Manual Therapies—A Biomechanical Continuum
John J. Triano, D.C., Ph.D., F.C.C.S., Research Professor, Department of Engineering, University of Texas, Arlington, Co-director for Research, Texas Back Institute, Texas
Over 200 different named systems of manual treatments exist worldwide. Systems are often clustered under headings of massage, neuromuscular therapy, mobilization and high velocity, low amplitude manipulation procedures. Common to all of them is the application of forces and moments to patient body segments, expecting to influence soft-tissue condition or joint behavior, physiologic responses and associated symptoms. These loads may serve both in efforts to diagnose and to treat. Successful transfer of mechanical energy into positive clinical change is likely to rely on the match of procedure characteristics common to all treatments (threshold, dose and duration) and biomechanical properties of the affected tissues. In theory, transduction mechanisms may include the altering of local tissue constitutive properties and fluid content, cellular or reflex reactions.
Manual therapies have multiple parameters that can be independently controlled for each administration including relative body segment orientation, static or dynamic initial conditions, application area concentration, frequency, preload amplitudes, direction, load rise-time, peak amplitudes, and sustained load duration. Little information currently exists on the association of changes in these parameters with threshold-dose relationships.
During this session, the several types of studies used to quantify some of the more common procedures will be reviewed. Thus far, only a small number of diagnostic and therapeutic procedures have received attention. Efforts have been made to quantify in vitro intradiscal pressures, point loads at select landmarks of the motion segment, ligamentous and arterial strains. Acoustic and acceleration sensors have triangulated joint cavitation with respect to targeted joint structures. Kinematics has been monitored in vitro with bone pins and in vivo by optoelectronic sensors and MRI in some diagnostic and therapeutic maneuvers. Uniaxial or triaxial loads at the applied site for the cervical, thoracic and lumbar regions have been reported. Force and moment components transmitted through the targeted body segment slice for the low back and neck are available. Analytic methods have explored kinetoelastostatic, direct and inverse dynamic as well as vibrational and energy models.
Understandably, the descriptive biomechanical data has grown most quickly over the past two decades, forming the basis for future work. Efforts to understand the transduction of input energy to physiologic processes has lagged behind. Early efforts sought threshold relationships with circulating biological markers and recent evidence has begun to map load intensity and direction to neural response. The role of skill in performance is just beginning to be investigated. Variability between operators is evident in cross-sectional studies. Within an operator’s performance, early evidence suggests a systematic variation and reproducibility in response to patient characteristics.
Future work must build an understanding of the differences in procedures and identify markers for mechanical transduction, carrying studies more expansively into mapping the relationship of the controllable biomechanical parameters of the various manual methods to physiologic and, ultimately, clinical effects.