Facteurs du risque de fracture du fémur distal dans les prothèses totales du genou: Étude de 32 fractures per et postopératoires

Abstract

Purpose of the study We reviewed fractures of the distal fémur occurring during or after total knee arthroplasty in order to identify risk factors. Material and methods Twelve introperative fractures occurred between 1990 and 2000 among 617 total knee arthroplasties performed during this period. The circumstances of thèse fractures were noted in comparison with other prosthetic implants. Twenty other fractures of the distal fémur occurred in 20 patients who had had a total knee arthroplasty during the same time period. Mean patient âge at surgery was 72 years (range 69-77). In addition to démographie data, we noted risk factors: bone deminerali-zation related to gênerai condition, rheumatoid arthritis or corticosteroid therapy, trochlear notch prior to the trochleal eut, bone résorption under the fémoral implant, repeated knee surgery, abnormal stress on the distal fémur due to hip disease, periprosthetic osteolysis without loosening related to polyethylene débris or metallosis, loosening, type of prosthesis, loss of bone stock because of the fémoral implant, life of prosthesis. Results Intraoperative fractures usually occurred in spécifie circumstances: use of a posterior stabilized prosthesis, probably with insufficient préparation and position of the stabilization élément, probably excessive impaction in osteoporotic bone (rheumatoid arthritis), difficult exposure (arthroplasty after prior osteotomy), fracture starting from the separator passing over the posterior aspect of the tibia and reaching the intercondylar notch. Independently of thèse intercondylar fractures, supra-condylar or diaphyseal fractures were essentially observed for revision prostheses using a fémoral stem. Postoperative fractures were observed in patients who had prior surgery of the distal fémur (revision of fémoral osteotomy, fracture of the distal fémur, arthrodesis), in patients with significant loss of bone stock (posterior stabilized prosthesis), or poor bone quality (rheumatoid arthritis), and in elderly patients with neurological impairment and fréquent falls. The trochlear notch did not appear to be sufficient to be the only cause of fracture but was nevertheless an élément frequently associated with other risk factors. Discussion and conclusion This study shows that fracture of the distal fémur occurs in certain preferential circumstances. Considering thèse éléments, a certain number of préventive measures can be discussed for technical modifications or choice of implants.