[Luxation of total hip prosthesis. Mathematic modelization, biomechanical approach].
Two particular aspects of total hip prosthesis dislocations were assessed by a mathematical method. A theoretical analysis of the intra-prosthetic motions, in function of the architectural parameters was presented as well as a biomechanical approach of the dynamic stability of the prosthetic hip during the flexion. It showed then two potential causes of dislocations: malposition dislocations, due to the block-effect of the femoral neck on the acetabular border; the position of the acetabular cup appeared as predominant for a given type of prosthesis too anteversed and/or too vertical, it limited the movement of external rotation at the origin of anterior dislocations; too horizontal and not enough anteversed it obstructed the flexion, especially if there was an association of internal rotation and adduction, the dislocation was then posterior. dislocation by muscular discoaptation. Here, the dislocating forces, during the flexion of the hip, were greater than the coaptation phenomenon which became precarious by the arthroplasty and quantified, in our model, by a multifactorial parameter translating the behaviour of the gluteus medius muscle during flexion.
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Service de Chirurgie Orthopédique et Traumatologique, Hôpital Ambroise Paré, Boulogne.
Benoit
J
J
Lortat-Jacob
A
A
Didry
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R
D001696:Biomechanical Phenomena; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D004204:Joint Dislocations; D008433:Mathematics; D008962:Models, Theoretical; D011475:Prosthesis Failure
La luxation des prothèses totales de hanche. Modélisation mathématique, approche biomécanique.