General Orthopedics 2026 Practice Questions: Set 3 (Solved)

<span class="exp-title">Detailed Explanation</span><div markdown="1">Slight external rotation of the tibial component will cause a net medialization of the tibial tubercle when the knee is articulated. This will help centralize the extensor mechanism over the trochlear groove and minimize the tendency for lateral subluxation. Internal rotation of the femoral component increases the risk of patellar instability. Anterior translation of the tibial component moves the patellar tendon insertion posteriorly, and may increase force on the patella but should not substantially alter patellar tracking. Clinical studies have shown no patellofemoral benefits to the use of fixed- or mobile-bearing designs. Thicker patellar components will not improve tracking, and may compound the problem. Pellicci PM, Tria AJ Jr, Garvin KL (eds): Orthopaedic Knowledge Update: Hip and Knee Reconstruction 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, pp 207, 323-337 Pagnano MW, Trousdale RT, Stuart MJ, et al: Rotating platform knees did not improve patellar tracking: A prospective, randomized study of 240 primary total knee arthroplasties. Clin Orthop 2004;428:221-227.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Traditional classification of slipped capital femoral epiphyses is based on the following temporal criteria: acute (symptoms that persist for less than 3 weeks); chronic (symptoms that persist for more than 3 weeks); or acute on chronic (acute exacerbation of long-standing symptoms). A newer classification differentiates between a stable slip where weight bearing is possible, and an unstable slip if it is not. Reduction of an unstable slip often occurs unintentionally with induction of anesthesia and positioning of the patient for surgery. The rate of satisfactory results is lower primarily because of a much higher incidence of osteonecrosis following internal fixation of an unstable slip. Loder RT, Richards BS, Shapiro PS, Reznick LR, Aronson DD: Acute slipped capital femoral epiphysis: The importance of physeal stability. J Bone Joint Surg Am 1993;75:1134-1140.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The most common complication following acetabular or pelvic ring injury is deep venous thrombosis (DVT). Without prophylaxis, rates of DVT are as high as 70% to 80%. With prophylaxis, the rates are around 10%. Infection rates in surgical repair of acetabular fractures are relatively low but a history of diabetes mellitus and a significant Morel-Lavalle lesion certainly increase the risk. However, even with these two complicating factors, the rates of infection are still lower than 10%. Sciatic nerve palsy rates from the injury alone approach 20% and iatrogenic injury is usually less than 2%. Degenerative changes to the hip following this injury approach 20% to 25%, even with an anatomic reduction. Geerts WH, Code KI, Jay RM, et al: A prospective study of venous thromboembolism after major trauma. N Engl J Med 1994;331:1601-1606.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient's right upper extremity is held in the "head waiter's" posture with the shoulder internally rotated, the elbow extended, and the wrist in flexion. The Erb type of obstetrical brachial plexus palsy involves the C5 and C6 nerve root, and occasionally, as in this child, the C7 nerve root. Obstetrical palsy is a traction injury, and is associated with a high birth weight, shoulder dystocia, cephalopelvic disproportion, or the use of forceps. Erb palsy is four times more common than injury to the entire plexus or injury to the C8 and T1 nerve roots. It results from the shoulder being depressed while the head and neck are laterally rotated, extended, and tilted in the opposite direction. Most patients recover wrist extension and elbow flexion. Patients with residual weakness of shoulder external rotation and abduction will benefit from release of the pectoralis major, latissimus dorsi, and teres major, with transfer of the latissimus dorsi and the teres major to the posterosuperior aspect of the rotator cuff. Recent studies using arthrograms and CT scans have shown a higher incidence of posterior glenoid deficiency and posterior subluxation than that observed with plain radiographs. The posterior subluxation or dislocation can be effectively reduced by tendon release and transfer procedures. Hoffer MM, Phipps GJ: Closed reduction and tendon transfer for treatment of dislocation of the glenohumeral joint secondary to brachial plexus birth palsy. J Bone Joint Surg Am 1998;80:997-1001. Pearl ML, Edgerton BW: Glenoid deformity secondary to brachial plexus birth palsy. J Bone Joint Surg Am 1998;80:659-667.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The treatment of choice for proximal pole scaphoid fractures is open reduction and internal fixation with a differential pitch screw via a dorsal approach. Healing rates of 100% have been reported for these acute fractures. Casting results in slow healing, with recommendations including 16 weeks or more in a cast. Vascularized bone grafts are not indicated for acute fractures. Rettig ME, Raskin KB: Retrograde compression screw fixation of acute proximal pole scaphoid fractures. J Hand Surg 1999;24:1206-1210.

<span class="exp-title">Detailed Explanation</span><div markdown="1">When a study yields a negative result between treatment groups, the next step is to perform a power analysis. The power, by definition, is the probability of rejecting the null hypothesis: in this example the null hypothesis would be that children treated with bisphosphonates would have fewer fractures than the untreated control population. The power analysis helps answer the question as to whether the null hypothesis should be rejected and the finding is real, or whether the sample size was too small or the effect of treatment too subtle to demonstrate a difference between the treatment and control groups. Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System, ed 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2000, p 7.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Most subtalar dislocations can be easily reduced by closed methods. If no fractures or defects are seen on the postreduction radiographs, then the success rate with cast immobilization is good. Medial dislocations have a better prognosis than lateral dislocations. Late instability is rare; therefore, the duration of immobilization should not be excessive. Most subtalar dislocations result in some stiffening of the hindfoot, and painful degenerative arthrosis is the most common serious complication.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The initial fracture was an unstable reverse oblique intertrochanteric fracture with subtrochanteric extension. Initial fixation with a high-angled screw and side plate construct may not provide stability as well as a 95 degree fixed-angle device or a intramedullary hip screw device. The follow-up radiographs show loss of fixation and further propagation of the fracture distally. Reconstruction would best be accomplished with hardware removal and conversion to a long intramedullary nail with femoral head fixation or a 95 degree angled plate and screw device. Conversion to a longer plate does not improve the biomechanical situation at the primary fracture site. In situ bone grafting would not provide any additional stability and would not correct the deformity. The proximal femoral fracture is not amenable to retrograde nailing. Cerclage wiring will not sufficiently enhance stability and is not indicated. Bridle SH, Patel AD, Bircher M, Calvert PT: Fixation of intertrochanteric fractures of the femur: A randomized prospective comparison of a gamma nail and dynamic hip screw. J Bone Joint Surg Br 1991;73:330-334. DeLee JC: Fractures and dislocations of the hip, in Rockwood CA Jr, Green DP, Bucholz RW, Heckman JD (eds): Rockwood and Green's Fractures in Adults, ed 4. Philadelphia, PA, Lippincott-Raven, 1996, pp 1659-1825. 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.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Whereas chondrosarcoma is the most frequently occurring malignant bone tumor of the foot and synovial sarcoma is the most common soft-tissue foot malignancy, the most common malignant tumor overall is melanoma. It constitutes approximately 25% of lesions found on the lower extremity. Furthermore, 31% of all melanomas arise in the foot. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 11-26.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The most common complication of dorsal plating is extensor tenosynovitis, which often causes pain and is a frequent reason for hardware removal. Other less frequent complications include loss of reduction and extensor tendon ruptures, with flexor tendon ruptures occuring to an even lesser degree. Rozental TD, Beredjiklian PK, Bozentka DJ: Functional outcome and complications following two types of dorsal plating for unstable fractures of the distal part of the radius. J Bone Joint Surg Am 2003;85:1956-1960.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The right syndesmosis appears disrupted on the CT scan when compared to the normal left side. CT can be helpful in determining injury to the syndesmosis, especially with occult clinical findings. Ebraheim NA, Lu J, Yang H, et al: The fibular incisure of the tibia on CT scan: A cadaver study. Foot Ankle Int 1998;19:318-321. Ebraheim NA, Lu J, Yang H, et al: Radiographic and CT evaluation of tibiofibular syndesmotic diastasis: A cadaver study. Foot Ankle Int 1997;18:693-698.

