Text

Objectives and questions: Historically, Grammont-style reverse shoulder arthroplasty (RSA) was associated with limited internal rotation (IR), commonly reflected in difficulty with personal hygiene. With recent design changes, this limitation appears far less prominent. Excellent active IR after RSA can be demonstrated by the German term “Schürzengriff” (tying a knot around the L3 vertebral level). The aim of this study was to investigate recovery of IR and patient-reported outcomes (PROMs) following lateralized–distalized RSA designs.

Material and methods: In this retrospective study based on prospectively collected data, patients with cuff tear arthropathy (CTA) and primary osteoarthritis (OA) undergoing RSA were identified. Two lateralized–distalized RSA designs were combined for analysis. Patients were stratified according to the type of metallic glenoid augmentation (centric +3 mm or eccentric full-wedge) and humeral stem design, with two short-stem systems used (Ascend Flex or Perform Humeral System [PHS]). Using data from a local shoulder arthroplasty registry, longitudinal changes in PROMs, range of motion, and abduction strength were analyzed using linear mixed-effects models. Fixed effects included time (baseline, 6, 12, and 24 months), implant group, and their interaction, adjusted for glenosphere position. Internal rotation was analyzed separately using cumulative link mixed-effects models with a logit link, treating IR as an ordinal outcome.

Results: A total of 164 patients were included, 62% of patients with CTA and 38% of patients with OA. Mean age at surgery was 75 years; 56% of patients were female. Analysis of functional IR demonstrated that most improvement occurred between 6 and 12 months, with continued gains up to 24 months. Compared with baseline, the odds of achieving a higher IR category were significantly greater at 6 months (OR = 2.44, 95% CI 1.28–4.65; p = 0.007), 12 months (OR = 4.66, 95% CI 2.26–9.61; p < 0.001), and 24 months (OR = 9.61, 95% CI 4.36–21.22; p < 0.001). At 24 months, 75% of patients achieved functional IR at or above the L3 level. Among the remaining 25%, 54.5% reached the lumbosacral region, 36.4% reached the gluteal region and 9.1% only reached the lateral thigh. No patient asked for revision surgery due to impaired IR. All PROMs also improved significantly over time (all p < 0.001).

Discussion and conclusions: Although the literature frequently describes functional gains after RSA as predominantly short-term rather than continuing throughout rehabilitation, functional IR showed progressive improvement up to 24 months in this cohort. Insufficient IR, historically associated with Grammont-style RSA, has largely resolved following the introduction of lateralized–distalized implant designs.