Multilevel magnetic resonance imaging analysis of multifidus-longissimus cleavage planes in the lumbar spine and clinical application to the Wiltse approach

Objective: To determine the anatomic location of the multifidus-longissimus intermuscular cleavage plane in a Chinese population and thereby to aid surgery by Wiltse's approach. Methodology: Two hundred patients (100 males, 100 females) were enrolled. The distance between the midline and the intermuscular plane at each disc level between L1 and S1 was measured on axial T2-weighted magnetic resonance images (MRI). Age, sex and body mass index (BMI) were also recorded. Results: The mean measured distance differed significantly between disc levels (P<0.05). At L5-S1, it was 33.56 mm; at L4-L5, 29.85 mm; at L3-L4, 24.97 mm; at L2-L3, 19.91 mm; and at L1-L2, 16.17 mm. Mean distances were significantly greater in males than in females (1 mm) at L1-L2, L2-L3 and L3-L4. There was no significant relationship between distance and height, weight or age. Conclusions: The location of the intermuscular cleavage plane was related to disc level and not correlated with age, height or weight. Mean distances were slightly greater in males than in females at L1-L2, L2-L3 and L3-4, which was not consistent with a previous report. These findings may aid surgery by Wiltse's approach.