Abstract
The occurrence of impingement can lead to instability, accelerated wear, and unexplained pain after THA. While implant and bony impingement were widely investigated, importance of soft tissue impingement was unclear. In the THA through posterior approach, it is known that posterior soft tissue repair can decrease the risk of dislocation. However, it is not known whether anterior soft tissue impingement by anterior hip capsule will influence hip ROM. The purpose of this study is to quantitatively measure the effect of anterior capsule resection on hip ROM in vivo during posterior approach THA using hip navigation system.
From June 2011, 26 hips (25 patients) that underwent primary THA using Stryker CT-based hip navigation system were the subjects. All were female osteoarthritis patients and the average age at the operation was 59 (47–76) years. Intraoperatively, acetabular cup and femoral stem placement were performed through posterior approach under the navigation system. After reduction of the joint, we measured hip ROM using the same navigation system. We measured them before and after the resection of anterior hip capsule and compared the difference.
After the resection of anterior hip capsule, the average increases of ROM were 0.7±3.5 degrees for flexion, 2.3±2.3 degrees for extension, 1.1±2.3 degrees for abduction and 2.1±2.9 degrees for external rotation at flexion 0 degree compared with ROM before the resection. However, it significantly increased 7.5±5.1 degrees for internal rotation at flexion 90 degree (range; −3–20, paired t-test p<0.001) and 6.1±5.5 degrees for internal rotation at flexion 45 degree (range; −4–18, p<0.001).
In this study, we used navigation system for assessment of soft tissue impingement. We found that during posterior approach THA, resection of anterior hip capsule brought about significant increase of ROM, especially in the direction of flexion with internal rotation. We also found that this procedure did not change ROM of flexion, extension, abduction and external rotation. These results indicated that, during THA through posterior approach, resection of anterior hip capsule could reduce the risk of posterior instability without increasing the risk of anterior instability.
