Herniated disks in the lumbar spine are the leading cause of patient visits to spinal surgeons in the United States. Although magnetic resonance imaging (MRI) is the diagnostic test of choice in patients with a herniated disk, plain radiographs can provide important information and should remain a standard part of the diagnostic workup in any patient indicated for revision spine surgery.
This article describes a case of a 36-year-old man with a >6-month history of worsening lumbar radiculopathy who was diagnosed with lumbar disk herniations on the basis of MRI alone and underwent 2 unsuccessful attempts at microdiskectomy at another institution. Further workup by the senior author (A.C.H.), which included initial plain radiographs followed by computed tomography, demonstrated a large disk herniation with a markedly calcified annulus as the continuing source of neurologic compression. The patient underwent revision lumbar decompression with attention being paid to the removal of the calcified annulus and disk material that resulted in complete resolution of his symptoms.
Although MRI is the diagnostic test of choice in the evaluation of spinal pathology, plain radiographs can provide important additional information that can be vital to the successful outcome of patients undergoing revision spinal surgery.
Acute low back pain with or without radiculopathy is one of the leading health problems in the United States, and it is the leading cause of disability in people younger than 45 years. The cost of low back pain (evaluation and treatment) is billions of dollars annually, not including the time lost from work.1 Various studies consistently demonstrate that clinicians vary widely in what diagnostic imaging they obtain for the assessment of low back pain, despite established guidelines.2-4
The guidelines most commonly cited are those created by the Agency for Health Care Policy and Research of the US Department of Health and Human Services for the management of patients with acute low back pain.5 Included are recommendations on the use of radiographs. Radiographs are not indicated in patients presenting within 6 weeks of the onset of symptoms, unless red flags are present for fracture, tumor, or infection. Red flags for spinal fracture include major and minor trauma, prolonged steroid use, osteoporosis, and age older than 70 years. Red flags for tumor or infection include age older than 50 years or younger than 20 years, history of cancer, fever, chills, unexplained weight loss, risk factors for spinal infection (intravenous drug use, immunosuppression), or pain that is worse when supine or at night. These guidelines were recently revalidated by the American College of Radiology.6
Despite wide consensus, spine radiographs are labeled as having low diagnostic yield.7 Augmenting this belief are the recent advances in magnetic resonance imaging (MRI), leading to faster and less expensive examinations. Thus, the use of MRI instead of radiographs as the initial imaging for low back pain has become more common, especially considering that randomized controlled trials have suggested that substituting MRI for radiographs is likely safe and that such replacement has resulted in no long-term difference in poor outcomes.8,9
This article describes a case of low back pain in which MRI was obtained instead of radiographs and used to guide operative intervention, resulting in a poor initial outcome.
A 36-year-old man presented to another institution with a 6-week history of lower back and leg pain, with severe numbness, tingling, and weakness in the right leg. Physical examination revealed that he had paraspinal spasm in the lumbosacral region with limited range of motion (ROM), including lateral bending and rotation. Straight leg raise was positive on the right side at 25° and positive on the left side at 45°. Heel toe walking was abnormal with mild guarding on the right. He had received physical therapy, which he reported was temporarily beneficial. Magnetic resonance imaging performed at that time indicated disk herniations at the L4-L5 and L5-S1 levels with impingement of the L5 and S1 roots (Figure 1). Because of the severe pain and clear evidence of disk herniation, an L4-L5 and L5-S1 laminectomy and microdiskectomy was performed. The patient had no improvement in his symptoms and underwent a second attempt at 2-level microdiskectomy.
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Figure 1: Axial (A) and sagittal (B) MRIs before initial surgery showing disk herniations at the L4-L5 and L5-S1 levels with impingement of the L5 and S1 roots.
Postoperatively, the patient had persistent symptoms that were only minimally relieved by the 2 previous attempts at microdiskectomy. The patient presented to the senior author (A.C.H.) 2 months postoperatively with worsening symptoms, including severe right-sided leg pain and sensory loss over lateral aspects of the right foot in the L5 dermatome. Magnetic resonance imaging revealed recurrent right-sided L4-L5 and L5-S1 posterolateral disk herniations (Figure 2). In addition to the MRI, radiographs revealed posterior calcification of the annulus into the intervertebral foramen as well as posterior to the vertebral body (Figure 3). Computed tomography scan revealed extensive calcification of the annulus at both L4-L5 and L5-S1 levels centrally and to the right (Figure 4).
Figure 3: Plain radiograph demonstrating posterior calcification of the annulus into the intervertebral foramen as well as posterior to the vertebral body.
