Summary of Key Points
- •
To avoid neurologic complications in high-risk patients, steroids may be used before incision and continued for 24 hours after surgery.
- •
In patients with severe stenosis at or above the level of C3-4, intubation with fiberoptic guidance, while the patient is awake, with use of local anesthesia is preferred.
- •
In patients with severe cervical spinal canal narrowing, the neutral or near-neutral position using three-point skull fixation is preferred.
- •
Both Doppler and end-tidal CO 2 monitoring must be used in all sitting-position operations to avoid air embolism.
- •
Suboptimally treated dural tears may result with cerebrospinal fluid cutaneous fistula and pseudomeningocele. Because they may lead to new problems such as pain, neurologic deficit, and infection, they must be treated aggressively with external lumbar drainage, percutaneous blood patch, revision surgery to repair the dural defect, myofascial closure of pseudomeningocele, or a lumboperitoneal shunt operation.
- •
In anterior cervical surgery, the incidence of recurrent laryngeal nerve injury does not differ significantly with the side of surgical approach. Its most common cause is compression of the recurrent laryngeal nerve within the endolarynx between the retractor and endotracheal cuff. We recommend releasing the cuff after retractor placement and avoiding excessive retraction of the medial structures.
- •
The extreme lateral lumbar interbody fusion approach or direct lateral transpsoas approach is prone to lumbosacral plexus injury, and intraoperative electromyography monitoring and nerve stimulation study are necessary. L4-5 is the most risky level and may also be avoided to decrease the nerve injury.
- •
Endoscopic surgery and some minimally invasive surgeries may have more complication rates during the learning period. Before starting such surgeries, fellowship training in experienced centers and cadaver dissections should be applied.
Technical complications in spine surgery usually arise from the overaggressive or inadvertent manipulation of eloquent soft tissues or from hardware “failure” (when hardware “fails,” though, the cause of the “failure” usually rests squarely on the shoulders of the surgeon). Other reasons for surgery-related complications include poor patient selection, incorrect diagnosis, ill-chosen approach, inadequate operation (e.g., incomplete decompression of a compressive lesion), and injury to normal anatomic structures.
Surgeons should clearly establish a diagnosis preoperatively. They should also harbor a solid three-dimensional understanding of the pathologic anatomy that is, in part, based on pre- and intraoperative imaging studies. Finally, astute surgeons should use conventional wisdom by “measuring twice, cutting once, and paying meticulous attention to detail.”
General Precautions
Antibiotics
The role of preoperative and perioperative antibiotics in spine surgery remains somewhat controversial. The average infection rate for spine operations is relatively low. Evidence suggests that the incidence of infections may decrease further if antibiotics are administered before the operation. Indeed, a review of the literature supports the use of perioperative antibiotics. Because the most frequently detected organism is a Staphylococcus species, a first-generation cephalosporin is usually satisfactory, unless an allergic propensity is recognized.
Steroids
The role of perioperative steroids in spine surgery is also controversial. The administration of steroids before spinal cord injury confers greater benefit than administration after injury. Although the literature is inconclusive, some surgeons choose to administer 4 to 8 mg of dexamethasone (or an equivalent dosage of methylprednisolone) preoperatively and to continue steroid administration for 24 hours postoperatively in high-risk cases. Because the short-term use of steroids is effective in experimental studies and long-term administration is associated with an increased risk of complications, its use for more than 24 hours seems unnecessary and possibly harmful.
Intubation
Neck positioning during intubation is important in patients with cervical spinal cord compression. C1-2 extension is most commonly associated with intubation and is usually well tolerated by the patient. In patients with severe stenosis at or above the level of C3-4, intubation with fiberoptic guidance, while the patient is awake, with use of local anesthesia, is usually preferred. Preoperative skull or halter traction may facilitate intubation and surgery by providing gentle traction and extension. Some surgeons suggest that patients with severe cervical myelopathy should be positioned before the induction of general anesthesia.
Positioning
Numerous complications are associated with improper positioning. These include air embolism, quadriplegia, peripheral nerve palsies, pyriformis syndrome, posterior compartment syndrome, and excessive bleeding.
