The influence of prosthesis stem design on femoral neck fracture by using finite element analysis

Abstract

Objective To investigate the influence of prosthesis metaphyseal stem design on femoral neck fracture with a range of implant orientations. Methods A finite element model of the hip resurfacing arthroplasty was reconstructed on the basis of data of a normal femur(from a 63-year-old male)and a 50 mm birmingham hip resurfacing(BHR)prosthesis.And this modeling was used to indicate the effects of prosthesis metaphyseal stem design on femoral neck fracture with a given load of 0-6 k N, with a range of varus-valgus implant orientations. Results The analysis suggested that the intact femoral neck strength could be maintained across a wider range of varusvalgus orientations for short-stemmed and stemless prostheses.The model predicted that the damage initiation load would be decreased by approximately 20% with varus implant orientation and 10% in neutral orientation.Compared with the stemmed, traditional-design prosthesis, the short-stemmed and stemless designs had less weakening effect upon the femoral neck.For the stemless design in all orientations, the femoral neck strength was predicted to be within 5% of that for the intact bone, and the strength with the short-stemmed design was within 3% of the intact case. Conclusion The study suggests that a short-stemmed resurfacing head offers improved tolerance to misalignment over traditional designs.While femoral neck fractures are multifactorial, biomechanical factors are of clear importance to the clinical outcome, so this may reduce the risk for patients at the edge of the indications for hip resurfacing. Key words: Hip resurfacing; Neck fracture; Prosthesis