Instructional Course Lecture
Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery Abstract Jesse E. Bible, MD, MHS Jeffrey A. Rihn, MD Moe R. Lim, MD Darrel S. Brodke, MD Joon Y. Lee, MD
The incidence of intraoperative complications in cervical spine surgery is low. However, when they do occur, such complications have the potential for causing considerable morbidity and mortality. Spine surgeons should be familiar with methods of minimizing such complications. Furthermore, if they do occur, surgeons must be prepared to immediately treat each potential complication to reduce any associated morbidity.
C From the Department of Orthopaedics and Rehabilitation, Penn State Milton S. Hershey Medical Center, Hershey, PA (Dr. Bible), The Rothman Institute, Thomas Jefferson University, Philadelphia, PA (Dr. Rihn), the Department of Orthopaedics, University of North Carolina at Chapel Hill, Chapel Hill, NC (Dr. Lim), the Department of Orthopaedics, University of Utah, Salt Lake City, UT (Dr. Brodke) and the Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA (Dr. Lee). This article, as well as other lectures presented at the Academy’s Annual Meeting, will be available in March 2016 in Instructional Course Lectures, Volume 65. J Am Acad Orthop Surg 2015;23: e81-e90 http://dx.doi.org/10.5435/ JAAOS-D-14-00446 Copyright 2015 by the American Academy of Orthopaedic Surgeons.
omplications related to cervical spine surgery can range in incidence and associated morbidity and mortality. Complications with a delayed onset, including dysphagia, nonunion, and adjacent-segment disease, are more common than those of immediate onset. The former types of complications are associated with reduced relative morbidity and often can be treated nonsurgically. Conversely, intraoperative complications occur much less often but are associated with more significant morbidity and mortality. Given that intraoperative complications are inevitable despite the use of the best surgical techniques, surgeons should be familiar with the risk factors, methods of prevention, and immediate treatment options for such complications, with the goal of mitigating any associated morbidity and mortality. Here, we discuss intraoperative vertebral artery, neurologic, and esophageal injuries, as well as cerebrospinal fluid (CSF) leaks and complications of instrumentation related to surgery on the cervical spine.
Vertebral Artery Injury Incidence Vertebral artery injury is a very rare event, but it can be associated with considerable morbidity and mortality. In one report, the incidence of injury during anterior cervical spine surgeries was 0.3%.1 In a survey of members of the Cervical Spine Research Society, the overall incidence of vertebral artery injury in the cervical spine was 0.07% (111 of 163,324 surgeries).2 Instrumentation of the upper cervical spine (32%), anterior corpectomy (23%), and posterior exposure (12%) was the most common surgical factor associated with injury.
Prevention A critical step in preventing injury to a vertebral artery is being cognizant of its anatomy and aware of potential anomalies in its anatomy and course. The vertebral artery is most susceptible to injury anteriorly at C7, laterally at C3-C6, and posteriorly at C1-C2. After branching from the subclavian artery, it enters through
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Figure 1
Figure 2
Axial T2-weighted magnetic resonance image demonstrating a right hypoplastic vertebral artery (horizontal arrow) and medial migration of the left vertebral artery (vertical arrow).
the C6 transverse foramen in 92% to 95% of patients.3,4 As the vertebral artery ascends from C6 to C3, it moves in a slightly posterior and medial direction and is located on average 3.3 6 1.6 mm lateral to the lateral margin of the uncovertebral joints.3 It deviates 45° laterally through the C2 foramen before traveling posteriorly and medially above the ring of C1. At a distance of 8 to 18 mm from the midline, it abruptly turns superiorly toward the foramen magnum.5 Although these numbers can be a helpful reference, they do not replace a careful preoperative examination of the course of the vertebral arteries in a patient using all available modalities for axial imaging. After noting the level at which the vertebral arteries enter the spine, the medial border of each transverse foramen should be noted, looking for any medial migration of the arteries (Figure 1). A review of 250
Sagittal (A) and axial (B) CT images demonstrating a tortuous vertebral artery (arrowheads) in the spinal canal.
consecutive patients’ MRI results identified medial migration of the vertebral artery in 19 patients (7.6%).4 Other anatomic variations in the vertebral arteries include anomalies such as multiluminal or unilaterally hypoplastic arteries and extraforaminal anomalies, which can occur anterior to the transverse processes6 (Figures 1 and 2). Throughout any anterior surgical procedure on the cervical spine, the surgeon must always know the location of the midline. This is reliably done by marking the midline before dissection of the longus colli and identifying the medial portion of the uncovertebral joints and using them as a continuous reference for bone and soft-tissue removal. When dissecting laterally under the longus colli with monopolar electrocautery, it should be set at a low intensity to minimize the transduction of heat through surrounding
structures, which can cause vertebral artery injury. Similarly, bipolar electrocautery or transcollation technology can be used for this portion of a surgical procedure to prevent arterial injuries caused by the arcing of energy. Venous bleeding should be controlled with topical hemostatic agents and paddies as opposed to being chased into the lateral vertebral body with the electrocautery device. A recommended width for safe vertebral body removal during corpectomy is approximately 15 mm, given that the average interforaminal distance varies from 26 to 29 mm. An off-center, asymmetric, or oblique corpectomy trough can put the vertebral artery at risk of injury. The wall of the vertebral body opposite the chief surgeon is generally more prone to injury secondary to an oblique corpectomy trough. During diskectomies and corpectomies, trumpet laminectomy, creating a space .15 mm, can be used for the
Dr. Rihn or an immediate family member serves as a paid consultant to or is an employee of Pfizer; has received research or institutional support from DePuy; and serves as a board member, owner, officer, or committee member of the North American Spine Society. Dr. Brodke or an immediate family member has received royalties from Amedica, DePuy Synthes, and Medtronic; serves as a paid consultant to and has stock or stock options held in Amedica; and serves as a board member, owner, officer, or committee member of the Cervical Spine Research Society and the Lumbar Spine Research Society. Dr. Lee or an immediate family member has received research or institutional support from Stryker. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Bible and Dr. Lim.
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optimal lateral decompression of neural structures (Figure 3).
Treatment In the instance of a vertebral artery injury, the therapeutic goals include control of local hemorrhage, prevention of immediate vertebrobasilar ischemia, and prevention of cerebrovascular complications (Figure 4). Efforts should be made immediately after injury to tamponade bleeding with local pressure, using thromboplastic agents and surgical patties. The use of bone wax or other particulate materials should be avoided if possible, given the theoretical risk of embolization. After bleeding is controlled, surgeons should avoid the temptation to definitively treat a vertebral artery injury solely with packing or tamponade because of the risk of delayed hemorrhage or creation of a fistula or pseudoaneurysm. During the process of tamponade and before any further surgical exploration is attempted, the operating room staff and anesthesiologists should be immediately notified, and the protocol for massive transfusion should be activated because of the potential for 3 to 5 L of rapid blood loss from vertebral artery injury. Intraoperative consultation with a vascular surgeon should also be considered. In addition, the head of the bed should be immediately returned to the neutral position to ensure the contralateral vertebral artery will not be mechanically occluded. At this point, the decision must be made either to have the patient undergo immediate angiography evaluation and possible coil/stent treatment or further surgical exploration with a possible repair or direct ligation. This decision is based on the stability of the patient and area of tamponade, availability and proximity of angiographic services, anatomic site and mechanism of injury, and vertebral artery dominance, if it is known. A
patient who remains in an unstable state or in whom active bleeding persists despite efforts at hemostasis should not be transported from the operating room to an angiography suite. If the injured vertebral artery is known to be dominant or the contralateral artery is not patent because of prior pathology, repair of the injured artery should be undertaken. The direct repair or ligation of an injured vertebral artery requires that the ipsilateral artery be clearly exposed above and below the site of injury. For an arterial injury during an anterior procedure, the skin incision made for the latter can be extended and the sternocleidomastoid muscle partially transected at the level of the arterial injury to create an improved working area. The ipsilateral longus colli is dissected laterally over the transverse processes above and below the site of injury. For the distal control of bleeding, the injured vertebral artery is dissected out and a temporary clamp applied at the C6-C7 level before the artery enters the C6 transverse foramen (Figure 5). For proximal control, the transverse process directly cephalad to the site of injury is unroofed using a 2- or 3-mm Kerrison rongeur and the intertransversarii muscles are carefully removed. Before a clamp is applied proximally, determination is made of the presence or absence of retrograde flow from the injury site. If good backfilling of the artery is seen, the patient can be presumed to have a patent circle of Willis or collateral antegrade flow, allowing direct ligation to remain a potentially viable option if the repair is unsuccessful.7 In addition, any significant changes in baseline neurologic function observed in neuromonitoring should be taken into account when assessing for adequate perfusion. With clamps in place cephalad and caudal to the injury site, surgical repair is done with 7-0 or 8-0
Figure 3
Axial CT slice demonstrating a trumpet-shaped decompression for corpectomy (dark lines), allowing lateral decompression posterior to the vertebral arteries.
