Dislocation rates after total hip arthroplasty vary from 1% to 8% and approximately 1% will require revision surgery to treat hip instability. From these revisions only 60% is successful with redislocation frequencies from 8.2% to 39%. A full-constrained acetabular cup can be used by hip surgeons as a measure of salvage. The purpose of this paper is to describe the complications the authors have encountered in a short postoperative period with the use of three different types of full-constrained acetabular cups.

Over a period of three years, between January 1999 and December 2001, 25 full-constrained acetabular components were implanted. Three different types of full-constrained prostheses were used: the Osteonics Bipolar Constrained Insert (Osteonics Corp., Allendale, NJ), the Ringloc Constrained Liner (Biomet Inc., Warsaw, IN) and the Trilogy Constrained Liner (Zimmer Inc., Warsaw, IN). In 14 cases the full-constrained cups were used in revision hip arthroplasty and in 4 cases as revision for failed full-constrained implants. Seven patients received a primary constrained acetabular prosthesis.

Of the 23 patients one woman died after a follow-up period of 25.5 months. The other 22 patients had an average clinical follow-up of 22.5 months, ranging from 16 to 47.5 months. In 8 prostheses 6 different postoperative problems were encounterd, resulting in a total of 32 % failures. Seven of the complications were different types of constrained acetabular cup disassembly and one complication was due to a failure at the interface between bone and the porous-metal surface. As alternative treatment option, the authors have used the Birmingham Hip Resurfacing (Midland Medical Technologies, Birmingham) Dysplasia cup with modular head in seven patients who sustained recurrent dislocations after multiple revision surgery, with only one failure (1/7 - recurrent dislocation) after a mean follow-up of two years.

In view of the high short-term complication rate (32%) in a follow-up period of three years, the authors strongly recommend judicious use of the constrained acetabular prosthesis. The component should only be applied as a salvage tool in selected patients in whom no other treatment options would be successful. In these cases the use of a constrained acetabular prosthesis might solve the problems encountered in the majority of patients, but it can never guarantee a problem-free course of this cup. Alternative options such as the use of large diameter femoral heads with a resurfacing cup, using a metal-on-metal friction couple should be considered as a worthwhile alternative in those cases.