46 Microsurgical Anterior Lumbar Interbody Fusion
(Mini-ALIF): The Transperitoneal Approach to L5/S1
H.M. Mayer
46.1
Terminology
Mini-ALIF L5/S1 describes a microsurgical modifica- tion of a transperitoneal surgical approach to L5/S1 through a “mini-laparotomy” in the midline.
46.2
Surgical Principle
The L5/S1 disc space is reached through a midline surgi- cal approach. A 4-cm skin incision is performed after localization of the corridor line to the promontorium in the midline of the abdomen. A transperitoneal route to L5/S1 is created in the form of a mini-laparotomy through the linea alba of the rectus sheath. The small in- testines and the sigmoid colon are retracted from the promontorium with a special soft tissue retractor. The prevertebral peritoneum is split and dissected from the right to the left in front of the promontorium. The medi- an sacral vessels are ligated with vascular clips and dis- sected. Once the anterior circumference of L5/S1 inter- vertebral disc is exposed, interbody fusion with autoge- nous bone graft or cages is performed after removal of the disc. For retroperitoneal access, see Chapter 43.
46.3 History
The approach was described first by the author in 1997 [17].
46.4 Advantages
The general advantages are:
The transperitoneal surgical approach to the lum- bosacral junction is well known to spine surgeons.
There is no need to learn a completely new surgical technique.
The approach can be performed with the help of only one assistant (costs!).
No additional medicolegal problems as compared to conventional anterior approaches.
No additional potential complications with this technique (e.g., no gas in the abdomen).
Short learning curve, no laboratory training neces- sary.
No laparoscopic surgeon necessary.
The main technical advantages are:
Small skin incision (4 cm; cosmesis!).
Increased safety due to illumination and magnifi- cation of the surgical field by the use of optical aids (surgical microscope). The use of the microscope facilitates preparation in the prevertebral space.
The risk of postoperative intra-abdominal fibrosis is decreased, as is the risk of injury to the superior hypogastric plexus.
The type of interbody fusion is optional.
Low blood loss (< 100 cc).
Large and rapid exposure of the situs is possible in case of complications.
Low complication rate.
Good clinical results.
Shorter operating times even in learning curve.
46.5
Disadvantages
The main disadvantages are:
The surgeon should have microsurgical or video endoscopic experience.
Approach limited to L5/S1 (L5/L6).
Potential risk of trauma to vascular bifurcation and superior hypogastric plexus.
Additional posterior instrumentation (pedicle screw system or translaminar screw fixation) is recommended.
46.6 Indications
The approach has been used for anterior lumbar inter- body fusion in the following diseases (in the majority of my own cases combined with posterior instrumentation):
Degenerative instability (mainly with Modic type I changes in MRI)
Degenerative spondylolisthesis Isthmic spondylolisthesis Spinal stenosis with instability Failed Back Surgery syndrome Spondylitis/spondylodiscitis
Pseudoarthrosis following other types of fusion (e.g., posterolateral, PLIF)
46.7
Contraindications
The following situations should be considered as abso- lute contraindications to the microsurgical transperi- toneal approach:
Previous major abdominal or gynecological sur- gery through a transperitoneal route (e.g., hyster- ectomy, colon resection, etc.)
Low vascular bifurcation (in front of L5/S1) Spondylitis/spondylodiscitis with large preverte- bral soft tissue mass or psoas abscess
Previous transperitoneal anterior interbody fusion Relative contraindications are:
Previous minor abdominal surgery (e.g., append- ectomy, laparoscopic surgery)
Abdominal diseases (e.g., Crohn’s diseases, colitis ulcerosa, etc.)
