PRIMARY RESEARCH
Routine Upright Imaging for Evaluating Degenerative Lumbar Stenosis Incidence of Degenerative Spondylolisthesis Missed on Supine MRI Brad Segebarth, MD,* Mark F. Kurd, MD,* Priscilla H. Haug, BA,w and Rick Davis, MDz
Study Design: A retrospective cohort. Background: Degenerative spondylolisthesis (DS) with lumbar stenosis is a well-studied pathology and diagnosis is most commonly determined by a combination of magnetic resonance imaging (MRI) and standing radiographs. However, routine upright imaging is not universally accepted as standard in all practices. To the best of our knowledge, there has been no study investigating the incidence of missed diagnosis of DS evident only on standing lateral or dynamic radiographs when compared with sagittal alignment on MRI. Objective: The authors hypothesize that supine MRI evaluation alone in lumbar degenerative disease will significantly underestimate the incidence of DS. Secondary hypothesis is that there will be no significant difference in detecting spondylolisthesis when comparing dynamic flexion-extension radiographs to standing lateral radiographs. Methods: We retrospectively evaluated all patients presenting to spine clinic for degenerative lumbar conditions from July 2004 to July 2006 who had an MRI, upright lateral, and flexionextension radiographs at our institution. The incidence of DS found on dynamic flexion-extension radiographs but not on MRI was determined. We then reviewed each and compared flexion-extension versus standing lateral views to determine whether there was any significant difference in detecting anterolisthesis. Results: Of 416 patients with eligible studies, 109 were found to have DS at levels L4–L5, L5–S1, or L3–L4 based on flexionextension radiographs. Of these, only 78 were found to have a corresponding spondylolisthesis on MRI, leaving 31/109 (28%) of DS levels undiagnosed on MRI. No additional anterolisthesis cases were detected on standing flexion-extension verses standing lateral radiographs. Received for publication April 15, 2014; accepted October 14, 2014. From the *OrthoCarolina Spine Center; wOrthoCarolina Research Institute, Charlotte, NC; and zHealth Partners, St Paul MN. M.F.K. was a past consultant for Gersen Lehman Group and a past consultant for Pacira. R.D. was previously paid a consulting fee, is a consultant for Zimmer, is an expert testimony for SPS, and has royalties from Stryker. The remaining authors declare no conflict of interest. Reprints: Brad Segebarth, MD, OrthoCarolina Spine Center, 2001 Randolph Road, Charlotte, NC 28207 (e-mail: [email protected]). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
394 | www.jspinaldisorders.com
Conclusions: Routine standing lateral radiographs should be standard practice to identify DS, as nearly 1/3 of cases will be missed on supine MRI. This may have implications on whether or not an arthrodesis is performed on those patients requiring lumbar decompression. Flexion-extension radiographs demonstrated no added value compared with standing lateral x-rays for the purposes of diagnosing DS. Key Words: degenerative spondylolisthesis, lumbar stenosis, upright x-ray (J Spinal Disord Tech 2015;28:394–397)
D
egenerative lumbar spinal stenosis is a narrowing of the spinal canal or intervertebral foramina caused by disk protrusions, facet overgrowth, or ligament hypertrophy. This can lead to varying degrees of compression of spinal nerves and roots. Spondylolisthesis describes a pathologic state of 1 vertebra translating in the sagittal plane relative to an adjacent vertebra. Degenerative spondylolisthesis (DS), classified by Wiltse and colleagues1,2 as type III, is due to long-standing instability, arthritic changes, and degeneration of the intervertebral disk and facet joints. DS occurs most commonly at L4–L5, followed by L5–S1.3,4 The presentation of patients with DS often mimics those with lumbar spinal stenosis. Patients note low-back pain, neurogenic claudication, and lower extremity radiculopathy. Initial workup generally involves anterior/ posterior and lateral lumbar radiographs. Dynamic radiographs (flexion/extension) are also often used as an economical means to evaluate spondylolisthesis.5–7 Radiographs are important as it is imperative to detect DS in patients with stenosis as the treatment algorithms differ with regard to surgical management. Initially patients are managed with conservative measures including physical therapy and epidural steroid injections. A small percentage of patients fail conservative management and are considered for surgical intervention. The surgery for DS has been well studied.1,2,8–16 It is generally accepted that in addition to lumbar decompression, arthrodesis of the unstable region yields higher patient satisfaction. It is less clear whether instrumented fusion yields better clinical results, despite a lower pseudoarthrosis rate.9 Before surgical intervention, patients require advanced imaging: magnetic resonance imaging (MRI) or computed tomography myelogram. MRI is the most accurate method J Spinal Disord Tech
Volume 28, Number 10, December 2015
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 10, December 2015
Upright Imaging for Evaluating Lumbar Stenosis
for evaluating central canal and neuroforaminal stenosis and is most commonly used in the workup for persistent symptomatic lumbar degenerative disorders. However, the supine positioning in the MRI machine may be enough to spontaneously reduce low-grade spondylolisthesis.17 In 1 study, standing and recumbent radiographs in spondylolisthesis were compared, showing partial reduction when axial load was eliminated in recumbency.18 Several studies have also looked into the utility of lateral flexion-extension radiographs in patients with DS. Results of these studies are varied leading to a lack of consensus in the spine community.19–23 The purpose of this study is to compare the incidence of DS between lateral radiographs, dynamic radiographs, and supine MRI scans.
