WEAR MEASUREMENT OF RETRIEVED POLYETHYLENE ABG 1 CUPS BY UNIVERSAL-TYPE MEASURING MICROSCOPE AND X-RAY METHODS

A simple method of measuring the wear of explanted acetabular component inserts

Objectives

The determination of the volumetric polyethylene wear on explanted material requires complicated equipment, which is not available in many research institutions. Our aim in this study was to present and validate a method that only requires a set of polyetheretherketone balls and a laboratory balance to determine wear.

Methods

The insert to be measured was placed on a balance, and a ball of the appropriate diameter was inserted. The cavity remaining between the ball and insert caused by wear was filled with contrast medium and the weight of the contrast medium was recorded. The volume was calculated from the known density of the liquid. The precision, inter- and intraobserver reliability, were determined by four investigators on four days using nine inserts with specified wear (0.094 ml to 1.626 ml), and the intra-class correlation coefficient was calculated. The feasibility of using this method in routine clinical practice and the time required for measurement were tested on 84 explanted inserts by one investigator.

Results

In order to get the mean for all investigators and determinations, the deviation between the measured and specified wear was -0.08 ml (sd 0.12; -0.21 to 0.11). The interobserver reliability was 0.989 ml (95% confidence interval (CI) 0.964 to 0.997) and the intraobserver reliability was 0.941 for observer 1 (95% CI 0.846 to 0.985), 0.983 for observer 2 (95% CI 0.956 to 0.995), 0.939 for observer 3 (95% CI 0.855 to 0.984), and 0.934 for observer 4 (95% CI 0.790 to 0.984). The mean time required to examine the samples was two minutes (sd 2; 1 to 5).

Conclusion

The method presented here was shown to be sufficiently precise for many settings and is a cost-effective and quick method of determining the volumetric wear of explanted acetabular components. However, the measurement of wear for scientific purposes will probably continue to involve more accurate and dedicated laboratory equipment.

Cite this article: L. Krakow, A. Klockow, E. Roehner, S. Brodt, H. Eijer, J. Bossert, G. Matziolis. A simple method of measuring the wear of explanted acetabular component inserts. Bone Joint Res 2017;6:530–534. DOI: 10.1302/2046-3758.69.BJR-2016-0249.R1

Reliability of a PowerPoint method for wear measurement after total hip arthroplasty: a retrieval study using 3-dimensional laser scanning

The purpose of this study was to evaluate the reliability of the PowerPoint (PP) (2007 Version; Microsoft, Redmond, Wash) method for measuring polyethylene liner wear after total hip arthroplasty. Seventeen retrieved polyethylene liners were included in this study. Wear volumes were calculated using the PP, the Dorr and Wan, and 3-dimensional (3D) laser scanning methods. Spearman correlation coefficients for wear volume results indicated strong correlations between the PP and 3D laser scanning methods (range, 0.89-0.93). On the other hand, Spearman correlation analysis revealed only moderate correlations between the Dorr and Wan and 3D laser scanning methods (range, 0.67-0.77). The PP method can be used to monitor linear wear after total hip arthroplasty and could serve as an alternative method when computerized methods are not available.

A prospective randomised controlled trial comparing three alternative bearing surfaces in primary total hip replacement

The ideal bearing surface for young patients undergoing total hip replacement (THR) remains controversial. We report the five-year results of a randomised controlled trial comparing the clinical and radiological outcomes of 102 THRs in 91 patients who were <  65 years of age. These patients were randomised to receive a cobalt–chrome on ultra-high-molecular-weight polyethylene, cobalt–chrome on highly cross-linked polyethylene, or a ceramic-on-ceramic bearing. In all, 97 hip replacements in 87 patients were available for review at five years. Two hips had been revised, one for infection and one for peri-prosthetic fracture.

At the final follow-up there were no significant differences between the groups for the mean Western Ontario and McMaster Universities osteoarthritis index (pain, p = 0.543; function, p = 0.10; stiffness, p = 0.99), Short Form-12 (physical component, p = 0.878; mental component, p = 0.818) or Harris hip scores (p = 0.22). Radiological outcomes revealed no significant wear in the ceramic group.

Comparison of standard and highly cross-linked polyethylene, however, revealed an almost threefold difference in the mean annual linear wear rates (0.151 mm/year versus 0.059 mm/year, respectively) (p < 0.001).

Male gender, Charnley class C, and severity of bone defects predict the risk for aseptic loosening in the cup of ABG I hip arthroplasty

Background

We studied which factor could predict aseptic loosening in ABG I hip prosthesis with hydroxyapatite coating. Aseptic loosening and periprosthetic osteolysis are believed to be caused, at least in part, by increased polyethylene (PE) wear rate via particle disease. Based on it, increased PE wear rate should be associated with aseptic loosening regardless of the type of implant.

Methods

We analyzed data from 155 revisions of ABG I hip prostheses to examine the influence of patient, implant, surgery, and wear related factors on the rate of aseptic loosening at the site of the cup. This was calculated by stepwise logistic regression analysis. The stability of the implant and severity of bone defects were evaluated intraoperatively.

