Intended and non-intended kinematic effects of atlanto-axial rotational high-velocity, low-amplitude techniques

• Atlanto-axial kinematics of high-velocity, low-amplitude thrust are analyzed in vitro.
• Atlanto-axial rotation thrusts induce unintended coupled motion components.
• Atlanto-axial rotation thrusts also induce motion at the atlanto-occipital segment.
• Angles during Atlanto-axial thrusts approximate 1° and do not exceed 3.5°.

IntroductionThe study of neck kinematics during high-velocity, low-amplitude manipulations of the atlanto-axial segment is essential to understanding cervical motion mechanisms and their impact and possible risk for soft-tissue injuries during treatment of spine disorders.MethodsTwenty fresh-frozen specimens were tested during manual application of an axial rotation technique.FindingsThe kinematics indicate the thrust induced motion components of approximately 1° at the treated segment around all three axes of the local embedded reference frame. Moreover, an equal amount of axial rotation motion took place at the adjacent atlanto-occipital joint.InterpretationOverall atlanto-axial motion remained below the level of slow regional mobilization of the cervical spine. These findings can be correlated to literature data concerning the limited increase in vertebral artery strain during high-velocity, low-amplitude manipulation.