MATERIALS AND METHODS After approval from the Institutional Review Board, we performed a retrospective chart review of all patients seen in spine clinic at our institution between July 2004 and July 2006. The diagnostic codes included were acquired spondylolisthesis, lumbosacral disk disease, lumbar spinal stenosis, and lumbago. Patients were included if they had an MRI, standing lateral, and upright flexion-extension radiographs on our PACs system before surgical intervention. This yielded 416 subjects. Of those, 109 were determined to have DS based on an attending musculoskeletal radiologist’s read of the upright lateral and flexion-extension radiograph series. Of that 109, the incidence of corresponding spondylolisthesis detected on MRI, again based on attending radiologist read, was determined. Each case of undetectable spondylolisthesis on MRI was then further evaluated to determine the degree of slip based on the Meyerding classification. The investigators then compared standard lateral upright radiographs to the lateral flexion-extension views to determine whether any anterolisthesis levels were missed on the static standing x-ray compared with the dynamic standing views.
FIGURE 1. An upright lateral radiograph of a patient displaying spondylolisthesis.
DISCUSSION Despite controversy regarding the reliability of dynamic radiographs in determining lumbar segmental instability, flexion and extension views of the lumbar spine are the most widely used technique and a valid method to estimate sagittal segmental lumbar motion.19–25 Although
RESULTS Of the 109 DS levels detected on flexion-extension radiographs, all anterolisthesis levels were detected on standing lateral radiographs alone. Only 78 (72%) corresponding levels were found on MRI. The sensitivity of MRI for detecting DS is 71.6% (95%CI, 62%–79%) and the specificity is 99%. The positive predictive value is 96.3% and negative predictive value is 90.7%. Of those slips that went undetected, all were grade 1 according to Meyerding classification. Of the 416 eligible patients reviewed, 3/416 (< 1%) were found to have DS detected only on MRI and not on flexion-extension films, representing false positives. Figure 1 displays an upright lateral radiograph of a patient showing anterior spondylolisthesis. Figure 2 displays a sagittal MRI view of the same patient supine where spondylolisthesis is not evident. Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 2. A sagittal MRI view of the same patient supine where spondylolisthesis is not evident. www.jspinaldisorders.com |
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
395
J Spinal Disord Tech
Segebarth et al
more recent modalities may include dynamic MRI and traction-compression techniques, the dynamic flexionextension radiographs remain the most reliable and economical means of detecting sagittal translation.21,24–27 Although no study has evaluated the accuracy of MRI in demonstrating anterior translation in patient with DS, studies have analyzed the association between other MRI findings and DS. Bram and colleagues studied the correlation between annular tears, traction osteophytes, bone marrow abnormalities, and DS in 60 patients. They found no correlation with bone marrow abnormalities and an 18.8% and 12.5% sensitivity for annular tears and traction osteophytes, respectively.28 In 2007, Rihn et al29 reported a positive predictive value of 82% when evaluating the correlation between facet fluid and DS in 51 patients. Other authors have reported similar findings with regard to facet fluid or effusion.30,31 Our study analyzed the effectiveness of MRI and standing lateral radiographs in detecting confirmed DS on upright flexion-extension radiographs. The results of this study demonstrate a significant number (31/109) of DS levels with confirmed DS on upright flexion-extension radiographs not detected on supine MRI. This finding emphasizes the importance of upright imaging when evaluating lumbar degenerative diseases. In cases requiring surgery, failing to detect the segmental instability could result in decompression alone when decompression and fusion has been shown to yield better results.9,11,12,32 The similar results found when comparing standing lateral to flexion-extension radiographs suggests that a single standing lateral radiograph is adequate to detect instability. One recent study challenges the dynamic flexionextension radiographs as the best modality for detecting segmental instability, and proposes a new dynamic x-ray method involving supine-prone positioning.33 Although this proposed method appears to pick up more