Direct anterior approach with conventional instruments versus robotic posterolateral approach in elective total hip replacement for primary osteoarthritis: a case-control study

Background The purpose of this study is to compare peri-operative and short-term outcomes in patients who underwent elective total hip replacement (THA) for primary osteoarthritis (OA) with direct anterior approach (DAA) versus a pair -matched cohort of patients who underwent robotic -assisted THA with posterolateral approach. Materials and methods Data from consecutive patients who underwent elective hip replacement from 2021 to 2023 for primary OA were retrospectively retrieved and divided into two groups: the DAA group, who underwent THA with the DAA approach using conventional instruments, and the robotic posterolateral (R -PL group), who underwent robot arm -assisted THA with the posterolateral approach. Comparative assessed outcomes were: operative time, radiographical implant positioning, intake of rescue analgesics, blood loss, transfusion rate, leg length discrepancy and functional outcomes (Harris hip score and forgotten joint score). Results A total of 100 pair -matched patients were retrieved with a mean age of 66.7 +/- 10.7 (range: 32-85) years and a mean follow-up of 12.8 +/- 3.6 (range: 7-24) months. No differences in patients' characteristics were detected. Patients in the R -PL group required less rescue tramadol (p > 0.001), ketorolac (p = 0.028) and acetaminophen (p < 0.001). There was no significant difference in the operative time between (MD = 5.0 min; p = 0.071). Patients in the DAA group had significantly lower Hb levels at day 1 (p = 0.002) without significant differences in transfusion rate (p = 0.283). Patients in the R -PL group had shorter length of stay (LOS) with a mean difference of 1.8 days [p < 0.001; 95% confidence interval (CI) 1.4-2.3]. No difference in clinical outcomes was found [leg length discrepancy (LLD), p = 0.572; HHS, p = 0.558; forgotten joint score (FJS), p = 0.629]. No radiographical differences were measured in cup inclination (MD = 2.0 degrees, p = 0.069), malpositioning [odd ratio (OR) = 0.2; p = 0.141], stem alignment (OR = 0.3; p = 0.485) and stem sizing (OR = 1.5; p = 1.000). There was no difference in complication rate except for lateral femoral cutaneous nerve damage, which was higher in DAA group (p < 0.001). Conclusions R -PL and DAA THA had comparable short-term clinical and radiological outcomes along with similar complication rates. The R -PL group showed significantly lower Hb drop, rescue analgesic consumption and shorter LOS. This is a preliminary study and no strong recommendation can be provided. Further prospective randomized trials are requested to further investigate the cost-effectiveness of robotic surgery in THA.