The characteristics of spinopelvic sagittal alignment in patients with lumbar disc degenerative diseases.

PURPOSE: A comparative study of the spinopelvic sagittal alignment in patients with lumbar disc degeneration or herniation (LDD/LDH) in normal population was designed to analyse the role of sagittal anatomical parameter (pelvic incidence, PI) and positional parameters in the pathogenesis and development of the disease. Several comparative studies of these patients with asymptomatic controls have been done. However, in previous studies without lumbar MRI, a certain number of asymptomatic LDD patients should have been included in the control group and then impacted on the results.

METHODS: Based on MRI findings, we divided 60 LDD or LDH patients and 110 asymptomatic volunteers into the normal group (NG) and the degeneration group (DG), which was further subdivided into the symptomatic (SDG) and asymptomatic (ADG) subgroups according to patients' symptoms. Standing full spine radiographs were used to measure sagittal parameters, including PI, sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), sagittal vertical axis (SVA), and sacrum-bicoxofemoral distance (SFD).

RESULTS: The PI, SS and LL in DG were significantly lower than NG, while the SVA and SFD were significantly greater (P < 0.05). PI correlated well with the SS and LL in all subjects. However, the trend lines of SS or LL over PI were downward in DG. PI was similar in SDG and ADG (P = 0.716) but SS and LL were significantly lower and SVA was significantly greater (P < 0.05).

CONCLUSIONS: PI may play a predisposing role in the pathogenesis of lumbar disc degenerative diseases. The secondary structural and compensatory factors would lead to a straighter spine after disc degenerative change.