Fig. 33.1
Anterior view of the retroperitoneal vascular vessels. The aorta artery runs to the left and divides at the L4–L5 intervertebral disc into the two common iliac arteries. The inferior vena cava is formed at the fifth lumbar vertebra by the union of the common iliac veins and ascends to the right of the median plane
The abdominal aorta arises and branches from the ventral wall (celiac, superior mesenteric, and inferior mesenteric arteries) and lateral wall (renal, the middle suprarenal, and the testicular or ovarian arteries). The four pairs of lumbar arteries arise dorsolaterally and their course is dorsomedial. On the right, they run dorsal to the inferior vena cava, dividing between the transverse processes into the ventral and dorsal branches (Fig. 33.2). The dorsal branch passes dorsally lateral to the articular processes and supplies mainly the spinal cord and cauda equina. The largest of these dorsal branches denominates the radicularis magna artery (Adamkiewicz).
Fig. 33.2
Right lateral view of the lumbar spine where the lumbar arteries run dorsal to the inferior vena cava. The inferior vena cava migrates as it descends from zone A at L1 to zone I at L5
Tributaries of the inferior vena cava are the common iliac veins (L5), the lumbar veins, the right testicular or ovarian vein (the left drains into the left renal vein), the renal veins, the azygos vein, the right suprarenal vein (the left also drains into the renal vein), the inferior phrenic veins, and the hepatic veins. The lumbar veins consist of four or five segmental pairs. They may drain separately into the inferior vena cava or the common iliac vein.
The distribution of abdominal large vessels and the psoas major of each lumbar intervertebral space is inconsistent. Lumbar intervertebral spaces were divided in six zones from the anterior to the posterior border of the vertebral body [8]. The anterior aspect of the anterior margin of the vertebral body was defined as zone A and the posterior aspect of the posterior margin as zone P; zones I, II, III, and IV were distributed equally between the anterior margin and the posterior margin from the anterior to the posterior, respectively.
The inferior vena cava on the right side migrates from zone A to zone I as it descends from L1 to L5 [9]. Based on the distribution of the inferior vena cava, the right-side extreme lateral interbody fusion (XLIF) approach does not injure the vena cava at zones II–P of intervertebral spaces L1/L2, L2/L3, L3/L4, and L4/L5 (Fig. 33.2) [10].
The abdominal aortas at intervertebral spaces L1/L2, L2/L3, and L3/L4 were located mostly to the left of zone A, 95.8 %, 85.4 %, and 79.1 %, respectively [9]. At the L4/L5 intervertebral space, about 62.6 % of the abdominal aortas are divided into bilateral iliac arteries, and these branches were located at zone A (Fig. 33.3) [9]. Left-side XLIF approaches at zones II–P of L1/L2–L3/L4 intervertebral spaces and at the I–P zone of L4/L5 intervertebral space do not injure the aorta [9]. The approach must pass through the psoas major at zone II of L3/L4 to avoid injuring the aorta and nerve root or else pass through the psoas major at zones I–II of L4/L5 [9].
Fig. 33.3
Left lateral view of the lumbar spine where the aorta artery migrates is located at zone A in the intervertebral spaces L1/L2, L2/L3, and L3/L4. In the L4/L5 intervertebral space, about 62.6 % of the abdominal aortas are divided into bilateral iliac arteries, and these branches were located at zone A
For convenient operation, the surgery should be performed through the psoas major via the location between zone II and zone III of both lumbar intervertebral spaces of L1/L2 and L2/L3 [9]. This would not injure the vena cava and nerve plexus. The approach must be through the psoas major at zone II of both L3/L4 and L4/L5 to avoid injury to the vena cava and plexus (Figs. 33.3 and 33.4) [9].
Fig. 33.4
Left lateral view of the lumbar spine where the psoas major is located over the lumbar spine
The position of either the inferior vein cava or right common iliac vein with respect to the anterior intervertebral plane measured −4.3 mm at L1–2, −1.3 mm at L2–3, even with the anterior intervertebral plane at L3–4, +2.1 mm at L4–5, and +4.9 mm at L5–S1 (Fig. 33.1) [11]. When a “typical” 20-mm operative corridor is used, the neurovascular structures would be vulnerable to injury at L4–5 in 21 and 44 % of patients when using left- and right-sided approaches, respectively (Figs. 33.2 and 33.3) [11].
33.3 Incidence of Vascular Complications in Lumbar Spine Surgery
Injury to the retroperitoneal vessels can occur after posterior, anterior, or lateral approaches to the lumbar spine.
33.3.1 Posterior Approach
33.3.2 Anterior Conventional Approach
There are a much greater number of vascular injuries by anterior approach. The number ranges from 1.3 to 15.6 % due to the presence of the great vessels and their branches and tributaries in the surgical field or nearby where they can be inadvertently injured either during dissection or during retraction [2].
