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Total Knee Replacement: Evaluating the Local and Systemic Collection and Biological Impact of Cobalt

Wednesday, September 4, 2019

9:00 AM-11:00 AM

BIOMED PhD Research Proposal

Total Knee Replacement: Evaluating the Local and Systemic Collection and Biological Impact of Cobalt and Other Metallic Debris

Christina Arnholt, PhD Candidate
School of Biomedical Engineering, Science and Health Systems
Drexel University

Steven M. Kurtz, PhD
Associate Research Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University

Joseph Sarver, PhD
Teaching Professsor
School of Biomedical Engineering, Science and Health Systems
Drexel University

Total knee arthroplasty (TKA) is one of the most commonly performed orthopedic surgeries, with over 700,000 primary and revision TKA procedures occurring annually in the United States. A TKA replacement consists of a tibial tray which can be composed of either titanium (Ti) or cobalt chromium (CoCr) alloys, a polyethylene insert attached to the tibial tray, a patella, and metallic femoral component that is typically composed of a cobalt chromium alloy.

TKA failure, often requiring a revision procedure, is a multifactorial issue which may be influenced by surgeon technique, implant characteristics, and patient factors. In TKA, failures attributed to metal reactions include hypersensitivity to ionic metals, foreign body reactions to wear debris particles, and responses to metal corrosion products, which can exhibit as hypersensitivity or dermatitis. Postmortem analysis has allowed for extensive analysis into these topics of interest within arthroplasty, helping to elucidate the characteristics of polyethylene wear rates, debris accumulation sites and osteolysis, bone cement interlock, and metal sensitivity within arthroplasty. These methods are still needed as patient satisfaction after receiving TKA remains in the mid to high eighty percentile, with postoperative pain being one of the main revision reasons. Additionally, new concerns regarding cobalt poisoning or cobaltism from THA have arisen.  This condition is associated with severe material loss from the THA devices. Acknowledging that both TKA and THA devices use the same medical cobalt chromium molybdenum, the current concerns and investigations into THA cobaltism create a need to better understand cobaltism within TKA. Initially, this was thought not to occur within total joint arthroplasty because the alloys commonly used rely on the formation of a passive film to prevent degradation of the material, which is one of the critical thermodynamic driving forces behind implant corrosion. However, these films form spontaneously on the surface and are only useful if they can withstand fracture or abrasion by fretting, micro motion, applied stress, or other methods [24]. Although the alloys used in TKA are typically the same as those used in THA, the research focusing on metal release in TKA is considerably more limited.

To address these limitations, the proposal will investigate collected TKA devices and tissues from routine revision TKA surgeries, and post-mortem TKA retrievals.  First we will study the impact of in-vivo use and patient factors on metal release in orthopedic total knee arthroplasty (TKA) devices. The causes for damage of metal components leading to metallic release will be evaluated specifically looking at third body damage using a semiquantitative method.  This method will determine the severity and coverage of third body damage on the bearing surface of the femoral components. Additionally, a statistical model will be used to determine what patient and implant factors influence the amount of third body damage observed. Secondly, we will study metal debris and its characteristics (tissue metal concentration, particle size, and particle dimension) to determine if they are uniform throughout the knee joint capsule. We also wanted to determine if there was a relationship between metal debris, and observed damage on the femoral component or observed biological reactions.  The amount of metallic debris will be identified as a concentration of metal within a specific tissue weight (ug/L or ppb). This tissue will be digested within an acid cocktail and analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). Specific regions being described will be from the synovial capsule collected from potential release zones around the artificial joint: the medial gutter, lateral gutter, supra patella, infra patella, and tibia. Additionally, ASTM: F1877 will be adhered to in order to describe the particle morphology and Feret diameters. The Feret diameter is the mean value of the distance between pairs of parallel tangents to a projected outline of a particle. The morphology will describe the general shape of the debris i.e. spherical or spheroidal; granular, irregular; globular; flakes; fibrillar; sharps or shards. Finally we want to use a biokinetic model to discuss the mobility of cobalt metal ions through the study of peripheral blood metal concentration, peripheral organs (liver, lung, heart, brain), and peri-prosthetic metal concentration allowing us to evaluate if the patient reactions to cobalt metal debris are a more systemic or local burden. The local movement of cobalt from the joint capsule into the blood stream will be modeled using metal concentrations collected for peri-prosthetic tissue from the joint capsule and metal concentrations collected from blood. Additionally, the systemic movement of cobalt will be modeled by measuring metal concentration for peri-prosthetic tissue and metal concentration from peripheral organs.  Using these two distinctive groups, a connection between the peri-prosthetic tissue, the blood, and the peripheral organs metal concentration will be modeled to describe where the major burden of cobalt is within patients who have metallic TKA.

The execution of these aims will provide a direct assessment of metallic debris biological reactions within the body of patients with TKA. Using the semiquantitative third body damage score, a connection will be established between the bearing surface and metallic debris measured within the joint capsule. The analysis of different regions within the joint capsule will provide evidence that the chosen tissues for model analysis are representative of the entire joint capsule. The use of peripheral organs, blood, and peri-prosthetic tissues for metallic concentration measurements will describe both the movement of cobalt through the body of a patient with TKA and where the most significant burden of metallic debris released from TKA is located.

Contact Information

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