The role of cage height on the flexibility and load sharing of lumbar spine after lumbar interbody fusion with unilateral and bilateral instrumentation: a biomechanical study

摘要

One- and two-level lumbar interbody fusion with unilateral instrumentation is as effective as that with bilateral instrumentation. The height of the interbody cage influences the operated segment stability and the fusion technique success. The purpose of this research was to determine the effect of the fusion cage height (i.e. long and short) on both the stability (based on flexibility measures) and load sharing of the unilateral and bilateral instrumented transforaminal lumbar interbody fusion (TLIF) technique. The flexibility and load sharing tests were performed on seven human lumbar spines. Different configurations combining a long or short cage with a unilateral, bilateral, or no posterior fixation were used to stabilize the operated segment. Two sets of modular cages were designed for each type of test to simulate the long and short cages. During the flexibility test, a pure-moment load of 7.5?Nm was applied. The range of motion (ROM) was recorded for flexion–extension, lateral bending, and axial rotation. During the load sharing test, an axial-compression load of 400?N was applied. The load bearing of the cages was recorded using a cage-embedded load cell. When the fusion cage height decreased 2?mm, the segment flexibility with unilateral fixation showed a significant increase in the ROM for flexion–extension, lateral bending, and axial rotation of 74.9, 83.8, and 175.2% (P?