Correlation between Single Assessment Numerical Evaluation score and Lysholm score in primary total knee arthroplasty patients

Background There are numerous subjective rating scales available to evaluate outcomes of total knee arthroplasty (TKA). Single Assessment Numerical Evaluation (SANE) score was developed to reduce the burden of patients or clinicians to evaluate patients' status by asking patients to simply rate the current status of their injured body part on a scale of 0-100. The purpose of this study is to investigate the correlation between SANE score and Lysholm score in patients who underwent primary TKA. Methods Forty-nine patients who underwent primary TKA participated. Patients who underwent bilateral TKA or revision TKA were excluded from this study. They were asked to respond to SANE and Lysholm scores. Regression analysis was used to evaluate the correlation between 2 scores. Bilateral isometric quadriceps strength and limb symmetry index were also measured and recorded. Results There were a total of 49 patients in the study. The mean age of the subjects was 73.04 ± 6.63 years. The mean height and body weight were 153.37 ± 8.81 cm and 55.51 ± 8.61 kg, respectively. The mean scores for SNAE and Lysholm scores were 66.08 ± 16.77 and 71.0 ± 17.55, respectively. Pearson r correlation coefficient between SANE and Lysholm scores was 0.38 (P = .003). Regression analysis showed statistically significant correlation between 2 scores with r2 of 0.15 (P = .005). The average time from surgery was 16.02 weeks. The mean isometric quadriceps strength was 26.76 ± 11.30 kgf for the involved knee and 40.58 ± 11.55 kgf for the non-involved knee. The limb symmetry index was 66.10% ± 21.51%. Conclusions The results of the investigation showed that there was a statistically significant, however relatively weak, correlation between SANE score and Lysholm score. SANE score may serve as an alternative method to assess TKA patients' subjective post-operative outcomes to Lysholm score.