Minimally invasive spine surgeries (MISS)

1. Apollo Medicine 2012 December
Theme Symposium
Volume 9, Number 4; pp. 307e311
Minimally invasive spine surgeries (MISS)
Ashish Jaiswal*
ABSTRACT
Minimally invasive spine surgeries (MISS) since its inception around 15 years ago has undergone rigorous changes
with ever evolving technologies. Minimally invasive spine surgeries with “percutaneous” and “tubular” approaches is
based on novel concept of minimizing collateral soft tissue damage, while achieving surgical goal in various spinal
pathologies. MISS has been applied to simple spinal procedures of discectomy, decompression and fusion to even
complex surgeries like deformity correction. MISS vis a vis “conventional open techniques” has benefits in terms of
postoperative pain, concurrent tissue damage, disruption of spinal stabilizing structures, estimated blood loss, need
of blood transfusion, length of hospital stay, surgical site infections, time to ambulation and functional recovery.
However MISS is associated with steeper learning curve, poorer surgical orientation, higher peroperative ionizing
radiation to patient and surgical team, higher incidence of incidental durotomies, dependency on technology, and
higher upfront cost of treatment.
Copyright © 2012, Indraprastha Medical Corporation Ltd. All rights reserved.
Keywords: Minimally invasive, Spine surgeries, Tubular, Percutaneous
INTRODUCTION applications of MISS is expanding to include even complex
surgeries like spinal deformity correction.
Minimally invasive spine surgeries (MISS) are based on
concept of decreased concurrent tissue damage while per-
forming index procedures in spine for treating various MUSCLE PRESERVATION e THE KEY
spinal pathologies. The purported advantages of minimally CONCEPT IN MISS
invasive spine surgery are less blood loss, lesser surgical
morbidity, need of blood transfusion, lesser postoperative It is known that traditional open approaches to spine
analgesic requirement, less hospital stay and early rehabili- surgery lead to increased paraspinal muscle injury
tation with functional resumption.1e6 Minimally invasive following denervation, ischemia secondary to prolonged
spine surgery has come a long way since its inception. retraction and detachment of musculotendinous junction.
There has been constant endeavor to minimize the collateral Denervation and ischemia can result from direct injury to
surgical damage while achieving the surgical goal. There dorsal roots and vasculature in extensive surgical exposure,
have been many revolutions in this field including introduc- and also occurs due to increased intramuscular edema and
tion of microscopes, endoscopes, specialized tubular and resultant focal compartment syndrome secondary to pro-
expandable retractors. Availability of better instrumentation longed strong retraction. This has a clinical implication in
has facilitated the minimization of surgical approach. MISS the form of increased postoperative backache. The major
is commonly applied in various common spinal procedures advantage of MISS is preservation of paraspinal muscula-
like discectomies, decompression and fusion. With time the ture especially multifidous insertion in spinous process.7
Senior Consultant, Department of Orthopaedics and Spine Surgery, Apollo Hospitals, Seepat Road, Bilaspur, Chhattisgarh 645009, India.
*
Corresponding author. Tel.: þ91 9630005676, email: drashishjaiswal@yahoo.com
Received: 3.9.2012; Accepted: 24.9.2012; Available online 4.10.2012
Copyright Ó 2012, Indraprastha Medical Corporation Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.apme.2012.09.003

2. 308 Apollo Medicine 2012 December; Vol. 9, No. 4 Jaiswal
Disruption of the midline supraspinous and interspinous discectomy has an advantage in morbidly obese patients
ligament complex in conventional open approaches can where surgical exposure through tubular retractor is better
lead to loss of tension band and thus can result in late post- attained than with conventional retractors used in micro
operative instability. MISS avoids the loss of integrity of discectomy.6
this midline supraspinous/interspinous complex which in Percutaneous transforaminal endoscopic discectomy
addition to providing structural stability to spine, also acts under local anesthesia is another way of doing MISS for
as a tie beam for effective functioning of paraspinal discectomy. Yeung and Hoogland are credited for the
muscles.2 Moreover, less muscle disruption in MISS also development of the Yeung Endoscopic Spine System
leads to decreased blood loss and lesser surgical stress (YESS) in 199711 and the Thomas Hoogland Endoscopic
response. Spine System (THESSYS) in 1994, respectively.12 The
purported advantages are avoidance of general anesthesia,
smaller skin incision, conduction as a day care surgery
MINIMALLY INVASIVE LUMBAR and intraoperative active feedback of patient about allevia-
DISCECTOMIES tion of radicular symptoms. However, it is not without limi-
tations, being applicable for specific types of disc
Lumbar discectomy has undergone a radical change in herniations and necessitates even steeper learning curves.
