Dynamic Chiropractic Canada – July 1, 2014, Vol. 07, Issue 07

Minimally Invasive Spine Surgery: A Potentially Misleading Term

By Ronald Fudala, DC, DACAN

Applying the term minimal to lumbar spine surgery can be misleading, presenting the potential for obscured risks, overstated benefits and inappropriate utilization. This is especially true considering the mindset of the average health care consumer or well-intentioned clinician who may want to believe that minimal always equates to better, safer or more accurate. Let's examine minimally invasive spine surgery (MIS) for the lumbar spine. The goal is to lay the foundation to better understand if and when these procedures may be applicable for our patients, and to avoid being "clinically seduced" by the term minimal.


Minimally invasive spine surgery is designed to preserve spinal architecture, cause less tissue destruction, improve recovery times, and lower surgical risks.1 The use of such techniques has exploded over the past 20 years, involving smaller incisive corridors and instrumentation to accomplish a variety of operative procedures.2

However, as intuitively appealing as these approaches may seem, especially to conservative practitioners and patients, they are not without risk3-4 and the benefits may be more ostensible than real.5-6 It is concerning that as these procedures become more popularized and marketed to the public, there remains very little in the way of concrete research to clearly delineate indications for and the comparative effectiveness of these treatments.7-8

Historical Perspective

Notwithstanding the increasing awareness (possibly due to marketing efforts) of MIS procedures, they are not new. Depending on one's definition of "minimally invasive," the birth of these techniques dates back to Smith's use of chymopapain in 1963,9 the introduction of microdiscectomy in the 1970s10 or possibly the initial use of laser discectomy in the 1980s.11 Tubular retractor systems and automated percutaneous discectomy, designed to reduce trauma to the paraspinal compartment, were introduced in the 1990s.12

From then up until the present, most of the reported technical advances have occurred with variations in the use of endoscopy13 or novel approaches and devices for instrumented spinal fusion.14-15

Interventional Approaches

MIS procedures are diverse in their technical specifics and nomenclature, but share a common theme of having a small portal of entry and narrow surgical corridor.16-17 It is most logical to classify MIS interventions based upon three primary surgical end-points: ablation, decompression and fusion-stabilization.

Ablation techniques seek to denervate presumed painful structures (disc, facet) or lyse scar tissue. Common methods include radiofrequency, alcohol, laser or freezing.18-21 Organizations may promote these in a way to imply that inflammation or other pain generators can be diagnosed in "real time" and sequential treatment of multiple painful sites can be accomplished in one setting.19

MIS decompression strives to reduce nerve root contact and/or stimulation of peripheral annular nociceptive fibers. Procedures differ depending on the etiology of compression, extent of tissue extracted or "dissolved," and how this is accomplished.

Internal volume reduction techniques are often employed for contained disc lesions. These presuppose that a retraction of external disc material away from the affected nerve root or reduction in annular nociception occurs when intradiscal pressure is reduced through evaporation, coagulation, dissolution, or mechanical removal of internal nuclear tissue.22-24 Thermal approaches use laser or radiofrequency energy to either evaporate the nucleus pulposus or coagulate surrounding tissue.21-22

Chemonucleolysis, the dissolution of nuclear tissue, first used chymopapain9 and more recently ozone. Ozone reportedly accomplishes the same result as chymopapain, but with less potential for adverse events.25

Mechanical volume reduction is accomplished by extracting nuclear material using a cannula to introduce small cutting and sucking instruments through the annulus into the nucleus. Named procedures within this category include, among others, automated percutaneous discectomy, laser annuloplasty and nucleoplasty.26-28

MIS for non-contained discs or boney and ligamentous compressive lesions, in contrast to internal volume reduction, involves external surgical resection/removal of the offending anatomy. Tubular retractors, designed to spare paraspinal muscle tissue are increasingly being utilized to create the surgical portal, although the benefit to this over standard open procedures has yet to be convincingly proven.28-29

