4.4. Surgical procedures

All rats were anaesthetized with a Fentanylcitrate (80 g/kg ) - Fluanisone (2.5 mg/kg) (Hypnorm®, Jansen-Pharmaseutica, Belgium) - Midazolam (1.25 mg/kg) (Dormicum®, Roche, Switzerland) blend injected intraperitoneally. After the induction of anaesthesia, they received Cefuroximinenatrium 5 mg/kg i.m. (Zinacef®, Glaxo Welcome plc, Great Britain ). Buprenorphin 0.3 mg/kg s.c. (Temgesic® 0.3 mg/ml, Reckitt & Colman) was used as a postoperative analgesic. The hair was shaven around the implantation site and the skin was sterilized by brushing it with chlorhexidin before operation. The rats were killed using carbon dioxide.

Study II: NiTi, stainless steel and titanium alloy (Ti-6Al-4V) implants (25 of each) were implanted, one implant per rat. A 2 mm incision was made with a knife, and a cannulated needle (Cathlon IV™, Jelco Laboratories, USA) was inserted via the incision into the right paraspinal muscle near the gluteal area toward the sciatic nerve. The needle was removed from inside the plastic cannula, the implant was placed into it and inserted to its final position using the needle. Cannula-assisted implantation was used to avoid prejudicial scar tissue formation due to the surgical procedure itself. Five animals in each group were killed at 2, 4, 8, 12 and 26 weeks after implantation. The implants were dissected with 5 mm of soft tissue around them.

Study III: For periosteal implantation, 25 NiTi, 25 stainless steel and 25 Ti-6Al-4V implants were used, one test specimen per rat. A 10 mm skin incision was made with a knife along the lateral side of the right femur. The muscles were bluntly separated to disclose the femoral bone periosteum. The periosteum was kept intact, to avoid the scar formation effects of surgical trauma. The test implant was placed in direct contact with the intact femur periosteum, but it was not fixed inside the bone. The muscles around the implant were approximated on it with resorbable sutures (Vicryl rapid®, Ethicon) to press the implant against the periosteum. The skin was closed with intracutaneous sutures. Five animals in each group were killed at 2, 4, 8, 12 and 26 weeks after implantation. The implants were dissected with femur bone and 3 mm of surrounding soft tissue.

Study IV: The right knee was shaven and a medial parapatellar incision was made. The patellofemoral joint was exposed and the patella was dislocated laterally. The muscles were bluntly separated and the lower portion of the femoral diaphysis was exposed. The intramedullary space was penetrated from the intracondylar space by drilling it manually with a 1.9 mm (TiN-coated) drill. Osteotomy was made with a diamond saw in the distal third of the femur. The osteotomy was then fixed with a NiTi or StSt intramedullary nail installed distally. The wound was closed in layers using resorbable sutures (Vicryl rapid®, Ethicon). Buprenorphin 0.3 mg/kg s.c. (Temgesic® 0.3 mg/ml, Reckitt & Colman) was used as a postoperative analgesic. The rats were allowed to move freely in their cages after the operation with no external support. Three rats in each group were killed at 2, 4, 8, 12, 26 and 60 weeks after implantation. All femurs with the implants were dissected, as were also the contralateral femurs and the brains, livers, spleens, kidneys and muscles around the operated femur in the 26- and 60-week groups for further studies.