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Mini-invasive
anterior approach to lumbo-sacral spine
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INTRODUCTION
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An increasing interest in the surgical approach to the lumbar spine is now occurring, due to the recent development of numerous and attractive techniques for the treatment of low back pain or lumbar instability. Approach can be either anterior or posterior. The anterior has advantage of giving direct access to the disc and allowing radical treatment of discogenic pain or disc instability. However, the anterior approach to the lumbar spine is still often considered as an aggressive procedure and therefore less frequently performed. The aim of this paper is to describe a technique of mini-invasive extraperitoneal anterior approach, less aggressive than the conventional anterior surgery, less sophisticated than the up-to-date laparoscopic techniques, and to discuss the results and complications observed from a series of 90 patients operated with this technique.
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MATERIALS
AND METHODS
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Approach
is made through an anterior extra-peritoneal dissection, right-sided
for the lumbo-sacral disc and left-sided for lumbar discs.11 The approach
is optimised by video- assistance.
1. Approach to L5-S1: The patient is in supine position.
Bending the table in lordosis after exposure of the disc will widen
the intervertebral space. The surgeon stands on the left side with one
assistant standing on the right side of the patient. A midline 4-5 cms
skin vertical incision is made half way between umbilicus and pubis
(Fig. 1a). In females a more cosmetic horizontal supra-pubic incision
is preferred (Fig. 1b). The incision must be exactly situated in the
direction of the disc to be fused, and a fluoroscopic control of the
disc level and orientation may be useful.
Then the anterior sheath of the right rectus abdominis is opened and
the muscle is pulled up together with the anterior sheath. Retraction
of the muscle is always possible and easy, as adhesions between the
muscle and its posterior sheath are never observed. Epigastric vessels
are pulled up together with the muscle. The approach is performed below
the linea arcuata and, as no posterior sheath is present (Fig. 2), the
dissection can be continued in the extraperitoneal fascia at the lateral
aspect of the muscle, with progressive cleavage of the peritoneum from
the lateral abdominal wall and the iliacus muscle. The dissection may
be facilitated by an inflatable balloon inserted in the lateral extraperitoneal
fascia. The progressive cleavage of the peritoneum provided by the balloon
insufflation can cause peritoneal tears, which could occur when dissection
is performed with nuts.
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A
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B
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| Figure
1 Post-operative aspect of the
skin incision after L5-S1 approach. a) vertical incision used in males
and b) horizontal supra-public incision used in females |
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A
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A
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B
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| Figure 2 Per-operative view of L5-S1 approach. Dissection is performed below the linea arcuata and the peritoneum is progressively cleaved from the lateral abdominal wall. 1: linea arcuata; 2: peri-toneum; 3: rectus abdominis muscle pulled-up | Figure 3 Per-operative view of L5-S1 approach. a) Lumbo-sacral disc has been exposed; left blade of the retractor has been secured to the adjacent vertebral bodies. Right common iliac artery is still visible b) after insertion of the right blade of the retractor the anterior aspect of the disc is completely exposed. 1: L5-S1 disc; 2: left valve of the retractor; 3: iliac artery; 4: right blade of the retractor |
The peritoneum is then medially retracted with a large retractor and the extraperitoneal cavity is progressively enlarged; the lateral and posterior peritoneum is more resistant than the anterior and tears are unlikely to occur. The ureter is adherent to the peritoneum and is retracted together with it. The endoscope may be inserted through a lateral port or through the anterior incision. It gives excellent illumination in the cavity, allowing the procedure to be continued under direct vision through the midline anterior incision.
