Effect of applied spinal manipulation force direction on vertebral accelerations: An in vivo ovine study
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Published on: May 25, 2017
Objective:
The purpose of this study was to determine the effect of varying spinal manipulative thrust (SMT) applied force angle on vertebral accelerations in an in vivo ovine model.
Methods:
Twelve healthy young Merino sheep (mean 24 kg, SD 3 kg) were tested under institutional ethics approval. Tri-axial accelerometers rigidly attached to intraosseous pins at L2 and L4 spinous processes quantified vertebral accelerations during SMTs delivered to L3 at 3 force vectors: 90° (posteroanterior), 60° (cephalad), and 120° (caudal). Thirteen SMTs (∼200 N peak force) were applied at ∼6 Hz per condition across 3 randomized repeated-measures trials. Peak-to-peak (p-p) accelerations were compared among force directions using 1-way analysis of variance.
Results:
Significantly increased p-p accelerations were observed for caudally directed (120°) thrusts at both L2 and L4 (P < .01), as well as at the L2-L4 segmental transfer level. Cephalad thrusts (60°) produced greater L2 than L4 accelerations; caudal thrusts (120°) produced greater L4 than L2 accelerations.
Conclusion:
The applied force direction significantly influences segmental and adjacent-segment vertebral accelerations, with implications for optimizing line-of-drive selection in clinical SMT practice.
