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Reprint of: Safe Route for Cervical Approach: Partial Pediculotomy, Partial Vertebrotomy Approach for Posterior Endoscopic Cervical Foraminotomy and Discectomy
Endoscopic Spine Surgery Special Section
Reprint of: Safe Route for Cervical Approach: Partial Pediculotomy, Partial Vertebrotomy Approach for Posterior Endoscopic Cervical Foraminotomy and Discectomy Hyeun Sung Kim1, Pang Hung Wu1,2, Yeon Jin Lee1, Dae Hwan Kim1, Ji Yeon Kim1, Jun Hyung Lee1, Jun Bok Jeon1, Il-Tae Jang1
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BACKGROUND: Cervical radiculopathy is a common cervical spine condition. However, a paucity of data is available on the effect of partial pediculotomy and partial vertebrotomy (PPPV) for posterior endoscopic cervical foraminotomy (PECF) to treat cervical radiculopathy. We investigated the radiological and clinical outcomes of this approach.
increase in decompression in the foramen area for all CTmeasured parameters compared with the mean preoperative values: 1) the sagittal area increased 60.1 23.1 mm2; 2) the craniocaudal length increased 4.0 1.54 mm; and 3) the ventrodorsal length increased 4.0 1.97 mm; Also, the 3-dimensional CT scan reconstruction decompression area had increased 996 266 mm2 (P < 0.05).
METHODS: We performed a retrospective evaluation of 30 patients with cervical radiculopathy who had undergone PPPV PECF. Pre- and postoperative radiographs were performed to evaluate for stability, and computed tomography (CT) was used to evaluate the foraminal dimensions and area in the sagittal view. Three-dimensional reconstruction of the area of decompression was also performed. The clinical outcomes were evaluated using the visual analog scale, Oswestry disability index, and the MacNab criteria.
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RESULTS: No complications or recurrence developed in our PPPV PECF cohort during the study period. At the preoperative, 1-week postoperative, 3-month postoperative, and final follow-up examinations, the mean visual analog scale scores and mean Oswestry disability index showed significant improvement (score, 7.6, 3.0, 2.1, and 1.7, respectively; P < 0.05; and score, 73.9, 28.1, 23.3, and 21.5, respectively; P < 0.05). All the patients scored good to excellent using the MacNab criteria. The radiological findings showed that PPPV PECF resulted in a significant
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Key words Cervical decompression - Cervical radiculopathy - Endoscopic spine surgery - Pedicule - Posterior cervical endoscopic foraminotomy - Posterior endoscopic cervical discectomy - Prolapsed intervertebral disc -
Abbreviations and Acronyms CT: Computed tomography MRI: Magnetic resonance imaging ODI: Oswestry disability index PECF: Posterior endoscopic cervical foraminotomy and discectomy
CONCLUSION: PPPV PECF is a safe route for decompression of the cervical spine with good clinical and radiological outcomes.
INTRODUCTION
C
ervical radiculopathy is a common cervical spine condition leading to significant disability from nerve root dysfunction.1 Conservative therapy is recommended for 6 weeks for cervical radiculopathy without myelopathy.1,2 The time to recovery has ranged from 2 weeks to 3 years for 83% of patients.3 However, a good proportion of patients will remain symptomatic despite being compliant with conservative treatment.3 Anterior cervical discectomy and fusion and cervical artificial disc replacement has been the reference standard treatment.4 The morbidity attributed to anterior cervical surgery has ranged from 13.2% to 19.3%, with pseudoarthrosis and adjacent segment disease the most common postoperative
PPPV: Partial pediculotomy, partial vertebrotomy approach VAS: Visual analog scale From the 1Spine Surgery Center, Nanoori Gangnam Hospital, Seoul, Republic of Korea; and 2 Department of Orthopaedic Surgery, National University Health System, Jurong Health Campus, Singapore To whom correspondence should be addressed: Hyeun-Sung Kim, M.D., Ph.D. [E-mail: [email protected]] Hyeun Sung Kim and Pang Hung Wu are co-first authors. Citation: World Neurosurg. (2020). https://doi.org/10.1016/j.wneu.2020.10.158 Journal homepage: www.journals.elsevier.com/world-neurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2020 Elsevier Inc. All rights reserved.
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complications.5 Posterior cervical foraminotomy has increased in popularity as an alternative to anterior cervical discectomy and fusion, sparing the issues associated with fusion and surgical instrumentation, with equally good clinical results and the added advantage of motion preservation.6-8 Cervical endoscopic decompression is becoming popular as a soft tissue-conserving minimally invasive technique for cervical foraminal decompression and discectomy for a prolapsed intervertebral disc and foraminal stenosis.9-11 One of the concerns with endoscopic cervical foraminotomy and discectomy has been the neurological complications associated with the spinal cord and exiting nerve root retraction, leading to significant residual radicular pain and, on rare occasions, paralysis. Although incomplete decompression is a leading cause of residual radicular pain, the risk must be weighed against overly aggressive resection of the facet, which can lead to local failure of the facet joint.12 The safety of the approach to the cervical intervertebral disc is of paramount importance. We hypothesized that drilling the medial one third of the pedicle and corpus ventral to the spinal cord and exiting nerve root by 3 to 5 mm would create space for efficient discectomy and uncus decompression and preserve the stability of the spinal segment. Creating a space ventral to the neural elements helps to prevent the complications resulting from neural retraction using the endoscopic working channel. We performed the partial pediculotomy, partial vertebrotomy approach (PPPV) for posterior cervical foraminotomy and discectomy (PECF) to test our hypothesis. METHODS Patient Demographics The institutional review board of Nanoori Hospital (Seoul, Republic of Korea) approved the present retrospective comparison study. All included patients provided written informed consent. From January 2017 to December 2019, 30 patients had undergone uniportal PPPV PECF at 36 cervical intervertebral disc levels at our institute. The clinical presentation was intractable cervical radiculopathy, not relieved by >6 weeks of conservative treatment; motor and/or sensory impairment with cervical neuroforaminal nerve root compression resulting from a soft herniated cervical intervertebral disc or cervical foraminal stenosis secondary to a degenerative disc; and uncovertebral joint hypertrophy and osteophytes in a facet joint. The patients were required to have disc material and uncal hypertrophy present at the lateral aspect of the cervical intervertebral disc with one half of the bulk of disc material lateral to the thecal sac on the axial view of the magnetic resonance imaging (MRI) scan. We excluded patients with contraindications for posterior cervical spine decompression. The contraindications included a calcified central disc, instability of the cervical spine, significant cervical kyphosis of >10 , advanced cervical myelopathy, and predominant axial neck pain without radiculopathy. Outcomes Measures The baseline demographic variables recorded included age, sex, diagnosis, number of decompression levels, and levels of decompression. The clinical outcome measures included the visual analog scale (VAS) scores13 and Oswestry disability index
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(ODI).14 The VAS and ODI were completed preoperatively, at 1 week and 3 months postoperatively, and at the final follow-up evaluation. We also used the MacNab criteria at the final followup to evaluate for pain relief.15 The data were retrieved from the clinical note documentation by 2 experienced Korean spine surgeons (Y.J.L. and D.H.K.) who were not involved in the care of the study patients. Postoperative complications, any recurrence at the same or adjacent levels, reoperations, and neurological deficits were documented. Workstation software (Infinitt, Inc, Seoul, Republic of Korea) was used. The radiological variables were measured by 3 experienced spine surgeons (P.H.W., Y.J.L., D.H.K.) who were not involved in the care of the study subjects. Individual and consensus interpretations were obtained for each variable. Preoperative computed tomography (CT) scans, MRI studies, and plain radiographs were obtained for all patients. Instability was defined as >2 mm of motion at the operative segment or any adjacent segments on cervical dynamic plain radiographs. These patients were excluded from the present study. Comparisons of the MRI and CT data were performed using images obtained preoperatively and on postoperative day 1. These imaging studies were performed as a part of the hospital protocol and were used to assess the cause of cervical radiculopathy, disc position, disc size, and the presence of uncal vertebral hypertrophy and foraminal stenosis. Surgical decompression of these pathologies was also evaluated. We compared the pre- and postoperative midsagittal foraminal area, craniocaudal length, and ventrodorsal length in the first cut of the cephalad vertebral pedicle when scrolling from medially to laterally at the affected level. The posterior coronal view of the area of decompression was measured on the preoperative and 1-day postoperative 3-dimensional (3D) reconstructed CT scan. We ensured the reconstructed CT scan was a direct posterior view in which the cut showed the symmetrical size of the caudal lamina bilaterally. The measurement methods used for the CT parameters are shown in Figure 1. Description of PPPV PECF Technique The patients underwent general anesthesia and were positioned prone on a Wilson frame with shoulder strapped and the neck flexed in a slight, reverse Trendelenburg position using a 3-point plaster traction technique at the head, shoulder, and back without a Mayfield head clamp to increase the interlaminar space of the cervical spine.16 The patient’s face was positioned in a commercial anesthesia pillow foam to support the bony prominence with space created for the eyes, nose, and mouth. The head attachment was tilted down slightly to allow for cervical spine flexion and secured with plaster. The arms were padded and tucked longitudinally next to the patient. The anterior superior iliac spine and knees were padded, and the hips and knees were flexed slightly. Both the shoulders were strapped to pull the shoulders down slightly without pressure on the brachial plexus, with a final strap on the back to reduce the skin fold. We did not use neuromonitoring during any of our PPPV PECF procedures. Skin marking was performed with anteroposterior and lateral cervical fluoroscopic guidance (Figures 2 and 3). We aimed for the intersection of the intervertebral disc space and medial border of facet joint junction on the anteroposterior view
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ENDOSCOPIC SPINE SURGERY SPECIAL SECTION HYEUN SUNG KIM ET AL.
