Fig. 1From: Paraspinal muscle changes after single-level posterior lumbar fusion: volumetric analyses and literature reviewMeasurements of paraspinal muscles. MF, multifidus; ES, erector spinae; P, psoas. a = semi-major axis (cm). b = semi-minor axis which is perpendicular to the semi-major axis (cm). A = maximum muscle diameter (cm). B = maximum diameter perpendicular to A on the same slice (cm). h = vertical height (cm)Back to article page