Leg muscle atrophy in idiopathic congenital clubfoot: is it primitive or acquired?

PURPOSE To investigate whether atrophy of the leg muscles present in congenital clubfoot (CCF) is primitive or secondary to treatment of the deformity. METHODS Magnetic resonance imaging (MRI) of both legs was taken in three cohorts of patients with unilateral congenital clubfoot (UCCF): eight untreated newborns (age range 10 days to 2 weeks); eight children who had been treated with the Ponseti method (age range 2-4 years); eight adults whose deformity had been corrected by manipulation and casting according to Ponseti, followed by a limited posterior release performed at age 2-3 months (age range 19-23 years). All of the treated patients wore a brace until 3 years of age. Muscles were measured on transverse MRI scans of both legs taken midway between the articular surface of the knee and the articular surface of the ankle, using a computer program (AutoCAD 2002 LT). The same program was used to measure leg muscles in the histologic cross sections of the legs of two fetuses with UCCF, spontaneously aborted at 13 and 19 weeks of gestation, respectively. Measurements of the whole cross section of the leg (total leg volume: TLV), of the muscular tissue (muscular tissue volume: MTV), and of the adipose tissue (adipose tissue volume: ATV) of the tibia, fibula, and of the other soft tissues (tendons, nerves, and vessels) were taken by using an interactive image analyzer (IAS 2000, Delta System, Milan, Italy). RESULTS Marked atrophy of the leg muscles on the clubfoot side was found in both fetuses and untreated newborns, with a percentage ratio of MTV between the normal and the affected leg of 1.3 and 1.5, respectively. Leg muscle atrophy increased with growth, and the percentage ratio of MTV between the normal and the affected leg was, respectively, 1.8 and 2 in treated children and adults. On the other hand, fatty tissue tended to increase relatively from birth to adulthood, but it could not compensate for the progressive muscular atrophy. As a result, the difference in TLV tended to increase from childhood to adulthood. CONCLUSIONS Our study shows that leg muscular atrophy is a primitive pathological component of CCF which is already present in the early stages of fetal CCF development and in newborns before starting treatment. Muscular atrophy increases with the patient's age, suggesting a mechanism of muscle growth impairment as a possible pathogenic factor of CCF.