In patients who underwent total hip arthroplasty, a body-mass index of 25 or greater was associated with subsequent hospitalization for thromboembolism. Pneumatic compression in patients with a body-mass index of less than 25 and prophylaxis with warfarin after discharge were independently protective against thromboembolism.

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Experimental photodynamic therapy (PDT) has recently been adapted for the treatment of inflammatory and rheumatoid arthritis. The biodistribution of benzoporphyrin derivative monoacid ring A (BPD-MA) and the effect of percutaneous light activation via intra-articular bare cleaved optical fibers was investigated using a rabbit-antigen-induced arthritis model. Qualitative evaluation of intra-articular photosensitizer clearance was performed with laser-induced fluorescence from 0 to 6 h following intravenous injection. The compound was rapidly taken up within the joint and then cleared steadily over the 6 h interval. Biodistribution was determined by fluorescence microscopy and spectrofluoroscopic extraction techniques 3 h following intravenous injection of 2 mg/kg BPD-MA. The biodistribution study demonstrated elevated levels of BPD-MA in synovium (0.35 microgram/g) and muscle (0.35 microgram/g). Fluorescence microscopy demonstrated presence of the compound within pathologic synovium but absence of the photosensitizer within meniscus, ligament, bone and articular cartilage. Tissue effects were evaluated histologically at 2 and 4 weeks posttreatment. BPD-MA-mediated PDT caused synovial necrosis in the region of light activation in 50% of treatment knees at 2 weeks and 43% at 4 weeks. No damage to nonpathologic tissues was observed. These studies indicate that selective destruction of synovium can be achieved by the light-activated photosensitizing agent BPD-MA without damage to articular cartilage or periarticular soft tissues. PDT needs to be further evaluated to optimize treatment parameters to provide for a new minimally invasive synovectomy technique.

A new, near-infrared, pulsed holmium laser (wavelength, 2.1 microns; pulse duration, 400 microseconds) was used to ablate bovine articular cartilage and meniscal fibrocartilage. Microscopic examination revealed zones of thermal damage extending 550 microns from ablation sites. Ablation rates were measured with a mass loss technique. Above threshold, mass removal rates were proportional to laser radiant exposure. Threshold radiant exposure for ablation was 50 J/cm2 for articular cartilage and 11 J/cm2 for meniscal fibrocartilage. Because the holmium laser can precisely and rapidly resect cartilaginous tissues with only moderate necrosis, function in a saline environment in direct contact with tissue, and be transmitted through conventional optical fibers, it has the potential to become a useful tool for the precise arthroscopic removal of intraarticular tissue.