Characterization of wear debris in total elbow arthroplasty

Polyethylene wear testing of a nonmechanically linked total elbow replacement

BACKGROUND

The objective of this study was to perform a polyethylene wear test on a nonmechanically linked total elbow arthroplasty implant using a clinically relevant in-vitro elbow wear test methodology that simulated 10 years of use in the light to moderate activity of daily living range.

MATERIALS AND METHODS

The test protocol applied an 80° arc of ulnohumeral motion beginning at 30° shy of full extension and progressing to 110° of flexion. Force was applied at 7° to recreate a valgus load on the elbow. A variable joint load profile at a frequency of 0.5 Hz was employed. The implants were tested for 5 million cycles (mc) in a bovine serum lubricant. Implant component failure was characterized and polyethylene wear was determined gravimetrically.

RESULTS

After 5 mc, the small polyethylene bushing wear rate was 0.56 mg/mc. The medium size wear rate was 0.28 mg/mc. Three large sizes were tested and the average wear rate was 0.39 ± 0.07 mg/mc. No implant failure was identified.

CONCLUSION

The test recreated an in vivo loading environment and measured polyethylene wear rates at specified cycle counts. The test demonstrated less wear than other joint replacements. Further clinical evaluation is necessary to determine if this translates into reduced complications of total elbow replacement associated with wear.

Update on elbow arthroplasties with emphasis on imaging

Elbow arthroplasty is increasing in popularity and can be used to treat many conditions, such as trauma, primary and secondary osteoarthritis, inflammatory arthritis, and osteonecrosis. Total elbow arthroplasty (TEA) is reserved for patients with severe symptoms refractory to more conservative management. In addition to TEA, hemi-arthroplasty, interposition arthroplasty, and resection arthroplasty also play roles in the management of elbow pain. There are specific indications for each type of arthroplasty. Postoperative complications may occur with elbow arthroplasties and may be surgery or hardware related. Imaging is important in both pre-operative planning as well as in post-surgical follow-up. This article reviews the different types of elbow arthroplasties, their indications, their normal postoperative imaging appearances, and imaging findings of potential complications.

Mettl3‑mediated m6A RNA methylation regulates osteolysis induced by titanium particles

Peri‑prosthetic osteolysis (PPO) induced by wear particles is considered the primary cause of titanium prosthesis failure and revision surgery. The specific molecular mechanisms involve titanium particles inducing multiple intracellular pathways, which impact disease prevention and the targeted therapy of PPO. Notably, N6‑methyladenosine (m6A) serves critical roles in epigenetic regulation, particularly in bone metabolism and inflammatory responses. Thus, the present study aimed to determine the role of RNA methylation in titanium particle‑induced osteolysis. Results of reverse transcription‑quantitative PCR (RT‑qPCR), western blotting, ELISA and RNA dot blot assays revealed that titanium particles induced osteogenic inhibition and proinflammatory responses, accompanied by the reduced expression of methyltransferase‑like (Mettl) 3, a key component of m6A methyltransferase. Specific lentiviruses vectors were employed for Mettl3 knockdown and overexpression experiments. RT‑qPCR, western blotting and ELISA revealed that the knockdown of Mettl3 induced osteogenic inhibition and proinflammatory responses comparable with that induced by titanium particle, while Mettl3 overexpression attenuated titanium particle‑induced cellular reactions. Methylated RNA immunoprecipitation‑qPCR results revealed that titanium particles mediated the methylation of two inhibitory molecules, namely Smad7 and SMAD specific E3 ubiquitin protein ligase 1, via Mettl3 in bone morphogenetic protein signaling, leading to osteogenic inhibition. Furthermore, titanium particles induced activation of the nucleotide binding oligomerization domain 1 signaling pathway through methylation regulation, and the subsequent activation of the MAPK and NF‑κB pathways. Collectively, the results of the present study indicated that titanium particles utilized Mettl3 as an upstream regulatory molecule to induce osteogenic inhibition and inflammatory responses. Thus, the present study may provide novel insights into potential therapeutic targets for aseptic loosening in titanium prostheses.

