Periprosthetic Ulna Fractures Following Aptis Distal Radioulnar Joint Arthroplasty: A Series of Four Cases.

PURPOSE: This case series presents four cases of periprosthetic ulna fractures following Aptis distal radioulnar joint (DRUJ) arthroplasty to elucidate clinical characteristics, contributing factors, management challenges, and short-term outcomes following this rare complication and to propose prevention and optimal treatment strategies.

METHODS

We conducted a retrospective review of 239 Aptis DRUJ prostheses implanted between 2012 and 2022 at a single institution. We identified four cases of periprosthetic ulna fractures and assessed demographics, surgical indications, time to fracture, mechanism of injury, radiographic findings, treatment modalities, associated complications, and outcomes.

RESULTS

The incidence of periprosthetic ulna fractures was 1.7%. All patients had prior surgery on the same extremity. Fractures occurred within 11 months of DRUJ arthroplasty, with varied mechanisms of injury, including one after a fall, another with heavy lifting, and the remaining two unprovoked. Postoperative radiographs revealed eccentric stem position and endosteal impingement in all cases. According to the Unified Classification System for periprosthetic fractures, three were classified as B1 type, and one was B2 type at diagnosis. Open reduction and internal fixation reliably achieved union at an average of 7 months with acceptable function.

CONCLUSION

Intraoperative technical pitfalls may contribute to periprosthetic ulna fractures during the early postoperative period. Consideration should also be given to anatomical variations and ulna shaft morphometry. Nonsurgical treatment yielded unsatisfactory results, whereas fractures without gross stem loosening treated with open reduction and internal fixation and autologous bone grafting resulted in reliable fracture union, suggesting a limited role for conservative treatment. Based on principles of periprosthetic fracture treatment in other locations, fractures with gross stem loosening may be best managed with implant exchange, with or without supplemental open reduction and internal fixation; however, more evidence is needed to guide the treatment of this rare complication of DRUJ arthroplasty.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.