Introduction. The release of metal debris and ions has raised concerns in joint arthroplasty. In THA metal debris and ions can be generated by wear of metal-on-metal bearing surfaces and corrosion at modular taper interfaces, currently understood to be mechanically assisted crevice corrosion (MACC) [1]. More recently, inflammatory-cell induced corrosion (ICIC) has been identified as a possible source of metal debris and/or ions [2]. Although MACC has been shown to occur at modular junctions in TKA, little is known about the prevalence of other sources. The purpose of this study was to determine the sources of metallic debris and ion release in long-term implanted (in vivo > 15y) TKA femoral components. Specific attention was paid to instances of ICIC as well as damage at the implant-bone interface. Methods. 1873 retrieved TKA components were collected from 2002–2013 as part of a multi-center, IRB-approved retrieval program. Of these, 52 CoCr femoral condyles were identified as long term TKA (Average: 17.9±2.8y). These components were predominantly revised for loosening, PE wear and instability. 40/52 of the components were primary surgeries. Components were examined using optical microscopy to confirm the presence of 5 damage mechanisms (polyethylene failure, MACC corrosion of modular tapers, corrosion damage between cement and backside, third-body wear, and ICIC). Third-body wear was evaluated using a semi-quantitative scoring method based on the percentage of damaged area. A score of 1 had minimal damage and a score of 4 corresponded to severe damage. Polyethylene components were scored using the Hood method and CoCr components were scored similarly to quantify metal wear. The total area damaged by ICIC was quantified using photogrammetry. Images were taken using a digital SLR with a calibrated ruler in the same focal plane. Using known pixel dimensions, the ICIC damaged area was calculated. Results. Surface damage indicative of corrosion and/or CoCr debris release was identified in 92% (n=48) of the components. Third-body wear was the most prevalent damage mechanism identified in 77% (n=40/52; Figure 1) of these components. ICIC was identified in 38% (n=20/52, figure 2) of the components. The polyethylene damage scores were predominantly a score of 4 out of a maximum score of 4 (89%). The corresponding femoral components had moderate to severe damage scores, with 39% with a score of 2, 37% scoring 3 and 22% scoring 4 out of a maximum score of 4. The total ICIC damaged area was an average of 0.11 ± 0.12 mm. 2. (Range: 0.01–0.46mm. 2. ). Discussion. In this study, we sought to identify mechanisms that could lead to the release of CoCr debris/ions in TKA. Five different mechanisms of potential metal release were observed. The most prevalent were third-body wear and ICIC damage. However the clinical implications remain unclear for several mechanisms because none of the devices were revised due to adverse local tissue reactions or biologic reactions to CoCr. Although we documented the prevalence of each damage mechanism, the quantity of metal removal was not investigated, warranting future studies

Revision of fractured ceramic-on-ceramic total hip replacements with a cobalt-chromium (CoCr) alloy-on-polyethylene articulation can facilitate metallosis and require further expensive revision surgery [1–3]. In the present study, a fifty-two year old male patient suffered from fatal cardiomyopathy after undergoing revision total hip arthroplasty. The patient had received a polyethylene-ceramic acetabular liner and a ceramic femoral head as his primary total hip replacement. The polyethylene-ceramic sandwich acetabular liner fractured in vivo after 58 months and the patient underwent his first revision surgery where he received a Vitamin E stabilized acetabular Polyethylene (PE) liner and a CoCr alloy femoral head with documented synovectomy at that time. After 15 months, the patient was admitted to hospital in cardiogenic shock, with retrieval of the bearing components. Before the second revision surgery, peak serum cobalt levels measured 6,521 μg/L, 78-times greater than serum cobalt levels of 83μg/L associated with cobalt poisoning [4]. Serum titanium levels found in the patient measured 17.5 μg/L) normal, healthy range 0–1.4 μg/L). The retrieved CoCr alloy femoral head had lost a total of 28.3g (24% or an estimated amount of 102 × 10. −9. wear particles (∼2 μm diameter) [1]) within 16 months of in vivo service. Despite initiating a cobalt chelating therapy, the patients' cardiac left ventricular ejection fraction remained reduced at 6%. This was followed by multi-organ failure, and ultimately the patient passed away shortly after being taken off life support. Embedded ceramic particles were found on the backside and articular surfaces of the Vitamin E-stabilized PE acetabular liner. Evidence of fretting wear on the titanium (Ti) alloy acetabular shell was present, possibly explaining the increased serum Ti levels. Scanning electron microscopy and energy dispersive X-ray analyses confirmed Ti alloy transfer on the embedded ceramic particles on the backside PE liner surface and CoCr alloy transfer on the embedded ceramic particles on the articular PE liner surface. A fractured ceramic-on-ceramic total hip replacement should not be revised to a CoCr alloy-on-polyethylene articulation irrespective of concurrent synovectomy [5] as it can cause severe, third-body wear to the CoCr alloy femoral head that can lead to metallosis with fatal, systemic consequences

