toxin has been shown to be effective in the treatment of ankle equinus, but its efficacy in other areas has not been demonstrated as yet. The indications for obturator neurectomy are unclear at present. Proximal femoral resection is a salvage procedure for long-standing hip dislocations that are symptomatic and not reconstructable. Tylkowski CM, Rosenthal RK, Simon SR: Proximal femoral osteotomy in cerebral palsy. Clin Orthop 1980;151:183-192.

There is no evidence of increased polyethylene wear in constrained acetabular components. The rates of wear appear to be the same using standard or constrained liners. Lachiewicz PF, Kelley SS: Constrained components in total hip arthroplasty. J Am Acad Orthop Surg 2002;10:233-238. Anderson MJ, Murray WR, Skinner HB: Constrained acetabular components. J Arthroplasty 1994;9:17-23.

The presence of the relatively long second metatarsal, along with the close approximation of the second and third metatarsal heads, are consistent with second metatarsophalangeal tenosynovitis. The hallmark of initial management is conservative. Modalities include taping, nonsteroidal anti-inflammatory drugs, metatarsal pads, and cortisone injections. Trepman and Yeo combined the use of a cortisone injection with a rocker bottom sole. Mizel and Michelson reported their results using an extended rigid steel shank shoe along with a cortisone injection. Trepman E, Yeo SJ: Nonoperative treatment of metatarsophalangeal joint synovitis. Foot Ankle Int 1995;16:771-777.

In one series, only 44% of patients demonstrated good results from tarsal tunnel decompression if they did not have a mass in the tarsal tunnel. Conditions that produce a traction neuropathy of the posterior tibial nerve are unlikely to respond to neurolysis. The most favorable condition associated with a good response to decompression is when a compressing anatomic structure can be removed from the tarsal tunnel. Frey C, Kerr R: Magnetic resonance imaging and the evaluation of tarsal tunnel syndrome. Foot Ankle 1993;14:159-164. Garrett AL: Poliomyelitis, in Nickel VL (ed): Orthopaedic Rehabilitation. New York, NY, Churchill Livingston, 1982, pp 449-458.

In most patients with symptomatic talocalcaneal coalition involving less than 50% of the subtalar joint, resection with fat graft interposition is preferred over a subtalar or triple arthrodesis, especially if reasonable range of motion can be achieved. This patient has a synchondrosis that is partially cartilaginous. Although patients may have a residual gait abnormality, most report pain relief after surgery. Scranton PE Jr: Treatment of symptomatic talocalcaneal coalition. J Bone Joint Surg Am 1987;69:533-539. Kitaoka HB, Wikenheiser MA, Schaughnessy WJ, et al: Gait abnormalities following resection of talocalcaneal coalition. J Bone Joint Surg Am 1997;79:369-374.

Achieving stability in chronic locked posterior dislocations of the shoulder remains a difficult challenge. Intraoperative measures include decreased humeral retroversion, anterior releases, and posterior capsular tightening. Postoperative rehabilitation is of equal importance. Immobilization in an external rotation brace (10 degrees to 15 degrees) with the arm at the side for 4 to 6 weeks is recommended to decrease tension in the posterior capsule. When passive range-of-motion exercises are instituted, they should be performed in the plane of the scapula to avoid stress posteriorly. Internal rotation and supine elevation should be avoided for similar reasons. Hawkins RJ, Neer CS II, Pianta RM, Mendoza FX: Locked posterior dislocation of the shoulder. J Bone Joint Surg Am 1987;69:9-18.

The most common shoulder injury in hockey players is to the acromioclavicular joint. Early rest and control of pain and inflammation is the preferred management. Surgery is reserved for patients with significant coracoclavicular disruption that has failed to respond to nonsurgical management. Cross-chest stretches and overhead exercises may increase symptoms. A cortisone injection within the glenohumeral joint will have little effect. Nuber GW, Bowen MK: Acromioclavicular joint injuries and distal clavicle fractures. J Am Acad Orthop Surg 1997;5:11-18.

Correct patellofemoral tracking has proven to be a crucial aspect in TKA because a large percent of problems after TKA are related to the patellofemoral articulation. External rotation of the femoral and tibial components has been shown to aid in tracking. Likewise, medialization of the patellar button aids in patellar tracking and prevention of lateral subluxations and dislocations. Attention to the distal femoral cut is critical in maintaining the joint line and preventing patella baja or alta. Tibial sizing, however, is not directly related to patellar tracking after TKA. Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, Lippincott Williams & Wilkins, 2003, pp 1245-1258.

