Most children with spastic hemiplegia have high levels of function and independence but fixed deformities and gait abnormalities are common. The classification proposed by Winters et al is widely used to interpret hemiplegic gait patterns and plan intervention. However, this classification is based on sagittal kinematics and fails to consider important abnormalities in the transverse plane. Using three-dimensional gait analysis, we studied the incidence of transverse-plane deformity and gait abnormality in 17 children with group IV hemiplegia according to Winters et al before and after multilevel orthopaedic surgery.

We found that internal rotation of the hip and pelvic retraction were consistent abnormalities of gait in group-IV hemiplegia. A programme of multilevel surgery resulted in predictable improvement in gait and posture, including pelvic retraction. In group IV hemiplegia pelvic retraction appeared in part to be a compensating mechanism to control foot progression in the presence of medial femoral torsion. Correction of this torsion can improve gait symmetry and function.

In a longitudinal case-control study, we followed 81 subjects with dysplasia of the hip and 136 control subjects without dysplasia for ten years assessing radiological evidence of degeneration of the hip at admission and follow-up. There were no cases of subluxation in the group with dysplasia. Neither subjects with dysplasia nor controls had radiological signs of ongoing degenerative disease at admission. The primary radiological discriminator of degeneration of the hip was a change in the minimum joint space width over time. There were no significant differences between these with dysplasia and controls in regard to age, body mass index or occupational exposure to daily repeated lifting at admission.

We found no significant differences in the reduction of the joint space width at follow-up between subjects with dysplasia and the control subjects nor in self-reported pain in the hip. The association of subluxation and/or associated acetabular labral tears with dysplasia of the hip may be a conditional factor for the development of premature osteoarthritis in mildly to moderately dysplastic hips.

Malposition of the acetabular component is a risk factor for post-operative dislocation after total hip replacement (THR). We have investigated the influence of the orientation of the acetabular component on the probability of dislocation. Radiological anteversion and abduction of the component of 127 hips which dislocated post-operatively were measured by Einzel-Bild-Röentgen-Analysis and compared with those in a control group of 342 patients.

In the control group, the mean value of anteversion was 15° and of abduction 44°. Patients with anterior dislocation after primary THR showed significant differences in the mean angle of anteversion (17°), and abduction (48°) as did patients with posterior dislocation (anteversion 11°, abduction 42°). After revision patients with posterior dislocation showed significant differences in anteversion (12°) and abduction (40°).

Our results demonstrate the importance of accurate positioning of the acetabular component in order to reduce the frequency of subsequent dislocations. Radiological anteversion of 15° and abduction of 45° are the lowest at-risk values for dislocation.