Three-dimensional spinal coupling mechanics: Part I. A review of the literature

To determine the state of knowledge relative to three-dimensional spinal coupled motion and to check the validity of currently accepted two-dimensional coupling as taught in chiropractic.

A hand search of available reference texts and a computer search of literature from Index Medicus were collected with an emphasis on three-dimensional studies of human spinal movements.

Most postural movements result in complicated three-dimensional spinal coupling in six degrees of freedom. Previous spinal coupling results based upon two-dimensional radiographic studies are inadequate and inaccurate. It is important that chiropractic colleges and techniques use the three-dimensional spinal kinematics to update their curricula and advance chiropractic treatment procedures.

Full three-dimensional investigations of spinal coupling patterns have shown that the vertebrae rotate and translate in all three axes and that previous theories of spinal coupling based upon two-dimensional studies are inaccurate and invalid. Postural rotations and translations, which are the main motions studied in spinal coupling research, and altered configurations of the normal sagittal plane curves are the cause of both normal and abnormal spinal coupling patterns in three dimensions. Chiropractic letter listings (such as PRS, ASRP, etc.) are outdated, incomplete, invalid representations of coupled segmental movements. Mechanical loading of the neuromusculoskeletal tissues plays a vital role in position, dynamics, proper growth, repair and symptoms. Future studies of spinal kinematics should study the postural translations of the skull and thorax for their associated coupling in three dimensions. Combined postural rotations and translations along with altered sagittal curvatures need to be studied for their associated coupling characteristics as well.