Integrity and function of the subscapularis after total shoulder arthroplasty

Background Reported healing rates of a subscapularis tenotomy have been extremely variable in the literature. The purpose of this study was to document the subscapularis healing rate after subscapularis tenotomy using ultrasound, and to correlate healing with physical examination findings and shoulder internal rotation strength. Methods Fifteen patients who underwent total shoulder arthroplasty due to unilateral osteoarthritis were evaluated after a minimum of 6 months follow-up with ultrasound, physical examination, and internal rotation strength testing. At surgery, a subscapularis tenotomy utilized to approach the shoulder. Postoperatively, no formal physical therapy program was utilized. Results Seven of the 15 shoulders had a complete tear of the repaired subscapularis tendon based on ultrasound examination. The lift-off and abdominal compression tests correlated poorly with the ultrasonographic condition of the subscapularis. The bear hug test using dynamometry did correlate with tendon integrity. Patients with a subscapularis tear after arthroplasty experienced significant weakness in isometric ( P = .01) and isokinetic ( P < .01) internal rotation strength testing, as well as significantly worse DASH scores ( P = .04). No patient demonstrated anterior subluxation on examination or by radiograph. Conclusion Subscapularis tear after total shoulder arthroplasty is a common finding, which cannot be diagnosed reliably by physical examination or radiographs. In this population, subscapularis integrity did not correlate with pain or subjective patient outcome. Failure to heal the subscapularis tenotomy is probably more common than has been previously reported based on only physical examination testing.