Elastic bandages or sequential compression devices should be placed on the lower extremities before the induction of anesthesia. The legs must not be lower than the hips in the sitting position. Great care should be taken in moving the patient to the prone position. Three-point skull fixation in the prone position may be used, although it can be associated with a variety of complications (generally minor).
Extreme rotation, extension, or flexion of the head may cause cervical spinal cord damage. Older patients with cervical spondylotic bars are more prone to this complication. Awake positioning, awake intubation, and evoked-potential monitoring may be helpful. Loss of somatosensory evoked potentials, with neck flexion and recovery with repositioning, has been reported. In patients with severe spinal canal narrowing, the neutral or near-neutral position is preferred.
A stretch injury of the brachial plexus may occur in both the prone and supine positions by abducting the arm greater than 90 degrees. An axillary roll should be used to prevent injury, with the lateral decubitus position when the dependent arm is compressed. The ulnar nerve could be injured because of its superficial position at the elbow. A pad under an extended elbow helps prevent this injury. Elbow extension minimizes exposure of the ulnar nerve to compression. The radial nerve may be injured if the arm hangs over the operating table edge. Padding under the arm may prevent compression injury. Common peroneal nerve injury with resulting footdrop may occur in the supine, the sitting, and the lateral decubitus positions. The superficial location of the nerve at the head of the fibula increases the risk of compression. The superficial femoral nerve may be compressed in the prone position and cause a postoperative transient meralgia paresthetica.
Compression and stretch injury of any nerve is possible during positioning. A general rule of thumb is to select a position that minimizes excessive compression of the extremities and to place appropriate pads beneath potentially exposed nerves. If the patient appears comfortable, nerve injury is less likely. Injury to the lateral femoral cutaneous nerve has been reported to be as high as 20%.
External pressure at the anterior superior iliac spine during prone position is the main reason for the injury of the nerve. The nerve can also be injured at the retroperitoneum by hematoma or traction, as well as during bone graft harvesting at the ventral iliac crest.
Compression of the eyes, with resulting blindness, has been reported with the use of the horseshoe headrest. The head should be positioned in such a way as to prevent it from slipping on the horseshoe headrest. Three-point skull fixation is a viable alternative to the horseshoe, which significantly reduces the incidence of this complication.
Air Embolism
Air embolism is one of the most serious complications encountered. It is predominantly related to operations in which the incision is positioned above the level of the heart. Two precautions to avoid air embolism are suggested: (1) if possible, avoid the sitting position, and (2) monitor the patient at risk meticulously with Doppler ultrasound and end-tidal P co 2 . In such patients, a central venous catheter should be used so that if an air embolism is detected, air can be emergently evacuated from the right atrium. The central venous pressure should be maintained at greater than 10 cm so that the pressure in epidural veins does not decline.
The incidence and clinical importance of air embolism are greater in the sitting position than in other positions. Its incidence has been reported to be as high as 50%. If air embolism occurs, a central venous catheter may be used to withdraw air from the left atrium. At the same time, the surgeon should flood the wound with Ringer solution and inspect and control any open veins with bipolar coagulation. Bleeding bone surfaces should be treated with wax, and the wound should be precisely packed with wet gauze. If signs of air embolism persist, the patient should quickly be placed in a side-lying position, with the right side facing up, to aid the removal of air via the central venous catheter from the right atrium.
If the sitting position or another position that presents a high risk for air embolism is used, nitrous oxide should be avoided as an anesthetic technique. Nitrous oxide diffuses into air-containing cavities (i.e., an air embolism) more rapidly than nitrogen diffuses out. This can result in a temporary increase in the pressure and volume of the cavity, such as an air embolism. This, in turn, compounds the pathologic effect of the embolism.
Paradoxic Air Embolism
A patent foramen ovale, or another right-to-left shunting, facilitates paradoxic air embolism. This is optimally prevented by an accurate preoperative diagnosis with an echocardiogram. Saline injection during echocardiography is suggested for the patients in whom a sitting-position operation is considered. If shunting from the right atrium to the left atrium is encountered, the sitting position should not be used. If the patient is placed in the sitting position, positive end-expiratory pressure should not be used, because it increases the right atrial pressure, which increases the risk of paradoxic air embolism by lowering the pressure gradient between the atria. In the event of a paradoxic air embolus, air may enter the arteries, resulting in coma, quadriplegia, or death.
