Short-term clinical and radiographic outcomes with modular long stem for revision reverse total shoulder arthroplasty

Background

When performing reverse total shoulder arthroplasty with compromised proximal bone fixation, surgeons must consider using specialized stems with a distal press-fit design. In this study, the authors report on the clinical and radiographic outcomes of patients who underwent surgical management with modular diaphyseal press-fit stems.

Methods

In 2017-2021, patients who underwent revision reverse total shoulder arthroplasty reconstruction with diaphyseal press-fit stems (Aequalis Adjustable Stem [AS] or Aequalis Flex Revive Stem [RS]; Stryker, Kalamazoo, MI, USA) with minimum 1-year follow-up were identified. Patients with complex proximal humerus and scapula fractures, neurological injuries, and custom humeral replacements were excluded. Demographics and clinical follow-up data including range of motion, Visual Analog Scale (VAS), Simple Shoulder Test (SST), American Shoulder Elbow Surgeons (ASES) Score, and Single Assessment Numeric Evaluation were retrospectively reviewed. Postoperative radiographs were reviewed for aseptic humeral loosening, periprosthetic instability, stress shielding, periprosthetic fractures, and humeral stem failure.

Results

Sixty-five patients (29 AS and 36 RS) had mean follow-up of 25 months (standard deviation ± 16). Mean anterior elevation improved from 57° ± 39 preoperative to 121° ± 31 postoperatively. Mean external rotation improved from 3° ± 17 to 34° ± 16. Mean internal rotation improved from 4° ± 13 to 35° ± 26. Mean VAS improved from 6.7 ± 2.2 to 2.9 ± 1.5. Mean SST improved from 13% ± 13% to 65% ± 22%. Mean ASES score improved from 19 ± 13 to 60 ± 18. Mean Single Assessment Numeric Evaluation improved from 25% ± 18% to 71% ± 17%. There were statistically significant differences in mean postoperative VAS (P = .0017), SST (P = .025), and ASES score (P = .0228) in favor of the RS group. There were no other notable differences between groups. The most common complications were aseptic humeral stem loosening (24% vs. 3%, P = .018) and periprosthetic instability (10% vs. 6%, P = .649) for the AS and RS cohorts, respectively. There was no statistically significant difference between surgical revision rates between the AS and RS cohorts (24% vs. 8%, respectively. P = .096).

Discussion

Diaphyseal press-fit modular humeral stem can provide a viable surgical alternative in compromised proximal humeral bone. At short-term follow-up, the clinical and radiographic outcomes are comparable to other stem designs. Further studies are necessary to identify risks and causes of failure associated with modular diaphyseal press-fit stems.