<span class="exp-title">Detailed Explanation</span><div markdown="1">High-energy tibial pilon fractures involve disruption of the soft-tissue envelope with significant lower extremity edema. Definitive reconstruction of the comminuted distal tibia should be delayed for at least 7 days to allow edema to dissipate, lowering the risk of skin necrosis. An external fixator is the best method to keep the ankle at anatomic length while preventing skin necrosis. Ligamentotaxis will hold the fragments reduced to allow the edema to dissipate. CT may be obtained in traction to localize the individual fragments and plan surgical incisions and subsequent fixation. Short leg casting will not provide adequate ligamentotaxis to hold the fragments reduced and prevent skin compromise. Primary fusion of the ankle in an unstable tibial pilon fracture is prone to a poor result from nonunion or malunion. Tornetta P III, Weiner L, Bergman M, et al: Pilon fractures: Treatment with combined internal and external fixation. J Orthop Trauma 1993;7:489-496.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The resultant spasticity and weakness (paresis) following a cerebrovascular accident leads to muscle imbalance that commonly results in contracture of the shoulder in adduction, internal rotation, and varying degrees of forward flexion. In addition, the elbow is usually flexed and the forearm pronated. Braun RM, Botte MJ: Treatment of shoulder deformity in acquired spasticity. Clin Orthop 1999;368:54-65.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Posterior atlantoaxial arthrodesis predictably relieves pain associated with arthrosis of the atlantoaxial joints. Typically, these patients have pain at the base of the occiput and in the most cephalad portion of the posterior aspect of the neck. Associated headache is common and often severe. Pain is aggravated by rotation but usually not by flexion and extension. Diagnostic blocks of the C1-C2 joint and the greater occipital nerve may be helpful to confirm the diagnosis preoperatively. Ghanayem AJ, Leventhal M, Bohlman HH: Osteoarthrosis of the atlanto-axial joints: Long-term follow-up after treatment with arthrodesis. J Bone Joint Surg Am 1996;78:1300-1307.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Surgery is not indicated in a patient who has a mild deformity and no pain. Shoe wear modifications should be recommended.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has an axillary nerve injury, which is relatively uncommon after surgery for instability. This type of injury generally is the result of a stretch injury rather than transection or a hematoma. Therefore, observation is indicated in the early postoperative period. After approximately 6 weeks, electromyography can be used to confirm and document the point of injury. Interscalene blocks can cause prolonged nerve injury but usually are not limited to the axillary nerve.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The CT scan reveals a left-sided psoas abscess. Irritation of the saphenous division of the femoral nerve can cause paresthesias along the medial aspect of the knee. Pain is usually improved with hip flexion. Cellier C, Gendre JP, Cosnes J, et al: Psoas abscess complication Crohn's disease. Gastroenterol Clin Biol 1992;16:235-238.