Analytical Problems with Preparation of Paraspinal Tissues from Patients with Spinal Fusion for Analysis of Titanium

Preparation of paraspinal tissue of patients with implants for elemental analysis is a challenge because it contains titanium in the ionic form, as well as metallic debris. Most literature reports focus on dissolving the tissue, but the impact of digestion conditions on metallic debris of Ti has not been investigated. In our work, various digestion conditions, including systems, compositions of oxidising mixture, and time, were tested aiming (i) to digest the tissue without digestion of metallic titanium to quantify soluble Ti and (ii) to digest metallic titanium debris to asses total Ti content in tissue. The experiments were performed in a closed mode using a microwave-assisted system and a carbon heating block. Our study revealed that total digestion of titanium was impossible in the tested conditions and the maximal level of digested titanium was below 70%. The mineralisation with the use of concentrated nitric acid was optimal to prepare paraspinal samples to analyse the soluble titanium form because metallic titanium passivated and did not migrate to the solution. The elaborated conditions were applied to determine titanium ion in the periimplant tissue of patients with three different titanium-based surgical systems, including traditional growing rod (TGR), guided growth systems (GGS), and vertical expandable prosthesis titanium rib (VEPTR).

Quantitative ultrahigh-molecular-weight polyethylene wear in total elbow retrievals

BACKGROUND

The purpose of this study was to evaluate ultrahigh-molecular-weight polyethylene (UHMWPE) wear and damage from retrieved total elbow arthroplasty components and compare in vivo wear with wear produced in vitro.

METHODS

Explanted total elbow components were collected at revision surgery. UHMWPE damage was characterized visually, whereas penetration and wear were quantified using micro-computed tomography and gas pycnometry. Volumetric wear rates were compared with historical hip data, and wear data were compared with reported in vitro wear test data.

RESULTS

Humeral bushing damage primarily occurred in the form of burnishing, scratching, and pitting at the articular face in the region of contact with the ulnar component. Wear of the ulnar bushings was concentrated on the edge of the component at the point of contact with the axis pin. Pitting and embedded debris were dominant damage modes, in addition to burnishing and delamination. Backside wear was negligible. The median linear penetration rates of the lateral, medial, and ulnar bushings were 0.14 mm/yr (range, 0.01-0.78 mm/yr), 0.12 mm/yr (range, 0.03-0.55 mm/yr), and 0.11 mm/yr (range, 0.01-0.69 mm/yr), respectively. The volumetric wear rates of the lateral, medial, and ulnar bushings were 5.5 mm³/yr (range, 0.7-37.2 mm³/yr), 5.9 mm³/yr (range, 0.6-25.5 mm³/yr), and 5.5 mm³/yr (range, 1.2-51.2 mm³/yr), respectively.

CONCLUSIONS

The observed wear rates were similar to those reported in well-functioning total hip replacement patients with conventional UHMWPE bearings. We found limitations in reported in vitro testing resulting in wear that was not consistent with our retrieval data. We recommend further investigation to clinically validate in vitro simulation to provide appropriate loading protocols for elbow wear simulation.

In vitro and in vivo investigations of a-C/a-C:Ti nanomultilayer coated Ti6Al4V alloy as artificial femoral head

