4. Pediatrics MCQs

This relies on Paley's Deformity Rule 2: When the ACA passes through the CORA, but the osteotomy is at a different level, the correction will result in angulation and translation at the osteotomy site, but the proximal and distal mechanical axes will become collinear and the overall alignment is properly restored.

Physeal bar resection and interposition (e.g., with fat or cranioplast) is indicated to restore longitudinal growth and correct angular deformity. Generally accepted contraindications include when the physeal bar involves greater than 50% of the cross-sectional area of the physis, or when the patient has less than 2 years of remaining skeletal growth, as the procedure will not yield clinically meaningful correction in these cases.

The metaphyseal-diaphyseal angle, also known as the Drennan angle, is measured on an AP radiograph of the tibia. An angle greater than 16 degrees is highly predictive of progressive infantile Blount's disease. Angles less than 10 degrees are typical of physiologic bowing and tend to resolve spontaneously.

Fibular hemimelia is frequently associated with several other anomalies, including shortening of the femur, ball-and-socket ankle joint, tarsal coalitions, and absence of the lateral rays of the foot. In the knee, the most common intra-articular anomaly is hypoplasia or complete absence of the anterior cruciate ligament (ACL).

The Menelaus method estimates growth from the distal femur at approximately 10 mm (3/8 inch) per year and from the proximal tibia at 6 mm (1/4 inch) per year until growth ceases (typically at age 14 for girls).

To maximize frame rigidity and minimize micromotion and wire breakage in ring fixators, wires should ideally cross at or near 90 degrees (maximizing the crossing angle) and be tensioned to approximately 130 kg in the adult tibia.

DISCUSSIONThe hip arthritis RR is significantly increased in patients with DDH (RR = 82.4; P < 2e-16), their parents (RR = 2.22; P = 0.0003), and their grandparents (RR = 1.33; P = 0.011). The THA RR also is significantly increased for patients with DDH (RR = 1168; P < 3e-08) and their grandparents (RR = 2.06; P = 0.01). First-degree and second-degree relatives were not at higher risk for knee arthritis or knee arthroplasty. The RR for DDH was significantly increased for first-degree relatives (RR = 12.1; P < 0.000001) and siblings (RR = 11.9; P < 0.000001).

DISCUSSION: For children between the ages of 1 and 6 years, closed reduction and early spica casting is recommended. In some instances, associated injuries or body habitus may preclude cast treatment. Pavlik harness treatment of femoral fractures is for infants younger than 1 year of age. Rarely is there an indication for traction. Internal fixation is reserved in general for children older than age 6 years or with confounding factors. REFERENCES: Abel MF (ed): Orthopaedic Knowledge Update: Pediatrics 3. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2006, pp 271-280. Flynn JM, Schwend RM: Management of pediatric femoral shaft fractures. J Am Acad Orthop Surg 2004;12:347-359.

For the parachute test, the examiner holds the child prone and then lowers the child rapidly toward the floor. The parachute reaction is normal or positive if the child reaches toward the floor. The Moro or startle reflex should not be present beyond age 6 months. Asymmetric tonic neck reflex, extensor thrust, and absent foot placement are abnormal findings at any age.

DISCUSSION: Fractures of the long bones are common in patients with myelodysplasia, and the frequency of fracture increases with higher level defects. Fractures also occur following surgery and immobilization secondary to disuse osteoporosis. The response to the fracture (swelling, fever, warmth, erythema) is often confused with infection, osteomyelitis, or cellulitis. Management should consist of a short period of immobilization in a well-padded splint. Long-term casting results in further osteopenia and repeated fractures. REFERENCES: Lock TR, Aronson DD: Fractures in patients who have myelomeningocele. J Bone Joint Surg Am 1989;71:1153-1157. Kumar SJ, Cowell HR, Townsend P: Physeal, metaphyseal, and diaphyseal injuries of the lower extremities in children with myelomeningocele. J Pediatr Orthop 1984;4:25-27.

DISCUSSION: The most effective way to measure a limb-length discrepancy in a patient with a knee flexion contracture is a lateral CT scanogram. All the other methods listed provide inaccurate results with a knee flexion contracture because the measurements are made in the coronal plane. REFERENCES: Aaron A, Weinstein D, Thickman D, et al: Comparison of orthoroentgenography and computed tomography in the measurement of limb-length discrepancy. J Bone Joint Surg Am 1992;74:897-902. Tachdjian MO: Clinical Pediatric Orthopaedics: The Art of Diagnosis and Principles of Management. Stamford, CT, Appleton and Lange, 1997, pp 237-240.

Clubfoot (talipes equinovarus) in patients with arthrogryposis is a rigid and resistant deformity. However, multiple studies document limited success with nonsurgical management. Manipulation and casting are generally a preliminary treatment before surgery; successful correction will most likely require a talectomy.

