The Optimal Timing of Hydrogel Injection for Treatment of Intervertebral Disc Degeneration: Quantitative Analysis Based on T1ρ MR Imaging

STUDY DESIGN Animal experimental study OBJECTIVE.: To investigate the optimal time of hydrogel injection for regenerating intervertebral disc degeneration (IDD) based on T1ρ magnetic resonance imaging (MRI). SUMMARY OF BACKGROUND DATA Currently, different approaches are being pursued to regenerate the IDD. However, the optimal timing for the regenerative intervention is unclear. METHODS The slowly, progressive IDD models were established in 18 rhesus monkeys. On the basis of the MR T1ρ values of the discs, the rhesus monkeys were divided into severe (T1ρ values:  0.05). However, in the severe group, the T1ρ values decreased significantly after 1 month and leveled at approximately 70 ms after 6 months, with significant difference compared to the values at 1 month (P   0.05). However, the histological score in the severe group at 12 months were significantly higher than the preoperative scores (P < 0.05). CONCLUSIONS This study suggested that the moderate degenerative stage of IDD (T1ρ values from 95 ms to 80 ms) could be the optimal time for hydrogel injection aimed at the regenerative intervention, based on T1ρ-MR imaging technique and quantitative analysis. LEVEL OF EVIDENCE N/A.