SLR - November 2019 - Brian Schenavar
Reference: Gibson P., Ippolito J., Hwang J., Didesch J., Koury K., Reilly M., Adams M., Sirkin M. Physiologic Widening of the Medial Clear Space: What’s Normal? Journal of Clinical Orthopaedics and Trauma. 10(2019) S62-S64Scientific Literature Review
Reviewed By: Brian Schenavar, DPM
Residency Program: Ascension Wisconsin – Milwaukee, WI
Podiatric Relevance: Ankle trauma is a common entity of podiatry pathology. In regard to fractures of the ankle, the instability of the soft tissue structures have received increased attention in the recent literature, specifically, involvement of the medial clear space. Insufficiency of the deep deltoid ligament is responsible for radiographic findings of lateral shift and excessive external rotation of the talus. The purpose of this article focused on uninjured ankles and the clear space that was recorded after external stress. The authors hypothesized that the medial clear space will be less than 5mm and the lateral talar shift would be less 2mm of baseline. This may be quite useful to understand the threshold of a healthy uninjured ankle as it compares to a fractured and unstable ankle.
Methods: This study prospectively enrolled patients that were undergoing open reduction internal fixation of an ankle. Manual external rotation stress images of the uninjured ankle was then performed under anesthesia and fluoroscopic measurements were performed. Exclusion criteria involved previous injury, known instability, poly-trauma, <18 years of age or incidental radiographic abnormalities. Three reviewers were used to review blinded serial fluoroscopy images of stressed and unstressed uninjured ankles. Additional measurements were taken including tib-fib clear-space, tib-fib overlap, talar tilt and stressed and unstressed lateral talar shift.
Results: Fifteen patients met the criteria in this study. Average age was noted to be 42 years old and a 2:1 male to female ratio. No statistical significance was noted between stressed and non-stressed fluoroscopic views. The mean medial non-stressed clear space was noted to be 3.1mm with only a difference of 0.10mm when stressed. There was a 0.51mm mean difference of the lateral talar shift between stressed and unstressed images. Throughout the fluoroscopic inter-rater reliability was noted to be excellent.
Conclusions: This research is important because it helps rule out instability in the injured patient. The results support current literature thresholds of >5mm and >2mm of medial clear space widening and lateral talar shift respectively. These values coincide with instability and disruption of the deep deltoid ligament. The results of this study do indeed support low false positives for ankle instability in an injured patient. Moreover, it values the importance of radiographic attention in ankle instability for stressed and unstressed radiographs after injury.