Doppler and End-Tidal CO 2 Monitoring
Both Doppler and end-tidal CO 2 monitoring are useful in all sitting-position operations. Although the Doppler is not necessarily a vital monitoring technique (i.e., it may show very small volumes of air that do not change P co 2 and vital signs), the surgeon should immediately search for a source of air entrance into the venous system. If a vessel is identified, it should be coagulated. If not, the wound should temporarily be packed with wet sponges. If the end-tidal CO 2 drops, the wound must be packed. If hemodynamic stability is diminished, the wound must be closed.
Intravascular Volume Control
Central and arterial lines should be placed preoperatively if there is a risk of excessive bleeding. If the sitting position is used, adequate hydration of the patient is imperative. If sympathetic tone is diminished or lost as a result of severe spinal cord compression, a central catheter should be placed. The sitting position in such patients is particularly troublesome.
Intraoperative Radiographs
Intraoperative imaging can help determine the correct level of the operation and may provide information about the degree of decompression, realignment, or stabilization.
Incidental Durotomy, Cerebrospinal Fluid Fistula, and Pseudomeningocele
Unintended violation of the dura mater is a common complication of spine surgery. Its incidence has been reported between 3.1% and 14% in different series. Immediately after surgery, a dural violation can cause headache and cerebrospinal fluid (CSF) fistulae. Wound infections are more common in the presence of a CSF fistula. In the long-term, persistent CSF leakage, pseudomeningocele, neurologic deficit, and arachnoiditis are common problems associated with durotomy. Dural violations should be identified and addressed intraoperatively, if possible.
CSF leakage may cause wound dehiscence and subsequent infection. If the fistula is substantial, fluctuations in consciousness may be observed. In fact, an intracranial hemorrhage may ensue. After ventral cervical spine surgery, the fistula may even cause airway obstruction, and after ventral or dorsolateral surgery of the thoracic spine, it may even cause a subarachnoid-pleural fistula.
Fibrin sealants may be used to prevent leakage. They are biologically derived substances consisting of fibrinogen solution and thrombin, with a calcium cofactor. They are used as adhesives to augment the integrity of closure. A retrospective review of fibrin sealants noted that the incidence of postoperative CSF leaks and tension pneumocranium was reduced, as were overall management costs. Nakamura and colleagues have found that autologous fibrin tissue adhesive was superior to that of commercial fibrin tissue adhesive in terms of cost.
CSF cutaneous fistula and pseudomeningocele are end-stage complications of an suboptimally treated dural tear. Because these complications may increase morbidity, cost, pain, and neurologic deficit, they must be treated properly and aggressively. The first priority is to implement CSF diversion (i.e., external lumbar drainage). A percutaneous blood patch may also be used. A revision surgery to repair the dural defect may also be indicated. If a pseudomeningocele is noted and the leakage of CSF persists, it may become necessary to perform dural and myofascial closure via an open reoperation. In difficult cases, a shunt (possibly lumboperitoneal shunt) may also be used for diversionary purposes.
Iliac Crest Graft Harvest Complications
If a graft has been taken from dorsal iliac crest, possible complications include superior gluteal artery injury, sciatic nerve injury, and deep wound infection. Ventral iliac crest harvest complications include donor site herniation, meralgia paresthetica, and pelvic fracture.
Thromboembolism
Venous thromboembolic disease, including deep vein thrombosis and pulmonary embolism, is a serious and potentially life-threatening complication in spine surgery. In one meta-analysis, the prevalence of deep vein thrombosis was 1.09%, and the prevalence of pulmonary embolism was 0.06% following elective spine surgery. The use of pharmacologic prophylaxis significantly reduced the prevalence of deep vein thrombosis relative to no prophylaxis ( P < 0.01).