nonabsorbable polypropylene suture. If repair is unsuccessful or technically impossible, direct ligation with hemoclips should be considered. Blind placement of clamps should be avoided because of the potential for damaging exiting nerve roots. Although most patients who sustain a vertebral artery injury can tolerate unilateral ligation of the injured artery, it poses a grave risk of neurologic compromise in those with an absent, hypoplastic, or stenotic contralateral artery. Wallenberg syndrome, cerebellar infarction, cranial nerve palsies, and quadriparesis have been reported in such patients, with death occurring in as many as 12%.8 The reported incidences of hypoplasia and the absence of the left vertebral artery are 5.7% and 1.3%, respectively, and of the right vertebral artery are 8.8% and 3.1%, respectively.9 If arterial injury occurs posteriorly at C1 or C2, direct repair and even ligation can be technically difficult because of poor visualization. If injury occurs during exposure of these cervical vertebrae, an approach similar to that described earlier is taken to expose the artery above and below the site of injury. This can
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Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery
Figure 4
Treatment algorithm for vertebral artery injury. ICU = intensive care unit, OR = operating room
entail removing the lateral masses of C2 and C3 and/or the posterior ring of C1. If injury is noted when drilling or tapping for screw placement, the screw can be placed to plug the drill hole, and bleeding and hemodynamic stability in the surrounding area can be reassessed. Following the procedure, the patient should be sent for angiography for potential coiling. Following any vertebral artery injury, the integrity of the repair or ligation is confirmed with angiography. The patient is admitted to the intensive care unit for monitoring. The latter should include vigilance for pseudoaneurysm or late hemorrhage. Anticoagulation and/or antiplatelet therapy should also be considered to reduce the risk of vertebrobasilar thromboembolism.
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Esophageal Injury Incidence Reported rates of esophageal injury during anterior cervical spine surgeries are 0.3% for diskectomy and fusion, 1.6% for corpectomy, and 1.5% for fracture repair.10 Causes of injury can include trauma, erosion by anterior osteophytes, intraoperative injury, and delayed injury from instrumentationrelated erosion (eg, prominent plates or loose screws).
Prevention The esophagus sits immediately posterior to the longus colli muscle, requiring that retractors be placed around it for visualization of the
midline during procedures on the cervical spine. The use of retractors, as well as the coverage of the posterior esophageal mucosa by only a thin layer of connective tissue, makes injury to the esophagus possible, especially proximally at the Lannier triangle (dorsal midline area just below cricopharyngeus muscle). The importance of careful manual retraction should be stressed to novice surgical assistants. When selfretaining retractors are placed, special attention should be given to ensuring that no esophageal folds are protruding into the surgical field, making them susceptible to injury by a burr or drill. Weakened and/or distorted esophageal anatomy can be expected in cases of surgical revision, tumor, or
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infection. Steps to avoid esophageal injury include careful dissection and retraction, and placement of a nasogastric or orogastric tube to help locate the esophagus during dissection.
Figure 5
Evaluation and Treatment The most important step in treating an esophageal injury is recognizing it initially. Intraoperative injury can sometimes be noted with direct visualization. However, this can be unreliable, especially with small tears. In a cadaver study of esophageal perforations, poor sensitivity was seen with reliance only on intraesophageal dye injection (methylene blue/indigo carmine) via a nasogastric tube.11 Better, although still limited, detection was achieved with the addition of a Foley catheter distal to the suspected area of injury. Early in the postoperative period, perforation of the esophagus in a missed intraoperative injury may present as neck pain, dysphagia, odynophagia, fever, swelling of the neck, wound drainage of food, or subcutaneous emphysema/crepitus. An injury with delayed presentation, caused by instrument-related erosion, presents in a similar manner with dysphagia or pneumonia of new onset. The evaluation of an esophageal injury includes radiography with or without CT to assess the position of instrumentation and/or a graft and for soft-tissue swelling, pneumomediastinum, or abscess/fluid collection. Contrast esophagoscopy can also be considered but has a false-negative rate of 10%, with barium being slightly more sensitive than diatrizoate meglumine for detecting esophageal tears.12 If, after an initial study that is read as normal, a patient’s clinical symptoms raise high suspicion of a tear, direct visualization via surgical exploration can be considered. However, a less invasive method of assessment
Illustration showing distal control of the left vertebral artery at C7 before it enters the C6 transverse foramen. Inset, the transverse process at the level or levels of injury is then unroofed with a Kerrison rongeur.
involves performing serial esophagrams, with surgical exploration done only after a tear is identified on imaging. If an esophageal tear is detected during surgery on the cervical spine, primary repair is the standard of care, performed preferably by an otolaryngologist or general surgeon. The patient should remain on status of no oral foods or liquids (ie, NPO), with a nasogastric or Dobhoff tube in place, until a swallowing study yields a normal result. In addition, an esophagram is commonly done at 7 to 10 days after the repair of an esophageal tear. A muscle flap may be required to allow the tension-free closure of a delayed or late
perforation, with a pedicled graft of the sternocleidomastoid muscle most commonly used.
