Abstract
BackgroundSoft tissue tension is treated as a crucial factor influencing the post-THA dislocation. The femoral offset is regarded as one of the major parameters responsible for the stabilization of the prosthesis. It is unclear which soft tissue is mostly affected by the offset changes.MethodsA finite element model of the hip was created. The model comprised muscles, bones, a stem, the acetabular component and a liner. The muscles were modelled as a Hill-type musculo-tendon nonlinear springs. Nonlinear analyses of the hip flexion and internal rotation were performed for the two values of the femoral stem offset.ResultsWe observed that the quadratus femoris and gluteus medius produce the largest resisting moment opposing the external load excreted by the surgeon during the intraoperative hip dislocation test.ConclusionsAn increased femoral offset increases the stretching of the quadratus femoris muscle significantly and provides the growth of its initial passive force. This muscle serves as a stiff band, providing stabilisation of the hip prosthesis, measured during the simulated intraoperative test.
Highlights
Total hip arthroplasty (THA) is the most successful and cost-effective procedure for patients with end-stage hip arthritis [1]
We observed that the quadratus femoris and gluteus medius produce the largest resisting moment opposing the external load excreted by the surgeon during the intraoperative hip dislocation test
An increased femoral offset increases the stretching of the quadratus femoris muscle significantly and provides the growth of its initial passive force
Summary
Total hip arthroplasty (THA) is the most successful and cost-effective procedure for patients with end-stage hip arthritis [1]. Femoral offset influence on passive forces in THA aseptic loosening, fracture, leg length discrepancy and hip instability. Surgery-related factors include the following: surgical approach, component orientation, choice of implant, soft tissue repair, maintenance of the leg length and femoral offset [4,5,6]. Increasing the femoral offset has been shown to increase the range of motion, restore hip biomechanics, reduce the occurrence of impingement, increase the strength of the abductor muscles and maximize joint stability by tensioning the soft tissue [8, 9]. Inappropriate soft tissue tension is cited as a crucial factor for post-THA dislocation, few investigations have addressed this problem. Soft tissue tension is treated as a crucial factor influencing the post-THA dislocation.
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