- Email: [email protected]
Intraoperative Ultrasound-Guided Posterior Cervical Laminectomy for Degenerative Cervical Myelopathy
Technical Note
Intraoperative Ultrasound-Guided Posterior Cervical Laminectomy for Degenerative Cervical Myelopathy Ralph T. Scha¨r, Jefferson R. Wilson, Howard J. Ginsberg
OBJECTIVE: We present our experience with routine intraoperative ultrasound (IOUS)eguided posterior cervical laminectomy (PCL) in patients with degenerative cervical myelopathy (DCM), describe the technique used, and describe relevant IOUS findings that may impact the surgical procedure.
-
METHODS: Three illustrative cases are presented of patients (age range, 67e79 years) who underwent PCL with IOUS guidance and instrumented fusion for DCM. Intraoperative standard B-mode images were obtained with a linear array 6.6- to 13.3-MHz transducer.
-
RESULTS: Excellent high-resolution IOUS view of the spinal cord and nerve roots was obtained in every case after laminectomy. IOUS had a relevant intraoperative impact in all cases, leading to extended decompression of focal residual compression, confirmation of posterior shift of the spinal cord from anteriorly located structures, and final confirmation of sufficient decompression by visualization of symmetric and rhythmic cord pulsations.
-
CONCLUSIONS: IOUS is a poorly described yet easy-touse and very effective tool for guidance and confirmation of adequate posterior decompression of the cervical spinal cord and nerve roots during PCL. Routinely using IOUSguided decompression for PCL in patients with myelopathy will help avoid residual compression of neural elements and might be beneficial for functional outcome.
-
P
osterior cervical laminectomy (PCL) is a frequent operative procedure in spine surgery to decompress the spinal cord and nerve roots in patients with degenerative cervical
Key words Cervical fusion - Cervical laminectomy - Degenerative cervical myelopathy - Intraoperative ultrasound -
Abbreviations and Acronyms DCM: Degenerative cervical myelopathy IOUS: Intraoperative ultrasound OPLL: Ossification of the posterior longitudinal ligament PCL: Posterior cervical laminectomy
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myelopathy (DCM), deformity, traumatic spinal cord injury, and spinal tumors.1 Frequently, PCL is combined with an instrumented fusion, mainly to avoid secondary instability and postlaminectomy kyphosis. Outcome after PCL is generally good, and rates of neurologic improvement of 40%e95% have been reported depending on origin of pathology and duration of symptoms.2-4 However, after PCL, the extent of decompression may easily be misjudged because the surgeon can merely assess the appearance of the dura after bone removal, but has no direct visualization of the spinal cord and nerve roots or anteriorly located structures. Incomplete decompression of the spinal cord and nerve roots may lead to postoperative radiculopathy, persistent symptoms, poor neurologic recovery, or functional deterioration in patients with myelopathy. In recent years, the use of intraoperative ultrasound (IOUS) has become popular in both cranial neurosurgery and spine surgery and remains the only true real-time imaging modality allowing surgeons to instantly visualize soft tissue anatomy while operating.5 Although IOUS was introduced to spine surgery over 30 years ago, there is no description in the literature of ultrasound as an adjunctive intraoperative tool for PCL. The quality and clarity of the images have improved remarkably over this time period. We use IOUS for guidance of PCL on a routine basis to achieve and confirm adequate decompression of the neural elements. We herewith present our experience with IOUS-guided PCL, discuss technical aspects, and discuss how relevant IOUS findings directly impact surgical decompression.
MATERIALS AND METHODS Study Design, Purpose, and Data Analysis This study is a technical report and presentation of 3 illustrative cases. For the latter, we reviewed our archive of stored IOUS data and selected 3 illustrative cases of patients who
Division of Neurosurgery, St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada To whom correspondence should be addressed: Ralph T. Schär, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2019) 121:62-70. https://doi.org/10.1016/j.wneu.2018.09.217 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter Crown Copyright ª 2018 Published by Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.217
TECHNICAL NOTE
Figure 1. Intraoperative ultrasound (IOUS) view of the cervical spinal cord. (A) In the axial view of the decompressed spinal cord (asterisk), both the dorsal and ventral roots are clearly visibly surrounded by cerebrospinal fluid. (B) In the sagittal plane, the degree of compression from an anterior disk (degree symbol)
to the spinal cord (asterisk) can be appreciated. Also, high-resolution IOUS depicts the interface between cerebrospinal fluid and the pia mater (black arrows) and the central canal (white arrows). CSF, cerebrospinal fluid; dr, dorsal roots; vr, ventral roots.
Figure 2. (A) Preoperative sagittal T2-weighted magnetic resonance imaging showing cervical stenosis at C5-6 and C6-7. (B) Axial view of C6-7 with prominent
osteochondral bar and cord compression is shown (corresponding to white reference line in A).
