Abstract
In total hip arthroplasty, aseptic loosening and dislocation are associated with not being able to achieve the correct prosthetic component orientation. Femoral neck modularity has been proposed as a solution to this problem by allowing the surgeon to alter either the neck-shaft or version angle of the prosthetic femoral component intra-operatively. A single replicate full factorial design was used to evaluate how effective a modular femoral neck cementless stem was in restoring a healthy prosthetic range of motion in comparison with a leading fixed-neck cementless stem with the standard modular parameters. It was found that, if altered to a large enough degree, femoral neck modularity can increase the amount of prosthetic motion as well as alter its position to where it is required physiologically. However, there is a functional limit to the amount that can be corrected and there is a risk with regard to the surgeon having to select the optimum modular neck before any benefit is realised.Electronic supplementary materialThe online version of this article (doi:10.1007/s11517-014-1171-9) contains supplementary material, which is available to authorized users.
Highlights
During total hip arthroplasty (THA), being able to control the orientation of the prosthetic components is of critical importance in normalising the biomechanics of the hip [36, 54]
The systematic fractional replicate design to screen out independent variables which were not main factors in influencing the prosthetic impingement free range of motion found that in the non-modular group, femoral head offset (M 2.9 %, 1.0°), femoral neck offset (M 2.9 %, 1.0°) and femoral stem length (M 1.2 %, 1.0°) had the lowest contribution upon both the size of the prosthetic motion area and its position
There have been concerns with regard to their integrity which relate to the taper fitting of the femoral neck onto the femoral stem, potentially causing excessive fretting and crevice corrosion to the modular neck [1, 12]
Summary
During total hip arthroplasty (THA), being able to control the orientation of the prosthetic components is of critical importance in normalising the biomechanics of the hip [36, 54]. This requires having both a stable joint as well as achieving the ideal range of motion for a patient to fulfil their daily activities [8]. Failure to achieve these outcomes is linked to two of the most prominent reasons for revision surgery, aseptic loosening secondary to wear and dislocation which account for 45 and 15 % of revision cases, respectively [25]. Orienting the prosthetic components to maximise range of motion by increasing both acetabular cup inclination and the combined version of the acetabular cup and femoral stem
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