ABOS Pediatric Orthopedics MCQs (Set 1): DDH Questions

Question 1

The inheritance of the deformity shown in Figure 1 is most commonly

Explanation

Cleft hand and cleft foot malformations are commonly inherited as autosomal-dominant traits and are associated with a number of syndromes. An autosomal-recessive and an x-linked inheritance pattern have also been described, but these are much less common and are usually atypical. In the common autosomal-dominant condition, nearly one third of the known carriers of the gene show no hand or foot abnormalities. This is known as reduced penetrance. The disorder may be variably expressed; affected family members often exhibit a range from mild abnormalities in one limb only to severe anomalies in four limbs. Variable expressivity and reduced penetrance can cause difficulty in counseling families regarding future offspring in an affected family. Many patients have a cleft hand that may be caused by the split-hand, split-foot gene (SHFM1) localized on chromosome 7q21.

Question 2

Examination of a 12-year-old girl with bilateral anterior knee pain reveals excessive femoral anteversion and excessive external tibial torsion. The patient has no patellofemoral instability. Nonsurgical management consisting of muscle strengthening and nonsteroidal medication has failed to relieve the patient's pain. Treatment should now consist of

Explanation

Children with symptomatic severe torsional malalignment of the lower extremity and patellofemoral pathology show excessive femoral anteversion and external tibial torsion on physical examination and analysis of gait. The functional effect of this torsional malalignment is centered about the knee joint. If nonsurgical management fails to alleviate patellofemoral pain, definitive surgical treatment should consist of corrective osteotomies, including internal rotation of the distal part of the tibia or external rotation of the femur, or both. Patients with surgical correction by osteotomy show an improved gait pattern and appearance of the extremity and a marked decrease in knee pain. External rotation of the distal part of the tibia or internal rotation of the distal part of the femur worsens the torsional malalignment. No additional soft-tissue realignment procedures, including retinacular release or patellar realignment, are required.

Question 3

Which of the following patients with cerebral palsy is considered the ideal candidate for a selective dorsal rhizotomy?

Explanation

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

Question 4

A 3-year-old boy sustains a complete paralysis following a high thoracic spinal cord injury consistent with a SCIWORA-type injury (spinal cord injury without radiographic abnormality). Subsequent progressive spinal deformity will develop in what percent of patients with this injury?

Explanation

Spinal cord injury in skeletally immature patients almost always leads to the development of paralytic spinal deformity. The age at injury is the most important factor affecting the development of scoliosis. Spinal cord injury that occurs more than 1 year prior to skeletal maturity is almost always followed by the development of scoliosis. In one study, scoliosis developed in 100% of children who were younger than age 10 years at the time of spinal cord injury. Scoliosis can occur after injury at any level. Spasticity is often a contributing factor. Up to two thirds of patients who have paralytic scoliosis prior to skeletal maturity will eventually require surgery for curve control. Mayfield JK, Erkkila JC, Winter RB: Spine deformity subsequent to acquired childhood spinal cord injury. J Bone Joint Surg Am 1981;63:1401-1411. Lancourt JE, Dickson JH, Carter RE: Paralytic spinal deformity following traumatic spinal cord injury in children and adolescents. J Bone Joint Surg Am 1981;63:47-53.

Question 5

A 12-year-old girl has progressive development of cavus feet. Examination reveals slightly diminished vibratory sensation on the bottom of the foot. Reflexes are 1+ at the knees and ankles. Motor examination shows that all muscles are 5/5 in the foot, except the peroneal and anterior tibial muscles are rated as 4+/5. Which of the following studies is considered most diagnostic?

Explanation

The patient most likely has a form of Charcot-Marie-Tooth disease, or hereditary motor sensory neuropathy (HMSN). The most common varieties can now be diagnosed by DNA testing. Mutations have been detected in the peripheral myelin protein-22 (PMP-22) gene in HMSN type IA and in the connexin gene in the x-linked HMSN. Specific DNA diagnosis is useful in genetic counseling. Routine chromosomal testing most likely would not detect these mutations. Nerve conduction velocity study results are normal in some types of HMSN, and delayed nerve conduction, when found, indicates a peripheral neuropathy but does not specify the type or inheritance pattern. Biopsy of the sural nerve or of the quadriceps can be informative in some patients, but is not as specific as DNA testing. These procedures are most often reserved for patients with negative DNA test results. Chance PF: Molecular genetics of hereditary neuropathies. J Child Neurol 1999;14:43-52.

Question 6

A 2-year-old girl was born with the toe deformity shown in Figure 2. She has difficulty wearing shoes despite having adequate room in the toe box. Management at this time should consist of

Explanation

The patient has a congenital curly toe deformity of the third toe, and tenotomy of the toe flexors is highly effective for this problem. Stretching and taping are ineffective for this deformity. The position of the second toe is secondary; therefore, procedures on that toe are unnecessary and ineffective. The flexor to extensor transfer is a more complicated procedure that produces negligible results, or may even worsen the deformity. Resection arthroplasty is contraindicated because it causes abnormal growth of the toes. Hamer AJ, Stanley D, Smith TW: Surgery for curly toe deformity: A double-blind, randomized, prospective trial. J Bone Joint Surg Br 1993;75:662-663. Ross ER, Menelaus MB: Open flexor tenotomy for hammer toes and curly toes in childhood. J Bone Joint Surg Br 1984;66:770-771.

Question 7

Figure 3 shows the radiograph of an asymptomatic 10-year-old boy. Management should consist of

Explanation

Asymptomatic spondylolysis in a child or adolescent should be observed for the possible development of spondylolisthesis, but no other active intervention is needed. The initial treatment of choice for symptomatic spondylolysis includes rest and activity modifications, nonsteroidal anti-inflammatory drugs, physical therapy, bracing, and casting. Immobilization with a TLSO or pantaloon spica cast may permit healing of an acute pars fracture. Rarely, surgical treatment may be necessary. Surgical options include posterolateral L5-S1 fusion or direct repair of the pars defect. Pizzutillo PD, Hummer CD III: Nonoperative treatment for painful adolescent spondylolysis or spondylolisthesis. J Pediatr Orthop 1989;9:538-540.

Question 8

A 12-year-old girl has had lower back pain for the past 6 months that interferes with her ability to participate in sports. She denies any history of radicular symptoms, sensory changes, or bowel or bladder dysfunction. Examination reveals a shuffling gait, restriction of forward bending, and tight hamstrings. Radiographs show a grade III spondylolisthesis of L5 on S1, with a slip angle of 20 degrees. Management should consist of

Explanation

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.