approach since its first description by Mixter and Barr using Superiority of percutaneous techniques over conventional
laminectomy in 1934. Progressively, it was noted that the microdiscectomy still remains unclear as similar outcomes
goal of discectomy and decompression is achievable with has been demonstrated with both methods.
lesser invasive approaches. Introduction of use of microscope
for discectomy by Yasargil and Caspar revolutionized this
procedure and still microdiscectomy is considered as MINIMALLY INVASIVE TRANSFORAMINAL
a “gold standard”. MISS was described by Foley and Smith LUMBAR INTERBODY FUSION
in 1997 for discectomy using tubular retractors. This relies
on dilating the way through muscle fibers rather than stripping Lumbar fusion is commonly done for spinal instability or
it from lamina and spinous process. Endoscope or microscope deformity resulting from spondylolisthesis or scoliosis as
can be used as an adjunct for visualization. Many spine well as low back pain from degenerative disc disease refrac-
surgeons prefer using microscope owing to 3-Dimensional tory to conservative treatment. Interbody fusion is the most
visualization and also, as most of them are already acquainted preferred approach for lumbar fusion as it facilitates larger
with use of microscope, while with endoscope, it has limita- surface of fusion bed, opening up of neural foramen through
tion of 2-Dimensional vision and one needs an additional skill “jack up effect” and additional anterior stability when a cage
to master due to unfamiliarity. However superiority of MISS is placed. Currently, transforaminal lumbar interbody fusion
over microdiscectomy is debated by some as, in microdiscec- (TLIF) is most commonly performed for lumbar arthrodesis,
tomy, already there is a minimal surgical exposure and long as TLIF provides exposure of the disc space while requiring
term results of both the approaches have been found to be less dural and nerve root retraction. However in traditional
similar.6 Adequate decompression, regardless of the operative open approach TLIF requires extensive surgical exposure.
approach used, may be the primary determinant of radicular The iatrogenic injury of muscle and soft tissue is an impor-
pain relief. Adversely, it has been noted that there is a higher tant cause of postoperative low back pain which might even
of incidental durotomy in minimally invasive discectomy8 counteract the effects of surgery and sometimes labeled as
with possible explanation being limited visualization, poor “fusion disease.” MISS transforaminal lumbar interbody
depth perception and steep learning curve. Some argue that fusion using nonexpendable or expandable tubular retractor
microdiscectomy can itself be considered as a minimally inva- and bilateral percutaneous screw placement reduces such
sive procedure for discectomy and controversy persists collateral soft tissue damage and has shown to produce
whether to stick to age old microdiscectomy or to adopt favorable outcomes in respect to postoperative back pain,
tubular discectomy where again, even an experienced spine total blood loss, need for transfusion, length of hospital
surgeon needs to tide over a steep learning curve. However, stay, time to ambulation and functional recovery.4,5 Iliac
MISS seems to be more beneficial for spinal procedures crest autograft remains the gold standard, with the osteo-
with extensive surgical exposure and soft tissue disruption genic, osteoinductive, and osteoconductive components
like spinal instrumentation and fusion.4,5,9,10 It can be argued required to achieve fusion, but it comes with associated
that discectomy is the most common surgery in spine, hence donor site morbidity. Majority of spine surgeons use locally
one should master MISS for discectomy before graduating harvested bone from bony decompression as a graft to avoid
to more extensive procedures with MISS. Minimally invasive donor site morbidity. However in MISS transforaminal

3. Minimally invasive spine surgeries (MISS) Theme Symposium 309
interbody fusion when the amount of local graft is inade- MISS has a potential to reduce the approach-related
quate or even otherwise allograft or bioactive agent like morbidity associated with conventional techniques which
recombinant human bone morphogenetic protein (rhBMP- is even more crucial in setting of pre-existing injury.
2) can be added to facilitate fusion. However MISS has limited indications in thoracolumbar
injuries. Pure osseous injuries like bony chance fractures
are ideally suited for MISS fixations where one can do
MINIMALLY INVASIVE DECOMPRESSIONS IN away without bone grafting and decompression.9 Fixation
LUMBAR CANAL STENOSIS in such a pure osseous injury has further advantage of
possibility of implant removal with restoration of spinal
Lumbar canal stenosis (LCS) is a common degenerative mobility.9 Spinal fractures needing decompression may be
process among the elderly leads to progressive neurogenic fixed with percutaneous instrumentation and decompression
claudication and often needs surgical decompression to can be achieved with expandable tubular retractors or ante-
alleviate the associated symptoms and disability. Indeed, rior laproscope/thoracoscopic decompressions.10 However
LCS is the most common indication for surgery of the spine one has to conversant with all the procedures and carefully
in patients over the age of 65 years. Conventionally lumbar select fractures types amenable for such MISS interven-
laminectomy was indicated surgical procedure for LCS. tions. Specific clinical indications for MISS interventions
However with advances in noninvasive imaging especially in spinal fractures are still evolving.