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

<span class="exp-title">Detailed Explanation</span><div markdown="1">The radiographs show a posterior knee dislocation. Knee dislocations almost always involve rupture of both the anterior and posterior cruciate ligaments. Collateral ligament injuries also are common. Arterial, nerve, and tendon injuries each occur in less than half of knee dislocations. Schenck RC Jr, Hunter RE, Ostrum RF, et al: Knee dislocations. Instr Course Lect 1999;48:515-522.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has osteochondritis dissecans. While location, size, and knee stability are all relevant to the overall prognosis, studies have shown that younger patients with open growth plates have a better prognosis of healing when compared with patients who have closed growth plates. The degree of pain is also relevant to treatment, but it is subjective rather than objective and is not as reliable of a prognostic indicator as age. Stanitski CL: Osteochondritis dissecans of the knee, in Stanitski CL, DeLee JC, Drez D Jr (eds): Pediatric and Adolescent Sports Medicine. Philadelphia, PA, WB Saunders, 1994, vol 3, pp 387-405. Cahill B: Treatment of juvenile osteochondritis dissecans and osteochondritis dissecans of the knee. Clin Sports Med 1985;4:367-384.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The MRI scans show Modic changes in the L4-L5 vertebral bodies due to spondylosis. There is no increased fluid signal or enhancement in the L4-L5 disk to suggest infection or any other pathologic process. Therefore, the patient's pain should be treated with a course of physical therapy and rehabilitation. There is no infection; therefore, IV antibiotics and debridement are not indicated. Similarly, a pseudomeningocele is not present. A revision diskectomy is useful for recurrent radiculopathy but would not be helpful for degenerative low back pain. Spivak JM, Connolly PJ (eds): Orthopaedic Knowledge Update: Spine 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, pp 319-329.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The vascular supply to the medial and lateral menisci originates predominantly from the medial and lateral genicular arteries. The popliteal artery splits into the superior genicular, which splits into medial and lateral branches supplying the patellar cartilage and the posterior cruciate ligament. The middle genicular artery also supplies the anterior curciate ligament, posterior cruciate ligament, and collateral ligaments. The inferior genicular splits into medial and lateral branches and supplies the menisci and other knee ligaments. Despite propagation of incorrect terminology, there is no superior or lateral genicular artery.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The rotator cuff interval is located between the supraspinatus and subscapularis and the biceps tendon is deep to the interval. It is a triangular area where the base is the coracoid process and the apex is the transverse humeral ligament at the biceps sulcus. Closure or tightening of this area is often helpful in patients with shoulder instability. Conversely, this area is often contracted in patients with adhesive capsulitis and may need to be released. Selecky MT, Tibone JE, Yang BY, et al: Glenohumeral joint translation after arthroscopic thermal capsuloplasty of the rotator interval. J Shoulder Elbow Surg 2003;12:139-143.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The radiograph shows a benign-appearing cortically based lesion eroding the underlying cortex, producing a saucer-shaped defect typical of a periosteal chondroma. The histology shows benign-appearing neoplastic cartilage. Although enchondroma would have the same histologic appearance, radiographs generally show a lesion with a central medullary epicenter. The benign-appearing histology does not support chondrosarcoma. Chondromyxoid fibroma will generally show histologic elements of its fibrous and myxoid components. Chondroblastoma typically demonstrates histologic findings of polyhedral cells separated by a chondroid matrix with pericellular, lattice-like "chicken wire" calcification. Schajowicz F: Tumors and Tumorlike Lesions of Bone: Pathology, Radiology, and Treatment, ed 2. Berlin, Springer-Verlag, 1994, pp 147-151.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Progressive scoliosis develops in most patients with Duchenne muscular dystrophy. The onset of spinal deformity typically follows the cessation of walking, and curves can be expected to progress about 10 degrees per year. Posterior spinal fusion with instrumentation should be performed as soon as a curve of 25 degrees or greater is documented and before deterioration of pulmonary function (a FVC of less than 30%) precludes surgery. Patients with kyphotic posture tend to progress more rapidly than those with lordotic posture. Brace treatment is contraindicated because it is not definitive and it may mask curve progression while pulmonary function is concomitantly worsening. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1999, pp 635-651.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Infantile tibia vara is a developmental condition characterized by a varus angulation of the proximal end of the tibia that is caused by a growth disturbance of the proximal medial physis. In a study of 42 affected extremities in 24 children younger than age 3 years, it was found that daytime ambulatory brace treatment favorably altered the natural history of tibia vara. Another study of 27 patients with stage II Langenskiöld disease found a success rate of 70% (improved alignment without the need for osteotomy) using brace treatment. These authors also noted that children with unilateral disease were more likely to obtain correction of the deformity compared with those with bilateral disease. In this patient, observation is not warranted because untreated tibia vara has a significant risk for progressive worsening. Osteotomy is best reserved for those patients who, despite bracing, do not show satisfactory clinical and radiographic improvement by age 4 years. Elevation of the medial tibial plateau is a treatment option for older patients who have more advanced disease. An MRI scan would not provide any useful clinical information at this time. Zionts LE, Shean CJ: Brace treatment of early infantile tibia vara. J Pediatr Orthop 1998;18:102-109. Richards BS, Katz DE, Sims JB: Effectiveness of brace treatment in early infantile Blount's disease. J Pediatr Orthop 1998;18:374-380.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a fracture-dislocation of the radiocarpal joint. Attached to the large radial styloid fragment are the extrinsic wrist ligaments to the carpus. This injury should be treated with open reduction and internal fixation of the styloid fracture. Radiolunate fusion or extrinsic ligament repair is suggested when the extrinsic ligaments are ruptured, resulting in ulnar translocation of the carpus. Dumontier C, Meyer ZU, Reckendorf G, et al: Radiocarpal dislocations: Classification and proposal for treatment: A review of twenty-seven cases. J Bone Joint Surg Am 2001;83:212.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient's history, including the timing and type of symptoms, is typical for postoperative diskitis. The elevated ESR, 5 weeks after surgery, is also consistent with infection; a normal WBC count is not unusual. Management should consist of MRI with gadolinium; if positive, this should be followed by percutaneous biopsy to confirm the organism. Open biopsy may be considered if the percutaneous biopsy is unsuccessful. Anterior debridement and interbody fusion is reserved for the occasional patient that fails to respond to intravenous antibiotics, bed rest, and immobilization. Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 257-271.

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

<span class="exp-title">Detailed Explanation</span><div markdown="1">Elbow dislocations in children are rare injuries and usually result from a fall on an outstretched arm. The incidence of these injuries increases as patients age and concurrently the incidence of supracondylar humerus fractures decreases. In adolescent patients, simple elbow dislocations are treated with splint immobilization and the initiation of physical therapy once comfortable. The practitioner must be aware of structures that may get caught in the joint on reduction. These include the median nerve as well as the medial epicondyle. In this patient, the radiographs reveal a medial epicondyle fracture. Postreduction radiographs show the joint to be incongruous secondary to intra-articular displacement. At this point, the most appropriate treatment is to perform an open reduction and repair of the medial epicondyle fragment. Rasool MN: Dislocations of the elbow in children. J Bone Joint Surg Br 2004;86:1050-1058.

<span class="exp-title">Detailed Explanation</span><div markdown="1">While the patellar tendon ligament is considered by many to be the tissue of choice for ACL reconstruction, more recent studies have shown that the quadruple semitendinosus and gracilis tendon graft has the greatest stiffness and offers the highest maximum load to failure. Hamner DL, Brown CH Jr, Steiner ME, Hecker AT, Hayes WC: Hamstring tendon grafts for reconstruction of the anterior cruciate ligament: Biomechanical evaluation of the use of multiple strands and tensioning techniques. J Bone Joint Surg Am 1999;81:549-557. Cooper DE, Deng XH, Burstein AL, Warren RF: The strength of the central third patellar tendon graft: A biomechanical study. Am J Sports Med 1993;21:8l8-823. Brown CH Jr, Steiner ME, Carson EW: The use of hamstring tendons for anterior cruciate ligament reconstruction: Technique and results. Clin Sports Med 1993;12:723-756.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has pain involving the cervical and lumbar spine as well as pain and swelling in both the knees and ankles. As such, this can be classified as polyarticular arthritis. The presence of multiple joint symptoms in the lower extremities, the absence of a history of trauma, and the multiple joints involved direct attention away from the spine as the etiology of this patient's pain. Radiographs of the involved joints are not likely to yield much useful information to assist with a diagnosis. Likewise, an MRI scan of the lumbar spine is not likely to provide much information regarding the etiology of the patient's condition. When a rheumatologic illness is suspected, the selective use of confirmatory laboratory testing can aid in arriving at a correct diagnosis. A presumed case of gout or chondrocalcinosis can be confirmed by the presence of the appropriate crystals in a joint-fluid aspiration. Because of the patient's recent trip to Costa Rica and the subsequent gastroenteritis, a CBC count, ESR, and CRP should be ordered to rule out infectious and inflammatory versus noninflammatory conditions. Rheumatoid factor (RF) in general should only be ordered for patients with polyarticular joint inflammation for more than 6 weeks. The presence of rheumatoid factor does not indicate rheumatoid arthritis. Antinuclear antibodies (ANA) should be ordered when a connective tissue disease such as systemic lupus erythematosus (SLE) is suspected on the basis of specific history and physical examination findings, such as inflammatory arthritis. Human leukocyte antigen-B27 (HLA-B27) should be ordered only when the patient's history is compatible with ankylosing spondylitis or Reiter's syndrome and this patient had a history of Reiter's syndrome. Gardner GC, Kadel NJ: Ordering and interpreting rheumatologic laboratory tests. J Am Acad Orthop Surg 2003;11:60-67.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In bone defects where host bone support is less than 50%, the failure rate is 70% at 5.1 years. The presence or absence of columns or hip position is of relatively little importance if the supportive bone is not present in at least 50% of the surface area around the future acetabular implant.

