All rats received enrofloxacin (5 mg/kg), carprofen (5 mg/kg) and morphine (2.5 mg/kg) subcutaneously pre-operatively. To broaden generalizability, both a spinal and long bone (femur) application were performed. For spinal applications, rats were placed prone on a prewarmed surgery table under general anesthesia [17 (link)]. The iliac crest and spinous processes were identified and a midline incision was performed 1 cm cranially from the iliac crest. The paraspinal musculature was dissected laterally to expose the transverse processes of L4–5. A 0.8 mm hole was drilled in the transverse process and a stainless-steel screw (1*5 mm), attached via a poly(ε-caprolactone) connecting piece to a polyurethane (PU) catheter (internal diameter 0.6 mm, UNO, Zevenaar, Netherlands) was inserted, so that the catheter opening faced the bone surface (Fig. 1 ). Sterile saline solution was dripped next to the hole during drilling for cooling. The dead volume of catheters was pre-filled with the appropriate bupivacaine solution to ensure infusion of precise volumes. The catheter was tunneled subcutaneously towards an exit-point between the shoulders and fixed to the skin with a suture. Bupivacaine infusion was initiated after confirmed absence of motor deficits (i.e., following observed movement of tail and paws).![]()
Schematic representation of experimental setup. Screws with a catheter attached were implanted in either the spine or femur. Catheters were then tunneled subcutaneously (dotted line) and exited between the shoulders. A pump was connected to the catheter to allow controlled infusion of bupivacaine solutions. Representative MicroCT images for the two surgical locations are shown
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