The next step is to identify the psoas muscle and the iliac artery. The lateral iliac artery is usually first identified, then by backward dissection the iliac bifurcation is exposed and then the common iliac artery. The lumbo-sacral disc is medial to the common iliac artery and the dissection is carried on medial to the artery. The right iliac vein is covered by the artery and is not seen during the procedure, making preferable a right-sided approach. The left iliac vessels are usually not seen; however, the dissection should not be performed too far to the left. The lumbo-sacral disc is easy to identify by palpation as the first bulging structure above the sacral concavity, and its anterior aspect is exposed by blunt dissection. Cauterisation should be avoided. The approach is performed under the aortic bifurcation in avascular plane and bleeding is usually imperceptible. The only structures to divide are the middle sacral vessels. They should be hemoclipped and cut, giving a wide exposure to the disc. The fibrous and nervous structures constituting the pre-sacral network should be progressively dissected and retracted until the disc exposure is sufficient (Fig. 3). Again, cauterisation should be strictly prohibited because of the risk of damage of the hypogastric nerves supplying the bladder, eventually resulting in retrograde ejaculation. The L5-S1 disc may be deeply situated especially when a spondylolisthesis is present; the disc should be searched in an upward direction, and care must be taken not to dissect downward into the sacral concavity.
A specially designed self-retaining retractor is inserted through the midline incision and is held in place with Steinman pins secured in adjacent vertebral bodies (Fig. 4). The retractor gives a very good exposure to the anterior aspect of the disc and the procedure can be carried on with disc excision, vertebral plates decortication, and fusion with cages or graft.
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| Figure 4 The self-retaining retractor in place. Pins on the adjacent vertebrae have secured both left and right blades. An additional third blade allows retraction of the peritoneum | Figure 5 Aspect of the skin incision after L4-L5 approach. The incision is peri-umbilical |
2. Lumbar Discs Approach: The routine approach to lumbar discs is left sided, because the inferior vena cava is an obstacle on the right side. The surgeon stands on the right side of the patient. 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 operative table will be curved in lordosis after the disc exposure. The skin incision is centred on the umbilicus (Fig. 5); again a fluoroscopic control may be helpful to have a good orientation for dissection. The approach is performed above the linea arcuata and the posterior sheath is an obstacle at the lateral side of the rectus; it has to be divided in order to reach the extraperitoneal fascia. The inflatable balloon is introduced through a small hole made in the posterior sheath. The insufflation provides a complete cleavage of the peritoneum from the posterior sheath and from the lateral abdominal wall. After removal of the balloon, the posterior sheath can be divided and the extraperitoneal cavity can be progressively enlarged with medial retraction of the peritoneum. The psoas muscle is identified as a bulging structure; the dissection on the anterior aspect of the muscle becomes more superficial; dissection should not be carried on deeply between the iliacus and the psoas muscle. The common iliac artery is identified along the medial side of the psoas. The approach to the disc is lateral to the vessels and the artery must be gently dissected from the psoas and medially retracted. The common iliac artery is the first element to be identified (Fig. 6); the iliac vein is more deeply situated; it is seen after retraction of the artery and 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. The dissection may be difficult if adhesions of the vein to the disc are present, and in some cases it may be preferable to expose only the antero-lateral part of the disc in order to avoid any vessel injury. After insertion of the retractor in this antero-lateral situation, it is possible to perform a complete disc resection and vertebral plates decortication under the vessels still protected by the annulus fibrosus. The sympathetic chain lies more laterally along the psoas muscle on the antero-lateral side of the disc. The disc approach is medial and the sympathetic chain is usually not injured during the procedure. The L4 lumbar vessels may be divided to facilitate the retraction of the blood vessels. The division of the ilio-lumbar vein is not necessary.
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Approach to the L3-L4 disc
is easier as there are no crossing vessels; the dissection is easy
after division of the L3 lumbar vascular pedicle and a strict anterior
exposure is routinely possible. The approach to L2-L3 disc is possible,
although less frequently indicated. Care must be taken to avoid injury
to the spleen, which has to be medially retracted with the peritoneum.
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RESULTS
AND COMPLICATIONS
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We reviewed 90 patients who underwent a lumbar or lumbo-sacral fusion
by the anterior video-assisted approach previously described. There were
22 males and 68 females. Mean age at surgery was 42 (26-65). Level of
fusion was L2-L3: 5 patients; L3-L4: 4 patients; L4-L5: 36 patients; L5-S1:
45 patients, of whom 12 were males. A single level fusion was performed
in 88 cases; a double level fusion was performed in 2 cases (L4-L5 and
L5-S1).