<span class="exp-title">Detailed Explanation</span><div markdown="1">By placing the forearm at neutral rotation, as shown in Figures 43c and 43d, the distal fragment has become malrotated by 90 degrees. This is evident by the fact that the bicipital tuberosity is rotated 90 degrees to the radial styloid. Normally, it should be directly opposite (180 degrees) to the radial styloid. The correct alignment was present in the original radiographs shown in Figures 43a and 43b. Another clue to the malrotation in the postreduction radiographs is the difference in the diameters of the opposing radial shafts. To correct this rotational malalignment, the distal fragment needs to be remanipulated into supination so that it is correctly aligned with the supinated proximal radius. Evans EM: Fractures of the radius and ulna. J Bone Joint Surg Br 1951;33:548-561.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Injury to the spinal accessory nerve can occur after penetrating trauma to the shoulder. Blunt trauma may also cause loss of trapezius function. Most commonly, surgical dissection in the posterior triangle of the neck, such as lymph node biopsy, may expose the nerve to possible damage. Surgical repair of the nerve may be considered up to 1 year after injury; after this time muscle transfer is usually associated with a better functional outcome. Steinman SP, Spinner RJ: Nerve problems in the shoulder, in Rockwood CA, Matsen FA, Wirth MA, et al (eds): The Shoulder. Philadelphia, PA, WB Saunders, 2004, vol 2, pp 1013-1015.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The risk of synostosis is imminent with any technique for repairing a distal biceps tendon rupture. However, the risk is quite low for all approaches that avoid exposure of the ulna, including the muscle-splitting two-incision technique.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has sustained high-energy upper extremity and chest injuries. He continues to remain hemodynamically unstable with no obvious thoracic or abdominal injury responsible for bleeding. The pelvic fracture is unlikely to be causing significant bleeding. A scapulothoracic dissociation and possible disruption of one of the great vessels of the upper extremity should be considered. Evaluation of peripheral pulses or blood pressure indices bilaterally in the upper extremities is a simple way to evaluate the need for further work-up. If there is any discrepancy or further concern, angiography of the involved extremity is necessary. Althausen PL, Lee MA, Finkemeier CG: Scapulothoracic dissociation: Diagnosis and treatment. Clin Orthop 2003;416:237-244.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Injuries involving brackish water and shellfish can have devastating consequences caused by Vibrio vulnificus infections. Patients may have a severe invasive infection, with three main clinical features: primary septicemia, wound infection, and gastroenteritis. Antibiotic administration is crucial because mortality rates of up to 50% have been observed with Vibrio septicemia. The current recommendation is to give a third-generation cephalosporin such as ceftazadime. Chiang SR, Chuang YC: Vibrio vulnificus infection: Clinical manifestations, pathogenesis, and antimicrobial therapy. J Microbiol Immunol Infect 2003;36:81-88.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient is showing signs of vertebral artery stroke. The signs of Wallenberg syndrome include those listed above, as well as contralateral loss of pain and temperature sensation throughout the body, an ipsilateral Horner's syndrome, dysphagia, and ataxia. Vertebral artery injuries are not unusual in significant cervical facet injuries. A lesion in the cervical spinal cord is not associated with these symptoms, and an intracranial hemorrhage from trauma is unlikely to present in this manner. Young PA, Young PH: Basic Clinical Neuroanatomy. Baltimore, MD, Williams and Wilkins, 1997, pp 242-243. Hauop JS, et al: The cause of neurologic deterioration after acute cervical spinal cord injury. Spine 2001;26:340-346.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a well-fixed and aligned painful total knee replacement. The success rate of revision knee replacement for pain when no mechanical problem can be identified is approximately 40%. The critical step is to rule out the presence of infection with appropriate laboratory studies and aspiration. If no infection is detected, revision should be avoided. Rand JA: Planning for revision total knee arthroplasty, in Zuckerman JD (ed): Instructional Course Lectures 48. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1999, pp 161-166.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The cross-sectional area of a muscle determines to a great extent the force generated by the muscle. The force of a muscle contraction is controlled by the amount of myofibrils that contract; the greater the amount of contracting myofibrils, the greater the force of contraction. Fiber types have less to do with the force of contraction and more to do with the duration and speed of contraction. Muscle length affects contraction force through the Blix curve. The morphology of a muscle can affect the cross-sectional area by varying the angle of the fibers in relation to the force vector. Conditioning mostly affects duration and fatigability. Buckwalter JA, Mow VC, Ratcliffe A: Restoration of injured or degenerated articular cartilage. J Am Acad Orthop Surg 1994;2:192-201.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The extensor carpi ulnaris tendon is shown subluxated from its tunnel at the ulnar head; this requires disruption of the tendon's subsheath. Rowland SA: Acute traumatic subluxation of the extensor carpi ulnaris tendon at the wrist. J Hand Surg Am 1986;11:809-811.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The histologic features of multiple myeloma are distinctive for this lesion. The plasma cells are round or oval and have an eccentric nucleus and prominent nucleolus. These characteristics and a clear area next to the eccentric nucleus representing the prominent Golgi center are pathognomonic for plasma cells. Lymphoma is in the differential diagnosis; the most frequent types that occur in bone are large cell or mixed small and large cell types. The histologic appearance of the specimen is not consistent with the other choices.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Boden and associates' recent article presents significant evidence that patients with rheumatoid arthritis, neurologic deterioration, and C1-2 instability are more likely to improve after surgery if the posterior alanto-odontoid interval is greater than 10 mm preoperatively. The accepted safe range for the posterior atlanto-odontoid interval is 14 mm. This measurement is believed to better represent the space available for the cord than the anterior alanto-odontoid interval. Garfin SR, Vaccaro AR (eds): Orthopaedic Knowledge Update: Spine. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1997, pp 273-279. Boden SD, Dodge LD, Bohlman HH, Rechtine GR: Rheumatoid arthritis of the cervical spine: A long-term analysis with predictors of paralysis and recovery. J Bone Joint Surg Am 1993;75:1282-1297.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The child has a near complete central physeal arrest of the distal femur and worsening limb-length discrepancy will develop. She is growing at the average rate for the population. The distal femoral physis grows at a rate of roughly 9 mm per year. Girls finish their growth at approximately age 14 years. Thus, at maturity the left leg will be 6.4 cm longer than the right. An angular deformity has not developed at this point and her arrest is central; therefore, angular deformity is unlikely to develop in any plane. Little DG, Nigo L, Aiona MD: Deficiencies of current methods for the timing of epiphysiodesis. J Pediatr Orthop 1996;16:173-179.

