Abstract
Objective To investigate the effect of a self-designed hollow-bone-graft dynamic hip screw on fracture healing in a pig model of femoral neck fracture.Methods We designed novel dynamic hip screws of titanium alloy which are hollow and have flabellum-like and round openings between screw threads.Sixteen healthy pigs (half males and half females,mean age of 3.5 months and mean body mass of 25.1 kg) were used to create models of bilateral femoral neck fractures.The left femurs were fixated with hollow-bone-graft dynamic hip screws as the experimental group,and the right femurs were fixated with conventional dynamic hip screws as the control group.At 4,8,12 and 16 weeks after surgery,the animals received X-ray and CT examinations and 4 animals were sacrificed each time to harvest both femurs for biomechanical test (4,8,12 weeks postoperation) or gross observation of fracture healing (16 weeks postoperation).The axial bending and torsional stiffness were assessed in the biomechanical test.Results The X-ray and CT examinations showed:at 4 weeks,the fracture lines were partially blurred and new bone grew evenly in the experimental group but the fracture lines were still clear in the control group; at 16 weeks,the bone density around the fracture line was similar to that of normal bone tissue and no punctiform dense hyperplasia was observed on the smooth surface of the femoral head in the experimental group while increased bone density at the fracture line and limited bone resorption and bone trabecula assimilation were observed in the control group.At 8,12,16 weeks after surgery.the experimental group had significantly higher Lane-Sandhu scores than the control group P ＜ 0.05).At 4,8,12 weeks postoperation,the experimental group had significantly greater stiffness against compression,bending and torsion than the control group(P ＜ 0.05).Gross observation at 16 weeks showed fine healing of the fracture ends in the experimental group but bony connection of the fracture ends in the control group.Conclusions Since the novel hollow-bone-graft dynamic hip screws can not only provide rigid internal fixation but also facilitate autogenous bone infusion at the fracture site,they promote early union of the fracture in an animal model.This experiment provides evidence for the clinical application of these screws. Key words: Femoral neck fractures; Fracture healing; Bone nails; Animal experimentation
Published Version
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