INTRODUCTION: Surgical treatment for lumbar degenerative disc disease includes discectomy, decompression, and spinal fusion. One potential treatment as an adjunct or alternative to surgery for includes the percutaneous delivery of agents to support nucleus pulposus (NP) functional mechanics. In this study, the effect of a recently developed injectable NP implant on disc mechanics was investigated.
METHODS: In vitro mechanical testing on mature ovine discs was performed in three stages: intact, discectomy, and after treatment via NP implant or sham control without implant (n=10/group). At each stage (intact/discectomy/treatment) mechanical testing consisted of a cyclic tension‐compression to 300 N (1.5X body weight). The discectomy removed 35% of NP via standard clinical procedures. The implant treatment injected a novel hydrogel consisting of oxidized hyalronic acid and gelatin, which we have shown has material properties similar to the native NP. The sham control had all same procedures without material implantation. Range of motion (ROM), compressive stiffness, and tensile stiffness were evaluated. In addition, tested discs were cut axially for structural observations. (cont'd)
RESULTS: Hydrogel implantation reduced ROM 17% (p < 0.05) and returned ROM of the treatment group to normal levels (pre‐discectomy 0.71mm, post‐implantation 0.72mm). The discs randomized to the sham control group had a 36.7% increase in ROM between intact and final mechanical analysis (p < 0.05). The compressive and tensile stiffness with repeated testing after discectomy, for both implant and sham control groups, remained unchanged from the initial loading after discectomy as the AF was not repaired. Gross morphology images confirmed no ejection of NP implant upon injection and testing.
DISCUSSION: An injectable implant that mimics non‐degenerate NP has the potential to return disc axial range of motion (ROM) to normal.