Introduction: Mechanical modulation of bone growth plays a key role in progressive musculoskeletal deformities and in the development of new minimally invasive (MI) treatments for moderate scoliosis.

Objective: This in vivo study focuses on determining the influence of dynamic compression parameters on the mechanical modulation of bone growth.

Method: Thirty-two rats (28 d.o.) were divided into four groups: control (n=6), sham (n=6), static (n=6), dynamic (n=14). A 0.2 MPa compression was applied for 15 days on the 7th caudal vertebra. Sustained loading was used in the static group and sinusoidal loading in the dynamic groups: (a) 0.1Hz and 30%; (b) 0.1Hz and 100%; (c) 1.0Hz and 30%. Growth rates and histomorphometry of the growth plate were compared.

Results: Growth rates (μm/day) of the static (30.5) and dynamic (a:30.4; b:29.2; c:29.4) groups showed no significant difference but were reduced compared with shams (37.8). Growth plate height (μm) decreased for both static (150.9) and dynamic (a: 168.9; c: 167.5) groups but increased significantly (185.5) in dynamic group (b) compared with shams (175.5). Hypertrophic cell heights (μm) decreased similarly and significantly in the static group (23.1) and in all dynamic groups (a: 25.9; b: 25.2; c: 24.4) compared with shams (28.6). Proliferative cell densities decreased in the static group, was similar in the dynamic group (a) but increased in dynamic groups (b) and (c), compared with shams; none of the changes were significant.

Conclusion: Static and dynamic loadings, with the same average compression, resulted in similar growth reductions. However, dynamic loadings modulated growth with less damage to the growth plate. Among dynamic loading parameters, increasing magnitude was less detrimental than increasing frequency.

Relevance: A comprehensive understanding of growth plate mechanobiology is essential for developing new MI treatments based on bone growth modulation for scoliosis correction.