Para – Transisthmic “Key Hole“ Technique
N. Jucopilla, C.Ferrarese, G. Mazzo, G.Tirapelle, A. Robert
ULSS n° 20 del Veneto – Ospedale di San Bonifacio, Verona
Department of Orthopedics and Traumatology of the Ospedale Zavarise
Manani San Bonifacio/ Verona, Italia
Head of Department: Dr. N. Jucopilla
The
extremely lateral disc protrusions (extraforaminal, extracanalicular) in the
field of disc protrusions represent an entity all to themselves for reasons
anatomical, clinical and surgical.
The
fundamental clinical characteristic is the fact that they concern the emerging
rather than the descending root, with a symptomatology generally more severe
and acute, often
with little
lumbar (axial) pain, but associated with neurological deficit.
In the past
underappreciated, their actual incidence is found around 4 - 12 %
The ever
increasing frequency with which they are diagnosed depends as well from refined
imaging technologies such as NMR and CT scans, as from major attention of specialists
towards this type of pathology.
The level
concerned most often is L4/ 5, followed by L3/ 4; these two disc spaces will
account for some 85% of all “lateral” lumbar protrusions.
From the
anatomical point of view it needs to be stressed that in the lumbar spine, the
length of the root canal increases progressively from L1 to L5 in relation to
an increase in peduncular diameter and the change of its orientation which
changes from vertical to oblique. Furthermore, there is an increase of size of
the isthmic part of the lamina, which is wider in the lateral part; the
superior transverse processes come down more and more as the articular
processes tend to cover more and more of the cranial and lateral parts of the
disc spaces. All these circumstances contribute to the fact that the “surgical
window” of access to the point of interest will become narrower as we go down
in the cranio – caudal direction.
Various
intralaminar approaches for the removal of lateral protrusions, be it
paraspinal or combined have been proposed until today.
All of
these will produce more or less severe iatrogenic damage due to the major
destruction of muscle tissue and the destruction of osseous and articular
structures with consecutive syndromes of scarring and instability.
In our
center, with more than a decade´s experience with the technique of Caspar we
have favored since 2001 the minimally invasive approach according to Williams
(1978), modified and personalized in order to adapt it to the lateral discal
pathologies.
This
“direct” approach to the protrusion was facilitated due to the improvement of
imaging technologies, especially NMR and CT scans which show in ever more
precise and refined images the disc pathology, defining with precision
position, extent and relations with neighboring structures.
Practically,
knowing with extreme stereotactical precision the coordinates of the
protrusion, we can plan the surgical intervention on the basis of three-
dimensional coordinates and practice a minimally invasive, direct approach.
Hence, no more a cut, but a minimal incision. Not muscular displacement, but
simply stretching, no osseous destruction, but minimal fenestration of the
lamina with a drill.
The
development in this direction of surgical techniques has resulted in the concept
of key hole surgery. This method in our opinion represents a real step ahead
towards reduced invasiveness and finds its maximum expression in the surgery of
intra- and extraforaminal lumbar and cervical protrusions.
The
technique requires an incision of a mere 15 – 20 mm and a para- or transisthmic
access. A retractor with two blades is used in transversal action.
The use of
the microscope is in mandatory after the initial phase and the removal of bone
with the drill.
For the
lateral protrusions at levels L1-L2, L2-L3 a lateral para – isthmic access is
performed with a moderate removal of the medial part of the intertransversal
ligament and the lateral branches of the flavum ligament often reaching the
isthmus; at levels L3-L4 and L4-L5 the approach is transisthmic. In L5-S1 a
minimal fenestration of the lateral facettarian isthmus is necessary.
In the
cervical spine, the approach is a refinement of the Scofield procedure (1958).
The
advantages are:
Direct
minimally invasive access to the site of pathology
Less damage
to intrinsic innervation and vascularization of the muscular masses
Integrity
of inter – transversal ligaments and muscles.
No
destruction of osteo – articular structures
No
resulting instability
Reduction
of operation time (direct access to hernia)
Disadvantages:
Steep
learning curve for those inexperienced in surgery using the microscope
In our
center we have used this method in 32 patients
L2-L3 2
L3-L4 7
L4-L5 12
L5-S1 5
Altogether
the positive results with a minimal follow – up of 6 months amount to 96 %
In the
cervical spine:
C6-C7 4
C7-T1 2
The
results, with a minimum follow – up of 6 months were positive in 100 %
In
conclusion we can confirm that the minimally invasive key hole approach, a
personal refinement of the microtechnique according to Williams, represents a
true step ahead in the treatment of disc herniation, especially in the lateral
disc protrusions.
The
absolutely mandatory condition is the knowledge of the “coordinates” of the
hernia and its relations with neighboring structures in order to facilitate a
direct aimed access, avoiding the classic wide approaches, almost always
followed by severe sequelae such as scarring and resulting instability.
It offers
undoubtable advantages such as minor invasiveness, resulting in less
postoperative pain, better esthetic result, reduction of in – patient time,
faster return to work and hence reduced costs to the health and social
institutions. Obviously it requires the use of the microscope, a high speed
drill and adequate, specialized instruments.
1
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2
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9
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