48 The Anterior Extraperitoneal Video-assisted Approach to the Lumbar Spine
M. Onimus, H. Chataigner
48.1
Terminology
The technique described is an open, mini-invasive ap- proach to the anterior lumbar spine which can be per- formed with the help of “open” endoscopy.
48.2
Surgical Principle
The anterior lumbar spine is approached through a small anterior midline skin incision via an extraperito- neal (retroperitoneal) route: right-sided for L5-S1 ap- proach, left-sided for lumbar discs approach. Illumina- tion and magnification of the surgical field is provided by an “open” endoscopic technique. The optical system (stab lens) may be introduced toward the target area through the same skin incision or through a second, separate skin incision.
48.3 History
Endoscopic lumbar surgery has developed in two dif- ferent directions:
1. Transperitoneal laparoscopic surgery was devel- oped for laparoscopic discectomy and fusion, the advantage of which being to give an approach to the anterior aspect of the disc through a natural cavity. But there are several disadvantages to the transperitoneal approach: the need for gas insuffla- tion, the risk of peritoneal complications, and the difficulty to access the L4-5 level. Moreover, true laparoscopic surgery is demanding and special training is necessary.
2. Extraperitoneal laparoscopic surgery was initially proposed for lumbar sympathectomy. The lateral extraperitoneal approach is not subject to peritoneal complications, and this approach makes it possible to perform lateral osteosynthesis. However, the exposition is provided to the lateral part of the disc,
making it more difficult than an anterior exposure for the strict midline placement of any reconstruc- tive device, such as cages, grafts, etc. Moreover, the lateral extraperitoneal access to the lumbosacral disc is difficult and is very infrequently performed.
The minimally invasive technique of the video-assisted approach described here has the advantages of both an anterior midline and an extraperitoneal approach, with- out the specific disadvantages of laparoscopic surgery.
This approach is related more to a microsurgical open approach than to true “closed” endoscopic surgery. Disc exposition is facilitated by a specially designed self-re- taining retractor. The technique was reported in 1996 [14].
48.4 Advantages
The anterior extraperitoneal video-assisted approach is conventional surgery performed with ordinary in- struments. The advantages of this technique include the following:
An extraperitoneal approach
A wide anterior midline access to the disc An optimization with video assistance
The advantages of an extraperitoneal approach are:
Previous abdominal surgery and bowel adhesions do not make the procedure more difficult.
During surgery, the bowel is withheld by the peri- toneum and does not invade the operative area.
The risk of vascular and peritoneal complications is reduced, as well as the risk of postoperative septic complications.
The postoperative course is safer and uneventful with an early return to normal transit. The classic risk of late bowel obstruction is completely eliminated.
The advantages of an anterior midline approach are:
To give a direct access to the anterior aspect of the
disc and adjacent vertebral bodies, allowing graf-
ting in an optimal midline situation
Fig. 48.1. A massive cage, providing a large surface for fusion, may be inserted through the midline approach
To give access to all discs from L2 down to S1, us- ing a similar dissection for each level, even if the more commonly approached levels are L4-5 and L5-S1
To allow insertion of a unique ring cage, providing more stability and a wider surface of fusion be- tween graft and vertebral plates than conventional twin cages (Fig. 48.1)
The advantages of video assistance are:
To make the procedure a minimally invasive one through a keyhole incision.
To improve the lighting of the operating area.
To provide a better visualization to the presacral area, allowing an easier and more acute dissection.
Good visualization of the vertebral end plates with an angulated endoscope gives assurance of a better decortication up to the subchondral bone, thus in- creasing the fusion rate.
Compared with transperitoneal or extraperitoneal closed laparoscopic surgery, open surgery with video assistance has the advantage that there is no need for CO
2insufflation.
A last advantage is that no specific training is nec- essary. The approach is a conventional one which can be performed without video assistance or through a wider incision. A wider midline incision does not transect any muscular fibers and has no specific disadvantages. This gives the surgeon the possibility of learning the technique and progres- sively reducing the length of the incision as he/she becomes more skilful with the technique.
