Atlantoaxial rotatory fixation: Part 1--Biomechanics of normal rotation at the atlantoaxial joint in children.

摘要: Objective: Atlantoaxial rotatory fixation (AARF) remains a recondite entity loosely included under the panoply of cervical trauma. The difficulty in finding precise definition and reliable diagnostic criteria for AARF has been chiefly because lack normative biomechanical data C1-C2 rotation. As Part 1 foundation comprehensive undertaking to define biomechanics, mechanism, diagnosis, classification, management AARF, present study focuses on dynamic behavior C1 C2 during normal voluntary head rotation children. Methods: Twenty-one children 3 11.5 years old underwent computed tomographic examinations from lower clivus base C3 various positions axial angles made by C1, C2, occiput with vertical 0 degrees were recorded, these, separation between (C1-C2 degrees) calculated each position (represented angle) studied. In 18 children, range was 90 -90 degrees, i.e., making full 180-degree turn one side other. first turned then back only half turn. All plotted against corresponding angle create motion curve, which, essence, describes interaction through positions. turns, both individual curves composite curve comprising all constructed. Results: There is high degree concordance rotational subjects undergoing always crosses at or near null point predictable relationship depicted three distinct regions curve: when rotates 23 it moves alone, remaining stationary approximately (the single-motion phase). When 24 65 move together, but faster rate double-motion phase), being pulled yoking ligaments. From onward, exact unison unison-motion phase) fixed, maximum 43 carried exclusively subaxial segments. turn, forward reverse are almost superimposable, suggesting that "yoking" result more than just tensing relaxing ligaments probably also mutual dragging irregular bony surfaces two bones. Conclusion: manner rotation, among relatively narrow variance mean. can thus be used as touchstone which may judged manners pathological interlock "stickiness" could defined AARF.