Anatomical and component rotational mismatches negatively affect postoperative outcomes in total knee arthroplasty

Anatomical rotational mismatch (ARM) refers to postoperative malrotation between the femur and tibia, and component rotational mismatch (CRM) refers to malrotation between the femoral and tibial components in total knee arthroplasty (TKA). This study aimed to quantify ARM and CRM and assess their individual and combined effects on postoperative outcomes.

This retrospective study analysed 224 knees that underwent primary TKA. Postoperative axial rotational angles between the femoral and tibial components (component rotational angle [CRA]) and between the femur and tibia (anatomical rotational angle [ARA]) were measured using computed tomography. Internal tibial or tibial component rotation relative to the femur or femoral component was assigned a positive value. Rotational mismatch was defined as CRA and ARA over ±10°. Clinical outcomes were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) 1 year postoperatively. Hierarchical cluster analysis categorised knees into two groups based on CRA and ARA (Groups 1 and 2).

The mean ± standard deviation (SD) postoperative ARA was 5.2° ± 5.3°, with ARM present in 16.1% of cases (36 knees). Knees with ARM showed significantly worse improvement in the KOOS pain subscale than those without ARM (p = 0.02). Postoperative CRA was 1.5° ± 4.5°, with CRM observed in 2.7% of cases (6 knees), but CRM alone did not significantly affect postoperative outcomes. Cluster analysis identified two groups (Group 1: 185 knees; Group 2: 39 knees), with Group 2 exhibiting greater CRAs and ARAs compared to Group 1 (both p < 0.01). Group 2 also had significantly worse KOOS pain and activities of daily living improvement relative to Group 1 (p < 0.01, 0.04).

Both CRM and ARM were observed following TKA. ARM negatively impacted postoperative outcomes, and the combined presence of CRM and ARM further worsened clinical results.

Level IV.