In a retrospective study conducted by the Scoliosis Research Society, the complication rate in 9692 lumbar microdiscectomies was 3.6%. In anterior cervical discectomy and fusion, the complication rate was 2.4%, and with 10,329 lumbar stenosis decompressions, it was 7%. Overall rates of pulmonary embolism were 1.38%, death due to pulmonary embolism 0.34%, and deep vein thrombosis 1.18%.
Operative Technique
General techniques for complication avoidance include (1) adequate visualization, (2) use of a high-speed drill, (3) use of microcurettes with varying angles and sizes, and (4) adequate positioning. The decision to operate, the approach, the operative technique, and the use of internal fixation and fusion are all important considerations.
Upper Cervical Spine: Complication Avoidance
The reducibility of a subluxation is a critically important consideration for upper cervical spine pathologic processes. If the lesion is reducible, only a dorsal fixation and fusion procedure may be indicated. If the lesion is not reducible, the optimal operation depends on the localization of the compression. For an extradural lesion located between the midclivus and the C3 vertebral body, a transoral approach may provide the trajectory and exposure of choice. If the lesion is intradural, a dorsal or lateral transcondylar approach may be more appropriate. Complex pathologic lesions with lateral extension that are located between the C1 and midcervical levels may involve a transmandibular, transglossal approach. For more limited pathologic lesions located between the lower clivus and the C2 vertebral body, a ventrolateral or ventromedial retropharyngeal approach may be appropriate. In general, if stabilization is required, a dorsal or lateral transcondylar approach with instrumentation should be considered.
Transoral Approach
Cerebrospinal Fluid Fistula
For intradural pathology, a lateral, transcondylar, or dorsal approach is associated with a significantly lower risk of a CSF fistula, compared with the transoral approach. If the latter approach is used and a CSF leak occurs, the dural leaves may be covered with fascia and fibrin glue. A lumbar drain is usually placed postoperatively to treat a CSF fistula.
Severe Tongue Swelling
Intermittent release of the tongue retractor can be used to minimize tongue swelling. Other methods to avoid tongue swelling include the intravenous administration of dexamethasone and postoperative massaging of the tongue to reconstitute venous and lymphatic flow. Patients who are prone to tongue swelling should not be extubated prior to near complete resolution of the swelling.
Hemorrhage
Because blood may accumulate in a deep and narrow wound, meticulous hemostasis is imperative. The careful control of bleeding should be maintained throughout the operation. Injury to the vertebral artery may require clipping or compression occlusion of the artery.
Meningitis
Meningitis is not uncommonly associated with intradural operations. Mouth irrigation with an antibiotic solution may be used preoperatively for 2 to 3 days, after preoperative cultures of the oropharynx are obtained. Intraoperatively, the mouth is swabbed with povidone-iodine (Betadine) solution. The presence of a retropharyngeal abscess is a contraindication to surgery. In patients with meningitis, postoperative antimicrobial therapy is administered.
Retropharyngeal Abscess and Palatal and Pharyngeal Wound Dehiscence
In the presence of late wound dehiscence, a retropharyngeal abscess should be sought. Palatal and pharyngeal wound dehiscence is often related to suboptimal wound closure. If complications develop, they commonly occur 1 week after the operation.
Neurologic Worsening and Instability
Neurologic worsening is often related to inadequate decompression. It may also be caused by loss of alignment or an iatrogenic injury. Injury during surgical positioning or intubation may be avoided by the use of fluoroscopy during positioning and an awake fiberoptic intubation. Instability can be investigated with postoperative dynamic (flexion/extension) radiographs. If instability is present, an occipitocervical fusion may be necessary.
Median Labiomandibular Glossotomy
Median labiomandibular glossotomy is a morbid operation that requires a preoperative tracheotomy or the maintenance of tracheal intubation until the edema of the tongue, palate, and pharynx resolves. If the dura mater is opened, meticulous closure with the application of fibrin glue is useful to avoid CSF fistulae and resulting meningitis. To obtain optimal cosmetic results, the assistance of a plastic surgeon may be appropriate.
