[Effect of a compression load on intradiscal pressure of the cervical spine: in vitro investigation].

Background And Purpose: The aim of this paper was to investigate the effects of intervertebral fusion (Cloward and Robinson-Smith techniques) on the intradiscal pressure at the adjacent levels exposed to compression loads.

Material And Methods: A biomechanical study was performed using cadaveric cervical spine. 12 cervical spines exposed to a compression load were analyzed. Intact spines and spines after internal stabilisation using bone grafts and metal plates were already studied. All biomechanical testing was performed on the material testing machine (MTS 858 MiniBionix Test System).

Results: The results of investigation confirmed a linear distribution of pressure related to the applied compression loads. This study showed that intradiscal pressure was always inferior in the disc above the stabilisation segment as compared to the disc underneath (even by 49%), regardless of the investigated system (intact spine or spine with a fixator). Intradiscal pressure in the spine with a bone graft, using Cloward technique or Robinson-Smith techniques, did not show significant differences between the two methods of stabilisation. Additionally, stabilisation (in the form of a fixator plate) did not show an essential influence of the fixator on changes of the intradiscal pressure.

Conclusion: Clinical studies have reported increased rates of disc degeneration at levels adjacent to fusion. The results presented in this paper have not shown a significant increase of the intradiscal pressure at the adjacent levels after stabilisation.