Bone Graft - MSmiline

Bone grafting is a surgical procedure that replaces missing bone with material from the patient's own body, an artificial, synthetic, or natural substitute. Bone grafting is used to repair bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly.

Biological mechanisms governing bone grafting

Chart depicting the properties of various types of bone graft sources.

Bone grafting is possible because bone tissue, unlike most other tissues, has the ability to regenerate completely if provided the space into which to grow. As native bone grows, it will generally replaces the graft material completely, resulting in a fully integrated region of new bone. The biologic mechanisms that provide a rationale for bone grafting are osteoconduction, osteoinduction and osteogenesis.The chart at right reveals which of these properties apply to the different types of bone graft material.

 

Osteoconduction

Osteoconduction occurs when the bone graft material serves as a scaffold for new bone growth that is perpetuated by the native bone. Osteoblasts from the margin of the defect that is being grafted utilize the bone graft material as a framework upon which to spread and generate new bone. In the very least, a bone graft material should be osteoconductive.

Osteoinduction

Osteoinduction involves the stimulation of osteoprogenitor cells to differentiate into osteoblasts that then begin new bone formation. The most widely studied type of osteoinductive cell mediators are bone morphogenetic proteins (BMPs). A bone graft material that is osteoconductive and osteoinduction will not only serve as a scaffold for currently existing osteoblasts but will also trigger the formation of new osteoblasts, theoretically promoting faster integration of the graft.

Osteogenesis

Osteogenesis occurs when vital osteoblasts originating from the bone graft material contribute to new bone growth along with bone growth generated via the other two mechanisms.

Uses

The most common use of bone grafting is in the application of dental implants, in order to restore the edentulous area of a missing tooth. Dental implants require bones underneath them for support and to have the implant integrate properly into the mouth. People who have been edentulous (without teeth) for a prolonged period may not have enough bone left in the necessary locations. In this case, bone can be taken from the chin or from the pilot holes for the implants or even from the iliac crest of the pelvis and inserted into the mouth underneath the new implant.

In general, bone grafts are either used en block (such as from the chin or the ascending ramus area of the lower jaw) or particulated, in order to be able to adapt it better to a defect.

Another common bone graft, which is more substantial than those used for dental implants, is of the fibular shaft. After the segment of the fibular shaft has been removed normal activities such as running and jumping are permitted on the leg with the bone deficit. The grafted, vascularized fibulas have been used to restore skeletal integrity to long bones of limbs in which congenital bone defects exist and to replace segments of bone after trauma or malignant tumor invasion. The periosteum and nutrient artery are generally removed with the piece of bone so that the graft will remain alive and grow when transplanted into the new host site. Once the transplanted bone is secured into its new location it generally restores blood supply to the bone in which it has been attached.

Besides the main use of bone grafting--dental implants--this procedure is used to fuse joints to prevent movement, repair broken bones that have bone loss, and repair broken bone that has not yet healed.

Bone grafts are used in hopes that the defective bone will be healed or will regrow with little to no graft rejection.

 

Procedure

Depending on where the bone graft is needed, a different doctor may be requested to do the surgery. Doctors that do bone graft procedures are commonly orthopedic surgeons, otolaryngology head and neck surgeons, neurosurgeons, craniofacial surgeons, oral and maxillofacial surgeons, and periodontists.

 

Risks

As with any procedure, there are risks involved; among these include reactions to medicine and problems breathing, bleeding, and infection.Infection is reported to occur in less than 1% of cases and is curable with antibiotics. Overall, patients with a preexisting illness are at a higher risk of getting an infection as opposed to those who are overall healthy

 

Risks for grafts from the iliac crest

Some of the potential risks and complications of bone grafts employing the iliac crest as a donor site include:

  • acquired bowel herniation (this becomes a risk for larger donor sites (>4 cm)). About 20 cases have been reported in the literature from 1945 till 1989and only a few hundred cases have been reported worldwide
  • meralgia paresthetica (injury to the lateral femoral cutaneous nerve also called Bernhardt-Roth's syndrome)
  • pelvic instability
  • fracture (extremely rare and usually with other factors)
  • injury to the clunial nerves (this will cause posterior pelvic pain which is worsened by sitting)
  • injury to the ilioinguinal nerve
  • infection
  • minor hematoma (a common occurrence)
  • deep hematoma requiring surgical intervention
  • seroma
  • ureteral injury
  • pseudoaneurysm of iliac artery (rare)
  • tumor transplantation
  • cosmetic defects (chiefly caused by not preserving the superior pelvic brim)
  • chronic pain

Bone grafts harvested from the posterior iliac crest in general have less morbidity, but depending on the type of surgery, may require a flip while the patient is under general anesthesia.

 

Recovery and Aftercare

The amount of time it takes for an individual to recovery depends on the severity of the injury being treated and lasts anywhere from 2 weeks to 2 months with a possibility of vigorous exercise being barred for up to 6 months.