Similar to the action of a force, a moment tends to angularly accelerate an object in a manner proportional to a quantity related to the mass of the object. The concept of a more massive object requiring a larger force to cause the same straight line acceleration is straightforward. The concept for changing angular velocity is similar but not identical. The proportional constant between the moment and the resulting angular acceleration is the mass moment of inertia, which depends not only on the mass of the object, but also its distribution. The unit of mass moment of inertia is obtained by multiplying the mass of the object by the square of the distance between an equivalent location of the center of rotation of the object and an equivalent location of the center of mass. Orthopaedic surgeons can change both the amount of mass carried by a limb and the way that the mass is distributed. For example, in applying a cast to the leg, the physician can affect the mass of the cast by the choice of casting material and by the size of the cast. As the mass moment of inertia of the limb increases (eg, by applying the cast farther down on the leg or using a heavier casting material), the patient will need to exert larger moments to angularly accelerate the leg during gait. Andriacchi T, Natarajan RN, Hurwitz DE: Musculoskeletal dynamics, locomotion, and clinical applications, in Mow VC, Hayes WC (eds): Basic Orthopaedic Biomechanics, ed 2. New York, NY, Lippincott-Raven, 1997, pp 43-47.

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.

Four years after surgery, more than 90% of patients are satisfied with the cosmetic appearance of the iliac donor site scar. Approximately 25% still have pain and/or functional difficulty, including 12.7% who still report difficulty with ambulation, 11.9% difficulty with recreational activities, 7.5% with sexual intercourse, and 11.2% require pain medication for iliac donor site symptoms. Silber JS, Anderson DG, Daffner SD, et al: Donor site morbidity after anterior iliac crest bone harvest for single-level anterior cervical discectomy and fusion. Spine 2003;28:134-139.

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.

The first extensor compartment of the wrist typically contains a single extensor pollicis brevis tendon and the abductor pollicis longus tendon that nearly always has multiple tendon slips. The extensor pollicis brevis tendon is frequently found to be separated from the slips of the abductor pollicis longus tendon by an intracompartmental septum. During surgery, this septum must be divided to complete the release of the compartment. Jackson WT, Viegas SF, Coon TM, Stimpson KD, Frogameni AD, Simpson JM: Anatomical variations in the first extensor compartment of the wrist: A clinical and anatomical study. J Bone Joint Surg Am 1986;68:923-926.

The patient will most likely exhibit ipsilateral weakness of the tibialis anterior. Gaenslen's test is designed to detect sacroiliac inflammation as a source of low back pain. Beevor's sign tests the innervation of the rectus abdominus and paraspinal musculature (L1 innervation). The extensor hallucis longus is predominantly innervated by L5. The peroneals are predominantly innervated by S1. Hoppenfeld S: Physical Examination of the Spine and Extremities. Appleton, WI, Century-Crofts, 1976.

Plasmacytoma is very sensitive to radiation therapy and given the complexity of the resection and complications of surgery in the given location, radiation therapy is preferred. However, the patient has clear loss of bony structural integrity, and resultant instability would persist even with tumor irradiation; therefore, posterior stabilization is warranted. Chemotherapy and bone marrow transplant are reserved for systemic disease with multiple myeloma. Corwin J, Lindberg RD: Solitary plasmacytoma of bone vs. extramedullary plasmacytoma and their relationship to multiple myeloma. Cancer 1979;43:1007-1013.

The atlanto-occipital joint is inherently unstable and would easily dislocate without the supporting ligaments. The apical ligament attaches to the basion and tip of the dens but does not provide adequate stability to the joint. Werne demonstrated that dividing the tectorial membrane and the alar ligaments resulted in gross joint instability. The anterior longitudinal ligament turns into the anterior atlanto-occipital membrane. This is called a membrane rather than a ligament because it is not strong enough to support these two structures. Werne S: Studies in spontaneous atlas dislocation. Acta Orthopaedica Scandinavica 1977;23(supplement).

The inability to single leg hop is considered the best indicator of a syndesmosis ankle sprain without diastasis. Tenderness along the syndesmosis, the deltoid, or over the anterior talofibular ligament or anterior distal tibia/fibula may present later, following the initial injury. The squeeze test and tenderness with dorsiflexion and external rotation may be positive but often are not present initially. The best determinant for prediction of return to play is the amount of tenderness along the syndesmosis, measured from the distal fibula up the syndesmosis. Nussbaum ED, Hosea TM, et al: Prospective evaluation of syndesmosis ankle sprains without diastasis. Am J Sports Med 2001;29:31-35. Miller CD, Shelton WR, Barrett GR, et al: Deltoid and syndesmosis ligament injury of the ankle without fracture. Am J Sports Med 1985;23:746-750.

