MINIMALLY INVASIVE SPINE SURGERY
From the University of California, San Diego, School of Medicine’s Minimally Invasive Surgery of the Spine
| MIS OF THE SPINE: PAST, PRESENT, AND FUTURE—Richard G. Fessler, MD, PhD, John Harper Seeley
Professor and Chief of Neurosurgery, University of Chicago Pritzker School of Medicine, 1st President of the Society
for Minimally Invasive Spine Surgery, and Chief, Section of Neurosurgery, The University of Chicago Hospitals,
Chicago, IL
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| Chemonucleolysis: chymopapain used in first minimally invasive surgery (MIS) disc procedure; learned how to
access disc radiographically and percutaneously; perhaps most minimally invasive technique; achieved good results;
why abandoned—paraplegias from original enzyme; corrected but discontinued in United States; still
used in other countries
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| Open microdiscectomy: remains gold standard; 90% to 95% good results long-term; comparatively easy operation
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| Percutaneous laser discectomy: no good studies available; theoretic advantages (atraumatic; can control
power); disadvantages (inability to remove sequestered fragment; no proven efficacy); widely viewed as
gimmick
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| Automated percutaneous discectomy: probably most studied MIS technique; initial results good; on long-
term follow-up 50% to 60% good results (little better than no surgery); problem (“you really couldn’t tell when
you were done”); never widely accepted
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| Automated arthroscopic microdiscectomy: enabled reduction of sequestered fragment; advantages include
restricted penetration of disc, biportal or uniportal capability, little soft-tissue injury, epidural bleeding, or
scarring; difficulty of procedure restricted wide acceptance
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| Intradiscal electrothermal therapy (IDET): only studies from inventor of device; ≈60% good results; barriers
to acceptance (no evidence of benefit; surgeons view as technique to allow nonsurgeons to perform procedures)
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| Percutaneous endoscopic retroperitoneal lumbar fusion (PERLF): insufflation followed by dissection to
bone and fusion; slight reduction in hospital stay and blood loss; technically difficult
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| Minimally invasive anterior lumbar interbody fusion (ALIF): advantages include decreased blood loss, reduced
hospitalization and discomfort, and avoiding dissecting posterior muscle; acceptance restricted by difficulty of
procedure, eg, need for insufflation
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| Thoracoscopy: does not require insufflation; enables discectomies, corpectomies, anterior reconstruction; advantages
include avoiding vital intrathoracic structures, direct decompression of nerve root; disadvantages include
technical difficulty, bleeding, and extensive operating room (OR) preparation
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| Vertebroplasty and kyphoplasty: equally effective; good results (pain score reduced from 9 to ≈2); few complications;
valuable percutaneous technique for compression fractures (even acute fractures)
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| Summary: techniques for minimally invasive lumbar discectomy—limited to discectomy; restricted indications;
some long-term success but no better than open microdiscectomy; relatively high reoperation rates; techniques
for anterior lumbar and thoracic surgery—good visualization; sometimes require insufflation; technically demanding;
difficult in some levels of spine; limited acceptance
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| Operating through tube revolutionary change: endoscope or microscope; routinely employed in almost every
operation; speaker not currently using for some intradural-intramedullary tumors, scoliosis, and ankylosing
spondylitis; moved from 100% open surgery in early 1990s to 98% MIS today
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| PERCUTANEOUS RADIOLOGIC ASSESSMENT—Mark J. Spoonamore, MD, Assistant Professor, Orthopaedic
Surgery, the Keck School of Medicine of the University of Southern California, and Medical Director,
USC Center for Spinal Surgery at USC University Hospital, Los Angeles
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| Definition of MIS spine surgery: combines traditional concepts of spine surgery with specialized imaging, using
smaller incisions with muscle- and tissue-sparing techniques
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| Fluoroscopy: full understanding of fluoroscopic imaging essential; limited to 1 to 2 landmarks (vs many available
in open surgery)
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| Avoid short-cuts: include same steps as open procedure; learning curve (may require more time at first)
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| Components: setup key; careful patient positioning; good quality C-arm; experienced radiology technician;
eliminate clutter, eg, wires and cables that obscure field of vision
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| Optimize imaging: place object of interest in middle one-third; en face view required (problem, using 2-D imaging
to target 3-D structures); maximize understanding of anatomy; target pedicle—position needle on pedicular
ridge; for accurate anteroposterior image, place spinous process perfectly in midline
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| Modalities of C-arm: cantilever—Ferguson views; adjusting to lordosis; over-under—patient malpositioned;
bull’s eye or oblique views; wig-wag—en face lateral view; final check—Jamshidi needle on oblique view
should be targeted directly down pike of pedicle
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| Pitfalls: using guidewires; aligning screw heads; malpositioning
