Ossification of the posterior longitudinal ligament (OPLL) in the cervical spine as a diagnosis leading to myelopathy and serious impairment has been studied extensively. Inconsistencies in the findings of different investigators and disparities in prevalence in the community, especially in Japan, has led to the formation of the Investigation Committee on Ossification of the Spinal Ligaments and the Investigation Committee on OPLL organized by the Japanese Ministry of Public Health and Welfare. Recent investigations of long-term outcomes associated with various treatment methods have yielded insight into the natural history, prognostic factors, and optimal preoperative evaluations, and provide best evidence–based information for surgical decision making. This chapter presents the case of a myelopathic patient with OPLL and discusses techniques of the primary treatment methods. Recent literature provides the best evidence regarding treatment and prognosis for counseling patients with OPLL.
Case Presentation
A 58-year-old man had a chief complaint of mild neck pain and bilateral hand paresthesias. His upper extremity paresthesias had become worse over the previous 6 months and no longer responded to nonsteroidal antiinflammatory drugs. The paresthesias were constant and did not change with alteration of arm or head position. He reported no gait abnormalities or bowel or bladder dysfunction. When questioned, he commented that he frequently drops objects and said that he wears pullover shirts due to difficulty with buttons.
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PMH: Hypertension and diabetes mellitus
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PSH: Unremarkable
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Exam: The patient showed good range of motion of the cervical spine without exacerbation of his neck pain or upper extremity symptoms. His upper extremity examination reveals 5/5 strength with diminished sensation to light touch from C6 to C8 dermatomes bilaterally. His biceps and brachioradialis reflexes were 4/5 bilaterally, and when the brachioradialis reflex was tested his thumb, index, and long fingers flexed (inverted radial reflex). His attempts to rapidly open and close his fists revealed significant spasticity (dysdiadochokinesia). The Hoffman sign was positive bilaterally. Lower extremity examination revealed normal gait stride and cadence with 5/5 strength and sensation intact to light touch from L2 to S1 myotomes and dermatomes, respectively. Patellar and Achilles reflexes were 4/5 bilaterally. There was no spasticity with range of motion of the knees, but six beats of clonus bilaterally. His toes were down turning on testing of the plantar reflex.
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Imaging: Sagittal computed tomographic (CT) scans ( Figure 3-1 ) demonstrated mixed-type OPLL from C3 to C7 with increased ossification posterior to C5-6, and lordotic alignment. Axial CT images ( Figure 3-2 ) demonstrated OPLL and diminished canal dimension. Sagittal and axial magnetic resonance (MRI) images ( Figure 3-3 ) show spinal cord compression by the ossified lesions.
FIGURE 3-1
Preoperative sagittal CT scans demonstrating mixed-type OPLL from C3 to C7 with an increase posterior to C5-6.
FIGURE 3-2
Axial CT scans demonstrating OPLL intrusion into the spinal canal.
FIGURE 3-3
Sagittal and axial MRI images of OPLL effacing cerebrospinal fluid signal and compressing the spinal cord.
Surgical Options
Surgical options for the treatment of OPLL depend on the site of compression, the number of levels involved, nuchal sagittal balance, the potential for the cord to drift posteriorly, the presence or absence of congenital stenosis, and the morphologic type of the OPLL. Anterior surgical options include multilevel anterior cervical diskectomy and fusion (ACDF) or multilevel anterior cervical corpectomy and fusion (ACCF). Posterior options include laminectomy with or without fusion or laminoplasty. In certain cases circumferential treatment is necessary that combines anterior decompression and fusion with supplemental posterior instrumented fusion.
The 58-year-old patient with mixed-type OPLL from C3 to C7 and a lordotic cervical spine was determined to be a good candidate for a C3-C7 laminectomy and fusion. Postoperative anteroposterior (AP) and lateral radiographs ( Figure 3-9 ) demonstrated slight loss of lordosis with maintenance of decompression. Clinically the patient’s myelopathic symptoms improved along with his radicular hand symptoms.
