A large posterior fragment in pertrochanteric fractures - pathoanatomic and 3D CT study

Three-part pertrochanteric fractures with a large posterior fragment have been reported both in historical and recent 3D CT studies, however, without a detailed description.

From the collection of the Institute of Anatomy, the authors obtained 6 specimens of hip joints of individuals who had sustained a three-part pertrochanteric fracture with a large posterior fragment, and 7 patients with the same type of fracture were identified in a cohort of 56 patients with a trochanteric fracture documented by 3D CT reconstructions. The study focused on the anatomy of the posterior fragment, the courses of the fracture lines, the integrity of the medial cortex and the lateral trochanteric wall.

Two types of the posterior fragment were identified, the quadrangular and the triangular ones. Separation of either of them markedly weakened the lateral trochanteric wall, more specifically, one quarter to two-thirds of its lateral surface. The triangular fragment was associated with shear instability on the medial aspect of the proximal femur and was markedly displaced in 5 of 7 cases. Exact identification of the shape and size of the posterior fragment was impossible with the use of postinjury radiographs alone.

In agreement with historical and recent CT studies, the findings of this study confirm the existence of a three-part type of pertrochanteric fracture with a large posterior fragment, and provides its detailed description, including its relevance to clinical practice.