The biopsy specimen is a low-power view of a soft-tissue sarcoma with a biphasic pattern of epithelial cells and fibrous spindle cells that are typical of a synovial sarcoma. A deep, painless soft-tissue mass greater than 5 cm in size is suspicious for a sarcoma. The imaging in this patient is indeterminate and the patient requires a biopsy for an accurate diagnosis. The biopsy reveals a tumor with a biphasic appearance consistent with a synovial sarcoma. These tumors are slow growing, occur primarily in the lower extremities, and are found in a younger demographic population compared to malignant fibrous histiocytoma and liposarcoma. They can occur in a biphasic pattern with clumps of epithelial cells and fibrous spindle cells or in a monophasic pattern. Synovial sarcomas stain positively for keratin. Keratin is positive in nearly all biphasic types and in many tumors of the monophasic fibrous type. Sixty percent of these tumors are found in the lower extremity. The area around the knee is the most common location, followed by the ankle and foot. Epithelioid and clear cell sarcomas are found associated with tendon sheaths of the hand and feet and are generally smaller in size. Epithelioid sarcoma may resemble granulomatous inflammation histologically; clear cell sarcoma is composed of nests of clear cells with occasional multinucleated giant cells. Pigmented villonodular synovitis is found within the synovium and is characterized by a villous histologic appearance with hemosiderin-laden macrophages. Malignant fibrous histiocytoma has a storiform histologic pattern with an abundance of pleomorphic cells. Enzinger FM, Weiss SW: Soft Tissue Tumors, ed 3. St Louis, MO, Mosby, 1995, p 757.

In the normal adult, the distance between the basion and the tip of the dens is 4 mm to 5 mm. Any distance greater than 5 mm is considered abnormal. This is one way to detect occipitocervical dissociation other than using the Power's ratio, which relies on an anterior dislocation. Wiesel SW, Rothman RH: Occipitoatlantal hypermobility. Spine 1979;4:187-191.

Extensor pollicis longus tendon rupture can occur after a fracture of the distal radius, even a minimally displaced one. Poor vascularity of the tendon within the third dorsal compartment is the suspected etiology, not the displaced fracture fragments. Tendon transfer will suitably restore active extension of the thumb interphalangeal joint. Christophe K: Rupture of the extensor pollicis longus tendon following Colles fracture. J Bone Joint Surg Am 1953;35:1003-1005.

The patient has an L5 radiculopathy secondary to an L4-5 disk herniation that is compressing the traversing L5 nerve root.

Generally, patients cannot tolerate more than 5 degrees of hindfoot posting. Donatelli RA, Hurlbert C, Conaway D, et al: Biomechanics foot orthotics: A retrospective study. J Orthop Sports Phys Ther 1988;10:205-212. Michaud TM: Foot Orthoses and Other Forms of Conservative Foot Care. Baltimore, MD, Williams & Wilkins, 1993, pp 61-65, 186.

The patient has lung cancer metastatic to the right proximal femur. The lesion is large, has destroyed a portion of the cortex, and involves the peritrochanteric region. All of these findings put the patient at high risk for pathologic fracture. The lesion is amenable to intramedullary fixation in the form of some type of reconstruction nail. Chemotherapy alone will not restore the bone stock. Given the extent of the lesion, radiation therapy, chemotherapy, or embolization will not prevent fracture. A proximal femoral replacement would be indicated in patients with bone destruction extending into the femoral head and neck. Bisphosphonates may diminish the risk of subsequent lesions but are not sufficient to treat this high-risk lesion. Radiation therapy should be given postoperatively to prevent further bone destruction.

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

The 5-year overall survival rate for deep, high-grade soft-tissue sarcomas is around 50%. The overall survival and disease-free survival rates chiefly depend on the tumor stage, but for all stages combined, most cancer treatment centers report a 5-year overall survival rate of around 70% and a disease-free survival rate of 65%. Fleming ID, et al: Manual for Staging of Cancer/American Joint Committee on Cancer, ed 5. Philadelphia, PA, Lippincott Raven, 1997, pp 149-156.

The radiograph shows medial migration of the cementless acetabular component, strongly suggesting acetabular discontinuity with a combined segmental and cavitary medial deficiency. The treatment of choice is a morcellized or structural graft, supported with a reconstructive cage bridging the pelvic discontinuity, and a cemented cup. Whiteside LA: Selection of acetabular component, in Steinberg ME, Garino JP (eds): Revision Total Hip Arthroplasty. Philadelphia, PA, Lippincott Williams and Wilkins, 1999, pp 209-220.

The radiographs reveal severe arthritic changes with no joint space, and the AP view shows a progressive malalignment secondary to the radial head resection. A prosthetic arthroplasty is indicated given the severe arthritis (Larsen grade III). Unconstrained arthroplasties have not performed as well as semiconstrained arthroplasties after previous radial head resections. However, both types of arthroplasties performed better in native elbows. Synovectomies should be reserved for less advanced disease states. Whaley A, Morrey BF, Adams R: Total elbow arthroplasty after previous resection of the radial head and synovectomy. J Bone Joint Surg Br 2005;87:47-53. Maenpaa HM, Kuusela PP, Kaarela KK, et al: Reoperation rate after elbow synovectomy in rheumatoid arthritis. J Shoulder Elbow Surg 2003;12:480-483.