Neurologic Injury Spinal Cord Injury Scant literature exists on perioperatve injury to the spinal cord in cervical spine surgery, but it has been reported to have a low incidence (,1%).13,14 Such injury can occur during any phase of the perioperative process, with potential causes including hyperextension of the neck during intubation/positioning, hypotension, hematoma, inadequate decompression, interbody graft/cage
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Figure 6
Checklist of items for rapid review in the event of a major intraoperative neuromonitoring alert during a cervical spine procedure. ABG = arterial blood gas, EBL = estimated blood loss, IV = intravenous, MAP = mean arterial pressure
dislodgement, and surgical trauma. Certain patients may be at particularly high risk of cord injury, such as those with severe myelopathy (myelomalacia), spinal instability, and ankylosing spondylitis, and those undergoing correction of a significant deformity. The keys to avoiding a perioperative cord injury are communication with the operating room staff and anesthesia team and vigilant attention to detail. Before intubating the patient, the surgical team should directly communicate with the anesthesia team about the severity of any spinal stenosis and not restrict this communication to any traumatic instability. A review of the American Society of Anesthesiologists Closed Claims database found that 57% of perioperative injuries to the cervical spinal cord occurred in patients with underlying stenosis and/or herniation, as opposed to only 24% of such injuries occurring in patients with notable cervical instability.15 For this reason, fiberoptic intubation, rather than direct laryngoscopy, should be
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strongly considered in patients with instability or a tenuous cord resulting from compressive cord pathology. Furthermore, mean arterial pressures (MAPs) should be kept .85 mm Hg until decompression is done or the correction of a deformity has been completed.16 If possible, this pressure should also be maintained during intubation and all subsequent positioning of the patient. Similarly, a cognizant neuromonitoring team can be especially helpful in minimizing neurologic injury. Any signs of lability should be immediately relayed to the surgical and anesthesia teams. The spine surgeon should have a memorized checklist for review in the event of a major neuromonitoring alert to allow prompt and aggressive management of its source. When running through the list, the surgeon should also keep in mind that falsepositive neuromonitoring alerts can occur and that some interventions may cause harm. A typical series of items for swift review include ensuring that the patient has a MAP .85
mm Hg, temperature .36.5° C, hemoglobin .8 g/dL, and whether the patient has recently undergone untaping of the shoulders, repositioning of the neck, release of a deformity correction, or removal of an implant (Figure 6). Depending on the stage of an operation on the cervical spine, aborting the procedure or a wake-up test can also be considered. If a cord injury persists postoperatively, potentially reversible causes for it are investigated with MRI and/or CT. Patients with persisting injury are admitted to the intensive care unit to maintain the MAP .85 mm Hg and hemoglobin .10 g/dL for 3 to 5 days, and may be treated with intravenous steroids. 17 Peripheral nerve injuries during cervical spine surgery are most often the result of improper positioning, with the most frequent injuries being ulnar neuropathy and brachial plexus injury. Although rare, both types of injury can lead to devastating deficits in upper extremity function.
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Figure 7
Figure 8
Lateral clinical photographs demonstrating an unprotected (A) and protected (B) ulnar nerve during supine positioning of the patient before the patient’s arms are tucked or “papoosed” for anterior cervical procedures. Lines or wires traversing the medial side of the elbow should be avoided, as seen in (A).
Ulnar Neuropathy Ulnar neuropathy is the most common type of perioperative peripheral nerve injury in cervical spine surgery, being responsible for 28% of all claims for anesthesia-related nerve injury.18 Its end result can be loss of intrinsic hand function and a clawlike deformity of the hand. Preexisting subclinical neuropathy can manifest in the perioperative period when patients undergoing cervical spine surgery are subjected to certain predisposing factors, such as prolonged hypotension. Other patientrelated risk factors for perioperative ulnar neuropathy include extreme thinness and obesity, older age, and male sex.19 Men are more susceptible to direct pressure on the unmyelinated fibers of the ulnar nerve than are women.20 Initial symptoms of ulnar neuropathy in patients undergoing cervical spine surgery are usually noted .24 hours postoperatively,19,21 with ,10% of instances of such neuropathy having been noted in the postoperative recovery unit in a large retrospective study.19 In this study, 47% of ulnar neuropathies presented as sensory deficits, with the remaining 53% presenting as mixed sensory and motor deficits. At 1 year
postoperatively, 41% of the patients who had experienced postoperative deficits had persistent deficits. Patients with mixed deficits were less likely to have a complete recovery (35%) than were patients with purely sensory deficits (80%).19 Before positioning the arms of patients in preparation for surgery on the cervical spine, the elbows of both arms should be wrapped with gel or foam pads, with care taken to ensure that the caudal surfaces of the elbows are adequately protected (Figure 7). Similarly, the number of lines and/or wires that traverse the arms should be minimized, especially over the medial side of the elbow. If no significant improvements in symptoms of apparent ulnar neuropathy are seen at 6 weeks, electromyographic testing should be considered and, if necessary, the patient should be referred to a hand specialist.
Brachial Plexus Injury Brachial plexus injury can result from the stretching or compression of nerves with subsequent ischemia of the vasa nervorum. During procedures on the cervical spine, traction injuries are most commonly the result of taping the patient’s shoulders to optimally visualize the level of
Photograph demonstrating the use of the surgeon’s hand to control the desired tension on the shoulder and brachial plexus while securing tape to the operating table distally for procedures done on the cervical spine.
interest on the localizing lateral radiograph. Under general anesthesia, especially with the use of muscle relaxants for intubation, patients have reduced defensive muscle tone, making it easy for an inattentive surgeon to apply too much traction. After affixing tape to the shoulder, the surgeon can place one hand over the tape and gently pull the shoulder down until the desired degree of tension is achieved (Figure 8). With this hand kept in place over the shoulder, the surgeon can then use the other hand (or ask an assistant) to affix the distal end of the tape to the operating table. Taping in this manner allows the surgeon to better gauge the tension on the patient’s brachial plexus rather than pulling distally using only the affixed tape. If neuromonitoring is being used and baseline values are recorded before the patient is positioned, they should be recorded before taping to provide the surgical team with a set of baseline values with which to determine whether the tape needs to be relaxed. Likewise, if adequate visualization cannot to obtained without excessive traction, further dissection can be carried cephalad until adequate radiographic localization occurs at a more cephalad level. From
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this point, the surgeon can manually count down to the cervical level of interest. In the case of a new postoperative deficit thought to be potentially related to injury of the brachial plexus, an MRI of the cervical spine should be done to rule out a compressive disorder masquerading as a plexus injury. Given that most brachial plexus injuries in the setting of cervical spine surgery are tractionrelated injuries to upper nerve roots (C5 and C6), patients who manifest signs of such injury can be given a sling for comfort and physical therapy to prevent adhesive capsulitis of the shoulder and/or elbow contractures.
Cerebrospinal Fluid Leaks Incidence CSF leaks in the cervical spine are rare, with a 1% (n = 20) incidence seen in a retrospective review of 1,994 patients who underwent cervical spine surgery from 1994 through 2005.22 A 12.5% rate of CSF leakage was seen in patients who had ossification of the posterior longitudinal ligament, and a 1.9% rate in patients who had anterior revision procedures. Seventy percent of anterior dural tears were caused by a Kerrison rongeur and 20% of posterior tears were caused by Bovie electrocautery or in opening of the lamina during laminoplasty. Eleven leaks were treated without repair or lumbar drainage, five with direct repair, and four without repair but with lumbar drainage. Only one patient (who had no repair or lumbar drainage) required a second operation for persistent leakage of CSF.22 CSF leaks in cervical trauma are also rare, with higher-energy injuries more likely to cause a dural tear. More common patterns of injury associated with CSF leaks include bilateral facet dislocations and compression-flexion
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injuries (stages IV and V). Most leaks associated with bilateral facet dislocations occur posteriorly and usually do not need to be repaired because of coverage by bone and/or ligamentum flavum of the dural tear through which they occur, allowing the tear to seal itself. In severe compressionflexion injuries, the retropulsed vertebral body tears into the dura, causing an anterior leak. These leaks are more likely to be persistent and often require a decompressive corpectomy and direct repair, if possible.
Prevention Many cervical CSF leaks are unavoidable, particularly in the setting of trauma and ossification of the posterior longitudinal ligament. However, careful use of Kerrison and pituitary rongeurs is critical to minimizing the tears responsible for cervical CSF leaks. During posterior dissection with unipolar electrocautery, special attention should be given to avoid falling into an interlaminar space. This is especially true in patients with widened interlaminar spaces.
