Approach from Convex Side May Improve Vessel Protection During Lateral Access Surgery for Adult Scoliosis
Key findings
- In adults with scoliosis of the thoracolumbar spine, the overlap of the inferior vena cava and the vertebral endplate was significantly greater for left-sided curves than for right-sided curves
- At lower levels of the lumbar spine, there was posterior migration of the inferior vena cava, and it draped more over the vertebral endplate
- The aorta tended to assume a more anterior position in the lumbar spine
- There was significantly more accessible disk space, and significantly less disk-vessel overlap, when approaching a curve from the convex side than from the concave side
In adults with scoliosis of the thoracolumbar spine who undergo minimally invasive lateral access surgery, varying anatomic relationships between retroperitoneal vessels and intervertebral disk spaces increases the risk of vascular injury. Yet until now, no group has studied the overlap between the vessels and disk spaces in this subset of patients with scoliosis.
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Thomas D. Cha, MD, MBA, assistant chief of the Orthopaedic Spine Center at Massachusetts General Hospital, and colleagues found that the overlap between retroperitoneal vessels and inferior vertebral endplates at the disk level in scoliotic spines varies significantly with the direction of the curvature, level of the deformity, and degrees of axial rotation. In Clinical Spine Surgery, they explain how their findings can help surgeons protect the inferior vena cava (IVC) and aorta.
Researchers studied 62 consecutive patients with scoliosis of the thoracolumbar spine who had a high-quality CT scan or MRI available. They used the images to measure the anatomic position of retroperitoneal vessels in relationship to curve direction, location, magnitude and axial rotation.
The team found that at the cephalad level, the overlap of the IVC and the vertebral endplate was significantly greater for left-sided curves (14.7%) than for right-sided curves (1.0%) (P=.002). At the apex level, the respective figures were 15.4% and 3.7% (P=.002). There was no significant difference between left- and right-sided curves in the overlap with the aorta.
Overlap between the vertebral endplate and IVC at the cephalad, apex, and caudad end of the curve was significantly different between thoracolumbar and lumbar curves. There was also significant difference in overlap with the aorta at the cephalad and apex endplate, although not the caudad endplate.
The magnitude of a scoliosis curve did not affect the overlap between endplate and vessels, but the axial rotation did. Curves with axial rotation >15 degrees had significantly increased overlap at the caudad IVC, cephalad aorta and apex aorta.
There was significantly more accessible disk space when approaching a curve from the convex side than from the concave side (36.7 vs 34.0 mm, P<.001). Similarly, the percentage of the disk overlapped by a vessel was significantly less on the convex side of the curve than on the concave side (4.9% vs 12.4%, P<.001).
Dr. Cha and colleagues encourage surgeons to individualize each case plan, as usual. Still, they believe surgeons should consider migration of the IVC, especially in left-sided curves, when choosing the side of the approach. An approach from the convex side may be preferable to allow direct visualization of the migrated IVC and better control of any damage that occurs.
Conversely, the researchers note, in these patients, the aorta may be more posterior in the low thoracic and thoracolumbar region and more anterior in the lumbar spine. More anterior approaches need to be undertaken with caution.
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