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Surgical approach to ossification of the thoracic yellow ligament
Surgical Approach to Ossification of the Thoracic Yellow Ligament I. Nishiura, M.D.,* T. Isozumi, M.D.,* K. Nishihara, M.D.,* H. Handa, M.D.* and T. Koyama, M.D.† *Division of Neurosurgery, Takeda General Hospital, Kyoto, and †Division of Neurosurgery, Ohtsu Municipal Hospital, Shiga-Prefecture, Japan
Nishiura I, Isozumi T, Nishihara K, Handa H, Koyama T. Surgical approach to ossification of the thoracic yellow ligament. Surg Neurol 1999;51:368 –72. BACKGROUND
Symptomatic ossification of the yellow ligament (OYL) at the lower thoracic level is uncommon. Although wide laminectomy has, until now, been the primary treatment for this disease, we propose a less invasive technique based on a new method of three-dimensional computed tomography (CT). METHODS
The clinical features and radiologic imaging findings of 37 patients with OYL (mean age, 54 years) were analyzed. The surgical approach was selected based on the position of the depicted OYL on 3D CT scan in each patient. RESULTS
The male-to-female ratio was 3:1. Involvement of the upper thoracic region was seen 11 times; of the middle region 8 times, and of the lower region 40 times (several patients had involvement in more than one region). About half of the patients complained of gait disturbance on admission caused by the markedly enlarged OYL. No postoperative complications were found. Neurologic deterioration was observed in only one patient. CONCLUSIONS
OYL should be treated as early as possible, using the least invasive technique available. By using 3D CT, we were able to perform limited surgery consisting of foraminotomy or extended partial laminectomy at the affected level after confirming the anatomic location of the OYL. In laterally extended OYL, it is necessary to decompress the radicular artery in order to prevent ischemic damage to the spinal cord. © 1999 by Elsevier Science Inc. KEY WORDS
Ossification, posterior longitudinal ligament, threedimensional computed tomography, yellow ligament.
Address reprint requests to: Dr. Iwao Nishiura, Division of Neurosurgery, Takeda General Hospital, 28-1 Mori-minami-cho, Ishida, Fushimi-ku, Kyoto, 601-13, Japan. Received July 25, 1997; accepted December 17, 1997. 0090-3019/99/$–see front matter PII S0090-3019(98)00051-2
ssification of the yellow ligament (OYL) at the level of the lower thoracic cord is often asymptomatic or only incidentally detected. When it produces symptoms, however, it frequently takes the form of markedly extensive ossification with extreme compression of the spinal cord. Recent advances in magnetic resonance (MR) imaging have made it easier to diagnose OYL in the early stages. The anatomical relationships among the ossified material and the spinal cord, lamina, and facet joint are now more accurately depicted by reconstructive computed tomography (CT). Thus, at the present time, the ossified material can be removed more easily, and with greater confidence and less invasiveness. We encountered 37 patients with symptomatic OYL in the past 15 years. We performed wide laminectomy during the early period, but more recently we have performed a key-hole foraminotomy (thinning of the lamina and OYL) with or without an additional small laminectomy. This improvement in technique was aided by a new 3D-CT imaging modality. Focusing on this modality, we discuss the problematic aspects of OYL.
O
Methods and Material We encountered 37 patients (mean age, 54 years; male-to-female ratio, 3:1) with symptomatic OYL between 1981 and 1996. All patients underwent operation, and, in all of them, the diagnosis of OYL was histologically confirmed. The preoperative radiologic examinations included myelography and CT myelography, and in the more recently treated patients, CT reconstruction, MR imaging, and 3D-CT imaging were also performed. © 1999 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
Ossification of Thoracic Yellow Ligament
Surg Neurol 369 1999;51:368 –72
A, Preoperative (1) and postoperative (2) CT scans; B, preoperative (1) and postoperative (2) 3D-CT scans. A small area of the OYL (arrows) was removed by bilateral foraminotomy.