Question 9

Figures 4a through 4c show the clinical photographs and radiographs of a 12-month-old boy who has progressive difficulty wearing shoes because of the length of the second toe, as well as width of the forefoot. Management should consist of

Explanation

The patient has macrodactyly involving the second ray, with significant enlargement of the width and height of the foot. The radiographs show widening of the interval between the first and second metatarsal and between the second and third metatarsal. With this degree of involvement, amputation of the second ray with excision of the overgrowth of affected soft tissue provides the most consistent desired reduction in foot size. A threaded Steinmann pin should be inserted across the remaining metatarsals until healing has occurred. Patients with macrodactyly should be examined to exclude neurofibromatosis type 1 and Klippel-Trenaunay-Weber syndrome.

Question 10

Figures 5a and 5b show the radiographs of an 11-year-old boy who felt a pop and immediate pain in his right knee as he was driving off his right leg to jam a basketball. Examination reveals that the knee is flexed, and the patient is unable to actively extend it or bear weight on that side. There is also a large effusion. Management should include

Explanation

Fractures through the cartilage on the inferior pole of the patella, the so-called sleeve fracture, are often difficult to diagnose because of the paucity of ossified bone visible on the radiographs. If the fracture is missed and the fragments are widely displaced, the patella may heal in an elongated configuration that may result in compromise of the extensor mechanism function. The treatment of choice is open reduction and internal fixation using a tension band wire technique to achieve close approximation of the fragments and restore full active knee extension. Heckman JD, Alkire CC: Distal patellar pole fractures: A proposed common mechanism of injury. Am J Sports Med 1984;12:424-428.

Question 11

A 2-year-old child has been referred for management of congenital kyphosis. Neurologic examination is normal, and radiographs show a type I congenital kyphosis. Which of the following anomalies is seen in the MRI scan shown in Figure 6?

Explanation

There is a high incidence of intraspinal anomalies in patients with congenital scoliosis and kyphosis. Bradford and associates reported an incidence rate of 38% in 42 patients. The MRI scan shows that the filum terminale is thickened and adherent distally in the spinal canal. Although the conus is at L1, which may be normal, neurologic dysfunction may occur with further growth. There are no signals of high intensity within the cord that would suggest a syrinx. A Chiari II malformation would be found in the upper cervical region, not shown in this MRI scan. Meningocele and diastematomyelia are not present. Bradford DS, Heithoff KB, Cohen M: Intraspinal abnormalities and congenital spine deformities: A radiographic and MRI study. J Pediatr Orthop 1991;11:36-41.

Question 12

A 15-year-old boy with a type I hereditary sensory motor neuropathy (Charcot-Marie-Tooth disease) reports recurrent ankle sprains and significant pain in the hindfoot and midfoot despite orthotic management. Examination reveals that he walks with a drop foot and has dynamic clawing of the toes. Clinical photographs of the left foot are shown in Figure 7. Management should consist of

Explanation

The clinical photographs show a patient with a type I hereditary sensory motor neuropathy who has cavus feet with a flexible hindfoot. The Coleman block test shows that the hindfoot corrects into valgus. To prevent progressive cavus, patients with this condition may benefit from soft-tissue releases at a younger age while the foot is flexible. Once there is fixed deformity, combined soft-tissue and bone procedures usually are necessary. Metatarsal osteotomies will correct the cavus, but will do nothing for the drop foot. Transfer of the extensor hallucis longus to the neck of the first metatarsal and modified transfer of the extensor digitorum longus to the dorsum of the foot will prevent further claw toes and improve foot dorsiflexion. Anterior transfer of the posterior tibialis tendon will also aid in dorsiflexion. Calcaneal osteotomy should be reserved for fixed hindfoot varus that does not correct with block testing, and triple arthrodesis should be avoided as long as possible because the long-term outcome is poor. Beaty JH (ed): Orthopaedic Knowledge Update 6. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1999, pp 235-245. Coleman SS: Complex Foot Deformities in Children. Philadelphia, Pa, Lea & Febiger, 1983, pp 147-165.

Question 13

Figures 8a through 8d show the radiographs and CT scans of a 14-year-old girl who has a painful, rigid planovalgus foot. Management consisting of arch supports and anti-inflammatory drugs failed to provide relief. A below-knee walking cast resulted in pain resolution, but she now reports that the pain has recurred. Management should now consist of

Explanation

Tarsal coalitions commonly present in the preadolescent age group as a rigid, planovalgus foot. Small coalitions of the calcaneonavicular joint or the middle facet of the talocalcaneal joint can be excised with interposition of fat or muscle tissue. Isolated calcaneocuboid joint coalitions are very rare. This patient has an associated large talocalcaneal coalition; therefore, resection is contraindicated. Surgery is warranted after failure of nonsurgical management, and because of the involvement of two joints, the only viable option for the severely symptomatic foot is triple arthrodesis. Vincent KA: Tarsal coalition and painful flatfoot. J Am Acad Orthop Surg 1998;6:274-281.

Question 14

Figures 9a and 9b show the spinal radiographs of a 3-year-old child with short limb dwarfism. The lateral radiograph is obtained with maximal lumbar extension. Management should consist of

Explanation

The patient has kyphosis in association with achondroplasia. The AP radiograph shows decreased interpedicular distance at the lower lumbar vertebrae, a feature considered to be a distinctive sign of achondroplasia. Most patients with achondroplasia have kyphosis, and this usually resolves spontaneously. When the fixed component is greater than 30 degrees, however, brace treatment is recommended. Spinal fusion is seldom required.

Question 15

A 10-year-old boy with severe hemophilia A (factor VIII) sustained an injury to his right forearm 2 hours ago when a classmate fell on his arm during a scuffle. Examination reveals moderate swelling in the forearm, decreased sensation in the distribution of the median and ulnar nerves, and pain on passive extension of the fingers. What is the most appropriate sequence of treatment?

Explanation

The patient has severe hemophilia with a volar forearm hemorrhage and an emerging compartment syndrome. Therefore, it is critical to normalize the clotting deficiency as the first step in treatment. In a patient who has a factor VIII level of less than 1% and no inhibitors to factor VIII, transfusion with 4 unit/kg will typically raise the factor VIII level to 100%. Continuous transfusion can then be used to maintain this level. Compartment pressures can be safely measured after infusion of factor VIII. Because the hemorrhage is of limited duration and any surgery is considered serious in a patient with hemophilia, the compartment pressure should be measured before making a decision regarding a fasciotomy. However, it is important to note that the use of factor VIII concentrates allows both emergency and elective surgery provided that adequate hematology backup is available. Splinting the elbow and wrist in flexion reduces the pressure in the volar compartments, protects the forearm from further trauma, and makes the patient more comfortable. Greene WB: Diseases related to the hematopoietic system, in Morrissy RT, Weinstein SL (eds): Lovell & Winter's Pediatric Orthopaedics, ed 4. Philadelphia, Pa, Lippincott-Raven, 1996, pp 345-391. Greene WB, McMillan CW: Nonsurgical management of hemophilic arthropathy, in Barr JS (ed): Instructional Course Lectures 38. Park Ridge, Ill, American Academy of Orthopaedic Surgeons, 1989, pp 367-381.