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SAFE ROUTE FOR CERVICAL APPROACH
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and at the facet joint of the correct level on the lateral view. This was correlated with the intraoperative view of the “V” point, defined as the junction of confluence of the cephalad and caudal laminal facets, which has a V-shaped configuration.17 A transverse 8-mm incision was made at the V point, and an obturator was inserted and docked, with the tip position confirmed by fluoroscopy. A 30 viewing angle, 7.3-mm outer diameter, and 4.7-mm working channel endoscope (Joimax GmbH, Karlsruhe, Germany) was used for the procedure with continuous normal saline irrigation at a pressure of 25 mm Hg. Hemostasis and soft tissue dissection was performed using a radiofrequency probe (Ellman bipolar radiofrequency electrocoagulator [Elliquence, Baldwin, New York, USA]) and endoscopic forceps. Once the V point had been identified and confirmed on fluoroscopy, the medial aspect of the lateral mass and facet joint was drilled using a long, straight, 3.5-mm diameter, coarse diamond, high-speed drill (Primado High-Speed Drill System [Nakanishi Inc, Surgical Division, Tochigi, Japan) to create a working window (Figure 4). The size of the window varied according to the size of the herniated material and degree of foraminal stenosis. Resection of the cephalad laminofacet was performed first. Typically, 3 to 5 mm in diameter of bone was removed from the lateral inferior aspect of the upper lamina, followed by ~3 mm of the medial inferior portion of the upper facet from the laminaefacet border (the V point).18 We then asked the anesthetist to tilt patient toward the surgeon to allow for resection at the medial superior articular facet of the lower vertebra. Approximately 3 to 5 mm in diameter was resected of the superomedial corner of the medial aspect of the superior articular facet of the caudal vertebra, close to the dorsal aspect of the nerve root, leading toward the proximal portion of the nerve root. We used a 3.5-mm diamond Primado II NSK drill bit (Nakanishi Inc, Surgical Division) for bone removal, with forceps and punches used to collect any loose bone fragments. After posterior foraminotomy had been completed, the exiting nerve root and spinal cord were exposed. We shifted the working cannula to center on the upper medial aspect of the pedicle, and drilled the pedicle 3 to 5-mm deeper than the neural element level to create a subneural working space to provide access to the herniated disc material. Using this method, minimal neural retraction was required during the discectomy. If a more central location of the disc had been noted on the preoperative MRI scan, a partial vertebrotomy approach was added. The lateral aspect of the corpus of the caudal cervical vertebra was drilled after the pedicle had been drilled to create a working space underneath the neural elements in a central location to provide access to the central disc without significant neural retraction. After drilling, a forceps or cutter was used to push the disc material and
osteophytes down to the subneural space created ventral to the neural elements and retrieved with forceps. The working cannula was rotated with the open bevel facing away from the axilla of the spinal cord and exiting nerve root, retracting it gently medially to expose the disc. Endoscopic forceps and a Kerrison rongeur were used to retrieve the prolapsed disc. Radiofrequency was often used to help in hemostasis and the gentle release of adhesions of the neural elements to disc to aid in the retrieval of the disc. Uncovertebral hypertrophy was removed with a cutter. After decompression, we performed a final check of the neural elements to confirm the presence of freely pulsating neural elements under irrigation and full decompression. Finally, the skin was closed in layers with a drain inserted. Statistical Analysis The clinical data were analyzed using SPSS, version 18, statistical analysis software (IBM Corp, Armonk, New York, USA). Continuous variables are presented as the mean standard deviation. The paired t test was used to compare the pre- and postoperative CT scan results for the sagittal area, craniocaudal length, and ventrodorsal length and 3D reconstructed posterior decompression area. Clinically, the VAS and ODI were measured preoperatively, 1 week and 3 months postoperatively, and at the final follow-up examination. In addition, the MacNab criteria were used at the final follow-up to evaluate the patients’ pain. A P value of <0.05 was considered statistically significant. RESULTS Baseline Demographics From January 2017 to December 2019, PPPV PECF surgery was performed in 30 patients at 36 levels. Of the 30 patients, 24 had undergone single-level surgery and 6 had undergone 2-level surgery. The mean follow-up period after PPPV PECF was 13.7 6.4 months. The mean patient age was 50.7 12.3 years. Overall, the most common level of cervical radiculopathy was C5-C6 (43.4%), followed by C6-C7 (36.2%). Of the 36 levels treated by PPPV PECF, 18 were at C5-C6, 10 were at C6-C7, 4 at C4-C5, 1 at C3-C4, and 3 at C7-T1. A male predominance was found, with 77.2% men. Clinical Outcomes Postoperatively, PPPV PECF group had not experienced any complications, recurrence, and revision surgery (Table 1 and Figure 5). The PPPV PECF group also showed significant improvement in the VAS scores. The mean standard deviation VAS scores at the preoperative, 1-week postoperative, 3-month postoperative, and final follow-up evaluations were 7.6 1.25, 2.97 0.72, 2.07 0.64, and 1.67 0.80, respectively (P < 0.05). The ODI also showed corresponding statistically significant improvement. The
Figure 1. Measurements performed on pre- and postoperative day 1 computed tomography (CT) sagittal and 3-dimensional CT posterior coronal views. (A) Preoperative sagittal foraminal area measurement. (B) Postoperative sagittal foraminal area measurement. (C) Preoperative ventrodorsal dimension (red double-headed arrow) and cranial caudal dimension (blue double-headed arrow). (D) Postoperative ventrodorsal dimension (red double-headed arrow) and cranial caudal dimension (blue double-headed arrow). (E) On the preoperative 3-dimensional computed tomography scan of the posterior coronal view area, we measured the baseline as 0 mm2 for standardization. (F) Postoperative 3-dimensional computed tomography scan of the posterior coronal view area measurement.
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ENDOSCOPIC SPINE SURGERY SPECIAL SECTION HYEUN SUNG KIM ET AL.
SAFE ROUTE FOR CERVICAL APPROACH
PECF (Table 2 and Figures 1 and 6). The radiological outcomes showed a statistically significant increase in the decompression dimension postoperatively compared with preoperatively on the CT scan after PPPV PECF. The difference in the mean standard deviation in the sagittal foraminal area, craniocaudal length, and ventrodorsal length had decreased: 60.1 23.1 mm2, 4.0 1.54 mm, and 4.0 1.97 mm, respectively. The 3D-CT scan reconstruction of the decompression area had increased 996 266 mm2 (P < 0.05). No patient who had undergone PPPV PECF had developed a pedicle fracture. An illustrative example of PPPV PECF is shown in Figure 6. DISCUSSION
Figure 2. Intraoperative fluoroscopy images showing docking position for partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. Anteroposterior view showing docking on the V point, which was marked by the intersection of the intervertebral disc space and medial to the pedicle of the caudal lamina of the vertebra. In this case, for C4-C5, the intersection would be the C4-C5 intervertebral disc and medial half of the C5 pedicle.
mean standard deviation ODI at the preoperative, 1-week postoperative, 3-month postoperative, and final follow-up evaluations were 73.9 7.83, 28.1 4.33, 23.3 3.04, and 21.5 3.81, respectively (P < 0.05). The MacNab criteria showed that 100% of the patients had experienced good and excellent pain relief, with 14 patients reporting good and 16 patients excellent scores. Radiological Outcomes The pre- and postoperative radiographs showed no instability of the cervical spinal segment in all 30 patients who had undergone PPPV
Figure 3. Drawings showing the key steps in partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. (A) Docking on the left C4-C5 V point. (B) Endoscopic cervical foraminotomy performed by drilling the left C4 medial laminofacet junction to expose the facet joint. (C) Endoscopic decompression of the superior medial portion of the C5 laminofacet junction after completion of decompression of the C4-C5 medial portion of the laminofacet junction. The C5 nerve root was
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Conventional posterior cervical foraminotomy is a motionpreserving procedure with the aim of removing the prolapsed soft intervertebral disc and decompressing the foraminal stenosis causing cervical radiculopathy. The procedure is indicated for cervical disc herniation and neuroforaminal pathology with radicular symptoms when two thirds of the soft disc is lateral to the thecal sac of cervical spinal cord and osseous and bony compression does not involve the median or paramedian region. Conventional posterior cervical foraminotomy is contraindicated for patients with pure axial neck pain and those with cervical instability. The relative contraindications include central disc and calcified disc.19,20 One of the most common postoperative morbidities is the occurrence of neck pain after posterior cervical surgery.12,21 Preservation of the cervical soft tissue and ligamentous structures is key to preventing postoperative instability and axial neck pain. Posterior endoscopic cervical discectomy and foraminotomy aims to preserve the posterior structures and achieve goals similar to those for conventional posterior cervical foraminotomy.18 Several investigators were able to achieve good outcomes without implant- and approachrelated complications.6,22 Surgical failure has been a concern after posterior cervical foraminotomy. The factors associated with an increased risk of failure included spondylosis, residual medial disc protrusion, and persistent radicular pain owing to insufficient decompression.12
exposed together with the pedicle, which was closely related inferior to the C5 nerve root. (D) Endoscopic (medial pediculotomy), 3- to 5-mm deep to create a subneural working epidural space. (E) Minimal retraction of the exit C5 nerve root was required owing to creation of the subneural epidural working space. The disc was exposed and retrieved using endoscopic forceps.