The primary difference between MIS fusion and "open" procedures basically amounts to a smaller portal of entry and shorter operative time. These procedures are being increasingly utilized, but there is a paucity of evidence to illustrate any improvement in outcomes or significant surgical morbidity as compared to open procedures.30

Most open fusion procedures performed in the past are now being done in a "minimally invasive" fashion with innovations in approach sites and angles enabled by the smaller portals of entry. Some of these approaches are TLIF (transverse lateral interbody fusion), XLIF (extreme lateral interbody fusion) and AXLIF (axial interbody fusion using a pre-sacral approach).31

Clinical Assessment and Decision-Making for MIS Intervention: 3 Questions

Determination of an appropriate candidate for MIS procedures involves taking into account three questions. In actuality, these questions apply to any form of care, but increase in importance when considering more aggressive measures.

Question #1: Is the "target" of an MIS procedure really the source of a patient's pain? In other words, the size of the "hole" is irrelevant if the target is wrong. To this end, MIS procedures are susceptible to the same primary challenge, especially in nonspecific back pain, as most any other procedure: the inability, in a large majority of cases, to reliably determine the anatomic structure responsible for a patient's pain.32-33

This is true regardless of what is seen on imaging,34-37 the bedside tests used during clinical examination,38-39 or any type of anesthetic or provocative injection procedure that may be used to ostensibly provide clear diagnostic confirmation.40-43

Understanding the imprecise nature of diagnosing spinal pain becomes even more important to those patients who may have encountered a website where it is implied that "[t]he doctor finds inflammation and actually diagnoses the source of pain."44 Such proclamations, possibly appearing in some form on other sites offering MIS procedures, are at best, unsubstantiated by the literature and misleading.

The diagnosis of radiculopathy, often felt to be more straightforward, is not without challenges. This is especially true when the imaging and neurologic exam are not unequivocally abnormal and highly congruent. In a systematic review, Al Nezari, et al., found that, in most cases, the tests we use for lumbar radiculopathy are inaccurate and not clinically useful.45 Another study, looking at cervical radiculopathy, found that tests vary considerably in their specificity and sensitivity and are more accurate when used in combination.46

Although combining such tests with imaging may improve diagnostic accuracy, we must also keep in mind the considerable number of disc protrusions, and even herniations, seen in asymptomatic individuals.35

Question #2: What are the indications for MIS intervention? At present, no formally adopted guidelines exist that are specific to MIS procedures or discuss clear indications for appropriate utilization. Thus, it must be assumed that MIS procedures would currently follow guidelines for "non-MIS" interventions directed at similar pathology.

However, even these guidelines can be extremely vague and lacking in scientific evidence. For example, guidelines pertaining to lumbar spinal fusion (various types) published on the American Association of Neurological Surgeons website state; "There is insufficient evidence available to support a treatment guideline."47

The inability to clearly define appropriate indications for any type of surgery, including MIS procedures, is better understood when one recognizes that most of the current surgical research focuses on developing and implementing new technology, not the determination of when and for whom these procedures are applicable.48

These authors pointed out that over the past 20 years, 33 technical (device) trials have been completed and only six indication trials. In summary, they stated, "We note that there have been 39 RCTs involving lumbar fusion; yet, the vast majority has avoided a fundamental, and still controversial, question: is surgery superior to non-operative management?"

Lacking an answer to this important question, the indications for MIS interventions are likely to remain as obscure and individualized to a particular procedural provider as are any other of the present "non-MIS" procedures. This is a great concern, especially when considering that the U.S. already has a 20-fold geographic variation in how spinal surgery is utilized, with little clinical evidence to support such variability.49 Even more alarming is that, despite this variability, the rate of spinal fusion has risen threefold since 1998 and national costs have increased by a factor of eight.50

Lacking a formal consensus for indications on most all MIS procedures, some guidance can currently be found in selected papers, professional society publications, insurance bulletins, and publications sponsored by device manufacturers.51-53 The article by Woeltjen and Jones53 provides a nice overview of the current status of various MIS procedures, including indications and contraindications for use. The interested reader will note the paucity of randomized controlled trials associated with most all of the procedures discussed and also readily recognize the potential conflict of interest in any publication produced by a company marketing their devices.

