OBJECTIVETo study the biomechanical relationship between iliac rotation displacement and L(4,5) disc degeneration, and to provide clinical evidences for the prevention and treatment of L(4,5) disc degeneration and herniation.

METHODSFrom March 2012 to February 2014,68 patients with lumbar disc herniation combined with sacroiliac joint disorders were selected. Among them, 42 patients with L(4,5) disc herniation combined with sacroiliac joint disorders included 22 males and 20 females, ranging in age from 19 to 63 years old, with an average of (51.78 +/- 20.18) years old, and the duration of the disease ranged from 1 to 126 months with an average of (11.18 +/- 9.23) months. Twenty-six patients with L5S1 disc herniation combined with sacroiliac joint disorders included 11 males and 15 females, ranging in age from18 to 65 years old with an average of (45.53 +/- 27.23) years old, and the duration of the disease ranged from 0.5 to 103 months with an average of (11.99 +/- 12.56) months. Sixty-eight anteroposterior lumbar radiographs, 68 lateral lumbar radiographs,and 68 pelvic plain films were taken. The degree of lumbar scoliosis, pelvic tilt,and disc thickness were measured. The correlation between pelvic tilt and lumbar scoliosis ,lumbar scoliosis and disc thickness were studied by using linear and regression methods. The hiomechanical analysis was performed.

RESULTSThere was a positive correlation between pelvic tilt and lumbar scoliosis in patients with L(4,5) disk herniation (R=0.49, P=0.00). There was a causal relationship and good linear proportional relationship (Y=3.05+1.07X, P=0.00) in the two variables. There was a negative correlation between lumbar scoliosis and intervertebral space in male patients with L (4,5) disk herniation (R = -0.50, P=0.01). There was a causal relationship and good linear proportional relationship in the two variables (Y=13.09-0.27X, P=0.02). But there was a positive correlation between lumbar scoliosis and intervertebral space in male patients with L5S1 disk herniation (R=0.46, P=0.04).

CONCLUSIONIliac rotational displacement are closely related with L(4,5) disc degeneration and herniation in biomechanics. A new concepts and therapeutic approach is provided for clinical treatment of chronic and refractory herniation of L(4,5) disc in patients