Prebending of Osteosynthesis Plates Versus Screw and Cerclage Fixation for Os Acromiale or Acromion Fracture; the 3D Technique and Mechanical Testing

Abstract

Three-dimensional applications are on the rise in medicine, mainly to make treatment more patient specific. This study compares the in vitro outcome parameters of 2 surgical techniques: hollow screws with cerclage fixation (HC) versus patient-specific plate osteosynthesis (PO). The techniques were tested on scapulae of 5 fresh-frozen cadavers as a treatment for symptomatic os acromiale or acromion fracture, to assess ultimate failure strength, stiffness, and fracture pattern. An existing osteosynthesis plate is preoperatively shaped by a printed 3-dimensional model of the acromion of the cadaver. The strength for the PO group [mean, 254.08±130.35 N (range, 118.12 to 404.19 N); P=0.10] was significantly different from the HC group [mean, 166.68±65.39 N (range, 91.02 to 226.34 N)]. There was no significant difference between stiffness of the PO group [mean, 13.38±4.99 N/mm (range, 7.02 to 19.22 N/mm); P>0.10] and stiffness of the HC group [mean, 10.22±6.26 N/mm (range, 6.73 to 21.38 N/mm)]. The fracture pattern of the HC is characterized by the screws ripping from the inferior bone cortex, whereas in the PO the posterior screws tear at the superior spine. From ultimate failure strength results can be concluded that patient-specific PO provides a stronger repair construct than cannulated screws and cerclage.