Turkish Neurosurgery 2015 , Vol 25 , Num 2
X-Stop« Implantation Effectively Limits Segmental Lumbar Extension in-vivo without Altering the Kinematics of the Adjacent Levels
Zongmiao WAN1, Guoan LI2
1The First Affiliated Hospital of Nanchang University, Orthopaedic Department, JiangXi Province, China
2Massachusetts General Hospital, Harvard Medical School, Bioengineering Laboratory, Department of Orthopaedics, Boston, USA
DOI : 10.5137/1019-5149.JTN.10135-13.0 AIM: To evaluate the in-vivo three-dimensional (3D) vertebral kinematics of the implanted and adjacent segments after implantation of the interspinous process distracting (ISP) device during various functional activities.

MATERIAL and METHODS: Eight patients with lumbar spinal stenosis (LSS) scheduled for X-Stop« surgery were recruited. Prior to surgery, patients were scanned with computed tomography/ magnetic resonance imaging (CT/MRI) in order to construct 3D L2 to S1 vertebral models. The lumbar spines of the patients were then imaged using two fluoroscopes while they performed seven functional activities before and after X-Stop« surgeries. The in-vivo 3D vertebral positions were determined in the dual fluoroscopic images using an established 2D-3D matching method. The vertebral 3D ranges of motion (ROM) of the implanted and cranial-caudal adjacent levels were then measured.

RESULTS: Primary ROMs of the implanted segments were significantly decreased (p<0.05) by 50.2% only at torso extension, from preoperative 2.5▒1.4║ to postoperative 1.1▒0.5║, but not significantly (p>0.05) at flexion, twisting and lateral bending. Primary ROM and the coupled translations and rotations of the implanted and the adjacent levels were not significantly changed during each posture.

CONCLUSION: X-Stop« implantation reduced the in-vivo range of extension by 50.2% at the implanted segment without disturbing 3D kinematics at the adjacent segments. Keywords : Interspinous process distracting device, In-vivo, Kinematics, Adjacent segments

Corresponding author : Zongmiao Wan, zongmiao2008@gmail.com