Surgical Implantation of Ultrafiltration Probes in Ovine Bone and Muscle

It may be desirable to collect compounds directly from sites of interest if blood concentrations do not reflect tissue levels. Ultrafiltration and microdialysis probes may be used to do this, but the hollow fibers of these probes are quite fragile. For this reason, we developed a pull-through technique that allows their implantation into the ovine quadriceps muscle and femur.The sheep is placed under anesthesia in lateral recumbency. An incision is made midway between the patella and greater trochanter directly over the lateral femur. A hand drill is used to make a 4.5-mm hole into the medullary cavity through the lateral cortex of the distal femur. A second incision is then made over the greater trochanter. The drill bit is inserted into the trochanteric fossa and a hole is drilled distally through the medullary cavity of the femur to the level of the first hole. A looped 20-gauge wire is then inserted into the femur and removed through the distal hole. Suture is attached, and the wire is withdrawn, leaving the suture in place. The suture is tied to the ultrafiltration probe tubing, allowing the probe to be carefully drawn into position. For implantation into the muscle, a 10-gauge introducer is used. The introducer is placed through the quadriceps muscle and the probe is then threaded through it. This technique has been successfully performed on 18 sheep. All sheep tolerated the procedure well. Up to 2.0 mL/day of interstitial fluid was recovered from each site. The average lifetimes of the bone and muscle probes were 35 and 40 days, respectively.