1
Results The level of involvement was in the upper thoracic region in 11 patients, the middle region in 8, and the lower region in 40 patients. The OYL was accompanied by lumbar canal stenosis in 4 patients, and by ossification of the posterior longitudinal ligament (OPLL) or other cervical lesions in 8 patients. Neurologic examinations revealed sensory disturbance (58%), motor weakness of the lower extremities (50%), gait disturbance (75%), and bladder dysfunction (17%). In all patients, the OYL was detected by CT myelography, which showed dural deformity (30%), cord deformity (50%), or only dural contact with the OYL (20%). In most patients, the OYL was of the symmetrical or unilaterally localized type, but three patients showed the rare medial type of OYL [10]. No postoperative complications were found. Neurologic deterioration was observed in only one patient.
Case Reports Four representative cases are presented. CASE 1 A 53-year-old man had noticed dysesthesia of his legs and dysuria for about 2 years. He gradually developed gait disturbance during the year immediately preceding his admission. Neurologic examination on admission revealed hypesthesia, hypalgesia below the T12 level, normal strength of his extremities, exaggeration of
both knee and ankle reflexes, positive bilateral Babinski sign, spastic gait, and neurogenic bladder. Myelography revealed poor filling of the contrast medium from T10 to T12. CT myelography disclosed bilateral OYL with mild cord compression at the level of T10 –T11 (Figure 1A1). MR imaging also revealed spinal cord compression due to the OYL only at this level. Bilateral foraminotomy at T10 –T11 was performed. After the dura was exposed near the midline, a part of the OYL was detected under the medial region of the upper third of the superior facet. The OYL was thinned, using an air drill, and easily removed. By 2 weeks after the operation, the bladder dysfunction had resolved and the spastic gait improved. Postoperative CT scanning disclosed that the OYL had been totally removed (Figure 1A2). CASE 2 A 70-year-old man complained of dysesthesia and weakness of the left hand that had begun 1 month previously and had gradually spread to both lower extremities. Neurologic examination on admission revealed weakness of bilateral upper and lower extremities, hypesthesia and hypalgesia of the palmar region, and hyperreflexia of the patellar tendon reflex and Achilles tendon reflex. The myelogram and CT scan disclosed compression of the spinal cord at two widely separated levels: cervical disc hernia at C4 –C5 and thoracic disc (T10 –T11) hernia from the ventral side with
370 Surg Neurol 1999;51:368 –72
Nishiura et al
A, Preoperative CT scan; B, preoperative CT myelogram; and C, postoperative CT scan. A small area of the OYL was removed by partial laminectomy following bilateral foraminotomy (arrow, a herniated thoracic disc)
2
accompanying OYL on the dorsal side (Figure 2 A and B). Three weeks after operation for the herniated cervical disc, the ossified portion of the yellow ligament was removed, followed by bilateral foraminotomy at T10 –T11 (Figure 2C). The thoracic disc was left untouched because the main causes of the patient’s symptoms were thought to be the cervical disc herniation and the OYL at T10 –T11. Starting 1 week after the first operation, the spastic gait improved rapidly, and 3 weeks after the second operation, the dysesthesia began to subside gradually. CASE 3 A 56-year-old woman complained of a 2-year history of lumbago with subsequent development of pain in the right lower extremity. She also had a 1-year history of weakness of this extremity, followed by spastic limping gait. Neurologic examination on admission revealed motor weakness of the right leg, hyperreflexia, and bilateral clonus. No sensory disturbance was found.
A, Plain CT; B, CT myelogram; and C, 3D-CT scan. OYL (arrows) at two levels is clearly demonstrated on 3D-CT.
3
CT myelography revealed OYL at T9 –T10 and T10 –T11 (Figure 3). MR imaging disclosed no intramedullary lesion. Hyperreflexia, probably caused partly by compression of the radicular artery by the OYL at the intervertebral foramen, was noted. After partial laminectomy following foraminotomy was performed, the laterally extended OYL was seen from the contralateral side. Adequate decompression of the radicular artery was obtained. Her leg pain disappeared promptly after the operation. However, the weakness of the lower extremity did not improve. CASE 4 A 71-year-old man had fallen down while inebriated. Immediately after the accident, he could not move his extremities, but his condition then improved gradually to the level of the left hemiparesis in 3 days. Neurologic examination on admission revealed left hemiparesis, hypesthesia and hypalgesia below the C4 level, and exaggerated reflexes of the lower extremities. Plain X-ray and MR images revealed
Ossification of Thoracic Yellow Ligament
Surg Neurol 371 1999;51:368 –72
A, MR image; B, preoperative (1) and postoperative (2) 3D-CT scans showing an inside view of the bony spinal canal. The 3D-CT scans clearly demonstrate the configuration of the OYL (arrow), especially where it extends into the intervertebral foramen (*), which area was removed by partial laminectomy confined to this level.