48.5
Disadvantages
No obvious disadvantages can be described with the extraperitoneal approach. Special attention must be given to the cleavage of the peritoneum. Cleavage of the anterior peritoneum close to the midline is difficult be- cause the peritoneum is thin and can be torn, especially in women. This is avoided by dissecting not between the posterior sheath of the rectus and the peritoneum, but anteriorly to the posterior sheath of the rectus, be- tween the sheath and the muscle. The peritoneum is more resistant on the lateral wall of the abdomen and cleavage is easier, making peritoneal tears infrequent.
The cleavage is considerably facilitated by the use of an inflatable balloon.
The anterior midline approach to L4-5 may be diffi- cult in obese patients and an anterolateral approach may be preferred (see Section 48.11.1)
The main disadvantage of the anterior approach is that a rigid osteosynthesis is usually contraindicated because of the proximity of the great vessels, except if a very low profile system is used. As a result, a posterior additional osteosynthesis may be necessary when a sol- id stabilization is required.
When a scoliotic deformity is present, an anterior midline approach does not give direct access to the ante- rior aspect of the vertebral bodies which face more later- ally because of the vertebral rotation. In such circum- stances, an anterolateral pararectal approach may be preferable, giving access to the anterior aspect of the ver- tebral bodies. Furthermore in this situation the great vessels remain more medially and are not troublesome.
There are no specific disadvantages to the use of video assistance. The endoscope can be introduced through the midline incision, avoiding an additional port and giving better endoscopic vision to the disc than through a lateral port. However, video assistance is not necessary and a headlight may provide effective lighting. The main advantage of video assistance is to give the assistants the possibility to observe the surgery.
48.6
Indications and Contraindications
This technique can be used from L2 to S1 in all situa- tions requiring an anterior approach to the lumbar spine, such as open biopsy, vertebral reconstruction, or segmental interbody fusion.
The technique can be used for open biopsy of the
lumbar vertebral bodies. However, isolated open biopsy
is not frequently indicated and in many cases a more
complex vertebral resection and reconstruction has to
be performed. This approach is not routinely considered
for vertebral reconstruction in traumatic lesions nor for
corporectomy in tumoral lesions because the proximity of the great vessels makes hazardous a stabilization by an anterior aggressive osteosynthesis. In selected cases, graft fixation can be performed using embedded screws.
The selective indication for the anterior extraperito- neal video-assisted approach is anterior interbody fu- sion (ALIF) which can be considered in two main situa- tions, both concerned with disc degeneration: painful progressive spondylolisthesis and low back pain due to degenerative disc disease.
48.6.1
Progressive Spondylolisthesis
Progression of spondylolisthesis in adults is related to disc degeneration. In L4-5 an obvious instability may be observed, suggested by a major hypermobility oc- curring in flexion and in extension. In L5-S1 the insta- bility is latent and is suggested by the slip progression with tilting of the upper vertebra in a segmental kypho- sis, and progressive disc collapse. In such situations, posterior stabilization may be insufficient to provide correction and stability and an additional anterior fu- sion may be considered. The anterior fusion can be per- formed during the posterior surgery (PLIF procedure).
However, the PLIF procedure is more aggressive for posterior structures than an ALIF procedure per- formed by a mini-invasive technique. Moreover, cor- rection of the slip and the disc collapse is easier by an anterior approach. The anterior approach is performed in a first surgical step, then the patient is turned into a prone position and an additional posterior fixation is performed during the same operative procedure.
48.6.2
Degenerative Disc Disease
Indications for surgery in low back pain by degenerative disc disease are still a challenging problem, as no un- questionable predictive criteria are available to indicate fusion. Stabilization by anterior fusion may be success- ful in relieving a discogenic pain. The aspects of disc de- generation on discogram are common and not specific;
equally the pain reproduction test is not specific as it is patient- and operator-dependent. The disc changes on MRI [12] (decreased signal on T2-weighted image) are also non-specific. More attention should be given to vertebral plates and adjacent bone marrow changes on MRI. Modic type I changes (inflammatory changes with decreased signal on T1 and increased signal on T2- weighted images) have been correlated with low back pain [18]. We observed the best results after anterior fu- sion when inflammatory changes were present on adja- cent vertebral plates [2]. The exact source of the pain, disc or vertebral plates, is unknown; however, Moore et al. [13] observed an intraosseous hyperpressure associ-
ated with Modic I changes, similar to that present in painful peripheral joint osteoarthritis, and suggesting that the recommended treatment should be stabiliza- tion by fusion (or disc prosthesis). Anterior fusion can be performed by a posterior approach, but preferably by an anterior approach, as posterior elements are intact and posterior stabilization is not indispensable. Fur- thermore, a canal exploration is unnecessary.