Question 16

Figures 10a and 10b show the radiographs of an athletic 9-year-old boy who has activity-related anterior knee pain with intact active knee extension. Examination reveals tenderness to palpation over the inferior pole of the patella. There is no effusion or ligamentous instability. Initial management should consist of

Explanation

The radiographs show fragmentation of the inferior pole of the patella. This finding, along with the clinical presentation, is most consistent with Sindig-Larsen-Johansson disease. This is an overuse syndrome commonly seen in boys ages 9 to 11 years. The differential diagnosis includes bipartite patella and patellar sleeve fracture. Like most overuse syndromes, Sindig-Larsen-Johansson disease responds to activity modification and nonsteroidal anti-inflammatory drugs. While symptoms usually resolve with short periods of activity restriction, radiographic findings may persist. Stanitski CL: Anterior knee pain syndromes in the adolescent. J Bone Joint Surg Am 1993;75:1407-1416.

Question 17

A 2-week-old infant has been referred for evaluation of nonmovement of the left hip. History reveals that the patient was delivered 6 weeks premature by cesarean section. Examination reveals no fever, and there is mild swelling of the thigh. Passive movement of the hip appears to elicit tenderness and very limited hip motion. A radiograph of the pelvis shows mild subluxation of the left hip. The next step in evaluation should consist of

Explanation

The diagnosis of bone and joint sepsis in a newborn is difficult because of the relative lack of obvious signs and symptoms. Fever is usually absent. A study of 34 newborns with osteomyelitis identified prematurity and delivery by cesarean section as predisposing factors. In that study, the most common clinical findings were pseudoparalysis, local swelling, and pain on passive movement. Because early diagnosis is so important, any infant who exhibits these findings should be suspected as having bone or joint sepsis. Once the area of involvement is identified, aspiration is mandatory. In newborns who have an infection about the hip, radiographs may reveal subluxation. In this patient, septic arthritis must be ruled out by aspiration of the hip. Developmental dysplasia of the hip is not painful and is not accompanied by localized swelling. If no purulent material is obtained at the time of hip aspiration, an arthrogram should be obtained to rule out epiphysiolysis of the proximal femur. Because the area of involvement has been identified by clinical examination, a gallium scan or MRI scan of the spine is not indicated. Knudsen CJ, Hoffman EB: Neonatal osteomyelitis. J Bone Joint Surg Br 1990;72:846-851.

Question 18

Figure 11 shows the lateral radiograph of a 16-year-old boy who has been unable to participate in sports activities because of pain in the anterior aspect of the knee. He states that the pain is aching in nature and is located in the region of the tibial tuberosity. He denies having joint effusion or symptoms of instability. Management should consist of

Explanation

The prognosis for most patients with Osgood-Schlatter disease is good. When the secondary ossification center unites with the main body of the tibial tubercle, the patellar tendon has a more rigid anchor, and heterotopic ossification and its associated reaction often become quiescent. However, even after closure of the growth plates, some patients have persistent symptoms. Excision of the ossicle and prominence of the tibial tuberosity decompresses the patellar tendon and allows most patients to resume sports activities. Nonsurgical modalities are ineffective. Better results have been reported after excision than after drilling of the tubercle. Excision of the ossicle is not indicated prior to skeletal maturity because symptoms will resolve in most patients when the secondary ossification center unites. Flowers MJ, Bhadreshwar DR: Tibial tuberosity excision for symptomatic Osgood-Schlatter disease. J Pediatr Orthop 1995;15:292-297.

Question 19

A 10-lb, 2-oz infant who was born via a difficult breech delivery 12 hours ago is now being evaluated for hip pain. Although the infant is resting comfortably, examination reveals that the patient is not moving the right lower extremity and manipulation of the right hip causes the infant to cry. The Galeazzi sign is positive. An AP radiograph of the pelvis shows proximal and superior migration of the right proximal femoral metaphysis. What is the most likely diagnosis?

Explanation

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

Question 20

A 10-year-old girl has been referred for evaluation of a prominence at the lower cervical spine. The patient is asymptomatic, and the examination reveals no evidence of neurologic abnormality. A radiograph and CT scans are shown in Figures 12a through 12c. What is the most likely diagnosis?

Explanation

Tuberculosis is uncommon in the cervical spine but has a relatively greater incidence in young children. In a review of 40 patients with lower cervical spine involvement (C2 to C7), 24 were younger than age 10 years at presentation. In children, the disease is characterized by more extensive involvement with the formation of large abscesses. In older patients with lower cervical tuberculosis, the disease is more localized but is more likely to cause paraplegia. Four-drug antituberculosis therapy should be used. For patients with pain or neurologic dysfunction, anterior excision of diseased bone and grafting are indicated. Whether vertebral body excision and grafting should be done in an asymptomatic 10-year-old child is debatable. The CT scan shows a large "cold" abscess that is partially calcified. Hsu LC, Leong JC: Tuberculosis of the lower cervical spine (C2 to C7): A report on 40 cases. J Bone Joint Surg Br 1984;66:1-5.

Question 21

Which of the following types of iliac osteotomy provides the greatest potential for increased coverage?

Explanation

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.

Question 22

The mother of a 26-month-old boy reports that he has been unwilling to bear weight on his left lower extremity since he awoke this morning. She denies any history of trauma. He has a temperature of 99.4 degrees F (37.4 degrees C), and examination reveals that abduction of the left hip is limited to 30 degrees. Laboratory studies show a WBC of 11,000/mm3 and an erythrocyte sedimentation rate of 22 mm/h. A radiograph of the pelvis is shown in Figure 13. Management should consist of

Explanation

The most likely diagnosis is transient synovitis. Initial management should consist of bed rest and serial observation to rule out atypical septic arthritis of the hip. In an unreliable family situation, hospitalization for bed rest and observation may be indicated. Other disorders such as proximal femoral osteomyelitis, leukemia, juvenile rheumatoid arthritis, pelvic osteomyelitis, diskitis, and arthralgia secondary to other inflammatory disorders should be considered. However, these disorders are unlikely because of the paucity of abnormal clinical signs exhibited by the patient. On the other hand, transient synovitis of the hip in children is a diagnosis of exclusion; other possibilities should be explored if the patient's symptoms do not follow a typical course and resolve in 4 to 21 days.

