6. Spine MCQs

The proposed mechanisms by which steroids such as methylprednisolone are thought to prevent neurologic deterioration by limiting secondary insult, include: decreasing the area of ischemia in the cord, reducing TNF-alpha expression and NF-kB binding activity, decreasing free radical oxidation and thus stabilizing cell and lysosomal membranes, and checking the influx of calcium into the injured cells, thus reducing cord edema.

DISCUSSION: The atlanto-occipital joint is inherently unstable and would easily dislocate without the supporting ligaments. The apical ligament attaches to the basion and tip of the dens but does not provide adequate stability to the joint. Werne demonstrated that dividing the tectorial membrane and the alar ligaments resulted in gross joint instability. The anterior longitudinal ligament turns into the anterior atlanto-occipital membrane. This is called a membrane rather than a ligament because it is not strong enough to support these two structures.

DISCUSSION: Incomplete cord syndromes have variable neurologic findings with partial loss of sensory and/or motor function below the level of injury. Incomplete cord syndromes include the anterior cord syndrome, the Brown-Séquard syndrome, central cord syndrome, and posterior cord syndrome. Central cord syndrome is characterized with greater motor weakness in the upper extremities than in the lower extremities. The pattern of motor weakness shows greater distal involvement in the affected extremity than proximal muscle weakness. Anterior cord syndrome involves a variable loss of motor function and pain and/or temperature sensation, with preservation of proprioception. The Brown-Séquard syndrome involves a relatively greater ipsilateral loss of proprioception and motor function, with contralateral loss of pain and temperature sensation. Posterior cord syndrome is a rare injury and is characterized by preservation of motor function, sense of pain, and light touch, with loss of proprioception and temperature sensation below the level of the lesion. Spinal shock is the period of time, usually 24 hours, after a spinal injury that is characterized by absent reflexes, flaccidity, and loss of sensation below the level of the injury.

DISCUSSION: This patient has bilateral jumped facet joints at C6-7. Although MR imaging is useful for revealing disk herniations, cord injuries, and bony fragments, early closed reduction to restore anatomic alignment may be attempted prior to MR imaging because reduction will decrease pressure on the cord. There have been reports of catastrophic outcomes with closed reduction in patients who are intubated when disk fragments are pushed into the spinal cord. Consequently, closed reduction should be attempted only in awake and cooperative patients for whom neurologic status monitoring is possible. MR imaging is generally performed after reduction is attempted (successful or not).

DISCUSSION: C1-C2 transarticular screw fixation is 10-fold stiffer than wiring constructs, particularly in rotation; eliminates the need for postsurgical halo use; and is associated with reported fusion rates to a maximum of 100% for bilateral screws and 95% for unilateral fixation. All of the other fusion techniques mentioned are associated with a pseudarthrosis rate of at least 30%.

With C1-C2 transarticular screw fixation, the following structures are potentially at risk: vertebral artery, spinal cord, occiput-C1 joint, and hypoglossal nerve. The vertebral artery is most vulnerable to injury with drill misdirection or anatomic variations in the vertebral foramen. The hypoglossal nerve may be injured if the drill, tap, or screw passes too far anterior to the lateral mass of C1. The occiput-C1 joint may be injured if the screw trajectory is too cephalad or cranially directed; however, this scenario is very unlikely because the exposure tends to direct the screw into a caudally inclined direction. This caudal orientation has the potential to cause vertebral artery injury, especially in patients who have a large vertebral foramen in the lateral mass of C2 because of erosions (rheumatoid arthritis) or anatomic variation.

The CT scans reveal an occipital-cervical dissociation with subluxation of the occipitocervical joints bilaterally. Definitive management should consist of an occipital-cervical fusion with instrumentation. Immobilization in a Philadelphia collar is inadequate for this highly unstable injury, and halo immobilization, while affording adequate temporary immobilization, is not appropriate definitive management for this ligamentous injury.

DISCUSSION: It is not uncommon for patients with ankylosing spondylitis to sustain extension-type fractures, most typically of the cervicothoracic junction. These fractures can appear nondisplaced or minimally displaced initially, making them difficult to diagnose. Because there is no mobility between vertebrae, fractures tend to occur more like those of a transverse fracture of a long bone. In addition, the vertebral bodies are vascular and their canals are relatively enclosed, making them vulnerable to epidural bleeding. The MRI scan reveals an epidural hematoma located posteriorly on the cord; therefore, the treatment of choice is surgical evacuation and a posterior laminectomy. Because of the intrinsic instability of such fractures at the time of the laminectomy, internal fixation and stabilization with a posterior fusion is warranted.

The nerve roots of S2-5 are positioned dorsally and in the midline relative to the L5 and S1 nerve roots. The L5 nerve root is located lateral to S1 as it prepares to exit under the L5 pedicle. The S1 nerve root is located lateral and ventral to the S2-5 nerve roots.

Ackland and associates demonstrated that the failure to achieve early spinal clearance in an unconscious blunt trauma patient predisposed the patient to increased morbidity secondary to the prolonged use of cervical immobilization. They demonstrated that the four significant predictors of collar-related ulcers were ICU admission, mechanical ventilation, the necessity for cervical MRI, and the time to cervical spine clearance and collar removal. The risk of pressure-related ulceration increased by 66% for every 1-day increase in Philadelphia collar time and this highlights the need for definitive C-spine clearance.

