MIDDLE TERM RESULTS OF SIMPLE OPEN HIP REDUCTION OF IRREDUCIBLE DEVELOPMENTAL DYSPLASIA OF THE HIP BEFORE WALKING AGE

When developmental dysplasia of the hip (DDH) is irreducible by conservative means, then surgical open hip reduction is the choice. When done before walking age simple open hip reduction is most often enough to stabilize the hip. We tested the hypothesis that simple open hip reduction (SOHR) gives enough stability even in severe Tonnis 4 grades of dislocation. We tried to find what is the cut-off age to safely perform SOHR with lower complications. We analyzed 123 children with 193 open hip reductions of irreducible DDH for the period 1995 - 2000 with X-ray follow-up of at least 4 years and full documentation. Mean age at follow-up was 8 years and 5 months. Age at operation -7 months to 7.5 years. The traditional surgical technique of open hip reduction in these children was performed through lateral Murphy's approach but with modification by sparing the attachment of the piriformis muscle with the underlying blood supply to the epiphysis during circumferential capsulotomy. We used McKay clinical criteria, radiological classifications of Tonnis, Severin, Herring-Mose and Kalamchi & MacEwen. When analyzing the results, there came up a strong statistical correlation between bilaterality and Tonnis grade 4. The final CE angle of Wiberg was on average 28 degrees. According to Severin classification: 74% were excellent and 10% good or 84% successful results. But according to Herring-Mose sphericity scoring - 60% were good and 30% fair. Mose's Fair is a potential cam-type femoro-acetabular impingement (FAI). Clinically according to McKay criteria - 10% excellent and 54% good, or 64% of the operated hips were clinically acceptable, which correlates more with the radiological results according to Mose than with those of Severin. Avascular necrosis (AVN) of the femoral head according to Kalamchi was: Type I - 6%, Type II - 12%, Type III - 0%, Type IV - 8%. Types II and IV represent 20% of the operated hips. The presence of ossific nucleus in the femoral epiphysis on initial X-ray did not have a statistical impact on AVN frequency. When analyzing the impact of severity of dislocation in group 4 according to Tonnis and trying to find the cut-off age for fewer complications, there came up a strong statistical significance between AVN IV type appearance in Tonnis grade 4 hips when age at operation was above 9 months. The thorough capsuloplasty after femoral head (FH) reduction in the acetabular socket is enough for stability even in Tonnis 4. When OR age is below 9 months severe FH AVN is lower and Herring-Mose FH sphericity scoring is higher.