Determination of lower limb coordinate systems and application to clinical stydy using MDCT images

In functional test of hip joint, anatomical coordinate system is user. Anatomical coordinate systems are defined by inputting landmarks manually. Therefore decision of anatomical coordinate systems includes inter-and intra-operator variability. In addition, variability of anatomical coordinate systems will affect results of diagnosis and/or cause critical error of total hip arthroplasty (THA) is operation that replaces damaged hip joint by implants. This paper proposes automated definition of anatomical coordinate systems and evaluation method for clinical study. As a result of having applied proposed method, anatomical coordinate system was decided automatically. A result of comparing with pelvic coordinate systems was decided by orthopaedic doctors, an angle mean error ± standard deviation (SD) was 0.78 ± 0.34 deg and an position mean error ± SD was 2.6 ± 1.6 mm. As a result of having calculated pelvic tilt and symmetry of pelvis, the proposed method obtained useful data.