Aim: To investigate the radiographic anatomical characters of the bones in the fractured calcaneus by using tangential X-rays.
Methods: Fifty-seven patients (114 sides) with normal calcaneus and thirty patients (42 sides) with fractured calcaneus were radiographed along the line connecting the midpoint of the 4th and 5th metatarsal heads with the lateral margin of the corpus calcanei. The anatomical characters of the calcaneus on the tangential X-ray views were analysed, including radius and fractal geometry.
Results: On a tangential X-ray view of the fractured calcaneus, the projection of sustentaculum tali resembled a duck beak, which was just under the middle facet of the talocalcaneal joint. The corpus calcanei appeared oval, which was just under the talocalcaneal joint articular surface. The lateral calcaneal wall did not exceed the vertical line extending from medial of the lateral malleolar fossa (the Z-W line). From the scan picture, the fractured calcaneus seemed to be widened as its lateral wall crossed the Z-W line. The longitudinal axis of this oval-shaped projection was 3.52 ± 0.41 cm (a), the horizontal axis was 2.56 ± 0.28 cm (b), and the a/b ratio was 1.40 ± 0.11. In the normal calcaneus, the a/b ratio is higher than 1.40 and the differences of the values in these two groups were significant. Therefore, the a/b ratio of the calcaneal oval-shaped projection can be used to evaluate the degree of its deformity after fracture.
Conclusion: These results demonstrated that the tangential X-ray view of the calcaneus can be used to evaluate its radiographic anatomy and to measure the radii of the oval-shaped corpus calcanei.