Treatment Early diagnosis is key, with direct visualization of a leak being optimal. Occult leaks can be diagnosed based on clear drainage from surgical incision, CT myelography, and/or clinical signs (eg, blurred vision, headaches, light sensitivity, bogginess in the vicinity of the incision). Treatment strategies for cervical CSF leaks include direct repair, counterpressure, and the placement of diverting drains. Whenever possible, a leak should be directly repaired with a Gore-Tex (Gore Medical) or silk suture. Postoperatively, the head of the patient’s bed should be raised to $30° to maintain a low intrathecal pressure. For posterior cervical leaks, maintaining the head of the bed at 90° can
help in reducing CSF pressure at the site of the repair. Dural sealants can be used to reinforce “leaky” repairs; however, the surgeon must beware of sealant expansion, which can lead to neural compression. When direct repair of a cervical CSF leak is impossible, autologous fascia, fat, or collagen matrix can be used as a dural graft. If possible, stay sutures are placed at the corners of the graft, holding it in place before a dural sealant further secures the graft. This technique can be valuable in the setting of an anterior cervical CSF leak that cannot be adequately exposed for repair. In such a case, a fascia graft or collagen matrix is laid over the defect and held in place with dural sealant and Gelfoam (Pfizer) before a tricortical bone graft or cage is placed in the usual fashion. More dural sealant can then be added in the lateral gutters. If a CSF leak cannot be directly repaired, placement of a lumbar shunt should be considered, with the flow of CSF titrated to 10 mL/h. Also, a low threshold should be set for lumbar drainage in ventilatordependent patients because positivepressure ventilation increases intradural pressure, potentially causing CSF leaks.
Complications of Instrumentation The increasing use of spinal instrumentation expands the realm of complications of its use, especially with a growing osteoporotic population. Many surgeons are aware of various techniques of such instrumentation and the potential for immediate complications associated with the nonanatomic placement of spinal instrumentation. However, it is important to be familiar with salvage or bailout techniques to help mitigate intraoperative complications of spinal instrumentation.
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Posterior Instrumentation During posterior procedures on the subaxial cervical spine, lateral-mass fixation can at times be tenuous because of poor screw purchase. If the walls of the pilot hole for a screw remain intact, a larger diameter salvage screw can be used with the hope of gaining better purchase. However, this sometimes still provides poor fixation, especially when the superolateral quadrant of a lateral mass sustains a blowout fracture during drilling or screw insertion. In this situation, conversion to a RoyCamille technique or the use of a transfacet screw can be considered as a salvage procedure. In the RoyCamille technique for lateral mass fixation with screws, the screw trajectory is more horizontal and perpendicular to the lateral mass, in contrast to the parallel articular facet in most other insertion techniques. Transfacet screws provide purchase of the ventral cortex of the inferior articular process when directed distally across the facet joint. Failure of a lateral-mass screw inserted at C7 is not an exceedingly rare event, given the small anteroposterior dimensions and steep surface of this vertebra. However, pedicle-screw placement at this level provides a robust rescue option in this situation. In the case of poor screw purchase in the atlantoaxial region, supplemental laminar wiring and cortical bone grafting remain viable salvage options. Additionally, the utilization of laminar screws at C2 should be remembered in the setting of a failed pars/pedicle screw or anatomic limitations created by the vertebral artery.
Anterior Instrumentation Before the placement of an anterior plate in the cervical spine, anterior osteophytes should be burred down to allow the plate to rest flat against the bone, providing the best biomechanical
environment for screw fixation. If screw purchase is poor, larger diameter and/or longer screws may be placed. Another option to address poor screw purchase in placing an anterior plate in the cervical spine is bicortical screw fixation. This can be done through stepwise drilling and the use of a depth gauge, together with fluoroscopy to avoid catastrophic complications. If anterior fixation remains poor despite these options, especially in a patient with considerable cervical spinal instability, a low threshold should exist for supplemental posterior fixation.
Summary Intraoperative complications during cervical spine surgery are rare. Having a systematic approach to preventing and immediately managing such complications, and especially vertebral artery and neurologic injuries, can potentially reduce any associated morbidity.
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3. Ebraheim NA, Lu J, Brown JA, Biyani A, Yeasting RA: Vulnerability of vertebral artery in anterolateral decompression for cervical spondylosis. Clin Orthop Relat Res 1996;322:146-151. 4. Eskander MS, Drew JM, Aubin ME, et al: Vertebral artery anatomy: A review of two hundred fifty magnetic resonance imaging scans. Spine (Phila Pa 1976) 2010;35(23): 2035-2040. 5. Ebraheim NA, Xu R, Ahmad M, Heck B: The quantitative anatomy of the vertebral artery groove of the atlas and its relation to the posterior atlantoaxial approach. Spine (Phila Pa 1976) 1998;23(3): 320-323. 6. Curylo LJ, Mason HC, Bohlman HH, Yoo JU: Tortuous course of the vertebral artery and anterior cervical decompression: A cadaveric and clinical case study. Spine (Phila Pa 1976) 2000;25(22): 2860-2864. 7. Ye JY, Ayyash OM, Eskander MS, Kang JD: Control of the vertebral artery from a posterior approach: A technical report. Spine J 2014;14(6):e37-e41. 8. Shintani A, Zervas NT: Consequence of ligation of the vertebral artery. J Neurosurg 1972;36(4):447-450. 9. Bernard G, Laurian C: The Vertebral Artery: Pathology and Surgery. New York, NY, Springer-Verlag GmbH Wien, 1987. 10. Orlando ER, Caroli E, Ferrante L: Management of the cervical esophagus and hypofarinx perforations complicating anterior cervical spine surgery. Spine (Phila Pa 1976) 2003;28 (15):e290-e295. 11. Taylor B, Patel AA, Okubadejo GO, Albert T, Riew KD: Detection of esophageal perforation using intraesophageal dye injection. J Spinal Disord Tech 2006;19(3):191-193. 12. Buecker A, Wein BB, Neuerburg JM, Guenther RW: Esophageal perforation: Comparison of use of aqueous and bariumcontaining contrast media. Radiology 1997;202(3):683-686. 13. Cramer DE, Maher PC, Pettigrew DB, Kuntz C IV: Major neurologic deficit immediately after adult spinal surgery: Incidence and etiology over 10 years at a single training institution. J Spinal Disord Tech 2009;22(8):565-570. 14. Graham JJ: Complications of cervical spine surgery: A five-year report on a survey of the membership of the Cervical Spine Research Society by the Morbidity and Mortality Committee. Spine (Phila Pa 1976) 1989;14(10):1046-1050. 15.
Hindman BJ, Palecek JP, Posner KL, et al: Cervical spinal cord, root, and bony spine injuries: A closed claims analysis. Anesthesiology 2011;114(4):782-795.
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Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery 16. Ryken TC, Hurlbert RJ, Hadley MN, et al: The acute cardiopulmonary management of patients with cervical spinal cord injuries. Neurosurgery 2013;72(suppl 2): 84-92. 17. Fehlings MG, Tighe A: Spinal cord injury: The promise of translational research. Neurosurg Focus 2008;25(5):e1. 18. Cheney FW, Domino KB, Caplan RA, Posner KL: Nerve injury associated with
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anesthesia: A closed claims analysis. Anesthesiology 1999;90(4):1062-1069. 19. Warner MA, Warner ME, Martin JT: Ulnar neuropathy: Incidence, outcome, and risk factors in sedated or anesthetized patients. Anesthesiology 1994;81(6): 1332-1340. 20. Morell RC, Prielipp RC, Harwood TN, James RL, Butterworth JF: Men are more susceptible than women to direct pressure
on unmyelinated ulnar nerve fibers. Anesth Analg 2003;97(4):1183-1188. 21. Alvine FG, Schurrer ME: Postoperative ulnar-nerve palsy: Are there predisposing factors? J Bone Joint Surg Am 1987;69(2): 255-259. 22. Hannallah D, Lee J, Khan M, Donaldson WF, Kang JD: Cerebrospinal fluid leaks following cervical spine surgery. J Bone Joint Surg Am 2008;90(5):1101-1105.
