Eligibility criteria
Institutional Review Board approval was obtained for the study. Consecutive patients who received R-THA or M-THA between January 2020 and January 2022 had their records examined. Patients with femoral head osteonecrosis who received R-THA or M-THA performed by one surgeon and had complete medical records were included in the study.
Participants who had autoimmune diseases, rheumatoid arthritis, abnormal preoperative inflammatory markers, bilateral simultaneous THA, a history of surgery or infection in the operative hip, neuromuscular dysfunction that affected lower limb function, coagulation dysfunction, liver or muscle disease, or a "complicated" postoperative hospital stay were all excluded from the study.
A total of 218 patients were included in this study, including 120 and 98 in the M-THA and R-THA groups, respectively.
R-THA surgical technique
R-THA was assisted by the MAKO robotic arm interactive orthopedic system (MAKO Rio Robot). The Accolade II femoral stem (Stryker) and Trident acetabular cups (Stryker) were used, along with a tapered cementless stem and cementless acetabular cups. The surgery was performed under general anesthesia using a standardized posterolateral approach. To fix the pelvic array, three pins were implanted at the anterior superior iliac spine during R-THA. An intraoperative assessment of leg length was then performed using fixed adhesive electrodes attached to the patella. In order to determine leg length and offset, the pelvic array was attached and a locating pin was placed at the outer edge of the greater trochanter. Joint dislocation and femoral neck osteotomy followed. By inserting a pelvic checkpoint screw outside the acetabulum, the acetabulum was registered. Three acetabular direction points, 32 registration points, and eight confirmation points were involved in acetabular registration. We constructed a three-dimensional computed tomography (CT) model of the bone structure prior to surgery. According to the preoperative plan, robotic-assisted acetabular reaming and acetabular cup implantation were performed under real-time three-dimensional navigation. Implantation of the acetabular screws and liner, and manual preparation of the femur were performed. It was confirmed that the hip joint was stable throughout its full range of motion. The landmarks that were used to determine the leg length and offset were marked. Finally, the femoral stem and head were implanted.
M-THA surgical technique
M-THA uses the same approach and implant design as the R-THA, but the acetabular surgery was manually performed. The acetabular bottom was prepared with the smallest available reamer, and the acetabulum was prepared using larger reamers before the acetabular cup was implanted.
Rehabilitation treatment
The patients in both groups received the same treatment, including intravenous and topical tranexamic infusions, as well as antibiotics within 24 hours of surgery.
Data collection
The levels of CRP, IL-6, hemoglobin (Hb), creatine kinase (CK), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), platelet (PLT), white blood cell (WBC), neutrophil rate, and lymphocyte rate, as well as the erythrocyte sedimentation rate (ESR), as evaluated preoperatively and on postoperative days 1 and 3, were compared between the two groups. The delta drop of Hb from preoperative also calculated and compared between the two groups. The operative time was defined as that between making and closing the incision. The postoperative HHS and FJS were collected 6 months in all patients. The blood transfusion rates and complications, including fracture, infection, dislocation, nerve injury, aseptic loosening, and osteolysis, were recorded.
Statistical analysis
Descriptive statistics are presented as mean ± standard deviation. The Student's t-test was applied to compare continuous parametric variables between groups. An analysis of categorical variables was carried out using chi-square tests or Fisher's exact tests. All statistical tests were performed at a probability level of 95% (α = 0.05) using SPSS software (version 25.0; IBM Corp., Armonk, NY, USA).