Femoral acetabular impingement (FAI) is a pathologic entity leading to pain, reduced range of motion in flexion and internal rotation, and development of secondary arthritis of the hip. There are two types of FAI: cam impingement and pincher impingement. Cam impingement is seen when a nonspherical femoral head produces a cam effect when the prominent portion to the femoral head rotates into the joint. This mechanism produces shear forces that damage articular cartilage. Radiographs reveal early joint degeneration and flattening of the head neck junction (the so-called "pistol grip deformity") as seen in this image. The pincher type of impingement involves abnormal contact between the femoral head neck junction and the acetabulum, in the presence of a spherical femoral head. Beall DP, Sweet CF, Martin HD, et al: Imaging findings of femoraoacetabular impingement syndrome. Skeletal Radiol 2005;34:691-701.

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.

The degree of acetabular dysplasia and the age of the child are important considerations when choosing what type of osteotomy to perform. The ability to obtain concentric reduction is a prerequisite of all osteotomies that redirect the acetabulum. Procedures that cut all three pelvic bones allow more displacement and, therefore, correction of acetabular dysplasia. The closer the osteotomy is to the acetabulum, the greater the coverage of the femoral head. Compared with the other acetabular osteotomies, the Ganz periacetabular osteotomy provides the greatest potential for correcting acetabular deficiency because there are no bone or ligamentous restraints to limit correction, but it has the disadvantage of being a technically demanding procedure. The amount of coverage provided by the Salter osteotomy is limited. Millis MB, Poss R, Murphy SB: Osteotomies of the hip in the prevention and treatment of osteoarthritis, in Eilert RE (ed): Instructional Course Lectures XLI. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1992, pp 145-154.

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.

Discoid menisci are rare causes of lateral knee pain in children. Various etiologies have been proposed, including failure of central absorption of the developing meniscus and hereditary transmission. Patients with discoid menisci have pain, clicking, and locking with a loss of active extension on range-of-motion testing. Classification of discoid menisci according to the Watanabe classification include complete, incomplete, and Wrisberg ligament type. The Wrisberg variant contains an abnormal posterior meniscal attachment. MRI is the diagnostic tool of choice, revealing a thick, flat meniscus generally seen in three consecutive MRI images. Symptomatic knees are often associated with a meniscal tear or degeneration and are managed with arthroscopic partial excision to a more normal shape (saucerization). Vandermeer RD, Cunningham FK: Arthroscopic treatment of the discoid lateral meniscus: Results of long-term follow-up. Arthroscopy 1989;5:101-109.

The radiograph shows bilateral flattening of the femoral heads with mottling and "fragmentation" suggestive of Legg-Calve-Perthes disease. However, when these changes occur bilaterally and are symmetric, multiple epiphyseal dysplasia or spondyloepiphyseal dysplasia should be suspected. Skeletal survey will show irregularity of the secondary ossification centers. With these conditions, there is no true osteonecrosis and no evidence that orthotic or surgical "containment" will alter the outcome of progressive degenerative arthritis. Cardiac anomalies and coagulopathies are not associated with the epiphyseal dysplasias. Crossan JF, Wynne-Davies R, Fulford GE: Bilateral failure of the capital femoral epiphysis: Bilateral Perthes disease, multiple epiphyseal dysplasia, pseudoachondroplasia, and spondyloepiphyseal dysplasia congenita and tarda. J Pediatr Orthop 1983;3:297-301.

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

The literature supports similar clinical outcomes after surgical and nonsurgical methods. The chief difference lies in the complications between the groups. Surgical patients experience more wound problems but a significantly lower rerupture rate. Although suturing the tendon allows earlier mobility, the tendon healing time is unchanged. Nonsurgical methods are less expensive to provide. Maffulli N: Rupture of the Achilles tendon. J Bone Joint Surg Am 1999;81:1019-1036. Cetti R, Christensen SE, Ejsted R, Jensen NM, Jorgensen U: Operative versus nonoperative treatment of Achilles tendon rupture: A prospective randomized study and review of the literature. Am J Sports Med 1993;21:791-799.

Most closed simple dislocations are best managed with early range of motion. Posterior dislocation typically occurs through a posterolateral rotatory mechanism. When placed in pronation, the elbow has greater stability when the medial ligamentous structures are intact. In traumatic dislocations, MRI rarely provides additional information that will affect treatment. In elbows that remain unstable, primary repair is preferred over ligament reconstruction. Cast immobilization increases the risk of arthrofibrosis.

