Biomechanical evaluation comparing zero-profile devices versus fixed profile systems in a cervical hybrid decompression model: a biomechanical in vitro study

Merritt D. Kinon, Samantha L. Greeley, Jonathan A. Harris, Yaroslav Gelfand, Reza Yassari, Jonathan Nakhla, Rafael De la Garza-Ramos, Pavan Patel, Belin Mirabile, Brandon S. Bucklen

Research output: Contribution to journalArticle

Abstract

BACKGROUND CONTEXT: The use of zero-profile devices and the need for posterior fixation in conjunction with a cervical hybrid decompression model have yet to be investigated. PURPOSE: To compare the biomechanics of zero-profile and fixed profile cervical hybrid constructs composed of anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF). Fixed profile devices included anterior plating, whereas zero-profile devices included integrated screws. STUDY DESIGN: In vitro cadaveric biomechanical study. METHODS: Twelve fresh-frozen cadaveric spines (C2–C7) were divided into two groups of equal bone mineral density, fixed profile versus zero profile (n=6). Groups were instrumented from C3–C6 with either (1) an expandable ACCF device and a static ACDF spacer with an anterior plate (Hybrid-AP) or (2) a zero-profile ACCF spacer with adjacent zero-profile ACDF spacer (Hybrid-Z). Motion was captured for the (1) intact condition, (2) a hybrid model with lateral mass screws (LMS), (3) a hybrid model without LMS, and (4) a hybrid model without LMS following simulated repetitive loading (fatigue). RESULTS: Hybrid-AP with LMS reduced motion in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) by 77%, 88%, and 82%, respectively, compared with intact. Likewise, Hybrid-Z with LMS exhibited the greatest reduction in motion relative to intact in FE, LB, and AR by 90%, 95%, and 66%, respectively. Following simulated in vivo fatiguing, an increase in motion was observed for both groups in all planes, particularly during Hybrid-Z postfatigue condition where motion increased relative to intact by 29%. Overall, biomechanical equivalency was observed between Hybrid-AP and Hybrid-Z groups (p>.05). Three (50%) of the Hybrid-Z group specimens exhibited signs of implant migration from the inferior endplate during testing. CONCLUSIONS: Fixed profile systems using an anterior plate for supplemental fixation is biomechanically more favorable to maintain stability and prevent dislodgement. Dislodgement of 50% of the Hybrid-Z group without LMS emphasizes the necessity for posterior fixation in a zero-profile cervical hybrid decompression model.

Original languageEnglish (US)
JournalSpine Journal
DOIs
StateAccepted/In press - Jan 1 2019

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Keywords

  • Anterior cervical corpectomy and fusion
  • Anterior cervical discectomy and fusion
  • Anterior plating
  • Fixed profile system
  • Integrated screws
  • Zero-profile device

ASJC Scopus subject areas

  • Surgery
  • Orthopedics and Sports Medicine
  • Clinical Neurology

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