Adipositas permagna
46.8
Patient’s Informed Consent
Besides information about general complications of spine surgery (deep venous thrombosis, pulmonary embolism, infection) the patient should be aware of the following potential complications and risks:
Injury to bowel, ureter, bladder with peritonitis, ur- osepsis, gastrointestinal and urogenital disturbances Injury to blood vessels (common iliac artery and vein, median sacral vessels)
Injury to superior hypogastric plexus with retro- grade ejaculation in men, sensory disturbance, ge- nital muscular function and lubrication in women
Intra-abdominal fibrosis with adhesions, ileus, or constrictions of ureter
46.9
Surgical Technique
46.9.1
Preoperative Planning and Anatomical Considerations Meticulous preoperative planning is paramount for the successful performance of a transperitoneal minimally invasive approach to L5/S1. Conventional X-rays of the lumbar spine give information on the anterior height of the intervertebral space L5/S1, on the sacral inclination as well as on the orientation of the intervertebral disc space plane (Fig. 46.1). The level of the bifurcation of the aorta and vena cava must be determined preopera- tively. This can be achieved in the majority of the pa- tients with a conventional MRI (Fig. 46.2a). Three-di- mensional color-coded CT angiography can be helpful in uncertain cases (Fig. 46.2b). The prevertebral space at the level of the lumbosacral junction must be evalu- ated very carefully on MRI and, in particular, the course of the common iliac artery and vein on both sides must be determined. In addition, MRI gives infor- mation on the thickness of the retroperitoneal fat pad in front of the L5/S1 disc space.
When previous abdominal operations have been performed, the indication for a minimally invasive transperitoneal approach must be evaluated individu- ally. It is possible to start with a microsurgical ap- proach. In case of larger intra-abdominal scar tissue or fibrous bands, it is possible to enlarge the approach;
however, when starting with this new surgical tech- nique, I recommend beginning with a longer skin inci- sion in previously operated cases.
The L5/S1 interspace is reached through a mini-lap- arotomy in the midline. Since the surgeon stands be-
Fig. 46.1. X-ray of the lumbar spine in supine position. Note the orientation of the L5/S1 disc space
a
b Fig. 46.2. a MRI axial view of the lumbosacral junction at the level of the L5/S1 disc. Note the common iliac artery and veins on both sides. b Three-dimensional color-coded CT angiogra- phy of the prevertebral area L4-S1
tween the abducted legs of the patient, abduction of the hip joints should be determined preoperatively. The patients are treated with routine mechanical large bow- el preparations as well as purgatives starting 24 hours before the operation.
46.9.2 Anesthesia
A complete relaxation of the patient is mandatory in or- der to be able to manipulate the small intestine as well as the sigmoid colon intraoperatively. This is para- mount for the exposure of the parietal peritoneum in front of the promontory. Anesthesia is performed in the same manner as described for the retroperitoneal approach.
Fig. 46.3. Positioning of the patient for transperitoneal anterior approach to L5/S1
46.9.3 Positioning
The patients is placed in a supine Trendelenburg posi- tion (trunk tilted 20 – 30°) with the lumbar spine hyper- extended and legs in maximum abduction (Fig. 46.3).
The position of the surgeon is between the legs of the patient. He is thus working straight forward with his vi- sual axis in parallel to the orientation of the L5/S1 disc space. The assistant stands at the left side of the patient and the scrub nurse obliquely behind the surgeon on his right side. The microscope is positioned on the pa- tient’s right side.
46.9.4 Localization
In obese patients the following method of localization is recommended. The orientation of the L5/S1 disc space is marked as it projects onto the skin in a lateral fluoroscopic view (“disc line”; Fig. 46.4a, b). The anteri- or border (tangent) of the promontorium is also marked on the skin (“border line”). The intersection of both lines is usually located on the lateral part of the patients buttock cranial to the major trochanter. A transverse line is drawn from this intersection point onto the abdomen (“corridor line”; Fig. 46.5a). This corridor line is located in the middle third of the dis- tance between umbilicus and symphysis. A 4-cm skin incision is centered over this line strictly in the midline (“incision line”). Either a longitudinal (Fig. 46.5b) or a transverse skin incision can be chosen (Fig. 46.5c). In slim patients, the skin incision can be determined by indenting the abdominal wall with a blunt metal mark- er centered over the disc space L5-S1. On lateral fluo- roscopy, the marker as well as the “entrance” of L5/S1
a
b
Fig. 46.4. a Lateral fluoroscopy for localization of L5/S1 (red line anterior border of L5/S1 interspace, yellow line orientation of disc space). b Disc line giving the orientation of the disc space
a
b
c
Fig. 46.5. a Corridor line drawn onto the abdomen. b Longitu- dinal skin incision marked in the midline. c Transverse skin in- cision
d
Fig. 46.5. (cont.) d L5/S1 lateral fluoroscopy. Note the metal marker above the “entrance” of L5/S1
can be identified. The skin incision is place above this entrance (Fig. 46.5d).
