Abstract
Introduction:
Unicompartmental knee arthroplasty (UKA) has been used in the past decades to treat progressive cartilage degeneration in a single compartment. Concern has been raised over the rate of revision procedures for polyethylene wear and osteoarthritic progression into the adjacent compartment. Few studies have examined the pathology of cartilage degeneration in the setting of UKA. This study aims to investigate the viability of knee chondrocytes introduced to high and low concentrations of orthopaedic wear debris particulate.
Methods:
Normal human articular chondrocytes (nHAC-Kn) were expanded in DMEM/F12 containing 10% FBS, 1% Penicillin/Streptomycin (Pen/Strp), and 50 μg/mL ascorbic acid (Asc). 24 hours prior to the start of the experiment, cells were seeded on 96-well plates at a density of 3500 cells/cm2 and exposed to DMEM/F12 containing 5% FBS, 1% Pen/Strp, and 50 μg/mL Asc. Particles (equivalent circle diameter range: 0.2–7 μm) at a low dose of 100: 1 (particles: cells) and high dose 1000: 1 (particles: cells) were introduced to treatment wells (n = 6). Control wells (n = 6) contained particles with no cells.
Treatment groups included high and low doses of TiAl6V4 alloy, 316L Stainless Steel, and Co-Cr-Mo alloy. At days 1, 3, 5, and 7, cells were assayed with a 3-(4,5-Dimethylthiazol-2-yl)-2,5-dyphenyltetrazolium bromide (MTT) assay for determination of cell viability. Light microscopy was performed at each timepoint to assess change in cell morphology.
Results:
All groups displayed a minor decrease in cell viability after 24 hours of exposure to particles. Similarly, a second distinct decrease in viability occurred at the day 3 timepoint. Days 5 and 7 yielded little change in cell viability. Results are displayed in Figure 1. Observations of light microscopy revealed cells may actively engulf particles over time. Images show particle concentrations at the same locations as chondrocytes with few particles present between cells.
Conclusions:
Wear debris has been implicated as a contributing source to osteolysis and component loosening. A potential effect on the cellular level can ultimate lead to effects on the entire tissue and complications on the clinical level. A decrease in chondrocyte viability has been shown in response to the presence of particulate wear debris. Our results showed decreases in cell viability were most noticeable between 24 and 72 hours after introduction to particles. Chondrocyte death may contribute to progression of cartilage degeneration into healthy compartments of the knee. Continued experiments are underway further characterizing chondrocyte response to wear debris particulate with respect to protein and gene expression in an extended 7 day in vitro culture.