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SAFE ROUTE FOR CERVICAL APPROACH
Figure 4. Endoscopic images of various steps of partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. (A) Docking and soft tissue dissection exposing the V point of the laminofacet junction, which was the landmark for drilling for the partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. Use of an intraoperative fluoroscopic view after defining the V point would help to avoid performing surgery at the wrong level. (B) After endoscopic drilling to complete cervical foraminotomy, the inferior and medial aspects of the left C5 nerve root (axilla) was exposed, and the pedicle
To prevent failure decompression as wide as possible is often required. However, if more than one half of the cervical facet joint has been sacrificed during decompression, instability can result. In a study by Raynor et al,23 they demonstrated that 70%facetectomy specimens had failed by fracture at 159 lb; however, none of the 50%-facetectomy specimens had failed at 208 lb. Hence, preservation of as much of the facet as possible within the limits of sufficient decompression is key to preserving the stability of cervical spinal column. Because the endoscope lens
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was located intimately with the axilla of the C5 exit nerve root. Endoscopically, the medial superior part of the pedicle (medial pediculotomy) and the lateral superior part of the corpus of caudal vertebra helped to create a subneural epidural working space to expose the C4-C5 intervertebral disc space. (C) Additional drilling and decompression was used to expose the prolapsed intervertebral disc at C4-C5 disc space under the axilla of the C5 exit nerve root. (D) Retrieval of the prolapsed intervertebral disc using endoscopic forceps. After removal of the prolapsed disc, the pulsating exit nerve root and dura of spinal cord under irrigation fluid were observed.
was at the distal tip of a long and slim endoscope, we were able to perform partial pediculotomy and vertebrotomy without the need to drill more of the facet joint. Thus, instead of creating a wider window dorsal to the nerve root, we were able to achieve wider all-round foraminal decompression by creating a space ventral to the nerve root by drilling 3 to 5 mm of the pedicle and corpus adjacent to nerve root and spinal cord for decompression. In our series, PPPV PECF achieved good clinical and radiological outcomes. PPPV PECF resulted in no neurologically related
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ENDOSCOPIC SPINE SURGERY SPECIAL SECTION HYEUN SUNG KIM ET AL.
SAFE ROUTE FOR CERVICAL APPROACH
Table 1. Pre- and Postoperative VAS Scores and ODI Outcome
Difference
P Value
VAS score
0.000
Pre- versus 1 wk postoperatively
4.633 1.542
Pre- versus 3-mo postoperatively
5.533 1.502
Preoperatively versus final follow-up
5.933 1.780
3D reconstruction of posterior coronal area 0.000
45.800 8.950
Pre- versus 3-mo postoperatively
50.667 8.934
Preoperatively versus final follow-up
52.400 10.324
complications such as C5 palsy and weakness, which have occurred in an average of 7.8% of patients after conventional posterior cervical surgery.24 We hypothesized that drilling 3 to 5 mm of the pedicle would create a space ventral to the spinal cord and exiting nerve root that would be efficient in decompression of the uncal hypertrophic bone and assessing lateral disc herniation without the need for neural retraction (Figure 7). Overall, the creation of a greater ventral subneural space allowed for sufficient
VAS 7.6
7 6 5 4
2.97
3
2.07
2
1.67
1 0
Pre
Post 1 week
Post 3 mon
Post Final
ODI 80
73.93
70 60 50 40
28.13
30
23.27
21.53
Post 3 mon
Post Final
20 10 0
Pre
Post 1 week
Figure 5. Graphs showing visual analog scale (VAS) scores and Oswestry disability index (ODI) after partial pediculotomy and partial vertebrotomy for posterior endoscopic cervical foraminotomy with statistically and clinically significant improvement in both VAS scores and ODI.
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Difference 60.057 23.014 996.029 266.070
Craniocaudal length
4.01771 1.54184
Ventrodorsal length
4.01412 1.97476
Data presented as mean standard deviation. 3D, 3-dimensional.
Data presented as mean standard deviation. ODI, Oswestry disability index; VAS, visual analog scale.
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Radiological Parameter: Preoperative versus Postoperative Sagittal foraminal area
ODI Pre- versus 1 wk postoperatively
Table 2. Radiological Parameters Showing Bone Removal Amount
decompression with less neural retraction required, explaining the lower rate of expected neurological complications. Our radiological parameters showed statistically significant enlargement of the laminofacet junction. More importantly, ventral decompression through the pedicle and corpus of the caudal vertebra led, overall, to more satisfactory decompression without compromising the stability of the cervical spine. All patients in PPPV PECF group had improved neck pain, VAS scores, ODI, and MacNab scores. No clinically significant instability occurred despite drilling of the pedicle and corpus of the caudal vertebra. Our findings are supported by those from another study by Xiao et al.25 They reported significantly fewer complications in their partial pediculectomy group, with better VAS scores and MacNab scores, a lower analgesic dosage, and shorter postoperative stays, although no radiological data had been collected in their study. The main differences between our technique and that of conventional posterior endoscopic cervical foraminotomy and discectomy were as follows. First, an additional subneural space was created using partial pediculotomy and partial vertebrotomy. Second, we used endoscopic drilling to perform most of the decompression rather than using an endoscopic Kerrison rongeur. Finally, no neural retraction was performed on the spinal cord, although we were able to reach further into the middle portion of the intervertebral disc using partial vertebrotomy and a 30 endoscope for vision. We believe PPPV PECF has several advantages. First, using the conventional posterior endoscopic cervical foraminotomy and discectomy technique, two thirds of the bulk disc must be lateral to the thecal sac to ensure safety during decompression. In contrast, using PPPV PECF, we were able to include more patients in whom the bulk of the herniated disc was located closer to the central location of the intervertebral disc with one half of the bulk of the disc, rather than two thirds of the disc, lateral to the thecal sac. Second, the calcified disc could be drilled or cut with the endoscopic cutter to create a subneural working space using partial pediculotomy and partial vertebrotomy. However, such cases are contraindicated for conventional PECF. Finally, no spinal cord retraction and less exiting nerve root retraction was required to decompress the herniated disc, because we had created the subneural ventral space and pushed the disc ventrally and away from the exiting nerve root before retrieving the herniated disc. In comparison, the conventional technique requires retraction of the exiting nerve root to expose and retrieve the herniated disc.
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Figure 6. Images of a 24-year-old man with subacute onset of a left shoulder drop with deltoid and biceps flexion strength of grade 1. He had recovered completely 2 months after left C4-C5 partial pediculotomy and partial vertebrotomy for posterior endoscopic cervical foraminotomy. (A, B) Preoperative magnetic resonance imaging (MRI) studies showing a large prolapsed intervertebral disc in left C4-C5 abutting the exit nerve root of left C5. (C) Preoperative computed tomography scan showing mild uncovertebral joint hypertrophy with narrowing of the left C4-C5 foramen. (D) Postoperative computed tomography scan showing wide posterior
The PPPV PECF technique has disadvantages compared with the conventional endoscopic techniques. First, the PPPV PECF technique requires a steep learning curve because endoscopic drilling must be performed close to the neural structures with the use of a working cannula to protect the neural elements. Second, overresection of the pedicle and vertebra could lead to instability. Thus, one must drill no more than 3 to 5 mm of the combined dimension of the pedicle and corpus. We typically measured the
Figure 7. Diagrams showing the concept of partial pediculotomy and partial vertebrotomy for posterior endoscopic cervical foraminotomy with subneural epidural space creation. Drilling and decompression were performed in the cone shape (blue). Drilling the medial superior part of the pedicle and lateral superior
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cervical foraminotomy with decompression of the left C4-C5 and upper half of the left C5 pedicle, which was drilled to expose the disc space of the left C4-C5. (E, F) Early postoperative MRI studies showing decompression of the left C4-C5 foramen with removal of the prolapsed left C4-C5 disc space. (G, H) MRI studies at 6 months of follow-up showing some reconstitution of the medial laminofacet joint with no recurrence of the left C4-C5 intervertebral disc space. (I) Photograph of the patient at 2 months postoperatively showing improvement of the left shoulder deltoid and biceps flexion strength to grade 5.
amount by the width of a 3.5-mm diamond drill. Both of these disadvantages can be overcome with greater experience. Despite the steep learning curve, our technique has several surgical pearls that could enhance the safety of this approach. First, a proper preoperative plan was created to determine the correct resection extent of the medial superior pedicle and lateral superior corpus required, because not all cases required partial vertebrotomy. We performed partial vertebrotomy for patients in whom
part of the corpus of the caudal vertebra created a subneural epidural space sufficient for the working instruments to access the lateral one third of the intervertebral disc space without significant, if any, neural retraction.
