A radiographic evaluation on the effect of body position change on retroperitoneal oblique corridor

English Keywords:MRI  Oblique lateral approach  Position change  Anatomical characteristic

English Abstract:

  【Abstract】 Objectives: To analyze whether right lateral decubitus position would change the retroperitoneal oblique corridor to the L1-L5 intervertebral discs. Methods: 40 volunteers were randomly enrolled and MRI(magnetic resonance imaging) scan was performed from L1 to L5 in supine and right lateral decubitus positions respectively. In image across the center of each disc, O was defined as the center of a disc; A(supine)/A′(right lateral decubitus) and B(supine)/B′(right lateral decubitus) were located in left lateral border of the aorta(or iliac artery) and the anterior medial border of the psoas. The distances of AB and A′B′ of all levels were measured and were compared with each other at all levels; A′B′ of different levels was compared and the associations with sex, BMI(body mass index) and relative psoas cross-sectional area(PCSA) were explored. Results: BMI of 40 subjects ranged from 18.4 to 26.5 and 6 cases had high aortic bifurcations. The distances of AB and A′B′(mm) at each level were: L1/2, 14.80±3.89 and 12.37±3.62; L2/3, 12.85±4.16 and 9.96±3.37; L3/4, 12.24±4.10 and 10.85±3.30; L4/5, 9.78±4.69 and 9.72±4.37, L4/5 of subjects with high aortic bifurcation, 7.72±3.56 and 6.71±2.86. AB was significantly larger than A′B′ at L1/2, L2/3, L3/4(P=0.005, 0.003, 0.020) without significant difference at L4/5 no matter whether the subjects had high aortic bifurcation or not(P=0.946, 0.097). There was significant difference between levels(P=0.046), A′B′ in L1/2 was largest, followed by L3/4, L2/3 and L4/5. There was no difference of A′B′ at each level between sexes(all P＞0.05). Negative linear relationship were found among A′B′, BMI and PCSA at L3/4(P=0.015, 0.000) and A′B′ at L1/2 was also affected by PCSA(P=0.024). Conclusions: Retroperitoneal oblique corridors at L1/2, L2/3 and L3/4 decreased from supine to lateral position, which meant that the value of pre-operative lumbar MRI images obtained at supine position might be limited and more intra-operative psoas tractation should be needed. Oblique corridors were different between levels and BMI, PCSA could affect the corridors at L1/2 and L3/4, which should also be taken into consideration before operation.