by S JESWANI · Cited by 1 — Anterior approaches to the spine have been used to treat lumbar degenerative disc disease for 70 years. The earli- est reports of anterior spine surgery

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1955HistoryAnterior approaches to the spine have been used to treat lumbar degenerative disc disease for 70 years. The earli -est reports of anterior spine surgery arise from the late 19th century. Tuberculosis of the spine was a signiÞcant problem, which often led to paraplegia. Vincent of Paris, in 1892, evacuated a tuberculosis abscess using costotrans -versectomy. 1 Three years later, the other pioneer of anterior spine surgery, Victor Menard, authenticated the beneÞts of the anterior approach by performing a posterolateral costo -transversectomy for abscess drainage. 2 The Þrst attempted anterior approach to the lumbar spine was in 1906 by Muller, wherein he used a transperitoneal approach to debride tuberculosis of the lumbar spine. 3 Postoperatively, his patient did well; however, subsequent patients had signiÞcant morbidities and mortalities, which slowed the progression of the approach. Almost 15 years later, in 1921, Royle used a retroperitoneal approach to remove a con -genital hemivertebra in the lumbar spine. 4 The next year, MacLennon was the Þrst to treat scoliosis in children with an anterior retroperitoneal approach. 5During the 1930s, Chaklin performed an anterior ret -roperitoneal osteotomy of the lumbar spine, while Burns, whom many credit to be the Þrst to perform an anterior fusion of the lumbar spine, used bone grafting to treat lum -bar spondylolisthesis via a transperitoneal approach. 6,7 Ito et al. used both an anterior costotransversectomy approach to the thoracic spine to treat PottÕs disease and a retroperitoneal approach to the lumbar spine to perform structural bone grafting. 8 In 1944, Iwahara treated lumbar degenerative disease by an interbody fusion done using a retroperitoneal approach. 9 Four years later, Lane and Moore used a transperitoneal approach to treat lumbar degenerative disease. 10 In 1945, Capener described a trans -peritoneal approach using a tibial allograft graft; in 1959, he modiÞed this approach by removing an additional rib laterally. 11 In 1956 and then in 1960, Hodgson and Stock, who were able to successfully eradicate the disease in hundreds of tuberculosis patients, extended the anterior approach to the thoracic and lumbar spine for debride -ment of tuberculosis abscesses with subsequent interbody fusion. 12 Acceptance of the anterior interbody fusion tech -nique as an efÞcacious procedure has evolved as one of the predominant techniques to treat discogenic back pain. Advantages The anterior approach to the lumbar spine has been shown to have several advantages over posterior approaches. The anterior approach provides direct access to the ventral sur -face of the vertebral bodies and disc spaces, and it provides a direct and more complete view of the anterior surface of the lumbar spine from L3 to S1. 13 In addition, the anterior approach avoids dissection through the soft tissue and musculature encountered in the posterior approach, espe -cially the paraspinal muscles. Avoidance of injury to these tissues may result in signiÞcantly decreased postoperative pain and subsequently decreased length of postoperative hospital stay. 13,14 Lumbar interbody fusion via the anterior approach has also shown to be advantageous over posterior tech -niques, such as posterior lumbar interbody fusion (PLIF). One signiÞcant advantage is the absence of neural retrac -tion required in the anterior approach, as compared to the degree of retraction required on the neural structures in the PLIF technique. 15 One recent study compared the anterior lumbar interbody fusion (ALIF) technique to the transfo -raminal lumbar interbody fusion technique and shows an increased ability of ALIF to improve foraminal height, local disc angle, and lumbar lordosis. 16 Other studies have dem -onstrated decreased rate of adjacent segment degeneration with ALIF compared to PLIF. 17IndicationsThe indications for ALIF have increased over the last sev -eral years. The most common indication for ALIF is dis -cogenic back pain that occurs between the levels of L3 to S1. 13,18 Another common indication for this procedure is spondylolisthesis, namely, the isthmic and degenera -tive types. 19,20 ALIF has also been used as revision surgery after a failed posterior fusion involving segments from L3 to S1. 13,21 A secondary indication for anterior fusion is interver -tebral foraminal stenosis secondary to loss of disc height, 22 in conjunction with the need for interbody fusion. ContraindicationsSeveral contraindications exist to the ALIF technique. Severe and numerous medical comorbidities pose a relative CHAPTER 171Anterior Lumbar Interbody Fusion: Indications and TechniquesSUNIL JESWANI ¥ DONIEL DRAZIN ¥ JOHN C. LIU ¥ CHRISTOPHER AMES ¥ FRANK L. ACOSTA