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Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery Abstract Jesse E. Bible, MD, MHS Jeffrey A. Rihn, MD Moe R. Lim, MD Darrel S. Brodke, MD Joon Y. Lee, MD
The incidence of intraoperative complications in cervical spine surgery is low. However, when they do occur, such complications have the potential for causing considerable morbidity and mortality. Spine surgeons should be familiar with methods of minimizing such complications. Furthermore, if they do occur, surgeons must be prepared to immediately treat each potential complication to reduce any associated morbidity.
C From the Department of Orthopaedics and Rehabilitation, Penn State Milton S. Hershey Medical Center, Hershey, PA (Dr. Bible), The Rothman Institute, Thomas Jefferson University, Philadelphia, PA (Dr. Rihn), the Department of Orthopaedics, University of North Carolina at Chapel Hill, Chapel Hill, NC (Dr. Lim), the Department of Orthopaedics, University of Utah, Salt Lake City, UT (Dr. Brodke) and the Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA (Dr. Lee). This article, as well as other lectures presented at the Academy’s Annual Meeting, will be available in March 2016 in Instructional Course Lectures, Volume 65. J Am Acad Orthop Surg 2015;23: e81-e90 http://dx.doi.org/10.5435/ JAAOS-D-14-00446 Copyright 2015 by the American Academy of Orthopaedic Surgeons.
omplications related to cervical spine surgery can range in incidence and associated morbidity and mortality. Complications with a delayed onset, including dysphagia, nonunion, and adjacent-segment disease, are more common than those of immediate onset. The former types of complications are associated with reduced relative morbidity and often can be treated nonsurgically. Conversely, intraoperative complications occur much less often but are associated with more significant morbidity and mortality. Given that intraoperative complications are inevitable despite the use of the best surgical techniques, surgeons should be familiar with the risk factors, methods of prevention, and immediate treatment options for such complications, with the goal of mitigating any associated morbidity and mortality. Here, we discuss intraoperative vertebral artery, neurologic, and esophageal injuries, as well as cerebrospinal fluid (CSF) leaks and complications of instrumentation related to surgery on the cervical spine.
Vertebral Artery Injury Incidence Vertebral artery injury is a very rare event, but it can be associated with considerable morbidity and mortality. In one report, the incidence of injury during anterior cervical spine surgeries was 0.3%.1 In a survey of members of the Cervical Spine Research Society, the overall incidence of vertebral artery injury in the cervical spine was 0.07% (111 of 163,324 surgeries).2 Instrumentation of the upper cervical spine (32%), anterior corpectomy (23%), and posterior exposure (12%) was the most common surgical factor associated with injury.
Prevention A critical step in preventing injury to a vertebral artery is being cognizant of its anatomy and aware of potential anomalies in its anatomy and course. The vertebral artery is most susceptible to injury anteriorly at C7, laterally at C3-C6, and posteriorly at C1-C2. After branching from the subclavian artery, it enters through
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Figure 1
Figure 2
Axial T2-weighted magnetic resonance image demonstrating a right hypoplastic vertebral artery (horizontal arrow) and medial migration of the left vertebral artery (vertical arrow).
the C6 transverse foramen in 92% to 95% of patients.3,4 As the vertebral artery ascends from C6 to C3, it moves in a slightly posterior and medial direction and is located on average 3.3 6 1.6 mm lateral to the lateral margin of the uncovertebral joints.3 It deviates 45° laterally through the C2 foramen before traveling posteriorly and medially above the ring of C1. At a distance of 8 to 18 mm from the midline, it abruptly turns superiorly toward the foramen magnum.5 Although these numbers can be a helpful reference, they do not replace a careful preoperative examination of the course of the vertebral arteries in a patient using all available modalities for axial imaging. After noting the level at which the vertebral arteries enter the spine, the medial border of each transverse foramen should be noted, looking for any medial migration of the arteries (Figure 1). A review of 250
Sagittal (A) and axial (B) CT images demonstrating a tortuous vertebral artery (arrowheads) in the spinal canal.
consecutive patients’ MRI results identified medial migration of the vertebral artery in 19 patients (7.6%).4 Other anatomic variations in the vertebral arteries include anomalies such as multiluminal or unilaterally hypoplastic arteries and extraforaminal anomalies, which can occur anterior to the transverse processes6 (Figures 1 and 2). Throughout any anterior surgical procedure on the cervical spine, the surgeon must always know the location of the midline. This is reliably done by marking the midline before dissection of the longus colli and identifying the medial portion of the uncovertebral joints and using them as a continuous reference for bone and soft-tissue removal. When dissecting laterally under the longus colli with monopolar electrocautery, it should be set at a low intensity to minimize the transduction of heat through surrounding
structures, which can cause vertebral artery injury. Similarly, bipolar electrocautery or transcollation technology can be used for this portion of a surgical procedure to prevent arterial injuries caused by the arcing of energy. Venous bleeding should be controlled with topical hemostatic agents and paddies as opposed to being chased into the lateral vertebral body with the electrocautery device. A recommended width for safe vertebral body removal during corpectomy is approximately 15 mm, given that the average interforaminal distance varies from 26 to 29 mm. An off-center, asymmetric, or oblique corpectomy trough can put the vertebral artery at risk of injury. The wall of the vertebral body opposite the chief surgeon is generally more prone to injury secondary to an oblique corpectomy trough. During diskectomies and corpectomies, trumpet laminectomy, creating a space .15 mm, can be used for the
Dr. Rihn or an immediate family member serves as a paid consultant to or is an employee of Pfizer; has received research or institutional support from DePuy; and serves as a board member, owner, officer, or committee member of the North American Spine Society. Dr. Brodke or an immediate family member has received royalties from Amedica, DePuy Synthes, and Medtronic; serves as a paid consultant to and has stock or stock options held in Amedica; and serves as a board member, owner, officer, or committee member of the Cervical Spine Research Society and the Lumbar Spine Research Society. Dr. Lee or an immediate family member has received research or institutional support from Stryker. Neither of the following authors nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this article: Dr. Bible and Dr. Lim.
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optimal lateral decompression of neural structures (Figure 3).