Transcervical Retropharyngeal Approach
Hypoglossal nerve injury and carotid artery injury are commonly observed with a transcervical retropharyngeal approach. To avoid intraoperative stroke via embolization, some surgeons use preoperative angiography or Doppler examination of the carotid artery.
Lateral Transcondylar Approach
The most feared complications of the lateral transcondylar approach are vertebral artery injury, air embolism, CSF leakage, and hypoglossal nerve injury. Appropriate decompression and protection of the vertebral artery will minimize the risk of injury. Air embolism may be prevented by the previously mentioned neuroanesthetic techniques. To prevent CSF leakage, an inverted J-shaped incision may provide a more precise closure of the muscle flaps than that achieved with a paramedian vertical incision. CSF fistula is a less common and less serious complication of this procedure, compared with the transoral approach. The hypoglossal nerve injury is another complication of the transcondylar approach. The hypoglossal nerve may be injured during a condylectomy procedure. A preoperative bone window and CT images of the occipital condyle may help localize the hypoglossal canal and its inner and outer orifices.
Subaxial Cervical Spine: Complication Avoidance
Surgical intervention in a patient with a complete traumatic spinal cord lesion and overt instability may be necessary to reestablish spinal stability. Systemic complications of trauma such as hypotension, respiratory difficulties, and metabolic derangements should be well controlled before embarking on a stabilization procedure in such a medically precarious patient.
For cervical spondylotic pathologies, the shape of the cervical curvature should be considered when determining the optimal operative approach. In general, cervical kyphosis is a specific indication for a ventral approach, to avoid postoperative instability and to provide adequate ventral decompression.
The majority of intradural tumors are best approached dorsally, whereas vertebral body tumors are best approached ventrally. A burst or wedge fracture with spinal canal compromise is best approached ventrally. However, severe three-column instability may require both a ventral and a dorsal approach. The indications for the ventrolateral approach are laterally situated tumors, nerve root decompression, and the rarely observed symptomatic vertebral artery compression.
Subaxial Ventral Approaches
Spinal Cord Damage
To avoid spinal cord damage, attention should be paid to (1) patient positioning, (2) illumination and visualization, (3) anesthetic and surgical techniques, (4) position of the surgeon, and (5) evoked-potential monitoring. It is perhaps best to place the patient in a neutral position, although mild extension may aid exposure. Care must be taken to avoid hyperextension, which may cause or exacerbate already existing spinal cord compression. Neurologic examination of the awake patient in a test-extension posture before surgery may help avoid neurologic injury related to positioning.
For optimum illumination and visualization, an operating microscope may help avoid injury to neural and vascular structures, especially in narrow surgical fields, such as those associated with the transoral approach.
An anesthetic technique without paralytic agents may be useful to monitor motor responses from unwanted irritation of the spinal cord or nerve roots. Monopolar cautery should be carefully employed. Instrument placement beneath the lamina in a tight spinal canal should be carefully considered to minimize the incidence of neural injury. Curettes may be used for the last pieces of bone. To avoid injury to the spinal cord and nerve roots, an interbody bone strut or cage should not be pushed into the recess with great force, and its depth should not be greater than 13 mm.
In the case of cervical corpectomy, the surgeon may inadvertently obtain a more extensive decompression on the side opposite the side of the approach. This may be prevented either by working alternately from both sides of the patient or by using the correct angle of view via the use of the operating microscope.
Although evoked-potential monitoring is controversial, some surgeons consider its use helpful.
Cervical Nerve Root Injury
A cervical nerve root may be injured during far-lateral dissection during a ventrolateral approach. Therefore, lateral dissection should be carefully performed dorsal to the anterior tubercle of the transverse process.
C5 Radiculitis
The C5 motor nerve root is most frequently adversely affected by surgery. This may occur in association with both ventral and dorsal operations. Because its mechanism of injury is not well understood, its prevention is also controversial. It has been suggested that excessively wide exposures result in tethering of the nerve roots. Saunders has recommended that the ventral cervical decompression should not exceed 15 to 16 mm in diameter, because an excessive degree of spinal cord displacement may cause traction on a relatively fixed cervical nerve root. The natural history of this complication is spontaneous resolution in most cases.