WORLD NEUROSURGERY, https://doi.org/10.1016/j.wneu.2020.10.158
ENDOSCOPIC SPINE SURGERY SPECIAL SECTION HYEUN SUNG KIM ET AL.
SAFE ROUTE FOR CERVICAL APPROACH
one half, rather than two thirds, of the bulk of the herniated disc was medial to the lateral margin of the thecal sac. Without proper planning and technical competence, this technique could be more complex than the conventional endoscopic technique. Second, careful identification of the V point under endoscopic view and confirmation with intraoperative fluoroscopy could prevent surgery at the wrong level surgery. Third, we drilled the cephalad lamina and lateral mass carefully to expose the underlying medial aspect of the facet joint. Fourth, we were careful to not perform drilling lateral to the pedicle, which would have exposed the vertebral artery. Fifth, the exit nerve root was identified as a key landmark before drilling the pedicle and corpus. Sixth, minimal retraction can be performed at the exit nerve root only. As much as possible, no retraction should be performed at the spinal cord level to prevent catastrophic neurological sequelae. If difficulty occurs in removing the disc, additional corpus or pedicle drilling ventrally was performed instead of retracting the spinal cord. Finally, careful hemostasis should be performed before removal of the endoscope. A drain should be inserted because of the bone drilling involved and to drain the irrigation fluid. The present report had some inherent limitations, including that it was a retrospective cohort study and the follow-up period after PPPV PECF was short term, at a mean of 13.7 months. We could not rule out a delayed presentation of cervical instability. Second, because the study was retrospective, an inherent selection bias was present. However, we minimized the selection bias because all cervical prolapsed discs were treated with PPPV PECF, with no open cervical foraminotomy performed during the study period by the same authors. Third, the information bias was minimized because the assessments were performed by orthopedic and neurosurgery spine surgeons with endoscopic experience who had not participated in the direct care of the study population. No comparison arm of conventional endoscopic or open PECF was included. A study including both treatment arms would be beneficial to confirm the hypothesis that PPPV PECF is safer and more effective than these conventional procedures. A CT
REFERENCES 1. Woods BI, Hilibrand AS. Cervical radiculopathy: epidemiology, etiology, diagnosis, and treatment. J Spinal Disord Tech. 2015;28:E251-E259. 2. Iyer S, Kim HJ. Cervical radiculopathy. Curr Rev Musculoskel Med. 2016;9:272-280. 3. Wong JJ, Cote P, Quesnele JJ, Stern PJ, Mior SA. The course and prognostic factors of symptomatic cervical disc herniation with radiculopathy: a systematic review of the literature. Spine J. 2014;14: 1781-1789. 4. Richards O, Choi D, Timothy J. Cervical arthroplasty: the beginning, the middle, the end? Br J Neurosurg. 2012;26:2-6. 5. Epstein NE. A review of complication rates for anterior cervical diskectomy and fusion (ACDF). Surg Neurol Int. 2019;10:100.
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comparison of this technique with the conventional transverse Vpoint posterior endoscopic cervical foraminotomy and discectomy technique would be helpful to evaluate the effect of PPPV PECF on the amount of the remnant facet joint, an important factor to achieving the goal of long-term cervical spine stability. CONCLUSION Use of the uniportal full endoscopic PPPV PECF showed improved radiological and clinical outcomes, providing a safe alternative technique for posterior cervical decompression with a low complication rate. CRediT AUTHORSHIP CONTRIBUTION STATEMENT Hyeun Sung Kim: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Pang Hung Wu: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Yeon Jin Lee: Data curation, Formal analysis. Dae Hwan Kim: Data curation, Formal analysis. Ji Yeon Kim: Data curation, Formal analysis. Jun Hyung Lee: Data curation, Formal analysis. Jun Bok Jeon: Data curation, Formal analysis. Il-Tae Jang: Project administration, Resources, Writing - review & editing. ACKNOWLEDGMENTS Drs. Hyeun Sung Kim and Pang Hung Wu contributed equally and are first co-authors. We would like to acknowledge scientific team members Ms. Jae Eun Park and Mr. Kyeong Rae Kim for providing assistance in acquiring full text articles and managing digital information.
6. Selvanathan SK, Beagrie C, Thomson S, et al. Anterior cervical discectomy and fusion versus posterior cervical foraminotomy in the treatment of brachialgia: the Leeds Spinal Unit experience (2008-2013). Acta Neurochir (Wien). 2015;157: 1595-1600. 7. Lee DG, Park CK, Lee DC. Clinical and radiological results of posterior cervical foraminotomy at two or three levels: a 3-year follow-up. Acta Neurochir (Wien). 2017;159:2369-2377. 8. Papavero L, Kothe R. Minimally invasive posterior cervical foraminotomy for treatment of radiculopathy: an effective, time-tested, and costefficient motion-preservation technique. Oper Orthop Traumatol. 2018;30:36-45. 9. Ye ZY, Kong WJ, Xin ZJ, et al. Clinical observation of posterior percutaneous full-endoscopic cervical foraminotomy as a treatment for osseous foraminal stenosis. World Neurosurg. 2017;106:945-952.
10. Komp M, Oezdemir S, Hahn P, Ruetten S. Fullendoscopic posterior foraminotomy surgery for cervical disc herniations. Oper Orthop Traumatol. 2018;30:13-24. 11. Kim M, Kim HS, Oh SW, et al. Evolution of spinal endoscopic surgery. Neurospine. 2019;16:6-14. 12. Jodicke A, Daentzer D, Kastner S, Asamoto S, Boker DK. Risk factors for outcome and complications of dorsal foraminotomy in cervical disc herniation. Surg Neurol. 2003;60:124-129 [discussion: 129-130]. 13. Haefeli M, Elfering A. Pain assessment. Eur Spine J. 2006;15(suppl 1):S17-S24. 14. Fairbank JC, Pynsent PB. The Oswestry disability index. Spine (Phila Pa 1976). 2000;25:2940-2952 [discussion: 2952].
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15. MacNab I. Negative disc exploration: an analysis of the causes of nerve-root involvement in sixtyeight patients. J Bone Joint Surg Am. 1971;53:891-903. 16. Kim JH, Adsul N, Kim HS, et al. Safety and efficacy of endoscopic posterior cervical discectomy and foraminotomy using three-point plaster traction technique. J Minim Invasive Spine Surg Tech. 2018;3:23-26. 17. Quillo-Olvera J, Lin G-X, Kim J-S. Percutaneous endoscopic cervical discectomy: a technical review. Ann Transl Med. 2018;6:100. 18. Chang JC, Park HK, Choi SK. Posterior cervical inclinatory foraminotomy for spondylotic radiculopathy preliminary. J Korean Neurosurg Soc. 2011;49: 308-313.
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experience with 34 patients. Clin Spine Surg. 2017; 30:E1419-E1425. 21. Kimura A, Shiraishi Y, Inoue H, Endo T, Takeshita K. Predictors of persistent axial neck pain after cervical laminoplasty. Spine (Phila Pa 1976). 2018;43:10-15. 22. Ruetten S, Komp M, Merk H, Godolias G. Fullendoscopic cervical posterior foraminotomy for the operation of lateral disc herniations using 5.9mm endoscopes: a prospective, randomized, controlled study. Spine (Phila Pa 1976). 2008;33: 940-948. 23. Raynor RB, Pugh J, Shapiro I. Cervical facetectomy and its effect on spine strength. J Neurosurg. 1985;63:278-282.
19. Witzmann A, Hejazi N, Krasznai L. Posterior cervical foraminotomy: a follow-up study of 67 surgically treated patients with compressive radiculopathy. Neurosurg Rev. 2000;23:213-217.
24. Pan FM, Wang SJ, Ma B, Wu DS. C5 nerve root palsy after posterior cervical spine surgery. J Orthop Surg (Hong Kong). 2017;25:2309499016684502.
20. Peto I, Scheiwe C, Kogias E, Hubbe U. Minimally invasive posterior cervical foraminotomy: Freiburg
25. Xiao CM, Yu KX, Deng R, et al. Modified K-hole percutaneous endoscopic surgery for cervical
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foraminal stenosis: partial pediculectomy approach. Pain Physician. 2019;22:E407-E416.
