NON ANATOMICAL POSITIONING (HIGH HIP CENTER) OF ZWEYMULLER CUP IN OSTEOARTHRITIS SECONDARY TO CONGENITAL HIP DISEASES

Abstract

AIM OF STUDY: The mid and long-term clinical and radiological evaluation of patients with degenerative arthritis secondary to congenital hip diseases with placement of the cup proximal to the true acetabulum.

MATERIAL AND METHODS: We operated on a total of 99 hips (90 patients) with arthritis due to CHD from 1996 to 2006. In 48 of these hips (mean age 55.8 yrs), the cup was inserted high.

The procedure was always performed with the patient in lateral position through a lateral transgluteal approach. We did not perform osteotomies of the greater trochanter or femur shortening osteotomies and the cup was placed where there was sufficient bone stock. The major determining factor in cup stability was the presence of sufficient anterior and posterior column. We also tried to insert the cup as medial as possible although in about half the group (25 out of 48), cup placement was superior and lateral. The limb length discrepancy was corrected by varying the neck length of the implant. A special stem was used in 5 cases.

The mean intraoperative time was 65 mins with minimal soft tissue disruption as compared with the classic methods. The patients were mobilized postoperatively in a couple of days.

RESULTS: Despite the higher rates described in literature, cup loosening occurred in only two hips and there was no incidence of stem loosening. There were no neurological complications. There were three complications in total: one DVT and two dislocations due to cup loosening as a result of mal-positioning.

CONCLUSIONS: The extremely low rate of cup loosening, improvement of Harris Hip Score and back pain, decreased intraoperative time are significant advantages of managing congenital hip diseases with the above technique using the uncemented Zweymüller implants. The long period of follow up (8 to 11 years for 31% of the patients) in this study is significant.