A comparison between anterior threaded cages vs. Posterior pedicle screw instrumentation in terms of foraminal distraction and lumbar lordosis

A cadaveric study was performed to compare the effect of anterior versus posterior distraction instrumentation on lumbar foraminal height and lordosis. Pedicle screws and interbody instrumentation can be used to distract vertebral bodies, thereby increasing foraminal height. BAK interbody cages were inserted anteriorly at L4-L5 and L5-S1 in ten spines. Isola instrumentation was applied posteriorly in six spines at L4, L5, and S1. Both anterior instrumentation and posterior pedicle screw instrumentation provided significant increase in foraminal height with slight decrease in total lumbar lordosis. Foraminal height increased with larger cages at the level in which the cages were first applied, and the addition of cages at the neighboring level had a little effect. However, no statistically significant differences were found with different sizes of cages at the neighboring level. The maximum change in foraminal height occurred with 10 mm of posterior distraction, but a plateau effect was observed over six mm. Distraction of the lumbar spine is effective in increasing foraminal height with relatively small losses of lumbar lordosis. Similar increases were obtained with the anterior and posterior approaches. The surgeon should choose a particular method based on the patient's pathology.