Lesser Trochanteric Fragments in Unstable Pertrochanteric Hip Fractures: A Morphological Study Using Three-Dimensional Computed Tomography (3-D CT) Reconstruction.

BACKGROUND The lesser trochanter (LT) posterior cortical extension (LTPE) fragment is important for joint stability during reconstruction in unstable pertrochanteric hip fractures. This study aimed to investigate the morphological characteristics of the LT fragments using three-dimensional computed tomography (3-D CT) reconstruction and to compare clinical outcomes in different subgroups of 31A2 fractures. MATERIAL AND METHODS A retrospective study included CT images of 58 cases of 31A2 type unstable pertrochanteric fractures, using the Arbeitsgemeinschaft für Osteosynthesefragen and Orthopedic Trauma Association (AO/OTA) classification. After 3-D CT reconstruction, all the displaced fragments were reduced and the morphologic parameters of the LT fragments were measured. RESULTS At the mid-level of the LT, the mean cortical extension of the LT fragment was 33.5 mm in the posterior wall (83%), 19.0 mm in the medial wall (53%). The mean distal cortical extension from the lower edge of the LT was 13.0 mm. The LT fragment occupied 38% of the whole cortical circumference. Comparison of the subgroups showed that the LT fragment of A2.3 had a larger cortical extension in the posterior, medial, and distal cortex. The mean fracture collapse was 4.7 mm in A2.2 fractures and 5.4 mm in A2.3 fractures (p=0.311). Despite the increased size of the LT fragment in subtype A2.3 fracture compared with subtype A2.2 fracture, this did not influence the clinical outcome. CONCLUSIONS The 3-D morphology of the LT fragment from CT imaging provided a better understanding of the characteristics of subgroups of unstable pertrochanteric fractures, which may improve and guide implant choice.