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.

To improve hip biomechanics and secure more suitable bone for acetabular fixation, the true acetabulum is often resurfaced in patients who have developmental dysplasia of the hip, thus lowering the hip center and lengthening the leg. Acute lengthening of more than 3 cm will place excessive tension on the sciatic nerve and require a femoral shortening to avoid sciatic nerve injury. The other maneuvers will not relieve sciatic nerve tension because of limb lengthening. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 430-431.

The radiograph shows a complete simple dislocation of the metacarpophalangeal joint. The clue to this injury is the perpendicular alignment of the proximal phalanx to the metacarpal on the lateral radiograph. This must be differentiated from the complete complex dislocation pattern that is irreducible because of the interposed volar plate. In lateral radiographs of these injuries, the long axes of the proximal phalanx and the metacarpal are parallel. Simple dislocations are amenable to closed reduction and casting. Some authors have recommended ulnar collateral ligament repair if instability is detected on examination after reduction. O'Brien ET: Part IV: Dislocations of hand and carpus, in Rockwood CA Jr, Wilkins KE, Beaty JH (eds): Fractures in Children, ed 4. Philadelphia, PA, Lippincott-Raven, 1996, vol 3, pp 429-431.

The superior gluteal artery is most at risk with a posterior iliac crest bone graft harvest. The artery leaves the pelvis through the sciatic notch and can be injured by retractors or other sharp instruments entering the sciatic notch area. The deep circumflex iliac, iliolumbar, and fourth lumbar arteries supply the iliacus and iliopsoas muscles and can be damaged during anterior bone graft harvest. The ascending branch of the lateral femoral circumflex artery is at risk during the anterior approach to the hip. Guyer RD, Delmarter RB, Fulp T, Small SD: Complications of cervical spine surgery, in Herkowitz HN, Garfin SR, Balderston RA, Eismont FJ, Bell GR, Wiesel SW (eds): Rothman-Simeone The Spine, ed 4. Philadelphia, PA, WB Saunders, 1999, p 547. Kurz LT, Garfin SR, Booth RE Jr: Iliac bone grafting: Techniques and complications of harvesting, in Garfin SR (ed): Complications of Spine Surgery. Baltimore, MD, Williams and Wilkins, 1989, pp 330-331.

All of the muscles are innervated by the peroneal nerve with the exception of the tibialis posterior which is innervated by the tibial nerve. Tibialis posterior function is best tested with resistance to plantar flexion and inversion.

A Keller proximal phalanx resection procedure usually results in reduced weight bearing under the first ray because of shortening of the toe and disruption of intrinsic flexor function. This can be an effective method of offloading a neuropathic ulcer under the great toe at the interphalangeal or metatarsophalangeal joint area. However, these features are generally undesirable in young active patients. The procedure has a high rate of recurrent deformity in patients with rheumatoid arthritis. It would exacerbate transfer metatarsalgia in a patient with a hypermobile first ray. Lin SS, Bono CM, Lee TH: Total contact casting and Keller arthroplasty for diabetic great toe ulceration under the interphalangeal joint. Foot Ankle Int 2000;21:588-593.

The fracture pattern shown in the radiograph involves both a talar neck fracture and a talar body fracture. The body fracture propagates into the subtalar joint, with significant risk for the development of arthritis in that surface even with an anatomic reduction. In addition, Canale and Kelly reported a 25% incidence of malunion of talar neck fractures, with varus angulation occurring most frequently. Of these patients, 50% required a secondary surgical procedure because of the development of degenerative joint disease of the subtalar joint. Canale ST, Kelly FB Jr: Fractures of the neck of the talus: Long-term evaluation of seventy-one cases. J Bone Joint Surg Am 1978;60:143-156.

Insufficient caloric intake caused by either a poor diet or an eating disorder is the most common cause for the loss of menses in a female athlete. In the face of adequate caloric intake, stress is unlikely to cause amenorrhea. Oral contraceptives control menses but do not eliminate it. Diabetes mellitus does not cause the new onset of amenorrhea. Pregnancy can be a cause in a sexually active athlete. Chromosomal abnormalities can result in delayed or absent menarche but not the onset of amenorrhea in a postmenarchal female. Constantini NW: Clinical consequences of amenorrhea. Sports Med 1994;17:213-223.

The biopsy specimens show a chondromyxoid fibroma with varying amounts of cartilage, benign fibrous tissue, giant cells, and loose myxoid areas. Chondromyxoid fibroma is a benign active bone lesion that is best treated with aggressive curettage and bone grafting. Although recurrences are common, more aggressive treatment is not warranted initially. Wilson AJ, Kyriakos M, Ackerman LV: Chondromyxoid fibroma: Radiographic appearance in 38 cases and in a review of the literature. Radiology 1991;179:513-518.

