Using the transverse processes of fresh porcine lumbar spines as an experimental model we evaluated the heat generated by a rotating burr of a high-speed drill in cutting the bone. The temperature at the drilled site reached 174°C with a diamond burr and 77°C with a steel burr. With water irrigation at a flow rate of 540 ml/hr an effective reduction in the temperature was achieved whereas irrigation with water at 180 ml/hr was much less effective. There was a significant negative correlation between the thickness of the residual bone and the temperature measured at its undersurface adjacent to the drilling site (p < 0.001).

Our data suggest that tissues neighbouring the drilled bone, especially nerve roots, can be damaged by the heat generated from the tip of a high-speed drill. Nerve-root palsy, one of the most common complications of cervical spinal surgery, may be caused by thermal damage to nerve roots arising in this manner.

We developed a new porous scaffold made from a synthetic polymer, poly(DL-lactide-co-glycolide) (PLG), and evaluated its use in the repair of cartilage. Osteochondral defects made on the femoral trochlear of rabbits were treated by transplantation of the PLG scaffold, examined histologically and compared with an untreated control group.

Fibrous tissue was initially organised in an arcade array with poor cellularity at the articular surface of the scaffold. The tissue regenerated to cartilage at the articular surface. In the subchondral area, new bone formed and the scaffold was absorbed. The histological scores were significantly higher in the defects treated by the scaffold than in the control group (p < 0.05).

Our findings suggest that in an animal model the new porous PLG scaffold is effective for repairing full-thickness osteochondral defects without cultured cells and growth factors.