Summary
In advanced knee osteoarthritis patients, decreased skeletal muscle mass assessed by the sarcopenia index (serum creatinine/cystatin C ratio) was significantly associated with ADL decline.
Abstract
Objective
In Japan, a super-aging society, the number of patients with knee osteoarthritis (KOA) is expected to increase in the future. The elderly may be complicated by Sarcopenia, an age-related loss of muscle mass, but its measurement is not simplified.
Recently, it has been reported that the serum creatinine/cystatin C ratio (sarcopenia index: SI) correlates with skeletal muscle mass, and SI divided by body weight (SI/BW) is considered more accurate. In this study, we used SI/BW to examine the characteristics of skeletal muscle mass loss in patients with advanced KOA.
Methods
Retrospective, single center study was conducted. A total of 68 consecutive advanced KOA patients who underwent total/unicompartmental knee arthroplasty from April 2020 to June 2021 were recruited. To avoid the influence of renal function or other conditions that cause muscle atrophy, exclusion criteria included estimated glomerular filtration rate < 30, inflammatory disease, and general anesthesia surgery for other disease within a year. After application of exclusion criteria, 45 patients, 45 knees were included. Age, gender, Body Mass Index, Visual Analogue Scale, joint range of motion, SI/BW and patient-reported outcome scores (PROs) such as Knee Society Score (KSS), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Oxford Knee Score (OKS). Cut-off values of SI/BW were defined as 0.0145 (men) and 0.009 (women) respectively according to the previous report, and we defined patients’ group with SI/BW less than the cut-off value as SI+ and the others as SI-. We evaluated the percentage and characteristics of SI+. We also evaluated the association between SI/BW and PROs.
Results
The overall percentage of SI+ was 20.0% , while SI+ was significantly higher in males (57.1%) compared to females (3.2%) (p < 0.001). There was no significant difference in patient background other than sex between SI+ and SI-.
The association between SI/BW and each PROs were statistically analyzed using multiple regression analysis. There was no multicollinearity in the independent variables with variance inflation factor of 1.14 (age), 1.43 (BMI), 1.02 (sex), 1.38 (SI/BW) respectively. Among each PRO subscales, KSS functional activity score (ß: 0.34, 95%CI: 0.024 to 0.65, p-value 0.036), KOOS ADL (ß: 0.57, 95%CI: 0.28 to 0.86, p-value 0.00032), and OKS (ß: 0.45, 95%CI: 0.13 to 0.77, p-value: 0.0075) were significantly associated with SI/BW.
Discussion
This study revealed that 20% of patients with advanced-stage KOA have decreased skeletal muscle mass, and the percentage was higher in males. Decreased skeletal muscle mass was significantly correlated with lower activity-related scores such as KSS Functional activity, KOOS ADL and OKS. Rehabilitation interventions have been reported to improve clinical outcomes for KOA patients, and selective intervention for patients with reduced SI/BW can be aimed at improving efficiency. In addition, preoperative evaluation is important because TKA in patients with Sarcopenia is reported to have a high risk of complications. SI/BW is useful for preoperative risk assessment of patients.
In conclusion, SI/BW, which can be evaluated only by blood sampling, is simple and useful, and the results can be used for patient evaluation, efficient intervention, and risk management.