The mean operative time was 90 minutes (60-130). The procedure was slightly
longer for L4-L5 approach (105 minutes). Average blood loss was 100 cc,
mainly due to the iliac graft donor site. The blood loss was imperceptible
and not measurable in 18 cases. Maximum blood loss was 400 cc. Post-operatively,
patient was allowed to stand up on the second post-operative day, wearing
a lumbo-sacral orthosis for 2 months. Mean hospital stay was 6 days.
Per-operative complications: Only vascular complications were observed:
five per-operative iliac vein injuries occurred during L4-L5 (3 cases)
and L5-S1 (2 cases) approach. In one case, a lumbar vein avulsion occurred
during the disc exposure. In 4 cases the operation was uneventful and
the bleeding occurred at the end of the procedure at removal of the retractor.
In all cases, bleeding was controlled by suture or hemoclip without enlarging
the approach. No per-operative peritoneal, gastrointestinal, neurologic
or urological complications were observed.
Post-operative complications: Two male patients presented with retrograde
ejaculation after an L5-S1 approach, which resolved in one case after
6 months. Sympathectomy syndrome was observed in 3 cases after the L4-L5
approach. Femoral thrombophlebitis was observed in two cases.
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DISCUSSION
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This surgical technique can be compared with the true laparoscopic approach,
which provides a direct access to the anterior aspect of the disc in a
natural cavity. However, the laparoscopic trans-peritoneal approach is
a demanding technique and special training is necessary. Visceral complications
may occur.9 With laparoscopic approach access to the lumbo-sacral disc
is easy, but access to the lumbar discs is difficult and not usually performed.15
This technique can also be compared to endoscopic or mini-invasive lateral
transmuscular approaches to the lumbar spine; these techniques give access
to the lateral part of the disc and not to the anterior part and they
involve some risk of denervation of the abdominal muscles. All endoscopic
techniques performed in virtual cavity, as both the peritoneal and extraperitoneal
cavities, require a gas insufflation in order to maintain wide open the
cavity.
The described technique is a mini-invasive conventional approach, performed
with insufflation, with ordinary instruments, and inducing no specific
extra cost. The approach can be performed through a wider incision, giving
the surgeon the possibility to progressively learn the technique and become
skilful with it. Previous abdominal surgery or bowel adhesions do not
make the procedure more difficult, and the post-operative course is easy
with early return to normal life. The advantages of video-assistance are
mainly to improve the lighting of the operative field and to allow the
assistants to see the operation. Lastly, the anterior approach allows
insertion of a unique large ring spacer in a midline situation. A large
spacer provides more stability and more contact between the graft and
vertebral plates then conventional twin cages (Fig. 7). The proximity
of the great vessels makes hazardous an additional fixation with a bulging
material and if osteosynthesis is indicated, low profile systems should
be used.
This technique is difficult in obese people. A wider skin incision is
necessary. The fat is mainly present in subcutaneous tissues and as soon
as the extraperitoneal space has been reached the procedure can be performed
in the usual way without specific difficulties. Dissection and mobilisation
of the iliac vessels is even easier in fat than in thin people. Complications
are rare. The overall incidence is about 10%, similar to the figures reported
after a conventional approach. Faciszewski reported a 11% incidence; Rajamaran
reported a 38% incidence after lumbar interbody fusion performed through
an extraperitoneal approach, but with many minor complications.3,13 Per-operative
injury to the great vessels is a well-known com-plication observed during
conventional anterior surgery: Kostuik reported a 2% incidence; Harmon
reported a 6% incidence; Baker reported a 15% incidence.1,5,8 These figures
are consistent with the 5% incidence observed in our review. Venous injury
is more frequent than an arterial injury. According to the literature,
most of the injuries are small tears, easily treated by a single clip
or stitch. Some investigators have found that venous repairs often result
in secondary thrombosis (25-50% of cases); however, we did not observe
this complication.6,12
Post-operative arterial obstruction has been described but was not observed
in our series.7,10
The more striking complication observed after anterior lumbo-sacral approach
is retrograde ejaculation. The reported incidence after conventional approach
is highly variable: one case out of 55 (2%) in Flynn series; 2 cases out
of 50 in Christensen series; 9 cases out of 40 (17%) in Tiusanen review;
2 cases out of 371 (0.5%) in Faciszewski review, but on multiple lumbar
levels; 3 cases out of 31 males (10%) for Rajamaran.2-4,13,14 We observed
2 cases out of 12 males, ie. a 16% incidence; all of them occurred at
L5-S1 level, although the dissection was very careful and without cauterisation.
