Clinical StudyPolyethylene wear and rim fracture in total disc arthroplasty
Introduction
The origins of disc arthroplasty as an alternative to fusion can be traced back to the 1960s, when Fernström described the first intervertebral prosthesis to relieve pain and restore motion of a diseased functional spinal unit as a potential alternative to fusion [1]. However, it was not until the 1980s that disc replacements began to adopt the bearing and fixation technologies that had been successfully established in total hip and knee replacements. One such design, the SB Charité III (DePuy Spine, Raynham, Massachusetts), consists of metallic (CoCr) alloy end plates, articulating against a central core of ultra-high-molecular-weight polyethylene (hereafter, polyethylene) [2]. Articulation between metallic and polyethylene components has been the cornerstone of hip replacements since 1962 [3], and remains the standard of care in total joint procedures even today [4].
Despite the established track record of polyethylene as a highly successful biomaterial, wear and surface damage are well recognized to potentially limit the longevity of orthopedic implants [4], [5]. Specifically, particulate wear debris can stimulate an inflammatory response, resulting in osteolysis and late loosening of a hip or knee prosthesis [5]. By contrast, the clinical relevance of polyethylene wear in the lumbar spine remains poorly understood. Proponents of artificial discs have theorized that, because the relative motions of the implant components were much lower than in hip or knee replacements, and because the intradiscal space was not a synovial joint, polyethylene wear debris would likely not be clinically significant for the lumbar spine [6]. However, recent case studies documenting wear, osteolysis, and other implant-related complications suggest that polyethylene damage may be a potential clinically relevant failure mode for lumbar artificial disc replacements [7], [8], [9], [10], [11].
The negative clinical consequences associated with the polyethylene wear have been well documented from the study of retrieved hip and knee implants [4]. In contrast, with the exception of previous individual case studies [7], [8], the detailed analysis of retrieved total disc replacements (TDRs) remains largely unexplored. As a result, many questions surrounding the wear and damage mechanisms of polyethylene TDRs remain unknown. The current lack of fundamental, mechanistic knowledge surrounding the clinical performance of polyethylene in the spine is particularly troubling, in light of the life-threatening risks that a patient may incur during TDR revision surgery [9], [10].
In collaboration with clinical partners, in 2004, we established a repository of retrieved TDRs to better understand implant wear and its relationship to clinical performance in the spine. Our total disc repository includes implants of a variety of designs and manufacturers, and is open to collaboration with orthopedic and spine surgeons from around the world. An institutional review board approved the retrieval collection, storage, and handling protocols for our repository.
In this international multicenter retrieval study, we performed detailed analyses of explanted polyethylene TDRs to quantify the wear and mechanisms of surface damage. We also sought to compare the wear mechanisms in polyethylene TDR components with those previously observed in hip and knee replacements. In this research, we addressed the following questions: 1) Are the wear and fracture mechanisms in polyethylene TDR components similar to those from hip and knee arthroplasty? 2) What is the magnitude and rate at which polyethylene wear of TDRs occurs in vivo?
Section snippets
Methods and materials
Twenty-one implants were analyzed from 18 patients (12 female, 6 male) undergoing TDR revision surgery. The average patient age at the time of implantation was 39 years (range: 22 to 49 years). The artificial discs were all of the SB III Charité design, which was commercially introduced to Europe outside of the Charité Hospital in Berlin starting in 1989 [2]. Nineteen of 21 revisions were performed in the Netherlands, and one implant was retrieved in England and the United States, respectively.
Results
Microscopic, multidirectional scratching was observed on the central bearing surfaces of all polyethylene cores, consistent with an adhesive/abrasive wear mechanism. There was also evidence of macroscopic rim damage, including radial cracking (Fig. 2), transverse cracking (Fig. 1, Fig. 3), burnishing, plastic deformation, and third-body damage. The wear and surface damage assessments for the 21 retrievals are summarized in Table 2.
A broad spectrum of fatigue and fracture modes was manifested in
Discussion
The retrieved polyethylene implants in this study exhibited wear and damage mechanisms previously observed in both hip and knee replacements. In the central, dome region of the implants, microscopic multidirectional scratches were consistent with the crossing-shear wear patterns characteristic of hip replacements [12], [13]. Like hip replacements, the dome penetration was found to increase with implantation time. The rate of head penetration in hip replacements generally decreases with
Conclusions
We quantitatively analyzed the long-term polyethylene failure mechanisms of 21 polyethylene TDR components implanted for up to 16 years. The observations in this study supported the following principal findings:
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Measurable wear was detected in all of the retrieved polyethylene total disc replacement components in this study.
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The TDRs displayed surface damage observed previously in both hip and knee replacements. In the center of the core, the adhesive/abrasive wear mechanisms were similar to hip
References (26)
- et al.
Analysis of a retrieved polyethylene total disc replacement component
Spine J
(2005) - et al.
Lubrication and wear of ultra-high molecular weight polyethylene in total joint replacements
Tribology International
(1998) - et al.
A literature review of the association between wear rate and osteolysis in total hip arthroplasty
J Arthroplasty
(2002) Arthroplasty with intercorporal endoprosthesis in herniated disc and in painful disc
Acta Chir Scand Suppl
(1966)History
Total hip replacement by low-friction arthroplasty
Clin Orthop
(1970)The UHMWPE handbook: ultra-high molecular weight polyethylene in total joint replacement
(2004)- et al.
Implant wear
(2001) - et al.
Biomechanics of total disc replacement
Revision of a Charite artificial disc 9.5 years in vivo to a new Charite artificial disc: case report and explant analysis
Eur Spine J
(2005)
Complications of artificial disc replacement: a report of 27 patients with the SB Charite disc
J Spinal Disord Tech
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2022, Clinical BiomechanicsCitation Excerpt :Although other clinical studies did not explicitly mention ceramic fractures, it is possible that fractures occurred but were counted as adverse events and included in the overall complication rates. However, failures of non-ceramic materials have been reported in articulating and non-articulating TDRs: fractures of polyethylene cores (Kurtz et al., 2007) and rubber tears (Fraser et al., 2004) in lumbar TDRs, cracking of a polyurethane sheath (Fan et al., 2012) tear of a sheath (Clark et al., 2020), disintegration of sheath and artificial annulus (Xia and Winder, 2019) and defect of the artificial annulus-fibers with migration of the artificial core (Brenke et al., 2015) for cervical TDRs. The results of this review suggest that wear rates of TDRs with ceramic articulating surfaces are within appropriate range, but evidence in literature is sparse.
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2022, Spine JournalCitation Excerpt :Moreover, although aseptic osteolysis may result in loosening and subsequent instability, cases of wear-particle inflammation without loosening have been reported [77], leading us to classify it as a separate failure category. Given the average age of approximately 45 both in our series and in our review of the literature, it is possible that TDA wear may become a more prevalent complication in the coming years with longer-term follow-up as patients begin to outlive their prostheses [18]. Radiographic wear without osteolysis may be observed in the asymptomatic patient, but also may be revised with anterior or posterior fusion versus TDA revision.
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FDA device/drug status: approved for this indication (SB Charité III).
The establishment of the total disc replacement repository and this study were supported by a research grant from Medtronic Sofamor Danek.