Rupture of the pectoralis major tendon most commonly occurs during bench pressing. Wolfe and associates have shown that the most inferiorly located fibers of the sternal head lengthen disproportionately during the final 30 degrees of humeral extension during the bench press. This creates a mechanical disadvantage in the final portion of the eccentric phase of the lift; with forceful flexion of the shoulder these maximally stretched fibers may rupture. In most patients, particularly in young athletes, the treatment of choice is anatomic repair of the ruptured tendon to its insertion in the proximal humerus either with suture anchors or transosseous sutures. Following surgery, most patients experience a near normal return of strength and significant improvement in the cosmetic appearance of the deformity. While more technically challenging, repair of chronic rupture is possible and is indicated in some patients. Wolfe SW, Wickiewicz TL, Cavanaugh JT: Ruptures of the pectoralis major muscle: An anatomic and clinical analysis. Am J Sports Med 1992;20:587-593.

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

The examination findings do not correlate with an acute injury (full range of cervical motion and the absence of pain). Radiographically, the fracture appears old based on the smooth contour of the fracture fragments and the absence of soft-tissue swelling. Flexion-extension radiographs can be obtained to determine potential instability; if present, stabilization and fusion should be considered. Schatzker J, Rorabeck CH, Waddell JP: Non-union of the odontoid process: An experimental investigation. Clin Orthop 1975;108:127-137.

An extended trochanteric osteotomy has been shown to be very efficient in removing a well-fixed distal implant and cement with minimal complications. Direct lateral, posterior, and transtrochanteric osteotomy exposures do not provide exposure of the midfemur.

The arrow is pointing to the posterior columns of the spinal cord that transmit position sense, vibratory sense, and proprioception. There are no motor tracts in the posterior columns. Bohlman H, Ducker T, Levine A: Spine trauma in adults, in Herkowitz HH (ed): The Spine, ed 4. Philadelphia, PA, WB Saunders, 1992, p 911.

Hypophosphatemic rickets is an inherited disorder that is transmitted by a unique sex-linked dominant gene. Therefore, if a male patient has a female offspring, his affected X chromosome will be transmitted and all of his female children will have hypophosphatemic rickets. All male offspring of a male patient will be unaffected. All offspring of a female patient have a 50% chance of having the disorder. Understanding the inheritance of hypophosphatemic rickets facilitates early diagnosis and early treatment. Medical treatment with phosphorus and some types of vitamin D (most authors recommend calcitriol) improves, but does not fully correct, the mineralization defect in hypophosphatemic rickets. However, if medical treatment is begun before the child begins walking, the growth plate is then adequately protected and a bowleg deformity will most likely be prevented. Evans GA, Arulanantham K, Gage JR: Primary hypophosphatemic rickets: Effect of oral phosphate and vitamin D on growth and surgical treatment. J Bone Joint Surg Am 1980;62:1130-1138.

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.

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

Transient osteoporosis of the hip is an uncommon problem, usually affecting women in the last trimester of pregnancy and middle-aged men. Symptoms include pain in the involved hip with temporary osteopenia; however, there is no joint space involvement. In this patient, the imaging findings are consistent with transient osteoporosis. Short TR/TE (repetition time/echo time) images reveal diffusely decreased signal intensity in the femoral head and intracapsular region of the femoral neck. Increased signal intensity is seen with increased T2-weighting. Within a few months, the pain, as well as the imaging findings, will completely resolve without intervention. Distinguishing the diffuse features of transient osteoporosis of the hip from the segmental findings of osteonecrosis is essential. Unlike transient osteoporosis of the hip, osteonecrosis will have a double-density signal on MRI and may progress radiographically. Surgical intervention and oral corticosteriods are not indicated for treatment. Protected weight bearing until the pain resolves may decrease symptoms while the transient osteoporosis resolves. Potter H, Moran M, Scheider R, et al: Magnetic resonance imaging in diagnosis of transient osteoporosis of the hip. Clin Orthop 1992;280:223-229. Bijl M, van Leeuwen MA, van Rijswijk MH: Transient osteoporosis of the hip: Presentation of typical cases for review of the literature. Clin Exp Rheumatol 1999;17:601-604.

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.

If a Cobb elevator is directed caudally while stripping the periosteum over the iliac wing, it will encounter the sciatic notch. Although this puts the sciatic nerve at risk, the first structure encountered is the superior gluteal artery. Because it is tethered at the superior edge of the notch, it is very vulnerable to injury and can then retract inside the pelvis, making it difficult to obtain hemostasis. The inferior gluteal artery exits the sciatic notch below the piriformis and is more protected. The cluneal nerves are at risk only if the incision extends too anteriorly, and the sacroiliac joint can be entered while harvesting the graft. Banwart JC, Asher MA, Hassanein RS: Iliac crest bone graft harvest donor site morbidity: A statistical evaluation. Spine 1995;20:1055-1060.