48.7
Patient’s Informed Consent
No specific patient’s informed consent is required be- cause this is conventional surgery, performed with or- dinary instruments. Preoperative routine information must be given to the patient with special reference to the specific complications of the anterior approach to the lumbar spine.
48.8
Surgical Technique
48.8.1
Patient Positioning
The patient is placed in a routine supine position with a pillow under the knees to have a good relaxation of the vessels. Bending the table in lordosis after exposure of the disc will widen the intervertebral space. No spe- cific preoperative bowel preparation is used, and no na- sogastric tube is placed. A urinary catheter is inserted after general anesthesia.
48.8.2 Surgical Steps 48.8.2.1
Approach to L5-S1
The surgeon stands on the left side of the patient, with one assistant standing on the right side and an addition- al assistant standing beside the surgeon who will have to hold a peritoneal retractor before insertion of the self- retaining retractor. A short 5-cm vertical skin incision is made half way between umbilicus and pubis (Fig. 48.2a).
In female patients, a more cosmetic horizontal suprapu- bic incision is possible for approaching the lumbosacral disc. Checking the right localization of the incision by imaging amplifier may be necessary, as the incision must be exactly situated in the direction of the disc.
The lumbosacral disc should be preferentially ap-
proached from the right side, because the common iliac
vein lies vertically on the lateral aspect of the disc; con-
versely the left iliac vein lies obliquely on the disc and it
has to be laterally retracted should a left approach be
a b
Fig. 48.2. a Postoperative aspect of the vertical midline skin incision for approach to the L5-S1 disc. b Postoperative aspect of the skin incision after L4-5 approach
performed; furthermore the right iliac vein is protected by the common iliac artery and is nearly not seen dur- ing the procedure. The anterior sheath of the right rec- tus abdominis is opened, and the muscle is gently pulled up, allowing it to be cleaved from its posterior sheath.
Adhesions of the muscle to the posterior sheath are not observed and the cleavage is easy. Epigastric vessels are pulled up together with the rectus abdominis muscle.
The posterior sheath of the rectus is a barrier in front of the peritoneum but it does not extend below the linea arcuata (Fig. 48.3a) and is often not necessary to be open. Occasionally an upward 1- to 2-cm incision of the posterior sheath from the linea arcuata is sufficient to give a wide exposure on the peritoneum. The dissection is continued in the extraperitoneal fascia, with progres- sive cleavage of the peritoneum from the lateral abdom- inal wall and the iliac muscle. The cleavage of the perito- neum may be difficult in cases where there has been a previous appendectomy and the peritoneal adherences should be gently released. The peritoneum is then me- dially retracted with a large retractor and the extraperi- toneal cavity is progressively enlarged A 10-mm endo- scope can be inserted either through a lateral port situ- ated at the level of the disc or through the midline inci- sion. The introduction of the endoscope gives good illu- mination and visualization to the operative field, and al- lows the operation to be continued through the midline incision, under both endoscopic and direct vision. The next landmark is the prominent psoas muscle and then
the lateral iliac artery lying on the medial side of the muscle is identified. By backward dissection of the ar- tery, the iliac bifurcation is exposed. The right iliac vein is covered by the iliac artery and is usually not seen. The lumbosacral disc is medial to the bifurcation and it can be identified by palpation as the first prominent struc- ture above the sacral concavity (Fig. 48.3b). Its anterior aspect is still covered by the fibrous and nervous tissue constituting the presacral network. These have to be progressively dissected and retracted by blunt dissec- tion with peanut swabs until the disc exposure is suffi- cient. Cauterization should be avoided because of the risk of damage to the hypogastric nerves supplying the bladder, eventually resulting in retrograde ejaculation.
