Relationship of Thenar and Hypothenar Muscle Thickness with Clinical Factors, Thigh Muscle Thickness and Physical Performance in Female Patients with Rheumatoid Arthritis

Abstract

Objective: The aim of this study was to evaluate hand muscle thickness in patients with rheumatoid arthritis (RA) and to investigate the relationship between muscle thickness and clinical factors and physical performance indicators. Materials and Methods: This cross-sectional study was conducted with 73 female participants between May 2022 and September 2022 (mean age: 60.83 +/- 9.73 years, range: 18-85). Among them, there were 37 RA patients (mean age: 60.8 +/- 9.9 years) diagnosed according to the 2010 American College of Rheumatology/European League Against Rheumatism RA classification criteria. The remaining 36 females were age- and sex-matched healthy subjects (mean age: 60.9 +/- 9.8 years). Thickness measurements of the thenar, hypothenar, and thigh muscles were obtained with ultrasound for all participants. In both groups, hand grip strength was measured using a hand dynamometer, and lower extremity performance assessments were made using 6-meter timed walk test (6MTWT) and a 5-time sit-to-stand test (5XSST). Disease activity score-28 (DAS-28), RA articular damage score (RA-ADS), and Duruoz Hand scale scores of RA patients were calculated. Results: Compared with the control group, thenar (p=0.004), hypothenar (p=0.000), and thigh (p=0.006) muscle thickness values were lower in RA patients. The RA group showed lower mean hand grip strength, longer time to complete 5XSST, and slower gait speed on 6MTWT (all p<0.01). Hand muscle thickness was negatively correlated with disease duration, RA-ADS, Duruoz Hand scale, and positively correlated with hand grip strength. Thigh muscle thickness was negatively correlated with age and 5XSST and positively correlated with hand grip strength and gait speed. Thickness measurements from all three muscles were not correlated with DAS-28. Conclusion: Hand muscle thickness of RA patients is affected by the disease regardless of age. Disease duration, articular damage, and decreased hand functions are closely related to muscle thickness. Low muscle thickness indicates reduced physical performance.