Trochanteric Hip Fractures Clinical Outcomes and the Cut-out Complication

Sammanfattning: The established treatment for trochanteric hip fractures is internal fixation, either intramedullary (nail) or extramedullary (plate). Approximately 10% of these patients suffer from mechanical complications, the most frequent one being perforation of the lag screw through the femoral head into the hip joint (cut-out). This condition is painful and disabling, and requires revision surgery. The purpose of this thesis was to gain better understanding of the cut-out complication. The complication rate was evaluated in the retrospective series of 3066 consecutive patients treated with an intramedullary nail in a single centre over a 12 years period. Cut-out was found to be the most frequent complication albeit lower than in previous literature - 1.85% (57 patients) (Studies I and II). Combination of three factors: a comminute fracture, poor fracture reduction and non-optimal implant positioning was associated with an increased cutout risk. From the range of cut-out patterns, i.e. screw cut-out in a variety of paths through the femoral head, it was observed to be a three-dimensional event. To further analyse the pre-cut-out movements, Radiostereometric Analysis (RSA) method was applied in trochanteric hip fractures treated with intramedullary nails (Studies III and IV). Firstly, an experimental study was undertaken to confirm the applicability of RSA in trochanteric fractures. A SawbonesTM model of a trochanteric fracture was mounted on micrometer screws, and radiographed with different true reference displacements. RSA was shown to have high precision and accuracy in this application as translations and rotations in the fracture-implant model could be detected to within ±0.14mm and ±0.03mm (translations), and ±0.5° and ±0.18° (rotations). The last study prospectively evaluated the 3D fracture-implant movements with the RSA method in 20 patients with stable trochanteric fractures treated with an intramedullary nail and followed for one year. Fracture-implant motion decreased after 3 months and no cut-out occurred. RSA detected clinically relevant movements: translation of the proximal tip of the lag screw in the femoral head, femoral head and lag screw movements relative to the nail. It is important to recognize the "fracture at risk" and, particularly in these patients, achieve anatomical fracture reduction and optimal implant placement. The migration of the implant in bone measured by RSA could be used as a cut-out predictor and enable evaluation of new treatment methods in small groups of patients.