Intradiscal application of hyaluronic acid in the non-human primate lumbar spine: radiological results.

Abstract

Prospectively, with randomized segment-treatment assignment, and with blinded evaluators, lumbar motion segments in Cercopithecus monkeys were analyzed for macroscopic and radiological changes 24 weeks after nucleotomy and nucleotomy with additional intradiscal application of different hyaluronic acid formulations versus untreated control segments. The objective was to find out whether hyaluronic acid is able to influence the degenerative cascade in nonhuman primates after nucleotomy. In a similar procedure, hyaluronic acid has proven to decrease degeneration after nucleotomy in a Minipig model. This is the first such study ever undertaken in primates, thus trying to overcome the known limitations of non-primate spine models. Twenty monkeys with four segments each obtained nucleotomy in three segments and solely exposure of another control segment. Nucleotomy was performed from a transpsoatic retroperitoneal approach. Preoperative radiographs and follow-up radiographs, magnetic resonance imaging (MRI), computed tomography (CT), Q-CT with bone mineral density measurements and three-dimensional reconstruction were obtained and analyzed qualitatively and quantitatively. Segments with high-molecular-weight hyaluronic acid (Hylan G-F 20) application proved to be significantly superior over those with a standard nucleotomy in radiographs, MR images, CT scans, and macroscopic appearance at follow-up. Control segments remained unaffected. Interdependence between the different methods validated the utilized methods of quantitative radiological assessment of degeneration. Hylan G-F 20 appears to be a possible adjunct in reducing postoperative degeneration in an animal nucleotomy model. It deserves further evaluation, despite the fact that the mechanisms of its effects are still speculative.