Muscular strength in idiopathic haemihypertrophy.

Nine patients (age 8.9, range 6.5 to 9.5 years) with idiopathic haemihypertrophy were followed at six month intervals for two years. The isometric voluntary contraction strength of the elbow flexors and knee extensors was measured bilaterally, and expressed per unit of muscle and bone cross sectional area of the upper arm (elbow flexors) and of the mid thigh (knee extensors). In absolute terms, the hypertrophic side was always stronger, and the increase in strength was strongly correlated with the increase in limb size bilaterally (P less than 0.01). The hypertrophic limb always exerted greater isometric strength, but if strength was standardized for an anthropometric estimate of upper arm and mid thigh cross sectional area, the normal and hypertrophic side were not significantly different. The limb length discrepancy, when expressed in percentage, remained constant at approximately 3%.