Factors Related to the Inconstancy of Sustentaculum Tali Fragments in Intra-Articular Calcaneus Fractures

CATEGORY: Trauma INTRODUCTION/PURPOSE: Since intra-articular fractures are common in calcaneus fractures, anatomical reduction is important. Several ligaments such as spring ligament and deltoid ligament are attached to the Sustentaculum tali (ST). It is known that ST fragment is constant in calcaneus fracture. However, few studies have been reported to prove this. Therefore, we studied to establish criteria for the inconstancy of ST fragments through the analysis of computed tomography (CT) of the unaffected calcaneus, to confirm the prevalence of ST fragment inconstancy by applying these criteria, and to analyze the factors related to the inconstancy of the ST fragment. METHODS: From 2012 to 2020, CT scans of calcaneus fractures of 122 patients (101 men and 21 women) were taken, and angulation and diastasis of ST fragment were measured in the semi-coronal plane. As a control, angulation and diastasis were measured in 62 unaffected calcaneus. After establishing criteria for the inconstancy of ST fragments, we evaluated the prevalence of ST fragment inconstancy. After, we analyzed related factors. Patient factors included age, BMI, smoking, and diabetes. Radiographic factors included the degree of comminution of the posterior facet, location of the outermost fracture line of the posterior facet, presence of an intra-articular fracture of the ST, and width of the ST fragment. RESULTS: The upper limit of the 95% CI of angulation and diastasis was 7.58° and 2.51 mm, respectively. Based on these criteria, the inconstancy of the ST fragment was observed in 34.5%. The width of the ST fragment was significantly smaller in the inconstant group. Severe comminution of the posterior facet, intra-articular fracture of the ST, and diabetes were significantly higher in the inconstant group. The inconstancy of the ST fragment was significantly associated with the width of the ST fragment (p < 0.001) (Table 1). Cut-off values for the inconstancy of the ST fragment were 20.5 mm for the width of the ST fragment. CONCLUSION: In intra-articular calcaneal fractures, ST fragment inconstancy was observed in 34.5%. The width of the ST fragment was significantly associated with the inconstancy of the ST fragment.