Dural Tears
Dural tears, CSF fistulae, and pseudomeningoceles may occur, especially in cases of ossification of the posterior longitudinal ligament (OPLL) or severe trauma. Using good illumination, the operating microscope, and diamond-tip burrs in the vicinity of the dura mater may decrease the frequency of these complications. Of note, the posterior longitudinal ligament thins out laterally, and therefore the spinal cord is relatively less protected in this region. The incidence of a CSF leak after anterior cervical OPLL resection has been reported to be between 6.7% and 31.8%. One technique to prevent dural tears is the cervical “floating method” during OPLL decompression. Matsuoka and coworkers have reported the long-term outcomes in 63 patients after anterior cervical decompression using the floating method. The incidence of a CSF leak or fistula with this technique is reported to be 5.1%.
If a violation of the dura mater occurs, repair from a ventral approach is not always possible. A tear may be managed with a piece of fascia with hemostatic gelatin (Gelfoam) and fibrin glue application, with a lumbar drain placed postoperatively (for 48 to 72 hours). If the dura mater has been excised, a Gelfoam and fascia application under the bone graft, without suturing, together with lumbar drainage, may be used. Prophylactic insertion of a lumbar drain before surgery should be considered in high-risk patients.
Major Vessel Injury
Brachiocephalic Vein Injury.
The brachiocephalic vein may bleed during dissection for low cervical and upper thoracic inlet exposures.
Vertebral Artery Injury.
Vertebral artery injury occurs in approximately 1% of cases and is usually caused by lateral use of the cutting burrs. The surgeon should respect the midline. Longus colli muscles and uncovertebral joints are the key structures for the identification of the midline. Because the uncinate processes are the lateral borders of the spinal canal, bony removal or dissection lateral to the uncinate processes may cause damage to the vertebral artery and nerve roots. Therefore, the uncinate processes should be clearly defined, and careful high-speed drilling of the uncinate processes should be limited to just medial to the vertebral artery.
Ventral cervical bone resection should not be carried out wider than 18 to 20 mm. The medial border of the foramen transversarium from one side to the opposite side is 30 mm. An anomalous position of the vertebral artery should be carefully ruled out on the preoperative CT and magnetic resonance imaging (MRI) scans. During the ventrolateral approach, the vertebral artery may be displaced laterally with a narrow-tipped retractor, but not more than 1 to 2 mm.
If an injury develops, it may be controlled by application of Gelfoam or bone wax. However, to see if a pseudoaneurysm has developed, a postoperative angiography should be performed. It may be treated using an endovascular approach.
Carotid Artery Injury.
The risk of carotid artery injury is greater with a ventrolateral approach than with the more common ventromedial approach. To avoid an injury to the carotid artery and internal jugular vein, it is necessary to identify the artery before retraction, to retract the artery laterally without opening its sheath, and to place the blades of the self-retaining retractors under the longus colli muscles. Inspection of the carotid sheath and the jugular vein should be conducted before closure to detect inadvertent injury of these structures.
Dysphagia
Dysphagia after ventral cervical surgery is a known complication of surgery. The reported incidence and prevalence of postoperative dysphagia and risk factors associated with its development vary widely in the literature. In a systematic review of a total of 126 articles, the rates of dysphagia were high just after surgery and declined at 1 year to a range of 13% to 21%. Risk factors were multilevel surgery and female gender.
Esophagus and Trachea Injury
Injury to the esophagus is a rare but life-threatening complication that may lead to disastrous consequences, including septicemia, mediastinitis, pneumonia, and meningitis. Some authorities suggest the use of finger dissection, rather than a sharp dissection, below the superficial cervical fascia. The surgeon should be aware of any preoperative problems with esophageal dysmotility (observed in 10% of patients, mostly in the elderly). In addition, he or she should avoid injury to the pharyngeal muscles during dissection in the upper cervical region. During lengthy operations, it may be necessary to release the medial blades regularly to avoid esophageal necrosis. The surgeon should inspect the esophagus and the trachea before closure to detect inadvertent injury to these structures. Graft dislocations or implant failure with loosened screws may also cause perforation of the esophagus.