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1956Section Nine ¥ NEUROSURGICAL MANAGEMENT OF SPINAL DISORDERS complication to any major surgical procedure. In addi -tion, severe obesity is a contraindication to the anterior approach, given the hindrance the obesity would have dur -ing exposure and retraction of intra-abdominal tissues and structures. Disease processes and abnormalities of intra-abdominal structures have a signiÞcant inßuence on the risk associ -ated with the anterior approach to the lumbar spine. For instance, signiÞcant retroperitoneal scarring due to pre -vious surgery, injury, or infection could severely limit the exposure and therefore increase the risk for injury to the intra-abdominal and retroperitoneal structures during the exposure. The presence of an abdominal aortic aneurysm would also be a contraindication to the anterior approach to the lumbar spine, since a signiÞcant amount of retraction is placed on the major vessels. Moreover, severe peripheral vascular disease would be considered a contraindication to this approach due to the potential compromise of already- diseased vasculature. Finally, a solitary kidney on the side of the exposure poses as a risk associated with the anterior approach, since there is a nonzero risk of injury to the ureter. Contraindications to the ALIF technique exist that are related to the state of the bone and fusion. Spinal infec -tion is a contraindication to interbody fusion, given that a foreign body is being place into infected tissue. Severe osteoporosis is also considered a contraindication. An area of question is the contraindication of stand-alone anterior interbody fusions in potentially unstable segments of the spine. For instance, it is considered that ALIF to treat high- grade spondylolisthesis should require posterior stabiliza -tion and fusion. Preoperative Evaluation The preoperative evaluation of patients who will undergo ALIF Þrst requires careful selection of those patients likely to have a successful outcome after an anterior fusion. For example, in patients with discogenic pain, the following criteria have been shown to be associated with a good out -come after ALIF 13: (1) axial back pain aggravated by spi -nal loading and fusion, (2) radiographic studies consistent with disc degeneration, (3) provocative discography that produces pain only at the affected levels, and (4) dynamic studies demonstrating motion/sagittal deformity on sagittal views. Careful consideration also needs to be placed on the type of approach used to access the anterior spine. This depends on the patientÕs characteristics, as well as the surgeonÕs pref -erence. ALIF has three major types of approaches: open, mini-open, and laparoscopic. Each approach has advan -tages and disadvantages. Open ALIF requires a larger inci -sion and opening into the retroperitoneal space. However, the drawbacks of this approach include increased blood loss during surgery, as well as increased operative time, compared to other approaches. 23On the other end of the spectrum, the laparoscopic approach to the anterior spine minimizes the size of the incision and dissection into the retroperitoneal space. This technique has been gaining popularity for some time. How -ever, the signiÞcant drawback with this approach is the decreased visibility intraoperatively, leading to inadvertent injury to nearby critical structures. Mini-open anterior lumbar interbody and fusion has gained a great amount of popularity over time and has been the favored technique for approaching the anterior spine for many surgeons. This approach seems to be an optimization between the laparoscopic technique and the open tech -nique in that the incision and dissection are minimized yet visibility is signiÞcantly improved compared to that of the laparoscopic approach. This technique is detailed further in the later sections. Next, the surgeon has to decide whether to approach the anterior spine via a transperitoneal or an extraperitoneal approach. The retroperitoneal approach seems to be the favored approach, given the complications that seem to be associated with the transperitoneal approach. The trans -peritoneal approach has been shown to have an increased of retrograde ejaculation compared to the retroperitoneal approach by approximately a factor of 10, 23,24 secondary to an increased rate of injury to the hypogastric plexus. 