Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Intradiscal pressure during low-magnitude-high-frequency vibration in a bovine disc degeneration model (#209)

Morten Vogt 1 , Felizitas Figel 1 , Graciosa Quelhas Teixeira 1 , Jan Ulrich Jansen 1 , Cornelia Neidlinger-Wilke 1 , Hans-Joachim Wilke 1
  1. Ulm University, Ulm, Germany

Introduction. Degeneration of the lumbar intervertebral discs (IVDs) is considered a major cause of low-back pain (LBP). Low-magnitude high frequency vibration (LMHFV) is a fitness trend and also used in the treatment of non-specific LBP [1, 2]. In subjects undergoing prolonged bed rest, daily LMHFV for 90 days could reduce the incident of LBP by 46 % [3]. However, in mice, comparable LMHFV led to clear signs of IVD degeneration after 4 weeks [4, 5]. To better understand this conflicting data, intradiscal pressure (IDP) measurements may provide valuable insights into spine loading and degenerative changes [6]. Therefore, the aim of this study was to explore the effect of LMHFV on IDP of healthy bovine discs and the influence of induced degeneration.

Methods. Three bovine IVD groups (n=3-7 IVDs/group) were tested: 1) fresh IVDs, and IVDs cultured for 21 days 2) under control conditions or 3) after induced degeneration by papain injection (13U in 200 ml/IVD) [7]. IDP was measured in IVDs in a 6-well-plate statically loaded with 0.5 kg [8] before and while LMHFV (45 Hz, 0.3 g) was applied. IDP was recorded at 125 Hz with miniature fiberoptic pressure transducers (⌀ 0.6 mm, Fiso Inc, Canada) inside the nucleus under X-ray position control. The raw data of a 10 s window was further analyzed in a self-written script (Matlab 2017b, MathWorks Inc., USA). The mean pressure was calculated for each sample. Mean amplitude was calculated via a root-mean-square envelope to assess the signal spread. Amplitude spectra were generated using Fast-Fourier-Transform. Statistics: Wilcoxon signed-rank test (p<0.05).

Results. The IDP of the fresh discs was not influenced by LMHFV (0.087 bar vs. 0.09 bar, p>0.05). However, the amplitude was significantly increased by LMHFV (0.0056 bar to 0.011 bar, p=0.016) (Fig. 1A). The amplitude spectra of all non-vibrated discs only showed a peak at 0 Hz of exactly the same magnitude as the IDP (Fig. 1B). With vibration, the amplitude spectra showed the peak at 0 Hz, but additionally showed a second peak at 45 Hz (Fig. 1C). After culture, results were similar. The IDP was not changed by LMHFV while the amplitude was increased, albeit not significantly. Again, without LMHFV only the 0 Hz peak occurred, but with LMHFV an additional 45 Hz peak was detected. After simulated degeneration and culture, the IDP was not affected by LMHFV (p>0.05). Interestingly, the amplitude was also not affected and not a single disc showed the 45 Hz peak.

Discussion. For the first time, the effect of LMHFV on IDP was measured. Our main findings are:

1) LMHFV did not increase the pressure level inside the nucleus, but led to 45 Hz IDP oscillations around a similar pressure.

2) Papain degeneration seemed to impair the nucleus´ ability to transfer the 45 Hz vibration.

This may hinder LMHFV from introducing any therapeutic stimulus for mechanosensitive cells in degenerated nuclei and, thus, prevent vibration therapies from exploiting their full potential.

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