Optimization of a 3d-printed Endoprosthetic Sleeve to Enhance Scaffold Efficacy

Successful healing of large bone defects remains a critical challenge in orthopedic medicine, often resulting in infections, reoperations, and limb loss, with significant personal and economic consequences. Current tissue engineering approaches utilizing highly porous osteoconductive scaffolds such as gyroid are effective in large defects but lack sufficient mechanical strength to support human-scale loads. We designed a 3D printed a novel polycaprolactone (PCL) endoprosthetic sleeve that structurally supports a highly porous 3D printed scaffold to enhance bone formation. It is well known that scaffold stability and internal strain are critical factors for effective bone growth. Immobilizing the scaffold in the bone defect accelerates the integration of the scaffold into the host bone and internal strains of less than 5% are known to accelerate bone formation. As the next step of our work, we are designing our sleeves to induce controlled strain in the scaffold that we expect will enhance the rate and maturity of bone formation. We hypothesize that the sleeve's curvature can be engineered to induce controlled transverse strain into the scaffold body. Enabled by 3D printing, we will manipulate curvature, cell geometry and internal angles of the infill pattern to regulate Poisson's effect in the structure, allowing precise control over the transverse strain in the scaffold. 3D printing offers the flexibility to customize the sleeve's design according to individual bone geometry, enabling easy modification of infill patterns to achieve desired mechanical properties on a patient-specific basis. In this study, we examined the effects of combined compression and torsional loading on 3D printed PLA gyroid scaffolds (~3cm in height) attached to cadaveric ovine metatarsi and secured with metal plate fixation. Strain measurements were conducted using rosette strain gauges in a half-bridge circuit with and without the optimized PCL sleeve.