There are limited data regarding the implications of revision posterior surgery in the setting of previous cervical arthroplasty (CA). The purpose of this study was to analyze segmental biomechanics in human cadaveric specimens with and without CA, in the context of graded posterior resection.
Fourteen human cadaveric cervical spines (C3–T1 or C2–7) were divided into arthroplasty (ProDisc-C, n = 7) and control (intact disc, n = 7) groups. Both groups underwent sequential posterior element resections: unilateral foraminotomy, laminoplasty, and finally laminectomy. Specimens were studied sequentially in two different loading apparatuses during the induction of flexion-extension, lateral bending, and axial rotation.
Range of motion (ROM) after artificial disc insertion was reduced relative to that in the control group during axial rotation and lateral bending (13% and 28%, respectively; p < 0.05) but was similar during flexion and extension. With sequential resections, ROM increased by a similar magnitude following foraminotomy and laminoplasty in both groups. Laminectomy had a much greater effect: mean (aggregate) ROM during flexion-extension, lateral bending, and axial rotation was increased by a magnitude of 52% following laminectomy in the setting of CA, compared to an 8% increase without arthroplasty. In particular, laminectomy in the setting of CA introduced significant instability in flexion-extension, characterized by a 90% increase in ROM from laminoplasty to laminectomy, compared to a 16% increase in ROM from laminoplasty to laminectomy without arthroplasty (p < 0.05).
Foraminotomy and laminoplasty did not result in significant instability in the setting of CA, compared to controls. Laminectomy alone, however, resulted in a significant change in biomechanics, allowing for significantly increased flexion and extension. Laminectomy alone should be used with caution in the setting of previous CA.
ABBREVIATIONSBMD = bone mineral density; CA = cervical arthroplasty; IAR = instantaneous axis of rotation; LZ = lax zone; PLL = posterior longitudinal ligament; RM-ANOVA = repeated-measures analysis of variance; ROM = range of motion; SZ = stiff zone.
Correspondence Neil Duggal: Western University, London, ON, Canada. firstname.lastname@example.org.
INCLUDE WHEN CITING Published online August 31, 2018; DOI: 10.3171/2018.3.SPINE171248.
Disclosures Dr. Crawford is an employee of and has direct stock ownership in Globus Medical. Dr. Duggal is a consultant for Synergy Disc Replacement Inc., has received clinical or research support from DePuy Synthes for the study described, and has received support from Medtronic for non–study-related clinical or research effort.
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