Это из названия статьи. Полностью звучит так:
“Relative 3 Dimensional Motions between End Vertebrae in a Bi-level construct, the Effect of Fixture Constraints on Test Results”
Речь идет о спинальных имплантатах.

Спасибо!

"Definition: Cephalad end vertebra: The first vertebra in the cephalad direction from a curve apex whose superior surface is angled maximally toward the concavity of the curve, as measured in the PA spinal projection. Caudad end vertebra: the first vertebra in the caudad direction from a curve apex whose inferior surface is angled maximally toward the concavity of the curve, as measured in the PA spinal projection."

http://www.srs.org/professionals/online-education-and-resources/glossary/three-dimensional-terminology-of-spinal-deformity#5

Спасибо!