4D Imaging of Soft Tissue and Implanted Biomaterial Mechanics; A Barbed-Suture Case Study for Tendon Repair

Timely, recent developments in X-ray micro-computed tomography (XµCT) imaging such as increased resolution and improved sample preparation are enabling non-destructive time lapse imaging of polymeric biomaterials when implanted in soft tissue, which we demonstrate herein. Imaging the full 3D structure of an implanted biomaterial provides new opportunities to assess micromechanics of the interface between implant and tissues, and how this changes over time as force is applied in load bearing musculoskeletal applications. In this paper we present a case study demonstrating in situ XµCT and FE analysis, using a dynamically loaded barbed suture repair for its novel use in tendon tissue. The aim of this study was to identify the distribution of stress in the suture and tendon as load is applied. The data gained demonstrates clear 3D visualization of micro-scale features in both the tissue and implant in wet conditions. XµCT imaging has revealed, for the first time, pores around the suture, preventing full engagement of all the barbs with the tendon tissue. Subsequent finite element analysis reveals the localized stress and strain, which is not evenly distributed along the suture, or throughout the tissue. This case study demonstrates for the first time a powerful in situ mechanical imaging tool, which could be readily adapted by other laboratories to interrogate and optimize the interface between implanted biomaterials and soft tissue.