Biomechanics of Stability After Unilateral Facetectomy at L5-S1 Using FacetFuse Transfacet
Pedicle Screw Alone or in Combination With Contralateral Pedicle Screw Rod Fixation*
K.R. Chin, M.T. Reis, P.M. Reyes, S.C. Anagnost, V.P. Kushwaha, J.P. Gabriel, S.C. Meyer, C.A. Bruce, W.D. Yu, N.R. Crawford
Barrow Neurological Institute, Spinal Biomechanics, Phoenix, AZ 85013 (N.R. Crawford)
Institute for Modern & Innovation Spine Surgery, Fort Lauderdale, FL 33311 (K.R. Chin)
*Preliminary Research
Background Context
Fixation across the lumbosacral segment is challenging and is made worse with unilateral facetectomy for transforaminal interbody placement or for severe stenosis. No study has previously investigated biomechanics of stabilization at L5-S1 when using combined facet screw fixation (FF) and pedicle screw-rod fixation (PS), either in the intact spine or after unilateral facetectomy.
Purpose
To assess the stability after FF or combined FF+PS in the intact condition and after facetectomy at L5-S1.
Study Design/Setting
Paired in vitro nondestructive flexibility comparison in specimens instrumented at L5-S1 with FF or combined FF and PS.
Patient Sample
Two human cadaveric L2-S1 specimens were studied, with motion assessed at L5-S1.
Outcome Measures
Range of motion (ROM) during flexion, extension, axial rotation, and lateral bending was compared in multiple conditions.
Methods
Specimen flexibility was tested by applying nonconstraining nondestructive pure moments (7.5 Nm maximum) while recording specimen motion optoelectronically in 3D. Specimens were tested (A) intact, (B) after bilateral L5-S1 FF+TLIF, (C) after FF on the left and PS on the right (TLIF), (D) after FF on the left+TLIF (PS disengaged), (E) after facetectomy with FF L+PS R+TLIF, (F) facetectomy with FF L+TLIF.
Results
Facetectomy and stabilization with unilateral FF Only allowed greater ROM in all modes than facetectomy and stabilization with L FF+R PS.
Discussion & Conclusion
Our preliminary results suggest that unilateral facetectomy destabilizes the segment and that contralateral facet fixation alone offers much less stability than having a hybrid of contralateral facet fixation and ipsilateral pedicle screw fixation on the facetectomy side.
Reference
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