Abstract
Percutaneous Radiofrequency Ablation (RFA) has become the method of choice in the treatment of a wide spectrum of disorders. It was introduced for the treatment of Trigeminal Neuralgia and has since been used both extensively and successfully in the treatment of this disorder. Over the past two decades it has been advocated in the treatment of hepatic metastases, lung tumours and cerebral tumours. In 1992 Rosenthal et al reported using this procedure for the treatment of Osteoid Osteomas with good outcome. Further case series have supported this modality of treatment. However, the biomechanical effects of RFA on cortical bone have not been reported to date.
The study comprised of 16 large white land-raised male pigs. All were between 70–80kg in weight at the time of treatment. RFA was performed on the femur, tibia and humerus of each animal 24 hours, 1 week and 4 weeks before euthanisation. RFA was carried out via a percutaneous technique under fluoroscopic guidance. The fibula was not treated in each case and used as an intrinsic control to account for inter-group variability. The Modulus of Rigidity, Maximum Torsional Strength of all bones were determined and compared.
There were three pathological fractures, all occurring in the hemerii and all occurring at 4 weeks post treatment. The Modulus of Rigidity and Maximum Torsional strength were significantly reduced at 24 hours and 1 week when compared with the control. However in the 4 weeks group the biomechanical strength of cortical bone was not significantly different and had almost returned to normal which is contradictory to the clinical setting. There was no significant difference at 24 hours and 1 week.
RFA has become well established as the method of choice for the treatment of Osteoid Osteomas, however the biomechanical consequences of this procedure have not been reported to date. The torsional strength of RF ablated cortical bone is severely attenuated after 1 week, 40% reduction in torsional strength when compared with the control group. This study demonstrated that RFA of cortical bone is an effective treatment for cortical lesions however the biomechanical weakness promotes the need for weight-bearing restrictions when managing these patients postoperatively.
The abstracts were prepared by Emer Agnew. Correspondence should be addressed to Irish Orthopaedic Association, Secretariat, c/o Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland.
