Study Design. In vivo noninvasive study.
Objective. To properly quantify pedicle anatomic parameters, using subject-based CT three-dimensional models and compare the data from 2-dimensional transverse-CT images.
Summary of Background Data. Accurate measurement of morphometric parameters of pedicle isthmus is important for transpedicular procedures. Anatomically, the lumbar pedicle is known to be elliptical cross-sectionally and slightly inclined in the vertical plane in the lower lumbar levels. Therefore, measurement of the pedicle isthmus may be overestimated when transverse images are used. More accurate measurement of the 3-dimensional geometry of the pedicle is therefore needed. To the best of our knowledge, 3-dimensional geometry of the pedicle has not been reported as the literature values are based on 2-dimensional image data.
Methods. In vivo measurements of the lumbar pedicle isthmus were performed on the 3-dimensional subject-based CT models, using custom-developed software in 89 volunteers.
Results. The least axis of pedicle, the longest axis of pedicle and the transverse plane width were largest at L5 in both genders. The isthmus angle declined in the lower levels. The ratio of the transverse plane width to the least axis of pedicle was largest at L5.
Conclusion. Our results showed that the least axis of pedicle, the longest axis of pedicle and the transverse plane width peaked at L5, and the transverse plane width became approximately twice as long in the lower levels compared to the upper levels. The ratio of the transverse plane width to the least axis of pedicle increased by about 40% at L5. These findings highlight the fact that measuring the isthmus width from CT transverse images leads to overestimation, especially in the lower lumbar spine. Therefore, a 3-dimensional inclination of the least axis of the pedicle should be taken into account for the determination of the pedicle diameter in the lower lumbar vertebrae.
The lumbar pedicle isthmus was measured using in vivo subject-based 3-dimensional CT models. The pedicle isthmus angle increased significantly at lower levels. Inclination of the least axis of the pedicle isthmus should be taken in account for the determination of the pedicle diameter in the lower lumbar vertebrae.
From the Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL.
Acknowledgment date: February 11, 2009. Acceptance date: April 20, 2009.
The manuscript submitted does not contain information about medical device(s)/drug(s).
No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.
Supported by NIH grant P01 AR48152.
Address correspondence and reprint requests to Nozomu Inoue, MD, PhD, Department of Orthopedic Surgery, Rush University Medical Center, 1653 West Congress Parkway, 1471 Jelke, Chicago, IL 60612; E-mail: Nozomu_Inoue@rush.edu