25 In addition, the number of levels than can be accessed with the transperitoneal approach is typically decreased. Finally, the transperitoneal approach requires direct manipulation of intra-abdominal contents, including visceral structures. This may lead to an increased rate of postoperative ileus, as well as an increased rate of injury to the intraperitoneal structures. Careful preoperative assessment must also be made in regard to whether ALIF should also be supplemented with additional posterior fusion. The addition of posterior fusion introduces a second step to the surgery. Since it requires dissection of posterior soft tissues, it counteracts the advantage that anterior lumbar approaches have in avoiding dissection of paraspinal musculature. However, biomechanical studies have shown a signiÞcant decrease in the relative motion between segments and a decrease in bone stress level, resulting in higher rates of fusion. 26 In cases of isthmic spondylolisthesis, the addition of poste -rior fusion should strongly be considered, given the inher -ent instability and motion with isthmic spondylolisthesis. In addition, standalone anterior interbody fusion has been associated with increased incidence of sacral fractures over time. 19 Finally, in cases requiring multilevel fusion, posterior Þxation and fusion should be considered. 15Preoperative imaging should carefully be assessed prior to surgery. Plain radiographs are used to estimate the size and angle of the implant to be used in an effort to achieve optimal postoperative disc height and lordosis. The degree of sagittal imbalance should also be assessed on preopera -tive imaging, which should be restored. 21 One study demon -strated that correction of sagittal imbalance, local lumbar lordosis, disc height, and neural foramen led to better over -all long-term outcomes. 16Operative Technique The operative technique for the mini-open ALIF via a retro -peritoneal approach is described in this section. The positioning of the patient for an ALIF is usually supine on the operating table. In some cases, the lateral position can be used. A break in the operating room table or an inßatable bladder needs to be placed under the lumbar area of the patient at the level of the affected disc to control the amount of lordosis at the level to be operated upon. 13,21

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1957171 ¥ Anterior Lumbar Interbody Fusion: Indications and Techniques The exposure of the anterior spine via a mini-open approach requires good knowledge of the surgical anatomy of the layers of the abdominal wall, as well as the retroperi -toneal space. Failure to recognize the individual layers of the anterior abdominal wall may lead to accidental perfora -tion through the peritoneal lining. Moreover, lack of knowl -edge of retroperitoneal structures and their relationship to one another in space may lead to signiÞcant injury of these structures during exposure or during retraction. Typically, a vertical skin incision is made on the abdo -men to the left of the midline ( Fig. 171-1 ). However, hori -zontal skin incisions have been used. The incision is made over the appropriate disc space to be fused. Blunt dissec -tion is then carried out through the subcutaneous tissues until the anterior rectus sheath is exposed ( Fig. 171-2 ). A vertical incision is then made through the anterior rectus sheath, exposing the rectus muscle. The rectus muscle is then mobilized and retracted medially to expose the poste -rior rectus sheath ( Fig. 171-3 ). The exposure of the posterior rectus sheath must include visualization of the arcuate line. Blunt dissection is then carried out underneath the arcu -ate ligament between the posterior rectus sheath and the peritoneum ( Fig. 171-4 ). Using blunt dissection, this space is developed until the retroperitoneal space is accessed. Once the accession to the retroperitoneal space has been veri -Þed, the peritoneal contents are then swept medially to pro -vide direct visualization of the retroperitoneal space ( Fig. 171-5 ). The ureter sits on the underside of the peritoneum and is retracted away with the peritoneum. At this point, the FIGURE 171-1 Vertical paramedian skin incision.Anterior rectussheathFIGURE 171-2 Exposure of the anterior rectus sheath.

