The effect of a lateral flare feature on implant stability

Abstract

We reviewed the X-rays of 109 patients with 115 primary total hip replacements utilizing a lateral flare cementless stem to assess axial migration and stability. The average follow-up was 48.6 (24-104) months. The average subsidence at 2 years was 0.32 mm, remaining at a level below 1 mm for the duration of the followup. Even though there were ten reoperations involving either the change of a polyethylene liner and the acetabular component, or both, none of the patients required a femoral stem revision. It was concluded that the proximal geometry of the stem provides significant initial stability, which seems to be preserved throughout a long follow-up period.Résumé Nous avons examiné les clichés de 109 malades avec 115 prothèses primaires de la hanche utilisant une tige fémorale non cimentée avec évasement latéral pour contrôler la migration axiale et la stabilité. La moyenne de suivi était 48.6 mois ( 24 à 104 mois). L'enfoncement moyen à 2 ans était 0.32 mm., restant en dessous de 1 mm pendant la suite de l'évolution. Bien qu'il y eût 10 ré -opérations pour changement de l'insert en polyéthylène et/ou du composant acétabulaire, aucun des malades n'a eu besoin d' une révision de la tige fémorale. Il a été conclu que la géométrie de la tige proximale donne une bonne stabilité initiale qui paraît être conservé pendant une longue période. IntroductionSince the development of the total hip arthroplasty, subsidence has been used as a means to predict long-term survival of the prosthesis [5]. It has been a useful tool in analysis of new prostheses early in their life because it is a reliable early predictor of failure. Malchau et al. showed that the greater the migration found by the 1-year follow-up, the higher the risk of revision [8]. Roentgen stereophotogrammetric analysis (RSA) has demonstrated a high incidence of subsidence in cemented and noncemented stems in the first 4-6 months. The amount of subsidence diminishes over the next year and one-half and then becomes insignificant in most successful stems.The lateral flare femoral stem features a proximal lateral expansion, which was designed to engage the lateral cortex of the femur in the metaphysis, allowing for a more concentric loading in the proximal femur [3]. The use of a 'proximal plug' configuration relieves distal stress transfers and is inherently stable [10]. The same geometry demonstrates comparable behavior in the revision setting, along with significant preservation of the preoperative bone stock [12].The purpose of the present study was to assess axial displacement values of a series of total hip arthroplasty in which a lateral flare cementless femoral component was used. The emphasis of this report was placed on the femoral component. Materials and methodsThe inpatient and outpatient records and radiographs of 101 patients who underwent 115 total hip arthroplasties from June 1992 through December 1998 were reviewed. Inclusion criteria for this study were a minimum of a 2-year follow-up from the first postoperative office visit and the ...

Promising mid-term results of total hip arthroplasties using an uncemented lateral-flare hip prosthesis: a clinical and radiographic study

“…Even though the use of a collar may increase the axial compression to the bone [5], it may impede the wedging effect of the lateral flare [18]. Its value as an additional feature to maximize prosthesis-bone contact in the primary setting is secondary to the stabilizing effect imposed by the extended proximal geometry of the implant [17] and the collar, therefore, is not a feature of the design of this stem.…”

“…The sturdy fixation achieved by engaging the metaphysis and loading the femur both medially and laterally creates an inherently stable construction [17,24,25]. The proximal anterior bow and the flat posterior surface create a trapezoidal proximal cross-section allowing for a near complete filling of the metaphysis in both the anterior-posterior and the mediallateral planes.…”

“…Finally, when axial migration, bone preservation and clinical results are compared, the mid-term results of total hip arthroplasty with an off-the-shelf Revelation femoral component compare favourably with its earlier custom counterpart [17,24,25].…”

“…The present stem is not press-fitted into the femur or driven down the diaphysis to achieve interference fit; instead, the broaching and preparation of the femur creates the necessary contour in the metaphysis for the stem to be toggled down and gently tapped during insertion into its resting position upon the medial and lateral cortices ("rest fit") [17].…”

Our Experience with Short Stem Hip Replacement Surgery

“…Fatto et al [9] further refined this model in 1995 and showed that the lateral femoral cortex can be effectively used to carry compressive loads. Leari et al [10] reviewed radiographs of primary THR with a lateral flare for axial migration and stability. They concluded that a prominent lateral flare provided significant initial stability through early bony ingrowth, which is vital for long term implant stability and provision against stress shielding.…”