6. Spine MCQs

The use of intraoperative neuromonitoring is expanding. Changes in monitoring are concerning for the possibility of a neurologic injury; however, several other factors can alter signals, including hypotension, changes in anesthesia depth and medications, the use of paralytic agents, and technical issues such as leads falling out or becoming disconnected. If a change in neuromonitoring signals is noted, these factors should be checked first to rule out false-positive findings. If this does not correct the problem, the wound should be explored to ensure there is no compression on the neural elements.

Symptoms of thoracic disk herniation may present in one of three distinct patterns: axial pain, radicular pain, or myelopathy. This patient demonstrates obvious upper motor neuron signs, including lower extremity hyperflexia, clonus, and a positive Babinski sign; therefore, the next most appropriate step is a MRI scan of the thoracic spine. Thoracic disk herniations presenting with axial pain usually involve the mid to lower thoracic region. The pain is usually worsened with activity and improved with rest. Radicular pain syndromes are usually described as starting in the back and radiating anteriorly in a band-like pattern to the anterior chest wall. The pain and paresthesias generally follow a dermatomal distribution. The MRI scan of this patient's cervical spine demonstrates spondylotic changes; however, she denied neck or upper extremity symptoms and more importantly, has a normal neurologic examination. There are degenerative changes involving the lumbar spine, but these cannot explain the upper motor neuron findings.(SBQ12SP.39) Which of the following is associated with increased risk of surgical site infection following lumbar spinal decompression?Review TopicUse of intra-wound vancomycin powderHair removal by clipping at the time of surgeryUse of morphine nerve paste applied to the dura after spinal decompressionSkin preparation with an alcohol-based prep solution rather than povidone iodineFailure to use chlorhexidine gluconate wash the night prior to surgeryThe use of morphine nerve paste applied to the dura after decompressive spine surgery has been used in an effort to mitigate postoperative pain but has been associated with epidemic levels of surgical site infection.Surgical site infection risk is modulated by a myriad of factors, both host factors and perioperative factors. Perioperative strategies to reduce infection that have been shown to be effective include: 1) hair removal by clipping (not shaving) at the time of surgery, 2) use of an alcohol based skin preparation agent, 3) use of perioperative prophylactic antibiotics, 4) limiting operating room traffic from OR personnel.Kramer et al. did a retrospective analysis of 148 patients who underwent laminectomy in order to identify risk factors for infection in the context of a sudden increase in infections. Regression analysis showed that use of morphine paste resulted in an 18-fold increase in the risk of surgical site infection. 17 of 148 had developed infection during the epidemic period, compared to 15/995. Cultures were positive in 10 of 16 cases; 7 of these involved skin flora. Histological exam showed foreign body reaction.Devin et al. did a multi-center analysis of patients undergoing spine surgery at seven spine centers to determine whether there was a difference in infection risk based on whether or not intra-wound vancomycin was used. They analyzed 2056 patients, of whom 47% had vancomycin used in their wounds. The risk of surgical site infection was higher in those patients that did not have vancomycin (relative risk 2.5).Incorrect answers:

DISCUSSION: The string passes under the ligamentum flavum as it runs from the posterior aspect of the vertebra above to the inferior aspect of the vertebra below in the sagittal midline. This is an important structure in diskectomy and in posterior approaches to the thoracolumbar spine and neural elements. It is rarely visualized in its entirety because typical exposures provide only a limited view. REFERENCE: Frymoyer JW (ed): The Adult Spine: Principles and Practice. New York, NY, Raven Press, 1991, vol 2, p 1465.

Epidural abscesses are potentially devastating. Nonsurgical care may be chosen for select patients. A baseline failure rate of 8.3% increases based on patient risk factors, which include a history of IV drug abuse, diabetes, age older than 65, CRP level higher than 115, WBC level higher than 12.5, and Staphylococcus aureus as the causative organism. Immunosuppression and abscess size are not significant risk factors for failure of nonsurgical care. Nonsurgical care may be regarded as "failed" if there is worsening of a patient's neurologic status. When nonsurgical care fails, delayed surgery is less successful at restoring motor function (vs early surgery).

Scoliotic deformities in patients with NF1 are often dysplastic with short, angular curves. Posterior arthrodesis is made more difficult by the presence of kyphosis and of weak posterior elements caused by dural ectasia. Combined anterior and posterior spinal arthrodesis is generally preferred for progressive dysplastic curves to maximize deformity correction and to decrease the risk of pseudarthrosis. Anterior fusion may also prevent crankshaft phenomenon in young children. Brace treatment is not effective for large, rigid, or dysplastic curves.

A facet dislocation that cannot be reduced in an alert, awake patient with some preservation of cord function requires MRI to evaluate the disk prior to a reduction under anesthesia. The presence or absence of a disk herniation must be assessed, as this factor may influence the method of reduction.

