Thermal Effect of Bone Reaming

Total hip replacement surgery is common in modern medicine and it provides patients with pain free gait. During surgery, high speed mechanical tools such as reamers (Figure 1) are used to prepare bone to receive the implant. Acetabular reamers are used to create the required part-spherical cavity in the acetabulum for the artificial cup or shell of a total hip replacement.

During acetabular reaming, some surgeons note occasional smoke, blackening of tissue and a smell of burning, especially with reamers which have been used many times. These high temperatures may result in potential thermal damage to the bone, as above 56˚C osteonecrosis may occur. This bone death could result in failure of cementless fixation which relies on bone growing into the artificial joint. One of the factors effecting temperature increase may be the reamer’s bluntness. There is no accepted definition of bluntness and surgeons would prefer to have a quick indicator of reamer condition. For this reason, use of an infrared laser camera has been proposed. The project objectives were to undertake in vivo tests of acetabular reaming using cow (bovine) bone. Using a FLIR E45 infra-red video temperature recording system the temperature before, during and immediately after reaming was recorded. Reaming process was performed on 8 bovine acetabula (hemi-pelvis) using various reamers while the temperature was recorded. All reamers were used and several different sizes were tested.