Question 23

A 10-year-old girl with a monoarticular pattern of juvenile rheumatoid arthritis (JRA) has had a 3-cm limb-length discrepancy since age 8 years when inflammation in the right knee came under good medical control. Because her right leg is longer, the patient states that she would like her legs to be close to equal in length in the future. A growth-remaining chart is shown in Figure 14. Management should consist of

Explanation

In a subgroup of patients with monoarticular JRA and a limb-length discrepancy that developed before the age of 9 years, Simon and associates showed that a subsequent growth deceleration on the affected side may correct a large part of the difference in length. This possibility would make surgery unnecessary and should prompt further observation. Simon S, Whiffen J, Shapiro F: Leg-length discrepancies in monoarticular and pauciarticular juvenile rheumatoid arthritis. J Bone Joint Surg Am 1981;63:209-215.

Question 24

A 14-year-old girl with polyarticular juvenile rheumatoid arthritis (JRA) has severe neck pain and reports the onset of urinary incontinence. A lateral radiograph and lateral tomogram of the cervical spine are shown in Figures 15a and 15b. An MRI scan of the upper cervical spine is shown in Figure 15c. Management should consist of

Explanation

The plain radiograph and tomogram show an abnormality of the upper cervical spine, with erosion of the dens. The MRI scan shows evidence of cord impingement. The cervical spine is frequently involved in polyarticular JRA. Stiffness and autofusion are commonly seen, but C1-2 instability can also occur secondary to synovitis and bony erosion. Basilar invagination is rare in JRA. There is no consensus regarding fusion in the asymptomatic patient. In patients with symptoms and neurologic signs, C1-2 posterior fusion is indicated. Fried JA, Athreya B, Gregg JR, Das M, Doughty R: The cervical spine in juvenile rheumatoid arthritis. Clin Orthop 1983;179:102-106.

Question 25

Figures 16a and 16b show the radiographs of an otherwise healthy 3 1/2-year-old boy who has an isolated deformity of the left leg. Definitive primary treatment of this condition should consist of

Explanation

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

Question 26

A 3-month-old female with developmental dysplasia of the hip (DDH) is being treated with a Pavlik harness. During a follow-up visit, the mother notes the child is no longer kicking her left leg. Examination reveals absent active knee extension on the left. What is the most appropriate next step in management?

Explanation

The patient has developed a femoral nerve palsy, a known complication of Pavlik harness treatment caused by excessive hip flexion. The appropriate management is immediate discontinuation of the harness to allow for nerve recovery. Once neurologic function returns, alternative treatments such as rigid bracing or closed reduction should be considered.

Question 27

A 6-week-old female infant undergoes a screening hip ultrasound. The alpha angle is 45 degrees and the beta angle is 80 degrees, indicating a laterally displaced cartilage roof. What is the most appropriate next step in management?

Explanation

An alpha angle of less than 50 degrees with a laterally displaced cartilage roof indicates a Graf Type III dysplastic hip. This requires immediate treatment with a Pavlik harness to achieve and maintain concentric reduction. Observation is only appropriate for physiologically immature hips (Graf IIa) with an alpha angle of 50-59 degrees in infants under 3 months of age.

Question 28

A 13-year-old boy sustains an ankle injury resulting in a juvenile Tillaux fracture. Which of the following describes the normal sequence of closure of the distal tibial physis, predisposing the patient to this specific fracture pattern?

Explanation

The distal tibial physis closes in a predictable sequence: central, then medial, and finally lateral. The anterolateral portion is the last to close, leaving it vulnerable to avulsion by the anterior inferior tibiofibular ligament during external rotation injuries (juvenile Tillaux fracture).

Question 29

A 12-year-old girl presents with a painless scoliotic deformity. Radiographs reveal a 35-degree left-sided thoracic curve. Neurologic examination is unremarkable. What is the most appropriate next step in evaluation?

Explanation

A left-sided thoracic curve in adolescent idiopathic scoliosis is an atypical pattern and carries a higher risk of underlying neural axis abnormalities, such as a syrinx or Chiari malformation. Therefore, a total spine MRI is indicated even in the absence of neurologic symptoms. Right-sided thoracic curves are the typical pattern for adolescent idiopathic scoliosis.

Question 30

Which of the following congenital spinal anomalies carries the highest risk of scoliotic curve progression and typically requires early surgical intervention?

Explanation

A unilateral unsegmented bar with a contralateral hemivertebra has the highest risk of curve progression in congenital scoliosis, approaching 100%. This severe progression is due to tethering on one side with active growth on the contralateral side, usually necessitating early spinal fusion. Other anomalies like block vertebrae have a much lower progression risk.

Question 31

A 6-week-old female is treated with a Pavlik harness for developmental dysplasia of the hip. At the 2-week follow-up, the mother notes the child is no longer kicking her leg on the affected side. On examination, there is decreased active knee extension. What is the most appropriate next step in management?

Explanation

The scenario describes a femoral nerve palsy, a known complication of hyperflexion in a Pavlik harness. The appropriate management is to adjust the anterior straps to decrease hip flexion or temporarily remove the harness until nerve function recovers.

Question 32

Which of the following ultrasound findings is most consistent with a normal infant hip at 6 weeks of age?

Explanation

According to the Graf classification for developmental dysplasia of the hip, a normal infant hip (Type I) is characterized by an alpha angle greater than 60 degrees and a beta angle less than 55 degrees, with femoral head coverage greater than 50%.

Question 33

A 13-year-old girl with adolescent idiopathic scoliosis presents for evaluation. Radiographs reveal a right thoracic curve of 35 degrees. Her Risser sign is 1, and she is premenarcheal. What is the most appropriate management?

Explanation

Full-time bracing (TLSO) is indicated for immature patients (Risser 0-2, premenarcheal) with idiopathic curves between 25 and 45 degrees. It has been shown to significantly decrease the risk of curve progression to the surgical threshold.

Question 34

A 14-year-old boy sustains a Salter-Harris type III fracture of the medial malleolus. The horizontal component of the fracture typically propagates through which of the following anatomic zones of the physis?

Explanation

Salter-Harris fractures typically propagate through the structurally weak zone of hypertrophy of the physis. A type III fracture then exits vertically through the epiphysis, involving the joint space.

Question 35

An 18-month-old child presents with untreated developmental dysplasia of the right hip. Closed reduction is attempted but is unsuccessful due to soft tissue interposition. Which of the following structures is most commonly a block to closed reduction in this setting?

Explanation

Common blocks to closed reduction in DDH include an inverted limbus, hypertrophied ligamentum teres, contracted transverse acetabular ligament, and a constricted iliopsoas tendon.

Question 36

In the evaluation of infantile idiopathic scoliosis, which of the following radiographic parameters is the most reliable predictor of curve progression?

