Developmental dysplasia of the hip in neonates: evolution of acetabular dysplasia after hip stabilization by brief Pavlik harness treatment.

BACKGROUND

The recommended treatment duration in neonates with developmental dysplasia of the hip (DDH) varies depending on whether prolonged Pavlik harness therapy is believed to favourably affect the course of the acetabular dysplasia. According to one theory, several months of additional Pavlik harness therapy after achieving hip reduction contributes to correct the acetabular dysplasia. Another theory holds that hip dislocation induces the acetabular dysplasia, which corrects spontaneously once the femoral head is properly seated in the acetabulum. Here, we evaluated this second theory by studying outcomes after early brief Pavlik harness therapy.

HYPOTHESIS

Acetabular dysplasia associated with neonatal hip instability undergoes self-correction provided stable hip reduction is achieved very early after birth. Therefore, the duration of Pavlik harness therapy can be substantially shortened.

MATERIALS AND METHODS

We defined hip instability as either reducible hip dislocation or a very easily dislocatable hip with a soft clunk precluding determination of spontaneous hip position as dislocated or reduced. Static and dynamic ultrasound scans were obtained. Patients with ultrasonographic instability (pubo-femoral distance>5mm with less than 50% of coverage) underwent a second physical examination and received treatment. We re-evaluated 42 abnormal hips in 30 patients after a mean follow-up of 6.7 years (range, 5-14 years). Mean age at treatment initiation was 5 days (range, 1-15 days) and mean treatment duration was 34 days (range, 15-75 days).

RESULTS

Mean acetabular angle was 20° (range, 12°-30°) and mean Wiberg's lateral centre-edge angle was 30° (range, 22°-35°). Blunting of the lateral angle of the bony roof was noted in 8 hips at last follow-up. In 1 patient whose hip was stable clinically but unstable by ultrasonography at 21 days of age, recurrent dislocation occurred at 5 months of age. The Severin class was 1a in all patients.

DISCUSSION

Despite continuing controversy about whether hip dislocation induces dysplasia or vice versa, the need for early treatment is universally recognised. The optimal treatment duration, however, remains debated. Proponents of the familial determinism of DDH consider that acetabular shaping is genetically programmed when the femoral head is centred in the acetabular socket. Others advocate routine prolongation of Pavlik harness therapy for 2 months or longer, based on the opinion that this strategy decreases the dislocation recurrence rate and that mechanical hip unloading may promote correction of the dysplasia. Mean treatment duration in our population was 34 days and our sole objective was to treat the instability. The hip was reduced and held in its proper position long enough to allow sufficient capsule and ligament tightening to stabilise the hip. Under these conditions, the acetabular dysplasia underwent self-correction that was not related to treatment duration.

CONCLUSION

Very early Pavlik harness therapy to ensure rapid hip reduction and stabilisation optimises the potential of the acetabulum for spontaneous remodelling.

LEVEL OF EVIDENCE

Level IV, retrospective study.