4
OYL at T3–T4 (Figure 4), and OPLL at C2–C5 with maximum involvement at C4. After the first surgery, consisting of C1–C7 osteoplastic laminotomy, the patient’s left grasping power improved. The removal of the OYL at the T3–T4 level 3 weeks later resulted in improvement of the dysesthesia and weakness of the left leg.
Discussion It is reported that in Japan, OYL is asymptomatic in 25% of the cases detected on plain radiograms or tomograms [6]. However, by the time gait disturbance appears, the OYL is sometimes already very extensive. In our experience, the neurologic findings on admission revealing weakness of the lower extremities lead to detection in about 50% of the cases, in contrast to the initial symptoms in only 16% [5]. The most symptomatic OYL is thought to occur at the lower thoracic levels, mainly T10 –T11 or T11–T12 [6]. Our data corroborate this generalization, but we also note that OYL occurs not only in the lower thoracic region, but also in the high (19%) and middle (14%) thoracic regions. Thus, a survey of the entire thoracic region is necessary when symptomatic OYL is suspected. When plain radiograms or tomograms in the lateral projection are carefully examined, OYL can be confirmed to reside mainly in the foramen, where it assumes a bird-bill shape. CT scans obtained at fine-slice thickness demonstrate very precisely
whether OYL is present [1,2,4,10]. The degree of spinal compression can also be evaluated by using CT performed after myelography. MR imaging is very reliable in detecting OYL, itself, in the sagittal projection when the OYL is large [9]. However, it often fails to detect OYL when it extends mainly into the foramen. Formerly, reconstructed CT was more reliable but, more recently, 3D-CT has been found to be most useful in planning the surgical approach. It clearly reveals whether the OYL extends from the medial side to the lateral foramen segmentally, without fusing of adjacent portions affected by OYL. This is the main reason that we recommend limited operation. At operation, it is important to correctly identify the level of OYL involvement. As shown in Figure 5, the initial foraminotomy [8] should be made at the medial region of the upper lamina. After the foraminotomy is made, the medial border of the superior facet is first identified and that region is cut as thin as possible. Then, the OYL itself is detected and cut in tapered fashion. The hard material of the OYL is removed easily with a curette. Previously, wide laminectomy extending across 3– 4 levels was usually performed [3,7]. The application of 3D-CT makes it possible to determine the precise location of the OYL. As a result, the operative space has become a very small area. In addition, OYL is easily removed by thinning of the OYL itself away from the adjacent lamina or facet joint as it is not as hard as the OPLL. In laterally extended OYL, ischemic change of the spinal cord due to
372 Surg Neurol 1999;51:368 –72
Nishiura et al
Conclusion The surgical treatment of OYL in the early stage is recommended, because OYL is usually already quite large at the time of detection in patients with motor weakness. Symptomatic OYL can occur not only in the lower thoracic region but also in the upper and middle thoracic regions. Finally, initial foraminotomy and thinning of the OYL itself are safely and accurately performed with the aid of 3D-CT imaging.
REFERENCES The scheme at operation shows the relationship between the pedicle and the position of foraminotomy (reproduced, by permission, from Ref. 5). (Left, vertical; right, axial.) A, Slice level at the intervertebral foramen; B, slice level at the superior articular processus. shaded area, position of foraminotomy: dotted area, position of the OYL.
5
compression of the radicular artery by the OYL may sometimes occur. In such a case, adequate decompression of the radicular artery is necessary. Thus, when laminectomy is carried out after the initial foraminotomy, OYL extending into the foramen laterally can be removed under direct vision from the contralateral side. In cases with ossification of the dura mater, although rarely found, the OYL can also be removed by lifting it with a curette and detaching it carefully from the adjacent arachnoid [7]. Sometimes, the motor weakness and dysesthesia of the legs do not improve promptly in patients with late-stage OYL. The likelihood of improvement seems to depend on the delay between the initial symptoms and the operation. Thus, we try whenever possible to perform surgical decompression early. When two-thirds or more of the posterior facet surfaces are injured, i.e., by addition of extreme lateral foraminal decompression, lateral fusion with or without instrumentation should also be applied.