levels of sagittal translation than the standard flexion-extension radiographs, it remains to be determined whether this method is reproducible at different centers and whether the additional levels of sagittal translation are clinically relevant. The current study did not make direct comparison of flexion verses extension views or compare either individual view to standing lateral or supine MRI. Therefore, the true value of flexion-extension radiographs could not be qualified. However, it was our observation that there was not a complete reduction of DS on upright extension radiographs even if there were movement at that level. This would imply that an extension radiograph would be similar to standing lateral radiograph for the purposes of detecting a DS. Although the flexion-extension views may provide some idea of spinal mobility, one questions the utility in detecting true segmental instability. For this reason, the authors no longer obtain routine flexion-extension radiographs for the purposes of detecting DS, as it appears that a standing lateral x-ray alone is appropriate. To best evaluate the dynamic nature of a DS, we now obtain a supine bolster lateral x-ray compared with standing lateral radiograph. This best demonstrates the relationship between the differences in
396 | www.jspinaldisorders.com
Volume 28, Number 10, December 2015
supine MRI and upright imaging found in our study. Our theory is that it is not the force vector placed on pathologic lumbar facets, but the axial loading of the degenerative facets that results in DS. Further studies are needed to support these hypotheses. Like all epidemiological studies, there are important weaknesses to consider. First, there is a lack of consensus regarding the definition of segmental instability and determining what constitutes an abnormal motion segment. Both the MRI and dynamic x-ray studies were read by attending radiologists at our institution and the term anterolisthesis or anterior spondylolisthesis with regard to sagittal alignment was included in their interpretation. Second, our study was retrospective and therefore may be subject to both selection and misclassification bias. In addition, when comparing anterolisthesis found on lateral radiographs to flexion-extension radiographs, the investigators only looked at those with known spondylolisthesis based on series radiology report, leading to systematic bias. In conclusion, our study supports the use of routine standing radiographs as standard workup for degenerative lumbar disease. MRI alone will significantly underdiagnose cases of DS based on sagittal alignment. This missed diagnosis could result in lower patient satisfaction or repeat operation in cases where decompression alone rather than decompression and fusion was performed. For the purposes of detecting DS, the benefit of flexionextension x-rays is called into question. Further investigation is needed to better compare this modality to other images such as supine-prone positioning or bolster radiographs. REFERENCES 1. Wiltse LL, Winter RB. Terminology and measurement of spondylolisthesis. J Bone Joint Surg Am. 1983;6:768–772. 2. Wiltse LL, Hutchinson RH. Surgical treatment of spondylolisthesis. Clin Orthop. 1964;35:116–135. 3. Newman PH. The etiology of spondylolisthesis. J Bone Joint Surg Br. 1963;45B:39–59. 4. Posner I, White AA, Edwards WT, et al. A biomechanical analysis of the clinical stability of the lumbar and lumbosacral spine. Spine. 1982;7:374–389. 5. Dvorak J, Panjabi MM, Novotny JE, et al. Clinical validation of functional flexion-extension roentgenograms of the lumbar spine. Spine. 1991;16:943–950. 6. Wiltse LL, Kirkaldy-Willis WH, McIvor GW. The treatment of spinal stenosis. Clin Orthop. 1976;115:83–91. 7. Wiltse LL, Newman PH, Macnab I. Classification of spondylolysis and spondylolisthesis. Clin Orthop. 1976;117:23–29. 8. Bridwell KH, Sedgewick TA, Obrien MF, et al. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord. 1993;6:461–472. 9. Fischgrund JS, Mackay M, Herkowitz HN, et al. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective, randomized study comparing decompressive laminectomy and arthrodesis with and without spinal instrumentation. Spine. 1997; 22:2807–2812. 10. Fox MW, Onofrio BM, Hanssen AD. Clinical outcomes and radiological instability following decompressive lumbar laminectomy for degenerative spinal stenosis: a comparison of patients undergoing concomitant arthrodesis versus decompression alone. J Neurosurg. 1996;85:793–802. 11. Herkowitz H. Spine update: degenerative lumbar spondylolisthesis. Spine. 1995;20:1084–1090.
Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 10, December 2015
12. Herkowitz HN, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis. J Bone Joint Surg Am. 1991;73:802–808. 13. Matsudaira K, Yamazaki T, Seichi A, et al. Spinal stenosis in grade I degenerative lumbar spondylolisthesis: a comparative study of outcomes following laminoplasty and laminectomy with instrumented spinal fusion. J Orthop Sci. 2005;10:270–276. 14. Resnick DK, Choudhri TF, Dailey AT, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. J Neurosurg Spine. 2005;2:679–685. 15. Weinstein JN, Luri JD, Tosteson TD, et al. Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis. N Engl J Med. 2007;356:2257–2270. 16. Weinstein JN, Luri JD, Tosteson TD, et al. Surgical compared with nonoperative treatment for lumbar degenerative spondylolisthesis. Four-year results in the spine patient outcomes research trial (SPORT) randomized and observational cohorts. J Bone Joint Surg Am. 2009;91:1295–1304. 17. Bendo JA, Ong B. Importance of correlating static and dynamic imaging studies in diagnosing degenerative lumbar spondylolisthesis. Am J Orthop. 2001;30:247–250. 18. Lowe RW, Hayes TD, Kaye J, et al. Standing roentgenograms in spondylolisthesis. Clin Orthop. 1976;117:80–84. 19. Hayes MA, Howeard TC, Gruel CR, et al. Roentgenographic evaluation of lumbar spine flexion-extension in asymptomatic individuals. Spine. 1989;43:327–331. 20. Jayakumar P, Nnadi C, Saifuddin A, et al. Dynamic degenerative lumbar spondylolisthesis: diagnosis with axial loaded magnetic resonance imaging. Spine. 2006;31:E298–E301. 21. Lee S, Wong KW, Chan M, et al. Development and validation of a new technique for assessing lumbar spine motion. Spine. 2002;17: E215–E220. 22. Putto E, Tallroth K. Extension-flexion radiographs for motion studies of the lumbar spine: a comparison of two methods. Spine. 1990;15:107–110.
Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
Upright Imaging for Evaluating Lumbar Stenosis
23. Shaffer WO, Spratt KF, Weinstein J, et al. Volvo award in clinical sciences. The consistency and accuracy of roentgenograms for measuring sagittal translation in the lumbar vertebral motion segment. An experimental model. Spine. 1990;15:741–750. 24. Dupuis PR, Yong-Hing K, Cassidy JD, et al. Radiologic diagnosis of degenerative lumbar spinal instability. Spine. 1985;10:262–276. 25. Danielson B, Frennered K, Irstam L. Roentgenologic assessment of spondylolisthesis. I. A study of measurement variations. Acta Radiol. 1988;29:345–351. 26. McGregor AH, Anderton L, Gedroyc WM, et al. The use of interventional open MRI to assess the kinematics of the lumbar spine in patients with spondylolisthesis. Spine. 2002;27:1582–1586. 27. Pitkanen M, Manninen H, Lindgrer K, et al. Limited usefulness of traction-compression films in the radiographic diagnosis of lumbar spinal instability: comparison with flexion-extension films. Spine. 1997;22:193–197. 28. Bram J, Zanetti M, Min K, et al. MR abnormalities of the intervertebral disks and adjacent bone marrow as predictors of segmental instability of the lumbar spine. Acta Radiol. 1998;39: 18–23. 29. Rihn JA, Lee JY, Khan M, et al. Does lumbar facet fluid detected on magnetic resonance imaging correlate with radiographic instability in patients with degenerative lumbar disease? Spine. 2007; 32:1555–1560. 30. Chaput C, Padon D, Rush J, et al. The significance of increased fluid signal on magnetic resonance imaging of lumbar facets in relationship to degenerative spondylolisthesis. Spine. 2007;32:1883–1887. 31. Schinnerer KA, Katz LD, Grauer JN. MR findings of exaggerated fluid in facet joints predicts instability. J Spinal Disord Tech. 2008; 21:468–472. 32. Johnsson K, Willner S, Johnsson K. Postoperative instability after decompression for lumbar spinal stenosis. Spine. 1986;11: 107–110. 33. D’Andrea G, Ferrante L, Dinia L, et al. “Supine-prone” dynamic x-ray examination: new method to evaluate low-grade lumbar spondylolisthesis. J Spinal Disord Tech. 2005;18:80–83.