DISCUSSION: The child has a trigger thumb deformity. A trigger thumb is a developmental mechanical problem rather than a congenital deformity. The anomaly generally is not noted at birth. A fixed flexion deformity of the IP joint of the thumb most commonly occurs in children in the first 2 years of life. A stretching and splinting program may correct the deformity in the first year of life, but nonsurgical management after age 3 years results in a success rate of only 50%. Release of the proximal annular pulley of the flexor sheath is recommended at this age. REFERENCES: Tan AH, Lam KS, Lee EH: The treatment outcome of trigger thumb in children. J Pediatric Orthop B 2002;11:256-259. Slakey JB, Hennrikus WL: Acquired thumb flexion contracture in children: Congenital trigger thumb. J Bone Joint Surg Br 1996;78:481-483. Herring JA: Disorders of the upper extremity: Thumb dysplasia, in Herring JA (ed): Tachdjian’s Pediatric Orthopaedics, ed 3. Philadelphia, PA, WB Saunders, 2002, p 445.

DISCUSSION: While other surgical and nonsurgical options exist for management of spasticity, the criteria originally laid out by Peacock and associates describe the most appropriate candidate for rhizotomy as a patient with spastic diplegia who is between the ages of 4 to 8 years and has a stable gait pattern that is limited by lower extremity spasticity. Rhizotomy is not recommended in patients with athetosis because of unpredictable results. In addition, rhizotomy should be avoided in nonambulatory patients with spastic quadriplegia because it is associated with significant spinal deformities. REFERENCES: Peacock WJ, Arens LJ, Berman B: Cerebral palsy spasticity: Selective posterior rhizotomy. Pediatr Neurosci 1987;13:61-66. Oppenheim WL: Selective posterior rhizotomy for spastic cerebral palsy: A review. Clin Orthop 1990;253:20-29. Mooney JF III, Millis MB: Spinal deformity after selective dorsal rhizotomy in patients with cerebral palsy. Clin Orthop 1999;364:48-52.

DISCUSSION: Hypophosphatemia is a rare genetic disease usually inherited as an X-linked dominant trait. The fact that the woman has no skeletal manifestations would indicate that the husband has the X-linked mutation. The disease is more severe in boys than it is in girls. The husband will not transmit the disease to his sons. However, all of their daughters will be affected either with the disease or as carriers. If the woman has the disease or the trait, there is a 50% chance that her sons will inherit the disease and a 50% chance that her daughters will be carriers or have a milder form of the disease. Parents should be advised to have genetic counseling so they can be informed when deciding whether to have children. REFERENCES: Herring JA: Metabolic and endocrine bone diseases, in Tachdjian’s Pediatric Orthopaedics, ed 3. New York, NY, WB Saunders, 2002, pp 1685-1743. Sillence DO: Disorders of bone density, volume, and mineralization, in Rimoin DL, Conner JM, Pyerite RE, et al (eds): Principles and Practice of Medical Genetics, ed 4. New York, NY, Churchill Livingstone, 2002. Staheli LT: Practice of Pediatric Orthopedics. Philadelphia, PA, Lippincott Williams & Wilkins, 2001.

DISCUSSION: Children with hypothyroidism have delayed bone age, reduced thickness of the physis, disorganization of the cartilage columns of the physis, and impaired differentiation of proliferating chondrocytes into hypertrophic cells. As a result, these children have severe growth retardation, and slipped capital femoral epiphysis may develop because of mechanical weakening of the physis. Thyroid hormone regulates terminal differentiation of the growth plate chondrocytes, with a resultant increase in type X collagen and alkaline phosphatase. These substances are important factors in matrix mineralization. Insulin-like growth factors and FGF-2 appear to act synergistically to stimulate mitotic activity of the growth plate chondrocytes. TGF-beta and PTHrP stimulate proteoglycan synthesis and mitotic activity of the chondrocytes and inhibit type X collagen and alkaline phosphatase activity. REFERENCES: Ballock RT: Regulation of skeletal growth and maturation by thyroid hormone, in Buckwalter JA, Ehrlich MG, Sandell LJ, Trippel SB (eds): Skeletal Growth and Development: Clinical Issues and Basic Science Advances. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1998, pp 301-317. Rosier RN, O’Keefe RJ, Reynolds PR, Hicks DG, Puzas JE: Expression and function of TGF-beta and PTHrP in the growth plate, in Buckwalter JA, Ehrlich MG, Sandell LJ, Trippel SB (eds): Skeletal Growth and Development: Clinical Issues and Basic Science Advances. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1998, pp 285-299. Trippel SB: IGF-I and FGF-2 in growth plate regulation, in Buckwalter JA, Ehrlich MG, Sandell LJ, Trippel SB (eds): Skeletal Growth and Development: Clinical Issues and Basic Science Advances. Rosemont, Ill, American Academy of Orthopaedic Surgeons, 1998, pp 263-283.

