Biomechanical comparison of a two-level anterior discectomy and a one-level corpectomy, combined with fusion and anterior plate reconstruction in the cervical spine Kamran Aghayev a,b , James J. Doulgeris a,d , Sabrina A. Gonzalez-Blohm a, ⁎, Mohammed Eleraky a,b , William E. Lee III c , Frank D. Vrionis a,b a H. Lee Moffitt Cancer Center & Research Institute, NeuroOncology Program, Tampa, FL 33612, USA b Department of Neurosurgery and Orthopedics, College of Medicine, University of South Florida, Tampa, FL 33612, USA c Dept. of Chemical & Biomedical Engineering, University of South Florida, Tampa, FL 33612, USA d Dept. of Mechanical Engineering, University of South Florida, Tampa, FL 33612, USA abstract article info Article history: Received 16 May 2013 Accepted 22 October 2013 Keywords: Anterior cervical discectomy and fusion (ACDF) Anterior cervical corpectomy and fusion (ACCF) Range of motion (RoM) Energy loss Background: Common fusion techniques for cervical degenerative diseases include two-level anterior discectomy and fusion and one-level corpectomy and fusion. The aim of the study was to compare via in-vitro biomechanical testing the effects of a two-level anterior discectomy and fusion and a one-level corpectomy and fusion, with an- terior plate reconstruction. Methods: Seven fresh frozen human cadaveric spines (C3–T1) were dissected from posterior musculature, preserving the integrity of ligaments and intervertebral discs. Initial biomechanical testing consisted of no-axial preload and 2 Nm in flexion-extension, lateral bending and axial rotation. Thereafter, discectomies were performed at C4–5 and C5–6 levels, then two interbody cages and an anterior C4–C5–C6 plate was implanted. The flexibility tests were repeated and followed by C5 corpectomy and C4–C6 plate reconstruction. Biomechanical testing was performed again and statistical comparisons among the means of range of motion and axial rotation energy loss were investigated. Findings: The two-level cage-plate construct had significantly lower range of motion than the one-level corpectomy- plate construct (P ≤ 0.03). Axial rotation energy loss was significantly (P ≤ 0.03) greater for the corpectomy-plate construct than for the two-level cage-plate construct and the intact condition. Interpretation: A two-level cage-plate construct provides greater stability in flexion, extension and lateral bending motions when compared to a one-level corpectomy-plate construct. A two-level cage-plate is more likely to main- tain axial balance by reducing the energy lost in axial rotation. © 2013 Published by Elsevier Ltd. 1. Introduction Two-level cervical degenerative disease is a common condition in clinical practice and two treatments for this condition are: two-level anterior cervical discectomy and fusion (ACDF) and one-level anterior cervical corpectomy and fusion (ACCF). ACCF is a preferable procedure when the spinal cord compression is located behind the vertebral body (Goldberg and Hilibrand, 2003; Pickett et al., 2008), especially when ossification is present (Hwang et al., 2007). Alternatively, ACDF is preferable when the primary lesion is at the disc level (Goldberg and Hilibrand, 2003). Patients are often categorized in a “gray zone” where the superiority of the clinical outcomes of one procedure with respect to the other is difficult to determine. The ambiguity between treatments creates a debate on the clinical impact and superiority. Several pathological factors should be considered for selecting the most appropriate surgical procedure, such as the extent and location of the spinal cord compression and pre-existing cervical deformities (Fraser and Hartl, 2007; Papadopoulos et al., 2006). However, investiga- tions on the biomechanical performance between the two conditions under specific in vitro scenarios can also provide substantial informa- tion. For example, a stable construct is believed to have greater chance of successful bony fusion and less likelihood of hardware migration or dislodgement. In other words, changes in range of motion (RoM) can be interpreted in terms of possible instability and the amount of energy lost (estimated from a load-displacement curve) can also provide infor- mation about the likelihood of maintaining a “corrected” balance after surgery. Thus, including biomechanical factors into the evaluation can help spine surgeons decide between two or more possible surgical treatments. The main rationale for corpectomy is to reduce the number of fusion surfaces but, to our knowledge, no conclusive evidence supports that the incidence of nonunion is higher in a 2-level ACDF than in a 1-level Clinical Biomechanics 29 (2014) 21–25 ⁎ Corresponding author. E-mail address: sabrina.gonzalezblohm@moffitt.org (S.A. Gonzalez-Blohm). 0268-0033/$ – see front matter © 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.clinbiomech.2013.10.016 Contents lists available at ScienceDirect Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech