The influence of humeral head inclination in reverse total shoulder arthroplasty: a systematic review

Humeral component inclination may play an important role in implant stability and the incidence of scapular notching in reverse total shoulder arthroplasty (RTSA). This study was conducted to determine if a difference exists between RTSA prostheses with a 135° vs 155° humeral component inclination angle with respect to dislocation rates and scapular notching rates. We hypothesized that the rate of dislocation would be significantly higher with the 135° inclination design and that the rate of scapular notching would be significantly higher with the 155° inclination design.

A systematic review was registered with PROSPERO and performed with Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines using 3 publicly available free databases. Therapeutic clinical outcome investigations reporting the number of dislocations, number of patients with scapular notching, and postoperative range of motion after RTSA with levels of evidence I to IV were eligible for inclusion. All study and subject demographics were analyzed. Statistics were calculated using 2-proportion z tests.

Thirty-eight studies including 2222 shoulders (average age, 70.3 ± 3.91 years; 67% female) undergoing RTSA were included. Of these, 1762 (79.3%) used the 155° inclination prosthesis and 460 (20.7%) used the 135° inclination prosthesis with a lateralized glenosphere. The rate of scapular notching was 2.83% in the 135° group and 16.80% in the 155° group (P < .0001, z = -7.7107). The rate of dislocation was 1.74% in the 135° group and 2.33% in the 155° group (P = .4432, z = -0.7669).

Our systematic review of 38 studies and 2222 shoulders found that the rate of scapular nothing was significantly higher with the 155° prosthesis than with the 135° prosthesis with a lateralized glenosphere, with no difference in dislocation rates between prostheses.