UW Shoulder and Elbow Academy: Total shoulder arthroplasty: avoiding the biasing effect of outcome measures

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

These authors evaluated the relationship between shoulder elevation strength (SES) and patient reported outcomes (PROMs) after aTSA for the treatment of primary glenohumeral osteoarthritis (GHOA) in a retrospective analysis of 605 patients having aTSA for primary glenohumeral osteoarthritis.

SES was tested using a digital dynamometer before and after surgery. The examiners were instructed to have the patient position the arm at 90 of elevation or maximum elevation below the horizontal in the scapular plane and resist the examiner who was holding the dynamometer.

The correlations between SES and the PROMs were very weak before aTSA and weak after aTSA.

The authors concluded that while measurement of SES provides information about shoulder function and outcome related to the treatment of primary GHOA with aTSA, the actual relevance to the patient is unclear as the correlations between SES and PROMs were weak.

Comment: This is an important article, in that it demonstrates that so called "objective" measures, such as shoulder strength, are only weakly associated with patient self-assessed comfort and function. It is also important to recognize that the use of strength and range of motion measures in the assessment of arthroplasty outcomes introduces both observer variability (different examiners are likely to measure strength and range of motion differently) and selection bias (excluding the patients who are unwilling or unable to return to the surgeon's office for followup measurements). Computer based platforms (PROMIS, OBERD) have similar issues with selection bias by eliminating patients without access to the computer based platform. By contrast, the use of so called "subjective" patient reported metric (PRM) forms that can be completed with a pencil and mailed in to the surgeon enable the inclusion of patients unavailable for in-person followup while keeping the observer (the patient) constant. We must recall that the goal of outcome assessment is to capture the self-assessments of largest percentage of patients for the longest period of time after treatment.

Here is a related article, the key finding of which was that active range of motion correlated poorly with patients' self-assessed function of their osteoarthritic shoulders, meaning that the shoulder function was dependent on characteristics of the shoulder and the patient other than the active range of motion.

Relationship Between Patient-Reported Assessment of Shoulder Function and Objective Range-of Motion Measurements

In 74 male and 30 female patients with osteoarthritis the authors analyzed the relationship between the SST patient self-assessments of shoulder function and objective range-of-motion measurements recorded by the observer-independent Kinect motion capture system

For both female and male patients, they found a poor correlation between objective measurements of active abduction and the total SST scores of osteoarthritic shoulders.

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