Loss of offset after pertrochanteric hip fractures affects hip function one year after surgery with a short intramedullary nail. A prospective cohort study.

Purpose: We hypothesised that protruding collum screws in intramedullary nails used for pertrochanteric fractures cause lateral pain/discomfort and that loss of offset relates to poorer hip function.
Methods: Seventy-six patients with an acute pertrochanteric femoral fracture AO types A1 and A2 were operated upon using a short intramedullary nail and were included in a prospective observational cohort study and followed-up for one year. The main outcome variables were lateral pain and hip function as evaluated with the Harris Hip Score. The main exposure was compression along the collum screw and lateral protrusion measured by anteroposterior X-ray images. Perioperative images were compared to images at the follow-up visit. Outcome variables were adjusted in regression models for reduction, fracture type, body mass index, sex and age.
Results: A total of 28 (36 %) patients experienced lateral pain at one year. We found a correlation between lateral protrusion and lateral pain, adjusted OR 4.5 per protruding centimetre (95 % CI, 1.1-17.5). Collum compression correlated with a poorer outcome with Harris Hip Score -14.2 per compressed centimetre (95 % CI, -21.8 to -6.7).
Conclusions: In patients with type A1 and A2 pertrochanteric fractures operated on using intramedullary nailing, a large compression and lateral protrusion of the collum screw are associated with poorer hip function and lateral pain. New technical improvements for implants should focus on these factors to improve functional outcome after surgery.