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Technical experience and postoperative complications with repeat transperitoneal approach to the lumbar spine in female Lewis rats

Rat models of lumbar intervertebral disc (IVD) degeneration are widely employed to characterize biologic-based therapeutics, but their anatomy and small size preclude consistent delivery of injectable therapeutics to the lumbar spine via the traditional posterolateral approach. Here, we describe our experience with a repeat ventral transperitoneal approach in female Lewis rats, enabling induction of IVD degeneration and later intervention via an injectable therapeutic. In the initial surgery, the ventral aspect of the L5/L6 IVD was accessed, and an annular defect was created using a #11 scalpel blade. Eight weeks after the initial surgery, follow-up surgery was performed via the same approach, and an injectable gelatin hydrogel was delivered using a 31G needle. A custom injection guard was developed to control injection depth, ensuring consistent delivery to the nucleus pulposus. Notable challenges associated with repeat surgery were increased tissue adhesion, intraoperative bleeding, and difficulty placing the injection guard due to mobile gastrointestinal tissues. Complication rates were 9.4% and 15.6% for the initial and repeat surgeries, respectively. The most frequent complications associated with repeat surgery were transient neuropraxia and significant intraoperative bleeding (6.3% each). The repeat transperitoneal approach is a reproducible method to facilitate both injury and later intervention in a female rat model of lumbar IVD degeneration.