On implant integration in irradiated bone. An experimental study of the effects of hyperbaric oxygenation and delayed implant placement

Abstract

The bone-anchored craniofacial prosthesis system is an alternative to conventional reconstructive surgery for patients with craniofacial defects. However, treatment of head and neck tumors with high dose radiotherapy alters the predictability of osseointegrated implants. Both increased time-intervals from irradiation to implant insertion and adjunctive hyperbaric oxygenation treatment (HBO) have been recommended to improve implant integration in irradiated bone. The aims of the research undertaken have been to experimentally investigate the primary healing phase of implant integration in irradiated bone, the effects of different time-intervals between irradiation and implant insertion and the effects of HBO on implant integration in irradiated bone in a rabbit model. Further, the effects of irradiation, delayed surgery and HBO on bone healing in a situation with predominantly cancellous bone have been investigated in another rabbit model. A microradiographic videodensitometric method has been further developed and evaluated. Removal torque measurement, histomorphometry and densitometric bone-mass determination from microradiographs were used as evaluation techniques.Irradiation reduced bone-to-titanium implant interface strength and reduced new bone formation. HBO treatment or a recovery period of one year after irradiation improved bone-to-titanium implant interface strength in irradiated bone. Histomorphometry revealed a recovery with time after irradiation in irradiated bone and indicated that HBO might accelerate bone maturation. There were no statistically significant effects of irradiation, HBO or delayed surgery on bone formation in terms of mineralization in a situation with predominantly cancellous bone. The overall results suggest that cancellous bone might recover faster than cortical bone from irradiation trauma. When the video camera was exchanged for a slide-scanner to perform computer-assisted densitometric measurements the accuracy of the method was improved, and modern software made the measurement procedure fast and stable. The coarsening of the calibration scale, necessary to measure larger samples, and producing microradiographs over an extended period of time reduced the accuracy of the method.Conclusions: Both HBO treatment and a recovery period between irradiation and implant insertion improved implant integration in irradiated bone in the rabbit model used. The negative effects of irradiation on bone healing were more pronounced in cortical bone compared to cancellous bone.