A publisher’s error resulted in this article appearing in the wrong issue. The article is reprinted here for the reader’s convenience and for the continuity of the special section. For citation purposes please use the original publication details; World Neurosurgery 140C Pages e273-e282 DOI of original item: http://dx.doi.org/10.1016/j.wneu.2020.05.033 Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Citation: World Neurosurg. (2020). https://doi.org/10.1016/j.wneu.2020.10.158 Journal homepage: www.journals.elsevier.com/worldneurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2020 Elsevier Inc. All rights reserved.
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Reprint of: Safe Route for Cervical Approach: Partial Pediculotomy, Partial Vertebrotomy Approach for Posterior Endoscopic Cervical Foraminotomy and Discectomy Hyeun Sung Kim1, Pang Hung Wu1,2, Yeon Jin Lee1, Dae Hwan Kim1, Ji Yeon Kim1, Jun Hyung Lee1, Jun Bok Jeon1, Il-Tae Jang1
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BACKGROUND: Cervical radiculopathy is a common cervical spine condition. However, a paucity of data is available on the effect of partial pediculotomy and partial vertebrotomy (PPPV) for posterior endoscopic cervical foraminotomy (PECF) to treat cervical radiculopathy. We investigated the radiological and clinical outcomes of this approach.
increase in decompression in the foramen area for all CTmeasured parameters compared with the mean preoperative values: 1) the sagittal area increased 60.1 23.1 mm2; 2) the craniocaudal length increased 4.0 1.54 mm; and 3) the ventrodorsal length increased 4.0 1.97 mm; Also, the 3-dimensional CT scan reconstruction decompression area had increased 996 266 mm2 (P < 0.05).
METHODS: We performed a retrospective evaluation of 30 patients with cervical radiculopathy who had undergone PPPV PECF. Pre- and postoperative radiographs were performed to evaluate for stability, and computed tomography (CT) was used to evaluate the foraminal dimensions and area in the sagittal view. Three-dimensional reconstruction of the area of decompression was also performed. The clinical outcomes were evaluated using the visual analog scale, Oswestry disability index, and the MacNab criteria.
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RESULTS: No complications or recurrence developed in our PPPV PECF cohort during the study period. At the preoperative, 1-week postoperative, 3-month postoperative, and final follow-up examinations, the mean visual analog scale scores and mean Oswestry disability index showed significant improvement (score, 7.6, 3.0, 2.1, and 1.7, respectively; P < 0.05; and score, 73.9, 28.1, 23.3, and 21.5, respectively; P < 0.05). All the patients scored good to excellent using the MacNab criteria. The radiological findings showed that PPPV PECF resulted in a significant
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Key words Cervical decompression - Cervical radiculopathy - Endoscopic spine surgery - Pedicule - Posterior cervical endoscopic foraminotomy - Posterior endoscopic cervical discectomy - Prolapsed intervertebral disc -
Abbreviations and Acronyms CT: Computed tomography MRI: Magnetic resonance imaging ODI: Oswestry disability index PECF: Posterior endoscopic cervical foraminotomy and discectomy
CONCLUSION: PPPV PECF is a safe route for decompression of the cervical spine with good clinical and radiological outcomes.
INTRODUCTION
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ervical radiculopathy is a common cervical spine condition leading to significant disability from nerve root dysfunction.1 Conservative therapy is recommended for 6 weeks for cervical radiculopathy without myelopathy.1,2 The time to recovery has ranged from 2 weeks to 3 years for 83% of patients.3 However, a good proportion of patients will remain symptomatic despite being compliant with conservative treatment.3 Anterior cervical discectomy and fusion and cervical artificial disc replacement has been the reference standard treatment.4 The morbidity attributed to anterior cervical surgery has ranged from 13.2% to 19.3%, with pseudoarthrosis and adjacent segment disease the most common postoperative
PPPV: Partial pediculotomy, partial vertebrotomy approach VAS: Visual analog scale From the 1Spine Surgery Center, Nanoori Gangnam Hospital, Seoul, Republic of Korea; and 2 Department of Orthopaedic Surgery, National University Health System, Jurong Health Campus, Singapore To whom correspondence should be addressed: Hyeun-Sung Kim, M.D., Ph.D. [E-mail: [email protected]] Hyeun Sung Kim and Pang Hung Wu are co-first authors. Citation: World Neurosurg. (2020). https://doi.org/10.1016/j.wneu.2020.10.158 Journal homepage: www.journals.elsevier.com/world-neurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2020 Elsevier Inc. All rights reserved.
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complications.5 Posterior cervical foraminotomy has increased in popularity as an alternative to anterior cervical discectomy and fusion, sparing the issues associated with fusion and surgical instrumentation, with equally good clinical results and the added advantage of motion preservation.6-8 Cervical endoscopic decompression is becoming popular as a soft tissue-conserving minimally invasive technique for cervical foraminal decompression and discectomy for a prolapsed intervertebral disc and foraminal stenosis.9-11 One of the concerns with endoscopic cervical foraminotomy and discectomy has been the neurological complications associated with the spinal cord and exiting nerve root retraction, leading to significant residual radicular pain and, on rare occasions, paralysis. Although incomplete decompression is a leading cause of residual radicular pain, the risk must be weighed against overly aggressive resection of the facet, which can lead to local failure of the facet joint.12 The safety of the approach to the cervical intervertebral disc is of paramount importance. We hypothesized that drilling the medial one third of the pedicle and corpus ventral to the spinal cord and exiting nerve root by 3 to 5 mm would create space for efficient discectomy and uncus decompression and preserve the stability of the spinal segment. Creating a space ventral to the neural elements helps to prevent the complications resulting from neural retraction using the endoscopic working channel. We performed the partial pediculotomy, partial vertebrotomy approach (PPPV) for posterior cervical foraminotomy and discectomy (PECF) to test our hypothesis. METHODS Patient Demographics The institutional review board of Nanoori Hospital (Seoul, Republic of Korea) approved the present retrospective comparison study. All included patients provided written informed consent. From January 2017 to December 2019, 30 patients had undergone uniportal PPPV PECF at 36 cervical intervertebral disc levels at our institute. The clinical presentation was intractable cervical radiculopathy, not relieved by >6 weeks of conservative treatment; motor and/or sensory impairment with cervical neuroforaminal nerve root compression resulting from a soft herniated cervical intervertebral disc or cervical foraminal stenosis secondary to a degenerative disc; and uncovertebral joint hypertrophy and osteophytes in a facet joint. The patients were required to have disc material and uncal hypertrophy present at the lateral aspect of the cervical intervertebral disc with one half of the bulk of disc material lateral to the thecal sac on the axial view of the magnetic resonance imaging (MRI) scan. We excluded patients with contraindications for posterior cervical spine decompression. The contraindications included a calcified central disc, instability of the cervical spine, significant cervical kyphosis of >10 , advanced cervical myelopathy, and predominant axial neck pain without radiculopathy. Outcomes Measures The baseline demographic variables recorded included age, sex, diagnosis, number of decompression levels, and levels of decompression. The clinical outcome measures included the visual analog scale (VAS) scores13 and Oswestry disability index
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(ODI).14 The VAS and ODI were completed preoperatively, at 1 week and 3 months postoperatively, and at the final follow-up evaluation. We also used the MacNab criteria at the final followup to evaluate for pain relief.15 The data were retrieved from the clinical note documentation by 2 experienced Korean spine surgeons (Y.J.L. and D.H.K.) who were not involved in the care of the study patients. Postoperative complications, any recurrence at the same or adjacent levels, reoperations, and neurological deficits were documented. Workstation software (Infinitt, Inc, Seoul, Republic of Korea) was used. The radiological variables were measured by 3 experienced spine surgeons (P.H.W., Y.J.L., D.H.K.) who were not involved in the care of the study subjects. Individual and consensus interpretations were obtained for each variable. Preoperative computed tomography (CT) scans, MRI studies, and plain radiographs were obtained for all patients. Instability was defined as >2 mm of motion at the operative segment or any adjacent segments on cervical dynamic plain radiographs. These patients were excluded from the present study. Comparisons of the MRI and CT data were performed using images obtained preoperatively and on postoperative day 1. These imaging studies were performed as a part of the hospital protocol and were used to assess the cause of cervical radiculopathy, disc position, disc size, and the presence of uncal vertebral hypertrophy and foraminal stenosis. Surgical decompression of these pathologies was also evaluated. We compared the pre- and postoperative midsagittal foraminal area, craniocaudal length, and ventrodorsal length in the first cut of the cephalad vertebral pedicle when scrolling from medially to laterally at the affected level. The posterior coronal view of the area of decompression was measured on the preoperative and 1-day postoperative 3-dimensional (3D) reconstructed CT scan. We ensured the reconstructed CT scan was a direct posterior view in which the cut showed the symmetrical size of the caudal lamina bilaterally. The measurement methods used for the CT parameters are shown in Figure 1. Description of PPPV PECF Technique The patients underwent general anesthesia and were positioned prone on a Wilson frame with shoulder strapped and the neck flexed in a slight, reverse Trendelenburg position using a 3-point plaster traction technique at the head, shoulder, and back without a Mayfield head clamp to increase the interlaminar space of the cervical spine.16 The patient’s face was positioned in a commercial anesthesia pillow foam to support the bony prominence with space created for the eyes, nose, and mouth. The head attachment was tilted down slightly to allow for cervical spine flexion and secured with plaster. The arms were padded and tucked longitudinally next to the patient. The anterior superior iliac spine and knees were padded, and the hips and knees were flexed slightly. Both the shoulders were strapped to pull the shoulders down slightly without pressure on the brachial plexus, with a final strap on the back to reduce the skin fold. We did not use neuromonitoring during any of our PPPV PECF procedures. Skin marking was performed with anteroposterior and lateral cervical fluoroscopic guidance (Figures 2 and 3). We aimed for the intersection of the intervertebral disc space and medial border of facet joint junction on the anteroposterior view
