[Reason analysis and treatment of acetabular component initial instability after primary total hip arthroplasty].

OBJECTIVE: To analyze the main reasons of acetabular component initial instability after primary total hip arthroplasty (THA) and to discuss the prevention and management.

METHODS: The clinical data were retrospectively analyzed from 19 patients undergoing revision for acetabular component initial instability after primary THA between January 2003 and June 2010. There were 11 males and 8 females, aged from 55 to 79 years (mean, 67.2 years). The locations were left hip in 9 cases and right hip in 10 cases. The cementless hip prosthesis was used in 12 cases and cement hip prosthesis in 7 cases. The revisions were performed at 3 weeks to 6 months after primary THA. The reasons of early failure were analyzed. Both the coverage rate of acetabulum-bone and the Harris hip score were compared between pre- and post-revision.

RESULTS: The main reason of acetabular component initial instability after primary THA may be unsuitable treatment of acetabulum, improper selection of acetabular component, and incorrect place angle of acetabular component. Sciatic nerve palsy occurred in 1 case and recovered at 7 weeks after revision. Slight fracture of the acetabulum in 1 case and healed at 3 months after revision. All incisions healed by first intention. No infection, vessel injury, displacement of acetabular component, or deep vein thrombosis occurred. The patients were followed up 11-73 months (mean, 28 months). At last follow-up, no acetabular component instability was observed. The coverage rate of acetabulum-bone was increased from 67.9% +/- 5.5% before revision to 87.7% +/- 5.2% after revision, showing significant difference (t = 11.592, P = 0.003). The Harris hip score at last follow-up (84.4 +/- 4.6) was significantly higher than that at pre-revision (56.5 +/- 9.3) (t = 11.380, P = 0.005).

CONCLUSION: Detailed surgical plan, proper choice of component, correct place angle and elaborative planning, and proficient surgical skill are necessary to achieve the initial stability of acetabular component in THA.