In the period 1991 to 1993, twenty-five patients had Tonnis Triple Pelvis Osteotomy (TPO) performed. The presenting condition was primary or residual acetabular dysplasia. The age range was 24 to 54. Fifteen operations were on the left and two patients had bilateral operations at intervals of more than one year.

The anterior approach (Salter incision) was limited to an internal dissection, with the most limited possible abductor elevation of 2cm at the level of the iliac osteotomy. An Orthofix leg-lengthener was used intraoperatively to manoeuvre the central acetabular fragment, to accurately correct the presenting deformity as determined by CT scans. Two or three 6. 5mm screws were used to fix the osteotomy. No immobilisation was used. Mean blood loss was 580mis (range 375–1050mis).

All patients presented with pain, and only two patients had (mild) pain at review. The adult acetabular index was corrected from mean 31 deg to mean 4deg (max 1 Odeg). The CEA was corrected from mean 8 deg to 20–35 (mean 29) degrees. There was one temporary sciatic neuropraxia in the first patient. One patient has been converted to a resurfacing. Harris Hip Scores (HHS) have been measured yearly from three years post-op. Presenting HHS was mean 58 (range 44–72). At most recent follow-up it was mean 91 (range 79–1 00). Only two patients had HHS < 85. These patients had only 50% joint space at presentation. There was no reduction in HHS with longer follow-up. The operation shows durable and promising results in the medium-term, consistent with other series reported in Europe. The authors recommend that this type of operation be performed before any joint space narrowing develops, so that irretrievable deterioration occurs