Articular cartilage damage is a primary outcome of pre-clinical and clinical studies evaluating meniscal and cartilage repair or replacement techniques. Recent studies have quantitatively characterized India Ink stained cartilage damage through light reflectance and the application of local or global thresholds. We develop a method for the quantitative characterisation of inked cartilage damage with improved generalisation capability, and compare its performance to the threshold-based baseline approach against gold standard labels. The Trainable WEKA Segmentation (TWS) tool (Arganda-Carreras et al., 2017) available in Fiji (Rueden et al., 2017) was used to train two separate Random Forest classifiers to automatically segment cartilage damage on ink stained cadaveric ovine stifle joints. Gold standard labels were manually annotated for the training, validation and test datasets for each of the femoral and tibial classifiers. Each dataset included a sample of medial and lateral femoral condyles and tibial plateaus from various stifle joints, selected to ensure no overlap across datasets according to ovine identifier. Training was performed on the training data with the TWS tool using edge, texture and noise reduction filters selected for their suitability and performance. The two trained classifiers were then applied to the validation data to output damage probability maps, on which a threshold value was calibrated. Model predictions on the unseen test set were evaluated against the gold standard labels using the Dice Similarity Coefficient (DSC) – an overlap-based metric, and compared with results for the baseline global threshold approach applied in Fiji as shown in Figures 1 and 2.Objectives
Methods
Hemiarthroplasty is an attractive technique for young and active patients as it preserves more bone stock. Polycarbonate urethane (PCU) has recently been introduced as an alternative bearing material. DSM Biomedical BV (Geleen, The Netherlands) has modified Bionate® PCU 80A (80AI) with C18 groups and produce Bionate® II PCU 80A (80AII) to create a different biointerface and enhance its tribological properties. The aim of this study was to compare friction performance of the articulation of the cartilage against 80AI and 80AII in various lubricants. A customised multidirectional pin-on-plate reciprocating rig (Fig. 1) was used to perform friction tests of ovine femoral condyles as they articulated against PCU 80A discs (diameter 38 mm, thickness 3.2 mm). The average surface roughness of the cartilage and the PCU discs was approx. 450 nm and 10 nm respectively. 30% (v/v) bovine calf serum (BCS) and bovine synovial fluid (BSF) were used as lubricants. Prior to testing, each disc was fully hydrated in its test lubricant for 6 days. During testing, a static compressive load of 20 N was applied (an average stress of approx. 0.95 MPa). The sliding distance was 25 mm with ±15° rotation over the length of the stroke to produce cross shear. Each test lasted 15 h at a frequency of 1 Hz. Lubricant was kept at 37±1 °C throughout testing. The friction force was measured using full-bridge circuit strain gauges (Fig. 1).Introduction
Materials and Methodology
