Charakterisierung der Knochendichte im Bereich der Wirbelsäule mittels quantitativer Computertomographie
Charaterization of the spinal bone mineral density using quantitative computed tomography
by Friederike Sophie Klockner
Date of Examination:2022-03-23
Date of issue:2022-03-21
Advisor:Prof. Dr. Stephan Sehmisch
Referee:Prof. Dr. Stephan Sehmisch
Referee:Prof. Dr. Heide Siggelkow
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Abstract
English
Purpose Pedicle Screw loosening is one major problem in posterior instrumentation especially in patients with osteoporosis. Augmentation of pedicle srews with cement is a common procedure to improve the stability of the implanted pedicle screws in patients with osteoporosis. However, there is still no clinically used algorithm to regularly measure the bone mineral density (BMD) and detect the osteoporotic BMD in patients undergoing posterior stabilization. The aim of this study was to investigate the BMD measured with the asynchronous quantitative computed tomography (QCT) and to establish a clinical algorithm to measure the preoperative BMD in all patients undergoing posterior stabilization. Methods 227 Patients between 20 and 92 years of age with acute or degenerative spine diseases who underwent diagnostic computed tomography (CT) were included in this study. The BMD was measured using quantitative computed tomography. A vertebral fracture occurred in 138 of the patients. Of these, 69 patients underwent posterior stabilization. If the preoperative measured BMD was less then 80 mg/cm3, an additional stabilization with cement augmentation of the pedicle screw was recommended. Results A significant correlation between the BMD and the age as well as for the location of the vertebral body in the spine was found (r2= 0.931; p<0,001). The BMD decreased significantly with higher age as well as from cranial to caudal in the spine. 69 patients undergoing posterior instrumentation of the spine were measured preoperativley, a cement augmentation of the pedicle screws was recommended and performed in 30,43% of these patients. Conclusion The QCT is a reliable method for regularly preopertive measurement of the BMD, as it relies on the preoperative performed CT diagnostic. An Algorithm for regular measurement of the preopertive BMD, as performed in this study, is a reliable method to reduce the rate of pedicle screw loosening.
Keywords: Spine; Osteoporosis; Bone mineral density; Quantitative computed tomography; DXA; Pedicle screw; Augmentation; Pedicle screw loosening