Abstract
Background:
Few clinical hip score include toe-reach motion after THA (put-on-socks, nail-cutting). Some reports have shown whether THA patients can put on socks or not in daily activity, and not shown how they can do it. The purpose of this study is to investigate real pattern of put-on-socks motion in daily activities after THA, and to evaluate safe range of motion for prevention of hip dislocation.
Materials and Methods:
Reviewing clinical chart, we investigated highly frequent pattern in wearing socks motion that would cause hip dislocation in ADL in 100 patients with normal lower extremities except for hip joint more than one year after THA, then, we classified the motion pattern. Using an optical 3-D motion analysis (MAC3D system, Motion Analysis, USA), we measured necessary angle of the hip in 10 THA subjects (mean age at operation 61 years old) one year postoperatively, while the patients make such frequent patterns of movement as above. Simultaneously, individual 3-dimensional skeletal model was reconstructed from CT data and implant CAD data. Driving 3-D skeletal model combined with motion analysis data on display (Zed Hip, LEXI), we calculated angle from posture that hip flexion angle was maximum during wearing-socks motion to impingement point (implant and/or bone) for each direction. ALL joint angle was defined as “zero” in supine position.
Results:
Resulting from clinical chart, high incident pattern of the motion was “Leg raising pattern” (26%), and “Trunk flexion pattern” (23%) (Figure 1). For above two pattern of the socks-wearing motion, 3-D motion analysis showed that maximum hip flexion angle was 85 ± 13 degrees for leg raising pattern, 88 ± 14 degrees for trunk flexion pattern. Hip angle of abduction/adduction or external/internal rotation was within mean 15 degrees during each motion. 3-D model simulation combined with motion data showed that 39 ± 15 degrees, 33 ± 9.7 degrees for direction of hip flection, 34 ± 17 degrees, 32 ± 11 degrees for direction of hip adduction and 78 ± 21 degrees, 51 ± 21 degrees for direction of hip internal rotation from posture on maximum hip flexion angle to impingement point for each motion, respectively. All cases showed safe range of more than 20 degrees for all direction and impingement occurred between cup and stem in all cases (Figure 2, 3).
Discussion:
Recently, there have been trend to decrease limitation of motion in ADL after THA. Safe range of motion without impingement have been enlarged resulting from development of implant design, proper alignment and operative technique. This study showed safe range without impingement in frequent socks-wearing pattern in daily living among THA patients one year after surgery. More research for motion in ADL can lead to remove postoperative restrictions in THA patients.