46.9.5 Surgical Steps 46.9.5.1
Skin to Intraperitoneal Cavity
A 4-cm skin incision is placed in the midline centered over the “corridor line.” The skin incision can be placed transversely or longitudinally. The fascia of the rectus abdominis muscle is exposed and the linea alba which
Fig. 46.6. Splitting of the rectus abdominis fascia in the midline (linea alba)
marks the midline is identified. The rectus fascia is opened along the linea alba and the rectus abdominis is then visible on both sides. Sometimes there are adhe- sions between the ligamentum urachi and the preperi- toneal fat pad which have to be dissected sharply (Fig. 46.6). A soft tissue spreader with blunt blades is inserted to retract both rectus muscles from the mid- line. This leads to exposure of the peritoneum (Fig. 46.7). The fat pad in front of the peritoneum is mobilized from lateral to medial in order to expose the peritoneum and to facilitate laparotomy. The peritone- um is opened and armed with four sutures placed at the cranial and caudal edges (Fig. 46.8). The mesenterium with the ileum is carefully pushed into the upper left abdominal cavity using the Langenbeck hooks for blunt dissection and small abdominal towels to hold the abdominal contents in place. The same is done to
Fig. 46.7. Exposure of the peritoneum
Fig. 46.8. Peritoneum is opened and armed with sutures. The greater omentum is exposed
a b
c
Fig. 46.9. a Mobilization and retraction of the bowel with small abdominal towels. b Soft tissue retractor before insertion.
c Soft tissue retractor after insertion
the sigmoid colon which is carefully retracted to the left (Fig. 46.9a). A soft tissue retractor with blunt blades is inserted in order to retract the bowel to the right and to the left after identification of the common iliac artery and the retroperitoneal course of the ureter on the right side (Fig. 46.9b). Thus, the promontorium is exposed (Fig. 46.10)
Fig. 46.10. Exposure of the promontorium by the soft tissue re- tractor
46.9.5.2
Retroperitoneal Space to Intervertebral Region
The retractor is now completed with two other blades.
One is positioned between the bifurcation in front of the lower anterior part of the L5 vertebral body, and the other one is centered in the presacral space (Fig. 46.9c).
Now, the corridor to the anterior circumference of L5/
S1 is free. Ideally, the visual axis of the surgeon is paral- lel to the orientation of the L5/S1 intervertebral space (Fig. 46.11).
Fig. 46.11. Visual axis of the surgeon is parallel to the L5/S1 in- tervertebral space
The peritoneum in front of the promontorium is in- cised with microscissors. The incision is made about 15 mm medial to the right common iliac artery and completed in a semicircular manner. The reason for this is the fact that the main branches of the superior hypogastric plexus are usually located in the medial and left aspect of the prevertebral space at L5/S1. On the right lateral side, you can only find very small fibers of the plexus which can be identified easily under the surgical microscope. Dissection is performed bluntly and the prevertebral fat tissue including the superior hypogastric plexus is gently pushed away from the disc circumference from the right to the left using cottonoid pads (Fig. 46.12). Only bipolar coagulation is allowed.
Thus, the anterior circumference of L5/S1 as well as the median sacral vessels (a.v. sacralis mediana) are ex- posed (Fig. 46.13a). The vessels are closed with vascu- lar clips, dissected, and retracted from the disc surface (Fig. 46.13b).
a b
Fig. 46.13. a Exposure of anterior circumference of L5/S1 disc as well as of median sacral vessels. b Ligation of vessels with vascular clips and dissection
Fig. 46.12. Opening of the prevertebral peritoneum on the right side for blunt dissection (from the right to the left side) of pre- vertebral fat tissue including the superior hypogastric plexus
The retractor blades can now be readjusted underneath the peritoneum in order to retract the peritoneum and the prevertebral tissues from the surgical field.
46.9.5.3 Interbody Fusion
Anterior lumbar interbody fusion with an autologous iliac bone graft is described here. However, there are
various other options for the type of interbody fusion (see also Chapter 51).
46.9.5.4
Discectomy and Preparation of Graft Bed
The anterior longitudinal ligament and the anulus fi- brosis are incised in a rectangular shape (Fig. 46.14).
The disc space is cleaned and the endplates are careful- ly removed with curettes. If the subchondral bone shows advanced sclerosis, I recommend to resect the endplate with chisels and a high-speed burr (Fig.
