Overview of Craniofacial Distraction Osteogenesis
Distraction osteogenesis is a medical term that refers to the formation of new bone. This is achieved by slowly separating two pieces of a bone that has been deliberately cut or fractured, a procedure known as an osteotomy. This technique was first used on jawbones in Germany in the 1930s. It mimics the normal process of how bones heal after an injury.
After a bone injury, the body forms a fibrous tissue called a callus at the site of the injury. This tissue later turns into bone, a process known as ossification. If the injury is not kept still, this transformation into bone won’t fully happen and a fibrous union will occur.
In cases of accidental bone fractures, this is an undesired outcome, which is why casts or other solid braces are used. However, in distraction osteogenesis, doctors intentionally move the pieces of the fractured bone along a set path. This movement gradually stretches the callus, which is then made immobile to allow ossification. The end result is that the bone at the site of the osteotomy becomes longer.
This particular technique has been widely used to correct deformities of the cranial or skull bones. It’s used to lengthen bones in the jaw, midface, and cranium (top part of the skull). These procedures result in strong bones that resist returning to their previous state. They also prompt the soft tissues around the bone to adapt to the changes.
Doctors have successfully used this craniofacial distraction osteogenesis to treat various patients with abnormalities of the skull, both in patients with known genetic conditions (syndromic) and those without (non-syndromic). This approach has helped these patients gain not only cosmetic improvements but also better functionality, making it a superior choice when compared to other techniques.
Anatomy and Physiology of Craniofacial Distraction Osteogenesis
The development of the head and facial features of a child undergo changes as they grow from infancy to adulthood. To understand how this growth occurs, we can divide the head and facial region into three sections: the neurocranium (the part of the skull that surrounds the brain, which are made of two structures: the calvaria forming the top of the skull and the basicranium forming the bottom), the nasomaxillary complex (the part that includes the nose and upper jaw), and the mandible (the lower jaw). In infants, the neurocranium is much larger than the nasomaxillary complex and the mandible. But as a child grows, their nose, mouth, and lower jaw also grow to balance out the shape of the adult face.
The top of the skull, the calvaria, forms gradually as the brain grows. Tiny bones separate and create new bone growth. By the time a child is approximately four years old, the calvaria is fully formed. However, if these bones join together too early, it can result in a condition called craniosynostosis. The basicranium, the bottom portion of the skull, grows more slowly than the calvaria and reaches 95% of its adult size by the age of 10.
The nose and upper jaw, or the nasomaxillary complex, generally grow towards the front and down from the basicranium, due to soft-tissue growth. The face achieves maturity at about 12 years of age. As this complex grows, the lower jaw or the mandible protrudes downwards and forward. In males, the mandible achieves its adult size well after puberty, typically in their early twenties.
The formation of bone, or osteogenesis, starts with the initial formation of a primary bone that is not too strong and matures into a stronger secondary bone. There are two ways it can happen: through the formation of bone over existing cartilage or through a process called intramembranous ossification in the connective tissue. This process is used in certain bone graft surgeries: undifferentiated cells are signaled to turn into bone-forming cells, creating primary bone material which turns into secondary bone.
There are three phases to fracture healing: inflammation, repair, and remodeling. The inflammation phase involves a blood clot forming at the fracture site, which also aids the formation of cells required for healing. During the repair stage, primary soft tissue starts forming at the fracture site. Then, the cells at the fracture site transform into other types of cells leading to the formation of new bone. Finally, during the remodeling phase, the cells present start transforming and new blood vessels form, resulting in the damaged bone being replaced with new, healthy bone tissue.
Why do People Need Craniofacial Distraction Osteogenesis
The main idea behind distraction osteogenesis is to lengthen a selected bone to improve its function.
For babies born with Pierre Robin sequence, a condition where they have a small lower jaw, tongue that falls back in the throat and sometimes a cleft palate, this can cause issues with their breathing. If other measures, such as changing their position or using special equipment to help with breathing do not work, distraction osteogenesis can be a good alternative. This process helps by increasing the length or height of the lower jaw, specifically in the branch that goes up to join the rest of the skull.