MRI, it was noted that most of these pathologic compres- Percutaneous vertebroplasty and kyphoplasty are mini-
sive changes typically occur at the level of the interlaminar mally invasive procedures when performed in symptomatic
window, hence it seems more prudent to do focal decom- osteoporotic vertebral fractures provides dramatic pain
pression at level of compression rather than wide laminec- relief to patients who are not responding to conservative
tomy. The ultimate goal, regardless of the technique used, is care.13 Vertebroplasty entails the percutaneous injection
to perform an effective decompression of the affected thecal of bone cement into the fractured vertebra, while kypho-
sac and nerve root. Current MISS techniques for decom- plasty addresses pain and kyphotic deformity by the percu-
pression avoids collateral damage and have successfully taneous expansion of an inflatable bone tamp to effect
shown to shorten hospital recovery times, reduce intraoper- fracture reduction before cement deposition in a fractured
ative complications, and minimize soft tissue trauma with vertebra.
resultant decrease in surgical stress response which is
a crucial factor in consideration in elderly patients.1e3
There has been constant endeavor to adopt a minimally SUMMARY
destructive method to attain aimed surgical neural decom-
pression in lumbar canal stenosis. Various methods of Although the authoritative definition of minimally invasive
less invasive approaches namely spinous process splitting spine surgery remains elusive, the one proposed in
approach, bilateral laminotomies, bilateral decompression summary statement published by McAfee et al14 looks
via unilateral laminotomy etc has been described. MISS most apt. “An MISS is one that by virtue of the extent
for lumbar canal stenosis using tubular retractors aided by and means of surgical technique results in less collateral
endoscope or microscope has been employed successfully tissue damage, resulting in measurable decrease in
to treat LCS.1e3 However, limitation of MISS in LCS morbidity and more rapid functional recovery than tradi-
decompression is that it may fail to provide an adequate tional exposures, without differentiation in the intended
decompression in patients with bony foraminal stenosis. surgical goal.” Growing experience with MISS techniques
In patients with lumbar stenosis in the setting of spondylo- by operating surgeons and development of newer instru-
listhesis, scoliosis, or severe degenerative disc disease, the mentation by manufactures are now enabling an increas-
inherent destabilizing nature of posterior decompression, ingly large portion of spine surgical procedures to be
even using MISS, may warrant a fusion operation in addi- performed via minimally invasive techniques.
tion to decompression.3 Extensive tissue trauma in traditional surgical exposures
cause exaggerated surgical stress response and leads to
variety of complications like deep venous thrombosis,
MINIMALLY INVASIVE FIXATIONS IN THOR- pulmonary embolism, pulmonary atelectasis, pneumonia,
ACOLUMBAR TRAUMA urinary tract infections, ileus, narcotic dependency etc.
Indeed, the greater the trauma, the greater the response.
Conventional spine exposures add to pre-existing paraspi- MISS plays an important role in reduction of this surgical
nal soft tissue injury secondary to trauma in spinal injuries. stress response and associated complications.7

4. 310 Apollo Medicine 2012 December; Vol. 9, No. 4 Jaiswal
Short term benefit like lower intraoperative blood loss, MISS is an exciting development in field of spine surgery
fewer infections, less intensive care utilization, less postoper- and to some extent has stood its promise and scientifically
ative analgesia, and shorter hospitalization with MISS vis ratified. However there is a need of high quality multicentre
a vis traditional open surgeries are more as compared to long randomized control studies with large study population to
term benefits. MISS techniques may reduce postoperative clearly elucidate the advantages and disadvantages of
wound infections as much as 10-fold compared with other MISS before it is accepted as a “Gold standard” in spinal
large series of open spinal surgery published in the literature.15 surgeries. Moreover clinicians and researchers need to
The steep learning curve of MISS has been one of the constantly endeavor to find out ways to simplify the proce-
greatest barriers to the widespread adoption of minimally dure, reduce the financial implications, reduce the steep
invasive spine surgery. The surgeon practicing this needs learning curve, improve clinical accuracy, reduce peropera-
a specialized training and experience. He should be expert tive radiation and broaden the clinical applications of MISS.
in doing open surgeries too, as at times he may need to
convert to open procedure, if it is not feasible to carry on CONFLICTS OF INTEREST
with MISS. MISS has a disadvantage of being an instru-
mentation dependent procedure. MISS techniques require The author has none to declare.
an extensive knowledge of the focal structural/radiological
anatomy and safe surgical corridors of spinal region of
interest.16 Additionally, one should be aware of possible REFERENCES
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