Quantifying success after total shoulder arthroplasty: the substantial clinical benefit

Abstract

An understanding of the substantial clinical benefit (SCB) after total shoulder arthroplasty (TSA) may help to gauge a minimum threshold beyond which a patient perceives his or her outcome as being substantially better. This study quantifies SCB for 7 outcome metrics and active motion measurements after shoulder arthroplasty and determines how these values vary based on prosthesis type, patient age at surgery, sex, and length of follow-up. A total of 1,568 shoulder arthroplasties with 2-year minimum follow-up were performed by 13 shoulder surgeons and enrolled in a multicenter registry. The SCB for the American Shoulder and Elbow Surgeons Shoulder Assessment, Constant Score, University of California Los Angeles Shoulder Rating Scale, Simple Shoulder Test, Shoulder Pain and Disability Index, global shoulder function, and visual analog scale pain scores, as well as active abduction, flexion, and external rotation were calculated for different patient cohorts using an anchor-based method. The anchor-based SCB results were American Shoulder and Elbow Surgeons score, 31.5 ± 2.0; Constant Score, 19.1 ± 1.7; University of California Los Angeles Shoulder Rating Scale score, 12.6 ± 0.5; Simple Shoulder Test score, 3.4 ± 0.3; Shoulder Pain and Disability Index score, 45.4 ± 2.2; global shoulder function, 3.1 ± 0.2; visual analog scale, 3.2 ± 0.3; active abduction, 28.5° ± 3.1°; active forward flexion, 35.4° ± 3.5°; and active external rotation, 11.7° ± 1.9°. Anatomic TSA patients, male patients, and patients of longer follow-up duration were associated with higher SCB values than female patients, reverse TSA patients, and patients of shorter follow-up duration. Our analysis demonstrated two-thirds of patients achieved the SCB threshold after TSA. Generally, a change of 30% of the total possible score for each outcome metric approximates or exceeds this SCB threshold.