Instrumentation and experiment design for in-vitro interface temperature measurement during the insertion of an orthopaedic implant

The metal implants have been widely used for the human skeleton in dental, maxillofacial and orthopedic treatments for many years. The main function of the implant is to reinforce the fractured bone or provide a direct attachment for a prosthetic limb. The mechanical based orthopedic fixation normally uses a self-tapping implant to provide connectivity between fractured bones. In such a system, the integration between bone and implant is normally based on a biology process called Osseointegration. However, the implantation process courses temperature elevation at the bone-implant interface. Clinically the high interfacial temperature affects regeneration of bone tissue and ultimately the osseointegration between implant and bone. In order to investigate the temperature elevation at the bone-implant interface, the authors developed a designated instrument system and special self-tapping implant with K type thermocouples placed close to the outer surface inside the implant. The experiments were carried out using re-hydrated human femurs while the implant was screwed into the femur. In this study, the temperature elevation was investigated using different implant diameters, insertion distances and speeds. The experiments were performed at the operation room temperature 21degC and the recorded peak temperature was 47.2degC. The result showed that there was a considerable temperature increase at the bone-implant interface while a self-tapping implant was inserted.