By: Dr. David Tiberio, Gray Institute
For the past 15-20 years, the importance of the scapula for shoulder and upper extremity function has been almost universally recognized. This should not surprise anyone since the glenoid fossa of the scapula is half of the gleno-humeral joint. In spite of this anatomical fact, the focus of shoulder rehabilitation and training had focused on the humerus. Once research demonstrated, and clinical practice validated, the importance of scapula motion for shoulder function, the options for treating dysfunction were multiplied.
At the Gray Institute, the “truth” that human movement is a chain reaction is a primary principle of Applied Functional Science (AFS). The Chain Reaction Principle would tell us not to stop at the scapula. It becomes logical to look at the next “link” in the chain: the thoracic spine and rib cage (thoracic cage). In watching functional arm movements, it becomes clear that the thoracic cage moves in a coordinated manner with the scapula and arm, providing important contributions to the global movement. This has been documented by Theodoridis and Ruston,1 as well as other researchers.
If the thoracic cage is critical to upper extremity movements, then dysfunction in thoracic spine movement (often asymptomatic) can be the cause of shoulder pain and tissue damage. Thoracic cage limitations directly reduce the contribution of the spine to the global movement, but also restrict the movement of the scapula further compromising the total movement. Kebaetse et al2 demonstrated that asking normal subjects to sit in a slouched position (thoracic kyphosis) substantially altered shoulder function. Compared to the “non-slouched” posture, shoulder abduction decreased by 24 degrees. Even more surprising is the isometric strength measured at 90 degrees of abduction was reduced by 16 percent.
Another principle of AFS is the 3D Principle. The 3D Principle reminds us that all functional movements involve all three planes of motion. This is particularly true in the thoracic spine when motion in the sagittal plane is linked with “coupled” motions in the frontal and transverse planes. The concept of “coupling” is not new, but our understanding of how it works during function is expanding. Patterns of coupling have been described, but there are no absolutes. Willems et al 3 documented the variability of coupling between subjects. Edmonston et al 4 found this same variability and even differences within single subjects. They also showed that the position of the spine in the sagittal plane altered the direction of coupling in many subjects.
If there are no absolutes and the specific combination of motions depends on both the individual, the initial position, and the intended functional movement, it is essential that all movement practitioners have a strategy for examining each client to determine what movement deficits might exist in the thoracic spine. The Analysis and Performance components of 3DMAPS allow the movement specialist to assess the contributions of the thoracic spine to global movements: first primarily in a single plane, and then though various plane combinations. Once the relative success of the different movements is determined, a strategic sequential program of starting with success can be initiated.
- Theodoridis D, & Ruston S. The Effect of Shoulder Movements on the Thoracic Spine 3D Motion. Clinical Biomechanics 2002, 17: 418-421.
- Willems JM, et al. An In Vivo study of the Primary and Coupled Rotations of the Thoracic Spine. Clinical Biomechanics 1996, 11: 311-316.
- Edmondston, SJ, et al. Influence of Posture on the Range of Axial Rotation and Coupled Lateral Flexion of the Thoracic Spine. J. Manipul and Physiol Therapeutics 2007, 30: 193-199.
- Kebaetse M, et al. Thoracic Position Effect on Shoulder Range of Motion, Strength, and Three-Dimensional Kinematics. Arch Phys Med Rehabil 1999. 80: 945-950.