The effect of component size and orientation on the concentrations of metal ions after resurfacing arthroplasty of the hip

Abstract

Increased concentrations of metal ions after metal-on-metal resurfacing arthroplasty of the hip remain a concern. Although there has been no proven link to long-term health problems or early prosthetic failure, variables associated with high metal ion concentrations should be identified and, if possible, corrected. Our study provides data on metal ion levels from a series of 76 consecutive patients (76 hips) after resurfacing arthroplasty with the Articular Surface Replacement. Chromium and cobalt ion concentrations in the whole blood of patients with smaller (<or= 51 mm) femoral components were significantly higher than in those with the larger (>or= 53 mm) components (p < 0.01). Ion concentrations in the former group were significantly related to the inclination (p = 0.01) and anteversion (p = 0.01) of the acetabular component. The same relationships were not significant in the patients with larger femoral components (p = 0.61 and p = 0.49, respectively). Accurate positioning of the acetabular component intra-operatively is essential in order to reduce the concentration of metal ions in the blood after hip resurfacing arthroplasty with the Articular Surface Replacement implant.

The Learning Curve for Adopting Hip Resurfacing Among Hip Specialists

“…Numerous studies have correlated acetabular component inclination greater than 50°to 55°with increased metal ion levels, metallosis, pseudotumors, and early failure [19,22,23,31,34]. In this study, acetabular inclination less than 45°w as achieved in 58.9% of cases and it appears the learning curve continued to slowly improve through the first 150 cases.…”

“…The component positioning parameters most strongly associated with a low early complication rate and high survivorship long-term include acetabular component inclination and femoral stem shaft angle [19,22,23,31,37,38,43,47]. Therefore, we used these measures to determine the learning curves.…”

“…It is well established that notching of the femoral neck, exposed cancellous bone, and varus placement of the femoral component increase the likelihood of femoral neck fracture [5,9,27,36,43]. Numerous studies demonstrate cup inclination or abduction angle greater than 50°to 55°is associated with high levels of serum metal ions and higher rates of early failure [19,22,23,31]. Therefore, accurate component placement is critical to avoid complications after hip resurfacing.…”

Accuracy of Acetabular Component Position in Hip Arthroplasty

“…The advent and popularity of alternative bearing surfaces has been accompanied by new complications such as polyethylene liner fracture, acoustic phenomenon, metal sensitivity, and pseudotumors. Acetabular component position has been implicated as one of several causative factors for each of these complications [21][22][23][24][25] . Higher wear rates in both conventional 26 and hard-on-hard 27 bearings are seen with higher abduction angles.…”

CORR Insights®: Does Degenerative Lumbar Spine Disease Influence Femoroacetabular Flexion in Patients Undergoing Total Hip Arthroplasty?

“…Surgeons should not dismiss spinopelvic motion just because they have a low dislocation rate, as spinal imbalance causes prosthetic impingement, which causes problems other than instability. These issues could include pain, which is often diagnosed as unexplained [6], and edge loading and accelerated wear, which are intensified with hard-on-hard articulations such as metal-on-metal [1,3,8].…”