Novel Transpatellar Tendon Retrograde Insertional Technique for Femoral Implant Placement in Rat Models

Objectives Prosthetic joint infection (PJI) is a serious complication affecting arthroplasty patients. The gold-standard treatment for PJI, two-stage revision, can fail in up to 30% of cases in patients undergoing total knee arthroplasty. Current rat models of PJI following total knee arthroplasty use a mainstream retrograde femoral nailing technique that significantly damages the quadriceps-patellar complex. We describe a novel method allowing retrograde intramedullary femoral nail insertion with minimal damage to the quadriceps-patellar complex. Methods Our technique was performed in 48 male Sprague-Dawley rats. After proper anesthesia, a 1 cm prepatellar skin incision was made, followed by a 2 mm transpatellar tendon incision. Using fluoroscopic guidance, a 1.2mm drill bit was advanced through the patellar defect and cortical bone and was used to ream the femoral canal. A 0.8 mm stainless steel Kirschner wire was inserted through the patellar defect into the femoral canal, leaving a 1mm segment protruding in the joint space. The defects in the patellar tendon and skin were closed with sutures. Results The mean surgical duration was 20.3 minutes. Among the 48 rats, 47 (98%) maintained articular capsule integrity on postoperative evaluation, as confirmed by an orthopedic surgeon under loupe magnification. All rats were ambulating postoperatively. Conclusion This novel technique offers an efficient, minimally invasive method of retrograde femoral nail fixation that preserves the integrity of the quadriceps-patellar complex and supports the further development of simulating prosthetic knee infection models in rats.