Abstract
Objective. To assess the friction at the thoracic skin–fascia interface to determine the potential
reaction force vectors during thoracic manual therapy.
Design. A basic in vivo study of human subjects, documenting the frictional properties at
the interface between the thoracic skin and underlying fascia.
Background. Chiropractors, and other spine manipulative therapists, during thoracic manipulation
have been attempting to apply force vectors to spine tissues in specific directions
in addition to those applied normal to the skin. For obliquely applied forces to be
directly transmitted to the underlying vertebrae, either friction is required at the
skin–fascia interface or the applied force must “hook” on a bony process.
Methods. Subjects were placed in the prone position with the thoracic skin exposed. The posterior
thoracic region was loaded with normal forces, incrementally from 125.3 to 392.9 N.
The interface between the load and the skin was either a plexiglass plate or modelled
hands. A force was then applied to either apparatus in the cephalad direction. The
applied forces and corresponding displacements were measured using a load cell and
an optoelectronic camera system, respectively. Chiropractors then performed actual
thoracic manipulation to determine if they could maintain their location of contacts
(spinous process/transverse process) on the underlying vertebra.
Results. Each of the subjects exhibited negligible friction between the thoracic skin and
underlying fascia for both the plexiglass and modelled hand contacts. Furthermore,
in each case, the apparatus travelled a distance greater than that between two transverse
or spinous processes without showing an abrupt change in the slope of the force–displacement
curves. The hands of chiropractors performing thoracic manipulation travelled a similar
distance during the dynamic thrust.
Conclusions. The skin–fascia interface over the thoracic spine exhibits negligible friction.
Therefore, the reaction force from a thoracic vertebra will be normal to the overlying
skin. Furthermore, the data show that the ability to “hook” either a thoracic transverse
or spinous process in the superior–inferior direction during a manipulative thrust
may be greatly over-rated.Relevance
During thoracic spinal manipulation, one cannot direct a force vector to a thoracic
vertebra at a given angle by simply directing their thrust in that direction.
Keywords
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to Clinical BiomechanicsAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Chiropractic technique: principles and procedures. first ed. Churchill Livingston Inc, New York1993: 347
- Thoracic and costovertebral subluxation syndromes.in: Gatterman M.I. Foundations of chiropractic subluxation. Mosby, St.Louis1995: 407
Szaraz ZT. Compendium of chiropractic technique. Division of Chiropractic Sciences, Canadian Memorial Chiropractic College, 1990
- Forces required to cause cavitation during spinal manipulation of the thoracic spine.Clin. Biomech. 1993; 8: 210-214
- Forces exerted during spinal manipulative therapy.Spine. 1993; 18: 1206-1212
- Two-dimensional mechanical properties of rabbit skin-II. Experimental results.J. Biomech. 1974; 7: 171-182
- Two-dimensional elastic properties of human skin in terms of an incremental model at the in vivo configuration.Med. Eng. Phys. 1995; 17: 304-313
- The stress–strain relationship for the skin.J. Biomech. 1976; 9: 649-657
- Material properties of commonly-used interface materials and their static coefficients of friction with skin and socks.J. Rehabil. Res. Dev. 1998; 35: 161-176
- In vivo friction properties of human skin.Prosthet. Orthot. Int. 1999; 23: 135-141
Article info
Publication history
Accepted:
February 4,
2002
Received:
September 14,
2001
Identification
Copyright
© 2002 Elsevier Science Ltd. Published by Elsevier Inc. All rights reserved.
