Predictability of degenerative disc disease by lumbar sagittal alignment on conventional radiograph in comparison with cross-sectional magnetic resonance imaging

Background: Degenerative disc disease (DDD) affects approximately 80% of the population. Changes in the magnitude of lumbar lordosis significantly change the weight-bearing patterns in lumbar facet joints and intervertebral discs. It is essential to understand the contribution of hypo and hyperlordosis toward the development of disc degeneration disease. Materials and Methods: A retrospective study of X-ray and magnetic resonance imaging (MRI) of the lumbosacral spine of 200 patients with chronic low back ache. The lumbar lordotic angle was measured in a standing lateral radiograph using Cobb's method (between the lines drawn along the inferior end plate of D12 and the superior end plate of S1 vertebrae). DDD was assessed on MRI based on the Pfirrmann grading system. The correlation between the lordosis measured on the radiograph and DDD on MRI was assessed. Results: We analyzed the lumbar sagittal alignment effect on the degree of disc degenerative disease. Out of 200 patients, 70 had no disc degenerative disease (Grade I, II) whose Cobb's angle was 45°–75°. The remaining 130 patients showed disc changes (Grades III-V) on MRI and had Cobb's angle <45° or >75°. There was a statistically significant difference between Cobb's angle in normal and DDD patients with P = 0.009 (P < 0.05). Conclusion: DDD correlated with deviation from an optimal lumbar lordotic angle (Cobb's angle) of 45° to 75°. Deviation from optimal values would compromise the optimal weight-bearing conditions on the lumbar spine resulting in DDD. These results may well have implications for the diagnosis, prevention, treatment, and rehabilitation of DDD.