Abstract
The most common implant options for the metacarpophalangeal joint arthroplasty include silicone, pyrocarbon and metal-polyethylene. A systematic review of outcomes of silicone and pyrocarbon implants was conducted; however, a similar exercise for metal-polyethylene implants revealed a scarcity of published results and lack of long-term follow-up studies. The aim of the present work is to test the hypothesis that the magnitude of metacarpophalangeal joint cyclic loads generates stress and strain behaviour, which leads to long-term reduced risk of metal-polyethylene component loosening. This study was performed using synthetic metacarpals and proximal phalanges to experimentally predict the cortex strain behaviour for both intact and implanted states. Finite element models were developed to assess the structural behaviour of cancellous-bone and metal-polyethylene components; these models were validated by comparing cortex strains predictions against the measurements. Cortex strains in the implanted metacarpophalangeal joint presented a significant reduction in relation to the intact joint; the exception was the dorsal side of the phalanx, which presents a significant strain increase. Cancellous-bone at proximal dorsal region of phalanx reveals a three to fourfold strain increase as compared to the intact condition. Interpretation The use of metal-polyethylene implant changes the strain behaviour of the metacarpophalangeal joint yielding the risk of cancellous-bone fatigue failure due to overload in proximal phalanx; this risk is more important than the risk of bone-resorption due to the strain-shielding effect. By limiting the loads magnitude over the joint after arthroplasty, it may contribute to the prevention of implant loosening.
Highlights
Arthritis in metacarpophalangeal (MCP) joint is relatively common, and it leads to disability, pain and disfigurement (Rizzo, 2011)
The metal-polyethylene SR MCP system (Stryker, MI, U.S.A.) attempts to re-establish the anatomic geometry of the metacarpal head, being suitable for use when either the patient is in need of a revision failed MCP prosthesis; or the patient expects to submit his/her hands to loading situations, which preclude the use of an alternative implant in the painful osteoarthritic and post traumatic arthritic MCP joint (Operative technique SR MCP System, 2016)
The hypothesis considered in this study is that the magnitude of MCP joint cyclic loads in daily hand functions generates stress, strain and initial stability behaviour, which yield reduced long-term risk of SR MCP system failure
Summary
Arthritis in metacarpophalangeal (MCP) joint is relatively common, and it leads to disability, pain and disfigurement (Rizzo, 2011). The hypothesis considered in this study is that the magnitude of MCP joint cyclic loads in daily hand functions generates stress, strain and initial stability behaviour, which yield reduced long-term risk of SR MCP system failure. The most common implant options for the metacarpophalangeal joint arthroplasty include silicone, pyrocarbon and metal-polyethylene. A systematic review of outcomes of silicone and pyrocarbon implants was conducted; a similar exercise for metal-polyethylene implants revealed a scarcity of published results and lack of long-term follow-up studies. The aim of the present work is to test the hypothesis that the magnitude of metacarpophalangeal joint cyclic loads generates stress and strain behaviour, which leads to long-term reduced risk of metal-polyethyle ne component loosening
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