SPINE Volume 33, Number 21, pp 2326 –2333 ©2008, Lippincott Williams & Wilkins Dynamic Angular Three-Dimensional Measurement of Multisegmental Thoracolumbar Motion In Vivo Erol Gercek, MD,* Frank Hartmann, MD,* Sebastian Kuhn, MD,* Jurgen Degreif, MD, PhD,† Pol Maria Rommens, MD, PhD,* and Lothar Rudig, MD, PhD‡ Study Design. Method validation and in vivo motion segment study. Objective. To determine in healthy subjects in vivo intervertebral segmental kinematics and coupled motion behavior in all 3 planes simultaneously for 3 segments and to evaluate whether these results differ from those in the normal population according to the literature. Summary of Background Data. Few studies have pro- vided a direct invasive approach to investigate segmental kinematics in vivo. Dynamic recordings of 3-dimensional segmental motion patterns of adjacent segments have rarely been reported. To date, no studies have examined the 3-dimensional segmental movements of the thoraco- lumbar junction in vivo in detail. Methods. K-wires were inserted into the Th11, Th12, L1, and L2 spinous processes of 21 healthy subjects. Ultra- sound markers and sensors were attached to the k- wires. Real-time motion data were recorded during standardized ranging exercises. Errors caused by the k-wires, and the static and dynamic accuracy of the system, were considered. Results. Large intersubject variation was found in all of the exercises. The average ranges of motion from Th11 to L2 were 18.7° for flexion-extension, 13.5° for one-sided lat- eral bending, and 1.8° for one-sided axial rotation. Coupled- motion patterns among the subjects showed a coupled flex- ion in active lateral bending and a coupled extension in active rotation, but the results were inconsistent for active extension and flexion. Conclusion. This method offered accurate multiseg- mental dynamic-recording facilities. The dynamic exer- cises showed high reproducibility. The ranges of motion for extension/flexion and lateral bending differed from those reported in previous studies. The coupling patterns were only partly consistent because of large interindi- vidual variation. The measurement error was comparable with that of other invasive methods. Key words: thoracolumbar spine, segmental motion, bio- mechanics, in vivo measurement. Spine 2008;33:2326 –2333 The thoracolumbar spine forms the junction between the relatively rigid thoracal to the more flexible lumbar spine. This region of the spine is of great importance in injuries and most fractures are situated in this part. 1 Before evaluation of injured spinal structures, we need a specific understanding of mechanical behavior of the healthy thoracolumbar junction. Therefore an evalua- tion of the adjacent spine segments within the thora- columbar junction including the kinematic behavior is necessary. Three-dimensional analysis of the range of motion (ROM) of the spine is possible to a limited extent. How- ever, physical examinations and visual evaluations de- pend on the examiner’s subjective assessment. 2 More- over, radiographic investigations only represent a static 2-dimensional situation and have the disadvantage of requiring exposure to radiation. 3,4 Some authors con- sider radiology to be the most accurate method to assess static positioning using bony landmarks. 5 Other studies have tried to investigate spine positioning and movement using inclinometers, 6,7 tape measures, 8 magnetic reso- nance imaging. 9 Several skin-mounted optical or electro- magnetic devices for taking noninvasive measurements of the ROM have been described previously. 10 –14 The aim of the current study was to determine in healthy subjects in vivo intervertebral kinematics and coupled motion behavior in all 3 planes simultaneously for more than 1 segment and to evaluate whether these results differ from those in the normal population ac- cording to the literature. We would provide support for the hypothesis that segmental dynamic motions of the thoracolumbar junction follow a sinusoidal run of the motion curves and that an ultrasound tracking system offers an acceptable access to reliable and accurate mea- surements. Previously, a simultaneous multisegmental invasive investigation of motion like this has not been done. Materials and Methods Obtaining approval from the Local Ethics Committee (Rhein- land-Pfalz, Germany) for the study design and the consent forms used in this invasive in vivo investigation, all subjects were informed about the procedure, got an allowance and con- sented to the process in writing. The power analysis showed that at least 10 samples are required to have 80% power for detecting the difference between the means. From the *Clinic of Trauma Surgery, Johannes Gutenberg University, Mainz, Germany; †Clinic of Orthopaedics and Trauma Surgery, Staedtische Klinken, Esslingen, Germany; and ‡Clinic of Trauma Sur- gery, GPR Klinikum, Ruesselsheim, Germany. Acknowledgment date: December 6, 2007. Revision date: May 4, 2008. Acceptance date: May 6, 2008. 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. 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. Approval given by the ethic commission of the Landesaerztekammer Rheinland-Pfalz, Germany, No. 183701898 (1555). Address correspondence and reprint requests to Erol Gercek, MD, Clinic of Trauma Surgery, Johannes Gutenberg University of Mainz, Langen- beckstrasse 1, 55131 Mainz, Germany; E-mail: gercek@unfall.klinik. uni-mainz.de 2326