Dynamic response of the cervical spine to posteroanterior mobilisation

Background. Posteroanterior mobilisation is a manual therapy technique that is commonly used in the examination and treatment of neck pain, but little is known about its biomechanical effect. The purpose of this study was to determine the intervertebral movements of the cervical spine produced by posteroanterior mobilisation. Methods. The cervical spines of nineteen healthy subjects were scanned using an open interventional magnetic resonance imaging scanner. Posteroanterior mobilisation forces were applied to the fifth cervical vertebra whilst they were in the prone position. Sagittal images of the spine were obtained before and during mobilisation. Findings. It was shown that posteroanterior mobilisation of the cervical spine generally produced extension of the upper motion segments and flexion of the lower segments. The middle segments were inconsistent in the direction of rotation. The cervical lordosis was found to increase with repeated PA loading cycles. Interpretation. The magnitude of intervertebral movement produced by mobilisation is small. Forces applied at one spinous process produced not only movements at the target vertebra but also movements of the entire cervical spine resulting in an increase in lordosis. Mobilisation should be interpreted as three-point bending of the entire cervical spine, rather than simple gliding of one vertebra upon another.