Postoperative course: The patient was admitted to the hospital after surgery for pain control and physical and occupational therapy. Findings of the immediately postoperative physical examination were stable relative to those of the preoperative examination, and after a 3-day uneventful hospital course he was discharged home. Maintenance of strength and resolution of upper extremity sensory deficits as well as clonus was demonstrated at 6- and 12-month follow-up. The patient has had no progression of OPLL. He maintains an independent lifestyle and performs activities of daily living himself. He is a community ambulator.
Fundamental Technique
Multilevel Cervical Diskectomies and/or Corpectomies
The Smith-Robinson approach is the principal surgical approach for the performance of anterior cervical fusions. A left-sided exposure is used primarily because the course of the recurrent laryngeal nerve is more predictable and protected in the left tracheoesophageal groove. The presence of a kyphotic deformity necessitates consideration of preoperative and/or intraoperative cervical traction. Preoperatively, cervical range of motion must be assessed by the anesthesia and surgical teams. Hyperextension of the cervical spine should be avoided during intubation and patient positioning. In patients with myelopathy, awake fiberoptic intubation and neurophysiologic monitoring of transcranial motor evoked potentials (tcMEPs) and somatosensory evoked potentials (SSEPs) should be considered. OPLL beyond the margins of the disk space causing retrovertebral compression warrants either a partial or complete corpectomy.
The level of the skin incision can be assessed using the palpable subcutaneous landmarks corresponding to the adjacent vertebral bodies ( Figure 3-4 ). The hyoid corresponds to C3, the thyroid cartilage to C4-C5, and the cricoid to C6. In addition, the carotid tubercle of C6 can often be palpated. An oblique incision paralleling the anterior margin of the sternocleidomastoid is often utilized for multilevel procedures because it grants access to more levels than does the more cosmetically appealing transverse incision that corresponds to Langer lines. Sharp dissection is performed down to the platysma, and it is divided transversely. Flaps are raised proximally and distally deep to the platysma. The sternocleidomastoid is identified. Dissection is performed bluntly, anterior and medial to the anterior edge of the sternocleidomastoid, through the deep cervical fascia where the omohyoid is encountered. Care must be taken to keep the carotid sheath and its contents lateral to the plane of dissection ( Tips from the Masters 3-1 ). The middle layer of the deep cervical fascia between the omohyoid and the sternocleidomastoid is bluntly dissected. The omohyoid may be divided if necessary to extend the exposure over multiple levels. The deep layer of the deep cervical fascia is incised vertically over the midline of the vertebral bodies and disks. Radiographic documentation of the appropriate diskectomy or corpectomy level is obtained by placing a spinal needle or marker within either a disk or vertebral body. The longus colli is elevated for 3 to 4 mm off the adjacent disk spaces and vertebral bodies.
The carotid sheath and its contents should be kept lateral to the plane of dissection, which is toward the anterior cervical spine.
The disk material is extricated and the uncinate processes are identified to delineate the lateral limits of the decompression or corpectomy. The decompression includes removal of the posterior disk-osteophyte complexes, identification and removal, or “floating,” of the ossified PLL, and foraminal decompression via removal of uncovertebral osteophytes.
If the surgical plan involves a corpectomy, the disks cephalad and caudad to the planned vertebrectomy level, along with any intervening disk in the case of a multilevel procedure, are completely excised before the vertebrectomy is performed. The decompression should be extended so as to completely alleviate elements leading to spinal cord deformation and compression.
When OPLL is the source of compression, caution must be exercised in removal of the ossification, and corpectomies are often necessary ( Tips from the Masters 3-2 ). The presence of the double layer sign (a rim of ossification surrounding the hypodense ligament) on radiographic workup of OPLL is suggestive of dural penetration. The two layers represent ossification of the ventral PLL and ossification that invests the dura with an intervening space of less dense PLL. This increases the risk of neurologic injury and iatrogenic durotomy if complete débridement of the OPLL is performed. An alternative to complete resection of the OPLL is the anterior floating method, which involves a transverse decompression of 20 to 25 mm to the joints of Luschka and release of the OPLL around the region that invests or replaces the dura to allow sufficient 4 to 5 mm of anterior migration of the ossification. In the event of a dural defect, a primary repair should be attempted, and adjuncts such as dural grafts and fibrin glue sealant can be applied to prevent cerebrospinal fluid (CSF) leaks. The patient can be kept in an upright position to diminish the buildup of CSF pressure across the anterior cervical spinal cord. Persistent leaks have been successfully treated with lumboperitoneal shunts and lumbar drains to prevent CSF fistulas.
