Superior Tuber Displacement in Intra-Articular Calcaneus Fractures

Category: Ankle Introduction/Purpose: Intra-articular calcaneus fractures typically result in a classic deformity which includes heel shortening, heel widening, varus malalignment and loss of height from depression of the posterior facet. When requiring operative management, correction of these various deformities is important and has been correlated with outcomes. However, little has been written regarding superior displacement of the calcaneal tuber. This previously undescribed deformity warrants consideration when treating calcaneus fractures as various studies have demonstrated functional weakness resulting from a shortened triceps surae mechanism. This investigation sought to determine the amount of tuber elevation seen in intra-articular calcaneus fractures as compared to normal uninjured calcanei. Furthermore, we propose two new measurements, the talo-tuber angle and talo-tuber distance, which aid in quantifying displacement and may aid in the surgical management of calcaneus fractures. Methods: Lateral radiographs of normal uninjured calcanei in 220 consecutive patients who met our criteria were examined. Radiographs demonstrating significant obliquity, previous bony injury or subtalar arthrosis were excluded. Two novel measurements were utilized to establish normative data for calcaneal tuber positioning. Two lines are drawn from the superior most portion of the talar head, one tangential to the talar dome and the other to the superior most portion of the calcaneal tuberosity. The angle subtended by these lines is termed the talo-tuber angle and the distance between these two lines at the level of superior most portion of calcaneal tuberosity measured as a perpendicular is termed the talo-tuber distance. Lateral radiographs of 50 consecutive calcaneus fractures treated operatively were examined and the same measurements were obtained before and after surgery to determine the amount of superior tuber elevation seen in patients sustaining intra-articular calcaneus fractures. Results: Normative data demonstrated a mean of 38.6 degrees (range: 26.2 to 58.44, SD=4.28) when utilizing the talo-tuber angle and 54.46 millimeters (range: 36.15 to 72.57, SD=7.30) when utilizing the talo-tuber distance (Figure 1) in normal uninjured calcanei. Patients sustaining intra-articular calcaneus fractures demonstrated a mean of 29.54 degrees (range: 20 to 46.4, SD=5.86) for the talo-tuber angle and 39.01 millimeters (range: 24.02 to 62.9, SD=9.41) for talo-tuber distance (Figure 2). These values changed to a mean of 37 degrees (range: 26.4 to 50, SD=5.18) for the talo-tuber angle and 51.76 millimeters (range: 33.18 to 75.65, SD=8.62) for talo-tuber distance after surgery (Figure 3). There was a statistically significant difference (P value < .00001) for both talo-tuber angle and distance between normal calcanei and fractured ones. There was no significant differences between normal calcanei and those treated surgically in these two measurements. Conclusion: Superior displacement of the calcaneal tuber is an additional deformity seen in intra-articular calcaneus fractures that has been poorly described in the literature. Given that functional weakness can occur with a shortened triceps surae mechanism, increased awareness and correction at the time of surgery is warranted. We propose two novel measurements with associated normative data that may aid surgeons in quantifying this deformity and assessing anatomic reduction.