TUESDAY, Mar. 10 (HealthDay News) -- Skeletal tissue dissection performed as part of the upper instrumented vertebra anchor site preparation and placement can reduce the stiffness of the proximal adjacent motion segment, researchers report in the Mar. 1 issue of Spine.
Andy L. Anderson, M.D., and colleagues from Kansas University Medical Center in Kansas City measured thoracic motion segment flexion stiffness of the supra-adjacent motion segment in 23 intact thoracic motion segments from six human cadavers after sequentially performed procedures associated with posterior upper instrumented vertebra anchor placement or mobilization.
The investigators found that bilateral supratransverse process hook, supralaminar hook, pedicle screw placement, or pedicle screw removal had only small effects on flexion stiffness, but together reduced flexion stiffness by 16.31 percent. Supraspinous and interspinous process ligament transection alone reduced flexion stiffness by 6.59 percent. Supralaminar hook site preparation plus supraspinous and interspinous process ligament transaction reduced flexion stiffness by 12.62 percent, the researchers report. Transection of the remaining posterior structures reduced flexion stiffness by 44.72 percent, while transection of the posterior stabilizing structures reduced stiffness by 67.61 percent, the authors note.
"Posterior thoracic skeletal structures involved in upper instrumented vertebra exposure and anchor placement were found to contribute to adjacent segment flexion stiffness," Anderson and colleagues conclude. "Although stiffness loss was small after individual procedures, the effects were additive for routinely used combinations."
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