My name is Alan Shamrock. I'll be discussing the role of weight-bearing CT in diagnosing syndesmotic instability in the chronic setting. So here are disclosures of the study group. Personally, I do not have any. So it has been estimated that foot and ankle injuries represent a quarter of all athletic injuries seen on the sideline in the athletic training room or in the office. Of the specific subset of foot and ankle pathology, the syndesmosis injury of the high ankle sprain represents a rather large portion. The prompt diagnosis and treatment of these injuries is critical, as you know, that missed or neglected syndesmosis injuries can lead to pain, dysfunction, and incongruent mortis and put the athlete at risk for the development of early osteoarthritis. So some syndesmosis injuries are not necessarily subtle, but this is not what we typically see. Instead, we have an athlete that comes in eight months after an injury with persistent pain and x-rays that look like this. And the diagnosis of syndesmosis pathology relies on physical exam in combination with various imaging modalities, all of which have their own unique limitations. Because of these limitations, today's gold standard for the diagnosis of syndesmosis pathology remains ankle arthroscopy, which in and of itself is an invasive procedure with associated healthcare costs and potential patient morbidity. So weight-bearing CT represents a useful diagnostic tool that is a non-invasive modality to directly assess syndesmosis under a physiologic load, which also offers a free look at the contralateral ankle under that same physiologic load as a normal control. There are also software programs that allow you to quickly calculate syndesmosis areas as well as syndesmosis volumes. So in 2019, the group at MGH reported on the utility weight-bearing CT to diagnose syndesmosis instability in the acute setting. They reported on 12 patients with unilateral instability. What they found was that the injured ankles had significantly increased syndesmosis areas compared to the non-injured side. Same cohort, similar study, but instead of looking at areas, they looked at volumes. And again, they found that injured ankles had increased syndesmosis volumes compared to the uninjured side. So what about chronic injuries? So there is currently a paucity in the literature on the role of weight-bearing CT in a chronic setting, so we sought out to prospectively evaluate the diagnostic accuracy of weight-bearing CT distance maps, area measurements, and volumetric measurements, detecting chronic, subtle syndesmotic instability. So we prospectively enrolled patients with suspected subtle chronic injuries, chronic being an injury more than six months prior, and subtle being a concerning physical exam with normal imaging including radiographic stresses. Patients were included if they had no hind foot malalignment as well as no ankle osteoarthritis. So all enrolled patients underwent a weight-bearing CT using the PET-CAT system prior to ankle arthroscopy. In the operating room, the syndesmosis was directly assessed and deemed unstable. If a three millimeter arthroscopic shaver could be inserted between the tibia and the fibula with the ankle at neutral or with a external rotation stress, the so-called drive-through sign. We used the BoneLogic software to calculate distance maps, syndesmosis areas, and syndesmosis volumes. This is a representative figure of syndesmosis distance maps which was used to calculate the distance areas one centimeter above the tibial plafond. So we looked at syndesmosis volumes one centimeter, three centimeter, five centimeter volumes above the tibial plafond as well as medial lateral gutters. We used previously published threshold values of abnormal syndesmosis areas and syndesmosis volumes. So using these threshold values in combination with arthroscopy findings, we calculated diagnostic accuracy of weight-bearing CT. So what did we find? So 11 patients were enrolled of which nine had confirmed instability in the operating room. Comparing injured ankles to the uninjured side, regardless of their threshold values, their increased areas of one centimeter above the plafond as well as volumes one and three centimeter above the tibial plafond. No difference in five centimeter volumes or lateral gutter volumes. So looking at the weight-bearing CT area measurements, there is a 36% diagnostic accuracy. When looking at volumes, there is a slightly improved yet still poor 45% accuracy. So when compared to the uninjured side, syndesmosis area and volumetric measurements were significantly increased in ankles with a chronic rotational injury. In terms of diagnostic accuracy, weight-bearing CT performed surprisingly poor and did not perform as well as in previous studies examining acute injuries. To highlight this, this is a paper out of MGH again. Same methodologies, the study we're talking about. And what they found was that looking at area measurements, their diagnostic accuracy was 75% and with their volumes, ranged between 80 and 90% compared to our 36 and 45%. So we noted large variations and ranges in all assessed measurements consistent with our relatively small sample size and believe that increasing the sample size as well as introducing an external rotation stress could potentially optimize its diagnostic capability in the chronic setting as an area of future study. Thank you.

weight-bearing CT

syndesmotic instability

chronic setting

diagnostic accuracy

ankle arthroscopy