46.15). If necessary, the endplates can be removed as far posterior as possible until the posterior longitudinal ligament is exposed. Thus, decompression of the ante- rior part of the spinal canal at L5/S1 can also be per-
Fig. 46.14. Removal of the L5/S1 disc with a rongeur
Fig. 46.15. Graft bed is prepared at L5/S1. The caudal endplate of L5 as well as the endplate of the sacrum are clearly visible
formed. The height and depth of the iliac crest graft needed is measured with a sliding caliper.
46.9.5.5 Graft Harvesting
A tricortical iliac bone graft is harvested as described in Chapter 45.
46.9.5.6 Grafting
The graft is prepared and inserted the same way as has been described for the retroperitoneal approach. How- ever, the orientation of the graft is strictly in the mid- line in parallel to the sagittal plane (Fig. 46.16a). Addi- tional cancellous bone from the iliac crest as well as from the removed parts of the vertebral bodies is im- pacted into the intervertebral space on both sides of the graft (Fig. 46.16b). The fusion area is covered with Sur- gicell.
46.9.5.7 Retreat
The peritoneum in front of L5/S1 as well as the perito- neum viscerale are closed with absorbable running su- tures after removal of the abdominal towels. The rectus sheath is readapted with absorbable single sutures. The skin is closed with an intracutaneous suture.
46.10
Postoperative Care
The postoperative treatment is identical to the retro- peritoneal approach. The patient is allowed to eat nor- mally after 24 hours and is mobilized the day after the operation.
46.11
Complications, Pitfalls, and Hazards
There are some specific potential complications and hazards, due to the microsurgical technique as well as due to the instruments, which should must be men- tioned:
The first pitfalls might be wrong positioning of the patient and inadequate localization of the corridor line. If the patient does not have a Trendelenburg positioning the angle between the L5/S1 interspace and the surgeon’s visual axis increases and might make it impossible to have a good insight into the disc space.
a b
Fig. 46.16. a Tricortical bone graft is impacted at L5/S1 in the midline. b Gaps on both sides of the graft as well as the space anterior to the graft are filled with cancellous bone
Exact localization of the corridor line is paramount since mobility of the skin of the patient is limited once the surgeon’s approach is too far cranial or caudal.
Retraction of the abdominal contents becomes extremely difficult if the bowel is not empty and relaxed. So preoperative bowel preparation is one of the keys to a successful operation.
Microsurgical dissection in front of the peritoneum is safe; however, it should be performed bluntly with small swabs, and the use of bipolar coagula- tion must be restricted to a minimum.
Dissection in the retroperitoneal space in front of the promontorium must start from the right side in order to decrease the risk of injury to the superior hypogastric plexus.
The opening of the retractor in the retroperitoneal space must be performed very gently in order to avoid overdistraction of the venous bifurcation. If there is an overlap of the medial aspect of the left common ili- ac vein with the L5/S1 disc space, the vein should be retracted gently by the assistant (Fig. 46.17).
Sometimes there is bleeding from intraosseous veins of the sacrum which might occur after resec- tion of the endplate. This can be controlled with bone wax which is distributed on the bony surfaces with the high-speed diamond burr.
In our series we had a total of 8/51 complications (15.7 %; Table 46.1). However, there was only 1/51
Fig. 46.17. Overlap of left common iliac vein (l.c.i.v.) with the L5/S1 disc space. b Bone graft
Table 46.1. Complications following 360° Fusion with trans- peritoneal Mini-ALIF
Complication Number of patients affected
Ileus 1
Fracture of os ilium 1 Loosening of implant 1 Fracture of pedicle 1 Hematoma donor site 2 Laryngeal irritation 1 Superficial infection 1
Total 8 (15.7%)
(1.96 %) specific complication. A 15-year-old boy with an isthmic type spondylolisthesis suffered from an ile- us on the 5th postoperative day after microsurgical an-
0 0
11
89
0 20 40 60 80 100 [%]
excellent good moderate bad EFR score
(Prolo 1986)
patients
2 9
6 5
6
0 0
2 0 4 0 6 0 8 0 1 0 0 [%]
excellent good moderate bad EFR score (Prolo 1986)
patients
9 5 , 4
4 , 6
0 , 0 0 , 0
0 2 0 4 0 6 0 8 0 1 0 0 [%]
completely better unchanged not
satisfied satisfied
patients
terior interbody fusion at L5/S1. However, this boy had Crohn’s disease which might have contributed to this postoperative complication. All other complications were either due to the posterior instrumentation (loos- ening of implant n = 1; fracture of the pedicle during insertion of pedicle screw n = 1) or due to the harvest- ing of the bone graft (fracture of the ileum n = 1; hema- toma at the donor site n = 2; superficial wound infec- tion at the donor site n = 1). There was one patient with a postoperative laryngeal irritation due to intubation.