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| Radiation safety: scatter exposure rate ≈5 mrem at 2 ft, 1 mrem at 4 ft; imaging spine surgery requires 10- to
20-fold increase in power compared to extremity surgery; recommended yearly limit ≈5000 mrem to torso
(≈50,000 to hand); fluoroscopy time— 15 to 30 sec for standard open 8-level pedicle subtraction osteotomy;
speaker’s last 2-level MIS case 300 sec (5 min); ≥10-fold increase even for experienced surgeon;
implications—actual risk unknown; stand as far away from beam as possible; “wear some lead”
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| MINIMALLY INVASIVE POSTERIOR LUMBAR DECOMPRESSION AND FUSION—Larry T. Khoo, MD, Associate
Professor of Neurosurgery and Orthopedics, David Geffen School of Medicine at University of California, Los Angeles,
and Chief of Neurosurgery, Santa Monica-UCLA Medical Center, Los Angeles
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| Patient example: classic case for fusion; back pain and radiculopathy; fuse for spondylitis; goals—
decompression; total discectomy for interbody fusion (posterolateral fusion associated with nonunion, especially
L5-S1)
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| Contralateral screw placement: place screws on side opposite leg pain; tap holes but do not place screws on
side to be decompressed; at end of procedure technician can insert screws under direct vision
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| Access: fixed tubes favored for 1-level procedures; expanding system preferred for 2 levels; drop tube through
transforaminal lumbar interbody fusion (TLIF) trajectory; expand tube; some systems enable expanding retractors
at variable depths
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| Surgical principles: place graft in middle; decompress; remove disc; decompress nerve root; decompress radiculopathy;
restore interbody height and sagittal balance with biggest cage possible (eg, 11 mm or 13 mm; avoid
7 mm and 9 mm); use interbody distractors; trick for success—when nerve root on top of disc, distracting pedicles
essential for space; removing facet gives access to disc space; drill with bone trap, save bone for graft
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| Graft material: alternatives if unable to afford bone morphogenic protein (BMP); bone dust compression; aspirate
hip; place in carrier or collagen sponge; extend with calcium triphosphate as matrix; pack into cage; pack
remaining 20 mL into interbody space
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| Central stenosis: during TLIF, tilt tube over to midline (angled approach) and drill across for central decompression;
can combine discectomy technique with bilateral laminectomy (spares spinous process; over multiple
levels if needed)
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| Outcome studies: speaker’s partner performs open TLIF; similar cases (spondylitis; disc herniation; degenerative
discs); no difference in fusion rates for open and MIS; advantages of MIS include shorter hospital stay, less
blood loss, reduced OR time, and less pain 7 to 21 days after surgery (hurt less and faster); MIS complications
at L5-S1 (may require alternative to TLIF)
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| Radiation exposure: speaker averages 1 to 3 min per case (longer because teaching residents); 80 cases last
year totaled 100 mrem (increasing lifetime cancer risk 1%)
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| USING NAVIGATION TO DECREASE RADIATION EXPOSURE—Choll W. Kim, MD, PhD, Assistant Professor,
Department of Orthopaedic Surgery, University of California, San Diego, School of Medicine, and Director,
UCSD Spine Fellowship Program
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| Shortcoming of MIS spine surgery: absence of real-time imaging; exposure to radiation; uncomfortable surgical
gear; awkward postioning using C-arm
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| Fluoroscopy exposure: ≈2 min for speaker's cases; National Council on Radiation Protection and Measurements
(NCRP) handbook states “extrapolation of risks from exposures at high doses, in addition to inherent experimental
errors in the data, is most likely the predominant uncertainty in the estimate of risk at low doses”;
not knowing true risk constitutes health hazard
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| MIS protective gear: circumferential skirt and vest; thyroid shield; lead-lined eye protection if possible
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| Image guided surgery (navigation): offers solution; avoids fluoroscopy; less radiation; unobstructed field; no
lead gowns; why not accepted—added preoperative imaging; image registration; fudicial points (subjective);
when introduced, fluoroscopy could be avoided
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| Virtual fluoroscopy: avoids preoperative imaging and fudicial readings; enables familiar fluoroscopy techniques;
requires attachment to fluoroscopy device; desired x-ray views taken initially and stored in image library;
screen showing 4 images simultaneously equivalent to having 4 flouroscopic devices
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| Comparison of navigation with standard fluoroscopy: MIS TLIF in 4 cadavers; MIS requires more time obtaining
images (initial set-up time); remaining times similar; radiation exposure (≈12.7 mrem with fluoroscopy; 0
with navigation [lead shield provides protection during image acquisition])
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| Prospective clinical data: compared to fluoroscopy, navigation required additional ≈20 min to obtain images;
other times similar
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| Conclusions: navigation convenient (no additional preoperative imaging); avoids intraoperative registration (fudicials);
