Background

Bone is the second most transplanted tissue with approximately 2.2 million grafting procedures performed annually worldwide as a result of trauma, infection, or disease. Issues associated with the gold standard use of autografts and allografts, particularly when massive quantities are needed, have stimulated the development of synthetic graft substitutes. However, long‐term incorporation and the stability of graft substitutes remain as challenges as there are many factors to consider, including the source of graft, systemic and local disease, graft mechanical properties, and so forth. To date, no bone graft substitute satisfies all of the prerequisites that are necessary to achieve successful and secured healing, particularly for critically sized defects that will not heal without intervention.

Summary

We have developed a three‐dimensional (3D) printed bioresorbable graft substitute to be used as an implant for the fusion of critically sized segmental bone defects. The graft substitute involves a skin‐ or core‐graded structure and contains variable porosity, pore size, and moduli at the skin and core layers, which are achieved by the series of vertical and horizontal conduits organized into a lattice to emulate cortical bone encapsulating cancellous bone. This two‐layer structure is based on the general features of native bone tissue to account for dissimilarities in bone morphology while possessing the ability to allow for load transfer to sustain physiological loads comparable with the adult human femur. Furthermore, the dimensions of the vertical and horizontal conduits, or pore sizes, of the inner core and outer skin layers were selected for optimal cell seeding to enable sustained biological transmission between the two layers and the generation of mechanical properties that emulate native bone tissue.

Benefits:

1. Emulates the hierarchical structure of native bone tissue
2. Possesses mechanical properties that are comparable to adult human femur
3. Potentially minimizes use of traditional metal fixation systems which increase the risk of postoperative complications
4. Enables patient‐specific customized design: local variations are readily customizable using computer‐aided design software to tailor the specific size and location of segmental bone of the patient to be replaced
5. Utilizes 3D printing for fabrication, which streamlines the manufacturing process compared to current gold standards
6. May be employed as templates on which cells can grow to generate tissue constructs with optimized properties to improve clinical outcomes of graft procedures

Value Proposition to key stakeholders:

Patients:

• Patient-specific and anatomically customized bone graft that is mechanically functional and bioactive

Surgeons:

• Single surgery is needed, which reduces recovery time and risk of postoperative complications thereby improving stability in long-term reconstruction

Payers:

• Alleviates financial burden due to single surgery
• Decreased hospital stays due to improved clinical outcomes
• Potentially reduces need for costly follow-up treatments

Applications: fusion of long bone defects as a result of fracture, bone tumor resections, and limb length discrepancy

Relevant keywords: bone graft substitute, loading frequency, mechanical stimulation, segmental bone replacement, 3D printing

Full Patent:  Dual Modulus Scaffold Designs for Bone Graft Incorporation and Stability