IMAGE-GUIDED OSTEOCHONDRAL AUTOLOGOUS AUTOGRAFTING OF THE ANKLE

Introduction Osteochondral autologous autograft (also called mosaic arthroplasty) is the preferred treatment method for very large osteochondral defects in the ankle. For long-term success of this procedure, the transplanted plugs should reconstruct the curvature of the articular surface. The different curvatures between femoral-patella joint and the dome of the talus makes the reconstruction difficult and requires lots of experience. Material Prior to the surgery a CT arthrogram of the ankle, as well as a CT of the knee were obtained and 3D bone models for the knee, the ankle as well as a model for the ankle cartilage were created. Using custom-made software a set of osteochondral grafts (“plugs”) positioned over the defect site were planned and an optimal harvest location for each plug was chosen. Intraoperatively, an optoelectronic navigation system was installed and sensors were attached to femur, talus, and conventional harvest and delivery chisels. A combined pair-point and surface matching was performed to register femur and talus. For each planned plug the surgeon positioned, oriented, and rotated the harvest and delivery chisels with respect to preoperative plan by using the visual and numerical feedback of the system. Results We performed the above described procedure on a 37 year old female patient with osteochondral injury of the dome of the right talus with an approximate size of 20mm × 9mm. One 8mm and two 6mm plugs were planned and intraoperative navigated. At 6 months postoperative she had a significant improvement in her passive range of motion from 0–15° dorsi-flexion and 0–60° plantar-flexion, compared to her uninjured ankle of 0–15° dorsi-flexion and 0–80° plantar-flexion. The inversion and eversion of the ankle are normal and x-ray evaluation showed good and complete integration of the osteochrondal plugs. Discussion A virtual preoperative planning tool helped to solve the complex geometrical problem of reconstructing the articular cartilage surface of the talus using multiple autologous osteochondral plugs from the knee. The intraoperative optoelectronic guidance allowed the surgeon to transfer this plan into the intraoperative situation.