1. Leroux JL, Legeron P, Moulinier L, Laroche M, Mazieres B, Blotman F, Arlet J. Stenosis of the lumbar spinal canal in vertebral ankylosing hyperostosis. Spine 1992;17:1213– 8. 2. Kurihara A, Tanaka Y, Tsumura N, Iwasaki Y. Hyperostotic lumbar spinal stenosis. A review of 12 surgically treated cases with roentgenographic survey of ossification of the yellow ligament at the lumbar spine. Spine 1988;13:1308 – 6. 3. Matsuzaki H, Tokuhashi T, Wakabayashi K, Matsumoto F. The pathogenesis and surgical procedure for OYL. Seikei Geka 1993;44:1272– 8. 4. Miyasaka K, Kaneda K, Ito T, Tabei H, Sugimoto S, Tsuru M. Ossification of spinal ligaments causing thoracic radiculomyelopathy. Radiology 1982;143:463– 8. 5. Nishiura I, Koyama T. Clinical aspects and operative approach for the ossification of thoracic yellow ligament. Spine Spinal Cord (Japanese) 1990;3:483–9. 6. Saiki K, Hattori A, Kawai S, Miyamoto T, Tsue K, Kotani H. The ossification of the yellow ligament in the thoracic spine. Seikei, Saigai Geka 1981;24:191– 8. 7. Sato T, Kokubun M, Ishii Y. Choice of operative method for ossification of ligamentum flavum based on CT findings. Rinsho Seikeigeka 1996;31:541–5. 8. Scoville WB. Posterior approaches to cervical discs. In: Symon L, ed. Operative surgery: neurosurgery Ed. 3. London: Butterworths, 1979:438 – 46. 9. Yamashita Y, Takahashi M, Matsuno Y, Sakamoto Y, Yoshizumi K, Oguni T, Kojima R. Spinal cord compression due to ossification of ligaments: MR imaging. Radiology 1990;175:843– 8. 10. Yanagi T, Naitou A, Yasuda T, Hashizume Y, Oomori K. The ossification of the ligamentum flavum of the thoracic spine; correlative CT and pathologic study. Seikei Geka 1987;38:297–307.
Nishiura I, Isozumi T, Nishihara K, Handa H, Koyama T. Surgical approach to ossification of the thoracic yellow ligament. Surg Neurol 1999;51:368 –72. BACKGROUND
Symptomatic ossification of the yellow ligament (OYL) at the lower thoracic level is uncommon. Although wide laminectomy has, until now, been the primary treatment for this disease, we propose a less invasive technique based on a new method of three-dimensional computed tomography (CT). METHODS
The clinical features and radiologic imaging findings of 37 patients with OYL (mean age, 54 years) were analyzed. The surgical approach was selected based on the position of the depicted OYL on 3D CT scan in each patient. RESULTS
The male-to-female ratio was 3:1. Involvement of the upper thoracic region was seen 11 times; of the middle region 8 times, and of the lower region 40 times (several patients had involvement in more than one region). About half of the patients complained of gait disturbance on admission caused by the markedly enlarged OYL. No postoperative complications were found. Neurologic deterioration was observed in only one patient. CONCLUSIONS
OYL should be treated as early as possible, using the least invasive technique available. By using 3D CT, we were able to perform limited surgery consisting of foraminotomy or extended partial laminectomy at the affected level after confirming the anatomic location of the OYL. In laterally extended OYL, it is necessary to decompress the radicular artery in order to prevent ischemic damage to the spinal cord. © 1999 by Elsevier Science Inc. KEY WORDS
Ossification, posterior longitudinal ligament, threedimensional computed tomography, yellow ligament.
