Articulation of an alumina-zirconia composite ceramic against living cartilage - An in vitro wear test.

BACKGROUND: There is interest in minimally invasive solutions that reduce osteoarthritic symptoms and restore joint mobility in the early stages of cartilage degeneration. The aim of the present study was to evaluate an alumina-zirconia composite (AZC) as a counterface for articulation against live cartilage explants in comparison to the clinically relevant cobalt-chromium (CoCrMo) alloy. METHODS: A four-station bioreactor designed to articulate against living tissue in an incubator was used for testing. Twelve 32 mm AZC and twelve 32 mm CoCrMo femoral heads with equal surface roughness made up both test groups. Each head articulated against a cartilage disk harvested from stifle joints of 24-week old steers. Test samples and free-swelling control cartilage samples were cultured in Mini ITS medium. Testing was conducted 3 h daily over 10 days applying a contact load of approximately 2 MPa. PG/GAG and hydroxyproline were analyzed using biochemical assays. Additionally, chondrocyte survival and Mankin score analyses were performed on histological slides. RESULTS: Cells stayed alive during the course of the experiment, with cell survival values close to 80% at test completion in the superficial zone. There was no significant difference between AZC and free-swelling control tissue. However, cell count values were inferior for CoCrMo (p = 0.003). Tested tissue suffered mostly structural abnormalities. The PG/GAG content in medium was not different between CoCrMo and AZC (p = 0.315); however, the hydroxyproline release into medium was nearly 30% higher for CoCrMo (p = 0.024). CONCLUSION: Based on average values, AZC induces less cell and tissue damage than CoCrMo. However, only the hydroxyproline measurements reached statistical significance, partially due to substantial scatter within both groups.

Effect of highly purified capsaicin on articular cartilage and rotator cuff tendon healing: An in vivo rabbit study.

Highly purified capsaicin has emerged as a promising injectable compound capable of providing sustained pain relief following a single localized treatment during orthopedic surgical procedures. To further assess its reliability for clinical use, the potential effect of highly purified capsaicin on articular cartilage metabolism as well as tendon structure and function warrants clarification. In the current study, rabbits received unilateral supraspinatus transection and repair with a single 1 ml injection of capsaicin (R+C), PEG-only placebo (R+P), or saline (R+S) into the glenohumeral joint (GHJ). An additional group received 1 ml capsaicin onto an intact rotator cuff (I+C). At 18 weeks post-op, cartilage proteoglycan (PG) synthesis and content as well as cell viability were similar (p>0.05) across treatment groups. Biomechanical testing revealed no differences (p>0.05) among tendon repair treatment groups. Similarly, histologic features of both cartilage and repaired tendons showed minimal differences across groups. Hence, in this rabbit model, a single injection of highly purified capsaicin into the GHJ does not induce a deleterious response with regard to cartilage matrix metabolism and cell viability, or rotator cuff healing. These data provide further evidence supporting the use of injectable, highly purified capsaicin as a safe alternative for management of postoperative pain following GHJ surgery.

BMP-7 protects against progression of cartilage degeneration after impact injury.

In vivo studies were used to characterize a model of cartilage injury leading to osteoarthritis progression in the medial femorotibial joint of sheep. In three subsequent studies, bilateral impact injuries were created and one joint received intraarticular injections of 340 microg of rhBMP-7 protein in a collagen particle carrier while the contralateral knee received the vehicle alone. Sheep were allocated to three groups that received intraarticular injections on day 0 (group A), 21 (group B), or 90 (group C) after experimental knee injury. In each group the, joints were evaluated for signs of osteoarthritis progression 90 days after the last treatment using India ink stained area, OARSI histological scoring, cartilage sGAG content, immunostaining for apoptosis (TUNEL), caspase-3, collagen degradation (Col 2 3/4C short collagen epitope), and the endogenous (pro-) form of BMP-7 protein. Knee joints that received rhBMP-7 immediately after injury had small focal lesions at the injury site that did not progress into the surrounding cartilage. Joints that received BMP-7 3 weeks after injury were improved and had limited progression compared to controls, but joints that received the protein 12 weeks after injury had no statistically significant improvement. These studies suggest that BMP-7 may be chondroprotective after traumatic injury in patients if it is administered within 3 to 4 weeks of the index injury. The mechanism of protection after sublethal injury appeared to be an increased survival of chondrocytes that are able to participate in the repair process.