The shoulder stiffness scale: a validated tool for monitoring stiffness in arthroscopic rotator cuff reconstructions.

BACKGROUND

Postoperative shoulder stiffness after arthroscopic rotator cuff repair is common and clinically heterogeneous. Established shoulder scores assess pain and function, but do not specifically isolate stiffness during follow-up. The aim of this study was to validate the newly developed Shoulder Stiffness Scale (SSS) as a pragmatic monitoring tool for postoperative shoulder stiffness after arthroscopic rotator cuff repair (ARCR).

METHODS

From a cohort of 973 primary arthroscopic rotator cuff reconstructions, patients without concomitant joint pathology of the same or contralateral arm were included. The new SSS was based on three items related to shoulder pain, subjective and objective ROM ranging from 0 to 10 points. It was collected before surgery, as well as 6 and 12 months postoperatively, along with other pain level parameters, Constant Score (CS), Subjective Shoulder Value (SSV), Oxford Shoulder Score (OSS). Changes of the SSS and its subscales over time, Cronbach's alpha for internal consistency, bottom and ceiling effects were reported. Validity was investigated through SSS associations with other parameters of similar dimension, and functional scores.

RESULTS

The selected cohort with 740 patients showed postoperative shoulder stiffness in 12.7 %. The SSS averaged 5.1 points (SD 2.5) preoperatively, and decreased significantly to mean 2.9 (SD 2.4) and 1.6 (SD 1.9) at 6 and 12 months, respectively (p<0.001). Cronbach's alpha ranged from 0.612 to 0.740 between time points. The SSS showed significant correlation in all three subscales pain, subjective ROM and objective ROM as well as to the functional scores CS, OSS and SSV scores at baseline, 6 months and 12 months with correlation coefficients ranging from -0.302 (low) to -0.649 (moderate) at baseline and from -0.626 (moderate) to -0.719 (high) at 12 months.

CONCLUSIONS

The SSS demonstrated acceptable internal consistency and construct validity as a simple clinician-administered tool for monitoring postoperative shoulder stiffness after ARCR. It complemented existing scores by isolating stiffness as a distinct construct and may facilitate day-to-day clinical follow-up and patient communication.

LEVEL OF EVIDENCE: III.