The relationship of shoulder elevation strength to patient-reported outcome after anatomic total shoulder arthroplasty.

BACKGROUND

Most patient-reported outcome measures (PROMs) used to assess outcomes after anatomic total shoulder arthroplasty (aTSA) focus on pain and function. Although strength is considered an important component of function, only the Constant-Murley score (CMS) includes an objective measurement of shoulder strength. The purpose of this study was to evaluate the relationship between shoulder elevation strength (SES) and PROMs after aTSA for the treatment of primary glenohumeral osteoarthritis (GHOA).

METHODS

This was a retrospective analysis of 605 patients enrolled in a multicenter clinical database who underwent aTSA to treat primary GHOA. Patients were evaluated preoperatively and at 24 months after surgery. Outcome was assessed with the CMS, American Shoulder and Elbow Surgeons score, Western Ontario Osteoarthritis of the Shoulder score, Single Assessment Numeric Evaluation score, and patient satisfaction. Relationships between SES and outcomes were investigated.

RESULTS

The correlations between SES and the PROMs before and after treatment were very weak and weak, respectively (r ≤ 0.262 for all). The strength of the correlations between the absolute and adjusted CMS and the other PROMs varied from weak to moderate (r = 0.180 to r = 0.455), and the strength of the correlations was greater postoperatively. With the strength component removed from the CMS, the correlations between the CMS and other PROMs were stronger (r = 0.194 to r = 0.495).

CONCLUSIONS

Although measurement of SES provides objective information about shoulder function and outcome related to the treatment of primary GHOA with aTSA, the actual relevance to patients is unclear as the correlations between SES and PROMs were weak. Furthermore, the variable correlations between the CMS and PROMs call into question the exclusive use of the CMS and support the use of other PROMs that may more accurately reflect patient perception of outcome.