The anatomy of the anterior inferior tibiofibular ligament and its relationship with the Wagstaffe fracture.

BACKGROUND: Our aim in this study was to identify the fibular footprint of the Anterior Inferior Tibiofibular Ligament (AITFL) and its relation to Wagstaffe fracture fragment size. METHODS: We examined 25 cadaveric lower limbs which were carefully dissected to identify the lateral ankle ligaments. The AITFL anatomy was compared to 40 Wagstaffe fractures identified from our ankle fracture database. RESULTS: The AITFL origin was from the anterior fibular tubercle with an average length of 21.61 mm (95% CI 20.22, 22.99). The average distance of the distal aspect of the AITFL footprint to the distal fibula margin was 11.60 mm (95% CI 10.49, 12.71). In the ankle fractures analyzed, the average length of the Wagstaffe fragment was 17.88 mm (95% CI 16.21, 19.54). The average distance from the distal tip of the fibula to the Wagstaffe fracture fragment was 21.40 mm (95% CI 19.78, 23.01). In total there were 22 syndesmosis injuries. There was no statistical difference in Wagstaffe fragment size between stable and unstable groups. CONCLUSION: The AITFL fibular origin was both larger and more distal than the Wagstaffe fracture fragments seen in our institution. Therefore, this suggests that a ligamentous failure will also have to occur to result in syndesmotic instability. The size of fracture fragment also did not confer to syndesmotic instability on testing. Level of Evidence - 3.

Posterior approaches to the ankle - an analysis of 3 approaches for access to the posterior malleolar fracture.

BACKGROUND: An anatomical study to determine what degree of access to the posterior distal tibia could be gained by using 3 different approaches; the posterolateral, the posteromedial and the medial posteromedial approaches. METHODS: A comparison study, between the anatomical dissection of 7 fresh frozen cadaveric lower legs and image analysis of CT data of posterior malleolar fractures from a prospectively collected database was conducted. All fractures have been classified using the Mason and Molloy classification. RESULTS: In comparing the posterior malleolar fracture fragment width to distal tibia width, the posterolateral fragment encompasses 60.1% (95% CI 56.8, 63.3) of the total width of the tibia. If the posteromedial fragment is included the fragments encompass the entire distal tibia (100%). In type 3 fractures, 81.4% (95% CI 75.5, 87.1) of the distal tibia width is involved. When comparing the fracture width to the approach, no approach achieves a complete exposure of the type 2B or 3 fracture patterns. The overall surface area of the type 2B and 3 fractures, is significantly greater than all the approaches. Considering the lateral to medial extent of the fracture, the posterolateral fragment mean width is 33% greater than what can be exposed by the posterolateral approach (mean 24.9 vs 16.8mm). In type 2B and 3 fractures, the horizontal exposure reduces to 39.8% and 47.6% respectively. In comparison, the PM approach exposes 47.6% of the type 2B fracture pattern and 57.1% of the type 3 fracture pattern and allows a preferable angle for hardware insertion. The MPM approach does not expose any of the posterolateral fragments in this study, however it does expose 92% (mean 21.9 vs. 23.8mm) of the medial to lateral width of a posteromedial fragment of a type 2B fracture. CONCLUSION: Each approach allows access to different parts and amounts of the posterior tibia. An understanding of and utilisation of these approaches can lead to adequate exposure for fixation of most posterior malleolus fracture patterns seen.

Anatomy of the Insertion of the Posterior Inferior Tibiofibular Ligament and the Posterior Malleolar Fracture.

BACKGROUND: Our aim in this study was to identify the extent of the posterior inferior tibiofibular ligament (PITFL) insertion on the posterior tibia and its relation to intra-articular posterior malleolar fractures. METHODS: Careful dissection was undertaken on 10 cadaveric lower limbs to identify the ligamentous structures on the posterior aspect of the ankle. The ligamentous anatomy was further compared with our ankle fracture database, specifically posterior malleolar fracture patterns, demonstrating a rotational pilon etiology (Mason and Molloy type 2A and B). Computed tomography imaging was used to measure the dimensions of the fracture fragments. RESULTS: The superficial PITFL was found to have a transverse component and an oblique component. The average size of the tibial insertion was 54.9 mm (95% CI, 51.8, 58.0) from joint line and 47.1 mm (95% CI, 43.0, 51.2) transverse. From our database of ankle fractures involving the posterior malleolus, 80 Mason and Molloy type 2 fractures were identified for analysis. Of these, 33 were type 2A and 47 were type 2B. The posterolateral fragments had an average size of 26.3 mm (95% CI, 25.0, 27.7) height and 22.1 mm (95% CI, 21.1, 23.1) width. The posteromedial fragments had an average size of 22.0 (95% CI, 18.9, 25.1) height and 19.8 (95% CI, 17.5, 22.0) width. CONCLUSION: The superficial PITFL insertion on the tibia is broad. In comparison with the average size of the posterior malleolar fragments, the PITFL insertion is significantly larger. Therefore, for a posterior malleolar fracture to cause posterior syndesmotic instability, a ligamentous injury must also occur. CLINICAL RELEVANCE: Posterior syndesmotic instability results from injury to the PITFL. It has been widely reported that a posterior malleolar fracture will also give rise to posterior syndesmotic instability due to the insertion of the deep PITFL on the posterior tibia. On the contrary, in this paper, we have shown that the superficial PITFL insertion on the tibia is very large, much greater than the average size of the posterior malleolar fragments. Therefore, for a posterior malleolar fracture to cause posterior syndesmotic instability, a ligamentous injury will also have to occur.