Influence of diabetes mellitus on rotator cuff muscle strength recovery following arthroscopic rotator cuff repair: a prospective observational study

Abstract

Background: Arthroscopic rotator cuff repair (ARCR) is an established treatment for symptomatic rotator cuff tears, resulting in significant improvements in pain and shoulder function. However, objective assessment of postoperative rotator cuff muscle strength and its relationship with functional recovery remains inadequately reported. This study evaluated changes in rotator cuff muscle strength following ARCR, investigated whether improvements in strength correlated with functional outcomes, and examined the influence of diabetes mellitus on recovery trajectories.

Methods: A prospective cohort study was conducted at a tertiary care teaching hospital between September 2017 and September 2019. Patients aged 18-60 years with reparable rotator cuff tears undergoing primary ARCR were enrolled. Clinical evaluation included preoperative and six-month postoperative assessment of isometric and isokinetic internal and external rotation strength using a Kin-Com 125 AP dynamometer. Functional outcomes were assessed using the American shoulder and elbow surgeons (ASES) score and Constant score. Paired comparisons were performed to evaluate postoperative changes, and correlation analysis was used to determine the association between strength recovery and functional outcomes.

Results: Twenty-six patients completed the six-month follow-up. The mean age was 48.3 years, with 15 males and 11 females. Significant improvements were observed in both functional outcome measures, with mean increases of 53.8 points in the ASES score and 38 points in the Constant score (both p<0.0001). Isometric internal and external rotation strength increased by 11.5 Nm and 8 Nm, respectively. Significant improvements were also observed in isokinetic strength at angular velocities of 60°/s and 120°/s for both internal and external rotation (all p<0.0001). Despite these improvements, no significant correlation was identified between gains in rotator cuff muscle strength and postoperative functional outcome scores. However, subgroup analysis revealed that patients with concurrent diabetes mellitus demonstrated a markedly blunted recovery trajectory in torque gains compared to non-diabetic participants.

Conclusions: ARCR resulted in significant improvements in objective rotator cuff muscle strength and shoulder function at six months. However, early postoperative functional recovery did not correlate with the magnitude of muscle strength recovery, suggesting that patient-reported functional improvement is influenced by factors beyond muscle strength alone.