Explanation

The rib-vertebra angle difference (RVAD) of Mehta is the most reliable predictor of progression in infantile idiopathic scoliosis. An RVAD > 20 degrees strongly indicates a progressive curve requiring intervention.

Question 37

A 6-year-old girl is diagnosed with congenital scoliosis due to a fully segmented unilateral hemivertebra at T8. Which of the following imaging studies is most critical to obtain during her initial workup?

Explanation

Congenital scoliosis is frequently associated with other VACTERL anomalies. Up to 30% of patients have genitourinary abnormalities, making a screening renal ultrasound critical in the initial evaluation.

Question 38

A 15-year-old boy undergoes posterior spinal fusion for adolescent idiopathic scoliosis. During deformity correction, somatosensory evoked potentials (SSEPs) are lost in the bilateral lower extremities, while motor evoked potentials (MEPs) remain intact. What is the most likely cause?

Explanation

SSEPs monitor the posterior columns (sensory), while MEPs monitor the anterior corticospinal tracts (motor). Loss of SSEPs with intact MEPs suggests compromise of the posterior columns, often due to direct mechanical stretching or compression during correction.

Question 39

A 14-year-old girl presents with an acute distal tibial fracture. Radiographs show a Salter-Harris type III fracture of the anterolateral distal tibial epiphysis. What is the mechanism of injury and the deforming force?

Explanation

This describes a juvenile Tillaux fracture, caused by an external rotation force. The anterior inferior tibiofibular ligament (AITFL) avulses the anterolateral distal tibial epiphysis, which is the last portion of the physis to close.

Question 40

A 5-year-old boy presents with a 40-degree left thoracic scoliosis. MRI reveals a syrinx extending from T4 to T10. Which of the following curve characteristics most strongly suggested the presence of an underlying neural axis abnormality?

Explanation

Left thoracic curves, rapid progression, presentation at a young age, and associated neurologic findings are red flags in idiopathic scoliosis. A left thoracic curve warrants an MRI to rule out neuroaxial abnormalities like a syrinx or Chiari malformation.

Question 41

Which pelvic osteotomy for DDH provides primarily anterior and lateral coverage by hinging on the pubic symphysis without changing the shape of the acetabulum?

Explanation

The Salter innominate osteotomy is a redirectional osteotomy that hinges at the pubic symphysis. It improves anterior and lateral coverage without altering the volume or shape of the acetabulum.

Question 42

A 12-year-old boy presents with a triplane fracture of the distal tibia. Which of the following best describes the typical fracture planes on radiographs?

Explanation

A classic triplane fracture consists of a coronal plane fracture through the posterior metaphysis, a sagittal plane fracture through the epiphysis, and a transverse plane fracture through the physis.

Question 43

A 9-year-old boy is found to have a physeal bar across the central 30% of his distal femoral physis following a previous Salter-Harris type II fracture. He has a 2 cm leg length discrepancy and 4 years of remaining growth. What is the most appropriate surgical management?

Explanation

Physeal bar resection is indicated when the bar occupies less than 50% of the cross-sectional area of the physis and the child has at least 2 years of remaining growth. Interposition material is used to prevent reformation.

Question 44

In a child with Duchenne muscular dystrophy, what is the most common indication for spinal fusion surgery for scoliosis?

Explanation

In Duchenne muscular dystrophy, spinal fusion is typically recommended when the curve exceeds 20 to 30 degrees in a non-ambulatory (wheelchair-dependent) patient. Surgery is performed early to halt progression, maintain sitting balance, and prevent severe pulmonary decline.

Question 45

An 8-year-old girl with Neurofibromatosis Type 1 presents with a sharp, short-segment thoracic scoliosis of 45 degrees. Radiographs show rib penciling and vertebral scalloping. What is the recommended treatment?

Explanation

Dystrophic scoliosis in NF-1 is characterized by short, sharp curves, rib penciling, and dural ectasia. These curves progress rapidly and do not respond to bracing; early anterior and posterior spinal fusion is recommended to achieve solid arthrodesis.

Question 46

A newborn is examined in the nursery. The examiner places the infant's hips in 90 degrees of flexion and gently abducts them while applying an anteriorly directed force on the greater trochanter, resulting in a palpable "clunk." What is this provocative test called?

Explanation

The Ortolani maneuver reduces a dislocated hip by elevating the greater trochanter and abducting the hip. The Barlow maneuver attempts to dislocate a reducible hip by applying posterior force during adduction.

Question 47

A 2-year-old boy presents with developmental dysplasia of the hip. A Pemberton osteotomy is planned. What is the primary hinge point for this osteotomy?

Explanation

The Pemberton osteotomy is an incomplete pericapsular osteotomy that hinges on the flexible triradiate cartilage. It changes the shape and volume of the acetabulum, providing primarily anterior and lateral coverage.

Question 48

A 14-year-old girl with adolescent idiopathic scoliosis has a major thoracic curve of 55 degrees. On the lateral radiograph, her thoracic kyphosis is measured at +15 degrees. According to the Lenke classification, what is her sagittal modifier?

Explanation

The Lenke classification sagittal modifiers are based on the T5-T12 thoracic kyphosis: minus (-) is < +10 degrees, normal (N) is +10 to +40 degrees, and plus (+) is > +40 degrees.

Question 49

A 10-year-old boy sustains a Salter-Harris II fracture of the distal femur. What is the most common significant complication associated with this specific injury?

Explanation

Distal femoral physeal fractures have a high rate of complications, with growth arrest occurring in up to 50% of cases. This can lead to significant leg length discrepancies or angular deformities due to the high growth potential of this physis.

Question 50

The "safe zone" of Ramsey in the treatment of DDH with a spica cast is defined as the position between:

Explanation

Ramsey's safe zone for DDH reduction is the arc of abduction between the angle of redislocation (when the hip adducts) and the angle of maximal abduction. Immobilization within this zone minimizes the risk of both redislocation and avascular necrosis.

Question 51

A 6-week-old female infant, born in breech presentation, undergoes a screening hip ultrasound. The alpha angle is measured at 45 degrees, and the beta angle is 80 degrees. What is the most appropriate next step in management?

Explanation

Graf type IIc or III indicates dysplasia or subluxation based on an alpha angle < 60 degrees and beta angle > 77 degrees. Treatment with a Pavlik harness is indicated to promote acetabular remodeling.

Question 52

A 3-month-old infant is being treated with a Pavlik harness for developmental dysplasia of the hip. The parents report that the child has stopped kicking the affected leg. On examination, there is decreased active knee extension. Which of the following harness adjustments is required?

Explanation

Hyperflexion of the hips in a Pavlik harness can cause femoral nerve palsy due to compression against the rim of the pelvis. Decreasing the flexion of the anterior strap relieves this compression.