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and at the facet joint of the correct level on the lateral view. This was correlated with the intraoperative view of the “V” point, defined as the junction of confluence of the cephalad and caudal laminal facets, which has a V-shaped configuration.17 A transverse 8-mm incision was made at the V point, and an obturator was inserted and docked, with the tip position confirmed by fluoroscopy. A 30 viewing angle, 7.3-mm outer diameter, and 4.7-mm working channel endoscope (Joimax GmbH, Karlsruhe, Germany) was used for the procedure with continuous normal saline irrigation at a pressure of 25 mm Hg. Hemostasis and soft tissue dissection was performed using a radiofrequency probe (Ellman bipolar radiofrequency electrocoagulator [Elliquence, Baldwin, New York, USA]) and endoscopic forceps. Once the V point had been identified and confirmed on fluoroscopy, the medial aspect of the lateral mass and facet joint was drilled using a long, straight, 3.5-mm diameter, coarse diamond, high-speed drill (Primado High-Speed Drill System [Nakanishi Inc, Surgical Division, Tochigi, Japan) to create a working window (Figure 4). The size of the window varied according to the size of the herniated material and degree of foraminal stenosis. Resection of the cephalad laminofacet was performed first. Typically, 3 to 5 mm in diameter of bone was removed from the lateral inferior aspect of the upper lamina, followed by ~3 mm of the medial inferior portion of the upper facet from the laminaefacet border (the V point).18 We then asked the anesthetist to tilt patient toward the surgeon to allow for resection at the medial superior articular facet of the lower vertebra. Approximately 3 to 5 mm in diameter was resected of the superomedial corner of the medial aspect of the superior articular facet of the caudal vertebra, close to the dorsal aspect of the nerve root, leading toward the proximal portion of the nerve root. We used a 3.5-mm diamond Primado II NSK drill bit (Nakanishi Inc, Surgical Division) for bone removal, with forceps and punches used to collect any loose bone fragments. After posterior foraminotomy had been completed, the exiting nerve root and spinal cord were exposed. We shifted the working cannula to center on the upper medial aspect of the pedicle, and drilled the pedicle 3 to 5-mm deeper than the neural element level to create a subneural working space to provide access to the herniated disc material. Using this method, minimal neural retraction was required during the discectomy. If a more central location of the disc had been noted on the preoperative MRI scan, a partial vertebrotomy approach was added. The lateral aspect of the corpus of the caudal cervical vertebra was drilled after the pedicle had been drilled to create a working space underneath the neural elements in a central location to provide access to the central disc without significant neural retraction. After drilling, a forceps or cutter was used to push the disc material and
osteophytes down to the subneural space created ventral to the neural elements and retrieved with forceps. The working cannula was rotated with the open bevel facing away from the axilla of the spinal cord and exiting nerve root, retracting it gently medially to expose the disc. Endoscopic forceps and a Kerrison rongeur were used to retrieve the prolapsed disc. Radiofrequency was often used to help in hemostasis and the gentle release of adhesions of the neural elements to disc to aid in the retrieval of the disc. Uncovertebral hypertrophy was removed with a cutter. After decompression, we performed a final check of the neural elements to confirm the presence of freely pulsating neural elements under irrigation and full decompression. Finally, the skin was closed in layers with a drain inserted. Statistical Analysis The clinical data were analyzed using SPSS, version 18, statistical analysis software (IBM Corp, Armonk, New York, USA). Continuous variables are presented as the mean standard deviation. The paired t test was used to compare the pre- and postoperative CT scan results for the sagittal area, craniocaudal length, and ventrodorsal length and 3D reconstructed posterior decompression area. Clinically, the VAS and ODI were measured preoperatively, 1 week and 3 months postoperatively, and at the final follow-up examination. In addition, the MacNab criteria were used at the final follow-up to evaluate the patients’ pain. A P value of <0.05 was considered statistically significant. RESULTS Baseline Demographics From January 2017 to December 2019, PPPV PECF surgery was performed in 30 patients at 36 levels. Of the 30 patients, 24 had undergone single-level surgery and 6 had undergone 2-level surgery. The mean follow-up period after PPPV PECF was 13.7 6.4 months. The mean patient age was 50.7 12.3 years. Overall, the most common level of cervical radiculopathy was C5-C6 (43.4%), followed by C6-C7 (36.2%). Of the 36 levels treated by PPPV PECF, 18 were at C5-C6, 10 were at C6-C7, 4 at C4-C5, 1 at C3-C4, and 3 at C7-T1. A male predominance was found, with 77.2% men. Clinical Outcomes Postoperatively, PPPV PECF group had not experienced any complications, recurrence, and revision surgery (Table 1 and Figure 5). The PPPV PECF group also showed significant improvement in the VAS scores. The mean standard deviation VAS scores at the preoperative, 1-week postoperative, 3-month postoperative, and final follow-up evaluations were 7.6 1.25, 2.97 0.72, 2.07 0.64, and 1.67 0.80, respectively (P < 0.05). The ODI also showed corresponding statistically significant improvement. The
Figure 1. Measurements performed on pre- and postoperative day 1 computed tomography (CT) sagittal and 3-dimensional CT posterior coronal views. (A) Preoperative sagittal foraminal area measurement. (B) Postoperative sagittal foraminal area measurement. (C) Preoperative ventrodorsal dimension (red double-headed arrow) and cranial caudal dimension (blue double-headed arrow). (D) Postoperative ventrodorsal dimension (red double-headed arrow) and cranial caudal dimension (blue double-headed arrow). (E) On the preoperative 3-dimensional computed tomography scan of the posterior coronal view area, we measured the baseline as 0 mm2 for standardization. (F) Postoperative 3-dimensional computed tomography scan of the posterior coronal view area measurement.
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PECF (Table 2 and Figures 1 and 6). The radiological outcomes showed a statistically significant increase in the decompression dimension postoperatively compared with preoperatively on the CT scan after PPPV PECF. The difference in the mean standard deviation in the sagittal foraminal area, craniocaudal length, and ventrodorsal length had decreased: 60.1 23.1 mm2, 4.0 1.54 mm, and 4.0 1.97 mm, respectively. The 3D-CT scan reconstruction of the decompression area had increased 996 266 mm2 (P < 0.05). No patient who had undergone PPPV PECF had developed a pedicle fracture. An illustrative example of PPPV PECF is shown in Figure 6. DISCUSSION
Figure 2. Intraoperative fluoroscopy images showing docking position for partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. Anteroposterior view showing docking on the V point, which was marked by the intersection of the intervertebral disc space and medial to the pedicle of the caudal lamina of the vertebra. In this case, for C4-C5, the intersection would be the C4-C5 intervertebral disc and medial half of the C5 pedicle.
mean standard deviation ODI at the preoperative, 1-week postoperative, 3-month postoperative, and final follow-up evaluations were 73.9 7.83, 28.1 4.33, 23.3 3.04, and 21.5 3.81, respectively (P < 0.05). The MacNab criteria showed that 100% of the patients had experienced good and excellent pain relief, with 14 patients reporting good and 16 patients excellent scores. Radiological Outcomes The pre- and postoperative radiographs showed no instability of the cervical spinal segment in all 30 patients who had undergone PPPV
Figure 3. Drawings showing the key steps in partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. (A) Docking on the left C4-C5 V point. (B) Endoscopic cervical foraminotomy performed by drilling the left C4 medial laminofacet junction to expose the facet joint. (C) Endoscopic decompression of the superior medial portion of the C5 laminofacet junction after completion of decompression of the C4-C5 medial portion of the laminofacet junction. The C5 nerve root was
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Conventional posterior cervical foraminotomy is a motionpreserving procedure with the aim of removing the prolapsed soft intervertebral disc and decompressing the foraminal stenosis causing cervical radiculopathy. The procedure is indicated for cervical disc herniation and neuroforaminal pathology with radicular symptoms when two thirds of the soft disc is lateral to the thecal sac of cervical spinal cord and osseous and bony compression does not involve the median or paramedian region. Conventional posterior cervical foraminotomy is contraindicated for patients with pure axial neck pain and those with cervical instability. The relative contraindications include central disc and calcified disc.19,20 One of the most common postoperative morbidities is the occurrence of neck pain after posterior cervical surgery.12,21 Preservation of the cervical soft tissue and ligamentous structures is key to preventing postoperative instability and axial neck pain. Posterior endoscopic cervical discectomy and foraminotomy aims to preserve the posterior structures and achieve goals similar to those for conventional posterior cervical foraminotomy.18 Several investigators were able to achieve good outcomes without implant- and approachrelated complications.6,22 Surgical failure has been a concern after posterior cervical foraminotomy. The factors associated with an increased risk of failure included spondylosis, residual medial disc protrusion, and persistent radicular pain owing to insufficient decompression.12
exposed together with the pedicle, which was closely related inferior to the C5 nerve root. (D) Endoscopic (medial pediculotomy), 3- to 5-mm deep to create a subneural working epidural space. (E) Minimal retraction of the exit C5 nerve root was required owing to creation of the subneural epidural working space. The disc was exposed and retrieved using endoscopic forceps.