The patient underwent an additional procedure consisting of an L4-L5 and L5-S1 revision and microdiskectomy. During the procedure, the right S1 nerve root could be observed tented over the large, calcified annular disk fragment. The calcified annulus was carefully dissected away from the root and pushed back into the disk space where it was then safely removed. Although some calcified annulus was left centrally and to the left side, the nerve root was seen to be free of compression, and further removal was not deemed necessary. The rim of annular calcification effectively obscured the location of the disk from the surrounding vertebral body.
The same procedure was performed at the L4-L5 level. The L5 nerve root was freed from the L4-L5 disk, and with the root protected, the calcified annulus was pushed back into the disk space and then removed. With the calcified disk material removed, the root was free of compression and took on a more normal anatomic configuration in the lateral recess, both at L5 and S1. No complications were observed during the procedure.
One year postoperatively, the patient reported no lower extremity discomfort. He ambulated on a regular basis. Physical examination demonstrated his strength, reflexes, and sensations returned to his preinjury baseline. Postoperatively, the patient was started on a regiment of physical therapy to work on progressive functional activity training with emphasis on a home exercise program.
Currently, MRI is the imaging modality of choice for the evaluation of suspected lumbar disk herniation. Magnetic resonance imaging provides the clinician with excellent anatomic detail, yet the relationship between the anatomy and clinical symptoms is sometimes controversial. Several studies have illustrated that MRIs in asymptomatic patients have high prevalence of incidental anatomic findings: disk herniations are seen in approximately one-third, disk bulges in half to two-thirds, and disk degeneration in up to 90%.10-13 Thus, it can be difficult to know which anatomic findings are of clinical importance; morphology does not always reflect function. Yet this is a relatively minor shortcoming and interpreter-specific. Therefore, MRI continues to be a widely used imaging modality and has become the primary modality in many circumstances.
Although plain radiographs have been accepted as the initial diagnostic imaging in patients with low back pain, many view them as a poor method for evaluation.7,14 Reflecting this, many clinicians have begun to use MRI as the first-line diagnostic modality for low back pain. McNally et al8 substituted a limited MRI scan for radiographs for 1042 patients with at least 6 weeks of low back pain. They concluded that an MRI scan detects a greater number of abnormalities. They have incorporated limited use of MRI into their routine practice, using it instead of radiographs for patients without radiculopathy and >6 weeks of low back pain.8
Additionally, Jarvik et al9 conducted a randomized controlled trial replacing lumbar spine radiographs with MRI in primary care patients and found there was no difference in disability, pain, or general health status. Those receiving MRI instead of plain radiographs were twice as likely to undergo surgery in the following year as opposed to physical therapy or chiropractor visits, resulting in an average increase in treatment cost of $470 with no measurable benefit in pain reduction. Yet, there was a preference among both patients and physicians for MRI. They suggested that substituting MRI for radiographs is likely safe and concluded that the policy advocated by McNally et al8 is likely not harmful to patients.9
In a study of 126 patients, Haig et al15 noted that MRI was unable to differentiate asymptomatic individuals from those with clinically relevant stenosis. The group with clinical stenosis differed greatly from the asymptomatic group in terms of lumbar tenderness, strength deficits, nerve-root tension signs, pain severity, pain below the knee, and walking deficits. Ilker et al16 had similar findings, where radiologists using just MRI incorrectly labeled asymptomatic patients as having clinical stenosis. Cost-effectiveness aside, our case demonstrates a pitfall to relying on MRI alone.
While we do not dispute the diagnostic imaging power of MRI, plain radiographs can often provide important additional information after failed surgery. Standing and dynamic radiographs can reveal alignment, instability (iatrogenic and degenerative), pseudarthrosis, end plate erosions (infection), or additional calcific densities. The calcifications in our patient were likely formed as a result of degenerative changes. Other recognized causes of calcifications in adults include hyperparathyroidism, hypervitaminosis D, chondrocalcinosis, hemochromatosis, ochronosis, pseudogout, gout, and hemolytic anemia. These diseases can result in the deposition of calcium in the annulus fibrosus.17-19 These bony changes can be difficult to observe on MRI because of their size, density, and relation to other dense structures such as normal bone and intervertebral disk. Calcification is usually invisible or hypointense on T1- and T2-weighted images on MRI.19 Diskal calcifications can, however, also appear hyperintense on T1-weighted images.20 Thus, reliable identification of annular calcifications can range from obvious to subtle or impossible via MRI alone.
In our case, radiographs altered the diagnosis and the operative plan, allowing the resolution of the patient’s symptoms. Although we cannot be entirely sure when the calcifications occurred, it is likely that the failure of the first 2 procedures was a result of the presence of the densities. We are unable to comment with certainty regarding the adequacy of the first 2 procedures; however, the operative notes report that the surgeons obtained a widened laminotomy during the second surgery and that decompression of the nerve roots from the surrounding bony elements and ligamentum flavum was performed both at L4-L5 and L5-S1. We believe the nerve roots were not decompressed, and while the surgeons reported no findings of abnormal calcifications, it is likely that the disk spaces were never fully opened because they were unknowingly covered by the calcified pathology.
