Tortuosity of the iliac artery is associated with ipsilateral low back pain – a case-control study

Objectives

Thrust owing to the deflection of flow in the bend of an artery has been shown to be associated with clinical symptoms such as neurovascular compression syndromes or vocal cord palsy. This study investigated the association between tortuous iliac arteries and lateral low back pain, hypothesizing that the enhanced pulsatility found in tortuous iliac arteries causes pain by inflicting pulsatile microtrauma on the psoas muscle or its embedded nerve roots.

Methods

In this retrospective case-control study, participants in the main study (aged 40 - 80 years) were recruited on the basis of existing outpatient computed tomography (CT) scans of the abdomen showing no significant abnormality (exclusion criteria: malignant disease; degenerative lumbar disease; lumbar surgery, fracture, or structural deformity; axial arthritis; aneurysms of the abdominal aorta or iliac arteries; femoral hernia), selecting subjects with normal iliac arteries (control group, arteries bending >135°, n= 52), and markedly tortuous iliac arteries (study group, arterial bends ≤ 90°, n=47). Marked iliac tortuosity was subdivided into bends targeting the psoas muscle and bends passing in front of or behind the muscle. Due to significant differences in age and sex, calculations of the participants’ self-reported frequency and localization of low back pain were performed on matched pairs (n = 31; 17 male and 14 female pairs, mean age of 62.5 years in the control group and 63.2 years in the study group). Concomitantly, an estimate of the frequency of marked iliac tortuosity was obtained by screening 500 consecutive CT scans.

Results

Marked iliac tortuosity on one or both sides was found in 39.2% of subjects aged 40 - 80 years, more often in males (p<0.00001), and more often on the left side (p<0.0001). Lateral low back pain was reported more often by participants in the study group (n=14) than by those in the control group (n=6) (p=0.031). In the matched study group, lateral low back pain was reported on 11 of the 20 sides of a markedly tortuous iliac artery targeting the psoas muscle. This was more often than on the side of a markedly tortuous iliac artery passing in front of or behind the muscle (four of 27 sides, p=0.005) and more often than in the matched control group (8 of 62 sides, p=0.0003).

Conclusion

Iliac artery tortuosity targeting the psoas muscle is associated with ipsilateral low back pain. This may explain low back pain in some cases currently regarded as nonspecific.

Arterial tortuosity can cause symptoms when targeting vulnerable structures. In cases of otherwise unexplained focal neurological symptoms, screening imaging for presence and orientation of arterial tortuosity in the affected area is recommended.