Introduction. From a tribological point of view and clinical experience, a ceramic-on-ceramic bearing represents the best treatment option after rare cases of ceramic component fracture in total hip arthroplasty (THA). Fractured ceramic components potentially leave small ceramic fragments in the joint capsule which might become embedded in PE acetabular liners. Purpose. This in vitro study compared for the first time the wear behaviour of femoral ball heads made of ceramic and metal tested with PE liners in the presence of ceramic third-body debris. The contamination of the test environment with third-body ceramic debris, insertion of ceramic fragments into the PE liners and implementation of continuous subluxation simulated a worst-case scenario after revision of a fractured ceramic component. Materials and Methods. Ceramic femoral ball heads (ϕ 32 mm) made of alumina matrix composite (AMC; BIOLOX® delta, CeramTec, Germany) were tested in combination with PE and cross-linked liners and compared to metal femoral ball heads (CoCrMo) of the same diameter. All PE liners were fixed into Ti-6Al-4V metal shells by conical fixation as intended for clinical use. The tests were performed based on ISO 14242-1 utilizing a hip simulator (EndoLab, Germany). Alumina ceramic debris (BIOLOX® forte, CeramTec, Germany) of about 2 mm diameter (maximum 5 mm) were inserted into the PE liners in predefined specific points corresponding to the main load transfer area before the test. The acetabular liners were tested at an inclination of 45° in the medial-lateral plane with the specimens placed in an anatomically correct position. During the test, additional alumina ceramic debris was introduced into the articulation area as a part of the test fluid (calf serum) used in the simulator test chambers. All specimens were tested up to 5 million cycles. Damages to the surfaces of the materials were assessed visually. The wear of the femoral ball heads was measured gravimetrically. Results. High wear rates were found for metal femoral ball heads, being 1,010 times higher when compared to ceramic femoral ball heads tested with XPE liners and 560 times higher when compared to ceramic femoral ball heads tested with conventional PE liners. The conventional and crosslinked PE liners used in combination with metal femoral ball heads clearly exhibited a scratched surface, whereas the surface of the liners tested with ceramic femoral ball heads exhibited significantly less scratching. Discussion and Conclusion. This study demonstrates that apart from the recommended ceramic-on-ceramic option also ceramic-on-PE and ceramic-on-crosslinked PE bearing couples may be a viable treatment option after fracture of a ceramic component. The use of a ceramic femoral ball head after fracture of a ceramic articulation component minimizes wear and wear-related complications caused by third-body wear. Based on the results of this in vitro study and clinical findings, the use of a metal femoral ball head in articulation with any PE liner after a ceramic fracture is contraindicated

INTRODUCTION. Total knee arthroplasty (TKA) is typically performed using cement to secure the prosthesis to bone. There are complications associated with cementing that include intra-operative hypotension, third-body abrasive wear, and loosening at the cement interfaces. A cementless prosthesis using a novel keeled trabecular metal tibial baseplate was developed to eliminate the need for cementing the tibial component in TKA. METHODS. A retrospective chart review was performed on patients who underwent TKA using cementless tibial and femoral components between August, 2013 and January, 2014. Patients with minimum two-year follow-up including radiographs were included in the analysis. Patient demographics as well as preoperative and postoperative range of motion (ROM) and function were measured using the Knee Society Scoring system (KSS). Post-operative radiographs were assessed for signs of osteolysis, loosening, or subsidence. Paired T-tests were used to identify differences in preoperative and postoperative ROM and KSS. RESULTS. Thirty-three patients underwent 48 TKAs in the study period. Of those, 20 patients (29 knees) completed two-year follow-up. The mean patient age was 69.0 ±8.4 years and mean BMI was 29.9 ±4.3. The average time of follow-up was 24.6 months (range 24–29). Preoperative ROM was on average 4.3–117.3°±6.7 and the preoperative KSS knee scores and functional scores were 43.8 ±8.6 and 49.8 ±12.6, respectively. Postoperatively, there were statistically significant improvements in ROM (0–130.7°±7.3), and postoperative KSS knee (98.4 ±3.2) and functional scores (99.3 ±2.6), at two years, respectively. None of the radiographs demonstrated evidence of osteolysis, loosening, migration, or subsidence. DISCUSSION and CONCLUSION. The two-year results of TKA utilizing a cementless tibial baseplate demonstrate excellent results in terms of knee ROM and function. The radiographic evidence of osteointegration without evidence of loosening, subsidence, or migration of the tibial components is promising. Further follow up is necessary to ensure that these implants will provide a satisfactory long-term alternative to cement fixation

