PMC5974679_01
Sagittal view and axial view of magnetic resonance imaging (MRI). Sagittal view (a) and axial view (b) ofMRI indicates no stenosis and compression lesion at the dura and nerve root in the canal.
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F3
Computed tomography (CT) showed a free ossification lesion in the foramen and ossification of the yellow ligament at L4-L5, without a ragged edge (Fig. 2).
Microendoscopic images during surgery. A part ofthe ossification lesion (dash line) and the nerve root (asterisk) are exposed before excision (a). An ultrasonic bone curette (white star) is applied to remove the ossification lesion and decompress the nerve root (asterisk) (b). After excision ofthe ossification lesion, spaces could be observed at both the cranial and caudal sides of the nerve root (asterisk), and the nerve root is relaxed (c).
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F4
Magnetic resonance imaging revealed no compression and stenotic lesion in the canal or fibrocartilaginous mass (Fig. 3).
Computed tomography (CT) after surgery. CT shows the absence of an ossification lesion at 45 months after surgery.
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F5
After removing the caudal side of the left L4-TP by drilling using a diamond bur and the inter-TP ligament, a part of the ossification lesion and the nerve root were exposed (Fig. 4a). Stryker Corp., Kalamazoo, MI, USA) was applied to remove the ossification mass (Fig. 4b). The deep lesion near the entrance zone was carefully treated. After decompression by resection of the ossification lesion, the nerve root was found to be relaxed (Fig. 4c).The surgical time was 83min, and blood loss was only 5g. She mentioned that there was no leg symptom immediately after the surgery and could walk without an aid on the next day of the surgery. According to the Japanese Orthopedic Association scoring system, her score improved from 21/29 preoperatively to 29/29 postoperatively, and the full score was maintained at the final observation 45 months after the surgery.
An image of an ultrasonic bone curette. The tip of an ultrasonic bone curette was developed to be bent moderately to use easily under a microendoscope with the property of its 25  oblique view.
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F6
Post-operative CT revealed the absence of an ossification lesion (Fig. 5) and no lumbar instability.