The Use of a Novel On-bone Femoral Spacer Molding Device for Reducing Femoral Spacer Complications in Periprosthetic Total Knee Infection: Preliminary Results.

Background: The complications of mobile cement spacer are common. To address these issues, a novel on-bone femoral molding device (FMD) has been developed to enhance stability between the spacer-bone. This study investigated the clinical outcomes and complications associated with this novel FMD.

Methods: The FMD was developed using a reverse engineering program with the on-bone molding concept. Five knees of 4 patients were examined. The bone status, ambulatory ability, knee range of motion, and femoral spacer complications were followed up until 3 months after the second-stage surgery.

Results: The infection was successfully treated in all patients. The interim period was 21.6 ± 4.5 weeks. The range of motion measured before the first surgery, before the second surgery, and 3 months after the second surgery was 104.2 ± 43.1, 105.8 ± 20.0, and 124.0 ± 18.5 degrees, respectively. No femoral spacer complications were observed. One knee joint subluxation and 1 minor tibial spacer fracture occurred.

Conclusions: Newly developed FMD appears safe during initial proof-of-concept in patients with stage 1 to 2B bone loss. It prevents femoral spacer complications in a specific bone defect type without causing additional bone loss and facilitates range of motion during the interim period. Precise gap assessment and appropriate tibial cement spacer thickness could prevent knee dislocation.