Introduction. Previous studies of CoCr alloy femoral components for total knee arthroplasty (TKA) have identified 3. rd. body abrasive wear, and apparent inflammatory cell induced corrosion (ICIC) [1] as potential damage mechanisms. The association between observed surface damage on the femoral condyle and metal ion release into the surrounding tissues is currently unclear. The purpose of this study was to investigate the damage on the bearing surface in TKA femoral components recovered at autopsy and compare the damage to the metal ion concentrations in the synovial fluid. Methods. 12 autopsy TKA CoCr femoral components were collected as part of a multi-institutional orthopedic implant retrieval program. The autopsy components included Depuy Synthes Sigma Mobile Bearing (n=1) and PFC (n=1), Stryker Triathlon (n=1) and Scorpio (n=3), and Zimmer Nexgen (n=4) and Natural Knee (n=2). Fluoro scans of all specimens prior to removal was carried out to assure no signs of osteolysis or aseptic loosening were present. Third-body abrasive wear of CoCr was evaluated using a semi-quantitative scoring method similar to the Hood method [2]. ICIC damage was reported as location of affected area and confirmed using a digital optical microscope with 4000X magnification. Synovial fluid was aspirated from the joint capsule prior to removal of the TKA device. The synovial fluid was spun at 1600 rpm for 20 minutes in a centrifuge with the cell pellet removed. The supernatant was analyzed in 1 mL quantities for ICP-MS (inductively coupled plasma mass spectrometry) by Huffman Hazen Laboratories. Data was expressed as ppb. Results. Mild to severe damage (Damage Score ≥ 2) was observed on 92% of the components in at least one quadrant, with no severe damage (Damage Score = 4) observed. ICIC damage was observed on three components in three different regions (the posterior lateral, anterior, and medial bearing surface). These observations were confirmed with digital optical microscopy, where we observed as interconnecting pits and indentations with a spiraling or trailing region, consistent with prior observation of ICIC in retrievals (Figure 1). Cobalt was detected in 7 cases, however the metal levels were not as high as levels observed in patients with a failed joint replacement (Table 1). There was no correlation between the metal ion concentration and the damage score on the CoCr femoral condyle. Discussion. This study documents the damage mechanics and associated metallic release into the synovial fluid of “well-functioning” TKA components retrieved at autopsy. It has been suggested that ICIC damage is actually damage from electrocautery during surgery. However, we observed ICIC damage on autopsy retrievals in which the use of electrocautery is unlikely. The damage mechanisms observed on the autopsy TKA components were similar but less severe compared to mechanisms observed in long-term TKA components from revision surgery [1]. More research is needed to better understand the metal release from CoCr femoral components and periprosthetic tissue reactions in TKA

Introduction. Previous studies of long-term CoCr alloy femoral components for TKA have identified 3rd body abrasive wear and inflammatory cell induced corrosion (ICIC). The extent of femoral condyle surface damage in contemporary CoCr femoral components is currently unclear. The purpose of this study was to investigate the prevalence and morphology of damage (3rd body scratches and ICIC) at the bearing surface in retrieved TKA femoral components from contemporary designs. Methods. 308 CoCr femoral TKA components were collected as part of an ongoing, multi-institutional orthopedic implant retrieval program. The collection included contemporary designs from Stryker (Triathlon n=48, NRG n=10, Scorpio n=31), Depuy Synthes (PFC n=27) and Zimmer (NexGen n=140, Persona n=1) and Biomet (Vanguard n=51). Hinged knee designs and unicondylar knee designs were excluded. Components were split into groups based on implantation time: short-term (1–3y, n=134), intermediate-term (3–5y, n=73) and long-term (6–15y, n=101). Each grouping was mainly revised for instability, infection and loosening. Third-body abrasive wear of CoCr was evaluated using a semi-quantitative scoring method similar to the Hood method (Figure 1). A score of 1 had minimal damage