Fiberoptic endoscopy is usually the procedure of choice to detect injury to the esophagus or trachea. Esophageal motility films may also help in the diagnosis. If leakage from the wound arouses suspicion a few days after surgery, one can simply have the patient drink methylene blue and look for that color in drainage fluid.
Broad-spectrum antibiotics and primary repair form the basis of management in early cases. In delayed cases, however, it may not be possible to place primary sutures in the esophagus. In case of a perforation with abscess formation, incision and drainage, broad-spectrum antibiotics, and opening a gastrostomy should be instituted. If the infection has subsided, suturing and covering the defect with a myofascial flap may be applied.
Recurrent Laryngeal Nerve Injury
Hoarseness after surgery is usually related to traction of the recurrent laryngeal nerve. It occurs in 3% to 11% of patients. It is usually transient. The recurrent laryngeal nerve passes under the subclavian artery on the right side and under the aorta on the left side. Although the right recurrent laryngeal nerve was thought to be more susceptible to stretch as midline structures are retracted, a study comparing the incidences of recurrent laryngeal nerve injury in right- and left-sided surgeries showed that there is no difference in incidence of recurrent laryngeal nerve injury with the side of surgical approach. The same study also showed that reoperative surgery causes significantly more injuries than primary surgery.
Although recurrent laryngeal nerve palsy after ventral cervical spine surgery was thought to be the result of direct injury to the nerve, no data support this hypothesis. Apfelbaum and colleagues have shown that the most common cause of vocal cord paralysis after ventral cervical spine surgery is compression of the recurrent laryngeal nerve within the endolarynx. We recommend monitoring the endotracheal cuff pressure and release after retractor placement. In the series of Apfelbaum and colleagues about instituting this maneuver, the rate of temporary paralysis has decreased from 6.4% to 1.69%.
Excessive retraction of the medial structures may result in postoperative stridor, hoarseness, and dysphagia. A rare complication is an esophageal fistula. To prevent excessive medial retraction, the following suggestions are made: (1) rostral and caudal dissection should be greater than is needed, (2) retraction should be relaxed on an hourly basis, and (3) the medial retractor should be inserted under the longus colli muscles, if possible.
Hypoglossal Nerve Injury
The hypoglossal nerve runs downward, lateral to the internal and external carotid arteries. Lateral to the occipital artery, the nerve usually turns forward a little above the level of the hyoid bone to disappear deep to the suprahyoid muscles. As it turns around the occipital artery, it gives off the superior root of the ansa cervicalis. Twelfth cranial nerve injury is rare, but possible, during high cervical dissections. Knowledge of its anatomy and course should minimize its injury.
Thoracic Duct Injury
The thoracic duct is on the left side. Because this structure is located laterally, it is uncommon to injure the thoracic duct, at least in exposures medial to the sternocleidomastoid muscle.
Sympathetic Chain Injury
Injury to the sympathetic chain is associated with an ipsilateral Horner syndrome. It is usually attributed to dissection of the longus colli muscles too far from the midline. They are easily injured during the ventrolateral approach. The sympathetic chain is located between the carotid sheath and the longus colli muscles in the midcervical region. Lateral retraction of the longus colli muscle during transverse foramen or uncovertebral joint exposition at the lower cervical levels may injure the sympathetic chain. Horner syndrome, visual symptoms, and an odd sense over the face may result. To avoid this complication, it is necessary to mobilize the sympathetic chain and longus colli muscle over the length of the exposure and insert the medial retraction blade after the lateral blades.
Excessive Bleeding
Excessive bleeding may arise from bone, epidural space, and posterior longitudinal ligament bleeding. Because extensive bone waxing may prevent fusion, it is often better to use Gelfoam, even for bone bleeding. Bipolar coagulation and Gelfoam may be useful to control bothersome epidural bleeding. Venous bleeding from the plexus around the vertebral artery is a common nuisance. Care must be taken to avoid injury to the vertebral artery during control of venous bleeding.
Postoperative Hematoma
To prevent postoperative hematomas, suction drains may be employed. The use of drains for this purpose, however, is controversial.
