Biomechanical evaluation of DTRAX^® posterior cervical cage stabilization with and without lateral mass fixation

Abstract

IntroductionLateral mass screw (LMS) fixation with plates or rods is the current standard procedure for posterior cervical fusion. Recently, implants placed between the facet joints have become available as an alternative to LMS or transfacet screws for patients with cervical spondylotic radiculopathy. The purpose of this study was to evaluate the biomechanical stability of the DTRAX® cervical cage for single- and two-level fusion and compare this to the stability achieved with LMS fixation with rods in a two-level construct.MethodsSix cadaveric cervical spine (C3–C7) specimens were tested in flexion–extension, lateral bending, and axial rotation to ±1.5 Nm moment without preload (0 N) in the following conditions: 1) intact (C3–C7), 2) LMS and rods at C4–C5 and C5–C6, 3) removal of all rods (LMS retained) and placement of bilateral posterior cages at C5–C6, 4) bilateral posterior cages at C4–C5 and C5–C6 (without LMS and rods), and 5) C4–C5 and C5–C6 bilateral posterior cages at C4–C5 and C5–C6 with rods reinserted.ResultsBilateral posterior cervical cages significantly reduced range of motion in all tested directions in both single- and multilevel constructs (P<0.05). Similar stability was achieved with bilateral posterior cages and LMS in a two-level construct: 0.6°±0.3° vs 1.2°±0.4° in flexion–extension (P=0.001), (5.0°±2.6° vs 3.1°±1.3°) in lateral bending (P=0.053), (1.3°±1.0° vs 2.2°±0.9°) in axial rotation (P=0.091) for posterior cages and LMS, respectively. Posterior cages, when placed as an adjunct to LMS, further reduced range of motion in a multilevel construct (P<0.05).ConclusionBilateral posterior cages provide similar cervical segmental stability compared with a LMS and rod construct and may be an alternative surgical option for select patients. Furthermore, supplementation of a lateral mass construct with posterior cages increases cervical spine stability in single- and multilevel conditions.

Anterior Cervical Pseudarthrosis Treated with Bilateral Posterior Cervical Cages

“…In the current study, an intervertebral cage with teeth locks the facet without the need for supplemental lateral mass fixation and associated soft tissue dissection. Voronov et al 15,16 reported that posterior cages limit cervical segmental motion comparable to a singlelevel plated ACDF and lateral mass screw and rod construct in cadaveric spine specimens. By the current authors' calculation, supplementation of a single-or 2-level ACDF with posterior cervical cages provides a 6-fold increase in stability compared to ACDF alone.…”

Posterior cervical fusion utilizing cages placed bilaterally in the facets for the treatment of the upper cervical adjacent segment disease in the elderly

“…No conclusions regarding C5 root palsy can be drawn from this study; a larger study would be needed to assess the risk of C5 root palsy with various surgical techniques. As demonstrated in the biomechanics study [22], the posterior cervical cages provide similar decreases in range of motion when compared to lateral mass fixation, and have the benefit of avoiding bone removal for root decompression, which may compromise screw purchase. The authors believe that for those patients with radiculopathy and substantial motor deficits or grade 2/5, a direct decompression with foraminotomy is preferred.…”

Multilevel cervical laminectomy and fusion with posterior cervical cages

“…The biomechanical stability achieved by the construct is comparable to that of a posterior LMS systems. [ 18 ]…”

“…[ 16 ] Stabilization achieved after bilateral posterior cervical cage implantation is reported to be similar to anterior cervical discectomy and fusion (ACDF) and lateral mass screws (LMSs) in biomechanical studies. [ 17 18 ] This technique stabilizes the facet with instrumented distraction and achieves indirect posterior cervical nerve root decompression by significantly increasing foraminal area. [ 19 ] Results have supported its safety and efficacy for treatment of single-level cervical radiculopathy.…”