Question 53

An 18-month-old girl presents with a painless limp and a positive Trendelenburg sign on the right. Radiographs reveal a dislocated right hip with a false acetabulum and breaking of Shenton's line.

What is the most appropriate definitive management?

Explanation

Children over 18 months of age with a dislocated hip typically have significant soft tissue contractures and acetabular dysplasia. Open reduction, often combined with pelvic or femoral osteotomies, is required to achieve and maintain concentric reduction.

Question 54

Following closed reduction of a dysplastic hip in a 9-month-old, the surgeon applies a spica cast. To minimize the risk of avascular necrosis of the femoral head, the hip should NOT be placed in which of the following positions?

Explanation

Excessive abduction (>60 degrees) during spica casting for DDH significantly increases the risk of avascular necrosis. The safe zone of Ramsey limits abduction to avoid compressing the medial circumflex femoral vessels.

Question 55

A 12-year-old girl presents with adolescent idiopathic scoliosis. She has a 20-degree right thoracic curve. She has not reached menarche. Which of the following radiographic parameters indicates the highest risk for curve progression?

Explanation

A Risser grade of 0 indicates that ossification of the iliac apophysis has not yet begun, implying significant remaining spinal growth. This is the strongest radiographic predictor for curve progression in adolescent idiopathic scoliosis.

Question 56

A 13-year-old girl is evaluated for scoliosis. Radiographs show a 32-degree right thoracic curve. She is premenarchal, and her Risser grade is 1.

What is the most appropriate management?

Explanation

Bracing is indicated for skeletally immature patients (Risser 0-2) presenting with curve magnitudes between 25 and 45 degrees. A TLSO brace aims to halt curve progression during the adolescent growth spurt.

Question 57

A 6-month-old infant is diagnosed with infantile idiopathic scoliosis with a 25-degree left thoracic curve. The rib-vertebral angle difference (RVAD) of Mehta is measured at 25 degrees. What is the expected natural history of this condition?

Explanation

In infantile idiopathic scoliosis, a rib-vertebral angle difference (RVAD) of Mehta > 20 degrees strongly predicts a progressive curve. These progressive curves often require early intervention with serial Mehta casting.

Question 58

Which of the following congenital spinal anomalies has the highest rate of progression and warrants early prophylactic in situ fusion?

Explanation

A unilateral unsegmented bar with a contralateral hemivertebra creates a severe growth imbalance. This deformity has the highest progression rate among congenital scoliosis types and requires early prophylactic surgical fusion.

Question 59

A 4-week-old infant is treated with a Pavlik harness for a dislocated left hip. After 3 weeks of strict compliance, ultrasound reveals the hip remains completely dislocated. What is the most appropriate next step in management?

Explanation

Continuing a Pavlik harness beyond 3-4 weeks in a persistently dislocated hip increases the risk of 'Pavlik harness disease' and acetabular posterior lip damage. The most appropriate next step is to transition to a rigid abduction orthosis or proceed with closed reduction and spica casting.

Question 60

In the Lenke classification system for Adolescent Idiopathic Scoliosis, a proximal thoracic curve is defined as structural if the residual Cobb angle on a side-bending radiograph is at least:

Explanation

The Lenke classification defines a structural curve as one having a residual Cobb angle of 25 degrees or greater on lateral side-bending radiographs, or a regional kyphosis of 20 degrees or more.

Question 61

A 12-year-old boy sustains a completely displaced Salter-Harris type II fracture of the distal femur. Which of the following factors is most strongly predictive of subsequent premature physeal closure?

Explanation

Distal femoral physeal fractures carry a very high rate of growth arrest (up to 50%). The initial severity of the trauma, as indicated by the initial degree of displacement, is the most significant prognostic factor for premature physeal closure.

Question 62

On an anteroposterior pelvis radiograph of a 6-month-old female, the ossific nucleus of the right femoral head is located in the superolateral quadrant formed by Hilgenreiner's and Perkin's lines. What is the diagnosis?

Explanation

In a normal pediatric pelvis radiograph, the ossific nucleus of the femoral head sits in the inferomedial quadrant. A superolateral position relative to Hilgenreiner's and Perkin's lines is diagnostic of developmental dysplasia of the hip (DDH).

Question 63

You are evaluating a 14-month-old boy with infantile idiopathic scoliosis. Which of the following radiographic parameters most reliably predicts the likelihood of curve progression?

Explanation

Mehta's rib-vertebra angle difference (RVAD) is the most critical prognostic indicator for infantile idiopathic scoliosis. An RVAD greater than 20 degrees strongly predicts curve progression, whereas an RVAD less than 20 degrees suggests likely spontaneous resolution.

Question 64

A 9-year-old girl develops a localized physeal bar in the distal radius following a previous trauma. Advanced imaging shows the bar comprises 25% of the cross-sectional area of the physis, and she has roughly 3 cm of anticipated growth remaining. What is the most appropriate management?

Explanation

Physeal bar resection with interposition (e.g., fat or cranioplast) is indicated if the bar involves less than 50% of the cross-sectional area and the child has at least 2 years or 2 cm of remaining growth. If greater than 50% is involved, completion epiphysiodesis is preferred.

Question 65

A newborn with arthrogryposis multiplex congenita presents with rigid, bilateral dislocated hips. What is the generally recommended initial management for these hip dislocations?

Explanation

Teratologic hip dislocations, such as those seen in arthrogryposis, are notoriously rigid. Pavlik harnesses are contraindicated as they frequently fail and can cause iatrogenic fractures or cartilage damage. Observation until roughly 6 months of age followed by single-stage open reduction is standard.

Question 66

A 3-year-old girl is diagnosed with congenital scoliosis secondary to a fully segmented hemivertebra in the lower thoracic spine. Which of the following diagnostic screening studies is most critical during her initial systemic evaluation?

Explanation

Congenital scoliosis is strongly associated with genitourinary anomalies (up to 30% of patients), most commonly a unilateral absent kidney. A renal ultrasound and total spine MRI are critical components of the initial diagnostic workup.

Question 67

A 13-year-old boy sustains a juvenile Tillaux fracture. This fracture pattern is primarily the result of the specific sequence of closure of the distal tibial physis. In what predictable sequence does the distal tibial physis normally close?

Explanation

The distal tibial physis typically closes from central to anteromedial, then posteromedial, and finally lateral. This late closure of the lateral portion leaves it vulnerable to avulsion by the anterior inferior tibiofibular ligament, resulting in a Tillaux fracture.

Question 68

A 4-year-old girl is undergoing surgical treatment for late-presenting developmental dysplasia of the hip. The surgeon plans a redirectional pelvic osteotomy that hinges at the symphysis pubis to provide primarily anterolateral coverage. Which osteotomy is being described?

