Effectiveness of cervical zero profile integrated cage with and without supplemental posterior Interfacet stabilization

Abstract

Background: Conditions requiring cervical decompression and stabilization are commonly treated using anterior cervical discectomy and fusion using an anterior cage-plate construct. Anterior zero profile integrated cages are an alternative to a cage-plate construct, but literature suggests they may result in less motion reduction. Interfacet cages may improve integrated cage stability. This study evaluated the motion reduction of integrated cages with and without supplemental interfacet fixation. Motion reduction of integrated cages were also compared to published cage-plate results.

Methods: Seven cadaveric (C2-T1) spines were tested in flexion-extension, lateral bending, and rotation. Specimens were tested: 1) intact, 2) C6-C7 integrated cage, 3) C6-C7 integrated cage + interfacet cages, 4) additional integrated cages at C3-C4 and C4-C5, 5) C3-C4, C4-C5 and C6-C7 integrated cages + interfacet cages. Motion, lordosis, disc and neuroforaminal height were assessed.

Findings: Integrated cage at C6-C7 decreased flexion-extension by 37% (P = .06) and C3-C5 by 54% (P < .01). Integrated + interfacet cages decreased motion by 89% and 86% compared to intact (P < .05). Integrated cages increased lordosis at C4-C5 and C6-C7 (P < .01). Integrated + interfacet cages returned C3-C5 lordosis to intact values, while C6-C7 remained more lordotic (P = .02). Compared to intact, neuroforaminal height increased after integrated cages at C3-C5 (P ≤ .01) and at all levels after interfacet cages (P < .01).

Interpretation: Anterior integrated cages provides less stability than traditional cage-plate constructs while supplemental interfacet cages improve stabilization. Integrated cages provide more lordosis at caudal levels and increase neuroforaminal height more at cranial levels. After interfacet cages, posterior disc height and neuroforaminal height increased more at the caudal segments.

Keywords: Cervical cage; Cervical spine; Integrated fusion; Interfacet fusion; Posterior fusion; Supplemental fixation.

Fig. 1:

Surgical implants used in this study. A) Zero-profile anterior integrated fusion cage (AIC) (CAVUX® Cervical Cage-L, Providence Medical Technology Inc., Lafayette, CA). B) Posterior interfacet fusion cage (CAVUX® Cage-B Cervical Posterior Cage with Ally™ Bone Screw, Providence Medical Technology Inc., Lafayette, CA)

Fig. 2:

Surgical and testing protocol: A) Intact, B) AIC at C6-C7; C) AIC + PCSS at C6-C7; D) addition of AIC at C3-C4 and C4-C5; E) AIC + PCSS at C3-C4, C4-C5 and C6-C7.