Entrapment of the Fifth Lumbar Spinal Nerve by Advanced Osteophytic Changes of the Lumbosacral Zygapophyseal Joint: A Case Report
A 54-year-old female patient had a 6-year history of backache and left sciatica. Five years earlier, she had undergone surgery in another hospital for L4-5 disc herniation. Although her left sciatica subsided, she experienced gradual deterioration of symptoms, including pain, numbness, and weakness in the left leg.\nOn referral to our hospital, the patient's neurological examination showed left L5 radiculopathy. The strengths of dorsiflexion were weak at the ankle and great toe. Light touch sensation was decreased over the dorsum of the left foot and pain was present. The left patellar reflex was decreased, but the Babinski sign was absent. Routine laboratory tests were normal and the patient was not diabetic. On magnetic resonance imaging, there was slight L4-5 disc bulging, but no canal stenosis. Computed tomography (CT) revealed that ossified wall enclosed the left L5 nerve root at the lateral recess (). Sagittal and coronal views also showed ossified wall medially located from the left L5 pedicle (). There were also osteophytic changes in the left L5-S zygapophyseal joint. Left L4-5 partial laminectomy and left L4-5 partial facetectomy had been performed at previous hospital. Osteophytes originating from the left L5-S zygapophyseal joint developed rostrally, along the left L5 nerve root ().\nThe imaging findings could explain the left L5 radiculopathy. It is suggested that abnormal ossification of the left L5 lateral recess derived from the osteophytes in the left L5-S zygapophyseal joint. Left L4-5 unilateral laminectomy and partial facetectomy had been performed and the shoulder of the left L5 nerve root was confirmed. The distal segment of the left L5 nerve root was embedded with abnormal ossified formation that corresponded on CT to the ossified wall at the left lateral recess of L5. We drilled this abnormal ossification to expose the left L5 nerve root (). This ossification continued to the superior left L5 articular process and the distal part of the intervertebral foramina. We carefully decompressed the nerve root from the left lateral recess to the intervertebral foramina (). The fat tissue in the epiradicular sheath disappeared through the intervertebral foramina. Unfortunately, we could not perform histological examination of these ossified tissues. The lateral half of the left L4-5 joint was preserved. Postoperative CT showed removal of the ossified lesion. After surgery, the patient's neurological function improved, and pain in her left leg subsided. Postoperative external fixation continued for three months.