We retrospectively reviewed eight children with idiopathic chondrolysis (IC) of the hip and nine with atrophic tuberculosis (TB) of the hip treated over the 10 years 1990 to 1999. Both conditions present with a stiff hip and radiographic joint space narrowing. Our aim was to delineate clinical, radiological and histological differences between the two conditions, thereby obviating the need for biopsy in IC, which could worsen the prognosis.

In the IC group all patients were girls. Their mean age was 12 years (11.5 to 13). They presented with a flexion abduction and external rotation deformity of the hip. Chest radiographs were normal in all patients, and all except one had an ESR below 20. The Mantoux was negative in six of the eight. Radiographs showed joint space narrowing and osteopoenia, but the subchondral bony line remained present. Four of the eight had a synovial biopsy, which showed non-specific chronic synovitis. The cartilage looked pale and lustreless. In one hip the cartilage was biopsied and showed cartilage necrosis.

In the TB group, five of the nine patients were boys. The mean age was 7 years (5 to 13.5). The only constant hip deformity was flexion. Chest radiographs were normal in all patients. In all patients the ESR was below 20 and the Mantoux was positive. Hip radiographs showed osteopoenia with loss of the subchondral bony line. Peri-articular lytic lesions were present in all patients except one. Histology of synovial biopsy showed caseous necrosis in all hips, and seven of the nine had a positive culture for TB. Macroscopically the cartilage looked normal, and in one hip the cartilage biopsy was histologically normal.

We confirmed that in IC the joint space narrowing is due to cartilage necrosis. We postulate that in atrophic TB the loss of subchondral bone due to subchondral erosion gives the impression of joint space narrowing. We also concluded that IC was a diagnoses per se and not by exclusion, and that biopsy was not required.

We reviewed 55 patients with mid-lumbar myelomeningocele (L3 and L4) first seen over a 17-year period from 1970 to 1986 and followed up for an average of ten years. We assessed a number of factors which might affect hip stability and ability to walk, recording the natural history of clinical and radiological hip deformity. Two-thirds of the hips had become dislocated or subluxed by the end of the first year of life, involving 86% of hips in patients with an L3 level and 45% of those with an L4 level. All the hips that developed instability secondary to muscle imbalance did so within the first year. The neurological level was the most significant determinant of walking ability: all patients with L4 neurological levels could walk but only one-third of those with L3 lesions could do so. Hip stability, intelligence quotient and fixed deformity did not influence walking ability.