Dynamic changes of the ligamentum flavum in the cervical spine assessed with kinetic magnetic resonance imaging.

The purpose of this article is to quantify changes in thickness of the ligamentum flavum (LF) associated with motion of the cervical spine and to compare the thickness of the LF at each cervical level using kinetic magnetic resonance imaging (kMRI). Two hundred fifty-seven symptomatic patients (129 men; 128 women) underwent kMRI in neutral, flexion, and extension positions. Midsagittal images were digitally marked and electronically analyzed by spine surgeons. Thickness of LF in the cervical region from C2-3 to C7-T1 was measured in all three positions. LF at C7-T1 was significantly thicker than C2-3 to C6-7 in neutral, flexion, and extension positions (p < 0.05). LF was significantly thicker in extension than in flexion at C3-4 to C6-7. LF thickness increases with extension and decreases with flexion. LF is uniquely thick at C6-7 and at C7-T1 in the extension position, which may predispose these levels to cord compression syndromes and associated neuropathies.