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TECHNICAL NOTE
tomographyebased 3D-dimensional stereotactic navigation system (Stryker Spine, Kalamazoo, Michigan, USA) was used for screw insertion. Laminectomy was performed under the microscope by identifying the medial borders of the lateral masses and drilling a trough through the laminae down to the epidural space on both sides. The detached posterior elements were subsequently gently pulled off and removed. PCL was completed with bone punches under IOUS guidance as subsequently described. Real-Time IOUS and Definition of Relevant IOUS Findings IOUS was performed using the ProSound Alpha 7 ultrasound system (ALOKA Co. [Hitachi Healthcare Americas, Twinsburg, Ohio, USA]) with a 6.6- to 13.3-MHz B-mode setting. To obtain optimal ultrasound imaging quality, the laminectomy site was filled with saline for acoustic coupling. A linear hockey stick ultrasound transducer (Aloka UST-536 [Hitachi Healthcare Americas]) was then placed over the dura to assess the extent of decompression via the laminectomy corridor in both the sagittal and axial planes. By this means, the cervical spinal cord and the ventral and dorsal nerve roots were clearly identifiable in every case (Figure 1). In particular, the lateral and craniocaudal margins of the laminectomy site were inspected in both planes for residual compression of spinal cord or nerve roots. Relevant IOUS findings were defined as ultrasonographic detection of residual focal compression of the spinal cord or nerve roots after laminectomy that led to further extended decompression of neural elements. For confirmation of sufficient decompression, we looked for posterior shift of the spinal cord away from previously compressive anteriorly located structures, such as intervertebral disks or ossification of the posterior longitudinal ligament (OPLL), and detection of symmetric and rhythmic cord pulsations. Figure 3. Preoperative sagittal computed tomography scan showing advanced degenerative changes and collapsed disks at C5-6 and C6-7 with evidence of ossification of the posterior longitudinal ligament at C6-7.
underwent PCL for DCM with ultrasound guidance. The purpose of this study was to describe the use and value of IOUS for PCL in patients with DCM. For these cases, pre- and postoperative imaging, preoperative and follow-up clinic notes, and the operative reports and IOUS images were reviewed. Surgical Technique of PCL with and without Fusion After endotracheal intubation, the patient’s head was fixed in a neutral position with a Mayfield clamp and attached to a Jackson table (Mizuho OSI, Union City, California, USA) before carefully rotating the fully secured patient into the prone position. Lateral C-arm fluoroscopy (Ziehm Vision FD Vario 3D [Ziehm Imaging, Nuremberg, Germany]) was used to identify and mark the surgical index levels. The posterior elements of the cervical spine were exposed through a midline incision and standard subperiosteal fashion. In cases for which an instrumented fusion was found to be necessary, screw hole preparation and screw insertion were completed before laminectomy to minimize the risk of iatrogenic cord injury by crossing of instruments over the unprotected spinal cord. For C1, C2, and vertebrae below C6, a computed
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RESULTS For this report we present 3 illustrative cases of patients with DCM. All patients underwent PCL with IOUS guidance and instrumented fusion. The short case presentations focus on preoperative imaging, clinical assessments, and the impact IOUS had during the surgical procedure.
Case 1 For many years, a 79-year-old woman had been suffering from slowly progressive numbness in her hands, neck pain, radiating pain in her arms, especially on the right side, and decreased hand dexterity. Also, because of unsteady gait, the patient had been using a cane for years. Her family doctor had ordered a magnetic resonance imaging scan of her cervical spine that revealed loss of lordosis and multilevel degenerative changes. Most notably, there was cervical stenosis at C6-7 with cord compression and moderate stenosis at C5-6 without T2 signal abnormalities within the cord (Figure 2). When the patient presented to our clinic, she demonstrated reduced range of motion of her neck and an unsteady tandem gait with no neurologic deficits. The arm pains were in line with bilateral C6 and C7 radiculopathies. A computed tomography scan was obtained and showed evidence of OPLL at C6-7 (Figure 3). The patient underwent a PCL of C5 and C6 with posterior instrumented fusion from C3 to C7. After PCL, we used IOUS
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.217
TECHNICAL NOTE
Figure 4. (A and B) Intraoperative ultrasound (IOUS) view of the decompressed cervical spinal cord in the axial and (C) sagittal plane. (B)
Ossification of the posterior longitudinal ligament (asterisk) appears hyperechoic in IOUS.
Figure 5. (A) Overview of sagittal T2-weighted magnetic resonance imaging of the cervical spine with highlighted box of the C6-7 level magnified (B) and the corresponding intraoperative ultrasound image (C). On ultrasound, the
amount of residual compression of the pulsating spinal cord by the anterior disk and ossification of the posterior longitudinal ligament can be easily assessed.
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walk unassisted and depended on a wheelchair most of the time. A magnetic resonance imaging scan of his cervical and upper thoracic spine showed severe multilevel degenerative changes with deformity, retro- and anterolisthesis of several segments, and cervical stenosis from C3 to T2. The maximum level of cord compression was seen at C7 and T1 (Figure 6). Clinically, the patient had mild quadriparesis, increased deep tendon reflexes in both his upper and lower extremities, and bilateral positive Babinski and Hoffmann signs. The patient consented to surgical treatment and underwent PCL from C3 to C7, laminectomy of T1 and T2, and instrumented fusion from C2 to T2. Subsequently, after all laminectomies were completed, IOUS confirmed sufficient decompression, and symmetric and rhythmic pulsations of the cord along the decompression could be appreciated, and a posterior shift of the cord away from the anterior intervertebral disks (Figure 7). Surgery was uneventful, and the patient was sent to rehabilitation a few days postoperatively. At 3-month follow-up, he had regained the strength in his legs and arms and was able to stand unassisted. He had reduced numbness in his hands and legs and increased hand dexterity.