Results

We found that men (odds ratio, OR = 5.6; p = 0.004), patients with Charnley class C (OR = 6.71; p = 0.013), those having more severe acetabular bone defects (OR = 4 for each degree of severity; p = 0.002), and longer time to revision surgery (OR = 1.51 for each additional year; p = 0.012) had a greater chance of aseptic loosening of the cup. However, aseptic loosening was not directly predicted by polyethylene wear rate in our patients.

Conclusion

Severity of bone defects predicts the risk for aseptic loosening in ABG I cup. Factors potentially associated with the quality of bone bed and biomechanics of the hip might influence on the risk of aseptic loosening in this implant.

Wear pattern observations from TDR retrievals using autoregistration of voxel data

Because of their unique geometry, characterization of wear damage in total disc replacement (TDR) is difficult. In the article, we developed and validated an automated damage calculation technique for explanted TDR components. Eight polyethylene cores implanted from 4.6 to 16.0 years were using cone-beam microCT imaging (SCANCO Medical, Switzerland). The nominal uniform voxel size for the implant under investigation was 18 mum, however with a smaller sample size increased resolutions (10-microm nominal voxel size) could be achieved using the same microCT imaging hardware. Nominal surface data for both sizes of TDR components we examined were obtained from manufacturer's drawings (Link, Germany) and converted to highly discretized triangular meshes. The damage calculation technique utilized an initial alignment phase, followed by a pointwise calculation of the linear damage at each 3D surface point. During the alignment phase, a three-dimensional surface of the undamaged component was automatically aligned with volumetric image data from the damaged component. The alignment algorithm maximized the contact area between undamaged portions of the implant and its nominal surface using an iterative optimization technique. Linear damage at each triangle on the nominal surface was computed by moving along the local normal of the surface both inward and outward direction for a distance much less than the size of the implant. For the retrieved components, the maximum damage occurred away from the central axis of the dome close to the rim. Penetrations of up to 0.8 mm were observed in this region. Lower magnitude penetrations were observed near the pole of the dome. In conclusion, we have developed an analytical method to automatically align and measure three-dimensional surface damage with both high resolution and accuracy on implants with complicated, nonparametric, surface geometry and used this technique to analyze eight implants.

Variation in cytokine genes can contribute to severity of acetabular osteolysis and risk for revision in patients with ABG 1 total hip arthroplasty: a genetic association study

BACKGROUND

The differences in total hip arthroplasty (THA) survivorship may be influenced by individual susceptibility to periprosthetic osteolysis. This may be driven by functional polymorphisms in the genes for cytokines and cytokine receptors involved in the development of osteolysis in THA, thereby having an effect on the individual's phenotype.

METHODS

We performed a study on 22 single-nucleotide polymorphisms (SNPs) for 11 cytokines and two cytokine receptor candidate genes for association with severity of acetabular osteolysis and risk to failure in THA. Samples from 205 unrelated Caucasian patients with cementless type THA (ABG 1) were investigated. Distribution of investigated SNP variants between the groups of mild and severe acetabular osteolysis was determined by univariate and multivariate analysis. Time-dependent output variables were analyzed by the Cox hazards model.

RESULTS

Univariate analysis showed: 1) TNF-238*A allele was associated with severe osteolysis (odds ratio, OR = 6.59, p = 0.005, population attributable risk, PAR 5.2%); 2) carriers of the IL6-174*G allele were 2.5 times more prone to develop severe osteolysis than non-carriers (OR = 2.51, p = 0.007, PAR = 31.5%); 3) the carriage of IL2-330*G allele was associated with protection from severe osteolysis (OR = 0.55, p = 0.043). Based on logistic regression, the alleles TNF-238*A and IL6-174*G were independent predictors for the development of severe acetabular osteolysis. Carriers of TNF-238*A had increased cumulative hazard of THA failure according to Cox model (p = 0.024). In contrast, IL2-330*G allele predicted lower cumulative hazard of THA failure (p = 0.019).

CONCLUSION

Genetic variants of proinflammatory cytokines TNF-alpha and IL-6 confer susceptibility to severe OL. In this way, presence of the minor TNF allele could increase the cumulative risk of THA failure. Conversely, SNP in the IL2 gene may protect carriers from the above THA complications.

Optical 3D methods for measurement of prosthetic wear of total hip arthroplasty: principles, verification and results

Total hip arthroplasty (THA) significantly improves the quality of life in majority of patients with severe osteoarthritis. However, long-term outcomes of THAs are compromised by aseptic loosening and periprosthetic osteolysis which needs revision surgery. Both of these are causally linked to a prosthetic wear deliberated from the prosthetic articulating surfaces. As a result, there is a need to measure the mode and magnitude of wear. The paper evaluates three optical methods proposed for construction of a device for the non-contact prosthetic wear measurement. Of them, the scanning profilometry achieved promising combination of accuracy and repeatability. Simultaneously, it is time efficient to enable the development of a sensor for wear measurement.