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397
Routine Upright Imaging for Evaluating Degenerative Lumbar Stenosis Incidence of Degenerative Spondylolisthesis Missed on Supine MRI Brad Segebarth, MD,* Mark F. Kurd, MD,* Priscilla H. Haug, BA,w and Rick Davis, MDz
Study Design: A retrospective cohort. Background: Degenerative spondylolisthesis (DS) with lumbar stenosis is a well-studied pathology and diagnosis is most commonly determined by a combination of magnetic resonance imaging (MRI) and standing radiographs. However, routine upright imaging is not universally accepted as standard in all practices. To the best of our knowledge, there has been no study investigating the incidence of missed diagnosis of DS evident only on standing lateral or dynamic radiographs when compared with sagittal alignment on MRI. Objective: The authors hypothesize that supine MRI evaluation alone in lumbar degenerative disease will significantly underestimate the incidence of DS. Secondary hypothesis is that there will be no significant difference in detecting spondylolisthesis when comparing dynamic flexion-extension radiographs to standing lateral radiographs. Methods: We retrospectively evaluated all patients presenting to spine clinic for degenerative lumbar conditions from July 2004 to July 2006 who had an MRI, upright lateral, and flexionextension radiographs at our institution. The incidence of DS found on dynamic flexion-extension radiographs but not on MRI was determined. We then reviewed each and compared flexion-extension versus standing lateral views to determine whether there was any significant difference in detecting anterolisthesis. Results: Of 416 patients with eligible studies, 109 were found to have DS at levels L4–L5, L5–S1, or L3–L4 based on flexionextension radiographs. Of these, only 78 were found to have a corresponding spondylolisthesis on MRI, leaving 31/109 (28%) of DS levels undiagnosed on MRI. No additional anterolisthesis cases were detected on standing flexion-extension verses standing lateral radiographs. Received for publication April 15, 2014; accepted October 14, 2014. From the *OrthoCarolina Spine Center; wOrthoCarolina Research Institute, Charlotte, NC; and zHealth Partners, St Paul MN. M.F.K. was a past consultant for Gersen Lehman Group and a past consultant for Pacira. R.D. was previously paid a consulting fee, is a consultant for Zimmer, is an expert testimony for SPS, and has royalties from Stryker. The remaining authors declare no conflict of interest. Reprints: Brad Segebarth, MD, OrthoCarolina Spine Center, 2001 Randolph Road, Charlotte, NC 28207 (e-mail: [email protected]). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
394 | www.jspinaldisorders.com
Conclusions: Routine standing lateral radiographs should be standard practice to identify DS, as nearly 1/3 of cases will be missed on supine MRI. This may have implications on whether or not an arthrodesis is performed on those patients requiring lumbar decompression. Flexion-extension radiographs demonstrated no added value compared with standing lateral x-rays for the purposes of diagnosing DS. Key Words: degenerative spondylolisthesis, lumbar stenosis, upright x-ray (J Spinal Disord Tech 2015;28:394–397)
D
egenerative lumbar spinal stenosis is a narrowing of the spinal canal or intervertebral foramina caused by disk protrusions, facet overgrowth, or ligament hypertrophy. This can lead to varying degrees of compression of spinal nerves and roots. Spondylolisthesis describes a pathologic state of 1 vertebra translating in the sagittal plane relative to an adjacent vertebra. Degenerative spondylolisthesis (DS), classified by Wiltse and colleagues1,2 as type III, is due to long-standing instability, arthritic changes, and degeneration of the intervertebral disk and facet joints. DS occurs most commonly at L4–L5, followed by L5–S1.3,4 The presentation of patients with DS often mimics those with lumbar spinal stenosis. Patients note low-back pain, neurogenic claudication, and lower extremity radiculopathy. Initial workup generally involves anterior/ posterior and lateral lumbar radiographs. Dynamic radiographs (flexion/extension) are also often used as an economical means to evaluate spondylolisthesis.5–7 Radiographs are important as it is imperative to detect DS in patients with stenosis as the treatment algorithms differ with regard to surgical management. Initially patients are managed with conservative measures including physical therapy and epidural steroid injections. A small percentage of patients fail conservative management and are considered for surgical intervention. The surgery for DS has been well studied.1,2,8–16 It is generally accepted that in addition to lumbar decompression, arthrodesis of the unstable region yields higher patient satisfaction. It is less clear whether instrumented fusion yields better clinical results, despite a lower pseudoarthrosis rate.9 Before surgical intervention, patients require advanced imaging: magnetic resonance imaging (MRI) or computed tomography myelogram. MRI is the most accurate method J Spinal Disord Tech
Volume 28, Number 10, December 2015
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 10, December 2015
Upright Imaging for Evaluating Lumbar Stenosis
for evaluating central canal and neuroforaminal stenosis and is most commonly used in the workup for persistent symptomatic lumbar degenerative disorders. However, the supine positioning in the MRI machine may be enough to spontaneously reduce low-grade spondylolisthesis.17 In 1 study, standing and recumbent radiographs in spondylolisthesis were compared, showing partial reduction when axial load was eliminated in recumbency.18 Several studies have also looked into the utility of lateral flexion-extension radiographs in patients with DS. Results of these studies are varied leading to a lack of consensus in the spine community.19–23 The purpose of this study is to compare the incidence of DS between lateral radiographs, dynamic radiographs, and supine MRI scans.
