CROMBACH, Lee J., GLESER, Goldine C., NANDA, Harinder & RAJARATNAM, Nageswar. The dependability of behavioral measurements: theory of generalizability for scores and profiles. New York, John Wiley and Sons, 1972.

The dependability of behavioral measurements: theory of generalizability for scores and profiles

The effects of different parameters on the mechanical behaviour of the lumbar spine were in most cases determined deterministically with only one uncertain parameter varied at a time while the others were kept fixed Thus most parameter combinations were disregarded The aim of the study was to determine in a probabilistic finite element study how intervertebral rotation, intradiscal pressure, and contact force in the facet joints are affected by the input parameters implant position, implant ball radius, presence of scar tissue, and gap size in the facet joints An osseoligamentous finite element model of the lumbar spine ranging from L3 vertebra to L5/S1 intervertebral disc was used An artificial disc with a fixed center of rotation was inserted at level L4/L5 The model was loaded with pure moments of 75 Nm to simulate flexion, extension, lateral bending, and axial torsion In a probabilistic study the implant position in anterior–posterior (ap) and in lateral direction, the radius of the implant ball, and the gap size of the facet joint were varied After implanting an artificial disc, scar tissue may develop, replacing the anterior longitudinal ligament Thus presence and absence of scar tissue were also simulated For each loading case studied, intervertebral rotations, intradiscal pressures and contact forces in the facet joints were calculated for 1,000 randomized input parameter combinations in order to determine the probable range of these output parameters Intervertebral rotation at implant level varies strongly for different combinations of the input parameters It is mainly affected by gap size, ap-position and implant ball radius for flexion, by scar tissue and implant ball radius for extension and lateral bending, and by gap size and implant ball radius for axial torsion For extension, intervertebral rotation at implant level varied between 14° and 75° Intradiscal pressure in the adjacent discs is only slightly affected by all input parameters Contact forces in the facet joints at implant level vary strongly for the different combinations of the input parameters For flexion, forces are 0 in 63% of the cases, but for small gap sizes and large implant ball radii they reach values of up to 533 N Similar results are found for extension with a maximum predicted force of 560 N Here the forces are mainly influenced by gap size, implant ball radius and scar tissue The forces vary between 0 and 300 N for lateral bending and between 0 and 200 N for axial torsion The parameters that have the greatest effect in both loading cases are the same as those for extension Intervertebral rotation and contact force in the facet joints depend strongly on the input parameters studied The probabilistic study shows a large variation of the results and likelihood of certain values Clinical studies will be required to show whether or not there is a strong correlation of parameter combinations that cause high facet joint forces and low back pain after total disc replacement

/pdf/effect-of-an-artificial-disc-on-lumbar-spine-biomechanics-a-1z17nusy30.pdf

Effect of an artificial disc on lumbar spine biomechanics: a probabilistic finite element study

Study Design Prospective case series. Objective To examine the relation between improved disability and changes in abdominal and lumbar multifidus (LM) thickness using ultrasound imaging following spinal manipulative therapy (SMT) in patients with low back pain (LBP). Background Although there is a growing body of literature demonstrating physiologic effects following the application of SMT, few studies have attempted to correlate these changes with clinically relevant outcomes. Methods Eighty-one participants with LBP underwent 2 thrust SMT treatments and 3 assessment sessions within 1 week. Transversus abdominis (TrA), internal oblique (IO), and LM muscle thickness was assessed during each session, using ultrasound imaging of the muscles at rest and during submaximal contractions. The Modified Oswestry Disability Index was used to quantify participants' improvement in LBP-related disability. Stepwise hierarchical multiple linear regression and repeated-measures analysis of variance were performed to exa...

Association between changes in abdominal and lumbar multifidus muscle thickness and clinical improvement after spinal manipulation.

Response of lumbar paraspinal muscles spindles is greater to spinal manipulative loading compared with slower loading under length control

Patient-centered outcomes of high-velocity, low-amplitude spinal manipulation for low back pain: a systematic review.

STUDY DESIGN A blinded, randomized controlled trial was conducted. OBJECTIVE To test the hypothesis that chiropractic side-posture manipulation (adjusting) of the lumbar spine separates (gaps) the zygapophysial (Z) joints. SUMMARY OF BACKGROUND DATA Spinal adjusting is thought to gap the Z joints, yet no studies have conclusively validated this hypothesis, and some investigators have reported that the lumbar Z joints do not gap during rotation. METHODS For this study, 64 healthy student volunteers (32 men and 32 women) ages 22 to 30 years with no history of significant low back pain were randomized into four groups of 8 men and 8 women each. Interventions included lumbar side-posture spinal adjusting (manipulation) and side-posture positioning. Anterior to posterior measurements of the Z joints from MRI scans taken before and after side-posture spinal adjusting and before and after side-posture positioning were compared. RESULTS Observers performing the measurements were blinded as to group and first and second scans. Reliability of the measurements was established. Differences were found between the groups (F = 24.15; P < 0.000, analysis of variance). Side-posture positioning showed greater gapping than the control condition (mean difference, 1.18; P < 0.000); side-posture adjusting showed greater gapping than the control condition (mean difference, 1.89; P < 0.000), and side-posture adjusting showed greater gapping than side-posture positioning (mean difference, 0.71; P = 0.047). CONCLUSIONS Spinal adjusting produced increased separation (gapping) of the Z joints. Side-posture positioning also produced gapping, but less than that seen with lumbar side-posture adjusting. This study helps to increase understanding about the mechanism of action for spinal manipulation.

/pdf/the-effects-of-side-posture-positioning-and-spinal-adjusting-4hzu2qw628.pdf

The effects of side-posture positioning and spinal adjusting on the lumbar Z joints: a randomized controlled trial with sixty-four subjects.

Magnetic Resonance Imaging Zygapophyseal Joint Space Changes (Gapping) in Low Back Pain Patients following Spinal Manipulation and Side Posture Positioning: A Randomized Controlled Mechanisms Trial with Blinding

Douglas Gregerson

Papers

The effects of side-posture positioning and spinal adjusting on the lumbar Z joints: a randomized controlled trial with sixty-four subjects.

Magnetic Resonance Imaging Zygapophyseal Joint Space Changes (Gapping) in Low Back Pain Patients following Spinal Manipulation and Side Posture Positioning: A Randomized Controlled Mechanisms Trial with Blinding

Quantification of Cavitation and Gapping of Lumbar Zygapophyseal Joints during Spinal Manipulative Therapy