The Journal of Bone and Joint Surgery, Vol 73, Issue 4 518-526, Copyright © 1991 by Journal of Bone and Joint Surgery, Inc
Biomechanical evaluation of methods of posterior stabilization of the spine and posterior lumbar interbody arthrodesis for lumbosacral isthmic spondylolisthesis. A calf-spine model
O Shirado, TA Zdeblick, PC McAfee and KE Warden
Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, Baltimore, Maryland 21239.
In order to evaluate biomechanically the efficacy of four types of
posterior instrumentation for the stabilization of isthmic
spondylolisthesis of the lumbosacral spine, mechanical non-destructive
cyclic testing in axial compression, flexion, extension, and rotation was
performed on six fresh lumbosacral spines from calves. Each segment
contained four motion segments, including the lumbosacral junction. Isthmic
spondylolisthesis was created by sectioning the pars interarticularis of
the sixth lumbar vertebra and all posterior ligaments between the fifth and
sixth lumbar levels. Eight constructs were tested sequentially: (1) the
intact spine, (2) the destabilized spine, (3) the spine fixed with
Harrington double-distraction rods, (4) the spine treated with
transpedicular Cotrel-Dubousset instrumentation with a transverse
approximating device, (5) the spine treated with Steffee transpedicular
screws and plates, (6) the spine treated with posterior lumbar interbody
arthrodesis, (7) the spine treated with Cotrel-Dubousset instrumentation
and posterior lumbar interbody arthrodesis, and (8) the spine treated with
Steffee instrumentation and posterior lumbar interbody arthrodesis. One
motion segment was involved in each construct, except for the spine that
was fixed with Harrington instrumentation, which involved three segments.
Strain across the supraspinous and anterior longitudinal ligaments was
measured with two extensometers that were attached at the spondylolisthetic
level and at the intact motion segments adjacent to the fixed level.
Harrington instrumentation was the least rigid construct under any type of
loading except axial compression (p less than 0.05).(ABSTRACT TRUNCATED AT
250 WORDS)
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