The statics of postural pelvic tilt scoliosis; a radiographic study on 288 consecutive chronic LBP patients.

Standing orthoradiography of the lumbar spine, the hip and knee joints revealed a lateral lumbar curve of 5-22° (mean=9·0°, s.d.=4·2°) secondary to leg length inequality in 186 or 64·6% of 288 consecutive patients with chronic low back pain (LBP). The incidence of leg length inequality in LBP patients (mean=10·6mm, s.d.=6·7mm) was significantly higher (P<0·001) than in 366 asymptomatic controls (mean=5·1 mm, s.d.=2·4 mm). In 170 cases (91·4%), the lumbar curve was convex toward the short leg side, correlating significantly with the degree of lateral inclination of the sacrum (r=+0·97) and with the amount of leg length inequality (r=-0·81). The curvature was generally coupled with an axial rotation of the vertebrae moving the spinous processes toward the concavity, as well as with an opposite rotation of the pelvis (r=+0·77), which were calculated to result in a significant torsional stress on the L5-S1 segment.