46.12 Results
Microsurgical transperitoneal anterior lumbar inter- body fusion has been performed in 51 patients (27 women, 24 men; age range 10 – 68 years (average 44.1 years). All the procedures were performed as part of a 270°-fusion philosophy which includes posterior instrumentation (with/without decompression of the spinal canal) with pedicle screw systems or translami- nar screws, and arthrodesis of the facet joints (except for isthmic type of spondylolisthesis) combined with anterior lumbar interbody fusion. The indications are listed in Table 46.2.
The average time for surgery was 122.5 minutes.
Time for surgery ranged between 65 and 205 minutes.
The average blood loss was 78.9 cc at the fusion site and 77.5 cc at the donor site for the bone graft. None of the
Table 46.2. Indications for transperitoneal microsurgical ante- rior lumbar interbody fusion. Mini-ALIF was part of a 270°-fu- sion concept
Indication Number treated
Degenerative spondylolisthesis 4 Isthmic spondylolisthesis 24 Degenerative instability 10
Failed backs 10
Spondylitis 3
Total 51
a b
Fig. 46.18. a Preoperative EFR score [21]. b Postoperative EFR [21]
patients received any blood transfusion for the anterior approach.
Preoperative evaluation of the economic and func- tional status of the patients was performed with the help of the EFR score published by Prolo in 1986 [21]. Forty- five of the patients (89 %) had a bad score preoperatively (Fig. 46.18a). After an average follow up period of 20 months, 94 % of the patients showed excellent or good clinical results, 6 % showed satisfactory results, and none of the patients had a bad results (Fig. 46.18b).
The patients were asked to give a self-rating of the result of surgery. All the patients were completely satisfied with the operation (Fig. 46.19). Radiological reevalua- tion showed a fusion rate of 99.6 % among those patients with a follow up of more than 6 months (Fig. 46.20).
46.13
Critical Evaluation
The transperitoneal approach which has been de- scribed in this chapter represents a microsurgical mod- ification of the well-known transabdominal approach to L5/S1. This route to L5/S1 follows the shortest ana- tomical way from the skin surface to the L5/S1 interver- tebral disc. It is the most direct approach to L5/S1 which can also be recommended in obese patients.
Fig. 46.19. Patient’s self-evaluation of the clinical results
Fig. 46.20. Solid interbody fusion at L5/S1 after posterior in- strumentation and microsurgical transperitoneal anterior bone grafting
Crossing the abdominal cavity bears certain risks for the anatomical structures which are located on the way to the promontorium. The bowels must be handled very gently by only using blunt instruments and hooks for preparation. The abdominal towels which are gently inserted into the abdominal cavity help to retract the bowel from the promontorium. We have not had any injury to the bowel so far. The bladder of the patients must be catheterized during the operation to decrease the risk to the bladder during dissection of the perito- neum.
In patient’s with a history of abdominal surgery (see Section 46.7), mobilization of the bowel must be per- formed very cautiously. Since only the small surgical corridor is visible through the microscope, there is a potential risk for indirect damage to the bowel due to forceful retraction. Since this damage might occur be- yond the visual field of the surgeon’s eye, it might re- main undetected during surgery. The same is true for indirect injury to the venous bifurcation. Although the amount of lateral retraction is limited by the skin inci- sion and the tension of the rectus abdominis muscle, the venous bifurcation is at risk. If the common iliac ar- tery covers part of the anterior circumference of the disc space, I recommend not to insert the retractor blades underneath the peritoneum. The assistant
should carefully retract the vein during preparation of the graft bed.
Injury to the superior hypogastric plexus can be avoided if dissection in the retroperitoneal preverte- bral space is performed as described above. Up to now, there have been no postoperative sexual complications.
Moreover, the risk of producing postoperative fibrosis in the abdominal cavity is diminished due to meticu- lous microsurgical preparation. If the technique is per- formed the way it is described, it represents a safe and most direct way for anterior interbody fusion of the lumbosacral junction.
