BONE GRAFTS AND BONE SUBSTITUTES

Image Credit: Medical News Today 

“Our health is something we often take for granted. But, there are some things in life that should never be taken for granted.
Take care of yourself.”
-Catherine Pulsifer

The bones, and our skeletal structure, are aspects of our bodies that we often don’t take notice of because they are within our internal structure. In some instances, there are a multitude of possibilities that result in the need for bones to be corrected. During these corrective procedures, there are currently a series of bone inclusions and additions that orthopaedic surgeons will utilize in the process of healing the bone structure, and improving the structural integrity of the bones. These options include the utilization of various bone grafts that are either taken from the patient’s body, a medically approved cadaver, or even materials that have been fabricated by material scientists. 

With many advances in fields like synthetic bone substitutes, it is quite possible that improvements in human orthopaedic surgery will be achieved. The future of orthopaedic healing, includes the utilization of technologies like composite bone grafts, that contain healing agents embedded in a osteoconductive matrix. Embedded in this matrix includes the combination of osteogenic cells and osteoinductive growth factors. With the right nutritious environment in place, the ability for the bone to regenerate itself will take place. With a variety of options for healing, let us delve into a few critical categories of bone grafts and bone substitutes: 

Autografts

Autografts are bone transfusions, that are generated from the patient’s own body, and transferred to the relevant section of the body (such as the spine) in order to be fused with the bone that is currently to be healed. There are usually two or more surgeries that are conducted in the process of treatment. This process usually includes the surgery that is dedicated to remove the bone from the base source. This surgery is known as a harvesting surgery and it is utilized in order to generate the bone graft. Harvested bones are usually taken from locations such as the ribs, the iliac crest of the pelvis, and also sections of the spine. Medical advances are always taking place, and the inherent risks that are associated with harvesting and graft transfer, are currently being optimized by the utilization of material science that generates suitable bone substitutes. 

Factors considered in Autograft Utilization 

Within medical practices, the autograft is classified as the gold standard for certain procedures such as spine fusions. With a spine fusion, the appropriate conditions for a solid bone bridge are achieved. The new bone growth is highly favored. The grafted bone also contains osteophytes and other bone growth enhancers that are able to generate new bone growth. The autografts has found favor in the field because there is [1]:

  • Greater chance of fusion success vs. allograft (cadaver bone) and some types of bone graft substitutes
  • No risk of disease transmission (vs. using cadaver bone).

The main disadvantages of using autograft include the risks and possible complications associated with conducting any surgical procedure, e.g.:

  • Surgical wound problems, such as infection
  • Nerve injury (rare)
  • Bleeding (rare)

There is also a limited supply of this type of bone graft and sometimes it needs to be supplemented with some form of bone graft substitute[1].

Bone Substitutes

Bone substitutes are being increasingly utilized in surgery. The number of bone grafts that are achieved via the utilization of bone substitutes is approaching several million each year. With the limitations that are inherent in the utilization of autografts highlighted above, medical science has identified alternate ways to heal bones that are able to overcome these restraints. 

Bone substitutes include elements such as allografts, xenograft substitutes, and ceramic based synthetic bone structures. Of these three bone substitutes, the ceramic based synthetic bone substitutes are the therapies that are widely used in clinical procedures. These ceramic bone substitutes are proving themselves to be effective. In the minimally invasive realm, there is also the possibility to utilize injectable cements. There is still ongoing research that is dedicated to the advancement of the field. 

Incorporation of a Bone Graft

The incorporation of a bone graft is a process that is defined as a multi-step cascade. Once the transfusion surgery is completed, there will be a healing process that enables the graft to be incorporated into the body. The healing process is one that involves the generation of inflammatory cells, along with the movement of the existing mesenchymal stem cells to the site of the graft. These mesenchymal stem cells will then intelligently differentiate into healing cells known as chrondoblasts and osteoblasts, and facilitate the healing of the bone. There is a regeneration of blood flow to the graft site, known as revascularization. Via a series of mechanisms, eventually the bone is internally remodeled, in order to restore the integrity of the bone, and enable the patient to regain full mobility and weight bearing capacity. 

What Is The Ideal Bone Substitute? 

The ideal bone substitute is a composite that is biocompatible to the healing site. In some instances, there have been adverse effects of the incorporation of a bone substitute. The immune system in general is very sensitive to any foreign bodies that are introduced to it, and there is often an immune response that initially attacks, then embraces the graft. The reaction to grafts is an individual one. Biocompatiblity is a capability of new bone substitutes, that will enable the substitute to be incorporated into the body within the minimal amount of time. The key parameters that bone substitutes should embody, are identified by the medical community. When analysis is conducted, these key parameters are to be facilitated by any material that is to be incorporated into the body. The parameters not only factor in the ability for the bone structures to be incorporated into the body, but also for the material to be affordable. 

Advances in technology, will ensure that future treatments are customizeable to the patient’s body. Until such time, the current available pool is one that is increasingly enabling faster patient recovery, and inherent adaptability for inclusion into the body. 

References: 

  1. Spine Health: https://www.spine-health.com/treatment/spinal-fusion/autograft-patients-own-bone
  2. Bone Substitutes in Orthopaedic Surgery: https://bit.ly/30Kg1Aj

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Dr. Gordon Slater

Dr. Slater is one of the first foot and ankle surgeons in Australia to adopt minimally invasive surgical techniques. He routinely uses MIS to treat a range of conditions, including bunions.

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Dr Gordon Slater is a highly-skilled surgeon specialising in foot and ankle conditions and sports injuries. Dr Slater is one of the first foot and ankle surgeons in Australia to adopt minimally invasive surgical techniques. He routinely uses MIS to treat a range of conditions, including bunions. MIS  has many advantages including shorter operating times, reduced post-operative pain, reduced risk of infection, minimal scarring and better cosmetic outcomes.

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