Excellent long-term survival rates associated with the absence of stem subsidence have been achieved with total hip arthroplasty (THA) using femoral components cemented line-to-line (“French Paradox”). Recently, short stems have been introduced in order to preserve diaphyseal bone and to accommodate to minimal invasive THA and a variety of clinical situations. The aim of the current study was to quantify the rotational and tilting stability of a Kerboull stem of varying length after line-to-line cementation using a validated in-vitro model. The femoral component made of M30NW stainless steel was derived from the original Kerboull stem. It had a double taper, a highly polished surface, and a quadrangular cross-section. Four stem lengths were designed from the original length with a distal reduction of 6, 12, 17 and 22%, whereas the proximal body geometry of the implant remained unaffected. For each stem length, five specimens were implanted into a non-canal synthetic femoral model. The femoral preparation was performed in order to obtain rotational and tilting stability of the stem prior to the line-to-line cementation. Spatial micro-motions of the specimens were investigated using a validated rotational measuring set-up. In addition, in a second separate step, the specimens were exposed to a ventro-dorsal moment to mimic varus-valgus moment. Statistical analysis was performed using ANOVA with Fisher PLSD.Introduction
Materials & methods
The wear performances of polyethylene in THA are influenced at a great extent by the manufacturing process. During the past decade, highly cross-linked materials have been developed with encouraging results in terms of wear, whereas another body of the literature has indicated potential catastrophic failures related to reduced fatigue properties and oxidation due to lipids adsorption and fatigue mechanism. Also, each of the materials available on the market has its own processing characteristics. Therefore, a specific evaluation is necessary for each of them. The aim of this retrospective study was to evaluate the wear properties of metal-back sockets using a first generation highly cross-linked PE in a consecutive series of primary THAs. Between August 2005 and December 2007, 80 patients (80 hips) with a mean age of 62.7 ± 8.9 years were included. All patients had a 28mm CoCr femoral head articulating with a highly cross-linked insert (Highcross®, Medacta SA) that was 100 Mrads gamma radiated, remelted at 150°C, and ethylene oxide sterilized. The primary criterion for evaluation was linear head penetration measurement using the Martell system, performed by an investigator trained to this technique. Also, steady state wear was calculated. Functional results were evaluated according to WOMAC score.Introduction
Materials
