Implant Survivorship and Functional Recovery Utilizing a Modern Knee Fusion Nail Spacer for Periprosthetic Joint...

Traditional indications for static spacers include substantial bone loss, ligamentous insufficiency, extensor mechanism dysfunction, or severe soft-tissue compromise. However, conventional designs are associated with high complication rates and morbidity. A knee fusion nail spacer (FNS) construct combines mechanical stability with targeted antibiotic delivery. This study aimed to (1) describe outcomes of FNS use in terms of total knee arthroplasty (TKA) reimplantation, infection eradication, and limb salvage; (2) determine FNS survivorship with reinfection as the endpoint; and (3) report complications and functional recovery.

This retrospective multicenter study reviewed chart and radiographic data from 63 patients treated between 2017 and 2023. The primary outcome was implant survivorship with reimplantation as the endpoint. Secondary outcomes included spacer- or wound-related complications, venous thromboembolisms, acute kidney injuries, functional recovery, and reinfections. Kaplan-Meier analyses assessed implant survivorship, and univariate Cox regression identified predictors of implant failure.

Successful reimplantation was achieved in 60.3% of patients. Of the remainder, 28.6% retained their FNS and 9.5% underwent unplanned reoperations. Reinfection was identified in 16% with three with FNS and seven following reimplantation. The mean follow-up period was 22.4 months (range, zero to 84). There were no cases of implant mechanical failure. Radiographic implant loosening was observed in 9.4% of patients, and three (4.8%) patients experienced periprosthetic fracture. The mean knee range of motion post-reimplantation was 3.6 degrees of extension (range, -5 to 48) and 87.6 degrees of flexion (range, 10 to 125).

The modular FNS demonstrates favorable survivorship, acceptable reinfection rates, and low mechanical complication rates in patients who have chronic knee PJI, many of whom present with severe bone loss, soft-tissue compromise, and instability. The FNS offers a safe and durable option for infection control and limb salvage in a population with limited reconstructive alternatives.