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Mundis GM, Eastlack RK, Moazzaz P, et al. Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model. Int J Spine Surg. 2015;9:53doi: 10.14444/2053.
Mundis, G. M., Eastlack, R. K., Moazzaz, P., Turner, A. W., & Cornwall, G. B. (2015). Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model. International journal of spine surgery, 953. https://doi.org/10.14444/2053
Mundis, Gregory M, et al. "Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model." International journal of spine surgery vol. 9 (2015): 53. doi: https://doi.org/10.14444/2053
Mundis GM, Eastlack RK, Moazzaz P, Turner AW, Cornwall GB. Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model. Int J Spine Surg. 2015 Oct 22;9:53. doi: 10.14444/2053. eCollection 2015. PMID: 26609508; PMCID: PMC4657610.
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Int J Spine Surg. 2015 Oct 22;9:53. doi: 10.14444/2053. eCollection 2015.

Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model.

International journal of spine surgery

Gregory M Mundis, Robert K Eastlack, Payam Moazzaz, Alexander W L Turner, G Bryan Cornwall

Affiliations

  1. Scripps Clinic Division of Orthopedic Surgery, San Diego, CA ; San Diego Spine Foundation, San Diego, CA.
  2. Orthopaedic Specialists of North County, Tri-City Medical Center Orthopaedic and Spine Institute, Oceanside, CA.
  3. NuVasive, Inc., San Diego, CA.

PMID: 26609508 PMCID: PMC4657610 DOI: 10.14444/2053

Abstract

BACKGROUND: Expandable cages are gaining popularity in anterior reconstruction of the thoracolumbar spine following corpectomy as they can provide adjustable distraction and deformity correction. Rectangular, rather than circular, endcaps provide increased resistance to subsidence by spanning the apophyseal ring; however their impact on construct stability is not known. The objective of this study was to investigate the contribution of expandable corpectomy cage endcap shape (round vs. rectangular) and fixation method (anterior plate vs. posterior pedicle screws) to the stability of an L1 sub-total corpectomy construct.

METHODS: Eight fresh-frozen cadaveric specimens (T11-L3) were subjected to multi-directional flexibility testing to 6 N·m with a custom spine simulator. Test conditions were: intact, L1 sub-total corpectomy defect, expandable cage (round endcap) alone, expandable cage (round endcap) with anterior plate, expandable cage (round endcap) with bilateral pedicle screws, expandable cage (rectangular endcap) alone, expandable cage (rectangular endcap) with anterior plate, expandable cage (rectangular endcap) with bilateral pedicle screws. Range-of-motion across T12-L2 was measured with an optoelectronic system.

RESULTS: The expandable cage alone with either endcap provided significant stability to the corpectomy defect, reducing motion to intact levels in flexion-extension with both endcap types, and in lateral bending with rectangular endcaps. Round endcaps allowed greater motion than intact in lateral bending, and axial rotation ROM was greater than intact for both endcaps. Supplemental fixation provided the most rigid constructs, although there were no significant differences between instrumentation or endcap types.

CONCLUSIONS: These results suggest anterior-only fixation may be adequate when using an expandable cage in a sub-total corpectomy application and choice of endcap type may be driven by other factors such as subsidence resistance.

Keywords: Corpectomy; Stability; biomechanics; endcap shape; expandable cage

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