Vertebral deformity arising from an accelerated "creep" mechanism

Luo, Jin ORCID: https://orcid.org/0000-0001-5451-9535, Pollintine, P, Gomm, E, Dolan, P and Adams, MA (2012) Vertebral deformity arising from an accelerated "creep" mechanism. European Spine Journal, 21 (9). pp. 1684-1691. ISSN 0940-6719

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Abstract

Introduction

Vertebral deformities often occur in patients who recall no trauma, and display no evident fracture on radiographs. We hypothesise that vertebral deformity can occur by a gradual creep mechanism which is accelerated following minor damage. “Creep” is continuous deformation under constant load.
Materials and methods

Forty-five thoracolumbar spine motion segments were tested from cadavers aged 42–92 years. Vertebral body areal BMD was measured using DXA. Specimens were compressed at 1 kN for 30 min, while creep in each vertebral body was measured using an optical MacReflex system. After 30 min recovery, each specimen was subjected to a controlled overload event which caused minor damage to one of its vertebrae. The creep test was then repeated.

Results

Vertebral body creep was measurable in specimens with BMD <0.5 g/cm2. Creep was greater anteriorly than posteriorly (p < 0.001), so that vertebrae gradually developed a wedge deformity. Compressive overload reduced specimen height by 2.24 mm (STD 0.77 mm), and increased vertebral body creep by 800 % (anteriorly), 1,000 % (centrally) and 600 % (posteriorly). In 34 vertebrae with complete before-and-after data, anterior wedging occurring during the 1st creep test averaged 0.07° (STD 0.17°), and in the 2nd test (after minor damage) it averaged 0.79° (STD 1.03°). The increase was highly significant (P < 0.001). Vertebral body wedging during the 2nd creep test was proportional to the severity of damage, as quantified by specimen height loss during the overload event (r 2 = 0.51, p < 0.001, n = 34).

Conclusions

Minor damage to an old vertebral body, even if it is barely discernible on radiographs, can accelerate creep to such an extent that it makes a substantial contribution to vertebral deformity.

Item Type: Article
Additional Information: This is a post-peer-review, pre-copyedit version of an article published in European Spine Journal. The final authenticated version is available online at: https://dx.doi.org/10.1007/s00586-012-2279-y
Uncontrolled Keywords: vertebral deformity; fracture; creep; BMD; cadaveric; damage
Subjects: Construction and engineering > Biomedical engineering
Medicine and health
Medicine and health > Physiology
Related URLs:
Depositing User: Jin Luo
Date Deposited: 08 May 2020 18:59
Last Modified: 09 May 2020 12:36
URI: http://repository.uwl.ac.uk/id/eprint/6907

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