V 46 CT-guided robotically-assisted retrograde drilling of osteochondral lesions of the ankle joint

Abstract

Introduction Disadvantages of arthroscopically guided surgical techniques for treatment of osteochondral lesions (OCL) of the ankle joint are disruption of viable articular cartilage and insufficient addressing of the subchondral bone. For certain lesion locations, like the posteromedial talus, feasibility is often compromised. The INNOMOTION robotic assistance device proved its value for precise musculoskeletal interventions, such as facet joint and sacroiliac joint infiltrations. We present our first experience with CT-guided robotically-assisted retrograde drilling of osteochondral lesions of the ankle joint and evaluate its feasibility, precision and potential use as a routine operative treatment. Methods 8 patients diagnosed with OCL of the talus (4) and the distal tibia (4) were included. MRI revealed an intact cartilaginous cover in all cases. Surgery was performed with the INNOMOTION robotic assistance device (Innomedic, Herxheim, Germany) mounted on the table of a CT scanner. The robot-device was referenced to the coordinate system of the CT-scanner. Drill trajectory and depth were planned within acquired CT images. A guiding sleeve for the Kirschner-Wire (K-Wire) was attached to the holding device on the application module and positioned automatically according to the planned trajectory. A 2.5 mm K-Wire was advanced through the guiding-sleeve up to the calculated drilling depth. A cannulated drill was placed over the wire and advanced into the lesion. The lesion was curetted and filled with DBM-paste and patient spongiosa. CT-control scans were performed to determine the position of the instruments and to document the exact localization of the deposit. Results Technically successful CT-guided robot-assisted retrograde drilling was performed in all cases without intra- and postoperative complications. No intervention abort or conversion to arthroscopically guided technique or arthrotomy was necessary. CT-control scans confirmed exact initial placement of the guiding wire within the centre of the OCL, precise drill bit positioning and successful retrograde filling of the bored cavity. Discussion The first clinical cases demonstrated CT-guided robot-assisted intervention to be a feasible and safe method for retrograde drilling of OCL of the ankle. Precise assistance by the INNOMOTION-robot combined with the superior ability of the CT to visualize skeletal anatomy greatly improves the accuracy of drilling with exact and reliable addressing of OCL without damage to overlying cartilage. Further studies need to evaluate the outcome of this new operative technique and to compare it to conventional retrograde drilling.