Question #3: Are the outcomes of an MIS procedure superior to alternative approaches or what is currently being done for the patient? Laser facet joint denervation is considered to be "investigational" by some, if not most, insurance companies based upon the limited evidence upon which to judge effectiveness.54-55 Iwatsuki, et al., noted a > 70 percent pain reduction in 17 of 21 patients undergoing laser neurolysis to the lumbar dorsal facet capsule, with the four failures being among the six patients who had undergone prior spine surgery.56

Andres, et al., found no difference in VAS outcomes between the laser denervation group, showing 3.5 improvement as compared to those having standard facet denervation, with 3.3 improvement.57 Even more important to the conservative practitioner is that these levels of "success", generally amounting to a > 50 percent reduction in pain, or a 2-3 point improvement on the VAS scale,58 may be no better than what had already been achieved from the non-allopathic care that had been provided.

Intradiscal electrothermal therapy (IDET) is felt to be an option for patients in the subacute stage of back pain. Selection criteria include: no neurologic deficit, T2 images of disc desiccation, >50 percent of disc height remaining, concordant pain on low-pressure discography, and annular disruption seen on post-discogram CT scan. One study notedthat three out of four patients meeting these criteria will experience a minimally clinically important improvement in pain, considered to be at least 2 points on a 10-point scale.59

Another study found that 40 percent of patients attained > 50 percent relief, while 50 percent experienced no clinical benefit.60 And Freeman, et al., found no difference between IDET and sham treatment.61

A Cochrane review in 2007 illustrated the paucity of evidence regarding minimally invasive percutaneous disc surgery. They concluded that microdiscectomy had comparable results to standard discectomy, three small RCTs of laser discectomy provided no evidence of efficacy, and that evidence was lacking regarding other percutaneous discectomy techniques.62

Since then, a few others have also studied these interventions. Chang, et al., found that patients undergoing MIS disc decompression had similar outcomes, longer operative times, a shorter hospital stay, less blood loss, and a greater chance of recurrent herniation than those undergoing standard discectomy.63 Smith, et al., noted that four randomized trials after the 2007 Cochrane review showed no difference in outcomes between microdiscectomy, endoscopic discectomy, and standard discectomy; and that the largest trial showed an increase in complication rate in the endoscopic discectomy group.64

Almost any spinal fusion procedure can now be performed in a "minimally invasive" fashion. However, as with the other procedures discussed, a lack of high-quality comparative research limits our ability to reliably determine the benefit of and indications for of these procedures. The learning curve is steep, with an estimated 11 percent complication rate including durotomy, neural injury, hardware malposition and non-union.65

A recent study of MIS-TLIF for chronic low back pain, non-responsive to conservative care, noted that average VAS and Oswestry scores improved from 7.0 and 43.1 percent preoperatively to 3.5 and 28 percent postoperatively. The authors considered a 2.5 reduction in VAS and 40 percent improvement in Oswestry as being indicative of clinical benefit. Interestingly, out of the 210 chronic pain patients who received unsuccessful conservative care, only 11 were seen by a doctor of chiropractic.66

The Take-Home Message

The lure of anything "minimally invasive" can be significant, especially when promoted to those suffering debilitating pain. As educated clinicians, it is up to us to provide our patients with rational and balanced guidance, and avoid falling prey to hype that may supersede reality.

It is not that these procedures discussed, which are just the tip of the iceberg, are inappropriate; it is that they should not be considered a "cure-all." This is especially true for those receiving conservative who may already have attained results comparable to what can be expected with these more aggressive measures.