The only vascular structures to be divided are the mid-
sacral vessels. They should be hemoclipped and cut,
giving a wide exposure to the disc. The ureter is usually
identified; it is adherent to the peritoneum and is medi-
ally retracted together with it. A specific self-retaining
retractor is inserted, providing a medial retraction of
the peritoneum and a lateral retraction of the iliac ves-
sels. This retractor is held in place with Steinmann pins
inserted in adjacent vertebral bodies. It is made up of
two expandable blades allowing intervertebral distrac-
tion (Fig. 48.4a). The medial blade is first inserted and
secured to the vertebral bodies of L5 and S1. Then the
lateral blade is inserted and secured. Both blades are
joined together with a half ring giving definitive stabili-
ty to the construct (Fig. 48.4b). The procedure is then
a
Fig. 48.3. a Perioperative as- pect of L5-S1 extraperitoneal approach. The posterior sheath of the rectus abdomi- nis (1) is present in the up- per part of the operative field; the peritoneum (2) can be seen below the linea arcu- ata (3). b Perioperative as- pect of the lumbosacral disc, after exposition and division of the midsacral vessels. The disc (4) is medial to the iliac bifurcation and prominent above the sacral concavity.
Iliac artery (5)
b
a b
Fig. 48.4. a The self-retaining retractor is made up of two ad-
justable lateral blades linked by a half ring and secured to the
adjacent vertebral bodies by pins. b The retractor in place dur-
ing an L5-S1 approach. An additional third blade (1) is secured
to the half ring (2) and can be inserted for cranial retraction of
the peritoneum if needed
a b
Fig. 48.5. a Preoperative ra-
diograph of a patient pre- senting with a degenerative painful lumbosacral disc.
b Postoperative radiograph after anterior extraperitone- al approach and insertion of a massive ring cage filled with iliac graft. The cage is screwed to the adjacent vertebral bodies. Screwing provides primary stability making a posterior fixation unnecessary
carried on, still under endoscopic illumination and still through the midline incision, with disc excision and vertebral plates decortication. A powerful interverte- bral distraction is performed with a long-arm spreader, giving a normal intervertebral height and widening the foramen. Then fusion can be performed. A ring cage filled with cancellous iliac graft is inserted and screwed into the adjacent vertebral bodies (Fig. 48.5a, b).
The wound is closed after insertion of a retroperito- neal suction tube; the only structures to be sutured are the anterior sheath of the rectus abdominis muscle, the subcutaneous fascia, and the skin.
48.8.2.2
Approach to Lumbar Discs
The routine approach to lumbar discs is left sided. The surgeon stands on the right side of the patient, with an assistant standing on the left side and an additional as- sistant beside the surgeon on his left. It is important to have both hips of the patient slightly flexed during the approach in order to have relaxation of the iliac vessels, making it easier for their dissection and retraction. The operating room table will be curved in lordosis after the disc exposure.
For the approach to L4-5, a 5-cm vertical incision is centered on the umbilicus (Fig. 48.2b); for the approach to L2-3 and L3-4 the incision is made above the umbili- cus; fluoroscopic control may be necessary to ensure the right alignment of the incision in the axis of the disc. The approach is similar to the L5-S1 approach, with incision of the left rectus anterior sheath and re-
traction of the muscle together with its anterior sheath.
The approach is performed above the linea arcuata and
the posterior sheath is a continuous barrier which has
to be divided at the lateral side of the rectus in order to
enter the extraperitoneal space. A small orifice is
opened in the posterior sheath of the rectus and an in-
flatable balloon is introduced in the extraperitoneal
fascia and pushed down in the lateral lumbar area. The
insufflation of the balloon provides complete cleavage
of the peritoneum from the posterior sheath and from
the lateral abdominal wall. After removal of the bal-
loon, the posterior sheath is easily divided and the ex-
traperitoneal cavity can be progressively enlarged with
medial retraction of the peritoneum. The ureter is re-
tracted together with the peritoneum. The endoscope
is introduced through a lateral port or through the mid-
line incision. The next landmark is the psoas muscle,
which is identified as the first prominent structure on
the posterior area. The muscle is progressively ex-
posed; the dissection becomes more superficial on the
anterior aspect of the psoas muscle and it should not be
carried on deeply at the lateral side of the muscle where
the lumbar roots can be injured. The approach to the
lumbar discs is lateral to the great vessels; these have to
be gently dissected and medially retracted until disc ex-
posure is sufficient. Then the retractor is inserted and
secured.
