Abstract
Abstract
Background
Spinal manipulative therapy (SMT) clinical effects are believed to be linked with its force-time profile characteristics. Previous studies have revealed that the force measured at the patient-table interface is most commonly higher than the force applied at the clinician-table interface. The factors explaining this force amplification remains unclear.
Objective
To determine the difference between the force applied on cadaveric specimen’s thoracic spine and the resulting force measured by a force-sensing table as well as to evaluate the relationship between this difference of force and both the SMT force-time characteristics and the specimen characteristics.
Methods
Twenty-five SMTs with different force-time profiles were delivered by an apparatus at the T7 vertebra of 9 human cadaveric specimens lying prone on a treatment table instrumented with a force plate. The difference between the force applied by the apparatus and the resulting force measured by the force plate was calculated (Fdiff). Difference in force was also expressed as the percentage of the applied force (Fdiff%). Kinematics markers were inserted into T6 to T8 spinous and transverse processes to evaluate vertebral displacements during SMT thrusts. Mixed-effects linear models were conducted to evaluate the variance in Fdiff and Fdiff% explained by SMT characteristics (peak force, thrust duration and rate of force), T6 to T8 relative and total displacements, and specimens’ characteristics (BMI, height, weight, kyphosis angle, thoracic thickness).
Results
Sixty percent of the trials showed lower force measured at the force plate than the one applied at T7. Fdiff¸ was significantly predicted (R2marginal = 0.54) by peak force, thrust duration, thoracic thickness and T6-T7 relative displacement in the z-axis. Fdiff% was significantly predicted (R2marginal = 0.56) by rate of force application, thoracic thickness and T6 total displacements. For both dependant variables, thoracic thickness showed the highest R2marginal out of all predictors.
Conclusion
Difference in force between the clinician-patient and the patient-table interfaces is influenced by SMT force-time characteristics and by the thoracic thickness. How these differences in force are associated with vertebral displacements remains unclear. Future investigations should measure SMT force-time profiles at both interfaces and normalization with thoracic thickness should be considered when measuring force at the patient-table interface.
Publisher
Research Square Platform LLC