A player who has an acute cervical disk herniation should not be allowed to return to play until the acute phase is over. Certain players with large herniations may require surgery before returning to play to eliminate the risk of disk-related stenosis and cord compression.

The patient has an established nonunion of the ischial tuberosity. Avulsion fractures of the pelvis are generally treated with rest and symptomatic treatment. Avulsion fractures of the ischial tuberosity are the most prone to nonunion. Most patients have few symptoms but some have trouble sitting and returning to sports. Excision of the avulsed fragment or open reduction and internal fixation are indicated for painful nonunions of the ischial tuberosity.

Figure B shows a multilevel laminoplasty, which can be used in the treatment of cervical myelopathy. The spinal cord is decompressed by increasing the anterior to posterior dimension of the spinal canal.The treatment of cervical myelopathy is dictated by the number of stenotic levels, sagittal alignment of the spine, and more recently attempt to retain motion. Anterior cervical discectomy and fusion (ACDF) is used for one or two level disease with pathology localized to anterior spine. Posterior decompression and fusion is typically used for disease at more than two levels and is contraindicated with kyphosis greater than 13 degrees. Lamninoplasty and cervical disc arthroplasty are thought to be motion-preserving alternatives, although there can be unintended loss of motion with both techniques. The open door laminoplasty technique involves the use of a suture anchor or small plate to maintain the opening on one side while the french door technique involves hinges bilaterally and opening in the midline.Emery reviewed the diagnosis and management cervical myelopathy. Surgical management is advocated for patients with functional impairment. Depending on location and extent of pathology, anterior procedures may require corpectomy and use of strut grafting.Gerard et al. reviewed techniques of surgical management of myelopathy. They describe a minimally invasive posterior decompression using a tubular retractor system. Patients are carefully selected and should have less than 3 levels of disease, no evidence of instability, and normal lordosis.Figure A is a T2 sagittal MRI image showing multilevel cervical stenosis. Figure B is lateral radiograph of a patient who underwent multilevel laminoplasty. Illustration A shows the open door technique.Incorrect

The arrow is pointing to a cystic-appearing structure with high signal intensity on T2-weighted image sequencing. It appears to be contiguous with the hypertrophied right facet joint, which appears to also have high signal intensity. The mass significantly narrows the right lateral recess. The high signal intensity suggests that this is a fluid-filled mass. In addition, the facet joints are degenerative and there is a very mild degree of anterolisthesis on the sagittal image. These findings make a lumbar synovial cyst the most likely diagnosis. Most lumbar juxtafacet cysts are observed at the L4-5 level, extradurally and adjacent to the degenerative facet joint. They may contain synovial fluid and/or extruded synovium. Presentation is indistinguishable from that of a herniated disk. The etiology of spinal cysts remains unclear, but there appears to be a strong association between their formation and worsening spinal instability. They occasionally regress spontaneously and may respond to aspiration and injection of corticosteroids, though there is a high recurrence rate with nonsurgical management. Synovial cysts resistant to nonsurgical management should be treated surgically. If the patient’s symptoms can be attributable to radicular findings, a microsurgical decompression that limits further destabilization should suffice. However, if there is significant low back pain attributable to spinal instability, decompression and fusion remains an appropriate option.

This clinical presentation is most consistent with vascular claudication.Vascular claudication refers to the pain, aching or fatigue of the muscles of the buttocks, thigh and/or calf that occurs with exertion, and is related to a failure to meet muscular oxygen requirements, usually caused by peripheral vascular disease impeding blood flow to the peripheral muscles.Neurogenic claudication is the classic symptom caused by lumbar spinal stenosis. Neurogenic claudication classically presents with bilateral buttock pain with upright activities, but seems to improve by postural changes that flex the lumbar spine. These posture changes are thought to increase the cross sectional area of the central canal, which relieves pressure on the affected area.Issack et al. reviewed degenerative lumbar spinal stenosis. They state that patients with vascular claudication will have similar symptoms of leg cramping, whether ambulating or riding a stationary bicycle. In comparison, patients with neurogenicclaudication have diminished symptoms of claudication while positioned seated.Young et al. reviewed the use of lumbar epidural/transforaminal steroids for managing spinal disease. They report that two thirds of acute low back pain episodes resolve within 7 weeks, so the utility and practice patterns regarding the timing and number of epidural/transforaminal steroid injections is usually based on expert opinion, rather than high level research evidence.Illustration A shows an angiogram of a patients with normal (left) vs abnormal (right) arterial vasculature. Illustration B shows the typical MRI of a patient with spinal stenosis.Incorrect

DISCUSSION: The long-term effect of transient quadriplegia is unknown. Based on a history of one brief episode of transient quadriplegia and normal examination and MRI findings, the risk of permanent spinal cord injury with a return to play is low. There is a risk of recurrent episodes of transient quadriplegia after the initial episode.

