Automated Versus Manual Femoral Component Rotation Planning in Robotic-Assisted and Conventional Total Knee Arthroplasty: A Retrospective Comparison.

Background: The purpose of this study was to determine if using automated femoral rotation planning in robotic-assisted total knee arthroplasty (RA-TKA) was associated with differences in functional outcomes compared to patients who underwent manually set femoral rotation in RA-TKA or conventional TKA (C-TKA).

Methods: This was a retrospective multicenter study of patients who underwent TKA utilizing conventional methods with femoral component rotation set to 3° externally (C-TKA) [n = 108 knees], RA-TKA with automated femoral rotation planning intrinsic to the system (A-RA-TKA) [n = 111], and RA-TKA with femoral rotation manually set by the surgeon (M-RA-TKA) [n = 152], at least one year before follow-up. Outcome measures included the range of motion, Knee Injury and Osteoarthritis Joint Replacement (KOOS-JR), and Forgotten Joint Score (FJS). Intraoperative intercompartmental laxity measures and the rotational position of the femoral component relative to the posterior condylar axis were recorded.

Results: In the A-RA-TKA group, the mean improvement in range of motion was significantly higher compared to both the M-RA-TKA and C-TKA groups (22.7 versus 9.88 and 20.6°, respectively). Significant differences in improvement in KOOS-JR were not seen, but patients in the A-RA-TKA group had significantly higher mean FJS than the M-RA-TKA and C-TKA groups (71.0 versus 52.6 and 60.5, respectively). Femoral component internal rotation was significantly greater in the M-RA-TKA group than in the A-RA-TKA group (4.27 versus 1.00°, P < 0.001). The M-RA-TKA group had a significantly higher number of highly internally rotated femoral components (> 4.5°) compared with the other groups, which was associated with significantly lower rates of achievement of FJS and KOOS-JR patient acceptable symptoms state.

Conclusions: Compared to manually set femoral rotation, the use of automated femoral rotational planning facilitates intercompartmental gap balancing and prevents over-rotation of the femoral component, which may be associated with worse functional outcomes.