retains familiar fluoroscopy techniques; no radiation exposure; no lead gear; expedites use of operating
microscope; appears safe; randomized controlled trial will determine efficacy
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| POSTEROLATERAL ENDOSCOPIC DISCECTOMY, DECOMPRESSION, AND NUCLEUS
REPLACEMENT—Christopher A. Yeung, MD, Volunteer Assistant Professor, Department of Orthopaedic Surgery,
University of California, San Diego, School of Medicine, and Arizona Institute for Minimally Invasive
Spine Care, Phoenix
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| Definition of procedure: visualized surgical approach for disc pathology and foraminal decompression; differs
from percutaneous discectomy-type “blind” fluoroscopically guided procedures
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| Advantages: less invasive; tissue dilation only; no destabilizing effect; avoids intracanal disruption and scarring;
allows access to “hidden zone” of MacNab
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| Indications: herniation—foraminal; extraforaminal; upper lumbar; recurrent; foraminal stenosis; discitis; discogenic
pain from anular tears; nucleus replacement (in future)
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| Standard pericentral disc herniation procedure: dock at 30° angle into disc; position beveled cannula at base
of herniation; provides endoscopic view of foramen with disc space, anulus, posterior longitudinal ligament, and
epidural space; medialize anulotomy to access disc herniation; extruded or sequestered fragments more difficult;
biportal approach—useful for large central or extruded herniation
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| Results: in prospective randomized study, results at least equal to microscopic discectomy; retrospective studies
show similar efficacy
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| Other advantages of procedure: treatment of micropathology, eg, anular tears, high intensity zones (nests of
necrotic cells; focal areas of granulation tissue in anulus); published results ≈75% satisfactory; treatment of foraminal
stenosis (laser used as fine dissecting tool)
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| Why techniques not more widely adopted: traditional microdiscectomy effective; different surgical skill set
(2-D visualization through screen); not part of training programs; no industry incentive
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Educational Objectives
| The goal of this program is to educate the listener about minimally invasive surgery (MIS) of the spine. After hearing
and assimilating this program, the clinician will be better able to:
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 | Explain the evolution of MIS of the spine and the role of newer techniques.
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| Perform a percutaneous radiologic assessment.
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| Execute minimally invasive lumbar decompression and fusion.
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| Consider adopting navigation to decrease radiation exposure.
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| Evaluate the efficacy of posterolateral endoscopic discectomy, decompression, and nucleus replacement.
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Suggested Reading
Eichholz KM et al: Thoracic microendoscopic discectomy. Neurosurg Clin N Am 17:441, 2006; Fessler RG et
al: Minimalism: is less more? Clin Neurosurg 50:220, 2003; Fessler RG et al: The development of minimally invasive
spine surgery. Neurosurg Clin N Am 17:401, 2006; Fessler RG: Minimally invasive percutaneous posterior
lumbar interbody fusion. Neurosurgery 52:1512, 2003; Fessler RG: Minimally invasive spine surgery. Neurosurgery
51:Siii, 2002; Isaacs RE et al: Thoracic microendoscopic discectomy: a human cadaver study. Spine 30:1226,
2005; Kambin P et al: Arthroscopic microdiscectomy: an alternative to open disc surgery. Mt Sinai J Med 67:283,
2000; Kesek M et al: Reduction of fluoroscopy duration in radiofrequency ablation obtained by the use of a non-
fluoroscopic catheter navigation system. Europace 8:1027, 2006; O'Toole JE et al: Minimally invasive approaches
to vertebral column and spinal cord tumors. Neurosurg Clin N Am 17:491, 2006; Saal JA et al: Intradiscal electrothermal
therapy for the treatment of chronic discogenic low back pain. Clin Sports Med 21:167, 2002; Saal JA et
al: Intradiscal electrothermal treatment for chronic discogenic low back pain: a prospective outcome study with minimum
1-year follow-up. Spine 25:2622, 2000; Tenforde TS: Future role of the NCRP in radiation health protection.
Health Phys 87:312, 2004; Tsou PM et al: Posterolateral transforaminal selective endoscopic discectomy and thermal
annuloplasty for chronic lumbar discogenic pain: a minimal access visualized intradiscal surgical procedure.
Spine J 4:564, 2004; Tsou PM et al: Transforaminal endoscopic decompression for radiculopathy secondary to intracanal
noncontained lumbar disc herniations: outcome and technique. Spine J 2:41, 2002; Yeung AT et al: Posterolateral
endoscopic excision for lumbar disc herniation: Surgical technique, outcome, and complications in 307
consecutive cases. Spine 27:722, 2002.
Faculty Disclosure
In adherence to ACCME guidelines, the Audio-Digest Foundation requests all lecturers to disclose any significant financial
relationship with the manufacturer or provider of any commercial product or service discussed. The following
has been disclosed: Dr. Fessler—Medtronics (consultant); Dr. Khoo—Abbot Spine (consultant), DePuy (consultant);
Dr. Yeung—Disc Dynamics (advisory board)
The speakers were recorded at Minimally Invasive Surgery of the Spine, sponsored by the University of California,
San Diego, School of Medicine, held November 3-4, 2006, in San Diego. The Audio-Digest Foundation thanks the
speakers and the sponsor for their cooperation in the production of this program.
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