Comparison of robot-assisted modified subvastus approach versus medial parapatellar approach in total knee arthroplasty: a retrospective cohort study

OBJECTIVE: This study aims to compare the short-term efficacy of the Mako robot-assisted modified subvastus approach (MA-MSVA) with the conventional medial parapatellar approach (MPA) in total knee arthroplasty (TKA). METHODS: This study included 275 patients who underwent TKA between May 2024 and May 2025, divided into the MA-MSVA group (n = 78), the MSVA group (n = 74), and the MPA group (n = 123). The three groups were compared in terms of early postoperative prosthesis alignment accuracy: mechanical tibiofemoral angle, mechanical lateral distal femoral angle, medial proximal tibial angle, lateral femoral component (the flexion angle of the femoral implant), lateral tibial component (the slope angle of the tibial implant) and outlier rates; clinical outcomes: International Knee Documentation Committee, five-level EuroQol five-dimensional questionnaire (EQ-5D-5 L), knee society score (KSS), visual analog scale (VAS) and range of motion (ROM); quadriceps muscle strength: knee extensors (KE ) and knee flexors (KF), and muscle injury markers: creatine kinase (CK) and lactate dehydrogenase. RESULTS: The MA-MSVA group demonstrated significantly superior prosthesis alignment accuracy compared with MSVA and MPA groups (P < 0.05), with the lowest outlier rate. On postoperative days (POD) 1 and 14, the MA-MSVA group demonstrated better outcomes in EQ-5D-5 L, KSS, VAS, and ROM than the other two groups (P < 0.05). Muscle injury in POD 1 was less severe (lower CK values), and muscle strength recovery was faster (higher KE and KF) within 30 days postoperatively in the MA-MSVA group. The MSVA group outperformed the MPA group in terms of early functional recovery and muscle strength recovery; however, its alignment accuracy was similar to that of the MPA group. CONCLUSION: MA-MSVA significantly enhances prosthesis alignment accuracy, accelerates early functional recovery, reduces pain, and promotes quadriceps strength recovery following TKA. While MSVA provides advantages in functional recovery over MPA, its alignment accuracy remains comparable. MA-MSVA technique, by combining precision with minimally invasive benefits, aligns with the enhanced recovery after surgery concept and merits clinical application. LEVEL OF EVIDENCE: Level III, retrospective cohort study.