Orthopaedic manifestations of congenital myotonic dystrophy during childhood and adolescence.

BACKGROUND

Congenital myotonic dystrophy (CMD) is a dominantly inherited disorder manifested in childhood by muscle weakness which can be profound at birth, but which progressively improves over the first few years. Congenital myotonic dystrophy represents the severe end of the spectrum of myotonic dystrophy, which in milder cases may not be diagnosed until adulthood. The goal of the study was to identify and quantitate the musculoskeletal deformities which may significantly affect the function of children with CMD.

METHODS

A retrospective chart and radiograph review was performed after Institutional Review Board approval for all cases of myotonic dystrophy from 1987 to 2004 followed at a children's specialty orthopaedic hospital. Inclusion criteria were either a conclusive testing for CMD by gene testing, electromyography, and/or muscle biopsy in the child or parent and the presence of a typical clinical picture. Skeletal manifestations were classified by body segment (upper extremity, hand, spine, hip, lower extremity, foot) and by the type of deformity. Surgical procedures and outcomes were also documented.

RESULTS

Thirty children and adolescents met the inclusion criteria. The male/female ratio was 1 (15 boys and 15 girls). In 27 cases, the mother transmitted the disease, and in 2 cases, the father transmitted the disease; in one case, it was impossible to reconstitute the family history of the child who was adopted. The mean age at onset of gait was 29 months. Twenty-two (73%) out of 30 children underwent surgery for lower extremity-, foot-, or spinal-related deformities. The mean follow-up was 11.4 years (range, 3-20 years).No contractures or deformities were observed in the upper extremities. Spinal deformities affected 9 patients (30%), and 3 of these required surgery. These spinal deformities when present usually had an early onset and included thoracolumbar scoliosis as well as kyphoscoliosis. Problems at the level of the hips and knee were infrequent and included only 2 patients who had unilateral hip abduction contracture and 1 patient who had significant fixed knee flexion contracture. Congenital clubfoot occurred in 5 patients (17%) and generally responded well after posteromedial release and recurrence occurred in only one case. Developmental equinus and equinovarus exclusive of clubfoot affected 7 patients (23%), 70% of whom required surgery. Outcome after Achilles tendon lengthening was positive, and many of the children began walking soon after the Achilles lengthening, and recurrence did not occur.

CONCLUSIONS

Child with CMD are at high risk for musculoskeletal deformities of the spine and lower extremities. In our experience, correction and improved function were likely after surgery.

LEVEL OF EVIDENCE

Retrospective study; level IV.