Relationship Among Global Femoral Offset, Leg Lengthening, and Tibiofemoral Rotation After Total Hip Arthroplasty

<b>Background/Objectives</b>: Several studies have described the changes in tibiofemoral rotation (TFRA) and patellar tilt angle (PTA) following total hip arthroplasty (THA). However, no studies have applied three-dimensional measurements to evaluate leg lengthening, changes in global femoral offset (GFO) or TFRA, or PTA during THA. Accordingly, this study employs three-dimensional measurements to test our hypothesis that increased leg lengthening is associated with an increase in TFRA, which increases PTA and worsens postoperative m-Harris Hip Score (mHHS). <b>Methods</b>: A total of 111 consecutive patients who underwent THA were enrolled. THA-related changes in GFO, femoral version, TFRA, PTA, and leg lengthening. Relationships between each parameter and the m-Harris Hip Sc were also assessed using the intraclass correlation coefficient. <b>Results:</b> Leg lengthening was significantly positively correlated with changes in TFRA and PTA. However, changes in GFO negatively correlated with changes in TFRA and PTA. Moreover, changes in GFO and leg lengthening were the only factors affecting changes in TFRA and PTA, respectively. <b>Conclusions</b>: Direct relationships exist between changes in GFO and changes in TFRA and PTA. This may be related to increased tension of the adductor muscles and medial soft tissue around the knee, ultimately reducing strain on the patellofemoral joint and improving knee pain.