Radiographic changes and clinical outcomes associated with an adjustable diaphyseal press-fit humeral stem in primary reverse shoulder arthroplasty.

Background: Press-fit humeral fixation in reverse shoulder arthroplasty (RSA) has become increasingly popular; however, radiographic analysis of these stems is limited. We aimed to evaluate the radiographic and clinical outcomes of an adjustable diaphyseal press-fit humeral stem in primary RSA.

Methods: We conducted a retrospective review of 232 primary RSAs in 219 patients performed by a single surgeon using this system. Radiographic outcomes were evaluated in patients with at least 2 years of radiographic follow-up. Standardized postoperative digital radiographs were analyzed for loosening, osteolysis, and stress shielding. Clinical outcomes in patients who also had complete clinical data sets were evaluated at the most recent follow-up.

Results: Radiographic evidence of loosening was identified in 1 RSA (0.4%) associated with deep infection. Aseptic loosening was not observed. No stems were identified as being at high risk for loosening. Internal stress shielding was observed proximal to the coated diaphyseal component in 226 shoulders (97.4%). This finding was often visible at 3 months (92.7%) and predictably progressed on subsequent radiographs. Progression beyond the 2-year period was rarely seen (4.4%). No external stress shielding or osteolysis was observed. Thirty-six complications occurred in 33 patients (15.1%). At an average follow-up of 36.6 months, significant improvements were identified in all measured clinical outcomes (P < .001).

Conclusion: Predictable fixation is achieved using an adjustable diaphyseal press-fit humeral system in primary RSA. Internal stress shielding is commonly observed but does not appear to compromise quality of fixation or clinical outcomes.