EVALUATION OF THE SHORT TERM HOST RESPONSE AND BIOMECHANICS OF AN ABSORBABLE POLY-4-HYDROXYBUTYRATE SCAFFOLD IN A SHEEP MODEL FOLLOWING VAGINAL IMPLANTATION

Objective: To compare the host and biomechanical response to a fully absorbable poly-4-hydroxybutyrate (P4HB) scaffold to the response to PP mesh in an animal model of vaginal POP surgery. Design: A study employing a sheep model Setting: KU Leuven Center for Surgical Technologies Population: 14 parous female Mule sheep Methods: P4HB scaffolds were surgically implanted in the posterior vaginal wall of sheep. The comparative PP mesh data were obtained from an identical protocol. Main outcome measures: Gross necropsy, histological and biomechanical evaluation of explants, and the in vivo P4HB scaffold degradation were evaluated at 60- and 180-days post-implantation. Results: Gross necropsy revealed no implant related adverse events using P4HB scaffolds. The tensile stiffness of the P4HB explants increased at 180-days (12.498 ± 2.66 N/mm (P=0.019)) as compared to 60-days (4.585 ± 1.57 N/mm) post-implantation, while P4HB degraded gradually. P4HB scaffolds exhibited excellent tissue integration with dense connective tissue and a moderate initial host response. P4HB scaffolds induced a significantly higher M2/M1 ratio (1.70 ± 0.67 SD, score 0-4), as compared to PP mesh (0.99 ± 0.78 SEM, score 0-4) at 180-days. Conclusions: P4HB scaffold facilitated a gradual load transfer to vaginal tissue over time. The fully absorbable P4HB scaffold, in comparison to PP mesh, has a favorable host response with comparable load bearing capacity. If these results are also observed at longer follow-up, a clinical study for vaginal POP surgery may be warranted to demonstrate efficacy. Key words: Pelvic organ prolapse, vaginal surgery, Poly-4-hydroxybutyrate, degradable scaffold, host response, biomechanics.