  1. Singh V, Manchikanti L Calodney AK, et al. Percutaneous lumbar laser disc decompression: an update of current evidence. Pain Physician, 2013;16:SE229-SE260.
  2. Oppenheimer JH, DeCastro I, McDonnell DE. Minimally invasive spine technology and minimally invasive spine surgery: a historical review. Neurosurg Focus, 2009 Sep;27(3):E9.
  3. Le TV, Burkett CJ, Deukmedjian AR, Uribe JS. Postoperative lumbar plexus injury after lumbar retroperitoneal transpsoas minimally invasive lateral interbody fusion. Spine, 2013 Jan 1;38(1):E13-20.
  4. Ahn Y, Lee HY, Lee S-H, et al. Dural tears in percutaneous endoscopic lumbar discectomy. Eur Spine J, 2011;20:58-64.
  5. Saetia K, Phankhongsab A, Kuansongtham V, Paiboonsirijit S. Comparison between minimally invasive and open transforaminal lumbar interbody fusion. J Med Assoc Thai, 2013 Jan;96(1):41-6.
  6. Lau D, Han SJ, Lee JG, Lu DC, Chou D. Minimally invasive compared to open microdiscectomy for lumbar disc herniation. J Clin Neurosci, 2011 Jan;18(1):81-4.
  7. Singh V, Manchikanti L, Benyamin RM, Helm S, Hirsch JA. Percutaneous lumbar laser disc decompression: a systematic review of current evidence. Pain Physician, 2009 May-Jun;12(3):573-88.
  8. Habib A, Smith ZA, Lawton CD, Fessler RG. Minimally invasive transforaminal lumbar interbody fusion: a perspective on current evidence and clinical knowledge. Minim Invasive Surg, 2012.
  9. Smith L. Enzyme dissolution of the nucleus pulposus in humans. JAMA, 1964;187:137-140.
  10. Yasargil M. Microsurgical Operation for Herniated Disc. In: Wullenweber R, Brock M, Hamer J, Klinger M, Spoerri O (eds): Advances in Neurosurgery. Berlin, Springer-Verlag, 1977, p. 81.
  11. Ascher PW, Heppner F. CO2-laser in neurosurgery. Neurosurg Rev, 1984;7:123-133.
  12. Mayer HM, Brock M. Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg, 1993;78:216-225.
  13. Richter E, Rothstein L. Minimally invasive, anterior epidural, endoscopic disc and neural decompression. JNSR, 2011:20-28.
  14. Foley KT, Gupta SK. Percutaneous pedicle screw fixation of the lumbar spine: preliminary clinical results. J Neurosurg, 2002;97:7-12.
  15. Marotta N, Cosar M, Pimenta L, Khoo LT: A novel minimally invasive presacral approach and instrumentation technique for anterior L5-S1 intervertebral discectomy and fusion: technical description and case presentations. Neurosurg Focus, 2006;20:E9.
  16. "What Are the Current MIS Treatments?" Society for Minimally Invasive Spine Surgery.
  17. Laser Spine Institute: Procedures. www.laserspineinstitute.com
  18. Joo YC, Park JY, Kim KH. Comparison of alcohol ablation with repeated thermal radiofrequency ablation in medial branch neurotomy for the treatment of recurrent thoracolumbar facet joint pain. J Anesth, 2013 Jun;27(3):390-5.
  19. North American Spine Institute: http://northamericanspine.com/spine-procedure/minimally-invasive/
  20. Staender M, Maerz U, Tonn JC, Steude U. Computerized tomography-guided kryorhizotomy in 76 patients with lumbar facet joint syndrome. J Neurosurg Spine, 2005 Dec;3(6):444-9.
  21. Manchikanti L, et al. An update of comprehensive evidence-based guidelines for interventional techniques in chronic spinal pain. Part II: guidance and recommendations. Pain Physician, 2013 Apr;16(2 Suppl):S49-283.
  22. Schenk B, Brouwer PA, Peul WC, van Buchem MA. Percutaneous laser disk decompression: a review of the literature. AJNR, 2006 Jan;27:232-35.
  23. Chen YC, et al. Intradiscal pressure study of percutaneous disc decompression with nucleoplasty in human cadavers. Spine, 2003;28:661-665.
