Commentary A Plea for Prospective Studies on Diskography Kim J. Burchiel, * E d m u n d H. Frank, * a n d Timothy L. Keenenl- All parts of the body which have a function, if used in moderation and exercised in labours in which each is accustomed, become thereby healthy, well-developed, and age more slowly, but if unused and left idle they become liable to disease, defective in growth, and age quickly. Hippocrates r. Bogduk has eloquently stated the case in favor of diskography as a diagnostic tool for identifying the isolated intervertebral lumbar disk that is painful in concordance with the patients low back symptoms. He likewise has separated out as nondiagnostic the patient with multiple level diskography pain and the patient with discordant diskography pain. His lucid separation of the elements in the controversy surrounding diskography and his review of the literature should be a reference for all students of degenerative spinal disorders. Back pain is virtually ubiquitous, 4 and it remains the most costly disorder in the U.S. 3 Most treatments for back pain, particularly surgery, are unproven and potentially harmful. 18 Back pain is also an exceedingly complex entity. This commentary draws attention to one, but not the sole, potential cause of back pain, the degenerated disk. Many patients with back pain do not have positive diskography. Furthermore, the correlation between positive diskography and the disk histology, computed tomography, or magnetic resonance imaging is not completely reliable. 9 Like- D From the Divisions of *Neurosurgery and tOrthopedics, Department of Surgery, School of Medicine, Oregon Health Sciences University, Portland, OR. Reprint requests: Kim J. Burchiel, MD, Division of Neurosurgery, L472/Oregon Health Sciences University. 3181 Southwest Sam Jackson Park Road, Portland, OR 97201. 161) wise, the degree of internal disk disruption does not necessarily parallel the pain provoked by diskography, 11 but is directly related to the patient's age. TM It is not absolutely certain which portion of the disk or endplate may convey nociceptive information during provocative diskography. 1° Other structures have also been implicated in the pathophysiology of back pain, including portions of the nerve root such as the sinovertebral nerve, the posterior support structures such as the facets, ligamentous structures, and muscle. 5,~s,~6 It is likely that in most back pain cases several elements of the spinal motion segment contribute to the overall problem. 22 This multifactorial nature of back pain has previously been an impediment to prospective research on the subject. Dr. Bogduk has suggested a way for us to proceed, at least in the subset of patients with positive provocative diskography. His implicit thesis is that we should be able to predict the success of lumbar intervertebral arthrodesis in individual cases based on the results of diskography. The use of diskography as a predictor of surgical success would only be possible if the disk was the sole cause of pain, which is very hard to prove since arthrodesis would also immobilize painproducing facet joints. Nevertheless, the hypothesis is reasonable and testable. In a day of cost containment, the indications for lumbar arthrodesis for degenerative disk disease with nonradicular back pain remain an issue. The focus article cites several reports of surgical series based on the yet unsubstantiated conclusion that operations in patients with abnormal diskograms lead to improved surgical outcomes, and there are others. 6-s,~2,~3,21 In fact, the net effect of diskography has been to promote invasive procedures, many of which are not otherwise clinically indicated. This occurs because the practice of medicine is often not inherently and stringently scientific, physicians are frustrated with the treatment of back pain and are APS Journal 3(3): 160-162, 1994 COMMENTARY/Burchielet al. willing to apply results of a test that has not been validated, physicians will relentlessly pursue an indication in an attempt to assist a desperate patient, and reimbursement is available. One aspect of the focus article that bears attention is the discussion of cervical diskography. While there is substantial information on lumbar diskography, less is definitely known about the cervical procedure. Making the intellectual jump from the lumbar to cervical spine in the applicability of this test is not justified, and Dr. Bogduk does not make this error. Given the anatomic and presumed physiologic differences between these disks, the results of any proposed prospective study on lumbar disks should not be applied to their cervical counterparts. While there is an unquestionable need for more scientific data on the practice of diskography, we are still left not knowing what to do with our low back pain patients. The putative usefulness of naming the pain is perhaps the central unresolved issue of this article. Most practitioners who care for patients with back pain would prefer to make a specific diagnosis, and then proceed with treatment if appropriate. Cynicism and nihilism clearly do not have an appropriate role in the management of back pain, yet taking a conservative viewpoint, there is little apparent utility in a diagnostic test that neither improves prognostication nor influences therapy, and has risks. 