Address reprint requests to: Dr. Iwao Nishiura, Division of Neurosurgery, Takeda General Hospital, 28-1 Mori-minami-cho, Ishida, Fushimi-ku, Kyoto, 601-13, Japan. Received July 25, 1997; accepted December 17, 1997. 0090-3019/99/$–see front matter PII S0090-3019(98)00051-2
ssification of the yellow ligament (OYL) at the level of the lower thoracic cord is often asymptomatic or only incidentally detected. When it produces symptoms, however, it frequently takes the form of markedly extensive ossification with extreme compression of the spinal cord. Recent advances in magnetic resonance (MR) imaging have made it easier to diagnose OYL in the early stages. The anatomical relationships among the ossified material and the spinal cord, lamina, and facet joint are now more accurately depicted by reconstructive computed tomography (CT). Thus, at the present time, the ossified material can be removed more easily, and with greater confidence and less invasiveness. We encountered 37 patients with symptomatic OYL in the past 15 years. We performed wide laminectomy during the early period, but more recently we have performed a key-hole foraminotomy (thinning of the lamina and OYL) with or without an additional small laminectomy. This improvement in technique was aided by a new 3D-CT imaging modality. Focusing on this modality, we discuss the problematic aspects of OYL.
O
Methods and Material We encountered 37 patients (mean age, 54 years; male-to-female ratio, 3:1) with symptomatic OYL between 1981 and 1996. All patients underwent operation, and, in all of them, the diagnosis of OYL was histologically confirmed. The preoperative radiologic examinations included myelography and CT myelography, and in the more recently treated patients, CT reconstruction, MR imaging, and 3D-CT imaging were also performed. © 1999 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
Ossification of Thoracic Yellow Ligament
Surg Neurol 369 1999;51:368 –72
A, Preoperative (1) and postoperative (2) CT scans; B, preoperative (1) and postoperative (2) 3D-CT scans. A small area of the OYL (arrows) was removed by bilateral foraminotomy.
1
Results The level of involvement was in the upper thoracic region in 11 patients, the middle region in 8, and the lower region in 40 patients. The OYL was accompanied by lumbar canal stenosis in 4 patients, and by ossification of the posterior longitudinal ligament (OPLL) or other cervical lesions in 8 patients. Neurologic examinations revealed sensory disturbance (58%), motor weakness of the lower extremities (50%), gait disturbance (75%), and bladder dysfunction (17%). In all patients, the OYL was detected by CT myelography, which showed dural deformity (30%), cord deformity (50%), or only dural contact with the OYL (20%). In most patients, the OYL was of the symmetrical or unilaterally localized type, but three patients showed the rare medial type of OYL [10]. No postoperative complications were found. Neurologic deterioration was observed in only one patient.
Case Reports Four representative cases are presented. CASE 1 A 53-year-old man had noticed dysesthesia of his legs and dysuria for about 2 years. He gradually developed gait disturbance during the year immediately preceding his admission. Neurologic examination on admission revealed hypesthesia, hypalgesia below the T12 level, normal strength of his extremities, exaggeration of
both knee and ankle reflexes, positive bilateral Babinski sign, spastic gait, and neurogenic bladder. Myelography revealed poor filling of the contrast medium from T10 to T12. CT myelography disclosed bilateral OYL with mild cord compression at the level of T10 –T11 (Figure 1A1). MR imaging also revealed spinal cord compression due to the OYL only at this level. Bilateral foraminotomy at T10 –T11 was performed. After the dura was exposed near the midline, a part of the OYL was detected under the medial region of the upper third of the superior facet. The OYL was thinned, using an air drill, and easily removed. By 2 weeks after the operation, the bladder dysfunction had resolved and the spastic gait improved. Postoperative CT scanning disclosed that the OYL had been totally removed (Figure 1A2). CASE 2 A 70-year-old man complained of dysesthesia and weakness of the left hand that had begun 1 month previously and had gradually spread to both lower extremities. Neurologic examination on admission revealed weakness of bilateral upper and lower extremities, hypesthesia and hypalgesia of the palmar region, and hyperreflexia of the patellar tendon reflex and Achilles tendon reflex. The myelogram and CT scan disclosed compression of the spinal cord at two widely separated levels: cervical disc hernia at C4 –C5 and thoracic disc (T10 –T11) hernia from the ventral side with
370 Surg Neurol 1999;51:368 –72
Nishiura et al
A, Preoperative CT scan; B, preoperative CT myelogram; and C, postoperative CT scan. A small area of the OYL was removed by partial laminectomy following bilateral foraminotomy (arrow, a herniated thoracic disc)
2
accompanying OYL on the dorsal side (Figure 2 A and B). Three weeks after operation for the herniated cervical disc, the ossified portion of the yellow ligament was removed, followed by bilateral foraminotomy at T10 –T11 (Figure 2C). The thoracic disc was left untouched because the main causes of the patient’s symptoms were thought to be the cervical disc herniation and the OYL at T10 –T11. Starting 1 week after the first operation, the spastic gait improved rapidly, and 3 weeks after the second operation, the dysesthesia began to subside gradually. CASE 3 A 56-year-old woman complained of a 2-year history of lumbago with subsequent development of pain in the right lower extremity. She also had a 1-year history of weakness of this extremity, followed by spastic limping gait. Neurologic examination on admission revealed motor weakness of the right leg, hyperreflexia, and bilateral clonus. No sensory disturbance was found.
