Alexander Breen

Measurement of Intervertebral Motion Using Quantitative Fluoroscopy: Report of an International Forum and Proposal for Use in the Assessment of Degenerative Disc Disease in the Lumbar Spine

Quantitative fluoroscopy (QF) is an emerging technology for measuring intervertebral motion patterns to investigate problem back pain and degenerative disc disease. This International Forum was a networking event of three research groups (UK, US, Hong Kong), over three days in San Francisco in August 2009. Its aim was to reach a consensus on how best to record, analyse, and communicate QF information for research and clinical purposes. The Forum recommended that images should be acquired during regular trunk motion that is controlled for velocity and range, in order to minimise externally imposed variability as well as to correlate intervertebral motion with trunk motion. This should be done in both the recumbent passive and weight bearing active patient configurations. The main recommended outputs from QF were the true ranges of intervertebral rotation and translation, neutral zone laxity and the consistency of shape of the motion patterns. The main clinical research priority should initially be to investigate the possibility of mechanical subgroups of patients with chronic, nonspecific low back pain by comparing their intervertebral motion patterns with those of matched healthy controls.

Attainment rate as a surrogate indicator of the intervertebral neutral zone length in lateral bending: an in vitro proof of concept study

BackgroundLumbar segmental instability is often considered to be a cause of chronic low back pain. However, defining its measurement has been largely limited to laboratory studies. These have characterised segmental stability as the intrinsic resistance of spine specimens to initial bending moments by quantifying the dynamic neutral zone. However these measurements have been impossible to obtain in vivo without invasive procedures, preventing the assessment of intervertebral stability in patients. Quantitative fluoroscopy (QF), measures the initial velocity of the attainment of intervertebral rotational motion in patients, which may to some extent be representative of the dynamic neutral zone. This study sought to explore the possible relationship between the dynamic neutral zone and intervertebral rotational attainment rate as measured with (QF) in an in vitro preparation. The purpose was to find out if further work into this concept is worth pursuing.MethodThis study used passive recumbent QF in a multi-segmental porcine model. This assessed the intrinsic intervertebral responses to a minimal coronal plane bending moment as measured with a digital force guage. Bending moments about each intervertebral joint were calculated and correlated with the rate at which global motion was attained at each intervertebral segment in the first 10° of global motion where the intervertebral joint was rotating.ResultsUnlike previous studies of single segment specimens, a neutral zone was found to exist during lateral bending. The initial attainment rates for left and right lateral flexion were comparable to previously published in vivo values for healthy controls. Substantial and highly significant levels of correlation between initial attainment rate and neutral zone were found for left (Rho = 0.75, P = 0.0002) and combined left-right bending (Rho = 0.72, P = 0.0001) and moderate ones for right alone (Rho = 0.55, P = 0.0012).ConclusionsThis study found good correlation between the initial intervertebral attainment rate and the dynamic neutral zone, thereby opening the possibility to detect segmental instability from clinical studies. However the results must be treated with caution. Further studies with multiple specimens and adding sagittal plane motion are warranted.

Accuracy and repeatability of quantitative fluoroscopy for the measurement of sagittal plane translation and finite centre of rotation in the lumbar spine

Quantitative fluoroscopy (QF) was developed to measure intervertebral mechanics in vivo and has been found to have high repeatability and accuracy for the measurement of intervertebral rotations. However, sagittal plane translation and finite centre of rotation (FCR) are potential measures of stability but have not yet been fully validated for current QF. This study investigated the repeatability and accuracy of QF for measuring these variables. Repeatability was assessed from L2-S1 in 20 human volunteers. Accuracy was investigated using 10 consecutive measurements from each of two pairs of linked and instrumented dry human vertebrae as reference; one which tilted without translation and one which translated without tilt. The results found intra- and inter-observer repeatability for translation to be 1.1mm or less (SEM) with fair to substantial reliability (ICC 0.533-0.998). Intra-observer repeatability of FCR location for inter-vertebral rotations of 5° and above ranged from 1.5mm to 1.8mm (SEM) with moderate to substantial reliability (ICC 0.626-0.988). Inter-observer repeatability for FCR ranged from 1.2mm to 5.7mm, also with moderate to substantial reliability (ICC 0.621-0.878). Reliability was substantial (ICC>0.81) for 10/16 measures for translation and 5/8 for FCR location. Accuracy for translation was 0.1mm (fixed centre) and 2.2mm (moveable centre), with an FCR error of 0.3mm(x) and 0.4mm(y) (fixed centre). This technology was found to have a high level of accuracy and with a few exceptions, moderate to substantial repeatability for the measurement of translation and FCR from fluoroscopic motion sequences.