19 Dr. Bogduk's call for "more stringently designed studies (are required) to vindicate these claims" should be heeded. Small area analysis and metaanalysis outcome studies have documented the discrepancies in our surgical decision making. 23 The treatment of low back pain in the U.S. exemplifies a disorder in need of prospective, randomized, and blinded outcome studies. Retrospective data analysis, or practice guidelines based on metaanalysis and expert opinion have not produced a definitive answer, and likely will not satisfactorily resolve this question. 1 The design of a prospective study to address this question would be a daunting, but not insurmountable task. Other recent reports on intradiskal chemotherapy have been successfully completed in a randomized, double-blinded, and prospective fashion. 17 Besides computed tomography and magnetic resonance imaging, other less expensive ancillary tests may help to screen patients for diskography. 2° Less invasive surgical modalities, such as percutaneous lumbar diskectomy also could be compared to conservative therapy or fusion, or both. 2 It is reasonable to call for careful clinical outcomes research on diskography. As Dr. Bogduk points out, the development of diskography as a clinical tool has 161 been, to some extent, arrested by the uncritical adoption of the test, and reimbursement for a procedure of unknown value. Lacking supportive evidence, the provision of reimbursement for diskography, or surgical procedures based on the findings of diskography, should be reconsidered. Diskography should also be reserved for patients enrolled in an institutionally approved research protocol, much as is currently mandated for spinal segmental fixation hardware. Well-designed research should be undertaken to clarify the role of diskography, if any, in the management of back pain. Most importantly, pain management specialists should support the conclusion that prospective controlled studies are needed to evaluate the results of surgical treatment of the isolated painful lumbar disk. The uncritical continuance of this technique without scientifically valid evidence is no longer supportable. References 1. Anderson C: Measuring what works in health care. Science 263:1080-1082, 1994 2. Castro WH, Jerosch J, Hepp R, Schulitz KP: Restriction of indication for automated percutaneous lumbar discectomy based on computed tomographic discography. Spine 17:1239-1243, 1992 3. Cats-Baril WL, Frymoyer JW: The economics of spinal disorders, pp. 85-105. 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Heggeness MH, Doherty BJ: Discography causes end plate deflection. Spine 18:1050-1053, 1993 11. Maezawa S, Muro T: Pain provocation at lumbar discography as analyzed by computed tomography/discography. Spine 17:1309-1315, 1992 162 COMMENTARY/Burchielet al. 12. Murtagh FR, Arrington JA: Computer tomographically guided discography as a determinant of normal disc level before fusion. Spine 17:826-830, 1992 13. Newman MH, Grinstead GL: Anterior lumbar interbody fusion for internal disc disruption. Spine 17:831-833, 1992 14. Ninomiya M, Muro T: Pathoanatomy of lumbar disc herniation as demonstrated by computed tomography/ discography. Spine 17:1316-1322, 1992 15. Parke W, Burchiel K, Rydevik Bet al: Nerve: basic science perspectives, pp. 57-123. In: New perspectives on low back pain. American Academy of Orthopedic Surgeons, Park Ridge, IL, 1989 16. Schultz A, Carter D, Grood E, King A, Panjabi M: Posterior support structures: basic science perspectives. pp. 249-275. In: New perspectives on low back pain. American Academy of Orthopedic Surgeons, Park Ridge, IL, 1989 17. Simmons JW, McMillin JN, Emery SF, Kimmich SJ: Intradiscal steroids: a prospective double-blind clinical trial. Spine 17(suppl):S172-175, 1992 18. Spitzer WO, LeBlanc FE, Dupuis Met al: Scientific approach to the assessment and management of activity related spinal disorders: a monograph for clinicians. Report of the Quebec task force on spinal disorders. Spine 12(suppl):S1-59, 1987 19. Tallroth K, Soini J, Antti-Poika I et al: Premedication and short-term complications in iohexol discography. Ann Chir Gynaecol 80:49-53, 1991 20. Tervonen O, Lahde S, Vanharanta H: Ultrasound diagnosis of lumbar disc degeneration: comparison with computed tomography/discography. Spine 16: 951-954, 1991 21. Thalgott J, LaRocca H, Gardner Vet al: Reconstruction of failed lumbar surgery with narrow AO DCP plates for spinal arth rodesis. Spine 16(suppl):$170-175, 1991 22. Vanharanta H, Floyd T, Ohnmeiss DD, Hochschuler SH, Guyer RD: The relationship of facet tropism to degenerative disc disease. Spine 18:1000-1005, 1993 23. Volin E, Mayer J, Diehr P et al: Small area analysis of surgery for low-back pain. Spine 17:575-579, 1992