Abstract
Introduction
Many groups consider passive flexion to be a good indicator of postoperative success, to the point where this outcome directly influences certain outcome scores such as Knee Society Scores (KSS). However, it is alternatively believed that normal-like kinematics result in better TKA outcomes, and previous fluoroscopy studies have demonstrated that there are many parameters that affect weight-bearing range-of-motion. The objective of this study to investigate the correlations between patient-reported outcomes, passive flexion, and weight-bearing knee kinematics.
Methods
The femorotibial kinematics, passive and weight-bearing range-of-motion, and KOOS and KSS for 291 TKA subjects were collected in a retrospective study. The average age, BMI, and post-op time was 69.2±7.2 years, 29.3±4.6, and 22.4±16.3 months, respectively. Pearson correlation analysis was used to find the statistical correlations between the various parameters, and two-tailed t-tests were carried out to find statistical differences.
Results
Superior weight-bearing flexion was statistically correlated with both higher KOOS (r=0.2122, p=0.0094) and KSS (r=0.2986, p<.0001), shown in Table 1. Interestingly, there was no correlation with respect to passive flexion and KOOS (r=0.1363, p=0.0975). Correlations between KSS and passive flexion were not analyzed due to the inherent covariance between these parameters. Furthermore, subjects with paradoxical anterior sliding of either condyle had significantly lower KSS scores than those without anterior sliding (81.1±11.9 versus 84.4±12.4 for lateral, p=0.03, and 82.2±12.1 versus 85.1±12.5 for medial, p=0.02).
Conclusion
The results of this study revealed that weight-bearing flexion and not passive flexion is a better predictor of TKA outcomes. Subjects having greater weight-bearing flexion demonstrated higher KOOS and KSS scores. Also, subjects that experienced a paradoxical anterior slide had a statistically lower KSS than those subjects that experienced posterior femoral rollback. Therefore, it may be more important to evaluate weight-bearing flexion during clinical exams.
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