Outcome of Decompression Alone for Foraminal/Extraforaminal Entrapment of L5 Nerve Root Through Wiltse Paraspinal Approach.

STUDY DESIGN: Retrospective analysis.

OBJECTIVE OF THE STUDY: The objective of the study was to present the surgical outcome and analyze the prognostic factors for postoperative leg pain after posterior decompression alone for foraminal/extraforaminal L5 entrapment at L5-S1 segment (LSS).

SUMMARY OF BACKGROUND DATA: Disk extrusion, hypertrophy of facet joint, osteophyte of vertebral body, thickened lumbosacral ligament, and collapsed disk lead to form the lumbosacral tunnel which compresses the L5 exiting nerve root. There are few reports discussing the outcome and prognostic factors of posterior decompression alone.

MATERIALS AND METHODS: One hundred two consecutive patients underwent posterior decompressive surgery through Wiltse approach for foraminal/extraforaminal entrapment at LSS, performed by 2 surgeons. Demography and preoperative radiograph were analyzed for 6 parameters: age, pathology, disk height, relative disk height ratio, depth of L5 vertebrae within the pelvis, and coronal wedging angle of the segment. Clinical outcomes were assessed by the Visual Analog Scale score for back and leg pain, Oswestry Disability Index, and modified Macnab criteria. The incidence of medications of anticonvulsants, opioids, epidural nerve root block and revisional surgery at index level were also examined.

RESULTS: This study included 93 patients. The mean follow-up period was 40.6±19.7 months. Thirty-six patients had disk herniation and 57 had stenosis. Preoperative Visual Analog Scale score and Oswestry Disability Index significantly improved at the final follow-up. On the basis of the modified Macnab criteria, 83% of the patients had good outcomes at follow-up. The mean duration of the medications of anticonvulsants or opioids is 27.2±37.4 days (0-210 d). 5 patients (5.4%) were reoperated. Relative disk height ratio <0.8 was associated with worsening of postoperative leg pain (P<0.01).

CONCLUSIONS: Decompression as the only method for foraminal/extraforminal lesion of LSS through Wiltse paraspinal approach provided good clinical results. A large difference of disk height between standing and supine positions is associated with poor clinical outcomes.