Introduction Using a non-human primate model, the purpose of this in-vivo investigation was to evaluate the efficacy of porcine small intestine submucosa (PSIS) for anterior longitudinal ligament replacement and as an anti-adhesion barrier following total disc arthroplasty. Success criteria were based on post-mortem vascular adhesion tenacity scores, biomechanical, histological and immunohistochemical analyses.

Methods A total of ten mature male baboons (Papio cynocephalus) were included in the current study and followed for a period of six-months post-operatively. Each animal underwent an anterior transperitoneal approach followed by a total disc arthroplasty procedure at L5-L6 using one of the following treatments: (1) Charité Disc Prosthesis alone (n=5) or (2) Charité Disc Prosthesis + PSIS (n=5). Following anterior annular and anterior longitudinal ligament (ALL) resection, complete diskectomy and endplate decortication, the Charité Device (Size 1) was implanted according to the manufacturer’s specifications. The PSIS material (40mm x 30mm width) was secured across the operative site using surgical bone staples with the abluminal side oriented towards the bone. Post-mortem analysis included vascular adhesion tenacity scores (0–5), histopathology of the operative site ALL, non-destructive biomechanical testing and histomorphometry.

Results All animals survived the operative procedure and post-operative interval without significant intra- or peri-operative complication. Vascular adhesion tenacity scores were markedly lower for the PSIS treatments (14/25) versus the Charité alone (20/25) (p=0.057). Gross histopathological analysis demonstrated disorganized collagenous matrix anteriorly spanning the disc arthroplasty site in 4/5 (80%) of the PSIS specimens compared to 2/5 (40%) for the Charité alone treatments. Plain film radiographic analysis showed no lucencies or loosening of any prosthetic vertebral endplate. Multi-directional flexibility testing demonstrated increased range of motion for both treatment groups under axial rotation and decreased motion in lateral bending when compared to the intact spine condition (p< 0.05). The neutral zone values were significantly higher in axial rotation and flexion extension for the both treatments (p< 0.05), with no differences in lateral bending.

Discussion Using a non-human primate model, the current study investigated in-vivo response to PSIS following total disc arthroplasty. Surgical application of the PSIS appears to reduce great vessel adhesion and improve regeneration of collagenous tissues at the operative disc space. However, there were no differences in the operative segment range of motion or neutral zone when comparing the two treatments. The current study serves as a basic scientific basis for ongoing clinical investigations into the use and efficacy of PSIS material following total disc arthroplasty.