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

Abstract

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.