Bibliography
1. Bohlman HH, Eismont FJ (1981) Surgical techniques of anterior decompression and fusion for spinal cord inju- ries. Clin Orthop 154:57 – 67
2. Capener N (1932) Spondylolisthesis. Br J Surg 19:374 – 386 3. Crock HV (1982) Anterior lumbar interbody fusion. Clin
Orthop 165:157 – 163
4. Faciszewski T, Winter RB, Lonstein JE, Denis F, Johnson L (1995) The surgical and medical perioperative complica- tions of anterior spinal fusion surgery in the thoracic and lumbar spine in adults. Spine 20: 1592 – 1599
5. Fujimaki A, Crock HV, Bedbrook GM (1982) The result of 150 anterior lumbar interbody fusion operations per- formed by two surgeons in Australia. Clin Orthop 165:
164 – 167
6. Gertzbein SD, Court-Brown CM, Jacobs RR, et al (1988) Decompression and circumferential stabilization of unsta- ble spinal fractures. Spine 13:892 – 895
7. Greenough CG, Taylor LJ, Fraser RD (1994) Anterior lum- bar fusion. A comparison of noncompensation patients with compensation patients. Clin Orthop 300:30 – 37 8. Greenough CG, Taylor LJ, Fraser RD (1994) Anterior lum-
bar fusion: results, assessment techniques and prognostic factors. Eur Spine J 3:225 – 230
9. Grob D, Scheier HJG, Dvorak J, Siegrist H, Rubeli M, Joller R (1991) Circumferential fusion of the lumbar and lumbo- sacral spine. Arch Orthop Trauma Surg 111:20 – 25 10. Harmon PH (1963) Anterior excision and vertebral body
fusion operation for intervertebral disc syndromes of the lower lumbar spine. Clin Orthop 25:107 – 127
11. Kostuik JP (1979) Decision making in adult scoliosis. Spine 4:520 – 525
12. Kozak JA, O’Brien JP (1990) Simultaneous combined ante- rior and posterior fusion. An independent analysis of a treatment for the disabled low-back pain patient. Spine 15:322 – 328
13. Kozak JA, Heilman AE, O’Brien JP (1994) Anterior lumbar fusion options. Clin Orthop 300:45 – 51
14. Leong JCY, Hoper G, Fang D, Chun SY (1982) Disc excision and anterior spinal fusion for lumbar disc protrusion in the adolescent. Spine 7:623 – 626
15. Louw JA (1990) Spinal tuberculosis with neurological defi- cit. J Bone Joint Surg Br 72:686 – 693
16. Mathews HH, Evans MT, Molligan HJ, Long BH (1995) Laparoscopic discectomy with anterior lumbar interbody fusion. Spine 20:1797 – 1802
17. Mayer HM (1997) A new microsurgical technique for mini- mally invasive anterior lumbar interbody fusion. Spine 22:691 – 700
18. McAffee PC, Regan JR, Zdeblick T, et al. (1995) The inci- dence of complications in endoscopic anterior thoraco- lumbar spinal reconstructive surgery. Spine 20:1623 – 1632
19. Obenchain TG (1991) Laparoscopic lumbar discectomy. J Laparoendosc Surg 3:145 – 149
20. O’Brien JP, Dawson MHO, Heard CW, Momberger G, Wea- therley CR (1986) Simultaneous combined anterior and posterior fusion. A surgical solution for failed spinal sur- gery with a brief review of the first 150 patients. Clin Or- thop 203:191 – 195
21. Prolo DJ, Oklund SA, Butcher M (1986) Toward uniformity in evaluating results of lumbar spine operations. Spine 11:601 – 606
22. Sorenson KH (1978) Anterior interbody lumbar spine fu- sion for incapacitating disc degeneration and spondylolis- thesis. Acta Ortho Scand 49:267 – 277
23. Spivak JM, Neuwirth MG, Giordano CP, Bloom N (1994) The perioperative course of combined anterior and poste- rior spinal fusion. Spine 19:520 – 525
24. Stauffer RN, Coventry MB (1972) Anterior interbody lum- bar spine fusion. J Bone Joint Surg Am 54:756 – 768 25. Takahashi K, Kitahara H, Yamagata M, et al (1990) Long-
term results of anterior interbody fusion for treatment of degenerative spondylolisthesis. Spine 15:1201 – 1215 26. Zucherman JF, Zdeblick TA, Bailey SA, Mahvi D, Hsu KY,
Kohrs D (1995) Instrumented laparoscopic spinal fusion.
Spine 20:2029 – 2035