Treatment In the instance of a vertebral artery injury, the therapeutic goals include control of local hemorrhage, prevention of immediate vertebrobasilar ischemia, and prevention of cerebrovascular complications (Figure 4). Efforts should be made immediately after injury to tamponade bleeding with local pressure, using thromboplastic agents and surgical patties. The use of bone wax or other particulate materials should be avoided if possible, given the theoretical risk of embolization. After bleeding is controlled, surgeons should avoid the temptation to definitively treat a vertebral artery injury solely with packing or tamponade because of the risk of delayed hemorrhage or creation of a fistula or pseudoaneurysm. During the process of tamponade and before any further surgical exploration is attempted, the operating room staff and anesthesiologists should be immediately notified, and the protocol for massive transfusion should be activated because of the potential for 3 to 5 L of rapid blood loss from vertebral artery injury. Intraoperative consultation with a vascular surgeon should also be considered. In addition, the head of the bed should be immediately returned to the neutral position to ensure the contralateral vertebral artery will not be mechanically occluded. At this point, the decision must be made either to have the patient undergo immediate angiography evaluation and possible coil/stent treatment or further surgical exploration with a possible repair or direct ligation. This decision is based on the stability of the patient and area of tamponade, availability and proximity of angiographic services, anatomic site and mechanism of injury, and vertebral artery dominance, if it is known. A
patient who remains in an unstable state or in whom active bleeding persists despite efforts at hemostasis should not be transported from the operating room to an angiography suite. If the injured vertebral artery is known to be dominant or the contralateral artery is not patent because of prior pathology, repair of the injured artery should be undertaken. The direct repair or ligation of an injured vertebral artery requires that the ipsilateral artery be clearly exposed above and below the site of injury. For an arterial injury during an anterior procedure, the skin incision made for the latter can be extended and the sternocleidomastoid muscle partially transected at the level of the arterial injury to create an improved working area. The ipsilateral longus colli is dissected laterally over the transverse processes above and below the site of injury. For the distal control of bleeding, the injured vertebral artery is dissected out and a temporary clamp applied at the C6-C7 level before the artery enters the C6 transverse foramen (Figure 5). For proximal control, the transverse process directly cephalad to the site of injury is unroofed using a 2- or 3-mm Kerrison rongeur and the intertransversarii muscles are carefully removed. Before a clamp is applied proximally, determination is made of the presence or absence of retrograde flow from the injury site. If good backfilling of the artery is seen, the patient can be presumed to have a patent circle of Willis or collateral antegrade flow, allowing direct ligation to remain a potentially viable option if the repair is unsuccessful.7 In addition, any significant changes in baseline neurologic function observed in neuromonitoring should be taken into account when assessing for adequate perfusion. With clamps in place cephalad and caudal to the injury site, surgical repair is done with 7-0 or 8-0
Figure 3
Axial CT slice demonstrating a trumpet-shaped decompression for corpectomy (dark lines), allowing lateral decompression posterior to the vertebral arteries.
nonabsorbable polypropylene suture. If repair is unsuccessful or technically impossible, direct ligation with hemoclips should be considered. Blind placement of clamps should be avoided because of the potential for damaging exiting nerve roots. Although most patients who sustain a vertebral artery injury can tolerate unilateral ligation of the injured artery, it poses a grave risk of neurologic compromise in those with an absent, hypoplastic, or stenotic contralateral artery. Wallenberg syndrome, cerebellar infarction, cranial nerve palsies, and quadriparesis have been reported in such patients, with death occurring in as many as 12%.8 The reported incidences of hypoplasia and the absence of the left vertebral artery are 5.7% and 1.3%, respectively, and of the right vertebral artery are 8.8% and 3.1%, respectively.9 If arterial injury occurs posteriorly at C1 or C2, direct repair and even ligation can be technically difficult because of poor visualization. If injury occurs during exposure of these cervical vertebrae, an approach similar to that described earlier is taken to expose the artery above and below the site of injury. This can
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Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery
Figure 4
Treatment algorithm for vertebral artery injury. ICU = intensive care unit, OR = operating room
entail removing the lateral masses of C2 and C3 and/or the posterior ring of C1. If injury is noted when drilling or tapping for screw placement, the screw can be placed to plug the drill hole, and bleeding and hemodynamic stability in the surrounding area can be reassessed. Following the procedure, the patient should be sent for angiography for potential coiling. Following any vertebral artery injury, the integrity of the repair or ligation is confirmed with angiography. The patient is admitted to the intensive care unit for monitoring. The latter should include vigilance for pseudoaneurysm or late hemorrhage. Anticoagulation and/or antiplatelet therapy should also be considered to reduce the risk of vertebrobasilar thromboembolism.
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Esophageal Injury Incidence Reported rates of esophageal injury during anterior cervical spine surgeries are 0.3% for diskectomy and fusion, 1.6% for corpectomy, and 1.5% for fracture repair.10 Causes of injury can include trauma, erosion by anterior osteophytes, intraoperative injury, and delayed injury from instrumentationrelated erosion (eg, prominent plates or loose screws).
Prevention The esophagus sits immediately posterior to the longus colli muscle, requiring that retractors be placed around it for visualization of the
midline during procedures on the cervical spine. The use of retractors, as well as the coverage of the posterior esophageal mucosa by only a thin layer of connective tissue, makes injury to the esophagus possible, especially proximally at the Lannier triangle (dorsal midline area just below cricopharyngeus muscle). The importance of careful manual retraction should be stressed to novice surgical assistants. When selfretaining retractors are placed, special attention should be given to ensuring that no esophageal folds are protruding into the surgical field, making them susceptible to injury by a burr or drill. Weakened and/or distorted esophageal anatomy can be expected in cases of surgical revision, tumor, or
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infection. Steps to avoid esophageal injury include careful dissection and retraction, and placement of a nasogastric or orogastric tube to help locate the esophagus during dissection.
Figure 5
Evaluation and Treatment The most important step in treating an esophageal injury is recognizing it initially. Intraoperative injury can sometimes be noted with direct visualization. However, this can be unreliable, especially with small tears. In a cadaver study of esophageal perforations, poor sensitivity was seen with reliance only on intraesophageal dye injection (methylene blue/indigo carmine) via a nasogastric tube.11 Better, although still limited, detection was achieved with the addition of a Foley catheter distal to the suspected area of injury. Early in the postoperative period, perforation of the esophagus in a missed intraoperative injury may present as neck pain, dysphagia, odynophagia, fever, swelling of the neck, wound drainage of food, or subcutaneous emphysema/crepitus. An injury with delayed presentation, caused by instrument-related erosion, presents in a similar manner with dysphagia or pneumonia of new onset. The evaluation of an esophageal injury includes radiography with or without CT to assess the position of instrumentation and/or a graft and for soft-tissue swelling, pneumomediastinum, or abscess/fluid collection. Contrast esophagoscopy can also be considered but has a false-negative rate of 10%, with barium being slightly more sensitive than diatrizoate meglumine for detecting esophageal tears.12 If, after an initial study that is read as normal, a patient’s clinical symptoms raise high suspicion of a tear, direct visualization via surgical exploration can be considered. However, a less invasive method of assessment
Illustration showing distal control of the left vertebral artery at C7 before it enters the C6 transverse foramen. Inset, the transverse process at the level or levels of injury is then unroofed with a Kerrison rongeur.
involves performing serial esophagrams, with surgical exploration done only after a tear is identified on imaging. If an esophageal tear is detected during surgery on the cervical spine, primary repair is the standard of care, performed preferably by an otolaryngologist or general surgeon. The patient should remain on status of no oral foods or liquids (ie, NPO), with a nasogastric or Dobhoff tube in place, until a swallowing study yields a normal result. In addition, an esophagram is commonly done at 7 to 10 days after the repair of an esophageal tear. A muscle flap may be required to allow the tension-free closure of a delayed or late
perforation, with a pedicled graft of the sternocleidomastoid muscle most commonly used.
