Figure 2From: Increase of nerve growth factor levels in the human herniated intervertebral disc: can annular rupture trigger discogenic back pain?Protein levels of nerve growth factor (NGF, pg/mg total protein) measured using ELISA in herniated discs. Mean values are indicated by short horizontal lines. No significant correlation was found between NGF levels and the grade of disc degeneration (Pfirmann grade).Back to article page