Medial parapatellar surgical approach leads to greater loss of postural sway complexity compared to mid-vastus approach in women undergoing total knee arthroplasty.

Purpose: Total knee arthroplasty (TKA) is associated with acute postoperative effects that increase the risk of falls. These effects differ between the medial parapatellar (PP) and mid-vastus (MV) surgical techniques but have not been evaluated in terms of postural sway complexity. Loss of this complexity leads to increased randomness in the center of pressure and higher fall risk. This exploratory comparative analysis addresses this knowledge gap by examining how PP and MV techniques affect postural sway complexity in women.

Methods: Twenty women with osteoarthritis (OA) were randomly assigned to TKA via the PP or MV approach. Postural sway data were collected at: 1 day before the surgery (Pre), 5 days (Post), 2 weeks, and 1 month post-surgery. We also included an age- and sex-matched healthy control group (n = 11) with a single assessment of their postural sway. The temporal structure of variability was evaluated in terms of its complexity. We quantified the complexity of postural sway using detrended fluctuation analysis (DFA) and multi-scale entropy (MSE).

Results: The α exponent (DFA) and MSE values showed significant effects of time in both axes, with both surgical groups exhibiting a shift towards more random patterns following TKA. When compared to controls, the PP group exhibited a significantly lower α exponent, indicative of more random patterns, at 2 weeks and 1 month but not at Pre and Post, while no such differences were observed for the MV group. Lower α exponent and higher MSE values reflect reduced sway complexity.

Conclusions: These findings suggest that TKA leads to loss of complexity in women during the postoperative stage, with the PP approach resulting in more pronounced reductions relative to healthy controls than the MV approach. Future studies should explore the long-term effects of TKA on postural sway complexity and the impact of rehabilitation protocols.

Level of evidence: N/A.