Neurologic Injury Spinal Cord Injury Scant literature exists on perioperatve injury to the spinal cord in cervical spine surgery, but it has been reported to have a low incidence (,1%).13,14 Such injury can occur during any phase of the perioperative process, with potential causes including hyperextension of the neck during intubation/positioning, hypotension, hematoma, inadequate decompression, interbody graft/cage
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Figure 6
Checklist of items for rapid review in the event of a major intraoperative neuromonitoring alert during a cervical spine procedure. ABG = arterial blood gas, EBL = estimated blood loss, IV = intravenous, MAP = mean arterial pressure
dislodgement, and surgical trauma. Certain patients may be at particularly high risk of cord injury, such as those with severe myelopathy (myelomalacia), spinal instability, and ankylosing spondylitis, and those undergoing correction of a significant deformity. The keys to avoiding a perioperative cord injury are communication with the operating room staff and anesthesia team and vigilant attention to detail. Before intubating the patient, the surgical team should directly communicate with the anesthesia team about the severity of any spinal stenosis and not restrict this communication to any traumatic instability. A review of the American Society of Anesthesiologists Closed Claims database found that 57% of perioperative injuries to the cervical spinal cord occurred in patients with underlying stenosis and/or herniation, as opposed to only 24% of such injuries occurring in patients with notable cervical instability.15 For this reason, fiberoptic intubation, rather than direct laryngoscopy, should be
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strongly considered in patients with instability or a tenuous cord resulting from compressive cord pathology. Furthermore, mean arterial pressures (MAPs) should be kept .85 mm Hg until decompression is done or the correction of a deformity has been completed.16 If possible, this pressure should also be maintained during intubation and all subsequent positioning of the patient. Similarly, a cognizant neuromonitoring team can be especially helpful in minimizing neurologic injury. Any signs of lability should be immediately relayed to the surgical and anesthesia teams. The spine surgeon should have a memorized checklist for review in the event of a major neuromonitoring alert to allow prompt and aggressive management of its source. When running through the list, the surgeon should also keep in mind that falsepositive neuromonitoring alerts can occur and that some interventions may cause harm. A typical series of items for swift review include ensuring that the patient has a MAP .85
mm Hg, temperature .36.5° C, hemoglobin .8 g/dL, and whether the patient has recently undergone untaping of the shoulders, repositioning of the neck, release of a deformity correction, or removal of an implant (Figure 6). Depending on the stage of an operation on the cervical spine, aborting the procedure or a wake-up test can also be considered. If a cord injury persists postoperatively, potentially reversible causes for it are investigated with MRI and/or CT. Patients with persisting injury are admitted to the intensive care unit to maintain the MAP .85 mm Hg and hemoglobin .10 g/dL for 3 to 5 days, and may be treated with intravenous steroids. 17 Peripheral nerve injuries during cervical spine surgery are most often the result of improper positioning, with the most frequent injuries being ulnar neuropathy and brachial plexus injury. Although rare, both types of injury can lead to devastating deficits in upper extremity function.
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Figure 7
Figure 8
Lateral clinical photographs demonstrating an unprotected (A) and protected (B) ulnar nerve during supine positioning of the patient before the patient’s arms are tucked or “papoosed” for anterior cervical procedures. Lines or wires traversing the medial side of the elbow should be avoided, as seen in (A).
Ulnar Neuropathy Ulnar neuropathy is the most common type of perioperative peripheral nerve injury in cervical spine surgery, being responsible for 28% of all claims for anesthesia-related nerve injury.18 Its end result can be loss of intrinsic hand function and a clawlike deformity of the hand. Preexisting subclinical neuropathy can manifest in the perioperative period when patients undergoing cervical spine surgery are subjected to certain predisposing factors, such as prolonged hypotension. Other patientrelated risk factors for perioperative ulnar neuropathy include extreme thinness and obesity, older age, and male sex.19 Men are more susceptible to direct pressure on the unmyelinated fibers of the ulnar nerve than are women.20 Initial symptoms of ulnar neuropathy in patients undergoing cervical spine surgery are usually noted .24 hours postoperatively,19,21 with ,10% of instances of such neuropathy having been noted in the postoperative recovery unit in a large retrospective study.19 In this study, 47% of ulnar neuropathies presented as sensory deficits, with the remaining 53% presenting as mixed sensory and motor deficits. At 1 year
postoperatively, 41% of the patients who had experienced postoperative deficits had persistent deficits. Patients with mixed deficits were less likely to have a complete recovery (35%) than were patients with purely sensory deficits (80%).19 Before positioning the arms of patients in preparation for surgery on the cervical spine, the elbows of both arms should be wrapped with gel or foam pads, with care taken to ensure that the caudal surfaces of the elbows are adequately protected (Figure 7). Similarly, the number of lines and/or wires that traverse the arms should be minimized, especially over the medial side of the elbow. If no significant improvements in symptoms of apparent ulnar neuropathy are seen at 6 weeks, electromyographic testing should be considered and, if necessary, the patient should be referred to a hand specialist.
Brachial Plexus Injury Brachial plexus injury can result from the stretching or compression of nerves with subsequent ischemia of the vasa nervorum. During procedures on the cervical spine, traction injuries are most commonly the result of taping the patient’s shoulders to optimally visualize the level of
Photograph demonstrating the use of the surgeon’s hand to control the desired tension on the shoulder and brachial plexus while securing tape to the operating table distally for procedures done on the cervical spine.
interest on the localizing lateral radiograph. Under general anesthesia, especially with the use of muscle relaxants for intubation, patients have reduced defensive muscle tone, making it easy for an inattentive surgeon to apply too much traction. After affixing tape to the shoulder, the surgeon can place one hand over the tape and gently pull the shoulder down until the desired degree of tension is achieved (Figure 8). With this hand kept in place over the shoulder, the surgeon can then use the other hand (or ask an assistant) to affix the distal end of the tape to the operating table. Taping in this manner allows the surgeon to better gauge the tension on the patient’s brachial plexus rather than pulling distally using only the affixed tape. If neuromonitoring is being used and baseline values are recorded before the patient is positioned, they should be recorded before taping to provide the surgical team with a set of baseline values with which to determine whether the tape needs to be relaxed. Likewise, if adequate visualization cannot to obtained without excessive traction, further dissection can be carried cephalad until adequate radiographic localization occurs at a more cephalad level. From
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this point, the surgeon can manually count down to the cervical level of interest. In the case of a new postoperative deficit thought to be potentially related to injury of the brachial plexus, an MRI of the cervical spine should be done to rule out a compressive disorder masquerading as a plexus injury. Given that most brachial plexus injuries in the setting of cervical spine surgery are tractionrelated injuries to upper nerve roots (C5 and C6), patients who manifest signs of such injury can be given a sling for comfort and physical therapy to prevent adhesive capsulitis of the shoulder and/or elbow contractures.
Cerebrospinal Fluid Leaks Incidence CSF leaks in the cervical spine are rare, with a 1% (n = 20) incidence seen in a retrospective review of 1,994 patients who underwent cervical spine surgery from 1994 through 2005.22 A 12.5% rate of CSF leakage was seen in patients who had ossification of the posterior longitudinal ligament, and a 1.9% rate in patients who had anterior revision procedures. Seventy percent of anterior dural tears were caused by a Kerrison rongeur and 20% of posterior tears were caused by Bovie electrocautery or in opening of the lamina during laminoplasty. Eleven leaks were treated without repair or lumbar drainage, five with direct repair, and four without repair but with lumbar drainage. Only one patient (who had no repair or lumbar drainage) required a second operation for persistent leakage of CSF.22 CSF leaks in cervical trauma are also rare, with higher-energy injuries more likely to cause a dural tear. More common patterns of injury associated with CSF leaks include bilateral facet dislocations and compression-flexion
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injuries (stages IV and V). Most leaks associated with bilateral facet dislocations occur posteriorly and usually do not need to be repaired because of coverage by bone and/or ligamentum flavum of the dural tear through which they occur, allowing the tear to seal itself. In severe compressionflexion injuries, the retropulsed vertebral body tears into the dura, causing an anterior leak. These leaks are more likely to be persistent and often require a decompressive corpectomy and direct repair, if possible.