The exact incidence of this complication is still controversial, as the
published series often do not separate the material by gender nor by the
operated levels. It should occur specifically after approach to the lumbo-sacral
disc because the dissection of the pre-sacral area may damage the sympathetic
fibres supplying the bladder. According to Tiusanen, this complication
should be more frequent after a transperitoneal approach.14 It is not
minimised by a keyhole approach and the risk should be seriously taken
into account when considering a lumbo-sacral fusion in young males.
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CONCLUSION
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Anterior video-assisted extraperitoneal approach to the lumbar spine
allows performing disc fusion with a low rate of complications. The incidence
of vascular and sexual complications is roughly similar to the incidence
reported after a conventional approach. The main advantages of a mini-invasive
keyhole approach is to decrease the number of general and gastrointestinal
complications, to reduce the hospital stay and to shorten the rehabilitation
time.
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REFERENCES
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| 1. | Baker JK, Reardon PR, Reardon MJ, Heggeness MH: Vascular injury in anterior lumbar surgery. Spine 1993, 18: 2227-2230 |
| 2. | Christensen FB, Bunger CE: Retrograde ejaculation after retroperitoneal lower lumbar interbody fusion: Int Orthop 1997, 21: 176-180 |
| 3. | Faciszewski T, Winter RB, Lonstein JE, Denis F, Johnson L: The surgical and medical perioperative complications of anterior spinal fusion surgery in the thoracic and lumbar spine in adults. Spine 1995, 20: 1592-1599 |
| 4. | Flynn JC, Price CT: Sexual complications of anterior fusion of the lumbar spine. Spine 1984, 9: 489-492 |
| 5. | Harmon PH: Anterior extraperitoneal lumbar disc excision and vertebral body fusion. Clin Orthop 1960, 18: 169-182 |
| 6. | Hobson RW, Yeager RA, Lynch TG, et al: Femoral venous trauma: techniques for surgical management and early results. Am J Surg 1960, 146: 220-224 |
| 7. | Khazim R, Boos N, Webb JK: Progressive thrombotic occlusion of the left common iliac artery after anterior lumbar interbody fusion. Eur Spine J 1998, 7: 239-241 |
| 8. | Kostuik JP: Anterior fixation for burst fractures of the thoracic and lumbar spine with or without neurologic involvement. Spine 1988, 8: 286-293 |
| 9. | McAfee PC, Regan JR, Zdeblick TA, et al: The incidence of complications in endoscopic anterior thoraco-lumbar reconstructive surgery. Spine 1995, 14: 1624-1632 |
| 10. | Marsicano J, Mirovsky Y, Remer S, Blom N, Neuwirth M: Thrombotic occlusion of the left common iliac artery after an anterior retroperitoneal approach to the lumbar spine. Spine 1994, 19: 357-359 |
| 11. | Onimus M, Papin P, Gangloff S: Extraperitoneal approach to the lumbar spine with video-assistance. Spine 1996, 2491-2494 |
| 12. | Pasch AR, Bishara RA, Schulert JJ, et al: Results of venous reconstruction after civilian vascular trauma. Arch Surg 1986, 121: 607-611 |
| 13. | Rajamaran V, Vingan R, Roth P, Heary RF, Conklin L, Jacobs GB: Visceral and vascular complications result-ing from anterior lumbar interbody fusion. J Neurosurg 1999, 91: 60-64 |
| 14. | Tiusanen H, Seitsalo S, Osterman K, Soini J: Retrograde ejaculation after anterior interbody fusion. Eur Spine J, 1995, 4: 339-342 |
| 15. | Zucherman JF, Zdeblick JA, Bailey SA, et al: Instrumented laparoscopic spinal fusion: preliminary results. Spine 1995, 18: 2029-2035 |
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