The clinical outcomes and radiological findings for cemented titanium stems remain controversial. In 2004, we produced a straight-collared double-tapered stem made from a titanium alloy with a smooth surface for cemented total hip arthroplasty. In this study, we retrospectively examined the mid-term outcomes of this stem.
We retrospectively reviewed 61 hips that had undergone primary cemented total hip arthroplasty with a collared smooth double-tapered titanium alloy femoral stem, after a minimum of 5 years (mean 6.1, range 5.0-7.3). Patients were evaluated preoperatively and postoperatively with the Merle d'Aubigné and Postel hip score. Radiographic examination was performed for evaluation of the cementing technique, the alignment of the stem, subsidence within the cement mantle, radiolucent lines at the cement-bone or cement-stem interface, cortical hypertrophy, and calcar resorption.
The clinical evaluation by the Merle d'Aubigné and Postel hip score was improved from 9.4 ± 1.9 preoperatively to 15.9 ± 1.6 at the time of final follow-up. The overall survival rate was 100% at 7 years, when radiological loosening or revision for any reasons was used as the endpoint. Five stems subsided less than 1 mm vertically. Nonprogressive radiolucence at the cement-bone interface occurred in six hips, without osteolysis. Cortical hypertrophy was observed in five hips and second-degree calcar resorption in 11 hips.
Our results in this study show good outcomes for cemented, collared, smooth, double-tapered titanium alloy femoral stems at a minimum follow-up of 5 years.
"For examples, Müller straight titanium stems, after 15 years, had a survival rate of 75.4%, while after 8 years, the survival rate of titanium stems with rough surface was 76.7% (Akiyama et al., 2010, 2011; Francetti et al., 2014). Consequently, due to these conflicting reports for many designs of titanium stems applied to the clinic, these stems are no longer favored in the Western World populations and to a great extent cemented femoral stems made from CoCrMo or stainless steel have replaced titanium stems (Akiyama et al., 2011). Nevertheless, Haruhiko discovered that the body's physical load could have a great effect on loosening failures, and that the titanium alloy stems are significantly more suitable for Japanese as average Japanese body weight is 20 Kg lower than Eurpeans. "
[Show abstract][Hide abstract] ABSTRACT: Background:
In cemented total hip arthroplasty (THA), a polished tapered femoral stem with a design based on the taper-slip concept enables extremely reliable and durable fixation. In contrast, cemented femoral stems made from titanium alloys are not favored because of reports describing insufficient clinical outcomes. However, we have reported excellent clinical and radiological outcomes for cemented titanium stems made using the composite-beam concept. This study examines the characteristics of cemented titanium femoral stems with a smooth surface.
The bonding strength between titanium alloys with different surface finishes and bone cement was evaluated by use of push-out and detachment tests. Torsional stability tests were performed to evaluate the initiation and propagation of disruption of the fixation of cemented stems at the cement-implant interface. The wear resistance was investigated by use of wear-friction tests performed using a multidirectional pin-on-disc machine. The bone strain loaded on to the femoral cortex was measured by use of an implanted Sawbone and analyzed by use of the finite element method.
The push-out and detachment tests revealed increasing cement adhesion strength with increasing degree of roughness of the metal surface. The torsional stability tests indicated that a load >1,000 N led to progressive debonding between the cement and the implant with a smooth surface finish. Interestingly, wear-friction tests revealed the wear rate for polished titanium surfaces was clearly higher than for smooth surfaces. In addition, the greater elasticity of titanium stems compared with cobalt-chromium stems transmitted the external load to the proximal side of the femur more effectively.
The smooth surface finish of the stems is an important factor for the satisfactory clinical and radiological outcomes of cemented titanium femoral stems. The greater elasticity of a titanium stem effectively transmits the external load to the medial side of the femur.
[Show abstract][Hide abstract] ABSTRACT: The cemented femoral stem with a distally straight cylindrical shape was designed to fill the distal femoral canal to facilitate higher cement pressurization and stability. We examined the mid-term outcomes of a stem made of titanium alloy and the efficacy of this shape.
Four hundred and twenty-nine consecutive patients (505 hips), who underwent a total hip arthroplasty with the distally straight cylindrical stem made of titanium alloy as their primary hip arthroplasty at two institutes, were followed for a minimum 2 years. Loosening was defined as subsidence of over 3 mm, tilting of the femoral component, or fracture of the cement or the stem. A continuous radiolucent line along the entire interface was considered to indicate loosening, too. We examined the interface stresses on the distally straight cylindrical stem compared with a newly manufactured femoral prosthesis with a double-taper design using a finite element model study.
The mean follow-up was 101.3 months after surgery. Thirty patients (30 hips) had aseptic loosening of the stems. Of these 30 hips, 18 had osteolysis, 17 showed subsidence, and 11 had cement fractures at the tip of the stem. These 11 hips had osteolysis and ectasia in the same place: the stem tip. The stem survival rate with stem loosening as the end-point was 94.4 % at 10 years and 66.9 % at 15 years. A finite element model study revealed higher stress around the tip of the cylindrical stem compared with that in the double-taper stem.
The straight cylindrical stem is potentially subject to early failure because of high stress around the tip of the stem, and showed a characteristic loosening with osteolysis and ectasia at the tip of the stem.
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