Early improvement in shoulder external rotation proprioception after arthroscopic rotator cuff repair: an AMEDA-based...

Rotator cuff injury often disrupts shoulder proprioception. However, early postoperative recovery of external rotation proprioception after arthroscopic repair lacks quantification via ecologically valid tools. This study aimed to quantify early improvement in shoulder external rotation proprioception following arthroscopic rotator cuff repair using the Active Movement Extent Discrimination Apparatus (AMEDA), and to identify preoperative factors associated with postoperative proprioceptive improvement.

We included thirty-one patients with unilateral rotator cuff injury who underwent arthroscopic repair. Proprioceptive acuity was quantified as the area under the receiver operating characteristic curve (AUC). Pain (Visual Analogue Scale, VAS) and shoulder function (Constant-Murley Score, CMS) were recorded before and after surgery. The Shapiro-Wilk test was used to check normality. Paired $t$ -tests and Pearson correlations were applied to analyze which factors influenced proprioceptive improvement ( $\Delta \text{AUC}$ , defined as postoperative AUC minus preoperative AUC).

Preoperatively, injured shoulders showed significantly lower proprioceptive AUC than the contralateral sides ( $p<0.0001$ ). After surgical repair, affected-side AUC increased markedly, becoming statistically comparable to those of contralateral sides ( $p=0.1091$ ). At the same time, VAS pain dropped and CMS improved (both $p<0.0001$ ). The proprioceptive improvement ( $\Delta \text{AUC}$ ) had a strong negative correlation with preoperative AUC ( $r=-0.625$ ). After Bonferroni correction, only preoperative AUC remained statistically significant.

AMEDA enables credible, quantitative proprioception measurement for shoulder external rotation proprioception in patients with rotator cuff injury. Arthroscopic rotator cuff repair produces measurable early improvements in shoulder proprioception. A negative linear association between preoperative proprioceptive acuity and postoperative proprioceptive improvement is observed, supporting the need for personalized perioperative proprioception rehabilitation. However, longer-term follow-up is needed to confirm sustained improvement.