Management of shoulder prosthetic joint infections with humeral bone loss using a customizable articulating long stem spacer (The Frankenspacer).

Background: With an increasing number of shoulder arthroplasties being performed, prosthetic joint infection (PJI) of the shoulder and proximal humeral bone loss (PHBL) remain challenging complications for surgeons to manage. While various strategies exist for managing patients with shoulder PJI or PHBL, there is limited information regarding treatment options and outcomes in patients with combined PJI and PHBL. The purpose of this study is to describe a novel technique for treatment of this unique patient population along with its risk of complications and reinfection in patients undergoing staged revision shoulder arthroplasty. Methods: This retrospective case series included 18 shoulders treated by three surgeons at a single institution between 2019 and 2023 who underwent revision for suspected PJI with PHBL noted preoperatively or at the time of surgery. Patients underwent placement of a custom, long stem antibiotic cement spacer using a prefabricated humeral head mated to a cannulated humeral nail using a large threaded pin. Patient demographics, reinfection rates, and radiographic complications were collected. Results: The mean age at the time of spacer placement was 63.6 ± 7.4 years, with an average follow-up of 22.8 ± 16.0 months. PHBL was identified in all patients with an average of 54.6 ± 30.9 mm on postoperative full length arm radiographs compared to contralateral humerus. Proximal Humeral Arthroplasty Revision Osseous inSufficiency (PHAROS) classification of PHBL revealed 5 (27.8%) type 1, 8 (44.4%) type 2, and 5 (27.8%) type 3 bone loss. Fourteen (78%) shoulders underwent a second stage revision to a reverse shoulder arthroplasty and an allograft-prosthetic construct was used in 11 of the patients in this group. Reinfection occurred in 3 (21.4%) shoulders that underwent 2-stage revision and a 16.7% recurrence rate overall. Other complications included spacer glenohumeral dislocation (56%), glenoid erosion (83%), and spacer loosening (11%). There were no fractures of the long stem spacer. Rate of dislocation was noted in 20% of shoulders with PHAROS 1 grade and in 69% of those with PHAROS 2 or 3 grades (P = .057). Conclusion: Long-stem custom spacer placement using a prefabricated humeral head combined with a humeral nail (The Frankenspacer) for shoulder PJI and PHBL results in acceptable reinfection rates for patients undergoing a 2-stage revision. Glenohumeral dislocation and glenoid erosion are common. Dislocation increases with severity of PHBL. This technique is a reasonable treatment option for managing this complex patient population.