The radiograph reveals a complete hip dislocation. A Pavlik harness is an accepted method of treatment for a dislocated hip up until 6 months of age. Closed reduction and spica casting with an arthrogram is often successful in young children up to 1-1/2 years to 2 years of age. Open reduction, capsulorrhaphy, and a spica cast is commonly recommended for younger children when attempts at closed reduction have failed or when the child is older than 2 years of age. A femoral shortening is also generally recommended in children older than 2 years of age in an attempt to reduce the muscle/compressive forces on the reduced hip.(SBQ13PE.38) Pavlik harness treatment is appropriate for which of the following?:Review Topic4 year old with a diaphyseal femur fracture and a neuromuscular disorder with lower extremity spasticity2 month old with a displaced spiral mid-diaphyseal femur fracture9 month old with a diaphyseal femur fracture with <2cm shortening9 month old with a diaphyseal femur fracture with >2cm shortening4 year old with a diaphyseal femur fracture, closed head injury and chest traumaTreatment with Pavlik harness or spica cast are options for patients <6 months of age with diaphyseal femur fractures. Pavlik harness provides adequate pain control for the short time required for healing in this age group. Significant remodeling potential can be expected.Because of the significant remodeling and quick healing, treatment of diaphyseal femur fractures in children younger than 6 months focuses on providing comfort and avoiding complications. Spica casting likewise results in stable union without longterm sequelae but minor skin complications are more common and some favor Pavlik treatment in this age group.Kocher et al. provide the AAOS Clinical Practice Guideline for the treatment of pediatric diaphyseal femur fractures. Their recommendation for diaphyseal femur fractures in children less than 6 months is Grade C, based on Level IV evidence (one retrospective comparative study and one case series). They recommend that Pavlik and spica casting are both acceptable treatment options in this age group.Flynn et al. review the management of pediatric femoral shaft fractures. They recommend Pavlik treatment for children 6 months of age or less in preference to a spica cast, sometimes supplemented with a simple splint. This avoids the skin complications of spica casting.Incorrect answers:

DISCUSSION: Weinstein reported on 31 patients (45 feet) with congenital metatarsus adductus followed for an average of 33 years. Twenty-nine feet had moderate to severe deformities treated with manipulation and casting with a 90% success rate. In a young child, surgery is not indicated until nonsurgical management has failed. In patients 2 to 4 years of age, tarsometatarsal capsulotomies are indicated, whereas multiple metatarsal osteotomies are reserved for recalcitrant deformities in children older than 4 years of age. Mild or moderate metatarsus adductus that is passively correctable will resolve without treatment. REFERENCES: Beaty J: Congenital anomalies of the lower extremity, in Canale ST (ed): Campbell’s Operative Orthopaedics, ed 10. Philadelphia PA, Mosby, 2003, pp 983-988. Katz K, David R, Soudry M: Below-knee plaster cast for the treatment of metatarsus adductus. J Pediatr Orthop 1999;19:49-50. Weinstein SL: Bristol-Myers Squibb/Zimmer award for distinguished achievement in orthopaedic research. Long-term follow-up of pediatric orthopaedic conditions: Natural history and outcomes of treatment. J Bone Joint Surg Am 2000;82:980-990.

This is one of those OITE questions that there is no way to make an educated guess. You either knew this or simply picked the best sounding answer. Wolff’s Law, which we are all familiar with, states that the bone builds structural development most suited for the stresses applied. I could not find Hooke’s and Hilston’s Laws in any orthopaedic or medical text and therefore, believe these were simply “fillers” to make five selections. Muller-Haeckel Law is from the Biogenetics principal that living matter always arises from pre-existing living matter (very profound). Finally, the Heuter-Volkmann Law is one that applies to many mechanisms in orthopaedics, but this question is specifically regarding tibia vara. This law states that increased pressure/strain across the epiphyseal plate on the medial aspect of the knee will inhibit its longitudinal growth. Conversely, Depelch’s Law not mentioned in the question, but certain to show up in future OITE’s states that distraction at the level of the physeal plate will cause increases longitudinal growth.

DISCUSSION: The radiograph shows the typical findings of achondroplasia. The defect is in fibroblast growth factor receptor 3. The pedicles narrow distally in the lumbar spine. The pelvis is low and broad with narrow sciatic notches and ping-pong paddle-shaped iliac wings. This is often called a champagne glass pelvis. Type I collagen abnormalities are typically found in osteogenesis imperfecta, and type II collagen defects are found in spondyloepiphyseal dysplasia and Kniest syndrome. COMP is defective in multiple epiphyseal dysplasia. Sulfate transport defects are seen in diastrophic dysplasia. REFERENCES: Johnson TR, Steinbach LS: Essentials of Musculoskeletal Imaging. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2004, pp 809-812. Caffey J: Achondroplasia of the pelvis and lumbosacral spine: Some roentgenographic features. Am J Roentgenol 1958;80:449.