MORPHOLOGICAL CHANGES OF POSTOPERATIVE BONE DEFECT UNDER EXTRACORPOREAL SHOCK WAVE THERAPY

Abstract

Restoring the integrity and volume of bone loss has been a major medical problem for decades. Extracorporeal shock wave therapy is one of the effective methods of impact on reparative osteogenesis. The aim was to study the changes in the quality of bone regenerate and its tissue composition in the process of postoperative bone defects healing in the experiment. Object and methods. Bone defects with a diameter of 4 mm and a depth of 3 mm were modeled in the area of the mandible diastema in 18 mature rabbits over 6 months of age with a mean body weight 2.5 ± 0.2 kg under combined anesthesia and following bioethics principles. Animals were stratified as follows: group A – bone defect healing under ESWT applications with constant maximum wave front pressure (1,2 Bar); group B – healing of the defect under ESWT applications with increasing maximum pressure (1,2-1,6 Bar); group C – control: bone defects healing under a blood clot only. In the early postoperative period, animals of groups A and B received ESWT, which included 3 applications of 500 pulses with a frequency of 5 Hz. CBCT was performed on the 2nd, 15th, 45th, 90th day with a bone-equivalent phantom in the scanning field. Bone density (BD) in the area of bone defect was measured at a depth of 1 mm, 2 mm and 3 mm (which corresponded to the cortical, cancellous bone and the floor of the defect) on grayscale units and the optical density evaluation with calibration of values according to the deviations of radiographic density of the phantom. For better clarity were compared the percentage meaning of the increase relative to the normal X-ray density of intact bone. Histological investigation was performed on 15, 45, 90 days after surgery. Results. According to the CBCT assessment, BD in the defect area varied depending on the measurement site and the chosen treatment method. Thus, at all stages of the observation, the increase in BD was highest in group B, slightly lower in group A and non-significant in the control group. Defects treated with ESWT with constant maximum wave front pressure were replaced with cancellous bone with different mineralization level and a significant amount of osteoid in the early stages, while with increasing maximum pressure from 1.2 Bar to 1.6 Bar, the newly formed bone tissue for 90 days did not differ structurally from intact ones. The bone defects in the control group were replaced by loose connective tissue. Conclusions. In the experiment, the use of ESWT with both a constant value of the maximum pressure at the wave front and with increasing, cause healing of postoperative critical size bone defects. Radiographical and histological changes in bone tissue indicate the initiation of repair processes both within the intact bone surrounding the defect and from the periosteum

Keywords

• bone defects
• maxillofacial area
• extracorporeal shock wave therapy
• cone-beam computed tomography
• bone density.