［Purpose］This study aimed to evaluate the differences in the immediate postoperative muscle strength around the hip and knee joints, joint range of motion, pain, and mobility between the anterolateral-supine (AL-S) approach, as a form of minimally invasive total hip arthroplasty (THA), and the posterior approach (PA), as a form of small-incision THA.

［Methods］The subjects were 68 patients with hip osteoarthritis who underwent unilateral THA for the first time. Maximal isometric muscle strength around the hip and knee joints, joint range of motion, walking ability, and pain were measured before surgery, and on Day 10, Day 21, and 2 months after surgery.

［Results］Significant interactions were found between the time and the type of surgery for hip abduction, external rotation, and extension strength. Interaction was also found between the surgical approach and the time required to achieve optimal hip extension range of motion.

［Conclusion］The differences in the functional recovery after AL-S approach and PA were most likely caused by differences in muscle damage. Therefore, it is necessary to customize rehabilitation programs according to the characteristics of each approach.

Purpose：The purpose of this study was to identify the determinants of walking ability on the first day after total hip arthroplasty (THA).Methods：We conducted a retrospective study of 78 joints that had undergone primary hemilateral side THA. We calculated the percentage of patients who successfully walked on the first day after THA and then performed a multiple logistic regression analysis, with walking condition on the first day after THA as the dependent variable and age, sex, body mass index, preoperative JOA score, intraoperative blood loss, and difference between preoperative and postoperative hemoglobin levels as independent variables.Result：Fifty-eight percent of the subjects started walking on the first day after surgery, with orthostatic hypotension listed as the most common reason for difficulty in walking. The multiple regression analysis revealed that intraoperative blood loss was significantly associated with walking ability on the first day after THA (p＜0.05).Conclusion：Walking ability on the first day after THA was more dependent on intraoperative blood loss than physical characteristics or preoperative hip function. Results of this study suggest that the amount of intraoperative blood loss is an important factor in determining the safety of early mobilization in THA patients.

Purpose：The purpose of this study was to identify the determinants of walking ability on the first day after total hip arthroplasty (THA).Methods：We conducted a retrospective study of 78 joints that had undergone primary hemilateral side THA. We calculated the percentage of patients who successfully walked on the first day after THA and then performed a multiple logistic regression analysis, with walking condition on the first day after THA as the dependent variable and age, sex, body mass index, preoperative JOA score, intraoperative blood loss, and difference between preoperative and postoperative hemoglobin levels as independent variables.Result：Fifty-eight percent of the subjects started walking on the first day after surgery, with orthostatic hypotension listed as the most common reason for difficulty in walking. The multiple regression analysis revealed that intraoperative blood loss was significantly associated with walking ability on the first day after THA (p＜0.05).Conclusion：Walking ability on the first day after THA was more dependent on intraoperative blood loss than physical characteristics or preoperative hip function. Results of this study suggest that the amount of intraoperative blood loss is an important factor in determining the safety of early mobilization in THA patients.