An in-vivo study exploring correlations between early-to-moderate disc degeneration and flexion mobility in the lumbar spine
Purpose: Early disc degeneration (DD) has been thought to be associated with loss of spine stability. However, before this can be understood in relation to back pain, it is necessary to know the relationship between DD and intervertebral motion in people without pain. This study aimed to find out if early to moderate DD is associated with intervertebral motion in people without back pain. Methods: Ten pain free adults, aged 51-71 received recumbent and weight bearing MRI scans and quantitative fluoroscopy (QF) screenings during recumbent and upright lumbar flexion. Forty individual level and 10 composite (L2-S1) radiographic and MRI DD gradings were recorded and correlated with intervertebral flexion ROM, translation, laxity, and motion sharing inequality and variability for both positions. Results: Kinematic values were similar to previous control studies. DD was evidenced up to moderate levels by both radiographic and MRI grading. Disc height loss correlated slightly, but negatively with flexion during weight bearing flexion (R=-0.356, p=0.0.025). Composite MRI DD and T2 signal loss evidenced similar relationships (R=-0.305, R= -0.267) but did not reach statistical significance (p=0.056, p=0.096). No significant relationships between any other kinematic variables and DD were found. Conclusion: This study found only small, indefinite associations between early-to-moderate DD and intervertebral motion in healthy controls. Motion sharing in the absence of pain was also not related to early DD, consistent with previous control studies. Further research is needed to investigate these relationships in patients.