33.3.3 Lateral or Extreme Lateral Retroperitoneal Transpsoas Approach
In the largest XLIF series published, there was no report of vascular complications following the surgery in 600 patients and at 741 levels [15]. Vascular injury by XLIF procedure is only published as a case report of iatrogenic lumbar artery pseudoaneurysm following XLIF when endovascular embolization was performed [16].
33.4 Surgical Features in Lateral Retroperitoneal Transpsoas Interbody Fusion
The use of XLIF in the lumbar spine cephalic to L5–S1 circumvents the dissection and retraction of the large retroperitoneal vessels that is one of the major complications of the anterior approach and consequently minimizes the risk of vascular injuries [15, 17, 18].
The XLIF technique uses a small 3-cm incision that limits the visualization of the surgical field and exposes the surgeon to problems and hazards that do not exist when doing similar procedures in an open technique. Surgeons depend on high-quality fluoroscopic imaging and must rely on intraoperative fluoroscopic images and electromyography monitoring during most of the procedure. Specific risks include injury to the exiting nerve root and laceration of the retroperitoneal vessels during the deployment of the surgical retractors and the discectomy procedure [18].
The neurovascular structures would be vulnerable to injury at L4–5 in lateral transpsoas approach with a higher incidence using right-sided (44 %) rather than left-sided (21 %) approaches [11].
The surgeons must bear in mind that it is usually during L4–L5 XLIF that a high percentage of patients require neurovascular retraction, especially on the right side. The neurovascular anatomy must be well studied during preoperative planning in order to detect the patients that may not be ideal candidates for this approach [11]. Besides neurovascular retraction, the risk of vascular lesion is significantly increased at the L4–L5 level because the more anterior position of the nerve root forces the discectomy window more anteriorly, which in turn increases the risk of injury to the ipsilateral and contralateral vessels and the relatively posterior location of the retroperitoneal vascular structures [18].
The risks are further increased with rotational deformity of the spine [18]. In the case of scoliosis, the vessels on the concave side of the curvature were positioned relatively posterior to their position in the normally aligned spines [18]. The overlap of the right vessels over the vertebral body reached 43.9 % in the levoscoliotic spines, compared with 12.2 % in the normal group. The left vessels’ overlap in the dextroscoliotic spines reached 19.8 %, compared with 1.2 % in the normal group (P < 0.05). As a result of the greater degree of overlap between the neurovascular structures and the vertebral body found in the scoliosis subgroup, the surgical safe zone decreased to 40 % in the levoscoliotic spines and 61 % in the dextroscoliotic spines, compared with 70 % in the nonscoliotic group. The altered location of the neurovascular structures depended mostly on the degree of rotatory deformity, measuring 12° in the levoscoliotic and 11° in the dextroscoliotic spines. Focal coronal deformity or lateral listhesis did not seem to affect the position of these structures [18].
33.5 Preventive Measures of Vascular Complications in Anterior Lumbar Spine Surgery
The popularity and the increasing numbers of XLIF procedures highlight a better understanding of the expected complications, the predictive factors for the patient, and the surgical technique and preventive measures [5, 19]. The measures adopted to prevent vascular injury start with good preoperative planning, expert skills during surgery, and close monitoring in the postoperative period (Table 33.1).
Table 33.1
Preventive measures for vascular complications in anterior or lateral lumbar spine surgery during the preoperative, operative, and postoperative period
Patient care | Preventive measures |
|---|---|
Preoperative period | Good preoperative planning |
Identification of vascular position and its relation to the pathology and the surgical corridor | |
Knowledge of anatomy of the deformity | |
Knowledge of the patient-related variables | |
Operative period | Mechanical and pharmacological prevention of venous thrombi in the lower limbs |
Careful positioning of the patient’s legs | |
Three-dimensional anatomic knowledge of the surgical area | |
Gentle surgical manipulation | |
Adherence to intraoperative EMG | |
Avoid endplate violation during discectomy and implant insertion | |
Postoperative period | Thromboembolic prophylaxis |
Early patient mobilization |
33.5.1 Preoperative Period
Accurate preoperative planning means: (1) precise knowledge of the location of the lumbar nerve roots, abdominal wall nerves, and nerves on the surface of the psoas muscle; (2) identification of the vascular position and its relation to the pathology and the surgical corridor; (3) high point of the iliac crest and its correlation with the lumbar spine; (4) anatomy of the deformity with information about the coronal and sagittal angle, vertebra rotation, asymmetry of the intervertebral disc, lateral listhesis, and presence of the osteophytes; and (5) knowledge of the patient-related variables, such as age, BMI, bone densitometry, and comorbidities [20].
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