The Influence of Preimplant Balancing on Manipulation under Anesthesia Rates following Imageless Robotic-Assisted Total Knee Arthroplasty

Acquired idiopathic stiffness (AIS) following total knee arthroplasty (TKA) often requires manipulation under anesthesia (MUA). Robotic-assisted TKA (RA-TKA) systems provide gap balance templates for objective correlation with the rate of AIS. The purpose of this study was to assess intraoperative balancing parameters that were associated with MUA utilizing an "anatomical" implant design.We performed a retrospective chart review of 265 imageless RA-TKA procedures performed by R.M. and K.D. between 2018 and 2020. The primary outcome for AIS or clinically significant "arthrofibrosis" was MUA. Patient intraoperative gap planning data were examined for association.The rate of MUA was 8.7% (23/265), which was performed at a mean follow-up time of 75.9 ± 32.2 days. The lateral to medial gap difference in extension was significantly less in patients requiring MUA (odds ratio [OR] = 0.86, 95% confidence interval [CI], 0.75-0.99) (<i>p</i> = 0.034). Significantly less preoperative varus mechanical axis was associated with knees requiring MUA (1.83° vs. 4.04°, OR = 1.09, 95% CI, 1.00-1.19). Decreased templated mechanical axis correction was associated with MUA (2.09° vs. 4.75°, <i>p</i> < 0.0001).A tighter lateral-to-medial gap in extension, less preoperative varus, and smaller templated mechanical axis corrections were associated with increased rates of MUA.