Hydrogen-free a-C/a-C:Ti nanomultilayer (a-C NM) films were deposited on medical Ti6Al4V by the magnetron sputtering technique under bias-graded voltage. Cell tests and implantations were performed for the a-C NM films coated Ti6Al4V with the uncoated Ti6Al4V as the control. The canine total hip arthroplasty (THA) surgeries were conducted for 12 dogs using the coated femoral heads, with the CoCr heads as the control. Results of cell tests showed that the coated Ti6Al4V had no cytotoxicity, and there was no statistical difference of the cell attachment rates between the coated and uncoated sample (P = 0.091). No significant difference of the tissue response around the coated and uncoated implants were observed after the intramuscular (P = 0.679) and intraosseous implantations (P = 0.122). After two years of successful canine THA, the polyethylene wear particles isolated from periprosthetic soft tissue showed similar sizes, shapes and counts in the two groups (all of the P values >0.05). The retrieved femoral heads showed slightly change of the surface roughness, but no statistical differences between groups (P = 0.696). However, the systemic metal ion analysis indicated that the content of Co and Cr ions released in the coated group (Co: 0.71 ± 0.06 μg/L, Cr: 0.52 ± 0.05 μg/L) were significant lower than that in the control (Co: 1.98 ± 0.16 μg/L, Cr: 1.17 ± 0.19 μg/L) (both P < 0.005). Histological analysis of the periprosthetic tissue in CoCr group showed a severer histiocyte response than that in the coated group (P = 0.029). The head-taper interfaces showed galvanic corrosion attack in the CoCr group, but not in the coated Ti6Al4V group. Therefore, the a-C NM films coated Ti6Al4V exhibited good biocompatibility as an implant material. Compared with the CoCr, the coated Ti6Al4V femoral head could provide comparable in vivo wear properties, release less harmful metal ions and reduce the inflammatory response in periprosthetic tissue, which may help to prolong the longevity of prostheses.

Development and Validation of a Method for Preclinical Durability Evaluation of Linked Semiconstrained Total Elbow Replacement Prostheses

Total elbow replacement (TER) is a clinically successful procedure yet isolated, gross mechanical complications associated with implant durability persist. The objectives of this study were to (1) develop a clinically relevant in vitro methodology to replicate the reported damage modes and (2) demonstrate durability improvements of a next-generation linked, semiconstrained design. Two TER prostheses were tested on a biaxial test frame at 1.4 Hz in 37 ± 3° deionized water through 0° to 130° flexion/extension at various load levels simulating high demand, posttraumatic patients until either component failure or run out to 200 000 cycles. The damage patterns of tested components were qualitatively compared to retrieved components to establish the clinical validity of the methodology. The run out load of design 1 was equivalent to 100 N weight in hand (WIH). Specimens tested at higher load levels exhibited multimodal damage consistent in appearance with the clinical literature. The minimum run out load of design 2 was 110 N WIH with no significant damage observed on the components. The methodology developed here was shown to reproduce the clinical damage modes associated with TER in high demand, posttraumatic patients. The method was able to distinguish performance differences within and between 2 different linked, semiconstrained designs.

Comparing damage on retrieved total elbow replacement bushings with lab worn specimens subjected to varied loading conditions

Complication rates following total elbow replacement (TER) with conventional implants are relatively high due to mechanical failure involving the UHMWPE bushings. Unfortunately, there are no standardized pre-clinical durability testing protocols for assessing the durability of TER components. This study examines the damage observed on retrieved humeral bushings, and then uses in vitro durability testing with two different loading protocols to compare resulting damage. Damage on 25 pairs of retrieved humeral bushings was characterized using micro-computed tomographic imaging techniques. The damage was compared with that of in vitro test specimens which were subjected to 200 K cycles of either high joint reaction force (high JRF) or high varus moment (high VM) loading. Material removal (mass loss) from bushing components was measured using gravimetric techniques. Thinning was less for retrieved bushings which were still assembled in their humeral component, versus bushings which were loose (0.3 ± 0.3 mm vs. 0.6 ± 0.3 mm, p = 0.02). Comparing in vitro test specimens, thinning due to high VM loading was 0.9 ± 0.3 mm, versus 0.2 ± 0.0 mm for high JRF loading (p = 0.08); however, the actual material removal rates from the humeral bushings were not different between the two protocols (48 ± 5 mm³ /Mc vs. 43 ± 2 mm³ /Mc, p = 1). Neither loading protocol could produce damage patterns fully representative of the spectrum of damage patterns observed on clinical retrievals. Pre-clinical testing should employ multiple loading protocols to characterize implant performance under a broader spectrum of usage. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1998-2006, 2018.