Case 3
Figure 6. Sagittal view of preoperative T2-weighted magnetic resonance imaging showing multilevel degenerative changes and cervical stenosis including the cervicothoracic junction.
with a linear hockey stick transducer to evaluate the extent of decompression. Some residual compression was visualized within the proximal left C5-6, which was then further decompressed under IOUS guidance. In the same fashion, the C4 and C7 laminas were undercut until there was no more evidence of cord compression on ultrasound. Finally, a moderate posterior shift of the cord away from the previously compressive OPLL was noted on IOUS and symmetric and rhythmic cord pulsations (Figures 4 and 5). The patient recovered well from the uneventful surgery and was soon discharged to an inpatient rehabilitation facility. At 6-week follow-up, her gait difficulties had not improved. However, her radiating arm pains and hand numbness had completely disappeared, and her hand dexterity had improved. Clinically, she had full power in all extremities.
A 76-year-old woman had been experiencing constant paresthesia for several months in both hands, which first occurred after a dental procedure where she had to extend her neck and tilt her head to the right for a long period of time. She also described reduced dexterity in both hands, but felt otherwise strong in her arms. On examination, she had some reduced range of motion of her neck, and she had normal muscle tone and strength in her arms and legs. Sensory examination was normal in her hands, with some patchy pinprick loss in her lower extremities. A magnetic resonance imaging scan of her cervical spine showed severe cervical stenosis at C3-4 and C4-5 with low-grade retrolisthesis of both C3-4 and C4-5 (Figure 8). The patient underwent PCL of C4 and C5 with posterior instrumented fusion from C3 to C5. After the laminectomy, IOUS illustrated residual right C4-5 foraminal compression with asymmetric pulsations of the cord (Figure 9A). Consequently, a right C4-5 foraminotomy was performed, and sufficient decompression was finally seen on IOUS (Figures 9B and 10). Surgery was completed uneventfully and without intraoperative complications. Postoperatively, the patient developed a transient right C5 palsy with nearly complete loss of power in her deltoid and biceps (M1/5). However, at her 6-week follow-up appointment, she had already regained much of her strength in her right arm (M3/5) and had fully recovered by 3-month follow-up (M5/5). Her paresthesia in her hands had remained unchanged.
DISCUSSION IOUS in Spine Surgery
Case 2 A 67-year-old man with a known history of rheumatoid arthritis was experiencing mild weakness in his legs and unsteadiness in his gait for 5 months. His symptoms had further progressed during the last 2 months to the point where he was unable to
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Ultrasound remains one of the most widely used diagnostic tools in many specialties in medicine today because of its availability, relatively low cost, and easy operability also by nonradiologists. First reports of IOUS in spine surgery as a valuable adjunct for real-time visualization of various pathologies in the spine, such as tumors, cysts, and syringomyelia, were published in the
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.217
TECHNICAL NOTE
Figure 7. (A) Axial and (B) sagittal intraoperative ultrasound (IOUS) view of the decompressed cervical spinal cord. (C) Preoperative sagittal T2-weighted magnetic resonance imaging with projected box corresponding to B onto the cervical spine at the
1980s.6-9 Today, many spine surgeons use IOUS to specifically tailor the extent of bone removal and to safely guide resection of intradural extramedullary and intramedullary tumors while preserving normal tissue and to confirm sufficient decompression of lesions ventral to the thecal sac, such as calcified thoracic disk herniations or retropulsed bone fragments in spine trauma.10-12 However, the use of IOUS guidance for PCL has not been reported in the literature to date, with the exception of 2 accounts mentioning IOUS during cervical laminoplasty in patients with DCM.13,14
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respective vertebral body levels C5 and C6. (D) The same image is shown with an overlay of the respective IOUS view of the spinal cord and hockey stick transducer simulating the intraoperative setting.
Complications and Outcome After PCL for DCM To date, multiple studies in the literature have demonstrated operative management for symptomatic DCM to be safe, effective, and often result in improvement of neurologic function.15 However, as pointed out earlier, incomplete decompression of the cervical spinal cord and nerve roots may lead to persistent or new onset of neurologic symptoms, poor neurologic recovery, or deterioration. Reported complication rates and outcome scores after PCL in the literature vary considerably. Data pooled from 2 related
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TECHNICAL NOTE
Figure 8. (A) Preoperative sagittal T2-weighted magnetic resonance imaging showing cervical stenosis at C3-4 and stenosis with retrolisthesis at C4-5. (B)
international multicenter studies revealed an overall surgical complication rate within 30 days after a posterior approach for DCM in 180 patients to be 13.3%, including worsening of neurologic deficits (1.7%) and C5 radiculopathy (1.7%).16 The same study reported a 46% recovery rate, and a mean improvement in the modified Japanese Orthopedic Association score of 1.6 after 2 years. A review of older studies found a broad spectrum of neurologic improvement rates after PCL for DCM ranging from 40% to 95%, as previously mentioned.4 Although another study reported the incidence of new cervical radiculopathy, including C5 radiculopathy, to be just 4% for both PCL with fusion and laminoplasty, the authors of yet another retrospective analysis of 61 cases demonstrated postoperative radiculopathies occurring in nearly 20% of patients after PCL and fusion, of which 6.5% were irreversible.17,18 There is no mention of the use of IOUS in any of these studies, and the rate of residual postoperative compression to the neural elements was not reported and remains undetermined. Therefore, one might argue that routinely using ultrasound guidance for posterior decompression in DCM might be beneficial regarding complication rate and functional outcome by eliminating the risk of incomplete decompression. However, this would require further study.
