Biomechanical Quantification of Pathologic Manipulable Spinal Lesions

(From the July 2012 issue of “The Scope” – by Steven T. Tanaka, DC)

Colluca CJ, Gunzburg R, Freeman BJ, et al. Biomechanical Quantification of Pathologic Manipulable Spinal Lesions: An In Vivo Ovine Model of Spondylolysis and Intervertebral Disc Degeneration. JMPT June 2012; 35(5):354-66.

ABSTRACT: Objective: The purposes of this study were to quantify the biomechanical and pathologic consequences of surgically induced spinal lesions and to determine their response to spinal manipulation (SMT) in an in vivo ovine model. Methods: Of 24 Merino sheep, 6 received L5 spondylolytic defects, 6 received L1 annular lesions, and 12 served as respective controls. Dorsoventral (DV) stiffness was assessed using oscillatory loads (2-12 Hz). Two SMT force-time profiles were administered in each of the groups using a randomized and repeated-measures design. Stiffness and the effect of SMT on the DV motions and multifidus needle electromyographic responses were assessed using a repeated measures analysis of variance (α = .05). Postmortem histologic analysis and computed tomography validated the presence of lesions. Results: L5 DV stiffness was significantly increased (40.2%) in the spondylolysis (6.28 N/mm) compared with the L5 control group (4.48 N/mm) (P < 03). Spinal manipulations delivered to the spondylolysis group resulted in less DV vertebral displacement (P < .01) compared with controls. Dorsoventral stiffness of the disc degeneration group was 5.66 N/mm, 94.5% greater than in the L1 control group (2.91 N/mm) (P < .01). One hundred–millisecond SMTs resulted in significantly reduced DV displacements in the disc degeneration group compared with the L1 control group (P < .01). Animals in the disc degeneration group showed a consistent 25% to 30% reduction in needle electromyographic responses to all SMTs.

Conclusions: Quantifiable objective evidence of spinal lesions and their response to SMT were confirmed in this study. Neuromechanical alterations provide novel insights into quantifying manipulable spinal lesions and a means to biomechanically assess SMT outcomes.

COMMENTS: In this study, the sheep had a surgically created spondylolysis at L5. The L1 disc was injured by scalpel on another group of sheep. After 6 months, the sheep were evaluated. Spinal manipulation (SM) was done mechanically with a PA direction. In those who had spondylolysis, there was bony healing and fibrous changes. Those that received SM had significantly reduced PA vertebral displacement compared to controls. Those that received L1 disc injury had signs of moderate to advanced disc degeneration. Disc changes extended to nucleus pulposus. There was significant loss of disc height caused by breakdown of the disc matrix. The peripheral annulus showed advanced repair with some showing a more organized collagenized scar tissue. In most, from the initial annular lesion, there were both radial and circumferential lesions. The nucleus migrated in many of the injured discs. Less PA vertebral displacement was found in the subjects that received SM along with a reduction of positive nEMG of the muttifidus muscle response. The latter was the same in both SM and non-SM spondylosis subjects. For Gonstead chiropractors, a useful study would be to see if SM wouldaffect the degree of disc degeneration.