Repair of segmental ulna defects using a ß-TCP implant in combination with a heparan sulfate glycosaminoglycan variant.

ABSTRACT

Given the wide spread clinical use of ceramic-based bone void fillers, we sought to determine the efficacy of an FDA-approved ß-tricalcium phosphate bone graft substitute (JAX™) in combination with a carboxymethyl cellulose (CMC) handling agent that included a particular heparan glycosaminoglycan (GAG) variant, herein referred to as HS3. Having recently demonstrated efficacy of a combination collagen/HS3 device, we further aimed to determine the support that HS3 could offer a handling agent used to administer a more tissue-relevant bone void filler. This study evaluated the JAX™-HS3 combination device in 1.5 cm critical-sized defects in the ulna bones of 27 male New Zealand White rabbits. Treatment groups consisted of JAX™ applied with CMC alone, or JAX™ with CMC containing either 30 µg or 100 µg of the HS3 GAG. Data based on radiographic, µCT, mechanical, and histological analyses at 4 and 8 weeks post-surgery, clearly demonstrate enhanced new bone formation in the JAX™-HS3 combination treated defects compared to treatment with JAX™ alone. The efficacy of such a combination advocates for inclusion of HS3 in handling agents used in the preparation of various bone void fillers being used in orthopaedic surgery. STATEMENT OF SIGNIFICANCE: Synthetic bone grafts and demineralized bone matrices are gaining prominence as alternatives to autologous and allogeneic bone grafts and are frequently administered in granular form, necessitating their combination with a handling agent. Typical handling agents include glycerol, gelatin, cellulose, hyaluronic acid and lecithin, formulated as hydrogels, which can be further enhanced by the addition of heparan sulfate (HS) glycosaminoglycans that augment the osteostimulatory properties of the graft. Here we assessed the efficacy of ß-TCP granules combined with a hydrogel consisting of carboxymethyl cellulose and the HS variant (HS3) previously shown to enhance osteogenic healing. The data advocates for HS3 to be included during the formulation of hydrogel-based carriers that support the various bone void fillers being used in orthopaedic surgery.