Does using a polyethylene RM press-fit cup modify the preparation of the acetabulum and acetabular offset in primary hip arthroplasty? - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Orthopaedics & Traumatology: Surgery & Research Année : 2017

Does using a polyethylene RM press-fit cup modify the preparation of the acetabulum and acetabular offset in primary hip arthroplasty?

Résumé

Introduction When performing total hip arthroplasty (THA), it is important to maintain the femoral and acetabular offsets to ensure good joint stability and to restore the function of the hip abductor muscles. In our practice, we mainly use a lateralized stem and hollow out the acetabulum to the quadrilateral plate to accommodate a press-fit polyethylene cup. However, the repercussions of this preparation method, which is driven by the cup's design, are not known. We carried out a retrospective study to assess: (1) the changes in the femoral and acetabular offset; (2) the height of the center of rotation; and (3) the repercussions on wear. Hypothesis We hypothesized there would be no significant differences between the preoperative and postoperative femoral and acetabular offsets. Patients and methods We reviewed 88 primary THA cases performed with the RM Pressfit™ cup that had a minimum of 5 years’ follow-up. A lateralized self-locking Muller-type cemented femoral stem was used in 92.0% of cases and a standard stem in 8.0%. Measurements were done on plain radiographs with MHP™ and Mesurim Pro™ software. The average follow-up was 6.5 years (5–8). Results On average, the acetabular offset was reduced by 2.75 mm ± 5.9 mm (range: –17.5 to +10.6 mm) (P < 0.001) and the femoral offset was increased by 0.01 mm ± 5.5 mm (range: –17.8 to +11.0 mm) (P = 0.99). In terms of total offset, medialization of 2.74 mm ± 7 mm (range: –17.7 to +18.2 mm) was found (P = 0.001). The acetabular center of rotation was on average 4.77 mm ± 5.1 mm higher (P < 0.001). The mean annual wear at the more recent follow-up (min.: 5 years) was 0.068 mm (range: 0.01 to 0.25 mm) per year. The wear was not impacted by having more than 5 mm change in offset. Discussion Measurements of acetabular offset revealed statistically significant medialization due to the type of implant used and the surgical technique. The anatomical technique consists of positioning the cup in subchondral bone without contacting the quadrilateral plate. This preserves bone stock, which may be useful later on if the cup is revised, particularly in younger patients. Conversely, the femoral offset did not change significantly, despite the use of lateralized stems in 92.0% of cases. We measured an annual wear rate of 0.068 mm per year, which is lower than in other published studies, possibly because our patient population was older. Level of evidence IV, retrospective study.

Dates et versions

hal-01649251 , version 1 (27-11-2017)

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R. Erivan, S. Aubret, G. Villatte, A. Mulliez, S. Descamps, et al.. Does using a polyethylene RM press-fit cup modify the preparation of the acetabulum and acetabular offset in primary hip arthroplasty?. Orthopaedics & Traumatology: Surgery & Research, 2017, 103 (5), pp.669 - 674. ⟨10.1016/j.otsr.2017.03.026⟩. ⟨hal-01649251⟩
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