48.9
Postoperative Care
Liquid alimentation is allowed on the first postopera- tive day, with progressive return to normal alimenta- tion after bowel evacuation (usually by the third post- operative day). The patient is allowed to stand up on the second postoperative day. A lumbosacral orthosis is prescribed for 2 months and should be worn during daily activities, being removed at night. Sitting in a deep arm chair is restricted; patients are advised to sit on a stool or on the edge of a chair, keeping a straight lumbar spine.
48.10
Hazards and Complications
The complications observed were listed from a series of 90 patients, all of them operated on with the technique.
48.10.1
Perioperative Complications
Only vascular complications have been observed: five perioperative iliac vein injuries occurred during the L4- 5 (three cases) and L5-S1 (two cases) approaches. In one case, a lumbar vein avulsion occurred during the disc exposure. In four cases the operation was uneventful;
the vein injury probably occurred during the exposure and the bleeding occurred at the end of the procedure, at removal of the retractor. In all cases the bleeding was controlled by suture or hemoclip without enlarging the approach. Perioperative injury to the great vessels is a well-known complication reported in conventional an- terior surgery: the 15 % rate in Baker et al.’s series [1] is consistent with the 5 % incidence observed in our re- view. Venous injuries are more frequent than arterial in- juries. According to the literature, most of the injuries are small tears, easily treated by a clip or a stitch. Ac- cording to some investigators, venous repair often re- sults in secondary thrombosis; however, we did not ob- serve this complication. No perioperative peritoneal, gastrointestinal, neurologic or urologic complications were observed. The overall incidence of perioperative severe complications after conventional extraperitoneal approach is equally low; the 38 % incidence in Rajama- ran et al.’s review [15] included many minor complica- tions. Most of the complications in Escobar et al.’s re- view [5] occurred during the transperitoneal approach.
48.10.2
Postoperative Complications
The main complication to avoid at the L5-S1 level is postoperative retrograde ejaculation due to presacral
nerve injury. The reported incidence is highly variable:
1 case out of 55 in Flynn and Price’s series [6]; 2 cases out of 50 in Christensen and Bunger’s series [4]; 9 cases out of 40 (17 %) in Tiusanen et al.’s series [17]; 6 cases out of 146 (4 %) in Sasso et al.’s review [16]; and 4 cases out of 50 (8 %) in Escobar et al.’s series [5]. We observed 2 cases out of 20 (10 %), one of them resolving at the sixth postoperative month. The exact incidence of this complication is still controversial, as the published se- ries often do not separate the material by gender nor by the operated levels. It should occur specifically after ap- proach to the lumbosacral disc where the dissection of the presacral area may damage the sympathetic fibers supplying the bladder. There is no unanimously accept- ed consensus regarding the prevention; the left and transperitoneal approaches should be more aggressive than the extraperitoneal and right approaches [6, 7, 16, 17]. According to the literature, it is important to per- form a gentle and bloodless dissection, without electro- cauterization, and with careful retraction of any vertical structure lying in front of the lumbosacral disc. Howev- er, some fibers are extremely tight against the disc and difficult to retract, and the risk should be seriously tak- en in account when considering a lumbosacral fusion in young male patients and a posterior approach may be preferable. Postoperative arterial obstruction has been described [8, 9, 11], especially in the elderly, but was not observed in our series. Such a complication may occur in cases of pre-existing vascular disease, and, in patients with increased risk, a vascular work-up should be per- formed before surgery as well as perioperative monitor- ing of lower limbs flow. A sympathectomy syndrome was observed in 3 cases after an L4-5 approach.
48.11
Critical Evaluation
48.11.1
Level of Approach
The approach can be performed for access to lumbar discs from L2 to S1. Disc surgery on L2-3 or L3-4 is in- frequently indicated. The skin incision is made above the umbilicus. Care must be taken of the peritoneum which is very thin and can be entered. The balloon in- sufflation makes the cleavage easier and peritoneal tears are unlikely to occur. When approaching the L2-3 disc, retraction of the peritoneum must be made cau- tiously to avoid damage to the spleen. For both levels, the anterior aspect of the disc is easy to palpate; the aor- ta must be medially retracted and it is necessary to di- vide at least one of the adjacent segmental vessels.