and a score of 4 corresponded to damage covering more than 50% of the evaluated area. ICIC damage was reported as location of affected area. A white light interferometer (Zygo New View 5000) was also used to analyze the topography of severe damage of the bearing surface. For this analysis, three representative components from each cohort were selected and analyzed in three locations on the apex of the bearing surface. We analyzed the following roughness parameters: Ra, Rsk, and Rku. Results. On the CoCr bearing surface, the primary damage mechanisms were large scratches, small random scratches, and ICIC damage (Figure 2). Mild to severe damage (Damage Score ≥ 2) was observed in 96% of the short-term, 98% intermediate-term and 94% of long-term components. Severe damage (Damage Score = 4) was observed in 43% of the short-term, 50% intermediate-term and 56% of long-term components. ICIC damage observed on a portion of the bearing surface was detected in 43% of the short-term components, 30% of the intermediate-term components and 26% of the long term components. Apparent ICIC damage on the bearing and/or a non-bearing region of the component was observed in 85% of the short-term components, 75% of the intermediate-term components and 80of long-term TKA components. The Ra, Rsk, and Rku were similar between cohorts (Table 1). Discussion. Abrasive wear of the femoral components was frequently observed in retrieved contemporary femoral components for TKA, regardless of their implantation time, and can most likely be attributed to third body damage caused by bone or bone cement debris. The prevalence of severe CoCr damage scores was highest in the long-term cohort, while the appearance of ICIC damage was lowest in the long-term cohort. Surface roughness parameters were similar in all three cohorts suggesting that the mechanism for this damage is comparable throughout the first 15 years of service. Future work is necessary to quantify the in vivo release of CoCr from abrasive wear and corrosion mechanisms, and the effects of increased surface roughness on wear of the polyethylene counter face

Damage to metal-on-metal bearings (MOM) has been varyingly described as “edge wear,” third-body abrasive wear and “rim-damage” (1–4). However, no distinction has been made between any of these proposed wear mechanisms. The goal of this study was to discover what features might differentiate between surface damage created by either 2-body or 3-body wear mechanisms in MOM bearings. The hypotheses were that surface damage created by impingement of the cup rim (2-body wear) would be i) linear on the micro-scale, ii) reveal transverse striations (in direction of the sliding rim), iii) have either no raised lip or have a single lip along one side of the track, and iv) have an asymmetrical surface profile across the track width. Five cases with 28 mm MOM, five of 34–38 mm MOM, and five of 50–56 mm diameter were studied (N = 15). The main wear zone (MWZ) was measured in each MOM head and the number of 2-body wear tracks recorded in the non-wear (NWZ) and main wear zone (MWZ). Bearing damage was examined using a white-light interferometer (Zygo Newview 600; 5x lens) and a scanning electron microscope (Zeiss MA15). The depths and slopes were assessed across the width of the damage tracks. Thirteen of the 15 MOM bearings showed wear tracks that exhibited all four of the hypothesized 2-body wear characteristics. These wear tracks will be referred to as “micro-segments”. While micro-segments visually appeared linear, microscopically they revealed a semi-lunar edge coupled with transverse striations leading to a linear edge. This indicated that during impingement episodes, the cup rim ploughed material from the CoCr surface at the semi-lunar edge (Fig. 1), thereby creating the abruptly raised lip on the linear edge of the track. This “snow plough effect” and its distinct edge effect can account for the asymmetrical surface profile. A different type of 2-body wear was identified and referred to as “furrows”. Furrows also visually appeared linear visually, but microscopically revealed longitudinal striations and a symmetrical surface profile (Fig. 2). Furrows had lips raised on both sides of the track, but not circumscribing the terminal ends of the track. Instead, the ends of the furrows are tapered smooth transitions to the articular surface. Thus, 2-body tracks were found to be distinguishable from 3-body tracks (micro-grooves) and were classified as either micro-segments or furrows. Micro-segements supported hypotheses 1–3 and provided a clearer definition for hypothesis-4, while furrows only supported hypothesis 1. The divergence in features between micro-segments and furrows allude to different interactions between the bearing and cup rim that led to each type of track. While these data represent a small set of cases (n = 15) this evidence shows for the first time what was previously only suspected (2), that the CoCr rim can routinely create 2-body wear damage mechanisms in MOM femoral heads