MATERIALS AND METHODS After approval from the Institutional Review Board, we performed a retrospective chart review of all patients seen in spine clinic at our institution between July 2004 and July 2006. The diagnostic codes included were acquired spondylolisthesis, lumbosacral disk disease, lumbar spinal stenosis, and lumbago. Patients were included if they had an MRI, standing lateral, and upright flexion-extension radiographs on our PACs system before surgical intervention. This yielded 416 subjects. Of those, 109 were determined to have DS based on an attending musculoskeletal radiologist’s read of the upright lateral and flexion-extension radiograph series. Of that 109, the incidence of corresponding spondylolisthesis detected on MRI, again based on attending radiologist read, was determined. Each case of undetectable spondylolisthesis on MRI was then further evaluated to determine the degree of slip based on the Meyerding classification. The investigators then compared standard lateral upright radiographs to the lateral flexion-extension views to determine whether any anterolisthesis levels were missed on the static standing x-ray compared with the dynamic standing views.
FIGURE 1. An upright lateral radiograph of a patient displaying spondylolisthesis.
DISCUSSION Despite controversy regarding the reliability of dynamic radiographs in determining lumbar segmental instability, flexion and extension views of the lumbar spine are the most widely used technique and a valid method to estimate sagittal segmental lumbar motion.19–25 Although
RESULTS Of the 109 DS levels detected on flexion-extension radiographs, all anterolisthesis levels were detected on standing lateral radiographs alone. Only 78 (72%) corresponding levels were found on MRI. The sensitivity of MRI for detecting DS is 71.6% (95%CI, 62%–79%) and the specificity is 99%. The positive predictive value is 96.3% and negative predictive value is 90.7%. Of those slips that went undetected, all were grade 1 according to Meyerding classification. Of the 416 eligible patients reviewed, 3/416 (< 1%) were found to have DS detected only on MRI and not on flexion-extension films, representing false positives. Figure 1 displays an upright lateral radiograph of a patient showing anterior spondylolisthesis. Figure 2 displays a sagittal MRI view of the same patient supine where spondylolisthesis is not evident. Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
FIGURE 2. A sagittal MRI view of the same patient supine where spondylolisthesis is not evident. www.jspinaldisorders.com |
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
395
J Spinal Disord Tech
Segebarth et al
more recent modalities may include dynamic MRI and traction-compression techniques, the dynamic flexionextension radiographs remain the most reliable and economical means of detecting sagittal translation.21,24–27 Although no study has evaluated the accuracy of MRI in demonstrating anterior translation in patient with DS, studies have analyzed the association between other MRI findings and DS. Bram and colleagues studied the correlation between annular tears, traction osteophytes, bone marrow abnormalities, and DS in 60 patients. They found no correlation with bone marrow abnormalities and an 18.8% and 12.5% sensitivity for annular tears and traction osteophytes, respectively.28 In 2007, Rihn et al29 reported a positive predictive value of 82% when evaluating the correlation between facet fluid and DS in 51 patients. Other authors have reported similar findings with regard to facet fluid or effusion.30,31 Our study analyzed the effectiveness of MRI and standing lateral radiographs in detecting confirmed DS on upright flexion-extension radiographs. The results of this study demonstrate a significant number (31/109) of DS levels with confirmed DS on upright flexion-extension radiographs not detected on supine MRI. This finding emphasizes the importance of upright imaging when evaluating lumbar degenerative diseases. In cases requiring surgery, failing to detect the segmental instability could result in decompression alone when decompression and fusion has been shown to yield better results.9,11,12,32 The similar results found when comparing standing lateral to flexion-extension radiographs suggests that a single standing lateral radiograph is adequate to detect instability. One recent study challenges the dynamic flexionextension radiographs as the best modality for detecting segmental instability, and proposes a new dynamic x-ray method involving supine-prone positioning.33 Although this proposed method appears to pick up more levels of sagittal translation than the standard flexion-extension radiographs, it remains to be