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Axial view of C3-4 showing both anterior and posterior cord compression (corresponding to white reference line in A).
Advantages of IOUS Guidance for PCL In our experience with routinely using ultrasound for real-time visualization of the spinal cord and nerve roots after PCL, the neural elements in question are clearly visible, and adequate decompression can be confidently achieved in every case with IOUS guidance. In 2 of the 3 presented cases, IOUS led to additional extended focal decompression of the spinal cord and proximal nerve roots. This nicely underscores the value of IOUS for posterior decompression in the cervical spine by virtually eliminating the risk of residual cord or nerve root compression. As seen on ultrasound, the spinal cord is a highly dynamic structure with rhythmic pulsations, that have been described to be synchronous in 2 phases with the heart beat and respiratory cycle.19 IOUS remains the only imaging modality that enables surgeons to directly appreciate these crucial features of the spinal cord in real time and allows for a better understanding and assessment of cord decompression. Preoperative magnetic resonance imaging on the other hand is only able to reflect a static image of the cord by basically merging the cord pulsations to one delineation, provided that cord pulsations are not impeded by compression. With conventional posterior decompression in the cervical spine, the surgeon has no direct visualization of the neural
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.217
TECHNICAL NOTE
Figure 9. (A) Dorsal and ventral roots and lateral borders of the cord are seen in the axial view after decompression. A slight posterior shift of the cord is
also seen on this view. (B) Sagittal view of the decompressed cord showing spondylolisthesis of the vertebral bodies anterior to the cord.
Figure 10. (A) After posterior cervical laminectomy, the left lateral margin of the cord and the proximal nerve roots still show evidence of compression. (B) The
respective neural elements are further decompressed using ultrasound guidance.
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elements, and the amount of bony removal is driven by the appearance of the dura and by probing the bony margins with a dissector. However, the goal of surgery is decompression of the spinal cord and nerve roots. IOUS allows the surgeon to directly assess the spinal cord within the thecal sac and visualize any focal residual compression surrounding the cord. As soon as the cord and proximal rootlets are seen freely and symmetrically pulsating embedded by cerebrospinal fluid within the dura, there is no need for further bony decompression. Limiting bone removal to as much as necessary and as little as possible is especially important in noninstrumented cases to avoid secondary instability and segmental kyphosis. In most cases, the dura and spinal cord will shift posteriorly to some degree after PCL, and the amount of indirect anterior decompression in cases of OPLL or with prominent osteochondral bars can be instantly and easily assessed with IOUS. In selected cases, this might help in the decision-making of
REFERENCES
whether a second anterior approach and decompression is needed or not. Despite all of the aforementioned advantages of IOUS, postoperative neurologic deficits may still arise, as seen with our patient presented in case 3, who developed a transient C5 palsy. However, one might argue that her neurologic recovery might be attributed to the extended selective C4-5 foraminal decompression because residual compression was detected on ultrasound after laminectomy. Admittedly, this argument remains speculative because the exact pathomechanism of a postoperative C5 palsy is still not fully understood today. In conclusion, IOUS is an easy-to-use and very effective tool for guidance and confirmation of adequate posterior decompression of the cervical spinal cord and nerve roots. Routinely using IOUSguided decompression in patients with myelopathy will help avoid residual postoperative compression to the neural elements and might thereby further improve functional outcome.
9. Rubin JM, Dohrmann GJ. The spine and spinal cord during neurosurgical operations: real-time ultrasonography. Radiology. 1985;155:197-200.
1. Laratta JL, Shillingford JN, Cohen-Tanugi S, Lombardi JM, Lenke LG, Riew KD, et al. Defining the "critical elements" for the most common procedures in spine surgery: a consensus of orthopedic and neurosurgical surgeons. Spine (Phila Pa 1976). 2018;43:E531-E536.
10. Juthani RG, Bilsky MH, Vogelbaum MA. Current management and treatment modalities for intramedullary spinal cord tumors. Curr Treat Options Oncol. 2015;16:39.
2. Kumar VG, Rea GL, Mervis LJ, McGregor JM. Cervical spondylotic myelopathy: functional and radiographic long-term outcome after laminectomy and posterior fusion. Neurosurgery. 1999; 44:771-777 [discussion: 777-778].
11. Nishimura Y, Thani NB, Tochigi S, Ahn H, Ginsberg HJ. Thoracic discectomy by posterior pedicle-sparing, transfacet approach with realtime intraoperative ultrasonography: clinical article. J Neurosurg Spine. 2014;21:568-576.
3. Epstein N. Posterior approaches in the management of cervical spondylosis and ossification of the posterior longitudinal ligament. Surg Neurol. 2002;58:194-207 [discussion: 207-208].
12. Lazennec JY, Sailland G, Ramare S, Hansen S. [Intraoperative ultrasound study of thoracolumbar spinal fractures with spinal canal fragments. Determining canal width and anatomic control of decompression: comparative analysis with CT]. Unfallchirurg. 1998;101:353-359 [Article in German].