Explanation

The Salter innominate osteotomy is a complete, trans-iliac redirectional osteotomy that hinges on the symphysis pubis to provide anterolateral head coverage. The Pemberton and Dega osteotomies are incomplete osteotomies that hinge at the triradiate cartilage.

Question 69

A 12-year-old premenarchal girl (Risser 0) is diagnosed with Adolescent Idiopathic Scoliosis. Her standing radiographs reveal a right thoracic curve of 32 degrees. Neurologic exam is normal. What is the most appropriate management?

Explanation

In a growing child (Risser 0-2) with an adolescent idiopathic scoliosis curve measuring between 25 and 45 degrees, TLSO bracing is indicated to halt curve progression. A landmark trial (BrAIST) showed bracing significantly decreases the likelihood of progression to surgery.

Question 70

A 14-year-old boy sustains a triplane fracture of the distal ankle. Which of the following Salter-Harris fracture patterns best describes the radiographic appearance in the sagittal and coronal planes, respectively?

Explanation

A triplane fracture typically appears as a Salter-Harris III fracture (vertical epiphyseal separation) on an AP (coronal) radiograph, and a Salter-Harris II fracture (posterior metaphyseal spike) on a lateral (sagittal) radiograph.

Question 71

You are evaluating a 6-week-old infant who has been in a Pavlik harness for 2 weeks for DDH. The parents report the infant has stopped kicking the left leg. On examination, the infant demonstrates absent active knee extension on the left side. What is the most likely diagnosis and appropriate initial management?

Explanation

Absent active knee extension in a Pavlik harness indicates a femoral nerve palsy, which is typically caused by excessive hip flexion compressing the nerve against the pelvis. The standard management is to temporarily discontinue the harness until quadriceps function fully recovers.

Question 72

A 6-week-old female infant, born breech, undergoes a screening ultrasound of the hips. The alpha angle is measured at 48 degrees and the beta angle at 65 degrees. Dynamic stress views show subluxation. What is the most appropriate initial management?

Explanation

An alpha angle less than 60 degrees at 6 weeks with instability indicates Developmental Dysplasia of the Hip (DDH). A Pavlik harness is the gold standard first-line treatment for reducible DDH in infants under 6 months of age.

Question 73

A 6-year-old boy presents with a 35-degree right thoracic curve. An MRI of the entire spine is unremarkable. Which of the following is the most appropriate management for this patient?

Explanation

This patient has Juvenile Idiopathic Scoliosis (JIS) with a moderate curve (25-50 degrees) and significant growth remaining. Full-time bracing is the standard of care to halt progression, while surgery is reserved for curves progressing beyond 50 degrees.

Question 74

A 13-year-old boy presents with an ankle injury after a twisting mechanism while playing soccer. CT imaging reveals a fracture with a sagittal component through the epiphysis, a coronal component through the posterior metaphysis, and a transverse component through the physis. Which mechanism of injury is most classically associated with this fracture pattern?

Explanation

This describes a triplane fracture, which is a Salter-Harris IV equivalent. It is classically caused by a supination-external rotation force in a child nearing skeletal maturity.

Question 75

A 30-month-old girl presents with a painless limp. Examination reveals a positive Galeazzi sign and limited abduction of the left hip. Radiographs demonstrate a high dislocation of the left hip with a false acetabulum. She has had no prior treatment. What is the most appropriate definitive management?

Explanation

In a child older than 2 years with a high untreated hip dislocation, soft tissue contractures make closed reduction unsafe and unlikely to succeed. Open reduction with a femoral shortening osteotomy is typically required to reduce joint pressure and minimize the risk of avascular necrosis.

Question 76

Parents of a newborn diagnosed with congenital scoliosis are seeking counseling regarding the risk of curve progression. Which of the following vertebral anomalies carries the highest risk of rapid progression?

Explanation

A fully segmented hemivertebra combined with a contralateral unsegmented bar creates a severe growth tether on one side and active growth on the other. This anomaly has the highest risk of rapid curve progression, often requiring early prophylactic fusion.

Question 77

A 14-year-old girl sustains a juvenile Tillaux fracture (Salter-Harris III of the anterolateral distal tibial epiphysis). What underlying anatomic phenomenon explains why the fracture occurs specifically in this anterolateral location?

Explanation

The distal tibial physis closes in an asymmetric pattern: it starts centrally, progresses medially, and finally closes laterally. The open anterolateral physis remains vulnerable to avulsion forces from the anterior inferior tibiofibular ligament.

Question 78

A 14-year-old girl is diagnosed with a 45-degree right thoracic scoliosis. She is premenarcheal, Risser 0, and has open triradiate cartilages on pelvic radiographs. Without treatment, what is the estimated risk of her curve progressing to greater than 50 degrees?

Explanation

Curve progression risk is based on remaining growth and curve magnitude. A premenarcheal, Risser 0 patient with a curve already at 45 degrees has an extremely high risk (approaching 100%) of progressing beyond surgical thresholds.

Question 79

A 3-month-old infant is being treated for DDH with a Pavlik harness. During a follow-up visit, you notice the infant lacks active knee extension on the treated side, though the harness is holding the hips in 110 degrees of flexion. What is the most likely cause of this finding?

Explanation

Excessive hip flexion in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a temporary femoral nerve palsy (manifesting as decreased active knee extension). This requires immediate adjustment or temporary removal of the harness.

Question 80

A 10-year-old boy falls from monkey bars and sustains a distal radius fracture. Radiographs demonstrate a fracture line that passes through the metaphysis, traverses the physis, and exits through the epiphysis into the radiocarpal joint. What Salter-Harris classification does this represent?

Explanation

A Salter-Harris Type IV fracture involves the metaphysis, physis, and epiphysis. Because it crosses the articular surface and the growth plate vertically, precise anatomic reduction is critical to prevent physeal arrest and joint incongruity.

Question 81

A 15-year-old girl undergoes a posterior spinal fusion for adolescent idiopathic scoliosis. On postoperative day 4, she develops significant abdominal distension, bilious emesis, and marked weight loss. Which anatomic structure is most likely directly compressing the obstructed bowel segment?

Explanation

This presentation is classic for Superior Mesenteric Artery (SMA) syndrome, a known complication of scoliosis surgery. Lengthening of the spine narrows the aortomesenteric angle, causing the SMA to compress the third portion of the duodenum.

Question 82

According to the American Academy of Pediatrics (AAP) guidelines, routine ultrasound screening for DDH at 6 weeks of age is universally recommended for which of the following asymptomatic infants?

Explanation

The AAP recommends targeted ultrasound screening at 6 weeks of age for infants with specific risk factors. Breech presentation (especially in females) and a positive family history are the strongest risk factors warranting routine screening.