Graft Bed Preparation
If a fibular graft is to be used, the ventral width of the decompression should be no more than the greatest diameter of the graft to ensure a good lateral bony approximation. This width is not usually necessary for the iliac crest graft, which may be fashioned to fit the decompression site.
Graft Dislocation
Allografts have a higher incidence of pseudarthrosis and an associated small risk of transmitting viral infections. Although autografts may also be complicated by pseudarthrosis, they are preferred in most instances. The graft should not be placed deeper than 13 mm. It should distract the intervertebral space approximately 2 mm and be recessed approximately 3 mm. Excessive end plate removal may increase the incidence of graft subsidence.
Graft dislocation may occur ventrally or dorsally. Dorsal dislocation is rare but more serious, because it may cause significant compression of the spinal cord. Partial graft extrusion is of little consequence and usually does not require treatment. Three technical considerations may help prevent graft dislocation:
- 1.
Contour the graft into a shape that fits snugly into the mortise of the graft bed. The graft should be recessed so that the ventral cortical bone is a few millimeters dorsal to the ventral vertebral body. This border, however, should not be confused with the ventral vertebral osteophytes. An obsessive tailoring of grafts is appropriate.
- 2.
Placement of a ventral cervical plate may help avoid graft dislocation.
- 3.
Postoperative bracing may decrease the risk of graft dislocation.
Graft Pseudarthrosis
The pseudarthrosis rate, using different graft techniques, varies from 0% to 26%. The risk of pseudarthrosis increases if more than one level is fused. If one long piece of cortical-cancellous graft or cortical bone is used, however, the risk is lower. It should be emphasized that the presence of pseudarthrosis does not necessarily compromise the clinical results of surgery.
Vertebral Avascular Necrosis
Avascular necrosis of the vertebrae is encountered with the use of grafts at individual interspaces. The Cloward technique for a ventral cervical fusion at two adjacent levels has been associated with avascular necrosis. If a multilevel fusion is needed, Cloward in fact suggested that a Smith-Robinson graft may be inserted at one disc level, and a bone dowel may be inserted at an adjacent level.
Ventral Plating Complications
Screw breakage, plate breakage, esophageal erosion, pain, and difficulty swallowing may complicate the results of ventral plating. Many surgeons do not advocate placing a screw into a graft, for fear that the screw may dislodge or weaken the graft.
Most patients should improve neurologically after surgery. If no improvement occurs, but is expected, the use of CT or MRI is prudent. The most likely surgically related reason for lack of improvement is an inadequate decompression. It is common for a right-handed surgeon operating from the right side to leave residual compression on the right side. Another cause of failure to achieve neurologic improvement may be OPLL, which may easily be overlooked on the preoperative MRI scan. Obtaining a preoperative CT scan is helpful in ruling out the possibility of OPLL.
Subaxial Dorsal Approaches
Neurologic Deterioration
Patients with cervical kyphosis are poor candidates for cervical laminectomy. A lordotic or neutral posture is preferred. Instrumentation under the lamina in the cervical region can cause neurologic injury. The predominant risk during the keyhole foraminotomy is direct nerve root trauma. To avoid this complication, dissection should only be performed from the axilla of the root.
Lateral mass screw fixation may also cause nerve root injury and, occasionally, vertebral artery injury. With transarticular screw fixation, if a vertebral artery injury is detected after a screw is placed, a second screw on the contralateral side should not be placed. The screw causing the vertebral artery injury may be left in place. It may effectively serve to tamponade vertebral artery bleeding. Residual bleeding may be effectively managed with oxidized cellulose (Surgicel).
Postoperative Instability and Kyphosis
Kyphosis is a late complication after cervical laminectomy without fusion. Respect for the facet joints and joint capsules is necessary to prevent postlaminectomy instability. Two additional precautions may be taken to prevent this complication: (1) the use of laminoplasty instead of laminectomy may decrease the risk of instability (although this has not been proved); and (2) lateral mass fixation and fusion may be carried out to prevent deformity, minimize instability, and decrease the movement associated with the degenerative process.
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
