Welcome to this audio poster on the CT analysis of the posterior medial neurovascular bundle in patients with end-stage ankle arthritis for planning of total ankle replacement surgery by myself, Olivier Gauthier-Quon out of Kitchener, Ontario, Kimon Tomezos, Chris Brown and Peter Stavrou out of Adelaide, Australia. The posterior tibial neurovascular bundle is at risk with the bony cuts required for total ankle replacement. The primary aim of this study was to identify a reliable landmark that could potentially be used to identify the position of the neurovascular bundle during the tibial and tailor cuts as well as the distance from the posterior cortex to the bundle. A secondary goal was to assess whether the neurovascular bundle moved anteriorly with anterior subluxation of the talus. This is a retrospective CT imaging study. All patients that had a pre-op CT scan for patient-specific instrumentation prior to undergoing a primary total ankle replacement were included. The right medical proxy CT scan protocol was performed on all patients included. We used a medial gutter that you can see on this axial cut as a landmark given that this is a relatively easy landmark to see intraoperatively, especially if you're using a gutter fork and the medial gutter to guide your axial rotation. We hypothesized that this line would be a good indicator of where the neurovascular bundle is positioned posterior to the ankle. We then used this line to identify the distance between the medial gutter line and the closest distance to the tibial neurovascular bundle that you see here in pink. We also measured the closest distance between the bundle and the posterior cortex of the tibia or the talus respectively, again, shown here in pink. We completed these measurements at the levels of the typical bony cuts for our primary ankle replacement system. You can see here the cuts are at 10 millimeters and 17 millimeters from the joint on the tibial side and 5 and 12 millimeters from the top of the talar dome on the talar side. The CT scans were reviewed independently by a foot and ankle surgeon and a foot and ankle fellow with a standard protocol at two separate occasions to also assess intra-observer and intra-observer reliability. In total, 168 measurements were taken in 42 ankle CT scans. Our third had anterior translation in the talus as is commonly seen in ankle arthritis. Here are our results. First look at the medial gutter line measurements. The results here show that the bundle is usually found within a centimeter lateral to the medial gutter line. Here positive measurements indicate that the bundle is lateral to the medial gutter line. The bundle is very rarely found medial to the medial gutter line. The results also show that the medial gutter line typically bisects the neurovascular bundle at the talar cuts level. The results also reveal that the bundle travels medially as it goes distally since the numbers are closing in on zero. If you follow the yellow dot, you can see that the bundle is traveling towards our medial gutter line medially as we go more distal. Our results for the measurements from the posterior cortex reveal that the bundle is closest and most at risk with the tibial cuts. It also shows that the bundle is further away with a five millimeter resection height than a 12 millimeter talar resection height as we would expect from the natural dome of the talus. This is a nice visualization of the position of the bundle as well as how far away it is from both the medial gutter line and the posterior cortex of the tibia. This heat map is at 10 millimeters above the level of the joint, which was found to be the level with the highest risk of injury. It shows that the bundle is almost never medial to the medial gutter line at this level. The bundle is less than five millimeters from the posterior cortex almost 50% of the time and less than one centimeter in nearly all of our measurements. Our results looking at anterior subluxation reveal that anterior subluxation of the talus did not show any statistically significant differences in the position of the neurovascular bundle when compared to a congruent joint. Inter-observer reliability was found to be fair to good and intra-observer reliability was found to be good. To conclude, the medial gutter provides an intraoperative landmark that may be used to help safely perform bony resections in total ankle arthroplasty. The study suggests that there is not an increased risk of iatrogenic injury during the boner sections in patients with end-stage ankle arthritis and anterior subluxation of the talus. Thank you and have a nice week.

CT analysis

posterior medial neurovascular bundle

ankle arthritis

total ankle replacement surgery

reliable landmark