Correlation between inclination of the acetabular component and metal ion levels in metal-on-metal hip resurfacing replacement

141

138

Background Pseudotumors are sterile inflammatory lesions found in the soft tissues surrounding metal-on-metal (MOM) and metal-on-polyethylene hip arthroplasties. In patients with MOM hip arthroplasties, pseudotumors are thought to represent an adverse reaction to metal wear debris. However, the pathogenesis of these lesions remains unclear. Currently, there is inconsistent evidence regarding the influence of adverse cup position and increased wear in the formation of pseudotumors. Questions/purposes We therefore determined whether pseudotumor formation was associated with (1) adverse cup position, (2) raised metal ion levels, and (3) increased wear rates of the retrieved components. Methods We retrospectively reviewed all 352 patients for whom we had retrieved specimens from revisions of a current-generation MOM hip prosthesis between February 2008 and September 2010; of these, 105 met our inclusion criteria. We used multivariate logistic regression analysis to compare acetabular orientation, metal ion levels before revision, and component wear rates between patients with (n = 72) and without (n = 33) pseudotumors, according to findings on metal artifact reduction sequence MRI. Results The proportion of patients demonstrating evidence of a pseudotumor in well-positioned hips was similar to those with adverse cup positions (67% and 66%, respectively). Patients revised with pseudotumors had similar whole-blood metal ion levels and component wear rates to those who were not revised. Conclusions Pseudotumors were not associated with increased wear or metal ion levels, suggesting patient susceptibility is likely to be more important.

Section: Discussionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Pseudotumors Are Common in Well-positioned Low-wearing Metal-on-Metal Hips

Matthies

Skinner

Osmani

et al. 2012

141

138

“…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.…”

Section: Discussionmentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

The Learning Curve for Adopting Hip Resurfacing Among Hip Specialists

Nunley

Zhu

Brooks

et al. 2010

Patient demand and surgeon interest in hip resurfacing has recently increased, but surgeons in the United States are relatively inexperienced with this procedure. We determined the learning curve associated with hip resurfacing and compared the rate of early complications of the first 650 hip resurfacings between five experienced hip surgeons and a national safety survey database study we previously published, which included 89 surgeons and 537 hip resurfacings. Patient demographics and adverse events were recorded. Specific features on pre-and postoperative radiographs were measured in a blinded fashion by a single observer. There were 13 major complications (2.0%), which is 3.7 times lower than our national safety survey complication rate of 7.4%. All fractures occurred in the first 25 cases performed. The complication rate was higher for the first 25 procedures (5.6%) compared with the second 25 procedures (1

“…Previously, a few studies were directed at proper femoral component stem orientation in HRA [19,26,27]. However, it now appears proper placement of the acetabular component may be even more critical to the success of this procedure [8,9,11,21,30]. We investigated the value of using a single intraoperative portable crosstable AP radiograph to improve the accuracy of placing the acetabular component within a target range of inclination.…”

Section: Discussionmentioning

confidence: 99%

Intraoperative Radiographs for Placing Acetabular Components in Hip Resurfacing Arthroplasty

Gross

Liu

Webb

2011

Background Various clinical and biomechanical studies suggest certain acetabular positions may be associated with higher wear and failure rates in modern metal-on-metal hip resurfacing arthroplasties. However, there are no widely available, reliable, and cost-effective surgical techniques that ensure surgeons are able to place an acetabular component within the safe range of inclination angles after hip resurfacing surgeries. Questions/purposes We investigated the accuracy of intraoperative radiographs to determine the acetabular inclination angle in resurfacing arthroplasty procedures. Patients and Methods The study group included the first 100 resurfacing arthroplasties performed after we started routinely checking the intraoperative acetabular inclination angles. The acetabular component was repositioned if the intraoperative acetabular inclination angle was out of the target range of 30°to 50°. The control group included the previous 100 resurfacing arthroplasties performed without the benefit of intraoperative radiographs. A posterior minimally invasive surgical approach was used in both groups. Demographics and diagnoses were similar in both groups. ResultsThe average (± SD) difference between the intraoperative and 6-week radiographs was 2.7°± 2.5°. The acetabular inclination angles at 6-week followup were within the targeted range more frequently in the study group than in the control group (outliers: 4% versus 29%). Conclusions These data suggest a single intraoperative radiograph is a quick, reliable, and cost-effective method for ensuring the acetabular inclination angle is within the targeted range. Level of Evidence Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.