The Effect of Focused Rehabilitation on Subscapularis Strength After Total Shoulder Arthroplasty

Study Design: This is a randomized, double-blinded, standard of care-controlled clinical trial. All adult patients undergoing anatomic total shoulder arthroplasty for glenohumeral osteoarthritis will be included and randomized after surgery into either the control group which is prescribed a standard rehabilitation protocol or the intervention group which also is prescribed the same standard rehabilitation protocol with the the addition of isolated subscapularis rehabilitation.

Purpose: To determine the subscapularis strength and function after anatomic total shoulder arthroplasty (aTSA) in patients who receive isolated subscapularis rehabilitation in addition to the standard rehabilitation protocol as compared to those who only receive the standard rehabilitation protocol at 12-month follow up. Specifically the investigators will measure subscapularis strength utilizing a dynamometer and subscapularis function utilizing isolated subscapularis physical examination testing: belly-press, bear-hug, and lift-off tests.

Hypothesis: The investigators believe that subscapularis strength can be improved using isolated subscapularis rehabilitation in addition to standard rehabilitation, leading to improved outcomes in patients receiving aTSA. This should also improve the post-operative physical examination predicting a functional subscapularis tendon.

Rationale and expectations: Anatomic total shoulder arthroplasty is often performed in patients with severe glenohumeral osteoarthritis that have an intact subscapularis. Often times it is seen that these patients return with positive isolated subscapularis tests, despite the subscapularis being intact after surgery. If these patients require revision surgery, an ultrasound is the only test that can be performed to evaluate the status of the subscapularis tendon. This study is difficult and not 100% accurate. It needs to be determined if the patient will need a reverse total shoulder arthroplasty due to the positive subscapularis test findings. Previous studies by Baumgartner et al. showed that patients that received a total shoulder arthroplasty with tenotomy improved liftoff, and bear-hug strength testing, but operative shoulder strength remained inferior to strength of the nonoperative shoulder. Patients with improvements in strength were more likely to have greater improvements in outcome scores and range of motion. It was noted that improvements in the shoulder activity level after anatomic total shoulder arthroplasty may be dependent on improvements in strength. The investigators believe that subscapularis strength can be improved using isolated subscapularis rehabilitation in addition to standard rehabilitation, leading to improved outcomes in patients receiving aTSA. This should also improve the post operative physical examination predicting a functional subscapularis tendon.

Research Plan: Patients to be included in the study will be those with glenohumeral osteoarthritis with an intact rotator cuff that are undergoing anatomic total shoulder arthroplasty. Exclusion criteris includes patients undergoing revision shouder arthroplasty, a previous subscpaularis rotator cuff repair or deficient rotator cuff, patients with inflammatory arthropathies, such as rheumatoid arthritis, and patients with a history of infection in the shoulder joint. Reverse total shoulder arthroplasty will be excluded. Non-English speaking patients will be excluded from the study in order to simplify communication with study participants. The control population will consist of patients undergoing the standard rehabilitation protocol for aTSA. Patients will be undergoing rehabilitation regardless of study participation.