An infection inhibiting urinary catheter material.

Catheter associated bacteriuria is a common infection in hospitals and nursing homes. An infection inhibiting catheter material for fabricating urinary catheters is being developed. The material consists of silicone rubber elastomer compounded with chlorhexidene gluconate (CHG) matrix. The antibiotic is released in sustained fashion over at least 4 weeks. A method was established for adding CHG to silicone rubber. To protect the CHG, it is suspended in a water soluble wax that also modulates CHG release from the elastomer. It was found that CHG is randomly dispersed in the elastomer and that the primary release mechanism is by diffusion. The antibacterial activity of the material with a range of 0.1 to 5% CHG by weight was examined using in vitro zone inhibition testing. The new material demonstrated significant inhibitory activity against three pathogens tested (Escherichia coli, Proteus mirabilis and Staphylococcus epidermidis.). The release rate of CHG was measured in vitro using high performance liquid chromatography (HPLC). With 5% CHG loading, the antibiotic was released at a steady rate of approximately 8.4 mg/cm2/day for periods extending beyond 4 weeks. This new material for urinary catheters has the potential to provide protection against infection and surface colonization.

Development of a magnetically operated artificial urethral sphincter. Chronic effects of compression on the skin structure and blood flow.

The artificial urethral sphincter (AUS) has been in clinical use for more than 20 years. Currently available AUS devices, however, are difficult to use and not entirely reliable. A magnetically operated AUS is currently under the development. Although the skin between the magnets will be compressed all day long, little information exists on the effects of chronic pressure on the skin structure and blood flow. In five miniature pigs, two internal magnets and one control metal disk were implanted subcutaneously at three different positions, and external magnets with differing magnetic forces were applied to the skin overlying the internal magnets for six weeks. In four pigs, the skin blood flow was measured by a laser Doppler flow meter applying different pressures. Compression of 10 mmHg preserved normal skin morphology in all but one animal where blood flow had not recovered 2 weeks after surgery. Compression of 20 mmHg for 6 weeks, however, produced pressure ulcers in all five cases (p < 0.05 vs. 10 mmHg group). The skin blood flow declined for pressures exceeding 20 mmHg (0 mmHg: 4.3 +/- 1.2, 10 mmHg: 4.3 +/- 3.3, 20 mmHg: 2.6 +/- 2.7 ml/min/100 g). We concluded that the magnetically operated AUS should use a magnetic coupling with a pressure less than 10 mmHg exerted on the interposing skin.

A new finger joint prosthesis.

A new finger joint prosthesis is being developed for the proximal and distal interphalangeal positions. Currently available "joint spacer" prostheses provide relief from pain and cosmetic improvement, but relatively poor long-term function. The new prosthesis employs a mechanical hinge at the joint. It is fabricated from titanium alloy (6A14V). The hinge mechanism avoids direct metal to metal contact by using high density polyethylene bearings. In vitro tests of the hinge mechanism have passed 75 million cycles of continuous flexure without failure (n = 12). The hinge also incorporates a mechanical limit stop to prevent hyperextension. The hinge mechanism is enclosed in a sealed elastomeric jacket that isolates the hinge from connective tissue ingrowth. The jacket, equivalent to an artificial synovial membrane, has an integrally textured exterior surface designed to promote tissue attachment to the implant to stabilize tissue capsule formation around the joint. To test the in vivo efficacy of the new design, a series of 12 devices were implanted in the knee joint position of adult rabbits. A jacketed prosthesis was implanted on one side, whereas 2 weeks later an unjacketed control was implanted contralaterally. The animals then were maintained for an 8 week period. At sacrifice, the implants were removed, and the response of the surrounding tissues was studied histologically. At the time of implantation, the range of motion of the joints was approximately 100-105 degrees. There was a progressive loss in range of motion observed in both groups. The fibrous tissue capsule around the jacketed implants, however, was significantly reduced in thickness compared with the controls (mean thickness, 1.5 mm vs. 4.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS)