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.

1. Minimally invasive spine surgeries (MISS)

2. Apollo Medicine 2012 December
Volume 9, Number 4; pp. 307e311
Theme Symposium
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
Minimally invasive spine surgeries (MISS) are based on
concept of decreased concurrent tissue damage while performing index procedures in spine for treating various
spinal pathologies. The purported advantages of minimally
invasive spine surgery are less blood loss, lesser surgical
morbidity, need of blood transfusion, lesser postoperative
analgesic requirement, less hospital stay and early rehabilitation with functional resumption.1e6 Minimally invasive
spine surgery has come a long way since its inception.
There has been constant endeavor to minimize the collateral
surgical damage while achieving the surgical goal. There
have been many revolutions in this field including introduction of microscopes, endoscopes, specialized tubular and
expandable retractors. Availability of better instrumentation
has facilitated the minimization of surgical approach. MISS
is commonly applied in various common spinal procedures
like discectomies, decompression and fusion. With time the
applications of MISS is expanding to include even complex
surgeries like spinal deformity correction.
MUSCLE PRESERVATION e THE KEY
CONCEPT IN MISS
It is known that traditional open approaches to spine
surgery lead to increased paraspinal muscle injury
following denervation, ischemia secondary to prolonged
retraction and detachment of musculotendinous junction.
Denervation and ischemia can result from direct injury to
dorsal roots and vasculature in extensive surgical exposure,
and also occurs due to increased intramuscular edema and
resultant focal compartment syndrome secondary to prolonged strong retraction. This has a clinical implication in
the form of increased postoperative backache. The major
advantage of MISS is preservation of paraspinal musculature 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

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

4. Minimally invasive spine surgeries (MISS)
interbody fusion when the amount of local graft is inadequate or even otherwise allograft or bioactive agent like
recombinant human bone morphogenetic protein (rhBMP2) can be added to facilitate fusion.
MINIMALLY INVASIVE DECOMPRESSIONS IN
LUMBAR CANAL STENOSIS
Lumbar canal stenosis (LCS) is a common degenerative
process among the elderly leads to progressive neurogenic
claudication and often needs surgical decompression to
alleviate the associated symptoms and disability. Indeed,
LCS is the most common indication for surgery of the spine
in patients over the age of 65 years. Conventionally lumbar
laminectomy was indicated surgical procedure for LCS.
However with advances in noninvasive imaging especially
MRI, it was noted that most of these pathologic compressive changes typically occur at the level of the interlaminar
window, hence it seems more prudent to do focal decompression at level of compression rather than wide laminectomy. The ultimate goal, regardless of the technique used, is
to perform an effective decompression of the affected thecal
sac and nerve root. Current MISS techniques for decompression avoids collateral damage and have successfully
shown to shorten hospital recovery times, reduce intraoperative complications, and minimize soft tissue trauma with
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
destructive method to attain aimed surgical neural decompression in lumbar canal stenosis. Various methods of
less invasive approaches namely spinous process splitting
approach, bilateral laminotomies, bilateral decompression
via unilateral laminotomy etc has been described. MISS
for lumbar canal stenosis using tubular retractors aided by
endoscope or microscope has been employed successfully
to treat LCS.1e3 However, limitation of MISS in LCS
decompression is that it may fail to provide an adequate
decompression in patients with bony foraminal stenosis.
In patients with lumbar stenosis in the setting of spondylolisthesis, scoliosis, or severe degenerative disc disease, the
inherent destabilizing nature of posterior decompression,
even using MISS, may warrant a fusion operation in addition to decompression.3
MINIMALLY INVASIVE FIXATIONS IN THORACOLUMBAR TRAUMA
Conventional spine exposures add to pre-existing paraspinal soft tissue injury secondary to trauma in spinal injuries.
Theme Symposium
309
MISS has a potential to reduce the approach-related
morbidity associated with conventional techniques which
is even more crucial in setting of pre-existing injury.
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
away without bone grafting and decompression.9 Fixation
in such a pure osseous injury has further advantage of
possibility of implant removal with restoration of spinal
mobility.9 Spinal fractures needing decompression may be
fixed with percutaneous instrumentation and decompression
can be achieved with expandable tubular retractors or anterior laproscope/thoracoscopic decompressions.10 However
one has to conversant with all the procedures and carefully
select fractures types amenable for such MISS interventions. Specific clinical indications for MISS interventions
in spinal fractures are still evolving.
Percutaneous vertebroplasty and kyphoplasty are minimally invasive procedures when performed in symptomatic
osteoporotic vertebral fractures provides dramatic pain
relief to patients who are not responding to conservative
care.13 Vertebroplasty entails the percutaneous injection
of bone cement into the fractured vertebra, while kyphoplasty addresses pain and kyphotic deformity by the percutaneous expansion of an inflatable bone tamp to effect
fracture reduction before cement deposition in a fractured
vertebra.
SUMMARY
Although the authoritative definition of minimally invasive
spine surgery remains elusive, the one proposed in
summary statement published by McAfee et al14 looks
most apt. “An MISS is one that by virtue of the extent
and means of surgical technique results in less collateral
tissue damage, resulting in measurable decrease in
morbidity and more rapid functional recovery than traditional exposures, without differentiation in the intended
surgical goal.” Growing experience with MISS techniques
by operating surgeons and development of newer instrumentation by manufactures are now enabling an increasingly large portion of spine surgical procedures to be
performed via minimally invasive techniques.
Extensive tissue trauma in traditional surgical exposures
cause exaggerated surgical stress response and leads to
variety of complications like deep venous thrombosis,
pulmonary embolism, pulmonary atelectasis, pneumonia,
urinary tract infections, ileus, narcotic dependency etc.
Indeed, the greater the trauma, the greater the response.
MISS plays an important role in reduction of this surgical
stress response and associated complications.7

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Apollo Medicine 2012 December; Vol. 9, No. 4
Short term benefit like lower intraoperative blood loss,
fewer infections, less intensive care utilization, less postoperative analgesia, and shorter hospitalization with MISS vis
a vis traditional open surgeries are more as compared to long
term benefits. MISS techniques may reduce postoperative
wound infections as much as 10-fold compared with other
large series of open spinal surgery published in the literature.15
The steep learning curve of MISS has been one of the
greatest barriers to the widespread adoption of minimally
invasive spine surgery. The surgeon practicing this needs
a specialized training and experience. He should be expert
in doing open surgeries too, as at times he may need to
convert to open procedure, if it is not feasible to carry on
with MISS. MISS has a disadvantage of being an instrumentation dependent procedure. MISS techniques require
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
anatomical variations and analyze them carefully in preoperative imaging to avoid operative complications. MISS
requires significant practice and didactic training to acquire
the skills necessary to perform it safely.
MISS entails higher cost of treatment especially in
instrumented cases where the cost of dedicated implants
and instruments is more than once used in traditional
surgeries. However this increase in cost can be offset by
advantages of MISS like lesser hospital stay, lesser complications, lesser blood loss and earlier return to functional
status which allows lesser postoperative expenditure and
earlier resumption of productivity of patient.17
High radiation exposure to patient and operative team in
MISS is a cause of concern being 10e20 times greater
compared to traditional open methods.18 Instrumentation
in MISS is blindfolded and entails frequent use of fluoroscopy at multiple stages. The steep learning course in MISS
further makes the operating surgeon to use fluoroscope
frequently to assure proper placement of implants.16 In
traditional open procedures, many experienced spine
surgeons place pedicle screws with freehand technique
based on anatomical landmarks and hardly use intraoperative imaging to guide the open placement of pedicle screws,
so a requirement for numerous intraoperative radiographs in
MISS can be a considerable deterrent to the adoption of
minimally invasive techniques. Although, it has been
shown that with growing experience the amount of radiation tends to decrease but it still remains higher than traditional open approaches. Introduction of computer
navigation and continuous electromyography (EMG) monitoring as an adjunct in MISS19 has potential to reduce the
amount of radiation, but again the navigation systems are
not widely available owing to high establishment cost and
need of additional dedicated technical expertise.
Jaiswal
MISS is an exciting development in field of spine surgery
and to some extent has stood its promise and scientifically
ratified. However there is a need of high quality multicentre
randomized control studies with large study population to
clearly elucidate the advantages and disadvantages of
MISS before it is accepted as a “Gold standard” in spinal
surgeries. Moreover clinicians and researchers need to
constantly endeavor to find out ways to simplify the procedure, reduce the financial implications, reduce the steep
learning curve, improve clinical accuracy, reduce peroperative radiation and broaden the clinical applications of MISS.
CONFLICTS OF INTEREST
The author has none to declare.
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