The change noted is focal and confined to the cortex, sparing the opposite side, both lower extremities, and the subcortical waveforms, making all the choices unlikely with the exception of carotid compression with focal cortical ischemia. This may be associated with poor collateral flow from the opposite hemisphere due to an incomplete circle of Willis.

The most predictable positive outcome from spinal surgery due to a cauda equina syndrome is early surgical intervention before any significant neurologic deficit develops. Meta-analysis studies demonstrate that surgical intervention more than 48 hours after the onset of cauda equina syndrome show an increased risk for poor outcomes.

DISCUSSION: This patient has a right-sided C5-C6 disk herniation causing C6 radicular symptoms in the right upper extremity. Studies have shown that both ACDF and posterior foraminotomy confer similar results in terms of pain relief and functional outcome. Patients treated with posterior foraminotomy are at higher risk for neck pain and recurrence of radiculopathy at the same level. Those who receive ACDF are at higher risk for occurrence of radiculopathy at an adjacent level. RECOMMENDED READINGS: Rao RD, Currier BL, Albert TJ, Bono CM, Marawar SV, Poelstra KA, Eck JC. Degenerative cervical spondylosis: clinical syndromes, pathogenesis, and management. J Bone Joint Surg Am. 2007 Jun;89(6):1360-78. Bolesta MJ, Gill K. Acute neck pain and cervical disk herniation. In: Spivak JM, Connolly PJ, eds. Orthopaedic Knowledge Update: Spine 3. Rosemont, IL: American Academy of Orthopaedic Surgeons; 2006:227-234.

Cervical spinal stenosis is a contraindication to participation in collision and contact sports. Previously, the risks of permanent quadriparesis from cervical spinal stenosis were thought to be unclear and athletes with cervical spinal stenosis were often allowed to play contact sports. In 1996, Torg and associates reported that developmental narrowing of the cervical canal in a stable patient does not appear to predispose an individual to permanent catastrophic neurologic injury and therefore should not preclude an athlete from participation in contact sports. However, the current understanding is that the actual risks of permanent neurologic injury from cervical stenosis are significant. The Torg ratio was previously used for diagnosis but is more recently thought to be of low predictive value as reported by Cantu. Current methods for diagnosis of cervical spinal stenosis rely on MRI and CT. Current diagnosis is based on comparisons of measurements with normal values. A cervical canal of less than 13 mm is considered stenotic whereas a diameter of less than 10 mm is considered absolute stenosis as reported by Crowl and Kong. This patient has symptomatic stenosis and should not be cleared for contact sports. A neck roll will not prevent neurologic injury in the presence of cervical spinal stenosis. Electrodiagnostic studies are not likely to add any additional significant findings with central canal stenosis. Cervical traction is not of value in the long-term. Epidural steroid injections or a methylprednisolone dose pack are not of value in this situation.

The CT scan reveals a right-sided lateral disk protrusion at L3-4 that has been symptomatic for more than 4 months despite appropriate nonsurgical management. Relative surgical indications include persistent radiculopathy despite an adequate trial of nonsurgical management, recurrent episodes of sciatica, persistent motor deficit with tension signs and pain, and pseudoclaudication caused by underlying stenosis. Whereas studies have shown improvement in patients with sciatica from a lumbar disk herniation treated either nonsurgically or surgically, those undergoing surgical treatment had an overall greater improvement of symptoms.

The treatment of thoracolumbar burst fractures has evolved over the years. In the absence of a neurologic deficit or a posterior ligamentous complex injury, nonsurgical treatment is as effective as surgery. The degree of spinal canal compromise is not a risk factor for neurologic symptoms. Similarly, although kyphosis may be a marker of more significant injury, the degree of kyphosis does not correlate with chronic pain. In the setting of a burst fracture, MRI can be used to evaluate the integrity of the posterior ligamentous complex. Polytrauma may be considered a relative indication for surgical intervention in the setting of a stable burst fracture.

Of the incomplete spinal cord injuries, Brown-Sequard syndrome has the best prognosis for ambulation. Central cord syndrome has a variable recovery. Anterior cord syndrome has the worst prognosis, with motor recovery rare below the level of the injury.

There are several reasons to obtain an MRI of the entire spinal cord of this patient to evaluate for abnormalities. These include her young age and the presence of a left-sided curve. For juvenile scoliosis patients with more than a 20-degree Cobb angle, there is an approximately 20% prevalence of a neurologic abnormality. Therefore, recommendations for work-up include an MRI scan of the entire spine.

DISCUSSION: NASCIS 2 established the recommended doses of methylprednisolone for spinal cord injury. This included an initial bolus of 30 mg/kg over 1 hour, followed by an infusion of 5.4 mg/kg/h for an additional 23 hours. If the injury was more than 8 hours old, the methylprednisolone was not recommended. NASCIS 3 changed the dosing schedule based on the time from injury. If the time from injury to treatment was less than 3 hours, the standard protocol was followed (30 mg/kg bolus followed by 5.4 mg/kg/h for 23 hours). If the time from injury to treatment was between 3 and 8 hours, the infusion was continued at 5.4 mg/kg for an additional 23 hours (48 hours total). In this situation with a time of injury 7 hours ago, treatment should consist of a bolus and further steroid therapy for 48 hours.

DISCUSSION: The posterior atlanto-dens interval represents the space available for the spinal cord and a distance of less than 14 mm is predictive of neurologic progression, thus warranting consideration for fusion, even in the absence of symptoms.