<span class="exp-title">Detailed Explanation</span><div markdown="1">A flexion contracture of the elbow is commonly seen in hemiplegic patients following cerebrovascular accidents. Spasticity and myostatic contracture of the joint are both causative factors. In patients with a flexion deformity of less than 90 degrees, musculocutaneous neurectomy is recommended, followed by serial casting to treat any residual deformity. At 9 months after injury, physical therapy will not significantly improve motion. Nerve blocks may be used in the early stages of recovery to facilitate therapy and serial casting.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The elongated anterior process of the calcaneus reaching distally toward the navicular is an abnormal finding. Instead of viewing the rounded, blunt distal anterior process of the calcaneus, a bridge extends to the navicular, albeit incomplete. These findings are consistent with a fibrous coalition. CT can reveal a stress fracture of the calcaneus, arthritis of the subtalar joint with subchondral cysts, or an os peroneal bone disruption in the peroneus longus, but those entities are not shown here. The plantar fascia is intact. Richardson EG: 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 702-732.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The typical mechanism of injury is a fall and the patient grasps something to prevent the fall. This maneuver forces the arm into external rotation against resistance. Kreuz PC, Remiger A, Erggelet C, et al: Isolated and combined tears of the subscapularis tendon. Am J Sports Med 2005;33:1831-1837.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The transverse carpal ligament is the volar boundary of the carpal tunnel. It attaches to the scaphoid and trapezium radially and the pisiform and the hook of the hamate ulnarly. The ulna and trapezoid do not receive attachments of the transverse carpal ligament. Hollinshead W: Anatomy for Surgeons: The Back and Limbs, ed 3. Philadelphia, PA, Harper and Row, 1982, vol 3, pp 471-472.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Most lesions of eosinophilic granuloma are simply observed, but larger aggressive lesions may require curettage and bone grafting. Frequently, biopsy is required to rule out a malignant diagnosis. The differential diagnosis of eosinophilic granuloma is osteomyelitis, Ewing's sarcoma of bone, or osteogenic sarcoma. The biopsy alone can be followed by spontaneous resolution. In some patients, low-dose radiation therapy is used. Chemotherapy or amputation is not indicated for these benign lesions.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The radiographic findings show 30 degrees of talar tilt (severe) and 10 mm of anterior translation that typically involves laxity of both of the major lateral ligaments of the ankle (anterior talofibular and calcaneofibular). There is no evidence of deltoid laxity. Harper MC: Stress radiographs in the diagnosis of lateral instability of the ankle and hindfoot. Foot Ankle 1992;13:435-438.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Much attention has been given to the use of supplemental postoperative analgesia with nonsteroidal anti-inflammatory drugs (NSAIDs), and a significant reduction in narcotic use has been recorded. However, a high failure rate of arthrodesis has been associated with the use of postoperative NSAIDs. Glassman and associates reported 29 cases of pseudarthrosis in 167 patients when ketorolac was used as a postoperative analgesic, whereas only five fusion failures were noted in 121 patients not using ketorolac. Indomethacin and ibuprofen have been shown to adversely affect bone formation in clinical and animal trials. Nicotine has also been shown in a number of studies to decrease the fusion rate. Oxycodone hydrochloride is a synthetic morphine and does not affect the fusion process. Glassman SD, Rose SM, Dimar JR, Puno RM, Campbell MJ, Johnson JR: The effect of postoperative nonsteroidal anti-inflammatory drug administration on spinal fusion. Spine 1998;23:834-838. Deguchi M, Rapoff AJ, Zdeblick TA: Posterolateral fusion for isthmic spondylolisthesis in adults: Analysis of fusion rate and clinical results. J Spinal Disord 1998;11:459-464.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The change noted is focal and confined to the cortex, sparing the opposite side, both lower extremities, and the subcortical waveforms, making all the choices unlikely with the exception of carotid compression with focal cortical ischemia. This may be associated with poor collateral flow from the opposite hemisphere due to an incomplete circle of Willis. Drummond JC, Englander RN, Gallo CJ: Cerebral ischemia as an apparent complication of anterior cervical discectomy in a patient with an incomplete circle of Willis. Anesth Analg 2006;102:896-899.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Radiation-associated sarcomas typically occur at least 5 years following radiation therapy, in the radiation therapy field, and with different histology than the original disease. The radiograph shows a lytic destructive lesion of the medial clavicle. The radiographic differential could include any of the above etiologies. The CT and MRI scans show this same reaction with extension into the adjacent soft tissue and periosteal reaction. These findings eliminate a degenerative process or radiation-induced osteonecrosis but do not distinguish between a neoplastic and infectious process. A PET scan showed marked uptake in the distal clavicle, which is more consistent with a malignant neoplastic process than a reactive process, like that of an infection. These findings, combined with the cellular atypia and bone formation on the biopsy specimen, confirm the diagnosis of radiation-associated sarcoma. In this older patient, radiation-associated sarcoma appears in an unusual location secondary to her previous radiation treatment in that region, which can occur 3 to 50 years after previous radiation therapy. Shaheen M, Deheshi BM, Riad S, et al: Prognosis of radiation-induced bone sarcoma is similar to primary osteosarcoma. Clin Orthop Relat Res 2006;450:76-81.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Severe valgus deformity is frequently accompanied by hypoplasia of the lateral femoral condyle. Posterior referencing instrumentation can substantially internally rotate the femoral component with respect to the transepicondylar axis and Whiteside's line. The femoral component malrotation must be corrected to properly address this problem. Berger RA, Della Valle CJ, Rubash HE: Patellofemoral problems in total knee arthroplasty, in Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, JB Lippincott, 2003, vol 2, pp 1245-1258.

<span class="exp-title">Detailed Explanation</span><div markdown="1">High-level pitchers with symptomatic UCL tears require reconstruction, with autograft being the best studied graft selection. With concomitant ulnar nerve symptoms, a simultaneous ulnar nerve transposition provides good results. Ligament "repairs" and allograft reconstructions have not shown good long-term results. Azar FM, Andrews JR, Wilk KE, et al: Operative treatment of ulnar collateral ligament injuries of the elbow in athletes. Am J Sports Med 2000;28:16-23.