Development of a hybrid computational/experimental framework for evaluation of damage mechanisms of a linked semiconstrained total elbow system

BACKGROUND

Long-term durability of total elbow arthroplasty (TEA) is a concern, and bearing wear or excessive deformations may necessitate early revision. The current study used experimental wear testing and computational finite element modeling to develop a hybrid computational and experimental framework for the evaluation of TEA damage mechanisms.

METHODS

Three Coonrad-Morrey (Zimmer-Biomet Inc., Warsaw, IN, USA) TEA implants were used for experimental wear testing for 200,000  cycles. Gravimetric measurements were performed before and after the tests to assess the weight change caused by wear. A finite element model of the implant was also developed to analyze ultrahigh-molecular-weight polyethylene (UHMWPE) damage.

RESULTS

High localized contact pressures caused visible creep and plastic flow, deforming bushings and creating unintended UHMWPE-on-UHMWPE contact surfaces where considerably high wear rates were observed. Average experimentally measured vs. model-predicted wear was 9.5 ± 1.0 vs. 14.1 mg for the of the medial bushing, 8.5 ± 1.0 vs. 13.9 mg for the lateral humeral bushing, and 34.1 ± 0.7 vs. 36.9 mg for the ulnar bushings, respectively. Model predicted contact stresses on the surfaces of bushings were substantially higher than the yield limit of conventional UHMWPE (87 MPa for the humeral bushings and 83 MPa for the ulnar bushing).

CONCLUSIONS

Our study discovered that unintended wear at UHMWPE-UHMWPE contact surfaces, "fed" by excessive plastic flow may, in fact, be of more concern than wear that occurs at the intended metal-UHMWPE contact interfaces. Furthermore, formation of high localized contact stresses much above the yield limit of UHMWPE is another likely contributor to bushing failure for this implant.

Mechanical tests, wear simulation and wear particle analysis of carbon-based nanomultilayer coatings on Ti6Al4V alloys as hip prostheses

Carbon-based nanomultilayer coatings were deposited on medical-grade Ti₆Al₄V alloy using a magnetron sputtering technique under a graded bias voltage.

In vitro wear of ultrahigh-molecular-weight polyethylene and vitamin E blended highly cross-linked polyethylene in linked, semiconstrained total elbow replacement prostheses

BACKGROUND

The objectives of this study were to develop a clinically relevant in vitro elbow wear test and to compare the polyethylene wear of 2 total elbow replacement prostheses, one that uses conventional gamma-irradiated polyethylene (CPE) and one that uses vitamin E blended and cross-linked polyethylene (VE-HXPE) bushings.

MATERIALS AND METHODS

The test protocol applied 0° to 85° flexion-extension motions and imposed a constant 4.5° varus malalignment of the ulnar relative to the humeral implant under a variable joint load profile at a frequency of 1 Hz. The implants were tested for 3 million cycles (Mc) in a bovine serum lubricant at 37°C ± 3°C. Polyethylene wear was determined gravimetrically. Wear particles were isolated and characterized.

RESULTS

Clinically relevant polyethylene bushings wear mechanisms were observed. After 3 Mc, the mean CPE wear rate was 9.3 ± 2.8 mm³/Mc, significantly lower than that reported for hip and knee implants but comparable to that of ankle (7.4 ± 1.3 mm³/Mc) devices. The mean VE-HXPE wear rate was 0.8 ± 0.2 mm³/Mc, comparable to that of hip and knees devices. The mean equivalent circle diameter and aspect ratio were 0.17 ± 0.01 µm and 1.99 ± 0.18 for the CPE and 0.15 ± 0.02 µm and 1.81 ± 0.16 for the VE-HXPE particles.

CONCLUSION

The test replicated clinically observed failure modes for CPE devices. The use of VE-HXPE led to an order of magnitude reduction in polyethylene wear. Further clinical evaluation is necessary to determine if this translates into reduced complications of total elbow replacement associated with wear.

Primary Linked Semiconstrained Total Elbow Arthroplasty for Rheumatoid Arthritis: A Single-Institution Experience with 461 Elbows Over Three Decades

BACKGROUND

Elbow arthroplasty is the treatment of choice for end-stage rheumatoid arthritis (RA). The purpose of this study was to determine the long-term outcome of a linked semiconstrained elbow arthroplasty implant design in patients with RA.