Prevention Many cervical CSF leaks are unavoidable, particularly in the setting of trauma and ossification of the posterior longitudinal ligament. However, careful use of Kerrison and pituitary rongeurs is critical to minimizing the tears responsible for cervical CSF leaks. During posterior dissection with unipolar electrocautery, special attention should be given to avoid falling into an interlaminar space. This is especially true in patients with widened interlaminar spaces.
Treatment Early diagnosis is key, with direct visualization of a leak being optimal. Occult leaks can be diagnosed based on clear drainage from surgical incision, CT myelography, and/or clinical signs (eg, blurred vision, headaches, light sensitivity, bogginess in the vicinity of the incision). Treatment strategies for cervical CSF leaks include direct repair, counterpressure, and the placement of diverting drains. Whenever possible, a leak should be directly repaired with a Gore-Tex (Gore Medical) or silk suture. Postoperatively, the head of the patient’s bed should be raised to $30° to maintain a low intrathecal pressure. For posterior cervical leaks, maintaining the head of the bed at 90° can
help in reducing CSF pressure at the site of the repair. Dural sealants can be used to reinforce “leaky” repairs; however, the surgeon must beware of sealant expansion, which can lead to neural compression. When direct repair of a cervical CSF leak is impossible, autologous fascia, fat, or collagen matrix can be used as a dural graft. If possible, stay sutures are placed at the corners of the graft, holding it in place before a dural sealant further secures the graft. This technique can be valuable in the setting of an anterior cervical CSF leak that cannot be adequately exposed for repair. In such a case, a fascia graft or collagen matrix is laid over the defect and held in place with dural sealant and Gelfoam (Pfizer) before a tricortical bone graft or cage is placed in the usual fashion. More dural sealant can then be added in the lateral gutters. If a CSF leak cannot be directly repaired, placement of a lumbar shunt should be considered, with the flow of CSF titrated to 10 mL/h. Also, a low threshold should be set for lumbar drainage in ventilatordependent patients because positivepressure ventilation increases intradural pressure, potentially causing CSF leaks.
Complications of Instrumentation The increasing use of spinal instrumentation expands the realm of complications of its use, especially with a growing osteoporotic population. Many surgeons are aware of various techniques of such instrumentation and the potential for immediate complications associated with the nonanatomic placement of spinal instrumentation. However, it is important to be familiar with salvage or bailout techniques to help mitigate intraoperative complications of spinal instrumentation.
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Posterior Instrumentation During posterior procedures on the subaxial cervical spine, lateral-mass fixation can at times be tenuous because of poor screw purchase. If the walls of the pilot hole for a screw remain intact, a larger diameter salvage screw can be used with the hope of gaining better purchase. However, this sometimes still provides poor fixation, especially when the superolateral quadrant of a lateral mass sustains a blowout fracture during drilling or screw insertion. In this situation, conversion to a RoyCamille technique or the use of a transfacet screw can be considered as a salvage procedure. In the RoyCamille technique for lateral mass fixation with screws, the screw trajectory is more horizontal and perpendicular to the lateral mass, in contrast to the parallel articular facet in most other insertion techniques. Transfacet screws provide purchase of the ventral cortex of the inferior articular process when directed distally across the facet joint. Failure of a lateral-mass screw inserted at C7 is not an exceedingly rare event, given the small anteroposterior dimensions and steep surface of this vertebra. However, pedicle-screw placement at this level provides a robust rescue option in this situation. In the case of poor screw purchase in the atlantoaxial region, supplemental laminar wiring and cortical bone grafting remain viable salvage options. Additionally, the utilization of laminar screws at C2 should be remembered in the setting of a failed pars/pedicle screw or anatomic limitations created by the vertebral artery.
Anterior Instrumentation Before the placement of an anterior plate in the cervical spine, anterior osteophytes should be burred down to allow the plate to rest flat against the bone, providing the best biomechanical
environment for screw fixation. If screw purchase is poor, larger diameter and/or longer screws may be placed. Another option to address poor screw purchase in placing an anterior plate in the cervical spine is bicortical screw fixation. This can be done through stepwise drilling and the use of a depth gauge, together with fluoroscopy to avoid catastrophic complications. If anterior fixation remains poor despite these options, especially in a patient with considerable cervical spinal instability, a low threshold should exist for supplemental posterior fixation.
Summary Intraoperative complications during cervical spine surgery are rare. Having a systematic approach to preventing and immediately managing such complications, and especially vertebral artery and neurologic injuries, can potentially reduce any associated morbidity.
References Evidence-based Medicine: Levels of evidence are described in the table of contents. In this article, reference 20 is a level I study. References 12, 21, and 22 are level II studies. References 1, 6, 13, 15, 18, and 19 are level III studies. References 7, 8, and 10 are level IV studies. References 2-5, 9, 11, 14, 16, and 17 are level V expert opinion. References printed in bold type are those published within the past 5 years. 1. Burke JP, Gerszten PC, Welch WC: Iatrogenic vertebral artery injury during anterior cervical spine surgery. Spine J 2005;5(5):508-514. 2. Lunardini DJ, Eskander MS, Even JL, et al: Vertebral artery injuries in cervical spine surgery. Spine J 2014;14(8): 1520-1525.
3. Ebraheim NA, Lu J, Brown JA, Biyani A, Yeasting RA: Vulnerability of vertebral artery in anterolateral decompression for cervical spondylosis. Clin Orthop Relat Res 1996;322:146-151. 4. Eskander MS, Drew JM, Aubin ME, et al: Vertebral artery anatomy: A review of two hundred fifty magnetic resonance imaging scans. Spine (Phila Pa 1976) 2010;35(23): 2035-2040. 5. Ebraheim NA, Xu R, Ahmad M, Heck B: The quantitative anatomy of the vertebral artery groove of the atlas and its relation to the posterior atlantoaxial approach. Spine (Phila Pa 1976) 1998;23(3): 320-323. 6. Curylo LJ, Mason HC, Bohlman HH, Yoo JU: Tortuous course of the vertebral artery and anterior cervical decompression: A cadaveric and clinical case study. Spine (Phila Pa 1976) 2000;25(22): 2860-2864. 7. Ye JY, Ayyash OM, Eskander MS, Kang JD: Control of the vertebral artery from a posterior approach: A technical report. Spine J 2014;14(6):e37-e41. 8. Shintani A, Zervas NT: Consequence of ligation of the vertebral artery. J Neurosurg 1972;36(4):447-450. 9. Bernard G, Laurian C: The Vertebral Artery: Pathology and Surgery. New York, NY, Springer-Verlag GmbH Wien, 1987. 10. Orlando ER, Caroli E, Ferrante L: Management of the cervical esophagus and hypofarinx perforations complicating anterior cervical spine surgery. Spine (Phila Pa 1976) 2003;28 (15):e290-e295. 11. Taylor B, Patel AA, Okubadejo GO, Albert T, Riew KD: Detection of esophageal perforation using intraesophageal dye injection. J Spinal Disord Tech 2006;19(3):191-193. 12. Buecker A, Wein BB, Neuerburg JM, Guenther RW: Esophageal perforation: Comparison of use of aqueous and bariumcontaining contrast media. Radiology 1997;202(3):683-686. 13. Cramer DE, Maher PC, Pettigrew DB, Kuntz C IV: Major neurologic deficit immediately after adult spinal surgery: Incidence and etiology over 10 years at a single training institution. J Spinal Disord Tech 2009;22(8):565-570. 14. Graham JJ: Complications of cervical spine surgery: A five-year report on a survey of the membership of the Cervical Spine Research Society by the Morbidity and Mortality Committee. Spine (Phila Pa 1976) 1989;14(10):1046-1050. 15.
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