Bone Healing: The Diamond Concept

Abstract

The incidence of fracture non-union has been estimated to be as high as 10 %. The treatment of fracture non-union remains challenging even for the most experienced surgeons. The presence of a poor soft tissue envelope, deformity, avascular bone edges, reduced bone stock, low-grade infection and patient related co-morbidities are some of the important contributing factors that need to be addressed. Evaluation of the complexity of the non-union and formulating the appropriate pre-operative plan and treatment modality requires good understanding of the pathogenicity of this condition and having extensive surgical experience.The state of both the mechanical and biological environment, is thought to play a crucial role in the decision making process regarding revision surgery. Application of the so-called 'diamond concept' provides the optimum mechano-biological conditions for bone repair and should be considered in cases where diffi culties to achieve union are anticipated. Types of Bone HealingWith regards to the histology of bone healing two basic types have been described, depending on the stability of fi xation of the fracture's bone fragments [ 2 , 3 , 6 ]. 1. The primary (direct) healing pattern occurs when there is absolute contact of the bone fragments (anatomical reduction) along with almost complete stability (commonly obtained with open reduction and internal fi xation) and therefore minimisation of the inter-fragmentary strains [ 7 , 8 ]. In this type of healing that rarely happens in nature, the disrupted continuity of the bone is re-established with regeneration of lamellar bone and the Harvesian system, and has no need of any remodelling [ 8 , 9 ]. 2. The secondary (indirect) healing pattern occurs in the vast majority of clinical cases and depends on the formation of fi brocartilaginous callus that matures to mineralised cartilage and fi nally bone [ 2 , 7 ]. Callus is formed as a physiological reaction to the inter-fragmentary movement and involves both intramembranous and endochondral ossifi cation [ 2 , 7 -9 ]. It originates from committed osteoprogenitor cells of the periosteum and undifferentiated multipotent mesenchymal stem cells (MSCs) [ 7 ]. Fracture Healing and Bone RepairSeveral types of tissues are involved in the process of fracture healing including cortical bone, periosteum, undifferentiated fascial tissue that surrounds the fracture, and bone marrow [ 9 , 10 ]. Bone repair follows a well defi ned chain of events starting with haematoma formation, followed by infl ammation, angiogenesis and granulation tissue formation, fi brous tissue formation, fi brocartilage, hyaline cartilage (soft callus), cartilage mineralisation, woven bone (hard callus), and fi nally remodelling [ 2 , 6 , 11 ]. The process of remodelling can last for several months.In more detail, following an injury the bone architecture and the surrounding soft tissue continuity are both disrupted. The concomitant tearing of the blood vessels at the site of injury leads to bleeding, activation of the coagulation casc...

Biological and molecular profile of fracture non‐union tissue: current insights

“…We deem essential that a widely accepted definition of the timeframe for non-unions should be set allowing an earlier intervention in such cases. The conceptual frame of the “diamond concept” for a successful fracture healing response should be considered in cases where bone repair is desirable 5 . Cellular therapies and inductive molecules with scaffolds have a role to play in future treatment strategies, as would do tissue engineering approaches 64 .…”

“…Bone healing is a complex but well-orchestrated physiological process which recapitulates aspects of the embryonic skeletal development in combination with the normal response to acute tissue injury 1 , 2 . It encompasses multiple biological phenomena and is margined by the combination of osteoconduction (scaffold formation), osteoinduction (timed cellular recruitment controlled by multiple signalling molecules) and osteogenesis (new bone formation) 2 – 5 . In contrast to the scar formation, which occurs in the majority of other tissue types in adults, bone has the innate capability to repair and regenerate, regaining its former biomechanical and biochemical properties 6 – 8 .…”

Stem Cell Interventions for Bone Healing: Fractures and Osteoporosis

“…Committed osteoprogenitor cells of the periosteum and undifferentiated multipotent MSCs are initially activated. Local and systemic regulatory factors such as VEGF, FGF, Insulin-like growth factor (IGF), TGFβ, various cytokines and hormones interact with these localised cells to attract more cells to the region and initiate the healing process [29,30].…”

“…Bone healing is controlled by the interaction of regulatory factors, such as cytokines and hormones; osteoconductive matrices or scaffolds, mechano-biology or relative mechanical stability of the fracture site, a population of stem cells and a blood supply [21,29]. Multiple cell types are involved in fracture healing, including osteoblasts, osteoclasts, osteocytes, osteoprogenitors and most importantly stem cells, which act in response to both mechanical signalling and the biochemical signalling cascade [33].…”

Treatment of a large osseous defect in a feline tarsus using a stem cell‐seeded custom implant

“…Ideal properties of graft material includes osteoinduction induced by bone growth factors, osteogenesis encouraged by osteoprogenitor cells, and osteoconduction provided by scaffolds (Dimitriou, Jones, McGonagle, & Giannoudis, 2011; Virk & Lieberman, 2012). Mechanical stability of the implant is crucial in order to provide stresses that favor bone formation (Giannoudis, Panteli, & Calori, 2014; Pobloth et al, 2018). At the same time, the implant has to be strong enough to withstand the imposed loads.…”