| dc.description.abstract | 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. | sv |
