[Periosteosynthesis subtrochanteric fractures after fixation of femoral neck fractures with cannulated screws].

Introduction: the objective of this study was to analyze the incidence and predisposing factors in subtrochanteric fractures on hips previously treated with cannulated screws after suffering a subcapital fracture, based on eight cases registered in the last 20 years.

Material and methods: this is a retrospective observational study on a series of patients with a diagnosis of subtrochanteric hip fracture, who have been treated in recent months for a subcapital fracture of the same hip by osteosynthesis with cannulated screws. The study period was 20 years (2000-2020).

Results: of the eight cases, five were women and three were men, with a mean age of 75.12 years (range 59-87 years). In all cases, the subtrochanteric fracture occurred within a year after the first fracture, the time elapsed between the two fractures was four months on average (range 1-9 months). Regarding the disposition of the cannulated screws, most of the 7/8 cases were in the shape of an upper vertex triangle, and only one case was in the shape of an inverted triangle or lower vertex. The entry point into the femoral external cortex was at the level of the lesser trochanter in six cases, and in two cases this entry was distal to the lesser trochanter.

Conclusion: in our experience, in the etiology of subtrochanteric fractures, the introduction of screws distal to the lesser trochanter, and the distribution of the screws in a triangular shape are the two main objective predisposing factors.