Thermal isotherms in PMMA and cell necrosis during total hip arthroplasty.
BACKGROUND
Polymethylmethacrylate (PMMA), also known as bone cement, is a commonly used adhesive material to fix implants in Total Hip Arthroplasty (THA). During implantation, bone cement undergoes a polymerization reaction which is an exothermic reaction and results in the release of heat to the surrounding bone tissue, which ultimately leads to thermal necrosis. Necrosis in the bony tissue results in early loosening of the implant, which causes pain and reduces the life of the implant.


OBJECTIVE
The main objective of the present study was to understand the thermal isotherms in PMMA and to determine the optimal cement mantle thickness to prevent cell necrosis during THA.


METHODS
In this study, the environment in the bony tissue during implantation was simulated by constructing 3D solid models to observe the temperature distribution in the bony tissue at different cement mantle thicknesses (1 mm, 3 mm and 5 mm), by applying the temperature conditions that exist during the surgery. Stems made with Co-Cr-Mo, 316L stainless steel and Ti6Al4V were used, which acted as heat sinks, and a thermal damage equation was used to measure the bone damage. FEA was conducted based on temperature conditions and thermal isotherms at different cement mantle thicknesses were obtained.


RESULTS
Thermal isotherms derived with respect to distance in the bony tissue from the center of the cement mantle, and cell necrosis was determined at different mantle thicknesses. Based on the deduced results, cement mantle thickness of 1-5 mm does not cause thermal damage in the bony tissue.


CONCLUSIONS
Considering the long term stability of the implant, cement mantle thickness range from 3 mm-5 mm was found to be optimal in THA to prevent cell necrosis.
Department of Biomedical, Industrial and Human Factors Engineering, Wright State University, Dayton, Ohio - USA.
Dinesh
D
Gundapaneni
Tarun
T
Goswami
D001843:Bone Cements / Q000737:chemistry*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008422:Materials Testing; D010006:Osteoblasts / Q000473:pathology*; D010020:Osteonecrosis / Q000209:etiology* / Q000473:pathology*; D019904:Polymethyl Methacrylate / Q000737:chemistry*
D001843:Bone Cements; D019904:Polymethyl Methacrylate