A high index of suspicion is required to identify a possible navicular stress fracture, especially in runners. High pain tolerance in the competitive athlete and often minimal swelling contribute to frequent delays in diagnosis. Localized tenderness over the dorsal navicular (so-called "N spot") in a running athlete should alert the treating physician. In this patient, the radiographs are negative and the MRI scan shows marrow edema within the navicular. This could represent a stress reaction, stress fracture, or osteonecrosis. Appropriate management should include non-weight-bearing immobilization and obtaining a CT scan to determine if a fracture is present. Early surgical treatment may be considered but only if a fracture is identified. Lee A, Anderson R: Stress fractures of the tarsal navicular. Foot Ankle Clin 2004;9:85-104.

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.

Repetitive subfailure strains have been shown to affect the mechanical behavior of the inferior glenohumeral ligament, producing dramatic declines in the peak load response and length increases that are largely unrecoverable. In another study, anteroinferior subluxation was found to result in nonrecoverable strain in the anteroinferior capsule, varying from 3% to 7% through a range of joint subluxation. Pollock RG, Wang VM, Bucchieri JS, et al: Effects of repetitive subfailure strains on the mechanical behavior of the inferior glenohumeral ligament. J Shoulder Elbow Surg 2000;9:427-435.

Atraumatic subluxation or dislocation of the sternoclavicular joint typically occurs in individuals with generalized ligamentous laxity. It is generally not painful, has no long-term sequelae, and needs no treatment. In fact, it is more likely to be painful following surgery than if managed nonsurgically. Rockwood CA Jr, Odor JM: Spontaneous atraumatic anterior subluxation of the sternoclavicular joint. J Bone Joint Surg Am 1989;71:1280-1288.

In an infant younger than age 6 months with a complete dislocation of the hip that is not initially reducible, the Pavlik harness may be used for a trial of guided reduction. When the harness is used in these patients, the infant should be followed at weekly intervals to see if reduction has been achieved. If the hip does not reduce after 3 to 4 weeks of harness wear, the harness should be discontinued, and closed or open reduction should be considered to avoid secondary deformation of the posterolateral acetabulum, also known as Pavlik harness pathology. Changing to other abduction braces is not indicated. Jones GT, Schoenecker PL, Dias LS: Developmental hip dysplasia potentiated by inappropriate use of the Pavlik harness. J Pediatr Orthop 1992;12:722-726. Atar D, Lehman WB, Grant AD: Pavlik harness pathology. Isr J Med Sci 1991;27:325-330.

The patient has a distal biceps rupture. While the distal biceps contributes to elbow flexion, its main function is forearm supination. Baker BE, Bierwagen D: Rupture of the distal tendon of the biceps brachii: Operative versus non-operative treatment. J Bone Joint Surg Am 1985;67:414-417. D'Arco P, Sitler M, Kelly J, et al: Clinical, functional, and radiographic assessments of the conventional and modified Boyd-Anderson surgical procedures for repair of distal biceps tendon ruptures. Am J Sports Med 1998;26:254-261.

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.

Flexion contractures and angular deformities of a limb cause inaccurate limb-length measurement results with most clinical methods. A CT scanogram is more accurate than standard scanograms for determining limb length in patients with knee flexion contractures of 30 degrees or more. The cost and time necessary to complete the examinations are comparable, but the CT scanogram delivers only 20% of the radiation needed for standard scanograms. Aaron A, Weinstein D, Thickman D, Eilert R: Comparison of orthoroentgenography and computed tomography in the measurement of limb-length discrepancy. J Bone Joint Surg Am 1992;74:897-902.

The history and physical examination are consistent with a monoarticular joint condition but not typical of joint sepsis. The arthroscopic appearance of brownish proliferative synovium is typical of PVNS. PVNS is a monoarticular synovial disease of unknown etiology and is treated with total synovectomy. The proliferative synovitis is not consistent with chondromalacia. Synovial cell sarcoma is an extracapsular disease. Rheumatoid arthritis typically is polyarticular, and the synovial appearance is not associated with hemosiderin deposition. Flandry FC, Hughston JC, Jacobson KE, Barrack RL, McCann SB, Kurtz DM: Surgical treatment of diffuse pigmented villonodular synovitis of the knee. Clin Orthop 1994;300:183-192.

