Aims

The aims of this study were to validate the outcome of total elbow arthroplasty (TEA) in patients with rheumatoid arthritis (RA), and to identify factors that affect the outcome.

Aims

The aim of this meta-analysis was to compare the outcome of total elbow arthroplasty (TEA) undertaken for rheumatoid arthritis (RA) with TEA performed for post-traumatic conditions with regard to implant failure, functional outcome, and perioperative complications.

Due to their superior wear characteristics, oxidized Zr-2.5Nb heads are used with hip stems made of conventional orthopaedic alloys. Galvanic interactions between Zr-2.5Nb (Zr) and Ti-6Al-4V (Ti), cobalt-chromium (CoCr), and 316L stainless steel (SS) alloys were evaluated.

Galvanic current density was measured for Zr/Ti,Zr/CoCr, Zr/SS, CoCr/Ti, and CoCr/SS couples under static conditions in aneutral Ringer’s solution and in an acidic (1.7 pH) solution. To simulate fretting, one or both coupled alloys in the neutral solution subsequently were abraded by a bone cement pin (82 MPa Hertzian stress). An extended(7-day) static test in the acidic solution was performed for Zr/SS and CoCr/Ti to simulate crevice conditions. The dissolved metal ion concentration was determined using direct coupled plasma emission spectrometry.

Mean initial current densities of the Zr/SS, SS/CoCr,Zr/CoCr, CoCr/Ti, and Zr/Ti couples were 3.0, 0.36, 0.16, 0.05, and 0.04μA/cm2, respectively, in the neutral solution, and 0.57, −0.29, 0.04, 0.02, and 0.03 μA/cm2, respectively, in the acidic solution (positive when first alloy was anode). Within 30 minutes, all values decreased below 0.02μA/cm2. The current densities increased by orders of magnitude under fretting conditions. When both alloys were abraded, the highest values were minus;677 and 464 μA/cm2 for CoCr/Ti and Zr/SS, respectively. In the extended static test of Zr/SS, the mean total metal ion concentration decreased from 8.15 mg/L when the alloys were uncoupled to 4.50 mg/L(p=0.007) when they were coupled. For CoCr/Ti, the change from 1.28 to 1.72mg/L when the alloys were coupled was not statistically significant(p=0.22).

With its strong tendency to passivate, the Zr alloy produced galvanic interactions within the range observed with conventional alloy couples. Its anodic characteristic helped protect SS in a galvanic couple.

Introduction: Bone loss, lack of ingrowth, and use of extended trochanteric osteotomies (ETO) all contribute to loss of proximal support in revision hip arthroplasty, leading to increased stem stresses. Clinical observations of fractured, distally fixed, proximally unsupported stems necessitates methods to mitigate proximal femoral bone loss. This study evaluated various cabling and strut techniques to reduce stem stresses seen with bone loss and ETO.

Methods: Finite element analysis (FEA) was performed on a clinical case of a fractured revision stem after an ETO. Stem stresses were determined and multiple treatment options were evaluated.

An instrumented extensively porous coated stem was implanted in composite femur models (n=3) and mechanically tested. The stem stresses resulting from proximal overbroaching, ETO, cable grips, and various cable and strut constructs were determined.

Results: Stem stresses increased 62 percent with a strut cabled above the distal portion of the ETO using FEA methods. This increase was reduced to as little as 10 percent when a third cable was added distal to the ETO.

Stem stresses increased 98 when a proximally loose stem was combined with an ETO using laboratory tests. This stress was decreased by up to 37 percent when a long trochanteric plate was utilized.

Discussion and conclusion: This study demonstrates the importance of proximal femoral support to the stresses imparted upon a cementless revision hip prosthesis. In the presence of proximal bone loss, an ETO dramatically increases these stresses, which can be reduced by cabling and strut techniques.

Introduction: Proximal femoral bone loss, failure of ingrowth, and the use of extended trochanteric osteotomies (ETO) all contribute to loss of proximal support in revision hip arthroplasty. This leads to increased stem stresses, and can lead to the fracture distally fixed, proximally unsupported uncemented revision femoral stems. This study evaluates various cabling and strut techniques to reduce stem stresses seen with bone loss and ETO.

Methods: Finite element analysis (FEA) was performed on a clinical case of a fractured revision stem after an ETO. Stem stresses were determined and multiple treatment options were evaluated.

An instrumented extensively porous coated stem was implanted in composite femur models (n=3) and mechanically tested. The stem stresses resulting from proximal overbroaching, ETO, cable grips, and various cable and strut constructs were determined.

Results: Stem stresses increased 62 percent with a strut cabled above the distal portion of the ETO using FEA methods. This increase was reduced to as little as 10 percent when a third cable was added distal to the ETO.

Stem stresses increased 98 when a proximally loose stem was combined with an ETO using laboratory tests. This stress was decreased by up to 37 percent when a long trochanteric plate was utilized.

Discussion and Conclusion: This study demonstrates the importance of proximal femoral support to the stresses imparted upon a cementless revision hip prosthesis. In the presence of proximal bone loss, an ETO dramatically increases these stresses, which can be reduced by various cabling and strut techniques.