Handheld Dynamometry Shows Moderate Reliability and Responsiveness in Assessing Shoulder Muscle Strength After Rotator Cuff Repair

Abstract

Purpose

To evaluate both the reliability and responsiveness of handheld dynamometry (HHD) in assessing shoulder external rotation, flexion, and internal rotation strength during long-term follow-up in patients following rotator cuff repair and to provide evidence for the clinical utility of HHD in this context.

Methods

This retrospective study investigated patients who underwent arthroscopic rotator cuff repair between 2014 and 2019. Patients with repeat tears were excluded. Muscle strength was assessed preoperatively and at 6, 12, 18, and 24 months postoperatively using a handheld dynamometer. Test-retest reliability was evaluated using intraclass correlation coefficients (ICCs) from linear mixed-effects models, while responsiveness was assessed via minimal clinically important difference (MCID) calculations. Missing data were handled with multiple imputations, and statistical analyses were performed using R.

Results

A total of 124 patients (mean age: 64.4 ± 9.8 years) were included, with 69.4% of surgeries performed on the right shoulder. Moderate reliability of HHD was shown for muscle strength measurements, with intraclass correlation coefficients ranging from 0.59 to 0.69. Muscle strength and MCID achievement rates improved significantly over 24 months (P < .001). For 90° of abduction, muscle strength increased from 47.4 ± 42.6 N preoperatively to 103.2 ± 45.9 N at 24 months postoperatively, while the rate of MCID achievement at 24 months postoperatively was 80.7%.

Conclusions

HHD showed moderate reliability and responsiveness in assessing shoulder muscle strength after arthroscopic rotator cuff repair. Significant improvements in muscle strength and MCID achievement rates were observed over 24 months, suggesting the potential utility of HHD for monitoring recovery in this patient population.

Level of Evidence

Level IV, retrospective diagnostic case series.