Rotational limb alignment changes following total knee arthroplasty.

PURPOSE: The aim of the present study was to assess the changes in rotational alignment introduced by total knee arthroplasty (TKA) and the reproducibility of pre- and postoperative CT measurements of rotational limb alignment. METHODS: For this purpose we analyzed data from 196 consecutive cruciate-retaining, fixed bearing Columbus TKA procedures. Both pre- and postoperative scans torsion difference CT scans were available for measurements in 89 cases. Using these CT scans the neck-malleolar angle (NMA), the femoral posterior condylar angle (fPCA), the tibial posterior condylar axis (tPCA) and the tibial torsion angle (TTA) were independently assessed by three raters. CT scans were re-evaluated 8 weeks later by the most experienced rater for assessment of intraobserver agreement. RESULTS: Measurements of all angles were prone to high standard deviations reflecting interindividual variability. Mean fPCA changed from 1.3° to 2.7° internal rotation preoperatively to 0.1°-1.9° internal rotation postoperatively. Based on a relative external rotation of the tibial base plate as compared to the preoperative situation, we found a relative internal rotation of the postoperative NMA and tibial torsion of 3°-5.4° and 6°-7.5°, respectively. Intra- and interobserver agreement was strong for all angles assessed (ICCs 0.7-1.0) except for fPCA (ICC 0.2-0.6). However, mean absolute measurement differences for fPCA were clinically acceptable (1.2°-2.6°). CONCLUSIONS: Reproducibility of CT rotational limb alignment measurements was found to be clinically acceptable. Rotational alignment of the femoral and even more so of the tibial component will ultimately affect the rotational alignment of the entire limb-at least when fixed bearings are used. LEVEL OF EVIDENCE: Diagnostic study, Level III.

Effect of Rotational Component Alignment on Clinical Outcome 5 to 7 Years After TKA With the Columbus Knee System.

The aim of the study was to examine the effects of rotational component alignment on outcome after total knee arthroplasty (TKA) with a minimum follow-up of 5 years. For this study, 96 patients were available for follow-up at a mean of 5.7 years after TKA. Computed tomography scans were available in 55 patients. Outcome (Oxford Knee Score [KSS], Knee Injury and Osteoarthritis Outcome Score [KOOS], 36-item Short Form Health Survey) was correlated with postoperative femoral and tibial component malrotation or femorotibial rotational alignment mismatch. Results showed that femoral or tibial component malrotation or femorotibial mismatch were present in 15.5%, 38.2%, and 29.1% of patients, respectively. Although femoral componoent malrotation was associated with significantly poorer, KSS and KOOS scores, outcome was comparable for patients with or without tibial component malrotation or femorotibial mismatch. In conclusion, both internal and external rotational femoral malalignment exceeding 3° is associated with significantly poorer subjective and objective outcome 5 to 7 years after TKA. Tibial component malrotation and femorotibial mismatch were more common, but did not significantly compromise outcome. [Orthopedics. 2016; 39(3):S50-S55.].