Stress shielding in reverse shoulder arthroplasty using a proximally coated stem for proximal humeral fractures: Does it have clinical relevance?

Objectives: To evaluate the clinical significance of stress shielding in patients who have undergone an uncemented reverse shoulder arthroplasty (RSA) with a proximally coated stem for complex proximal humeral fractures (PHF) comprising 3 or 4 parts, assessed at 2 years postoperatively. Additionally, this study aims to examine the correlation between tuberosity healing and clinical outcomes.

Methods: Setting: Single Centre.Patient Selection Criteria: 43 patients underwent surgery involving a cementless RSA with an anatomical stem (Mini Stem of Zimmer Biomet ^® Comprehensive System) following an acute 3- or 4-part or 4-part with luxation PHF within 4 weeks of injury. Patients who were excluded from the study included those who passed away, did not have a minimum 2-year follow-up, or had undergone cemented RSAs or alternative humeral components, as well as those who required RSA due to fracture sequelae.Outcome Measures and Comparisons: Stress shielding, tuberosity healing and its positioning were evaluated. Clinical-functional assessments were made using the Constant and ASES scores. Furthermore, quality of life assessments, including QuickDASH score, SF-12, satisfaction test (SANE) and Visual Analogue Scale (VAS) were performed.

Results: Of the total shoulders, 6 (13.9%) were excluded, leaving 37 PHFs that met the inclusion criteria. The mean age at the time of surgery was 72 years (range, 61-85). Stress shielding was observed in 31 shoulders (83.8%). There was no observed correlation between stress shielding and clinical-functional or quality of life assessments. The greater tuberosity in patients without stress shielding was found to be above the tray (66.7%) (P < 0.05). Tuberosity healing was observed in 94.6% (35/37) of the shoulders.

Conclusions: No significant clinical difference was observed between patients with and without stress shielding in terms of short-term functional outcomes. Successful consolidation of the tuberosities can be attained even in cases with notable stress shielding.

Level of evidence: Level IV; Case Series; Treatment study.