Ionizing radiation exposure and the development of intervertebral disc degeneration—no case to answer

In the following perspective article, Mellor and Breen provide a counterpoint to a previous perspective on the potential link between ionizing radiation exposure and intervertebral disc degeneration in humans [1]. The previous perspective asked, is this link a myth or reality? It suggested the potential for such a link. Mellor and Breen offer a drastically alternate view, in essence, that the question itself is flawed. To support their perspective, they explain the different units of radiation measurement and their conversion to risk in humans and how this impacts the previous perspective. They explain the variable sensitivity of different body tissues to radiation and highlight that neither human research nor any of the multiple international regulatory agencies have ever suggested that the intervertebral disc is sensitive to radiation. Finally, they claim that it is impossible to predict with any certainty the effects of low-level radiation on the intervertebral discs.

Leadership and capacity building in international chiropractic research: introducing the chiropractic academy for research leadership (CARL)

In an evidence-based health care environment, healthcare professions require a sustainable research culture to remain relevant. At present however, there is not a mature research culture across the chiropractic profession largely due to deficiencies in research capacity and leadership, which may be caused by a lack of chiropractic teaching programs in major universities. As a response to this challenge the Chiropractic Academy for Research Leadership, CARL, was created with the aim of develop a global network of successful early-career chiropractic researchers under the mentorship of three successful senior academics from Australia, Canada, and Denmark. The program centres upon an annual week-long program residential that rotates continental locations over the first three-year cycle and between residentials the CARL fellows work on self-initiated research and leadership initiatives. Through a competivite application process, the first cohort was selected and consists of 13 early career researchers from five professions in seven countries who represent diverse areas of interests of high relevance for chiropractic. The first residential was held in Odense, Denmark, with the second being planned in April 2018 in Edmonton, Canada, and the final residential to be held in Sydney, Australia in 2019.

Estimation of in vivo inter-vertebral loading during motion using fluoroscopic and magnetic resonance image informed finite element models

Finite element (FE) models driven by medical image data can be used to estimate subject-specific spinal biomechanics. This study aimed to combine magnetic resonance (MR) imaging and quantitative fluoroscopy (QF) in subject-specific FE models of upright standing, flexion and extension. Supine MR images of the lumbar spine were acquired from healthy participants using a 0.5 T MR scanner. Nine 3D quasi-static linear FE models of L3 to L5 were created with an elastic nucleus and orthotropic annulus. QF data was acquired from the same participants who performed trunk flexion to 60° and trunk extension to 20°. The displacements and rotations of the vertebrae were calculated and applied to the FE model. Stresses were averaged across the nucleus region and transformed to the disc co-ordinate system (S1 = mediolateral, S2 = anteroposterior, S3 = axial). In upright standing S3 was predicted to be -0.7 ± 0.6 MPa (L3L4) and -0.6 ± 0.5 MPa (L4L5). S3 increased to -2.0 ± 1.3 MPa (L3L4) and -1.2 ± 0.6 MPa (L4L5) in full flexion and to -1.1 ± 0.8 MPa (L3L4) and -0.7 ± 0.5 MPa (L4L5) in full extension. S1 and S2 followed similar patterns; shear was small apart from S23. Disc stresses correlated to disc orientation and wedging. The results demonstrate that MR and QF data can be combined in a participant-specific FE model to investigate spinal biomechanics in vivo and that predicted stresses are within ranges reported in the literature.

EVALUATION OF ANGULAR KINEMATICS OF LOWER LIMB AMPUTEES USING QUANTITATIVE FLUOROSCOPIC IMAGING

In the design of a functional prosthetic socket for lower limb amputees it is desirable to mimic the actions of a healthy limb as close as possible. While limiting the degree of freedom to which the residual limb is able to move in the prosthetic socket during ambulation (walking) is a prerequisite for an adequate fitting, with inadequate understanding of the specific anatomy of the patient including residuum changes after amputation, an overly tight socket fit can lead to pain, pressure ulcers and infections. Furthermore, changes in the initial alignment between the residual limb and socket have been shown to affect the pressure distribution within the socket. The purpose of this study was to measure and report the angular kinematic data/variables of lower limb amputees under protocols designed to infer the kinematics within the socket during walking and static weight hold on the artificial limb. The study details the angular motion kinematics of the tibia within the residuum with and without the addition of a 5kg mass used to replicate forces applied to the residual limb while undergoing the swing phase of slow and fast walking. Using quantitative fluoroscopic imaging techniques, continuous frame by frame tracking of tibia and prosthesis have been recorded and measures of residual limb/tibia angular kinematic have been performed. The understanding of the angular motion of the tibia within the residuum conveys a new insight in socket design (comfort and performance considerations) and furnishes a straightforward view into the effects of surgical amputation and prosthetic fit techniques.