• Congenital and developmental anomalies with terminal limb deficiencies (see Plate 3-32): hemihypertrophy or hemiatrophy, Klippel-Trénaunay-Weber syndrome, Maffucci syndrome, posterior bowing of the tibia, proximal femoral focal deficiency, congenital short femur, enchondromatosis
• Paralytic disorders: poliomyelitis, encephalopathy (e.g., cerebral palsy), myelopathy (e.g., myelomeningocele)
• Infections of bone and joint that retard or arrest bone growth: osteomyelitis (may accelerate or inhibit growth), septic arthritis (may lead to avascular necrosis with partial or complete growth arrest)
• Trauma to bone and joint: injuries to the growth plate (may arrest growth); fractures of the metaphysis or diaphysis (may accelerate growth); malunion, excessive overriding, or angulation due to fracture (may result in limb shortening)
• Tumorous conditions that produce bone overgrowth: fibrous dysplasia, enchondromatosis, osteoid osteoma, hemangioma, neurofibromatosis
• Tumors that produce growth retardation: solitary enchondroma of growth plate, simple bone cyst with repeated fractures through growth plate
• Irradiation of malignant tumors of long bones that arrest growth: Ewing sarcoma, neuroblastoma
The many factors to be considered in the treatment of leg-length discrepancy include (1) etiology; (2) degree of the discrepancy; (3) skeletal age; (4) progression of the discrepancy; (5) predicted adult height and predicted magnitude of the leg-length discrepancy at skeletal maturity; (6) strength and balance of the musculature of the limb, especially in neurologic disorders; (7) status of the foot and ankle (e.g., availability of muscles in the foot and ankle, presence of an equinus contracture of the short limb that allows the child to walk on tiptoe on the short side to balance the pelvis); (8) predominant site of the inequality (i.e., femur or tibia); (9) any general or extenuating health factors; and (10) the needs and desires of the patient and parents.
Leg-length discrepancy can be measured in several ways. A common method is to place standing blocks of measured thickness beneath the short leg to level the pelvis. Radiographic techniques, using a metal ruler on the film, include a one-exposure technique in which a single exposure is made of both entire lower limbs. The one-exposure technique may produce magnification at the ends of the lower limbs owing to the effect of parallax. A more accurate method involves three successive exposures of the hips, knees, and ankles on one long film (see Plate 4-33). Unfortunately, none of the radiographic measurement techniques accurately depicts pelvic asymmetry, differences in pelvic height, or height of the feet; therefore, it is always important to correlate the radiographic measurements with the clinical examination of pelvic obliquity.
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