Question 83

A 7-year-old boy sustained a Salter-Harris IV fracture of the distal femur 2 years ago. He now presents with a 3 cm leg length discrepancy and a progressive valgus deformity. CT mapping reveals a central physeal bar occupying 40% of the cross-sectional area of the physis. What is the best treatment option?

Explanation

Physeal bar resection with interposition grafting (e.g., fat or Cranioplast) is indicated when the bar occupies less than 50% of the physeal cross-section and the child has more than 2 years of remaining growth.

Question 84

A 12-year-old boy with Duchenne muscular dystrophy presents with a progressive 45-degree thoracolumbar scoliosis. His Forced Vital Capacity (FVC) is currently 40% of predicted. What is the most appropriate management plan?

Explanation

In Duchenne muscular dystrophy, scoliosis progresses relentlessly, and bracing is poorly tolerated and ineffective. Posterior spinal fusion to the pelvis is recommended when curves reach 20-30 degrees, ideally while the FVC is still >30-35%, to minimize perioperative pulmonary complications.

Question 85

A 5-month-old infant has been treated in a Pavlik harness for 4 weeks for a completely dislocated right hip. A repeat ultrasound shows the hip remains persistently dislocated. What is the most appropriate next step in management?

Explanation

Failure to achieve reduction in a Pavlik harness after 3 to 4 weeks is an indication to abandon the harness to prevent 'Pavlik harness disease' (posterior acetabular wear). The next step is a closed reduction under anesthesia, typically with an arthrogram, followed by spica casting.

Question 86

A 6-month-old boy is diagnosed with infantile idiopathic scoliosis. He has a 35-degree left thoracic curve. Radiographs demonstrate a rib-vertebral angle difference (RVAD, or Mehta's angle) of 25 degrees. What is the most appropriate management?

Explanation

An RVAD greater than 20 degrees in infantile idiopathic scoliosis is a strong predictor of curve progression. Early intervention with serial derotational casting (Mehta casting) has been shown to successfully halt progression and potentially cure the deformity.

Question 87

Which of the following pediatric lower extremity physeal fractures carries the highest historical rate of premature growth arrest?

Explanation

Distal femoral physeal fractures, even Salter-Harris II patterns, carry a notoriously high risk of premature growth arrest (often cited between 30% and 50%). This is due to the severe energy required to fracture the undulating contour of the distal femoral physis.

Question 88

A 6-week-old female infant presents with a positive Ortolani sign on the left hip. Ultrasound shows an alpha angle of 45 degrees. What is the most appropriate next step in management?

Explanation

The patient presents with clinical DDH and an abnormal ultrasound alpha angle (normal is >60 degrees). The Pavlik harness is the gold standard for reducible hip dysplasia in infants under 6 months of age.

Question 89

A 2-year-old girl is undergoing closed reduction and spica casting for late-presenting developmental dysplasia of the hip. Which of the following intraoperative positioning parameters represents the highest risk for developing avascular necrosis of the femoral head?

Explanation

Hip abduction greater than 60 degrees in a spica cast significantly increases the risk of avascular necrosis (AVN) of the femoral head. Safe zone positioning emphasizes moderate flexion and avoiding excessive abduction.

Question 90

In evaluating a 12-year-old girl with adolescent idiopathic scoliosis, which of the following combinations of factors indicates the highest risk for curve progression?

Explanation

Peak height velocity occurs just prior to menarche, making premenarchal status a critical risk factor for progression. A 30-degree curve in a rapidly growing premenarchal girl has the highest risk of progression among the choices provided.

Question 91

A newborn is diagnosed with congenital scoliosis secondary to a fully segmented hemivertebra. Which of the following imaging studies is most critical to obtain during the initial comprehensive evaluation?

Explanation

Congenital scoliosis is highly associated with VACTERL anomalies, occurring in up to 60% of cases. Evaluating for concurrent genitourinary and cardiac anomalies using renal ultrasound and an echocardiogram is essential during the initial workup.

Question 92

A 10-year-old boy sustains a Salter-Harris type II fracture of the distal femur. Despite anatomic closed reduction and casting, the patient is at significant risk for which of the following long-term complications?

Explanation

Distal femoral physeal fractures, especially Salter-Harris II, have a notoriously high rate of premature physeal closure and growth arrest. This complication occurs in up to 50% of cases due to the highly undulating anatomy of the distal femoral physis.

Question 93

A 12-year-old boy developed a distal tibial physeal bar following a previous fracture. A scanogram reveals a 2 cm leg length discrepancy and 15 degrees of varus angulation. Mapping shows the bar involves 20% of the cross-sectional area of the physis peripherally. What is the most appropriate treatment?

Explanation

Physeal bar resection is indicated if the bar involves less than 50% of the physis and the patient has more than 2 years of growth remaining. The presence of an associated angular deformity requires a concurrent corrective osteotomy.

Question 94

A 4-month-old girl with left developmental dysplasia of the hip has been treated in a Pavlik harness for 4 weeks. Repeat ultrasound shows failure of reduction with the femoral head remaining chronically dislocated. What is the most appropriate next step in management?

Explanation

If a dislocated hip is not reduced after 3 to 4 weeks of Pavlik harness use, it should be discontinued to prevent "Pavlik disease" (excoriation of the posterior acetabulum). The next appropriate step is transition to a rigid orthosis or closed reduction and spica casting.

Question 95

A 6-month-old boy is noted to have a 25-degree left thoracic curve. Radiographs indicate a rib-vertebral angle difference (RVAD) of Mehta of 25 degrees. What is the most appropriate management?

Explanation

Infantile idiopathic scoliosis with a rib-vertebral angle difference (RVAD) of Mehta greater than 20 degrees has a high likelihood of malignant progression. Serial Mehta casting is the appropriate treatment to control and potentially cure the progressive curve.

Question 96

A 14-year-old boy sustains an ankle injury resulting in a Salter-Harris III fracture of the anterolateral distal tibia. Which of the following best describes the pathomechanics of this specific fracture pattern?

Explanation

A juvenile Tillaux fracture is a Salter-Harris III fracture of the anterolateral distal tibia. It occurs due to avulsion by the anterior inferior tibiofibular ligament during external rotation, as the medial physis closes before the lateral physis.

AAOS Orthopedic MCQs (Set 1): Spine Disorders, Sports Medicine & Arthroplasty | 2026 Board Review

AAOS Pediatric Orthopedics (Set 1): DDH, Scoliosis & Growth Plate Injuries | 2024 Board Review

Key Takeaway

AAOS Pediatric Orthopedics (Set 1): DDH, Scoliosis & Growth Plate Injuries | 2024 Board Review

Chapter Index