The opening size of the laminoplasty is dependent on the groove size: A numerical study

The expansion of the cervical vertebrae lamina appears to be crucial to related surgical procedures. The dimensions of the groove influence the strain concentration within the lamina of the vertebra and, thus, the potential success or failure of respective surgical procedure. The aim of this computational study is to clarify both the role of the size of the groove with concern to both the open door and the double door laminoplasty techniques.

Finite element models were created via computer tomography with varying lamina groove dimensions. Displacements were applied to the models at the open side of the vertebral arch and the vertebral body was constrained prior to movement along all the axes. The maximal opening size measured on the inner side of the lamina and the percentage increase in the initial spinal areas were subsequently analyzed.

The elastic strain concentration value was observed for the groove in all cases, while the maximal principal elastic strain concentration value was observed at the opposite side to the groove cut into the lamina, also in all cases. The maximal area increase related to the 4 mm groove accompanied by the preservation of the ventral cortex of the bone.

The study suggested three conclusions a) the wider the groove, the greater is the opening potential, b) the maximal opening size following laminoplasty is not dependent on the depth of the bone cut for this type of groove, c) no benefit accrues in terms of the opening size following the cutting of a supplementary groove at the beginning of the lamina.