Electrocautery exposure of anterior osteophytes facilitates complete removal, which improves visualization of the posterior vertebral body and allows for anatomic placement of anterior plates.
Orientation to the midline must be maintained during the decompression. As demonstrated by An and colleagues , the risk of vertebral artery injury increases as one moves rostrally in the subaxial cervical spine. At C3 a 15-mm-wide central decompression, and at C6 a 19-mm-wide decompression, yields a 5-mm margin of safety for the transverse foramen and vertebral artery ( Figure 3-5 ). Goto and associates reported in 1993 that the central decompression should be at least 16 mm. This can be achieved by maintaining C3 15-mm and C6 19-mm-wide central decompressions at the level of the vertebral artery and expanding the decompression dorsally as the canal is approached. After the decompression is completed, the focus shifts to reconstruction and grafting of the corpectomy defect. Fibular strut allografts and cages filled with local autograft are principally used to reconstruct the corpectomy defects. Before anterior cervical instrumentation became standard, postoperative graft dislodgment was a significant risk. Several authors have recommended that the treatment of OPLL involving one- or two-level corpectomies consist of allograft strut grafting and anterior plating. Multilevel OPLL involving three or more levels should be addressed with multilevel corpectomies, allograft strut grafting, anterior plating, and supplemental posterior fixation and fusion. This approach has been associated with few, if any, graft-related complications.
Laminectomy with or without Fusion
Posterior surgical approaches to treat myelopathy due to OPLL include laminectomy with or without fusion and laminoplasty ( Tips from the Masters 3-3 ). The patient can be placed prone in a Mayfield pin headrest or in a halo ring vest to maintain alignment and avoid pressure on the central retinal artery. Reverse Trendelenburg positioning helps reduce bleeding and improve visualization for the surgeon. Neurophysiologic monitoring (measurement of SSEPs and tcMEPs, electromyography) is generally recommended.
Preoperative administration of steroids can help mitigate neurologic injury.
Landmarks for the posterior midline dissection include the palpable spinous processes of C2 and C7. Bilateral subperiosteal dissection of the posterior elements is carried out to the facets of the levels involved. Complete exposure and packing of the most cephalad levels initially, followed by sequential exposure and packing of the caudal levels in addition, improves visualization and reduces bleeding. Careful dissection should avoid removal of the C2 attachments of the erector spinae and suboccipital triangle muscles, because they contribute to stability and resist kyphosis at this level.
After adequate exposure of the involved levels is obtained, a high-speed bur is used to create a trough at the facet-lamina junction bilaterally ( Figure 3-6 , A ). A Kerrison rongeur is used to release the ligamentum flavum and complete the troughs. The lamina is then removed en bloc ( Figure 3-6 , B ). After completion of the laminectomy ( Figure 3-6 , C ), foraminotomies can be performed as indicated. Decompression of the exiting nerve roots is assessed with a small nerve hook or probe.
Laminectomy is often carried out from C3 to C7 to ensure that decompression is sufficient to prevent dorsal kinking of the spinal cord and resultant neurologic deficit ( Tips from the Masters 3-4 ). In addition, removal of the T1 lamina can destabilize the cervicothoracic junction and result in postoperative deformity.
Avoid complete facetectomy to prevent iatrogenic destabilization and assess foraminal decompression with a right-angled nerve probe.
Instrumented fusion, using lateral mass screws in the subaxial cervical spine, generally accompanies laminectomy. Starting points for the screws should be 1 mm medial to the coronal and sagittal midpoints ( Figure 3-7 , A ). A 2-mm bur is used to initiate the starting points, which should be in line with each other. A 2.5-mm drill with a 12- to 14-mm stop is used to drill the holes to orient the screws 30 degrees laterally and 15 to 30 degrees cephalad ( Figure 3-7 , B and C ). Following drilling, the holes should be probed, measured, tapped, and probed again ( Tips from the Masters 3-5 ). After the lateral mass screws are placed, a longitudinal rod is measured, cut, contoured, and definitively fixed to the rod-screw construct. The lateral masses are then decorticated, graft material is placed laterally to the rod-screw construct, and the incision is closed in layers over a drain.