determined whether this method is reproducible at different centers and whether the additional levels of sagittal translation are clinically relevant. The current study did not make direct comparison of flexion verses extension views or compare either individual view to standing lateral or supine MRI. Therefore, the true value of flexion-extension radiographs could not be qualified. However, it was our observation that there was not a complete reduction of DS on upright extension radiographs even if there were movement at that level. This would imply that an extension radiograph would be similar to standing lateral radiograph for the purposes of detecting a DS. Although the flexion-extension views may provide some idea of spinal mobility, one questions the utility in detecting true segmental instability. For this reason, the authors no longer obtain routine flexion-extension radiographs for the purposes of detecting DS, as it appears that a standing lateral x-ray alone is appropriate. To best evaluate the dynamic nature of a DS, we now obtain a supine bolster lateral x-ray compared with standing lateral radiograph. This best demonstrates the relationship between the differences in
396 | www.jspinaldisorders.com
Volume 28, Number 10, December 2015
supine MRI and upright imaging found in our study. Our theory is that it is not the force vector placed on pathologic lumbar facets, but the axial loading of the degenerative facets that results in DS. Further studies are needed to support these hypotheses. Like all epidemiological studies, there are important weaknesses to consider. First, there is a lack of consensus regarding the definition of segmental instability and determining what constitutes an abnormal motion segment. Both the MRI and dynamic x-ray studies were read by attending radiologists at our institution and the term anterolisthesis or anterior spondylolisthesis with regard to sagittal alignment was included in their interpretation. Second, our study was retrospective and therefore may be subject to both selection and misclassification bias. In addition, when comparing anterolisthesis found on lateral radiographs to flexion-extension radiographs, the investigators only looked at those with known spondylolisthesis based on series radiology report, leading to systematic bias. In conclusion, our study supports the use of routine standing radiographs as standard workup for degenerative lumbar disease. MRI alone will significantly underdiagnose cases of DS based on sagittal alignment. This missed diagnosis could result in lower patient satisfaction or repeat operation in cases where decompression alone rather than decompression and fusion was performed. For the purposes of detecting DS, the benefit of flexionextension x-rays is called into question. Further investigation is needed to better compare this modality to other images such as supine-prone positioning or bolster radiographs. REFERENCES 1. Wiltse LL, Winter RB. Terminology and measurement of spondylolisthesis. J Bone Joint Surg Am. 1983;6:768–772. 2. Wiltse LL, Hutchinson RH. Surgical treatment of spondylolisthesis. Clin Orthop. 1964;35:116–135. 3. Newman PH. The etiology of spondylolisthesis. J Bone Joint Surg Br. 1963;45B:39–59. 4. Posner I, White AA, Edwards WT, et al. A biomechanical analysis of the clinical stability of the lumbar and lumbosacral spine. Spine. 1982;7:374–389. 5. Dvorak J, Panjabi MM, Novotny JE, et al. Clinical validation of functional flexion-extension roentgenograms of the lumbar spine. Spine. 1991;16:943–950. 6. Wiltse LL, Kirkaldy-Willis WH, McIvor GW. The treatment of spinal stenosis. Clin Orthop. 1976;115:83–91. 7. Wiltse LL, Newman PH, Macnab I. Classification of spondylolysis and spondylolisthesis. Clin Orthop. 1976;117:23–29. 8. Bridwell KH, Sedgewick TA, Obrien MF, et al. The role of fusion and instrumentation in the treatment of degenerative spondylolisthesis with spinal stenosis. J Spinal Disord. 1993;6:461–472. 9. Fischgrund JS, Mackay M, Herkowitz HN, et al. Degenerative lumbar spondylolisthesis with spinal stenosis: a prospective, randomized study comparing decompressive laminectomy and arthrodesis with and without spinal instrumentation. Spine. 1997; 22:2807–2812. 10. Fox MW, Onofrio BM, Hanssen AD. Clinical outcomes and radiological instability following decompressive lumbar laminectomy for degenerative spinal stenosis: a comparison of patients undergoing concomitant arthrodesis versus decompression alone. J Neurosurg. 1996;85:793–802. 11. Herkowitz H. Spine update: degenerative lumbar spondylolisthesis. Spine. 1995;20:1084–1090.
Copyright
r
2014 Wolters Kluwer Health, Inc. All rights reserved.
Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.