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1958Section Nine ¥ NEUROSURGICAL MANAGEMENT OF SPINAL DISORDERS vascular structures and ureter is carefully identiÞed to mini -mize injury to these structures. Deep abdominal retractors can then be placed. Vascular dissection and retraction then must be car -ried out to access the ventral surface of the lumbar spine. Knowledge of the vascular anatomy in this area is critical, and there can be a signiÞcant amount of variability in the relationship between the bifurcations of the aorta and vena cava and the disc space ( Fig. 171-6 ). If accessing the L3-4 or the L4-5 disc space, then the aorta and vena cava have to be retracted away to visualize the anterior surface of the vertebral bodies. However, if the L5-S1 disc space is to be accessed, the space below the bifurcations of the aorta and vena cava can be accessed. In this case, the middle sacral artery and vein may have to be ligated. Segmental vessels may have to be ligated to maximize the operative Þeld, as well as to prevent bleeding during the case. The iliolumbar vein is also identiÞed and ligated to prevent unnecessary bleeding during the case ( Fig. 171-7 ). The major vessels are retracted away carefully using blunt dissection to expose the anterior spine ( Fig. 171-8 ).At this point, the anterior longitudinal ligament is incised sharply. Care should be taken to avoid excessive electro -cautery in this area and thus avoid injury to the hypogastric plexus, which may result in retrograde ejaculation. The dis -cectomy at the desired level is then carried out using curettes and rongeurs. The cartilaginous end plates are completely removed. The surface of the vertebral bodies are also decorti -cated to expose cancellous bone, allowing for optimal fusion. Care must be taken to avoid damage to the bony end plates. At this point, any signiÞcant osteophytes dorsally and ventrally can also be removed. Once discectomy is complete, depend -ing on the preoperative disc height and degree of foraminal stenosis, distraction of the disc space may be necessary. A variety of interbody implants are available. Each con -sists of an interbody space and an osteoconductive/osteoin -ductive substance to Þll the spacer. Common substances for spacers include iliac crest autograft, femoral ring allograft, tita -nium mesh cages, and cylindrical threaded bone dowels and titanium cages. Iliac crest autograft can be harvested at the Arcuate lineof posterior rectus sheathTransversalis fascia over peritoneum Left rectusmuscle retractedFIGURE 171-3 Retraction of rectus muscle exposing the posterior rectus sheath, including the arcuate line.Posterior rectus sheath Arcuate lineLeft rectus muscleAreolar adhesionof transversalis tendon to transversalis fascia Transversalis fascia overlying peritoneum FIGURE 171-4 Blunt dissection through the arcuate line to access the retroperitoneal space.Segmental artery (mid-vert. body) Sympathetic truck Retroperitoneal fat DescendingcolonLeft ureterAorta Inferior vena cava Abdominal contentsPeritoneum FIGURE 171-5 Sweeping of the peritoneal contents medially to visual-ize the retroperitoneal space.

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1959171 ¥ Anterior Lumbar Interbody Fusion: Indications and Techniques time of surgery and does not require Þlling of osteoconduc -tive/osteoinductive material. Nonautograft spacers, however, require Þlling of osteoconductive/osteoinductive substances. Cylindrical threaded bone dowels and titanium cages are advantageous in that they lower the risk of graft migration or backout, given the threaded surface is in contact with the end plates. Common osteoinductive/osteoconductive Þlling sub -stances include vertebral autograft, which can be acquired during surgery; cancellous autograft chips; demineralized bone matrix; and bone morphogenetic protein. Once the interbody graft has been implanted, intraop -erative radiographs are taken to ensure proper placement of the graft in lateral and anteroposterior dimensions ( Fig. 171-9 ). In addition, satisfactory disc height restoration and lordosis are conÞrmed during intraoperative imaging. The wound is then irrigated copiously, and hemostasis is meticulously achieved. Retraction on the peritoneum is then released, and the lining of the peritoneum is carefully inspected. Any tears found in the peritoneum should be primarily repaired. The rectus sheath is then closed with interrupted sutures to prevent the risk of ventral hernias. Following this, the skin is closed with staples or subcuticu -lar sutures. Postoperative images are obtained at the discre -tion of the treating surgeon ( Fig. 171-10 ).ComplicationsSeveral potential complications exist with ALIF surgery. Many of these complications can be avoided by proper visualization and identiÞcation of retroperitoneal struc -tures to minimize subsequent accidental injury to these structures. For example, proper identiÞcation of the ureter L4Hypogastric plexus L5-S1 diskL5FIGURE 171-6 Vascular anatomy in relation to vertebral levels, including the middle sacral artery and vein.Ascending lumbar vein Common iliac veins Inferior vena cava Lumbarsegmental veins Hemiazygosvein Thoracic segmental veins Arygous vein Superior vena cava Internal jugular Left common iliac vein Right commoniliac vein Middle sacral vein L5FIGURE 171-7 Venous anatomy including the middle sacral vein and ascending lumbar vein. The ascending lumbar vein (iliolumbar vein) should be ligated to minimize bleeding.FIGURE 171-8 Intraoperative photograph demonstrating a view of the L5-S1 disc space after retroperitoneal exposure. The left iliac artery is retracted laterally. The iliac vein is retracted medially.