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

<span class="exp-title">Detailed Explanation</span><div markdown="1">The lateral arm flap is based on the posterior radial collateral artery, a branch of the profunda brachial artery. Katsaros J, Tan E, Zoltie N: The use of the lateral arm flap in upper limb surgery. J Hand Surg 1991;16:598-604.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Osteonecrosis of the femoral head is a known complication from the use of rigid intramedullary nails for femoral fractures in adolescents. When the nails are placed through the piriformis fossa, the lateral ascending vessels of the femoral neck may be injured, resulting in osteonecrosis of the femoral head in 1% to 2% of patients. Rigid reamed nails placed into the piriformis fossa are contraindicated in children with open growth plates because the physis is a barrier to blood supply and the ligamentum teres does not provide sufficient vascularity. Alternative fixation methods for femoral fractures in adolescents include external fixation and open reduction and internal fixation. Nailing through the tip of the trochanter may decrease the incidence of this serious complication. Letts M, Jarvis J, Lawton L, et al: Complications of rigid intramedullary rodding of femoral shaft fractures in children. J Trauma 2002;52:504-516. Stans AA, Morrissy RT, Renwick SE: Femoral shaft fracture treatment in patients age 6 to 16 years. J Pediatr Orthop 1999;19:222-228. Buckley SL: Current trends in the treatment of femoral shaft fractures in children and adolescents. Clin Orthop 1997;338:60-73.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Indications for surgical treatment of spondylolisthesis include pain and/or progression of deformity. Specifically, surgery is necessary when there is persistent pain or a neurologic deficit that fails to respond to nonsurgical therapy, there is significant slip progression, or the slip is greater than 50%. For patients with mild spondylolisthesis, in situ posterolateral L5-S1 fusion is adequate. In patients with more severe slips (greater than 50%), extension of the fusion to L4 offers better mechanical advantage. Postoperative immobilization may be achieved with instrumentation, casting, or both. In patients with a slip angle of greater than 45 degrees, reduction of the lumbosacral kyphosis with instrumentation or casting is desirable to prevent slip progression. Laminectomy alone is contraindicated in a child. Nerve root decompression is indicated if radiculopathy is present clinically. Seitsalo S, Osterman K, Hyvarinen H, Tallroth K, Schlenzka D, Poussa M: Progression of spondylolisthesis in children and adolescents: A long-term follow-up of 272 patients. Spine 1991;16:417-421.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a stress fracture of the olecranon; therefore, the most appropriate management is modification of activities below the threshold of symptoms to allow for healing. Ultrasound provides no benefit, and immobilization is not necessary. MRI is not necessary because there is no associated ligamentous injury. Arthroscopy is not indicated. Cabanela ME, Morrey BF: Fractures of the olecranon, in Morrey BF (ed): The Elbow and Its Disorders. Philadelphia, PA, WB Saunders, 2000, pp 365-379.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Numerous surgical approaches have been used for thoracic diskectomy, including the most recent VATS. One of the first approaches described, posterior laminectomy, involves manipulation of the spinal cord, which the other approaches avoid. The posterior approach had dismal results, including further neurologic deterioration and even paralysis. Belanger TA, Emery SE: Thoracic disc disease and myelopathy, in Frymoyer JW, Wiesel SW (eds): The Adult and Pediatric Spine. Philadelphia, PA, Lippincott Williams and Wilkins, 2004, pp 855-864. Benjamin V: Diagnosis and management of thoracic disc disease. Clin Neurosurg 1983;30:577-605. Russell T: Thoracic intervertebral disc protrusion: Experience of 67 cases and review of the literature. Br J Neurosurg 1989;3:153-160.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In this age group of patients with arthrogryposis, open reduction through a medial approach is generally recommended. Open reduction through an anterior approach is reserved for patients in which a medial approach has failed or for older patients who require simultaneous femoral shortening and/or pelvic osteotomy. Closed treatment of unilateral hip dislocation in association with arthrogryposis is rarely successful. In bilateral hip dislocation associated with arthrogrypsis, the consensus is that the hips are best left unreduced because of the difficulty in obtaining excellent clinical and radiographic results bilaterally. Staheli LT, Chew DE, Elliot JS, Mosca VS: Management of hip dislocations in children with arthrogryposis. J Pediatr Orthop 1987;7:681-685. Szoke G, Staheli LT, Jaffe K, Hall JG: Medial-approach open reduction of hip dislocation in amyoplasia-type arthrogryposis. J Pediatr Orthop 1996;16:127-130.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The latissimus dorsi inserts on the humerus metaphysis between the pectoralis major (posterior) and teres major (anterior). Teres minor inserts on the base of the greater tuberosity. Pectoralis minor does not insert on the humerus. Williams PL, Warwick R, Dyson M, Bannister LH: Neurology, in Gray's Anatomy, ed 37. Edinburgh, Scotland, Churchill Livingstone, 1989, pp 1131-1132.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Based on the findings, the treatment of choice is resection of the sternoclavicular joint. Antibiotic therapy, repeat aspirations, hyperbaric oxygen, and simple irrigation and debridement are generally ineffective and associated with a high rate of recurrence.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Results have been satisfactory in many patients; however, at long-term follow-up, examination of the affected shoulder often shows some decrease in range of motion compared with the contralateral side. Although range of motion often improves over time, it does not return to normal in 60% of patients. Pain improves but is often increased compared with the contralateral side. Griggs SM, Ahn A, Green A: Idiopathic adhesive capsulitis: A prospective functional outcome study of nonoperative treatment. J Bone Joint Surg Am 2000;82:1398-1407.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient sustained a high-angle femoral neck fracture. The follow-up clinical findings and radiograph show that she now has a nonunion with failed internal fixation. The joint appears preserved. In a healthy, young patient, arthroplasty of the femoral head, although possible, is not ideal. Excellent healing and function can be obtained in 70% to 80% of patients with femoral neck nonunion with a valgus intertrochanteric osteotomy. Marti RK, Schuller HM, Raaymakers EL: Intertrochanteric osteotomy for non-union of the femoral neck. J Bone Joint Surg Br 1989;71:782-787.