J Spinal Disord Tech
Volume 28, Number 10, December 2015
12. Herkowitz HN, Kurz LT. Degenerative lumbar spondylolisthesis with spinal stenosis. A prospective study comparing decompression with decompression and intertransverse process arthrodesis. J Bone Joint Surg Am. 1991;73:802–808. 13. Matsudaira K, Yamazaki T, Seichi A, et al. Spinal stenosis in grade I degenerative lumbar spondylolisthesis: a comparative study of outcomes following laminoplasty and laminectomy with instrumented spinal fusion. J Orthop Sci. 2005;10:270–276. 14. Resnick DK, Choudhri TF, Dailey AT, et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. J Neurosurg Spine. 2005;2:679–685. 15. Weinstein JN, Luri JD, Tosteson TD, et al. Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis. N Engl J Med. 2007;356:2257–2270. 16. Weinstein JN, Luri JD, Tosteson TD, et al. Surgical compared with nonoperative treatment for lumbar degenerative spondylolisthesis. Four-year results in the spine patient outcomes research trial (SPORT) randomized and observational cohorts. J Bone Joint Surg Am. 2009;91:1295–1304. 17. Bendo JA, Ong B. Importance of correlating static and dynamic imaging studies in diagnosing degenerative lumbar spondylolisthesis. Am J Orthop. 2001;30:247–250. 18. Lowe RW, Hayes TD, Kaye J, et al. Standing roentgenograms in spondylolisthesis. Clin Orthop. 1976;117:80–84. 19. Hayes MA, Howeard TC, Gruel CR, et al. Roentgenographic evaluation of lumbar spine flexion-extension in asymptomatic individuals. Spine. 1989;43:327–331. 20. Jayakumar P, Nnadi C, Saifuddin A, et al. Dynamic degenerative lumbar spondylolisthesis: diagnosis with axial loaded magnetic resonance imaging. Spine. 2006;31:E298–E301. 21. Lee S, Wong KW, Chan M, et al. Development and validation of a new technique for assessing lumbar spine motion. Spine. 2002;17: E215–E220. 22. Putto E, Tallroth K. Extension-flexion radiographs for motion studies of the lumbar spine: a comparison of two methods. Spine. 1990;15:107–110.
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Upright Imaging for Evaluating Lumbar Stenosis
23. Shaffer WO, Spratt KF, Weinstein J, et al. Volvo award in clinical sciences. The consistency and accuracy of roentgenograms for measuring sagittal translation in the lumbar vertebral motion segment. An experimental model. Spine. 1990;15:741–750. 24. Dupuis PR, Yong-Hing K, Cassidy JD, et al. Radiologic diagnosis of degenerative lumbar spinal instability. Spine. 1985;10:262–276. 25. Danielson B, Frennered K, Irstam L. Roentgenologic assessment of spondylolisthesis. I. A study of measurement variations. Acta Radiol. 1988;29:345–351. 26. McGregor AH, Anderton L, Gedroyc WM, et al. The use of interventional open MRI to assess the kinematics of the lumbar spine in patients with spondylolisthesis. Spine. 2002;27:1582–1586. 27. Pitkanen M, Manninen H, Lindgrer K, et al. Limited usefulness of traction-compression films in the radiographic diagnosis of lumbar spinal instability: comparison with flexion-extension films. Spine. 1997;22:193–197. 28. Bram J, Zanetti M, Min K, et al. MR abnormalities of the intervertebral disks and adjacent bone marrow as predictors of segmental instability of the lumbar spine. Acta Radiol. 1998;39: 18–23. 29. Rihn JA, Lee JY, Khan M, et al. Does lumbar facet fluid detected on magnetic resonance imaging correlate with radiographic instability in patients with degenerative lumbar disease? Spine. 2007; 32:1555–1560. 30. Chaput C, Padon D, Rush J, et al. The significance of increased fluid signal on magnetic resonance imaging of lumbar facets in relationship to degenerative spondylolisthesis. Spine. 2007;32:1883–1887. 31. Schinnerer KA, Katz LD, Grauer JN. MR findings of exaggerated fluid in facet joints predicts instability. J Spinal Disord Tech. 2008; 21:468–472. 32. Johnsson K, Willner S, Johnsson K. Postoperative instability after decompression for lumbar spinal stenosis. Spine. 1986;11: 107–110. 33. D’Andrea G, Ferrante L, Dinia L, et al. “Supine-prone” dynamic x-ray examination: new method to evaluate low-grade lumbar spondylolisthesis. J Spinal Disord Tech. 2005;18:80–83.
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