Spinal ligament loading during axial distraction: a biomechanical model.

The objective of this study was to develop a method of measuring spinal ligament forces during axial distraction to understand the load-bearing contributions of the individual ligamentous structures in the lumbar spine. A sequential ligament-cutting technique and the arthroscopically implantable force probe (AIFP, MicroStrain, Burlington, VT) were used to determine loading of the anterior longitudinal ligament (ALL), the posterior longitudinal ligament (PLL), and the remaining posterolateral complex (PLC) in an in vitro corpectomy model. During axial spinal distraction, the relative percentages of the total axial load in the individual structures were as follows: ALL, 37.5%; PLL, 17.2%; PLC, 45.3%.