In support of our theory, the patient did not benefit from either of the first 2 procedures; rather, he reported continuing radiculopathy of L5 and S1, indicating a persisting pathology rather than repeated herniation of the disks. Radiographs may have revealed the extensive annular calcification and alerted the surgeon of the disk space being hidden or obscured by this additional pathology. This may have facilitated a successful revision microdiskectomy after the first attempt.
It is not our recommendation that patients undergoing routine microdiskectomy obtain plain radiographs preoperatively. We understand that this would subject patients to unnecessary radiation and costs. However, routine radiographs are an essential tool in the workup of failed lumbar microdiskectomy. The workup for persistent radiculopathy after failed lumbar diskectomy should include the routine use of plain radiographs in addition to MRI or myelography to identify other pathology.
- Luo X, Pietrobon R, Sun SX, Liu GG, Hey L. Estimates and patterns of direct health care expenditures among individuals with back pain in the United States. Spine (Phila Pa 1976). 2004; 29(1):79-86.
- Carey TS, Garret J. Patterns of ordering diagnostic tests for patients with acute low back pain. The North Carolina Back Pain Project. Ann Intern Med. 1996; 125(10):807-814.
- Cherkin DC, Deyo RA, Wheeler K, Ciol MA. Phyisican variation in diagnostic testing for low back pain. Who you see is what you get. Arthritis Rheum. 1994; 37(1):15-22.
- Di Iorio D, Henley E, Doughty A. A survey of primary care physician practice patterns and adherence to acute low back problem guidelines. Arch Fam Med. 2000; 9(10):1015-1021.
- Bigos S, Bowyer O, Braen G, et al. Acute low back problems in adults: clinical practice guidelines number 14. AHCPR publication 95-0642. Agency for Health Care Policy and Research. Rockville, MD: US Department of Health and Human Services, Public Health Service; 1994.
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- Selim AJ, Fincke G, Ren XS, et al. Patient characteristics and patterns of use for lumbar spine radiographs: results from the Veterans Health Study. Spine (Phila Pa 1976). 2000; 25(19):2440-2444.
- McNally EG, Wilson DJ, Ostlere SJ. Limited magnetic resonance imaging in low back pain instead of plain radiographs: experience with first 1000 cases. Clin Radiol. 2001; 56(11):922-925.
- Jarvik JG, Hollingworth W, Martin B, et al. Rapid magnetic resonance imaging vs radiographs for patients with low back pain: a randomized controlled trial. JAMA. 2003; 289(21):2810-2818.
- Boden SD, Davis DO, Dina TS, Patronas NJ, Wiesel SW. Abnormal magnetic-resonance scans of the lumbar spine in asymptomatic subjects. A prospective investigation. J Bone Joint Surg Am. 1990; 72(3):403-408.
- Jensen MC, Brant-Zawadzki MN, Obuchowski N, Modic MT, Malkasian D, Ross JS. Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med. 1994; 331(2):69-73.
- Jarvik JJ, Hollingworth W, Heagerty P, Haynor DR, Deyo RA. The Longitudinal Assessment of Imaging and Disability of the Back (LAIDBack) study: baseline data. Spine (Phila Pa 1976). 2001; 26(10):1158-1166.
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- Haig AJ, Geisser ME, Tong HC, et al. Electromyographic and magnetic resonance imaging to predict lumbar stenosis, low-back pain, and no back symptoms. J Bone Joint Surg Am. 2007; 89(2):358-366.
- Ilker Y, Gunduz OH, Gazenfer E, Demirhan D, Onder U, Akyuz G. The utility of lumbar paraspinal mapping in the diagnosis of lumbar spinal stenosis. Am J Phys Med Rehabil. 2009; (88):843-851.
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- Major NM, Helms CA, Genant HK. Calcification demonstrated as high signal intensity on T1-weighted MR images of the disks of the lumbar spine. Radiology. 1993; 189(2):494-496.
Messrs Bronson and Koehler and Drs Qureshi and Hecht are from the Department of Orthopedic Surgery, Mount Sinai Medical Center, New York, New York.
Messrs Bronson and Koehler and Drs Qureshi and Hecht have no relevant financial relationships to disclose.
Correspondence should be addressed to: Andrew C. Hecht, MD, Leni and Peter W. May Department of Orthopedic Surgery, Mount Sinai Medical Center, 5 E 98 St, 9th Floor, New York, NY 10029 (firstname.lastname@example.org).