Results of Tonnis-type acetabuloplasty in patients with developmental hip dysplasia

Aim: The aim of this prospective study was to evaluate the outcome of open reduction and Tönnis acetabuloplasty as the first method of treating developmental dysplasia of the hip (DDH) in children in early childhood at walking age. Materials and methods: Between 2005 and 2009, 34 hips of 34 children were operated on with the aforementioned method. Mean age was 25.6 (range 12-44) months, and mean follow-up was 3.6 years. During the follow-up period,the hips were evaluated using the acetabular index and for development of avascular necrosis and redislocation. Functional evaluation was also conducted. Results: Clinically, 97.3 % of patients had excellent and good results. The acetabular angle decreased from 45 preoperatively to 21 early postoperatively and at the last follow-up had improved to 18. In two hips, type 2 avascular necrosis developed. Hip instability was not observed, and no additional surgery was performed. Conclusion: Tönnis acetabuloplasty is a powerful tool to increase primary stability of the hip when acetabular coverage is inadequate in DDH. Besides its acute correction ability, when performed properly, it has no unwanted effects on acetabular growth. As an isolated procedure or as a part of combined open reduction and/or femoral osteotomy, Tönnis type acetabuloplasty is a safe and effective method. © 2012 The Japanese Orthopaedic Association.