  24. Singh V, Manchikanti L, et al. Systematic review of percutaneous lumbar mechanical disc decompression utilizing DeKompressor. Pain Physician, 2009;12:589-599.
  25. Buric J, Molino Lova R. Ozone chemonucleolysis in non-contained lumbar disc herniations: a pilot study with 12 months follow-up. Acta Neurochir Suppl, 2005;92:93-7.
  26. Manchikanti L, Singh V, Falco FJ, Calodney AK, Onyewu O, Helm S II, Benyamin RM, Hirsch JA. An updated review of automated percutaneous mechanical lumbar discectomy for the contained herniated lumbar disc. Pain Physician, 2013 Apr;16(2 Suppl):SE151-84.
  27. Arts MP, Brand R, van den Akker ME, et al. Tubular diskectomy vs conventional microdiskectomy for sciatica: a randomized controlled trial. JAMA, 2009;302:149-158.
  28. Dasenbrock HH, Juraschek SP, Schultz LR, et al. The efficacy of minimally invasive discectomy compared with open discectomy: a meta-analysis of prospective randomized controlled trials. J Neurosurg Spine, 2012 May;16(5):452-62.
  29. Lee SH, Kang HS. Percutaneous endoscopic laser annuloplasty for discogenic low back pain. World Neurosurg, 2010 Mar;73(3):198-206.
  30. Manchikanti L, Falco FJ, Benyamin RM, et al. An update of the systematic assessment of mechanical lumbar disc decompression with nucleoplasty. Pain Physician, 2013 Apr;16(2 Suppl):SE25-54.
  31. Goldstein CL, Macwan K, Sundararajan K, Rampersaud YR. Comparative outcomes of minimally invasive surgery for posterior lumbar fusion: a systematic review. Clin Orthop Relat Res, 2014 Jan 25.
  32. Deyo RA, Rainville J, Kent DL. What can the history and physical examination tell us about low back pain? JAMA, 1992;288:760.
  33. Balagué F, Mannion AF, Pellisé F, Cedraschi C. Non-specific low back pain. Lancet, 2012;379:482-91.
  34. Boden SD, et al. Abnormal magnetic resonance scans of the lumbar spine in asymptomatic subjects: a prospective investigation. J Bone Joint Surg (Am), 1990; 72A:403-408.
  35. Jarvik JJ, et al. The longitudinal assessment of imaging and disability of the back. Spine, 2001;26:1158-66.
  36. Masui T, et al. Natural history of patients with lumbar disc herniation observed by magnetic resonance imaging for minimum 7 years. J Spinal Disord Tech, 2005 Apr;18(2):121-126.
  37. Weishaupt D, et al. MRI of the lumbar spine: prevalence of intervertebral disc extrusion and sequestration, nerve root compression and plate abnormalities, and osteoarthritis of the fact joints in asymptomatic volunteers. Radiology, 1998;209:661-666.
  38. Rubinstein SM, van Tulder M. A best-evidence review of diagnostic procedures for neck and low-back pain. Best Practice & Research Clinical Rheumatol , 2008;22(3):471–482.
  39. May S, Littlewood C, Bishop A. Reliability of procedures used in the physical examination of non-specific low back pain: a systematic review. [Aust J Physiother], 2006;52(2):91-102.
  40. van Tulder M, Rubinstein SM. Op Cit.
  41. Beynon R, Hawkins J, Laing R, et al. The diagnostic utility and cost-effectiveness of selective nerve root blocks in patients considered for lumbar decompression surgery: a systematic review and economic model. Health Technol Assess, 2013 May;17(19).
  42. Carragee EJ, Chen Y, Tanner CM, et al. Provocative discography in patients after limited lumbar discectomy: a controlled, randomized study of pain response in symptomatic and asymptomatic subjects. Spine, Dec 1 2000;25(23)
  43. Wolfer LR, Derby R, et al. Systematic review of lumbar provocation discography in asymptomatic subjects with a meta-analysis of false-positive rates. Pain Physician, 2008;11.