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Figure 4. Endoscopic images of various steps of partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. (A) Docking and soft tissue dissection exposing the V point of the laminofacet junction, which was the landmark for drilling for the partial pediculotomy and partial vertebrotomy approach for posterior endoscopic cervical foraminotomy. Use of an intraoperative fluoroscopic view after defining the V point would help to avoid performing surgery at the wrong level. (B) After endoscopic drilling to complete cervical foraminotomy, the inferior and medial aspects of the left C5 nerve root (axilla) was exposed, and the pedicle
To prevent failure decompression as wide as possible is often required. However, if more than one half of the cervical facet joint has been sacrificed during decompression, instability can result. In a study by Raynor et al,23 they demonstrated that 70%facetectomy specimens had failed by fracture at 159 lb; however, none of the 50%-facetectomy specimens had failed at 208 lb. Hence, preservation of as much of the facet as possible within the limits of sufficient decompression is key to preserving the stability of cervical spinal column. Because the endoscope lens
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was located intimately with the axilla of the C5 exit nerve root. Endoscopically, the medial superior part of the pedicle (medial pediculotomy) and the lateral superior part of the corpus of caudal vertebra helped to create a subneural epidural working space to expose the C4-C5 intervertebral disc space. (C) Additional drilling and decompression was used to expose the prolapsed intervertebral disc at C4-C5 disc space under the axilla of the C5 exit nerve root. (D) Retrieval of the prolapsed intervertebral disc using endoscopic forceps. After removal of the prolapsed disc, the pulsating exit nerve root and dura of spinal cord under irrigation fluid were observed.
was at the distal tip of a long and slim endoscope, we were able to perform partial pediculotomy and vertebrotomy without the need to drill more of the facet joint. Thus, instead of creating a wider window dorsal to the nerve root, we were able to achieve wider all-round foraminal decompression by creating a space ventral to the nerve root by drilling 3 to 5 mm of the pedicle and corpus adjacent to nerve root and spinal cord for decompression. In our series, PPPV PECF achieved good clinical and radiological outcomes. PPPV PECF resulted in no neurologically related
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Table 1. Pre- and Postoperative VAS Scores and ODI Outcome
Difference
P Value
VAS score
0.000
Pre- versus 1 wk postoperatively
4.633 1.542
Pre- versus 3-mo postoperatively
5.533 1.502
Preoperatively versus final follow-up
5.933 1.780
3D reconstruction of posterior coronal area 0.000
45.800 8.950
Pre- versus 3-mo postoperatively
50.667 8.934
Preoperatively versus final follow-up
52.400 10.324
complications such as C5 palsy and weakness, which have occurred in an average of 7.8% of patients after conventional posterior cervical surgery.24 We hypothesized that drilling 3 to 5 mm of the pedicle would create a space ventral to the spinal cord and exiting nerve root that would be efficient in decompression of the uncal hypertrophic bone and assessing lateral disc herniation without the need for neural retraction (Figure 7). Overall, the creation of a greater ventral subneural space allowed for sufficient
VAS 7.6
7 6 5 4
2.97
3
2.07
2
1.67
1 0
Pre
Post 1 week
Post 3 mon
Post Final
ODI 80
73.93
70 60 50 40
28.13
30
23.27
21.53
Post 3 mon
Post Final
20 10 0
Pre
Post 1 week
Figure 5. Graphs showing visual analog scale (VAS) scores and Oswestry disability index (ODI) after partial pediculotomy and partial vertebrotomy for posterior endoscopic cervical foraminotomy with statistically and clinically significant improvement in both VAS scores and ODI.
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Difference 60.057 23.014 996.029 266.070
Craniocaudal length
4.01771 1.54184
Ventrodorsal length
4.01412 1.97476
Data presented as mean standard deviation. 3D, 3-dimensional.
Data presented as mean standard deviation. ODI, Oswestry disability index; VAS, visual analog scale.
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Radiological Parameter: Preoperative versus Postoperative Sagittal foraminal area
ODI Pre- versus 1 wk postoperatively
Table 2. Radiological Parameters Showing Bone Removal Amount
decompression with less neural retraction required, explaining the lower rate of expected neurological complications. Our radiological parameters showed statistically significant enlargement of the laminofacet junction. More importantly, ventral decompression through the pedicle and corpus of the caudal vertebra led, overall, to more satisfactory decompression without compromising the stability of the cervical spine. All patients in PPPV PECF group had improved neck pain, VAS scores, ODI, and MacNab scores. No clinically significant instability occurred despite drilling of the pedicle and corpus of the caudal vertebra. Our findings are supported by those from another study by Xiao et al.25 They reported significantly fewer complications in their partial pediculectomy group, with better VAS scores and MacNab scores, a lower analgesic dosage, and shorter postoperative stays, although no radiological data had been collected in their study. The main differences between our technique and that of conventional posterior endoscopic cervical foraminotomy and discectomy were as follows. First, an additional subneural space was created using partial pediculotomy and partial vertebrotomy. Second, we used endoscopic drilling to perform most of the decompression rather than using an endoscopic Kerrison rongeur. Finally, no neural retraction was performed on the spinal cord, although we were able to reach further into the middle portion of the intervertebral disc using partial vertebrotomy and a 30 endoscope for vision. We believe PPPV PECF has several advantages. First, using the conventional posterior endoscopic cervical foraminotomy and discectomy technique, two thirds of the bulk disc must be lateral to the thecal sac to ensure safety during decompression. In contrast, using PPPV PECF, we were able to include more patients in whom the bulk of the herniated disc was located closer to the central location of the intervertebral disc with one half of the bulk of the disc, rather than two thirds of the disc, lateral to the thecal sac. Second, the calcified disc could be drilled or cut with the endoscopic cutter to create a subneural working space using partial pediculotomy and partial vertebrotomy. However, such cases are contraindicated for conventional PECF. Finally, no spinal cord retraction and less exiting nerve root retraction was required to decompress the herniated disc, because we had created the subneural ventral space and pushed the disc ventrally and away from the exiting nerve root before retrieving the herniated disc. In comparison, the conventional technique requires retraction of the exiting nerve root to expose and retrieve the herniated disc.
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ENDOSCOPIC SPINE SURGERY SPECIAL SECTION HYEUN SUNG KIM ET AL.
SAFE ROUTE FOR CERVICAL APPROACH
Figure 6. Images of a 24-year-old man with subacute onset of a left shoulder drop with deltoid and biceps flexion strength of grade 1. He had recovered completely 2 months after left C4-C5 partial pediculotomy and partial vertebrotomy for posterior endoscopic cervical foraminotomy. (A, B) Preoperative magnetic resonance imaging (MRI) studies showing a large prolapsed intervertebral disc in left C4-C5 abutting the exit nerve root of left C5. (C) Preoperative computed tomography scan showing mild uncovertebral joint hypertrophy with narrowing of the left C4-C5 foramen. (D) Postoperative computed tomography scan showing wide posterior
The PPPV PECF technique has disadvantages compared with the conventional endoscopic techniques. First, the PPPV PECF technique requires a steep learning curve because endoscopic drilling must be performed close to the neural structures with the use of a working cannula to protect the neural elements. Second, overresection of the pedicle and vertebra could lead to instability. Thus, one must drill no more than 3 to 5 mm of the combined dimension of the pedicle and corpus. We typically measured the
Figure 7. Diagrams showing the concept of partial pediculotomy and partial vertebrotomy for posterior endoscopic cervical foraminotomy with subneural epidural space creation. Drilling and decompression were performed in the cone shape (blue). Drilling the medial superior part of the pedicle and lateral superior
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cervical foraminotomy with decompression of the left C4-C5 and upper half of the left C5 pedicle, which was drilled to expose the disc space of the left C4-C5. (E, F) Early postoperative MRI studies showing decompression of the left C4-C5 foramen with removal of the prolapsed left C4-C5 disc space. (G, H) MRI studies at 6 months of follow-up showing some reconstitution of the medial laminofacet joint with no recurrence of the left C4-C5 intervertebral disc space. (I) Photograph of the patient at 2 months postoperatively showing improvement of the left shoulder deltoid and biceps flexion strength to grade 5.
amount by the width of a 3.5-mm diamond drill. Both of these disadvantages can be overcome with greater experience. Despite the steep learning curve, our technique has several surgical pearls that could enhance the safety of this approach. First, a proper preoperative plan was created to determine the correct resection extent of the medial superior pedicle and lateral superior corpus required, because not all cases required partial vertebrotomy. We performed partial vertebrotomy for patients in whom
part of the corpus of the caudal vertebra created a subneural epidural space sufficient for the working instruments to access the lateral one third of the intervertebral disc space without significant, if any, neural retraction.