4. Mayer M, Meier O, Auffarth A, Koller H. Cervical laminectomy and instrumented lateral mass fusion: techniques, pearls and pitfalls. Eur Spine J. 2015;24(suppl 2):168-185. 5. Vasudeva VS, Abd-El-Barr M, Pompeu YA, Karhade A, Groff MW, Lu Y. Use of intraoperative ultrasound during spinal surgery. Global Spine J. 2017;7:648-656. 6. Dohrmann GJ, Rubin JM. Intraoperative ultrasound imaging of the spinal cord: syringomyelia, cysts, and tumorsea preliminary report. Surg Neurol. 1982;18:395-399. 7. Montalvo BM, Quencer RM. Intraoperative sonography in spinal surgery: current state of the art. Neuroradiology. 1986;28:551-590. 8. Raymond CA. Brain, spine surgeons say yes to ultrasound. JAMA. 1986;255:2258-2259.2262.
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13. Kimura A, Seichi A, Inoue H, Endo T, Sato M, Higashi T, et al. Ultrasonographic quantification of spinal cord and dural pulsations during cervical laminoplasty in patients with compressive myelopathy. Eur Spine J. 2012;21:2450-2455. 14. Seichi A, Chikuda H, Kimura A, Takeshita K, Sugita S, Hoshino Y, et al. Intraoperative ultrasonographic evaluation of posterior decompression via laminoplasty in patients with cervical ossification of the posterior longitudinal ligament: correlation with 2-year follow-up results. J Neurosurg Spine. 2010;13:47-51. 15. Wilson JR, Tetreault LA, Kim J, Harrop JS, Mroz T, Cho S, et al. State of the art in degenerative cervical myelopathy: an update on current clinical evidence. Neurosurgery. 2017;80:S33-S45.
16. Kato S, Nouri A, Wu D, Nori S, Tetreault L, Fehlings MG. Comparison of anterior and posterior surgery for degenerative cervical myelopathy: an MRI-based propensity-score-matched analysis using data from the prospective multicenter AOSpine CSM North America and International Studies. J Bone Joint Surg Am. 2017;99:1013-1021. 17. Fehlings MG, Santaguida C, Tetreault L, Arnold P, Barbagallo G, Defino H, et al. Laminectomy and fusion versus laminoplasty for the treatment of degenerative cervical myelopathy: results from the AOSpine North America and International prospective multicenter studies. Spine J. 2017;17: 102-108. 18. Kristof RA, Kiefer T, Thudium M, Ringel F, Stoffel M, Kovacs A, et al. Comparison of ventral corpectomy and plate-screw-instrumented fusion with dorsal laminectomy and rod-screwinstrumented fusion for treatment of at least two vertebral-level spondylotic cervical myelopathy. Eur Spine J. 2009;18:1951-1956. 19. Jokich PM, Rubin JM, Dohrmann GJ. Intraoperative ultrasonic evaluation of spinal cord motion. J Neurosurg. 1984;60:707-711.
Received 23 August 2018; accepted 28 September 2018 Citation: World Neurosurg. (2019) 121:62-70. https://doi.org/10.1016/j.wneu.2018.09.217 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter Crown Copyright ª 2018 Published by Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.217
Intraoperative Ultrasound-Guided Posterior Cervical Laminectomy for Degenerative Cervical Myelopathy Ralph T. Scha¨r, Jefferson R. Wilson, Howard J. Ginsberg
OBJECTIVE: We present our experience with routine intraoperative ultrasound (IOUS)eguided posterior cervical laminectomy (PCL) in patients with degenerative cervical myelopathy (DCM), describe the technique used, and describe relevant IOUS findings that may impact the surgical procedure.
-
METHODS: Three illustrative cases are presented of patients (age range, 67e79 years) who underwent PCL with IOUS guidance and instrumented fusion for DCM. Intraoperative standard B-mode images were obtained with a linear array 6.6- to 13.3-MHz transducer.
-
RESULTS: Excellent high-resolution IOUS view of the spinal cord and nerve roots was obtained in every case after laminectomy. IOUS had a relevant intraoperative impact in all cases, leading to extended decompression of focal residual compression, confirmation of posterior shift of the spinal cord from anteriorly located structures, and final confirmation of sufficient decompression by visualization of symmetric and rhythmic cord pulsations.
-
CONCLUSIONS: IOUS is a poorly described yet easy-touse and very effective tool for guidance and confirmation of adequate posterior decompression of the cervical spinal cord and nerve roots during PCL. Routinely using IOUSguided decompression for PCL in patients with myelopathy will help avoid residual compression of neural elements and might be beneficial for functional outcome.
-
P
osterior cervical laminectomy (PCL) is a frequent operative procedure in spine surgery to decompress the spinal cord and nerve roots in patients with degenerative cervical
Key words Cervical fusion - Cervical laminectomy - Degenerative cervical myelopathy - Intraoperative ultrasound -
Abbreviations and Acronyms DCM: Degenerative cervical myelopathy IOUS: Intraoperative ultrasound OPLL: Ossification of the posterior longitudinal ligament PCL: Posterior cervical laminectomy
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myelopathy (DCM), deformity, traumatic spinal cord injury, and spinal tumors.1 Frequently, PCL is combined with an instrumented fusion, mainly to avoid secondary instability and postlaminectomy kyphosis. Outcome after PCL is generally good, and rates of neurologic improvement of 40%e95% have been reported depending on origin of pathology and duration of symptoms.2-4 However, after PCL, the extent of decompression may easily be misjudged because the surgeon can merely assess the appearance of the dura after bone removal, but has no direct visualization of the spinal cord and nerve roots or anteriorly located structures. Incomplete decompression of the spinal cord and nerve roots may lead to postoperative radiculopathy, persistent symptoms, poor neurologic recovery, or functional deterioration in patients with myelopathy. In recent years, the use of intraoperative ultrasound (IOUS) has become popular in both cranial neurosurgery and spine surgery and remains the only true real-time imaging modality allowing surgeons to instantly visualize soft tissue anatomy while operating.5 Although IOUS was introduced to spine surgery over 30 years ago, there is no description in the literature of ultrasound as an adjunctive intraoperative tool for PCL. The quality and clarity of the images have improved remarkably over this time period. We use IOUS for guidance of PCL on a routine basis to achieve and confirm adequate decompression of the neural elements. We herewith present our experience with IOUS-guided PCL, discuss technical aspects, and discuss how relevant IOUS findings directly impact surgical decompression.