At the L4-5 level, the iliac vessels obliquely cross the
anterior aspect of the disc. They must be dissected and
retracted caudally and medially. Dissection must be
carried out carefully; the common iliac artery is the
first element to be identified along the medial border of the psoas muscle; the iliac vein is more deeply situated and is seen after retraction of the artery. It should also be gently dissected and retracted toward the midline. A complete exposure of the anterior aspect of the disc is possible but that requires an extensive dissection and retraction of the iliac vessels. Adhesions of the vein to the disc may be present, making the dissection more difficult. The L4 lumbar segmental vessels may be di- vided to facilitate the retraction of the iliac vessels. Dis- tal dissection of the iliac artery and vein must be per- formed as far as necessary to allow sufficient retraction of the vessels. The division of the iliolumbar vein is not usually necessary. The sympathetic chain lies more lat- erally on the anterolateral side of the disc, along the psoas muscle, and is normally not injured during the procedure.
The L4-5 anterior approach may be difficult in over- weight patients and a wider skin incision may be neces- sary. The fat is mainly present in subcutaneous tissues and as soon as the extraperitoneal space has been reached the procedure can usually be performed in the usual way without specific difficulties. Dissection and mobilization of the great vessels is even easier in fatter people. In very obese patients, rather than risk an iliac vein injury, it may be preferable to perform an antero- lateral approach by splitting the muscular fibers. This provides access to the anterolateral part of the L4-5 disc. After disinsertion and retraction of the anterior attachments of the psoas muscle, the anterolateral part of the disc is exposed and the self-retaining retractor can be inserted and secured to the adjacent vertebral bodies. It is then possible to perform a complete disc resection and vertebral plates decortication, working under the iliac vessels still protected by the remaining anterior longitudinal ligament and the superficial fi- bers of the annulus fibrosus. However, using this ap- proach often results in injury to the sympathetic chain with postoperative temperature difference in lower limbs, which does not always resolve.
The L5-S1 approach is made below the aortic bifur- cation; the iliac vessels are laterally situated and have to be only slightly retracted. Using a right-sided ap- proach, the oblique left common iliac vessels are usual- ly not seen; however, the dissection should not be per- formed too far to the left. A left-sided approach may be necessary, for instance in case of a combined L4-5 and L5-S1 approach; the left common iliac vein should be then dissected and laterally retracted. The anterior as- pect of the disc is always easily identified. Use of cauter- ization should be strictly avoided. The presacral net- work is not as mobile in the areolar retroperitoneal tis- sue as reported in the literature and it may be difficult to retract together with the peritoneum.
The L5-S1 disc may be deeply situated, especially when a spondylolisthesis is present; care must be taken
not to dissect right down into the sacral concavity, and the dissection must be carried on in an upward direc- tion corresponding to the direction of the disc.
48.11.2
Intervertebral Distraction
Intervertebral distraction is very effective for correc- tion of existing preoperative radicular pain, by increas- ing the foraminal volume [3]. The use of a large spread- er allows distraction even in stiff and collapsed discs. In our experience, anterior distraction has never induced neurologic complications, probably because the dis- traction is anteriorly applied, far from the neural canal.
Intervertebral distraction has the advantage of improv- ing the sagittal alignment of the lumbar and lumbosa- cral spine, thus protecting the adjacent non-fused lev- els.
48.11.3
Video Assistance
The operation can be performed without video assis- tance. Illumination of the surgical field is improved by the use of a headlight. The main advantage of video as- sistance is to provide a better illumination and to allow the assistants to see the procedure. By using a 30° angu- lated endoscope, a careful visualization of the vertebral plates is possible, thus controlling their decortication.
48.11.4
Disc Reconstruction
The large exposure provided on the anterior aspect of the disc allows the possibility of reconstruction using a ring cage filled with bone graft. We use a titanium cage screwed into the adjacent vertebral bodies. Screwing does not increase the stability in flexion, in torsion, or in lateral bending, but it does increase the stability in extension as far as 31 % [10]. An additional posterior fixation may be useful in cases of posterior instability (Fig. 48.6).
48.11.5
General Criticism
As the approach is being performed through the abdo-
men, knowledge of abdominal and vascular surgery
should have been acquired. As for any other anterior
approach to the lumbar spine, the most striking peri-
operative complication is vascular injury; bleeding
may occur during the exposure and is then easily iden-
tified; in some circumstances the insertion of the re-
tractor may collapse the injured vessel and bleeding
then will occur after the procedure has been completed,
when the retractor is removed. The surgeon should
a b