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ENDOSCOPIC SPINE SURGERY SPECIAL SECTION HYEUN SUNG KIM ET AL.
SAFE ROUTE FOR CERVICAL APPROACH
one half, rather than two thirds, of the bulk of the herniated disc was medial to the lateral margin of the thecal sac. Without proper planning and technical competence, this technique could be more complex than the conventional endoscopic technique. Second, careful identification of the V point under endoscopic view and confirmation with intraoperative fluoroscopy could prevent surgery at the wrong level surgery. Third, we drilled the cephalad lamina and lateral mass carefully to expose the underlying medial aspect of the facet joint. Fourth, we were careful to not perform drilling lateral to the pedicle, which would have exposed the vertebral artery. Fifth, the exit nerve root was identified as a key landmark before drilling the pedicle and corpus. Sixth, minimal retraction can be performed at the exit nerve root only. As much as possible, no retraction should be performed at the spinal cord level to prevent catastrophic neurological sequelae. If difficulty occurs in removing the disc, additional corpus or pedicle drilling ventrally was performed instead of retracting the spinal cord. Finally, careful hemostasis should be performed before removal of the endoscope. A drain should be inserted because of the bone drilling involved and to drain the irrigation fluid. The present report had some inherent limitations, including that it was a retrospective cohort study and the follow-up period after PPPV PECF was short term, at a mean of 13.7 months. We could not rule out a delayed presentation of cervical instability. Second, because the study was retrospective, an inherent selection bias was present. However, we minimized the selection bias because all cervical prolapsed discs were treated with PPPV PECF, with no open cervical foraminotomy performed during the study period by the same authors. Third, the information bias was minimized because the assessments were performed by orthopedic and neurosurgery spine surgeons with endoscopic experience who had not participated in the direct care of the study population. No comparison arm of conventional endoscopic or open PECF was included. A study including both treatment arms would be beneficial to confirm the hypothesis that PPPV PECF is safer and more effective than these conventional procedures. A CT
REFERENCES 1. Woods BI, Hilibrand AS. Cervical radiculopathy: epidemiology, etiology, diagnosis, and treatment. J Spinal Disord Tech. 2015;28:E251-E259. 2. Iyer S, Kim HJ. Cervical radiculopathy. Curr Rev Musculoskel Med. 2016;9:272-280. 3. Wong JJ, Cote P, Quesnele JJ, Stern PJ, Mior SA. The course and prognostic factors of symptomatic cervical disc herniation with radiculopathy: a systematic review of the literature. Spine J. 2014;14: 1781-1789. 4. Richards O, Choi D, Timothy J. Cervical arthroplasty: the beginning, the middle, the end? Br J Neurosurg. 2012;26:2-6. 5. Epstein NE. A review of complication rates for anterior cervical diskectomy and fusion (ACDF). Surg Neurol Int. 2019;10:100.
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comparison of this technique with the conventional transverse Vpoint posterior endoscopic cervical foraminotomy and discectomy technique would be helpful to evaluate the effect of PPPV PECF on the amount of the remnant facet joint, an important factor to achieving the goal of long-term cervical spine stability. CONCLUSION Use of the uniportal full endoscopic PPPV PECF showed improved radiological and clinical outcomes, providing a safe alternative technique for posterior cervical decompression with a low complication rate. CRediT AUTHORSHIP CONTRIBUTION STATEMENT Hyeun Sung Kim: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Pang Hung Wu: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing - original draft, Writing - review & editing. Yeon Jin Lee: Data curation, Formal analysis. Dae Hwan Kim: Data curation, Formal analysis. Ji Yeon Kim: Data curation, Formal analysis. Jun Hyung Lee: Data curation, Formal analysis. Jun Bok Jeon: Data curation, Formal analysis. Il-Tae Jang: Project administration, Resources, Writing - review & editing. ACKNOWLEDGMENTS Drs. Hyeun Sung Kim and Pang Hung Wu contributed equally and are first co-authors. We would like to acknowledge scientific team members Ms. Jae Eun Park and Mr. Kyeong Rae Kim for providing assistance in acquiring full text articles and managing digital information.
6. Selvanathan SK, Beagrie C, Thomson S, et al. Anterior cervical discectomy and fusion versus posterior cervical foraminotomy in the treatment of brachialgia: the Leeds Spinal Unit experience (2008-2013). Acta Neurochir (Wien). 2015;157: 1595-1600. 7. Lee DG, Park CK, Lee DC. Clinical and radiological results of posterior cervical foraminotomy at two or three levels: a 3-year follow-up. Acta Neurochir (Wien). 2017;159:2369-2377. 8. Papavero L, Kothe R. Minimally invasive posterior cervical foraminotomy for treatment of radiculopathy: an effective, time-tested, and costefficient motion-preservation technique. Oper Orthop Traumatol. 2018;30:36-45. 9. Ye ZY, Kong WJ, Xin ZJ, et al. Clinical observation of posterior percutaneous full-endoscopic cervical foraminotomy as a treatment for osseous foraminal stenosis. World Neurosurg. 2017;106:945-952.
10. Komp M, Oezdemir S, Hahn P, Ruetten S. Fullendoscopic posterior foraminotomy surgery for cervical disc herniations. Oper Orthop Traumatol. 2018;30:13-24. 11. Kim M, Kim HS, Oh SW, et al. Evolution of spinal endoscopic surgery. Neurospine. 2019;16:6-14. 12. Jodicke A, Daentzer D, Kastner S, Asamoto S, Boker DK. Risk factors for outcome and complications of dorsal foraminotomy in cervical disc herniation. Surg Neurol. 2003;60:124-129 [discussion: 129-130]. 13. Haefeli M, Elfering A. Pain assessment. Eur Spine J. 2006;15(suppl 1):S17-S24. 14. Fairbank JC, Pynsent PB. The Oswestry disability index. Spine (Phila Pa 1976). 2000;25:2940-2952 [discussion: 2952].
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15. MacNab I. Negative disc exploration: an analysis of the causes of nerve-root involvement in sixtyeight patients. J Bone Joint Surg Am. 1971;53:891-903. 16. Kim JH, Adsul N, Kim HS, et al. Safety and efficacy of endoscopic posterior cervical discectomy and foraminotomy using three-point plaster traction technique. J Minim Invasive Spine Surg Tech. 2018;3:23-26. 17. Quillo-Olvera J, Lin G-X, Kim J-S. Percutaneous endoscopic cervical discectomy: a technical review. Ann Transl Med. 2018;6:100. 18. Chang JC, Park HK, Choi SK. Posterior cervical inclinatory foraminotomy for spondylotic radiculopathy preliminary. J Korean Neurosurg Soc. 2011;49: 308-313.
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experience with 34 patients. Clin Spine Surg. 2017; 30:E1419-E1425. 21. Kimura A, Shiraishi Y, Inoue H, Endo T, Takeshita K. Predictors of persistent axial neck pain after cervical laminoplasty. Spine (Phila Pa 1976). 2018;43:10-15. 22. Ruetten S, Komp M, Merk H, Godolias G. Fullendoscopic cervical posterior foraminotomy for the operation of lateral disc herniations using 5.9mm endoscopes: a prospective, randomized, controlled study. Spine (Phila Pa 1976). 2008;33: 940-948. 23. Raynor RB, Pugh J, Shapiro I. Cervical facetectomy and its effect on spine strength. J Neurosurg. 1985;63:278-282.
19. Witzmann A, Hejazi N, Krasznai L. Posterior cervical foraminotomy: a follow-up study of 67 surgically treated patients with compressive radiculopathy. Neurosurg Rev. 2000;23:213-217.
24. Pan FM, Wang SJ, Ma B, Wu DS. C5 nerve root palsy after posterior cervical spine surgery. J Orthop Surg (Hong Kong). 2017;25:2309499016684502.
20. Peto I, Scheiwe C, Kogias E, Hubbe U. Minimally invasive posterior cervical foraminotomy: Freiburg
25. Xiao CM, Yu KX, Deng R, et al. Modified K-hole percutaneous endoscopic surgery for cervical
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foraminal stenosis: partial pediculectomy approach. Pain Physician. 2019;22:E407-E416.
A publisher’s error resulted in this article appearing in the wrong issue. The article is reprinted here for the reader’s convenience and for the continuity of the special section. For citation purposes please use the original publication details; World Neurosurgery 140C Pages e273-e282 DOI of original item: http://dx.doi.org/10.1016/j.wneu.2020.05.033 Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Citation: World Neurosurg. (2020). https://doi.org/10.1016/j.wneu.2020.10.158 Journal homepage: www.journals.elsevier.com/worldneurosurgery Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2020 Elsevier Inc. All rights reserved.
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