MATERIALS AND METHODS Study Design, Purpose, and Data Analysis This study is a technical report and presentation of 3 illustrative cases. For the latter, we reviewed our archive of stored IOUS data and selected 3 illustrative cases of patients who
Division of Neurosurgery, St. Michael’s Hospital, University of Toronto, Toronto, Ontario, Canada To whom correspondence should be addressed: Ralph T. Schär, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2019) 121:62-70. https://doi.org/10.1016/j.wneu.2018.09.217 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter Crown Copyright ª 2018 Published by Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2018.09.217
TECHNICAL NOTE
Figure 1. Intraoperative ultrasound (IOUS) view of the cervical spinal cord. (A) In the axial view of the decompressed spinal cord (asterisk), both the dorsal and ventral roots are clearly visibly surrounded by cerebrospinal fluid. (B) In the sagittal plane, the degree of compression from an anterior disk (degree symbol)
to the spinal cord (asterisk) can be appreciated. Also, high-resolution IOUS depicts the interface between cerebrospinal fluid and the pia mater (black arrows) and the central canal (white arrows). CSF, cerebrospinal fluid; dr, dorsal roots; vr, ventral roots.
Figure 2. (A) Preoperative sagittal T2-weighted magnetic resonance imaging showing cervical stenosis at C5-6 and C6-7. (B) Axial view of C6-7 with prominent
osteochondral bar and cord compression is shown (corresponding to white reference line in A).
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tomographyebased 3D-dimensional stereotactic navigation system (Stryker Spine, Kalamazoo, Michigan, USA) was used for screw insertion. Laminectomy was performed under the microscope by identifying the medial borders of the lateral masses and drilling a trough through the laminae down to the epidural space on both sides. The detached posterior elements were subsequently gently pulled off and removed. PCL was completed with bone punches under IOUS guidance as subsequently described. Real-Time IOUS and Definition of Relevant IOUS Findings IOUS was performed using the ProSound Alpha 7 ultrasound system (ALOKA Co. [Hitachi Healthcare Americas, Twinsburg, Ohio, USA]) with a 6.6- to 13.3-MHz B-mode setting. To obtain optimal ultrasound imaging quality, the laminectomy site was filled with saline for acoustic coupling. A linear hockey stick ultrasound transducer (Aloka UST-536 [Hitachi Healthcare Americas]) was then placed over the dura to assess the extent of decompression via the laminectomy corridor in both the sagittal and axial planes. By this means, the cervical spinal cord and the ventral and dorsal nerve roots were clearly identifiable in every case (Figure 1). In particular, the lateral and craniocaudal margins of the laminectomy site were inspected in both planes for residual compression of spinal cord or nerve roots. Relevant IOUS findings were defined as ultrasonographic detection of residual focal compression of the spinal cord or nerve roots after laminectomy that led to further extended decompression of neural elements. For confirmation of sufficient decompression, we looked for posterior shift of the spinal cord away from previously compressive anteriorly located structures, such as intervertebral disks or ossification of the posterior longitudinal ligament (OPLL), and detection of symmetric and rhythmic cord pulsations. Figure 3. Preoperative sagittal computed tomography scan showing advanced degenerative changes and collapsed disks at C5-6 and C6-7 with evidence of ossification of the posterior longitudinal ligament at C6-7.
underwent PCL for DCM with ultrasound guidance. The purpose of this study was to describe the use and value of IOUS for PCL in patients with DCM. For these cases, pre- and postoperative imaging, preoperative and follow-up clinic notes, and the operative reports and IOUS images were reviewed. Surgical Technique of PCL with and without Fusion After endotracheal intubation, the patient’s head was fixed in a neutral position with a Mayfield clamp and attached to a Jackson table (Mizuho OSI, Union City, California, USA) before carefully rotating the fully secured patient into the prone position. Lateral C-arm fluoroscopy (Ziehm Vision FD Vario 3D [Ziehm Imaging, Nuremberg, Germany]) was used to identify and mark the surgical index levels. The posterior elements of the cervical spine were exposed through a midline incision and standard subperiosteal fashion. In cases for which an instrumented fusion was found to be necessary, screw hole preparation and screw insertion were completed before laminectomy to minimize the risk of iatrogenic cord injury by crossing of instruments over the unprotected spinal cord. For C1, C2, and vertebrae below C6, a computed
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RESULTS For this report we present 3 illustrative cases of patients with DCM. All patients underwent PCL with IOUS guidance and instrumented fusion. The short case presentations focus on preoperative imaging, clinical assessments, and the impact IOUS had during the surgical procedure.