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

<span class="exp-title">Detailed Explanation</span><div markdown="1">The tendon most prone to rupture in a patient with rheumatoid arthritis of the wrist is the extensor digiti quinti. It can be a silent injury since the extensor digitorum communis can provide extension to the fifth finger. The extensor digiti quinti is at high risk since it is overlying the ulnar head where it is prone to attritional rupture (Vaughan-Jackson syndrome). Vaughan-Jackson OJ: Rupture of extensor tendons by attrition at the inferior radioulnar joint: A report of two cases. J Bone Joint Surg Br 1948;30:528-530.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Tillaux and triplane fractures occur in adolescents as the result of an external rotation injury of the ankle. As seen on the CT scan, the growth plate starts to close during adolescence; therefore, growth arrest resulting in limb-length discrepancy or angulation is less of a concern in this age group than achieving joint congruity. The joint should be surgically reduced if displacement is greater than 2 mm to minimize the chances of late arthrosis. Kay RM, Matthys GA: Pediatric ankle fractures: Evaluation and treatment. J Am Acad Orthop Surg 2001;9:268-278. Kling TF Jr: Operative treatment of ankle fractures in children. Orthop Clin North Am 1990;21:381-392.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The short-form 36 is an excellent tool for measuring the patient's perception of treatment outcome because it is a patient-generated, validated assessment of physical, social, and role function, emotional and mental health, energy/fatigue, pain, health perception, and health change. The Nurick criteria is an evaluation of physical function with gradations of ambulation and daily function. The Japanese Orthopaedic Association score gives points for function in activities of daily living but does not assess perception of general health. The neck disability index assesses the impact of neck pain on daily life, and the Odom criteria are the surgeon's evaluations of degree of radicular pain and deficit. Albert TJ, Mesa JJ, Eng K, McIntosh TC, Balderston RA: Health outcome assessment before and after lumbar laminectomy for radiculopathy. Spine 1996;21:960-963. Swiontkowski MF, Buckwalter JA, Keller RB, Haralson R: The outcomes movement in orthopaedic surgery: Where we are and where we should go. J Bone Joint Surgery Am 1999;81:732-740.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has necrotizing fasciitis, a rare and sometimes fatal disease that has many different etiologies. Signs that this is not a normal infection are the worsening clinical symptoms despite IV antibiotics and the systemic symptoms. He needs urgent surgical care before he becomes completely septic and unstable. He needs very aggressive debridement of his tissues. Hyperbaric oxygen and immunoglobulins are only anecdotally helpful, and would only be used after surgery. Fontes RA, Ogilvie CM, Miclau T: Necrotizing soft-tissue infections. J Am Acad Orthop Surg 2000;8:151-158.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Posterior constructs for Scheuermann's kyphosis ideally should extend from the most superior to the most inferior aspect of the Cobb angulation. However, the most distal fusion level must be in a stable or lordotic position to avoid the development of junctional kyphosis. Lowe reported that failure to incorporate the first lordotic segment of the lumbar spine is associated with a higher risk of junctional kyphosis. The first lordotic segment of the lumbar spine is typically at least one level below the distal aspect of the curve as measured by the Cobb technique and most commonly is in the upper part of the lumbar spine. Lowe TG: Scheuermann's disease. Orthop Clin North Am 1999;30:475-487.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a transscaphoid dorsal perilunate dislocation. The radiographs clearly define a dorsal dislocation of the capitolunate joint, and the scaphoid fracture component is easily visible on the AP view. A scaphoid fracture alone is an unlikely diagnosis because of the midcarpal dislocation component. The radiocarpal joint is not dislocated because the lunate is sitting in the lunate fossa of the radius. Isolated radiocarpal dislocations are not associated with a midcarpal disruption. While a midcarpal dislocation is a component of a dorsal perilunate dislocation, this diagnosis does not address the scaphoid fracture. A volar lunate dislocation is not seen because the lunate is reduced in the lunate fossa of the distal radius. Volar lunate dislocations are in the spectrum of injury of perilunate dislocations and fracture-dislocations; however, the radiographs show a transscaphoid dorsal perilunate dislocation. Mayfield JK, Johnson RP, Kilcoyne RK: Carpal dislocations: Pathomechanics and progressive perilunar instability. J Hand Surg Am 1980;5:226-241.

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

<span class="exp-title">Detailed Explanation</span><div markdown="1">Nodular fasciitis is a benign soft-tissue lesion that usually arises from the fascia and is often misdiagnosed as a sarcoma. Desmoid tumors (aggressive fibromatosis) are also benign tumors with a greater tendency for local recurrence. Desmoid tumors have more spindle-shaped fibroblasts in an abundant collagenous matrix. Malignant fibrous histiocytoma is a hypercellular pleomorphic sarcoma more commonly found in adults. The histology is not consistant with a fatty tumor.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In both room temperature air and physiologic fluids, titanium alloys self-passivate or spontaneously form a layer of titanium oxide very rapidly. This layer makes titanium alloys resistant to surface breakdown. Callaghan JJ, Rosenberg AG, Rubash HE, et al (eds): The Adult Knee. Philadelphia, PA, Lippincott, 2003, vol 1, pp 269-278.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The zone of Ranvier provides the earliest increase in strength of the physis. During the first year of life, the zone spreads over the adjacent metaphysis to form a fibrous circumferential ring bridging from the epiphysis to the diaphysis. This ring increases the mechanical strength of the physis. The zone also helps the physis grow latitudinally. In turn, the increased width of the physis helps the physis further resist mechanical forces. The change in shape of the physis to its progressively more undulating form is also a factor in increasing physeal strength, but this occurs over a longer period of time, as the child's activity level increases. The undulations of the physis seen in some growth plates also add to stability but to a lesser extent. The other changes contribute little toward increasing physeal strength. Burkus J, Ogden J: Development of the distal femoral epiphysis: A microscopic morphological investigation of the zone of Ranvier. J Pediatr Orthop 1984;4:661-668.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has posttraumatic arthritis of the elbow; therefore, the treatment of choice is hardware removal and soft-tissue releases with splinting to avoid recurrence of contractures. The combination of pain and stiffness in an elbow that has sustained significant joint surface damage renders it unresponsive to simple soft-tissue releases and heterotopic bone excision. Joint distraction and interposition arthroplasty offer the possibility of maintaining motion and relieving pain as a later salvage procedure. Joint replacement should not be performed in young, active, strong individuals because the prosthesis will fail quickly and complications will develop. Synovectomy and radial head excision are not indicated. Morrey BF: Distraction arthroplasty: Clinical applications. Clin Orthop 1993;293:46-54.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Approximately 75% of people have the artery on the left side between T9 and T11. Its relevance to iatrogenic spinal cord problems is still uncertain. Stambaugh J, Simeone F: Vascular complication in spine surgery, in Herkowitz HH (ed): The Spine, ed 4. Philadelphia, PA, WB Saunders, 1992, p 1715.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Patellar problems currently constitute the largest number of complications after total knee arthroplasty, affecting between 8% and 35% of patients. These problems include patellar instability, fracture, component loosening, surface erosion, and pain. Malalignment, as an isolated reason for revision, is uncommon, yet it contributes to accelerated wear of the components. Joint instability affects up to 6% of patients, and the infection rate in knee arthroplasty is around 1% to 2%. Blasier RB, Matthews LS: Complications of prosthetic knee arthroplasty, in Epps CH (ed): Complications in Orthopaedic Surgery. Philadelphia, PA, JP Lippincott, 1994, pp 1066-1069. Rand JA: The patellofemoral joint in total knee arthroplasty. J Bone Joint Surg Am 1994;76:612-620.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has a displaced burst fracture. Fusion with instrumentation has shown better results than casting alone. Posterior fusion with instrumentation, with sagittal plane correction, yields the best results. Decompression occurs indirectly with correction of the kyphosis. Anterior decompression is unnecessary. Lalonde F, Letts M, Yang JP, et al: An analysis of burst fractures of the spine in adolescents. Am J Orthop 2001;30:115-120. Clark P, Letts M: Trauma to the thoracic and lumbar spine in the adolescent. Can J Surg 2001;44:337-345.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The structure shown is the exiting nerve root at the L3-4 disk, which is the right L3 root.