A, Plain CT; B, CT myelogram; and C, 3D-CT scan. OYL (arrows) at two levels is clearly demonstrated on 3D-CT.
3
CT myelography revealed OYL at T9 –T10 and T10 –T11 (Figure 3). MR imaging disclosed no intramedullary lesion. Hyperreflexia, probably caused partly by compression of the radicular artery by the OYL at the intervertebral foramen, was noted. After partial laminectomy following foraminotomy was performed, the laterally extended OYL was seen from the contralateral side. Adequate decompression of the radicular artery was obtained. Her leg pain disappeared promptly after the operation. However, the weakness of the lower extremity did not improve. CASE 4 A 71-year-old man had fallen down while inebriated. Immediately after the accident, he could not move his extremities, but his condition then improved gradually to the level of the left hemiparesis in 3 days. Neurologic examination on admission revealed left hemiparesis, hypesthesia and hypalgesia below the C4 level, and exaggerated reflexes of the lower extremities. Plain X-ray and MR images revealed
Ossification of Thoracic Yellow Ligament
Surg Neurol 371 1999;51:368 –72
A, MR image; B, preoperative (1) and postoperative (2) 3D-CT scans showing an inside view of the bony spinal canal. The 3D-CT scans clearly demonstrate the configuration of the OYL (arrow), especially where it extends into the intervertebral foramen (*), which area was removed by partial laminectomy confined to this level.
4
OYL at T3–T4 (Figure 4), and OPLL at C2–C5 with maximum involvement at C4. After the first surgery, consisting of C1–C7 osteoplastic laminotomy, the patient’s left grasping power improved. The removal of the OYL at the T3–T4 level 3 weeks later resulted in improvement of the dysesthesia and weakness of the left leg.
Discussion It is reported that in Japan, OYL is asymptomatic in 25% of the cases detected on plain radiograms or tomograms [6]. However, by the time gait disturbance appears, the OYL is sometimes already very extensive. In our experience, the neurologic findings on admission revealing weakness of the lower extremities lead to detection in about 50% of the cases, in contrast to the initial symptoms in only 16% [5]. The most symptomatic OYL is thought to occur at the lower thoracic levels, mainly T10 –T11 or T11–T12 [6]. Our data corroborate this generalization, but we also note that OYL occurs not only in the lower thoracic region, but also in the high (19%) and middle (14%) thoracic regions. Thus, a survey of the entire thoracic region is necessary when symptomatic OYL is suspected. When plain radiograms or tomograms in the lateral projection are carefully examined, OYL can be confirmed to reside mainly in the foramen, where it assumes a bird-bill shape. CT scans obtained at fine-slice thickness demonstrate very precisely
whether OYL is present [1,2,4,10]. The degree of spinal compression can also be evaluated by using CT performed after myelography. MR imaging is very reliable in detecting OYL, itself, in the sagittal projection when the OYL is large [9]. However, it often fails to detect OYL when it extends mainly into the foramen. Formerly, reconstructed CT was more reliable but, more recently, 3D-CT has been found to be most useful in planning the surgical approach. It clearly reveals whether the OYL extends from the medial side to the lateral foramen segmentally, without fusing of adjacent portions affected by OYL. This is the main reason that we recommend limited operation. At operation, it is important to correctly identify the level of OYL involvement. As shown in Figure 5, the initial foraminotomy [8] should be made at the medial region of the upper lamina. After the foraminotomy is made, the medial border of the superior facet is first identified and that region is cut as thin as possible. Then, the OYL itself is detected and cut in tapered fashion. The hard material of the OYL is removed easily with a curette. Previously, wide laminectomy extending across 3– 4 levels was usually performed [3,7]. The application of 3D-CT makes it possible to determine the precise location of the OYL. As a result, the operative space has become a very small area. In addition, OYL is easily removed by thinning of the OYL itself away from the adjacent lamina or facet joint as it is not as hard as the OPLL. In laterally extended OYL, ischemic change of the spinal cord due to
372 Surg Neurol 1999;51:368 –72
Nishiura et al
Conclusion The surgical treatment of OYL in the early stage is recommended, because OYL is usually already quite large at the time of detection in patients with motor weakness. Symptomatic OYL can occur not only in the lower thoracic region but also in the upper and middle thoracic regions. Finally, initial foraminotomy and thinning of the OYL itself are safely and accurately performed with the aid of 3D-CT imaging.
