Immediate Postoperative Ultrasound Assessment of Quadriceps Muscle and Femoral Nerve Morphology After Total Knee...

Robot-assisted total knee arthroplasty (rTKA) has been introduced to improve surgical accuracy, but its effects on periarticular soft tissues in the early postoperative period remain insufficiently described. Ultrasound imaging allows non-invasive assessment of muscle and nerve morphology after surgery. The primary objective of this exploratory case series was to demonstrate the feasibility of early postoperative ultrasound assessment and to describe quadriceps muscle and femoral nerve morphological findings, thereby providing a methodological framework for future longitudinal studies.

This prospective exploratory ultrasound case series included 11 patients undergoing conventional TKA (n = 5) or rTKA (n = 6). Quadriceps muscle thickness (rectus femoris, vastus intermedius, vastus medialis, and vastus lateralis) and femoral nerve morphological parameters were assessed preoperatively and within the first 24 h after surgery. Analyses focused on descriptive within-group pre-post variations, with effect sizes and percentage changes reported to characterize the magnitude and direction of observed changes. The study was not designed or powered for inferential or inter-group comparisons.

Postoperative variations in quadriceps muscle thickness were observed in both surgical groups, most consistently in the rectus femoris and vastus intermedius, while changes in the vastus medialis and vastus lateralis were smaller and less consistent. In contrast, femoral nerve morphological measures demonstrated minimal variation, representing a relatively stable pattern across individuals. Overall, the observed changes were small in magnitude and showed inter-individual variability.

At this early postoperative time point, the observed ultrasound findings primarily reflect initial postoperative tissue behavior rather than structural adaptation. The relative stability of femoral nerve morphology represents a reassuring descriptive observation, while the small and variable quadriceps changes highlight the need for cautious interpretation at this stage.

This exploratory case series demonstrates the feasibility of early postoperative ultrasound assessment of quadriceps muscle and femoral nerve morphology following conventional and robot-assisted TKA. These descriptive findings provide preliminary data and a methodological basis for future longitudinal studies integrating functional and clinical outcomes.