DISCUSSION: Prolonged use of steroids is associated with compression fractures with minimal trauma. Indications for radiography with acute low back pain include possible tumor, fracture, infection, or cauda equina syndrome.

There are currently no official guidelines on the appropriate use of neuromonitoring in spine surgery. In general, use of neuromonitoring is at surgeon discretion and often is based on the surgeon's perceived risk for neurologic injury during surgery and medicolegal concerns.

The MRI scan reveals a L4-L5 foraminal disk herniation originating from the L4-5 disk space that has migrated up into the foramen, compressing the left L4 nerve root. There is normal distribution of the roots in the cerebrospinal fluid, excluding arachnoiditis as a diagnosis, and disk herniation in this location would not result in cauda equina syndrome or myelopathy.

The radiograph shows a displacement of C5 on C6 of approximately 25%. The CT scan shows a perched facet at C5-6. There is no evidence of a facet fracture. A bilateral facet dislocation would show a displacement of more than 50%.

The patient has signs and symptoms of both lumbar spinal stenosis and myelopathy, also known as tandem stenosis. The next most appropriate step is a cervical spine MRI.While 79% of patients with cervical myelopathy will have at least one sign on physical exam, the absence of a one or more signs such as a Babinski reflex or a Hoffman's sign does not rule out the diagnosis of myelopathy. Tandem cervical and lumbar stenosis occurs in between 5 and 25% of patients with lumbar stenosis, and because of the stepwise progressive nature of myelopathy, it is critical not to miss this diagnosis.Rhee et al. found that the sensitivity and specificity of specific physical exam findings varies in patients with myelopathy. Overall 79% of patients will have at least one physical exam sign of myelopathy, with biceps hyperreflexia (62%) and the Hoffman sign (59%) being the most sensitive. Classic upper motor neuron findings in the lower extremity such as an upward Babinski reflex (13%) and clonus (13%) are not sensitive.Lee et al. performed a cadaveric study of 440 specimens to identify the overall prevalence of stenosis in the population. They found 5.4% of the specimens had cervical stenosis and 5.9% had lumbar stenosis. A total of 0.9% had both cervical and lumbar stenosis.Bajwa et al. evaluated over 1,000 skeletal remains to determine if tandem stenosis (concomitant lumbar and cervical stenosis) is due to an increased risk of disc degeneration or a congenitally small vertebral canal, and they concluded that tandem stenosis is likely due to a congenitally small vertebral canal in both the cervical and lumbar spine.Figure A and B demonstrate an AP and lateral radiograph of the lumbar spine respectively. A degenerative L4/5 spondylolisthesis is present.Incorrect answers:

Sagittal balance is becoming increasingly important. PI should be roughly equal to LL. A PI larger than the LL has been associated with a higher incidence of PJK. PJK also is associated with larger sagittal balance corrections. Additional risk factors include higher presurgical thoracic kyphosis, higher postsurgical lordosis, osteoporosis, fusion below L2, and older (greater than 65 years old) patient age.

DISCUSSION: Afferent pain fibers to the lumbar facet joints arise from the medial branch nerves originating from the next two cephalad levels. Therefore, innervation of the L3-L4 facet joint arises from the L2 and L3 medial branch nerves. This effect should be taken into account when considering a medial branch block or facet denervation. The medial branch nerve arises from the dorsal ramus of the exiting nerve root. REFERENCES: Nade SL, Bell E, Wyke BD: The innervation of the lumbar spinal joint and its significance. J Bone Joint Surg Br 1980;62:255-261. Kornick C, Kramarich SS, Lamer TJ, et al: Complications of lumbar facet radiofrequency denervation. Spine 2004;29:1352-1354.

DISCUSSION: The natural history of cervical myelopathy has been described by Lees and Turner as exacerbations of symptoms followed by often long periods of static or deteriorating function (or very rarely improvement). This stepwise pattern of decreasing function has been corroborated by Clarke and Robinson. These authors described long periods of stable neurologic function, sometimes lasting for years, in about 75% of their patients. In the majority of the patients, however, the condition deteriorated between quiescent streaks. About 20% of their patients showed a slow, steady progression of symptoms and signs without a stable period, and 5% had rapid deterioration of neurologic function. REFERENCES: Emery SF: Cervical spondylotic myelopathy: Diagnosis and treatment. J Am Acad Orthop Surg 2001;9:376-388. Lees F, Turner JA: The natural history and prognosis of cervical spondylosis. Brit Med J 1963;2:1607-1610. Clarke E, Robinson PK: Cervical myelopathy: A complication of cervical spondylosis. Brain 1956;79:486-510.