University of Pennsylvania Kennett Square, Pennsylvania
Lumbar intervertebral disc degeneration (IVDD) causes significant debilitation in humans and canines. Degeneration begins in the nucleus pulposus (NP), where proteoglycan loss compromises tissue function. We hypothesized that NP hydrogel augmentation can be used to safely and effectively mitigate disc degeneration by restoring intervertebral disc (IVD) biomechanics. Six adult goats underwent chemonucleolysis with CABC to induce IVDD in three lumbar discs.Ten days later, the degenerated NP was augmented in two IVD with an injectable hydrogel via an open retroperitoneal, transpsoatic approach. Post-operative disc height was calculated using monthly lateral radiographs. After 2.5 years, contrast-enhanced MRI was performed. Animals were euthanized after 6wk, 12wk, or 2.5 years for histopathology. At study completion, 8/11 hydrogels remained in situ. In two animals, annulus fibrosus (AF) rupture with hydrogel leakage into the vertebral canal occurred. One hydrogel migrated into the lateral soft tissue at 20 months post-nucleoplasty. One animal had temporary paresis from lumbar plexus injury; no other persistent neurologic deficits/pain were observed. Hydrogel-treated discs maintained height, while CABC-degenerated disc height significantly decreased. MRI revealed no difference in end-plate diffusion between hydrogel-treated and native discs. Histopathology revealed minimal to no hydrogel-associated inflammatory changes. Our findings demonstrate that hydrogel NP replacement is safe and mitigates signs of IVDD. Limitations include a small cohort sample size. NP augmentation is a promising treatment modality for early-onset human and canine IVDD. Current surgical therapies target degenerated discs after NP herniation; however, injectable hydrogel therapy would allow mitigation of further progression before irreversible damage occurs.
