The Journal of hand surgery · 2018
Physiological Loading of the Coonrad/Morrey, Nexel, and Discovery Elbow Systems: Evaluation by Finite Element Analysis.
СтатьяНазвание и аннотация: Перевод в очереди
Обработка статьи · этапы, ошибки и управление
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King Elizabeth A, Favre Philippe, Eldemerdash Amin, Bischoff Jeffrey E, Palmer Mark, Lawton Jeffrey N
Аннотация
PURPOSE: Wear of polyethylene bearings represents a limiting factor in the long-term success of total elbow prostheses. Bearing stress is 1 factor contributing to accelerated wear. Physiological loading of total elbow prostheses and implant design influence upon bearing stresses have not been well described. This study evaluates bearing stresses in 3 commercially available implant designs under loads associated with daily living.
METHODS: Motion tracking from a healthy volunteer helped establish a musculoskeletal model to simulate flexor and extensor muscle activation at 0°, 45°, and 90° of shoulder abduction with a 2.3-kg weight in hand-forces and moments were measured at the elbow. Resulting physiological joint reaction forces and moments were applied to finite element models of 3 total elbow bearing designs (Coonrad/Morrey, Nexel, and Discovery) to evaluate contact area and polyethylene stresses.
RESULTS: Increasing shoulder abduction resulted in minimal changes to the elbow joint reaction force but greater joint moments. All implants showed greater peak stresses with increasing shoulder abduction-elbow varus. Discovery and Nexel achieved greater contact area (23% vs > 100%) and demonstrated up to 39% lower peak polyethylene stresses compared with the Coonrad/Morrey design.
CONCLUSIONS: Shoulder abduction results in a varus moment at the elbow. Newer bearing designs (Nexel and Discovery) provide a combination of higher contact area, improved load sharing, reduced edge loading, and lower stresses through elbow range of motion when compared with a cylindrical hinge-bearing design (Coonrad/Morrey).
CLINICAL RELEVANCE: Although the Coonrad/Morrey is a clinically successful prosthesis, our physiological loading model shows that Discovery and Nexel provide greater contact area, better load sharing and lower peak stresses. This may lead to a decrease in polyethylene wear rates and the eventual risks of osteolysis and aseptic loosening. Further studies are needed to determine how these findings translate clinically.
METHODS: Motion tracking from a healthy volunteer helped establish a musculoskeletal model to simulate flexor and extensor muscle activation at 0°, 45°, and 90° of shoulder abduction with a 2.3-kg weight in hand-forces and moments were measured at the elbow. Resulting physiological joint reaction forces and moments were applied to finite element models of 3 total elbow bearing designs (Coonrad/Morrey, Nexel, and Discovery) to evaluate contact area and polyethylene stresses.
RESULTS: Increasing shoulder abduction resulted in minimal changes to the elbow joint reaction force but greater joint moments. All implants showed greater peak stresses with increasing shoulder abduction-elbow varus. Discovery and Nexel achieved greater contact area (23% vs > 100%) and demonstrated up to 39% lower peak polyethylene stresses compared with the Coonrad/Morrey design.
CONCLUSIONS: Shoulder abduction results in a varus moment at the elbow. Newer bearing designs (Nexel and Discovery) provide a combination of higher contact area, improved load sharing, reduced edge loading, and lower stresses through elbow range of motion when compared with a cylindrical hinge-bearing design (Coonrad/Morrey).
CLINICAL RELEVANCE: Although the Coonrad/Morrey is a clinically successful prosthesis, our physiological loading model shows that Discovery and Nexel provide greater contact area, better load sharing and lower peak stresses. This may lead to a decrease in polyethylene wear rates and the eventual risks of osteolysis and aseptic loosening. Further studies are needed to determine how these findings translate clinically.