Reasons and prevention for postoperative dislocation following total hip replacement

Objective To investigate the cause and prevention of postoperative dislocation after total hip replacement. Methods Radiographic measurement and side lying abduction test were used in 350 patients to determine the influence of patient-related and operative factors and the position of the acetabular component on the rate of dislocation. Results Dislocation occurred in 15 of 350 after total hip arthroplasties: 12 of 255 primary procedures and 3 of 26 revisions and the defference was statistically significant( P ＜ 0. 01 ). The dislocation rate of patients, with a positiven side lying abduction test was 6. 15% ,otherwise the rate was 3.18%, and the difference was statistically significant( P ＜ 0. 05 ). The dislocation rate for cup orientation with anteversion of 15 ± 10 degrees and lateral opening of 40 ± 10 degrees was 2. 41% ,while outside this safe range of the dislocation rate was 13.3%. This defference was statistically significant ( P ＜ 0. 01 ). The dislocation rate of patients using high-side prosthesis acetabu-lum preventing dislocation was 3.08 % compared with 7.78% in those without such prosthesis acetabu-lum( P ＜0.05). The dislocation rate of patients using 28 mm in diameter femoral head prostheses was 3.17%, the dislocation rate of patients using less than 28 mm in diameter femoral head prostheses was 7.14%. This defference was statisticall significant ( P ＜ 0. 05 ). The difference of dislocation rate between patients with a posterolateral approach(5.14 % )and those with a reserving and reconstructing articular capsule( 3.43 % )apart from this approach was also statistically significant( P ＜ 0. 05 ). There was no relationship between the variables of age, weight and gender. Conclusions The causes of postoperative dislocation after total hip replacement are correlated with the position of prostheses, the balance of muscle force, reserving and reconstructing articular capsule, design of prostheses and revision arthroplasties. Precise implantation of prosthesis and good nursing care can decrease the mobidity of dislocation. Reduction should be in time when the dislocation occurred. The causes should be carefully analyzed for the recurrent cases and aggressive operation should be considered. Key words: Total hip replacement ;  Postoperative dislocation ;  Prevention and cure ;