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

<span class="exp-title">Detailed Explanation</span><div markdown="1">A variety of methodologies have been used to decrease the need for homologous blood transfusions following THA. Some of the effective strategies include preoperative donation of autologous units, intraoperative salvage and recycling, preoperative injection of erythropoietin, and regional anesthesia. Cementless fixation and use of wound drains have been shown to increase the blood loss with THA. Huo MH, Paly WL, Keggi KJ: Effect of preoperative autologous blood donation and intraoperative and postoperative blood recovery on homologous blood transfusion requirement in cementless total hip replacement operation. J Am Coll Surg 1995;180:561-567. Bierbaum BE, Callaghan JJ, Galante JO, Rubash HE, Tooms RE, Welch RB: An analysis of blood management in patients having a total hip or knee arthroplasty. J Bone Joint Surg Am 1999;81:2-10.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Multiple hereditary exostosis and enchondroma commonly present as multiple lesions in the hand. Multiple hereditary exostosis consists of cartilage capped bony exostoses arising from the metaphyseal end of rapidly growing bones. Osteosarcoma and chondrosarcoma rarely appear as multiple lesions. Fracture callus can exhibit enchondral ossification that is usually circumferential, but the radiographic findings are not consistent with fracture. Porter DE, Emerton ME, Villanueva-Lopez F, Simpson AH: Clinical and radiographic analysis of osteochondromas and growth disturbance in hereditary multiple exostoses. J Pediatr Orthop 2000;20:246-250.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The valgus stress at the elbow caused by throwing strains the medial collateral ligament. The medial epicondyle, on which the ligament inserts, is the last ossification center to fuse to the distal humerus, and acute avulsion of the medial epicondyle can occur in adolescents. If the elbow is allowed to heal in a displaced position, valgus instability and loss of elbow extension may result. Valgus instability is especially problematic for the throwing athlete. Surgical treatment with rigid internal fixation is the treatment of choice for displaced medial epicondyle avulsion fractures. Valgus instability is prevented, and the rigid fixation allows for early range of motion. Case SL, Hennrikus WL: Surgical treatment of displaced medial epicondyle fractures in adolescent athletes. Am J Sports Med 1997;25:682-686.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Retrovascular cords are common in Dupuytren's disease and commonly require surgical treatment. Nerve injury in Dupuytren's surgery is an infrequent complication that occurs partly because the digital nerves can be displaced from their normal anatomic relationships by retrovascular cords. The nerves are displaced superficially, toward the center of the digit (palmarly and ulnarly). This displacement is typically seen at the level of the metacarpophalangeal joint.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The MRI scan reveals disruption of the lateral capsule and ligaments with fluid in the soft tissues laterally. Additionally, there is a large bone bruise on the medial femoral condyle. This combination indicates injury to the posterolateral complex. These injuries often have coexisting anterior and/or posterior cruciate ligament injuries. Failure to recognize the posterolateral corner injury can lead to failure of anterior or posterior cruciate ligament reconstructions. LaPrade RF, Gilbert TJ, Bollom TS, et al: The magnetic resonance imaging appearance of individual structures of the posterolateral knee: A prospective study of normal knees and knees with surgically verified grade III injuries. Am J Sports Med 2000;28:191-199.

<span class="exp-title">Detailed Explanation</span><div markdown="1">Several cutting studies have evaluated the primary static restraints and the role of the glenohumeral ligaments in providing static stability. With the arm at the side in adduction, the superior glenohumeral ligament and coracohumeral ligament are the primary restraints to inferior translation. The middle glenohumeral ligament functions with the arm in 45 degrees of abduction and resists anterior translation. The inferior glenohumeral ligament is the primary restraint to anterior translation at 90 degrees of abduction. Warner JJ, Deng XH, Warren RF, et al: Static capsuloligamentous restraints to superior-inferior translation of the glenohumeral joint. Am J Sports Med 1992;20:675-685.

<span class="exp-title">Detailed Explanation</span><div markdown="1">In a child with myelomeningocele, the guiding principle of treatment is to achieve a plantigrade foot by the time the child is ready to stand. The standard clubfoot protocol should be followed, but these children will require an aggressive surgical release to obtain a sufficient correction. Mizel MS, Miller RA, Scioli MW (eds): Orthopaedic Knowledge Update: Foot and Ankle 2. Rosemont, IL, American Academy of Orthopaedic Surgeons, 1998, pp 65-78.

<span class="exp-title">Detailed Explanation</span><div markdown="1">PMMA has no adhesive properties and can be more accurately described as grout than glue. It does not chemically bond to bone or implants; however, mechanical bonding is accomplished with porous or coated components and with cancellous bone. PMMA is approximately three times stronger in compression than in tension. Peak blood levels of monomer are usually seen approximately 3 minutes after the cement is placed. The monomer is cleared by the lungs. Associated hypotension is more closely related to diminished blood volume than to circulating monomer levels. High porosity decreases the tensile and fatigue properties of cement. Manually mixed cement may have porosity as high as 27%. Porosity may be reduced to less than 1% through vacuum mixing or centrifugation of the cement. When adding antibiotics to cement, the compressive and tensile forces are not appreciably decreased, but the overall fatigue strength may be reduced. Canale ST (ed): Campbell's Operative Orthopaedics, ed 9. St Louis, MO, Mosby, 1998, pp 221-224.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The lunotriquetral interosseous ligament stabilizes the lunotriquetral joint. The scapholunate interosseous ligament stabilizes the scapholunate joint. The ulnolunate ligament originates from the base of the ulnar styloid and inserts in the lunate. The ulnotriquetral ligament originates from the base of the ulnar styloid and inserts on the triquetrum. The ulnolunate and the ulnotriquetral ligaments are important stabilizers to the ulnar side of the wrist. The short radiolunate ligament originates on the volar ulnar margin of the distal radius and inserts in the ulnar margin of the lunate. Berger RA: Ligament anatomy, in Cooney WP, Linscheid RL, Dobyns JH (eds): The Wrist, Diagnosis and Operative Management. St Louis, MO, Mosby, 1998, pp 73-105.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The patient has an infected total knee arthroplasty and an interrupted extensor mechanism. A late infection of a total knee arthroplasty in a patient with diabetes mellitus and a virulent organism requires removal of the components, debridement, antibiotic spacers, and surveillance to ensure eradication of the infection. Reconstruction of an incompetent extensor mechanism in an infected knee is extremely unlikely to be successful. Arthrodesis is the procedure of choice if a revision total knee arthroplasty is not likely to succeed. Resection arthroplasty is recommended only as a long-term solution if the patient is medically unable to undergo further surgery. Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgery, 2002, pp 513-536.

<span class="exp-title">Detailed Explanation</span><div markdown="1">The interlocking screws at the proximal end of the rod can act as a stress riser and lead to fracture. Postoperative pain at this level should prompt inclusion of this diagnosis in the differential. Removing the screws following bone union can decrease the chances of this occurring. A short rod that avoids the diaphyseal area may also be beneficial. Rotatory deformity is controlled by the perpendicularly oriented distal transfixion screws. Talar osteonecrosis would be unusual since the dissection can be minimized with an intramedullary rod. Any type of hardware can fail if the construct does not lead to a solid arthrodesis. Nunley JA, Pfeffer GB, Sanders RW, et al (eds): Advanced Reconstruction: Foot and Ankle. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 236-237. Thordarson DB, Chang D: Stress fractures and tibial cortical hypertrophy after tibiotalocalcaneal arthrodesis with an intramedullary nail. Foot Ankle Int 1999;20:497-500.

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