A Rare Case of Isolated Talus Osteomyelitis, Salvaged with Custom-made 3D Printed Antibiotic-impregnated Bone Cement

Background:
Chronic Osteomyelitis is a challenging orthopedic condition. Biofilm development and avascular necrosis of the bone render systemic antibiotics ineffective. Debridement of necrotic tissue with highly concentrated locally delivered antibiotics in the form of antibiotic-impregnated bone cement is the gold standard of treatment. In this case, an overweight 56-year-old male presented to the emergency department with chronic right ankle pain lasting for three months. The patient was partially treated with oral antibiotics in an outside hospital for presumed cellulitis. Diagnostic arthrocentesis from his ankle yielded less than 1cc of fluid that yielded methicillin-sensitive staph aureus. A CT scan revealed signs of isolated chronic osteomyelitis of the talus. The first surgical debridement included a bone biopsy that confirmed the diagnosis. We initiated six weeks of IV antibiotics. At three months postoperatively, the patient presented with local signs of infections. A new CT scan demonstrated progression in the severity of the talar osteomyelitis, represented by enlarged diffuse cysts. The plan at this point was to perform a total talectomy and replace it with a custom-made 3D printed antibiotic-impregnated bone cement.

Methods:
A 3D mold was created based on the patient`s CT scan. We performed a 3D model conversion using D2P® software. We reduced the model size to 95% of its original size to facilitate the spacer insertion into the articular space. We then integrated four Kirschner wires into the model for reinforcement of the cement. We printed The final version of the mold in sterilization safe PA (Nylon) 12 material. Surgical Procedure: A standard anterior approach to the ankle joint was carried out. We excised the infected tissue and extracted the diseased talus. We then prepared the mold on a back table, injected it with cement antibiotics (vancomycin and gentamicin), and introduced four 1.4mm Kirschner wires in the designed grooves.

Results:
Postoperatively, we initiated treatment with IV cefazolin for six weeks and oral Cephalexin for six more weeks. The patient started weight-bearing in a CAM boot at two weeks postoperatively. At three months postoperatively, the patient reported going back to work and to daily activities. At six months postoperatively, the ankle range of motion was measured to 0-20 but was painless. The subtalar range of motion was minimal and painful. Weight-bearing Radiographs exhibited no signs of implant subsidence or subluxation. The CRP value was 0.45 mg\L.

Conclusion:
This case represents an innovative approach to treating rare single bone osteomyelitis with custom-made 3D printed antibiotic-impregnated bone cement. This novel approach is a step forward towards personalized treatments for complex osteomyelitis cases and prosthetic joint infections.