If a unilateral violation of the vertebral artery occurs during drilling or tapping of lateral mass screw holes, pack the hole with bone wax and place the screw for hemostasis, and do not instrument the contralateral side.
Laminoplasty
Laminoplasty is an alternative to laminectomy. After a dissection and exposure similar to that for laminectomy are performed, a bur is used to make a full-thickness trough on the opening side at the lamina-facet junction. Then a partial-thickness gutter is made on the hinge side to prevent the hinge from becoming unstable or disjointed ( Figure 3-8 , A and B ). A small or micro Kerrison rongeur is used to complete the trough on the opening side. The opening side should be the more symptomatic side demonstrating radicular symptoms so that foraminotomies may be performed. The ligamentum flavum at the rostral and caudal ends of the laminar door is removed transversely. While the gutter on the hinge side is deepened, the surgeon should gradually apply an opening force to the spinous processes ( Tips from the Masters 3-6 ). When the laminoplasty door is ready to be opened, stay sutures from the intact facet capsules around the bases of the spinous processes ( Figure 3-8 , C and D ), allograft bone, or specially designed plates can be used to keep the door open as the free edge is elevated.
If hinge fracture occurs, a complete laminectomy should be performed.
Fundamental Technique
Multilevel Cervical Diskectomies and/or Corpectomies
The Smith-Robinson approach is the principal surgical approach for the performance of anterior cervical fusions. A left-sided exposure is used primarily because the course of the recurrent laryngeal nerve is more predictable and protected in the left tracheoesophageal groove. The presence of a kyphotic deformity necessitates consideration of preoperative and/or intraoperative cervical traction. Preoperatively, cervical range of motion must be assessed by the anesthesia and surgical teams. Hyperextension of the cervical spine should be avoided during intubation and patient positioning. In patients with myelopathy, awake fiberoptic intubation and neurophysiologic monitoring of transcranial motor evoked potentials (tcMEPs) and somatosensory evoked potentials (SSEPs) should be considered. OPLL beyond the margins of the disk space causing retrovertebral compression warrants either a partial or complete corpectomy.
The level of the skin incision can be assessed using the palpable subcutaneous landmarks corresponding to the adjacent vertebral bodies ( Figure 3-4 ). The hyoid corresponds to C3, the thyroid cartilage to C4-C5, and the cricoid to C6. In addition, the carotid tubercle of C6 can often be palpated. An oblique incision paralleling the anterior margin of the sternocleidomastoid is often utilized for multilevel procedures because it grants access to more levels than does the more cosmetically appealing transverse incision that corresponds to Langer lines. Sharp dissection is performed down to the platysma, and it is divided transversely. Flaps are raised proximally and distally deep to the platysma. The sternocleidomastoid is identified. Dissection is performed bluntly, anterior and medial to the anterior edge of the sternocleidomastoid, through the deep cervical fascia where the omohyoid is encountered. Care must be taken to keep the carotid sheath and its contents lateral to the plane of dissection ( Tips from the Masters 3-1 ). The middle layer of the deep cervical fascia between the omohyoid and the sternocleidomastoid is bluntly dissected. The omohyoid may be divided if necessary to extend the exposure over multiple levels. The deep layer of the deep cervical fascia is incised vertically over the midline of the vertebral bodies and disks. Radiographic documentation of the appropriate diskectomy or corpectomy level is obtained by placing a spinal needle or marker within either a disk or vertebral body. The longus colli is elevated for 3 to 4 mm off the adjacent disk spaces and vertebral bodies.
Related posts:
Asymptomatic Intradural Schwannoma: Surgery Versus Radiosurgery Versus Observation
Cervical Spondylosis–Spinal Stenosis: Laminoplasty Versus Laminectomy and Fusion
Lumbar Degenerative Disk Disease: Fusion Versus Artificial Disk
Degenerative Scoliosis: Anterior and Posterior Fusion Versus Posterior Fusion
Laminectomy Across the Cervicothoracic Junction: Fusion Versus Nonfusion
C1-C2 Fusion: Transarticular Screws Versus Harms/Melcher Procedure
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