  44. http://northamericanspine.com/spine-pain/patient-information-presentation/
  45. Al Nezari NH, Schneiders AG, Hendrick PA. Neurological examination of the peripheral nervous system to diagnose lumbar spinal disc herniation with suspected radiculopathy: a systematic review and meta-analysis. Spine J, 2013 Jun;13(6).
  46. Rubinstein SM, Pool JJM, van Tulder MW, et al. A systematic review of the diagnostic accuracy of provocative tests of the neck for diagnosing cervical radiculopathy. Eur Spine J, 2007:
  47. AANS / CNS Joint Section on Disorders of the Spine and Peripheral Nerves: 2005 Lumbar Fusion Guidelines.
  48. Andrade NS, Flynn JP, Bartanusz V. Twenty-year perspective of randomized controlled trials for surgery of chronic non-specific low back pain: citation bias and tangential knowledge. Spine J, 2013 Sep 5.
  49. Weinstein J, Lurie JD, Olson P, et al. United States trends and regional variations in lumbar spine surgery: 1992-2003. Spine, 2006 Nov 1;31(23).
  50. Rajaee SS, Bae HW, Kanim LE, Delamarter RB. Spinal fusion in the United States: analysis of trends from 1998 to 2008. Spine, 2012 Jan 1;37(1).
  51. Society for Minimally Invasive Spine Surgery: Candidates for Surgery.
  52. Birkenmaier C, Chiu J, Fontanella A, Leu H. Guidelines for Percutaneous Endoscopic Spinal Surgery. International Society for Minimal Intervention In Spinal Surgery, February 2010. www.ismiss.com
  53. Woeltjen B, Jones SC. "The History, Current Treatment, and Future Outlook of Minimally Invasive Posterior Lumbar Disc Surgery."
  54. Blue Cross Blue Shield of Western New York. Protocol: Facet Joint Denervation, July 2013.
  55. Premera Blue Cross: Facet Joint Denervation. December 2013.
  56. Iwatsuki K, Yoshimine T, Awazu K. Alternative denervation using laser irradiation in lumbar facet syndrome. Lasers Surg Med, 2007 Mar;39(3).
  57. Andres RH, Graupner T, Bärlocher CB, Augsburger A, Fandino J. Laser-guided lumbar medial branch kryorhizotomy. J Neurosurg Spine, 2010 Sep;13(3).
  58. Binder DS, Nampiaparampil DE. The provocative lumbar facet joint. Curr Rev Musculoskelet Med, 2009.
  59. Kloth DS, Fenton DS, Andersson GBG, et al. Intradiscal electrothermal therapy (IDET) for the treatment of discogenic low back pain: patient selection and indications for use. Pain Physician, 2008 Sep-Oct;11(5).
  60. Pauza KJ, Howell S, Dreyfuss P, et al. A randomized, placebo-controlled trial of intradiscal electrothermal therapy for the treatment of discogenic low back pain. Spine J, 2004.
  61. Freeman BJ, Fraser RD, Cain CM, et al. A randomized, doubleblind, controlled trial: intradiscal electrothermal therapy versus placebo for the treatment of chronic discogenic low back pain. Spine, 2005;30:2369-2377.
  62. Gibson JN, Waddell G. Surgical interventions for lumbar disc prolapse: updated Cochrane Review. Spine, 2007 Jul 15;32(16).
  63. Chang X, Chen B, Li HY, et al. The safety and efficacy of minimally invasive discectomy: a meta-analysis of prospective randomised controlled trials. Int Orthop, 2014 Apr 11.
  64. Smith N, Masters J, Jensen C, et al. Systematic review of microendoscopic discectomy for lumbar disc herniation. Eur Spine J, 2013 Nov;22(11).
  65. Sclafani JA, Kim CW. Complications associated with the initial learning curve of minimally invasive spine surgery: a systematic review. Clin Orthop Relat Res, 2014 Feb 8.
  66. Perez-Cruet MJ, Hussain NS, White GZ, et al. Quality-of-life outcomes with minimally invasive transforaminal lumbar interbody fusion based on long-term analysis of 304 consecutive patients. Spine, 2014 Feb 1;39(3):E191-E198.

Page printed from: