Summary

The purpose of the present study was to evaluate whether reinsertion of the SSc in rTSA improves overall clinical outcomes and whether it improves active range of motion (ROM) and strength in IR. It also aims to compare whether the reinsertion of the SSc has the same effects in a 155° NSA inlay prosthesis (medialized design) compared to a 145° onlay prosthesis (lateralized design).

Abstract

Background

The role of the subscapularis tendon (SSc) in the Grammont designed reverse shoulder arthroplasties
(RSAs) has been a debated topic for several years. Some authors stated that the SSc repair may improve
anterior stability of the implant and increase strength in internal rotation (IR). In the past years, more
anatomic prosthetic designs were introduced having as main features a lateralized centre of rotation
(CoR) and/or a lower neck-shaft angle (NSA) and curved onlay stems. Using these new implants, some
authors found no differences in term of instability rate if the SSc is repaired or not. Furthermore,
biomechanical studies demonstrated that non repairing the SSc requires much less strenght to be
generated by the deltoid for arm abduction. The purpose of the present study was to evaluate whether
reinsertion of the SSc in rTSA improves overall clinical outcomes and whether it improves active range
of motion (ROM) and strength in IR. It also aims to compare whether the reinsertion of the SSc has the
same effects in a 155° NSA inlay prosthesis (medialized design) compared to a 145° onlay prosthesis
(lateralized design).
Case Presentation
A retrospective comparative study from prospectively collected data was performed. Patients who
underwent surgery for primary RSA for osteoarthritis and cuff tear arthropathy between March 2013
and May 2018 performed by a single surgeon were included. The minimum follow-up was 2 years.
Patients were divided into four groups for data analysis: group 1 (Lat;SSc+) and 2 (Lat;SSc-) consisted
of patients who received a lateralized RSA with and without SSc repair respectively, whereas group 3
(Med;Ssc+) and 4 (Med;Ssc-) consisted of patients who received a medialized RSA with and without
SSc repair respectively. ROM, strength in IR, visual analog scale (VAS) for pain, Constant-Murley
score (CS), and the American Shoulder and Elbow Surgeons score (ASES) were assessed for
all patients preoperatively and at final follow-up.
Clinical Outcomes
75 patients were available for data collection and analysis (10 male and 65 female patients with a mean
age of 76±4.6 years) The mean follow up was 40.8 ± 13.1 months. No significant differences were
detected in the clinical parameters comparing the postoperative values of the Lat/SSc+ group and the
Lat/SSc- group. Conversely, patients belonging to the Med/SSc- group reported worse results than the
Med/SSc+ group in terms of VAS (1.4±1 vs 0.3±0.6), ASES (76.7±7.6 vs 84.8±5.9) and CMS score.
(62±11 vs 72.2±6). No difference was highlighted between the groups in terms of ROM in IR, while
higher values of strength in IR were obtained in the Med/SSc+ group compared to the Med/SSc- group.

Discussion

The management of SSc in RSA remains a not well-defined topic. When the SSc can be repaired, no
differences emerge from the use of a medialized or a lateralized design of the prosthesis. In case of
radiographic signs of an irreparable SSc tendon, it may be useful to choose a lateralized design implant.