High-strength scaffolds for bone regeneration

Abstract

Repair of large skeletal defects that are intrinsic to skeletal stability represents the greatest challenge for orthopaedic surgeons. IntroductionBone defects arising from disease, trauma, infection or genetic abnormality are reconstructed with non-biodegradable materials such as stainless steel or titanium to restore skeletal function. 2,3These materials have been associated with long-term problems such as loosening, 4 peri-prosthetic fracture and infection. 5The modern approach is marked by a shift in emphasis from replacement to regeneration of tissue. 6,7 This is achieved by way of human-or animal-derived grafts (autograft, allograft or xenograft), bone graft substitute (BGS) materials, growth factors 8 or bioinorganics. 9 The drawbacks associated with human-and animal-derived grafts such as limited availability, high cost, poor remodelling, donor site morbidity, delayed healing and disease transmission have driven extensive research into synthetic alternatives. [10][11][12][13] The principal advantages of BGSs are unlimited supply, ease of sterilisation and storage, predictable mechanical properties, excellent bone in-growth and moderate cost. 14,15 Bone defects can be categorised into those that are intrinsic to skeletal stability and those that are not. Currently, there are numerous commercially available low-strength, void-filling BGS products but none are indicated to offer structural support to the skeleton. [16][17][18] Thus, there is an urgent need for BGSs that can replace allogenous or autogenous grafts in large defects, for example, in resections for infection or tumour. In these instances, bone grafts can be as large as 20 cm and their locations (joints, spine and long bones) require them to bear load and function with instrumentation to maintain the stability of the skeleton.2,19-21 Non-structural biomaterials can repair segmental defects in combination with instrumentation such as plates and screws but these require an additional retrieval procedure.22 A BGS material with the strength of cortical bone will benefit many patients and be particularly useful in spinal arthrodesis where high strength and osteoinductivity are essential to ensure rapid fusion. 23,24High-strength scaffolds for bone regeneration Meredith and Mallick

Towards the Development of Artificial Bone Grafts: Combining Synthetic Biomineralisation with 3D Printing

“…However, the small increase in volume and the appearance of a large number of nanopores in the rehydrated scaffolds suggests that this technique does not render the polymer chains completely crystalline which would have inhibited any dissolution dependent change polymer swelling as in the case of freeze-dried samples. The increased porosity of rehydrated air-dried scaffolds together with the printed macropores could, therefore, contribute to biologically relevant porosity during in vivo applications [44,45]. These results together with the observation that air-drying can potentially reduce the susceptibility of 3D chitosan hydrogel-based scaffolds to deformation under compression are the main reason for preferentially selecting this dehydration technique.…”

Porous hydroxyapatite‐bioactive glass hybrid scaffolds fabricated via ceramic honeycomb extrusion

“…The ideal BGS should be bioactive, porous, and mechanically sound . Ceramic honeycomb extrusion is a technique capable of achieving porous ceramic BGS with compressive strengths comparable to that of cortical bone, which has seldom been achieved by both traditional and contemporary fabrication techniques used to fabricate BGS. In addition, honeycomb extrusion is unique in that it offers controlled and interconnected porosity, fabrication of large‐sized scaffolds and is industrially scalable .…”

“…In spite of these advantageous, the technique has not been widely adopted for BGS. As such, honeycomb extrusion has only been used to fabricate hydroxyapatite (HA) or β‐tricalcium phosphate (β‐TCP) . Although honeycomb extrusion was successful in fabricating these materials with mechanical properties exceeding that of traditional methods (i.e.…”