Anatomic relationship between superior mesenteric artery and aorta before and after surgical correction of thoracolumbar kyphosis.

Study Design: A computed tomographic study.

Objective: To investigate the changed anatomic relationship between the superior mesenteric artery and the aorta in surgically treated ankylosing spondylitis (AS) patients with thoracolumbar kyphosis.

Summary Of Background Data: Superior mesenteric artery syndrome in kyphosis patients after surgery has been reported. To date, the changed aortomesenteric angle and distance in AS patients undergoing surgical correction of kyphosis have not yet been addressed.

Methods: Thirty-three AS patients with thoracolumbar kyphosis subjected to pedicle subtraction osteotomy were prospectively recruited. Radiographic measurements included global kyphosis (GK), thoracic kyphosis (TK), local kyphosis (LK), and lumbar lordosis. The aortomesenteric angle and distance were measured on both preoperative and postoperative computed tomography images. The height and weight of these patients were also recorded.

Results: The average height significantly increased from 159.7±5.1 cm before surgery to 167.2±5.3 cm after surgery (P<0.001), whereas the average weight changed from 59.3±6.8 kg to 59.5±6.9 kg (P>0.05). GK, TK, LK, and lumbar lordosis were corrected from 77.7, 40.2, 19.4, and 2.8 degrees before surgery to 37.1, 38.4, -21.9, and -32 degrees after surgery, respectively. All the changes of these parameters were found to be significantly different (P<0.001) except that of TK (P>0.05). With the correction of kyphosis, the aortomesenteric angle significantly decreased from 29.3 to 23.4 degrees (P<0.001), whereas the aortomesenteric distance significantly decreased from 25.7 to 20.4 mm (P<0.001). It is to be noted that the changes of GK, LK, and height were significantly correlated with the decrements of aortomesenteric angle and distance (P<0.05).

Conclusions: The correlations of the surgical correction of kyphosis and the decreased aortomesenteric angle and distance in AS patients were quantitatively confirmed by our study. Spine surgeons should be aware of the potential risk for the development of superior mesenteric artery syndrome after kyphosis correction in AS patients.