Efficacy of Oblique Lateral Interbody Fusion at L5/S1 for Lumbosacral Transitional Vertebrae-Related Far-Out Syndrome: A Report of Two Cases

Far-out syndrome is often related to lumbosacral transitional vertebrae (LSTV) and can result in L5 radiculopathy. Although conservative treatment can resolve the radiculopathy, surgical treatment should be considered when the symptoms are refractory. Several surgical procedures, including facetectomy with fusion surgery and nerve root decompression via the anterior or posterior approach, have been described. However, research regarding the efficacy of oblique lumbar intervertebral fusion at L5/S1 (OLIF51) to resolve far-out syndrome is limited. This case report aimed to report the efficacy of this surgery. OLIF51 was performed for two patients with far-out syndrome. The first patient (an 81-year-old man) had undergone posterior lumbar intervertebral fixation from L3 to L5 for degenerative lumbar spondylosis. The right refractory L5 radiculopathy persisted after surgery. As the L5 radiculopathy might have resulted from LSTV, posterior nerve decompression surgery was performed. However, the symptoms recurred after one month, and OLIF51 was performed to decompress the L5 nerve root in the anterior exit zone. The second patient (a 46-year-old man) had a disc herniation at L4/5, which was treated surgically five months prior. Because the right L5 radiculopathy related to LSTV persisted, OLIF51 was performed. Following OLIF51, the L5 nerve root radiculopathy disappeared in both cases. Both patients have been followed up at the outpatient clinic, and their symptoms have not recurred for 12 and 10 months in the first and second patients, respectively. OLIF51 can effectively resolve far-out syndrome related to LSTV.