Capturing Three-Dimensional In Vivo Lumbar Intervertebral Joint Kinematics Using Dynamic Stereo-X-Ray Imaging

Abstract

Availability of accurate three-dimensional (3D) kinematics of lumbar vertebrae is necessary to understand normal and pathological biomechanics of the lumbar spine. Due to the technical challenges of imaging the lumbar spine motion in vivo, it has been difficult to obtain comprehensive, 3D lumbar kinematics during dynamic functional tasks. The present study demonstrates a recently developed technique to acquire true 3D lumbar vertebral kinematics, in vivo, during a functional load-lifting task. The technique uses a high-speed dynamic stereo-radiography (DSX) system coupled with a volumetric model-based bone tracking procedure. Eight asymptomatic male participants performed weight-lifting tasks, while dynamic X-ray images of their lumbar spines were acquired at 30 fps. A custom-designed radiation attenuator reduced the radiation white-out effect and enhanced the image quality. High resolution CT scans of participants' lumbar spines were obtained to create 3D bone models, which were used to track the X-ray images via a volumetric bone tracking procedure. Continuous 3D intervertebral kinematics from the second lumbar vertebra (L2) to the sacrum (S1) were derived. Results revealed motions occurring simultaneously in all the segments. Differences in contributions to overall lumbar motion from individual segments, particularly L2-L3, L3-L4, and L4-L5, were not statistically significant. However, a reduced contribution from the L5-S1 segment was observed. Segmental extension was nominally linear in the middle range (20%-80%) of motion during the lifting task, but exhibited nonlinear behavior at the beginning and end of the motion. L5-S1 extension exhibited the greatest nonlinearity and variability across participants. Substantial AP translations occurred in all segments (5.0 ± 0.3 mm) and exhibited more scatter and deviation from a nominally linear path compared to segmental extension. Maximum out-of-plane rotations (<1.91 deg) and translations (<0.94 mm) were small compared to the dominant motion in the sagittal plane. The demonstrated success in capturing continuous 3D in vivo lumbar intervertebral kinematics during functional tasks affords the possibility to create a baseline data set for evaluating the lumbar spinal function. The technique can be used to address the gaps in knowledge of lumbar kinematics, to improve the accuracy of the kinematic input into biomechanical models, and to support development of new disk replacement designs more closely replicating the natural lumbar biomechanics.

Role of the Middle Lumbar Fascia on Spinal Mechanics

“…In particular, a fixed IAR does not permit translation, which has been reported in previous in vitro 30 and in vivo studies 31 . It may be that tension in the MLF constrains translation and if so this would have been obviated by use of a fixed IAR.…”

Apportionment of lumbar L2–S1 rotation across individual motion segments during a dynamic lifting task

“…However, reported results regarding segmental contribution patterns have been inconsistent. Some studies have reported an increased contribution from caudal segments (L4-5, L5-S1) compared to the cephalic segments (Panjabi et al, 1994;Pearcy et al, 1984), others have reported a progressively decreasing contribution from cephalic to caudal segments (Li et al, 2009;Wong et al, 2004;Wong et al, 2006), while still others failed to detect significant differences in contributions (Aiyangar et al, 2014;Goel et al, 1985;Schultz et al, 1979;Tencer et al, 1982;Wu et al, 2014). Differences in experimental protocols do not completely account for these variations as the inconsistency persists even between studies using similar techniques.…”

“…Several studies have attempted to quantify segmental contributions to overall lumbar rotation. These include in vitro cadaveric studies (Goel et al, 1985;Miller et al, 1986;Schultz et al, 1979;Soni et al, 1982;Tencer et al, 1982), in vivo studies based on 2D lateral radiographs or static biplane radiography (Li et al, 2009;Passias et al, 2011;Pearcy et al, 1984;Plamondon et al, 1988), surface markerbased studies (Troke et al, 2001;Zhang and Xiong, 2003), uniplanar continuous radiography (Ahmadi et al, 2009;Harada et al, 2000;Kanayama et al, 1995;Okawa et al, 1998;Wong et al, 2004;Wong et al, 2006), and, more recently, dynamic biplane radiography (Aiyangar et al, 2014;Anderst et al, 2008;Wu et al, 2014). These studies have collectively and progressively improved our understanding of lumbar spinal motion.…”

Effect of Off-Axis Fluoroscopy Imaging on Two-Dimensional Kinematics in the Lumbar Spine: A Dynamic In Vitro Validation Study

“…To completely describe any spinal motion, 3D kinematics must be determined. Investigators have previously used biplanar fluoroscopy techniques to determine 3D spine kinematics [7,8,20,28]. This type of analysis more completely describes spinal motion but is very resource intensive.…”

“…Numerous investigators have used fluoroscopic methods to obtain 2D [17][18][19] and 3D [7,8,20] measurements of lumbar intervertebral motion. Although 3D measures of lumbar kinematics can provide highly detailed information about complex intervertebral kinematics, the technique requires sophisticated hardware and software for measuring images; such tools are not readily available in the clinical setting.…”