XLIF or OLIF cages have to be stabilized by posterior instrumentation (pedicle screws) to make sure the cage does not “slip” out of position before the vertebra heals together. Screws can be placed by various posterior procedures.
The OLIF is designed to distract the vertebral bodies apart. This separation can indirectly reduce the compression of the neural elements in the canal or foramen but this is not guaranteed to fully free the nerve roots. This is called “indirect decompression”.
During the procedure, nerve monitoring is necessary to make sure there is no irritation or injury to the exiting nerve roots that can occur with the placement of the retractor or that too much distraction is not employed as this can on occasion cause a nerve root stretch or compression injury.
These are X-rays before and after of a patient who had a long laminectomy for lower back pain that did not give him relief. This is because his pain was generated from disc degeneration and not canal narrowing (stenosis). The laminectomy makes a TLIF at all levels very difficult so OLIFs were employed at L2-3, L3-4 and L4-5 where a TLIF was utilized at L5-S1.