Osteonecrosis of the femoral head is the most devastating complication of SCFE. There is a 47% incidence of ischemic necrosis associated with an unstable SCFE. By definition, the patient with an unstable SCFE is unable to bear weight even with crutches. Osteonecrosis is most likely associated with the initial femoral head displacement rather than the result of either tamponade from hemarthrosis or from gentle repositioning prior to stabilization. Age, sex, and obesity are not risk factors for osteonecrosis. Loder RT, Richards BS, Shapiro PS, et al: Acute slipped capital femoral epiphysis: The importance of physeal stability. J Bone Joint Surg Am 1993;75:1134-1140.

The flexor digitorium longus is the commonly accepted tendon transfer for posterior tibial tendon insufficiency. The flexor hallucis longus has to be carefully rerouted to avoid crossing the neurovascular bundle and has not been shown clinically to provide superior results to flexor digitorum longus transfer. Use of the peroneus longus results in loss of plantar flexion strength of the first metatarsal, contributing to the flatfoot deformity. The anterior tibial tendon is in the anterior compartment and fires out of phase with the posterior tibial tendon. Sitler DF, Bell SJ: Soft tissue procedures. Foot Ankle Clin 2003;8:503-520.

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

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

Garfin and associates have shown that halo pins inserted with 8 in-lb of insertion torque results in significantly less loosening with cyclical loading than pins inserted with 6 in-lb of torque. Moreover, Botte and associates reported that 8 in-lb of torque is clinically safe and effective in lowering the incidence of pin loosening and infection. Botte MJ, Byrne TP, Garfin SR: Application of the halo device for immobilization of the cervical spine utilizing an increased torque pressure. J Bone Joint Surg Am 1987;69:750-752. Garfin SR, Lee TO, Roux RD, et al: Structural behavior of the halo orthosis pin-bone interface: Biomechanical evaluation of standard and newly designed stainless steel halo fixation pins. Spine 1986;11:977-981.

Complications of medial sesamoidectomy include stiffness, claw toe, and hallux valgus. Each sesamoid sits within its respective head of the flexor hallucis brevis tendon. Excision of one sesamoid can result in slack in its flexor hallucis brevis tendon; therefore, it is imperative to preserve or repair the flexor hallucis brevis tendon when removing the medial sesamoid. Dedmond BT, Cory JW, McBryde A Jr: The hallucal sesamoid complex. J Am Acad Orthop Surg 2006;14:745-753.

Although not as common as arterial injury, venous thrombosis secondary to trauma of the subclavian or axillary vein can be problematic; therefore, venous duplex ultrasound scanning is the diagnostic study of choice. Arteriography may not show venous thrombosis in the venous run-off phase. The clinical history does not fit the usual presentation of a compartment syndrome or complex regional pain syndrome.

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

Premature consolidation is a complication that is unique to gradual bone lengthening after corticotomy. Causes include excessive latency period, inadequate distraction rate, exuberant bone formation, patient compliance problems, and mechanical failure of the distraction apparatus. The femur and fibula are most commonly involved. This patient did not have an incomplete corticotomy, as initial distraction occurred before the distraction device was noted to seize up. The radiographs show bowing of the Ilizarov wires and mature regenerate bone, both suggestive of premature consolidation. No wire breakage or joint subluxation is seen on the radiographs. Treatment for premature consolidation includes continuing distraction until the consolidation bridge ruptures, or additional surgery may include closed rotational osteoclasis or repeat corticotomy. Paley D: Problems, obstacles and complications of limb lengthening, in Maiocchi AB, Aronson J (eds): Operative Principles of Ilizarov. Baltimore, MD, Williams & Wilkins, 1991, p 360.

Excision of the affected mucoid degenerative area is considered appropriate management in the Blazina classification system. A finding of phase III indicates persistent pain with or without activities, as well as deterioration of performance. With the appearance of the mucoid degeneration and the vigorous activity level of the intercollegiate basketball player, it is unlikely that nonsurgical management will provide adequate relief. When excising the affected degenerative area, care must be taken to retain normal tendon fibers. The defect in the patellar tendon is closed with absorbable sutures, as is the paratenon. Postoperative rehabilitation involves initial mobilization extension, with progressive range-of-motion and mobilization exercises as tolerated and weight bearing as tolerated. Open chain and isokinetic exercises are delayed until full range of motion and mobility is obtained, generally within 4 weeks. A return to activities is achieved by 80% to 90% of athletes, although there may be occasional activity-related aching for 4 to 6 months after surgery. Blazina ME, et al: Jumper's knee. Orthop Clin North Am 1973;4:665. Kelly DW, Carter VS, Jobe FW, Kerlan RK: Patellar and quadriceps tendon ruptures: Jumper's knee. Am J Sports Med 1984;12:375-380. Krums PE, Ryder B: Operative treatment of patella tendon disorders. Operative Techniques Sports Med 1994;2:303.