Case 1 For many years, a 79-year-old woman had been suffering from slowly progressive numbness in her hands, neck pain, radiating pain in her arms, especially on the right side, and decreased hand dexterity. Also, because of unsteady gait, the patient had been using a cane for years. Her family doctor had ordered a magnetic resonance imaging scan of her cervical spine that revealed loss of lordosis and multilevel degenerative changes. Most notably, there was cervical stenosis at C6-7 with cord compression and moderate stenosis at C5-6 without T2 signal abnormalities within the cord (Figure 2). When the patient presented to our clinic, she demonstrated reduced range of motion of her neck and an unsteady tandem gait with no neurologic deficits. The arm pains were in line with bilateral C6 and C7 radiculopathies. A computed tomography scan was obtained and showed evidence of OPLL at C6-7 (Figure 3). The patient underwent a PCL of C5 and C6 with posterior instrumented fusion from C3 to C7. After PCL, we used IOUS
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Figure 4. (A and B) Intraoperative ultrasound (IOUS) view of the decompressed cervical spinal cord in the axial and (C) sagittal plane. (B)
Ossification of the posterior longitudinal ligament (asterisk) appears hyperechoic in IOUS.
Figure 5. (A) Overview of sagittal T2-weighted magnetic resonance imaging of the cervical spine with highlighted box of the C6-7 level magnified (B) and the corresponding intraoperative ultrasound image (C). On ultrasound, the
amount of residual compression of the pulsating spinal cord by the anterior disk and ossification of the posterior longitudinal ligament can be easily assessed.
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walk unassisted and depended on a wheelchair most of the time. A magnetic resonance imaging scan of his cervical and upper thoracic spine showed severe multilevel degenerative changes with deformity, retro- and anterolisthesis of several segments, and cervical stenosis from C3 to T2. The maximum level of cord compression was seen at C7 and T1 (Figure 6). Clinically, the patient had mild quadriparesis, increased deep tendon reflexes in both his upper and lower extremities, and bilateral positive Babinski and Hoffmann signs. The patient consented to surgical treatment and underwent PCL from C3 to C7, laminectomy of T1 and T2, and instrumented fusion from C2 to T2. Subsequently, after all laminectomies were completed, IOUS confirmed sufficient decompression, and symmetric and rhythmic pulsations of the cord along the decompression could be appreciated, and a posterior shift of the cord away from the anterior intervertebral disks (Figure 7). Surgery was uneventful, and the patient was sent to rehabilitation a few days postoperatively. At 3-month follow-up, he had regained the strength in his legs and arms and was able to stand unassisted. He had reduced numbness in his hands and legs and increased hand dexterity.
Case 3
Figure 6. Sagittal view of preoperative T2-weighted magnetic resonance imaging showing multilevel degenerative changes and cervical stenosis including the cervicothoracic junction.
with a linear hockey stick transducer to evaluate the extent of decompression. Some residual compression was visualized within the proximal left C5-6, which was then further decompressed under IOUS guidance. In the same fashion, the C4 and C7 laminas were undercut until there was no more evidence of cord compression on ultrasound. Finally, a moderate posterior shift of the cord away from the previously compressive OPLL was noted on IOUS and symmetric and rhythmic cord pulsations (Figures 4 and 5). The patient recovered well from the uneventful surgery and was soon discharged to an inpatient rehabilitation facility. At 6-week follow-up, her gait difficulties had not improved. However, her radiating arm pains and hand numbness had completely disappeared, and her hand dexterity had improved. Clinically, she had full power in all extremities.
A 76-year-old woman had been experiencing constant paresthesia for several months in both hands, which first occurred after a dental procedure where she had to extend her neck and tilt her head to the right for a long period of time. She also described reduced dexterity in both hands, but felt otherwise strong in her arms. On examination, she had some reduced range of motion of her neck, and she had normal muscle tone and strength in her arms and legs. Sensory examination was normal in her hands, with some patchy pinprick loss in her lower extremities. A magnetic resonance imaging scan of her cervical spine showed severe cervical stenosis at C3-4 and C4-5 with low-grade retrolisthesis of both C3-4 and C4-5 (Figure 8). The patient underwent PCL of C4 and C5 with posterior instrumented fusion from C3 to C5. After the laminectomy, IOUS illustrated residual right C4-5 foraminal compression with asymmetric pulsations of the cord (Figure 9A). Consequently, a right C4-5 foraminotomy was performed, and sufficient decompression was finally seen on IOUS (Figures 9B and 10). Surgery was completed uneventfully and without intraoperative complications. Postoperatively, the patient developed a transient right C5 palsy with nearly complete loss of power in her deltoid and biceps (M1/5). However, at her 6-week follow-up appointment, she had already regained much of her strength in her right arm (M3/5) and had fully recovered by 3-month follow-up (M5/5). Her paresthesia in her hands had remained unchanged.