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1960Section Nine ¥ NEUROSURGICAL MANAGEMENT OF SPINAL DISORDERS with subsequent medial retraction with the peritoneum can signiÞcantly decrease the risk of injury to this structure. One possibly devastating risk with anterior lumbar sur -gery is vascular injury. For this reason, many spine surgeons work with vascular surgeons during the exposure. A recent study demonstrated a 6.1% rate of vascular injury among 212 anterior lumbar interbody and fusion procedures per -formed. 27 Older studies have shown risk of vascular injury to be as high as 17%. 25Injury to the sympathetic hypogastric plexus may result in retrograde ejaculation. A transperitoneal approach to the lumbar spine seems to be associated with a higher rate of injury to the hypogastric plexus as compared to a ret -roperitoneal approach. The rate of retrograde ejaculation after anterior lumbar surgery has been quoted to be as high as 2.3%. 24 The descending sympathetic chain may also be injured with the anterior approach, which may result in a unilateral warm leg syndrome due to the loss of sympa -thetic activity in the affected extremity. Problems may arise with the lumbar spine and fusion construct postoperatively. Pseudarthrosis remains a prob -lem with any fusion surgery. However, adequate prepara -tion of the interbody space, including decortication of the surface of the vertebral bodies, can promote fusion. Pos -terior Þxation and stabilization have also been shown to increase fusion rates. Graft migration, as well as telescop -ing of the graft into the endplates, has been frequently observed postoperatively. Some surgeons advocate the use of an anterior plating device to decrease the risk of graft migration. Telescoping of the graft into an end plate may result if the bony end plate is damaged during surgery or if the cross-sectional area of the graft is too small relative to the cross-sectional area of the end plate. Loss of physiologic lordosis, failure to correct sagittal imbalance, and failure to improve disc height are frequent problems after ALIF. One reason for this may be settling of the graft into the end plate. In addition, these problems may be caused by placing an interbody graft that is too small. Therefore, careful preoperative planning with assessment of the radiographic images is essential for planning of graft dimensions. Postoperative ileus and bowel injury are also problems encountered with the anterior approach to the lumbar spine. A transperitoneal approach to the lumbar spine is associated with a signiÞcantly higher risk of these problems compared to a retroperitoneal approach. Postoperatively, early mobilization, limited use of narcotics, and adequate hydration are key strategies for dealing with ileus. The risk of deep venous thrombosis should be minimized with mobilization and prophylactic anticoagulation. ConclusionThe ALIF is a highly efÞcacious technique for fusing the lower lumbar spine in select patients with discogenic back pain. FIGURE 171-9 Intraoperative C-arm ßuoroscopic image during sizing of an ALIF graft at the L5-S1 interspace. The graft is maximally lordotic.ABFIGURE 171-10 A, Preoperative sagittal T2-weighted magnetic reso-nance image demonstrating severe degenerative spondylosis at L5-S1 in a 43-year-old man with severe low back and leg pain. B, Postoper-ative lateral radiograph of the same patient after ALIF at L5-S1 using a self-plating graft. Note the restora-tion of disc height and segmental lordosis.

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