REFERENCES The scheme at operation shows the relationship between the pedicle and the position of foraminotomy (reproduced, by permission, from Ref. 5). (Left, vertical; right, axial.) A, Slice level at the intervertebral foramen; B, slice level at the superior articular processus. shaded area, position of foraminotomy: dotted area, position of the OYL.
5
compression of the radicular artery by the OYL may sometimes occur. In such a case, adequate decompression of the radicular artery is necessary. Thus, when laminectomy is carried out after the initial foraminotomy, OYL extending into the foramen laterally can be removed under direct vision from the contralateral side. In cases with ossification of the dura mater, although rarely found, the OYL can also be removed by lifting it with a curette and detaching it carefully from the adjacent arachnoid [7]. Sometimes, the motor weakness and dysesthesia of the legs do not improve promptly in patients with late-stage OYL. The likelihood of improvement seems to depend on the delay between the initial symptoms and the operation. Thus, we try whenever possible to perform surgical decompression early. When two-thirds or more of the posterior facet surfaces are injured, i.e., by addition of extreme lateral foraminal decompression, lateral fusion with or without instrumentation should also be applied.
1. Leroux JL, Legeron P, Moulinier L, Laroche M, Mazieres B, Blotman F, Arlet J. Stenosis of the lumbar spinal canal in vertebral ankylosing hyperostosis. Spine 1992;17:1213– 8. 2. Kurihara A, Tanaka Y, Tsumura N, Iwasaki Y. Hyperostotic lumbar spinal stenosis. A review of 12 surgically treated cases with roentgenographic survey of ossification of the yellow ligament at the lumbar spine. Spine 1988;13:1308 – 6. 3. Matsuzaki H, Tokuhashi T, Wakabayashi K, Matsumoto F. The pathogenesis and surgical procedure for OYL. Seikei Geka 1993;44:1272– 8. 4. Miyasaka K, Kaneda K, Ito T, Tabei H, Sugimoto S, Tsuru M. Ossification of spinal ligaments causing thoracic radiculomyelopathy. Radiology 1982;143:463– 8. 5. Nishiura I, Koyama T. Clinical aspects and operative approach for the ossification of thoracic yellow ligament. Spine Spinal Cord (Japanese) 1990;3:483–9. 6. Saiki K, Hattori A, Kawai S, Miyamoto T, Tsue K, Kotani H. The ossification of the yellow ligament in the thoracic spine. Seikei, Saigai Geka 1981;24:191– 8. 7. Sato T, Kokubun M, Ishii Y. Choice of operative method for ossification of ligamentum flavum based on CT findings. Rinsho Seikeigeka 1996;31:541–5. 8. Scoville WB. Posterior approaches to cervical discs. In: Symon L, ed. Operative surgery: neurosurgery Ed. 3. London: Butterworths, 1979:438 – 46. 9. Yamashita Y, Takahashi M, Matsuno Y, Sakamoto Y, Yoshizumi K, Oguni T, Kojima R. Spinal cord compression due to ossification of ligaments: MR imaging. Radiology 1990;175:843– 8. 10. Yanagi T, Naitou A, Yasuda T, Hashizume Y, Oomori K. The ossification of the ligamentum flavum of the thoracic spine; correlative CT and pathologic study. Seikei Geka 1987;38:297–307.