Summary
Femorotibial rotational change and femorotibial rotational mismatch are related to poorer clinical outcomes in TKA
Abstract
Introduction
Coronal alignment or sagittal alignment has attracted more attention in total knee arthroplasty (TKA). However, the increased use of perioperative computed tomography (CT) has recently promoted a greater focus on axial rotational alignment. The change in rotational alignment between the femur and tibia induced by TKA is not well-characterized. Moreover, it is not clear if the femorotibial rotational change should be avoided or not. Additionally, postoperative femorotibial rotational malposition called anatomical rotational mismatch is associated with poor clinical outcomes. However, it is not clear whether the postoperative rotational mismatch is induced by TKA, because of wide variability in preoperative femorotibial rotational alignments. This study aimed to evaluate the postoperative femorotibial rotational mismatch and the femorotibial rotational change in TKA and their effect on postoperative patient‐reported outcome measures (PROMs).
Methods
This was a prospective study of 250 knees that underwent TKA for knee osteoarthritis. Femorotibial rotational angle (FTRA) was used as the femorotibial axial rotational parameter in postoperative and preoperative CT. FTRA was defined as the angle of the anatomical tibial anteroposterior axis (Akagi’s line) relative to the line perpendicular to the femoral surgical epicondylar axis in both CTs. The tibial and femoral lines were defined on preoperative CT, and preoperative FTRA was measured. Postoperative FTRA was measured on postoperative CT, which projected the preoperative femoral and tibial landmarks using a surface matching in a 3D software program. Perioperative FTRA change >5° and postoperative FTRA >5° were defined as rotational change (RC) and rotational mismatch (RM), respectively. PROMs were evaluated using Pain, Symptom and ADL subscales in Knee Injury and Osteoarthritis Outcome Score (KOOS), and the 2011 Knee Society Score (KSS) preoperatively and 1 year postoperatively. All knees were classified into four groups (RM +/RC+, RM+/RC-, RM-/RC+, and RM- /RC-) to investigate the relationship between RM and RC.
Results
Mean postoperative FTRA was 5.3° ± 5.3° (mean ± standard deviation). RM occurred in 54.4% of knees (n=136). RM was associated with significantly lower satisfaction scores in KSS, ∆Pain (∆: postoperative-preoperative value), and ∆ADL in KOOS compared to knees without RM (p = 0.04, <0.01, 0.03). Mean perioperative change of FTRA was 4.8° ± 3.7°. RC occurred in 40.4% of knees (n= 101) RC was associated with significantly lower objective and satisfaction scores in KSS and all ∆subscales in KOOS compared to knees without RC (p = 0.04, 0.01, <0.01, 0.01, <0.01). The distribution of knees in RM+/RC+, RM+/RC-, RM-/RC+ and RM-/RC- groups were 26.4%, 28.0%, 13.6% and 32.0%, respectively. RM+/RC+ knees showed significantly lower ∆Pain and ∆ADL in KOOS compared to RM-/RC- group (p = <0.01, 0.03).
Conclusions
Femorotibial rotational change and rotational mismatch were related to poorer clinical outcomes in TKA. In particular, femorotibial mismatch with femorotibial rotational change was associated with worse clinical outcomes.