Comparison of early outcomes of primary total knee arthroplasties performed using subvastus and medial parapatellar approaches and evaluation of quadriceps muscle elastography

Background In primary total knee arthroplasty (TKA) surgeries, the medial parapatellar (MP) and subvastus (SV) approaches are frequently employed. The SV approach involves preserving the vastus medialis muscle, leading to debates about the possibility of earlier healing of the extensor mechanism. Shear wave elastography (SWE) is known for monitoring tissue healing. In this study, our research question revolves around whether there exist differences in tissue healing following MP and SV approaches. Unlike previous studies, we aim to investigate this difference using solely SWE, which provides a quantitative measurement specifically targeting the vastus medialis muscle. Methods We divided 17 patients into two groups: SV (10 patients) and MP (7 patients). SWE measurements and clinical scores were recorded before surgery and at the 3rd-month follow-up. The first straight leg raising days were also recorded. Results Both the MP and SV groups showed significant improvement in clinical scores postoperatively. Straight leg raising time was comparatively earlier in the SV group, but no significant difference was found. SWE measurements revealed similar recovery values in the vastus medialis muscle between the two groups. Conclusion Both MP and SV approaches demonstrate similar and favorable early outcomes in TKA surgery. The preservation of the vastus medialis in the SV approach does not lead to significant differences in clinical scores or muscle recovery compared to the MP approach. Trial registration The study was retrospectively registered on ClinicalTrials.gov on March 7, 2024 (NCT06297746). https://classic.clinicaltrials.gov/ct2/show/NCT06297746?id=am7mi3VB&draw=2&rank=1 .