METHODS

Between 1982 and 2006, 461 primary total elbow arthroplasties using the Coonrad-Morrey prosthesis were performed in 387 patients with RA. Fifty-five of the arthroplasties were performed to treat concurrent traumatic or posttraumatic conditions. There were 305 women (365 elbows, 79%) and 82 men (96 elbows, 21%). Ten patients (10 elbows) were lost to follow-up, 9 patients (10 elbows) died, and 6 patients (6 elbows) underwent revision surgery within the first 2 years. For the 435 elbows (362 patients, 94%) with a minimum of 2 years of follow-up, the median follow-up was 10 years (range, 2 to 30 years).

RESULTS

At the most recent follow-up, 49 (11%) of the elbows had undergone component revision or removal (deep infection, 10 elbows; and mechanical failure, 39 elbows). Eight additional elbows were considered to have radiographic evidence of loosening. For surviving implants followed for a minimum of 2 years, the median Mayo Elbow Performance Score (MEPS) was 90 points. Bushing wear was identified in 71 (23%) of the surviving elbows with a minimum of 2 years of radiographic follow-up; however, only 2% of the elbows had been revised for isolated bushing wear. The rate of survivorship free of implant revision or removal for any reason was 92% (95% confidence interval [CI] = 88% to 94%) at 10 years, 83% (95% CI = 77% to 88%) at 15 years, and 68% (95% CI = 56% to 78%) at 20 years. The survivorship at 20 years was 88% (95% CI = 83% to 92%) with revision due to aseptic loosening as the end point and 89% (95% CI = 77% to 95%) with isolated bushing exchange as the end point. Risk factors for implant revision for any cause included male sex, a history of concomitant traumatic pathology, and implantation of an ulnar component with a polymethylmethacrylate surface finish.

CONCLUSIONS

Elbow arthroplasty using a cemented linked semiconstrained elbow arthroplasty provides satisfactory clinical results in the treatment of RA with a reasonable rate of survivorship free of mechanical failure at 20 years. Although bushing wear was identified on radiographs in approximately one-fourth of the patients, revision for isolated bushing wear was uncommon.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Total elbow arthroplasty is moving forward: Review on past, present and future

The elbow joint is a complex joint, which, when impaired in function, leads to severe disability. In some cases however, an arthroplasty might be an appropriate treatment. In the past four decades, large steps have been taken to optimize this treatment in order to achieve better post-operative outcomes. To understand these progresses and to discover aspects for upcoming improvements, we present a review on the past developments, the present state of affairs and future developments which may improve patient care further.

Wear particles and ions from cemented and uncemented titanium-based hip prostheses-a histological and chemical analysis of retrieval material

Wear debris-induced inflammation is considered to be the main cause for periprosthetic osteolysis in total hip replacements (THR). The objective of this retrieval study was to examine the tissue reactions and exposure to metal ions and wear particles in periprosthetic tissues and blood samples from patients with titanium (Ti)-based hip prostheses that were revised due to wear, osteolysis, and/or aseptic loosening. Semiquantitative, histological tissue evaluations in 30 THR-patients revealed numerous wear debris-loaded macrophages, inflammatory cells, and necrosis in both groups. Particle load was highest in tissues adjacent to loosened cemented Ti stems that contained mainly submicron zirconium (Zr) dioxide particles. Particles containing pure Ti and Ti alloy elements were most abundant in tissues near retrieved uncemented cups. Polyethylene particles were also detected, but accounted only for a small portion of the total particle number. The blood concentrations of Ti and Zr were highly elevated in cases with high abrasive wear and osteolysis. Our findings indicate that wear particles of different chemical composition induced similar inflammatory responses, which suggests that particle size and load might be more important than the wear particle composition in periprosthetic inflammation and osteolysis. © 2014 The Authors. Journal of Biomedical Materials Research Part B: Applied Biomaterials Published by Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B:709–717, 2015.