DISCUSSION IOUS in Spine Surgery
Case 2 A 67-year-old man with a known history of rheumatoid arthritis was experiencing mild weakness in his legs and unsteadiness in his gait for 5 months. His symptoms had further progressed during the last 2 months to the point where he was unable to
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Ultrasound remains one of the most widely used diagnostic tools in many specialties in medicine today because of its availability, relatively low cost, and easy operability also by nonradiologists. First reports of IOUS in spine surgery as a valuable adjunct for real-time visualization of various pathologies in the spine, such as tumors, cysts, and syringomyelia, were published in the
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Figure 7. (A) Axial and (B) sagittal intraoperative ultrasound (IOUS) view of the decompressed cervical spinal cord. (C) Preoperative sagittal T2-weighted magnetic resonance imaging with projected box corresponding to B onto the cervical spine at the
1980s.6-9 Today, many spine surgeons use IOUS to specifically tailor the extent of bone removal and to safely guide resection of intradural extramedullary and intramedullary tumors while preserving normal tissue and to confirm sufficient decompression of lesions ventral to the thecal sac, such as calcified thoracic disk herniations or retropulsed bone fragments in spine trauma.10-12 However, the use of IOUS guidance for PCL has not been reported in the literature to date, with the exception of 2 accounts mentioning IOUS during cervical laminoplasty in patients with DCM.13,14
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respective vertebral body levels C5 and C6. (D) The same image is shown with an overlay of the respective IOUS view of the spinal cord and hockey stick transducer simulating the intraoperative setting.
Complications and Outcome After PCL for DCM To date, multiple studies in the literature have demonstrated operative management for symptomatic DCM to be safe, effective, and often result in improvement of neurologic function.15 However, as pointed out earlier, incomplete decompression of the cervical spinal cord and nerve roots may lead to persistent or new onset of neurologic symptoms, poor neurologic recovery, or deterioration. Reported complication rates and outcome scores after PCL in the literature vary considerably. Data pooled from 2 related
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Figure 8. (A) Preoperative sagittal T2-weighted magnetic resonance imaging showing cervical stenosis at C3-4 and stenosis with retrolisthesis at C4-5. (B)
international multicenter studies revealed an overall surgical complication rate within 30 days after a posterior approach for DCM in 180 patients to be 13.3%, including worsening of neurologic deficits (1.7%) and C5 radiculopathy (1.7%).16 The same study reported a 46% recovery rate, and a mean improvement in the modified Japanese Orthopedic Association score of 1.6 after 2 years. A review of older studies found a broad spectrum of neurologic improvement rates after PCL for DCM ranging from 40% to 95%, as previously mentioned.4 Although another study reported the incidence of new cervical radiculopathy, including C5 radiculopathy, to be just 4% for both PCL with fusion and laminoplasty, the authors of yet another retrospective analysis of 61 cases demonstrated postoperative radiculopathies occurring in nearly 20% of patients after PCL and fusion, of which 6.5% were irreversible.17,18 There is no mention of the use of IOUS in any of these studies, and the rate of residual postoperative compression to the neural elements was not reported and remains undetermined. Therefore, one might argue that routinely using ultrasound guidance for posterior decompression in DCM might be beneficial regarding complication rate and functional outcome by eliminating the risk of incomplete decompression. However, this would require further study.
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Axial view of C3-4 showing both anterior and posterior cord compression (corresponding to white reference line in A).
Advantages of IOUS Guidance for PCL In our experience with routinely using ultrasound for real-time visualization of the spinal cord and nerve roots after PCL, the neural elements in question are clearly visible, and adequate decompression can be confidently achieved in every case with IOUS guidance. In 2 of the 3 presented cases, IOUS led to additional extended focal decompression of the spinal cord and proximal nerve roots. This nicely underscores the value of IOUS for posterior decompression in the cervical spine by virtually eliminating the risk of residual cord or nerve root compression. As seen on ultrasound, the spinal cord is a highly dynamic structure with rhythmic pulsations, that have been described to be synchronous in 2 phases with the heart beat and respiratory cycle.19 IOUS remains the only imaging modality that enables surgeons to directly appreciate these crucial features of the spinal cord in real time and allows for a better understanding and assessment of cord decompression. Preoperative magnetic resonance imaging on the other hand is only able to reflect a static image of the cord by basically merging the cord pulsations to one delineation, provided that cord pulsations are not impeded by compression. With conventional posterior decompression in the cervical spine, the surgeon has no direct visualization of the neural
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Figure 9. (A) Dorsal and ventral roots and lateral borders of the cord are seen in the axial view after decompression. A slight posterior shift of the cord is
also seen on this view. (B) Sagittal view of the decompressed cord showing spondylolisthesis of the vertebral bodies anterior to the cord.
Figure 10. (A) After posterior cervical laminectomy, the left lateral margin of the cord and the proximal nerve roots still show evidence of compression. (B) The
respective neural elements are further decompressed using ultrasound guidance.
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elements, and the amount of bony removal is driven by the appearance of the dura and by probing the bony margins with a dissector. However, the goal of surgery is decompression of the spinal cord and nerve roots. IOUS allows the surgeon to directly assess the spinal cord within the thecal sac and visualize any focal residual compression surrounding the cord. As soon as the cord and proximal rootlets are seen freely and symmetrically pulsating embedded by cerebrospinal fluid within the dura, there is no need for further bony decompression. Limiting bone removal to as much as necessary and as little as possible is especially important in noninstrumented cases to avoid secondary instability and segmental kyphosis. In most cases, the dura and spinal cord will shift posteriorly to some degree after PCL, and the amount of indirect anterior decompression in cases of OPLL or with prominent osteochondral bars can be instantly and easily assessed with IOUS. In selected cases, this might help in the decision-making of
REFERENCES
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Received 23 August 2018; accepted 28 September 2018 Citation: World Neurosurg. (2019) 121:62-70. https://doi.org/10.1016/j.wneu.2018.09.217 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter Crown Copyright ª 2018 Published by Elsevier Inc. All rights reserved.
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