In the case of midface hypoplasia, where the middle part of the face is underdeveloped, distraction osteogenesis can also be used as a solution. This condition can be present on its own or as a part of certain facial syndromes, such as Treacher Collins syndrome or Cohen syndrome. People with midface hypoplasia often have noticeable cheekbone retrusion, an irregular bite, and their eyes may bulge due to the lower eye socket being positioned further back than normal. This can also cause breathing difficulties or severe sleep apnea. Distraction osteogenesis is a tool used to correct these abnormalities.
Craniosynostosis is another condition where distraction osteogenesis can be helpful. This is a condition where the skull fuses too early in infants. If not treated, it can lead to severe facial deformities, increased pressure within the brain, intellectual disability, delays in development, seizures, blindness, and even death. Using distraction osteogenesis, doctors can expand the front or back part of the skull to relieve the increased pressure within the brain caused by this condition.
When a Person Should Avoid Craniofacial Distraction Osteogenesis
If a person has other health issues that make surgery risky, they should not undergo craniofacial distraction osteogenesis, which is a surgery to correct abnormal bone growth in the skull and face. Instead, if nonsurgical methods work well to alleviate their symptoms, these should be preferred, especially in young children.
It’s also important to differentiate between positional plagiocephaly and true craniosynostosis. Positional plagiocephaly is when a baby’s head becomes flat due to lying in one position for too long. On the other hand, craniosynostosis is a condition where the joints between the bones of a baby’s skull close too early. The key difference is that positional plagiocephaly can be managed without surgery, unlike true craniosynostosis.
Equipment used for Craniofacial Distraction Osteogenesis
There are two types of devices used in certain medical procedures: internal and external, manufactured by different companies around the world.
Internal devices are entirely placed inside the body, and are fixed directly to the bone with screws. There are two types of these; one moves in a straight line (linear) and one moves along a curve (curvilinear). This device has a part outside the body that can be adjusted to increase the gap for treatment. Some doctors believe that because these devices are directly attached to the bone, the treatment is more effective and predictable. Also, these devices might be more visually tolerable for parents and families during the treatment and healing process. However, these devices need to be removed with another operation once the healing phase is finished.
External devices, on the other hand, rely on titanium pins or wires that are inserted through the skin to both ends of the bone segments. The treating device is then attached to the skin where these pins have been inserted. These devices also come in both straight and curve-movement models. They were developed before the internal devices, thus we have more long-term data about their effectiveness. However, some doctors believe that they don’t work as efficiently as internal devices because some amount of the force used in the treatment might get lost due to the bending of the pins. But, the benefit of external devices is that they can allow for more accurate corrections by adjusting how the device moves during the treatment period, which isn’t possible with internal devices. After the healing process is over, the pins are just removed in a simple procedure; opening the body for a second procedure is not needed.
Who is needed to perform Craniofacial Distraction Osteogenesis?
Distraction osteogenesis is a type of surgery performed while you are fully asleep due to general anesthesia. This surgical operation needs a team of professionals which includes a special doctor who performs the surgery also known as a surgeon, a professional who puts you to sleep called an anesthetist, and nursing staff who assist with the operation. A surgical assistant plays an important role as they greatly help in making the procedure run smoothly.
Preparing for Craniofacial Distraction Osteogenesis
Some surgeons use a special planning technique before surgery. This method involves using high-quality scans of the body and specialized computer programs to create a 3D model of the area they will be operating on. The software is usually provided by the company that makes the surgical instruments. This technique allows the surgeon to perform a practice run of the surgery on a computer to help plan out the procedure and see the best outcome. Using this model, surgeons can choose the right surgical tools and devices in advance. They can even 3D print models and adjust surgical plates or devices according to these models before the operation.
However, it’s crucial to note that this type of planning is not available everywhere and can add to the overall cost of the surgery.
How is Craniofacial Distraction Osteogenesis performed
The process of growing new bone, which we call craniofacial osteogenesis, can be broken down into four main steps:
1) Making the Initial Cut and Placing the Device: First, a small surgical cut is made in the bone where growth is desired. After this, a device called a distractor is put in place. Sometimes, if there’s an existing line or joint in the skull, the surgeon may use this instead of making a new cut. The distractor helps the growth occur in the right direction, and after it’s attached, the surgeon will test its movement to make sure there are no restrictions. Distractors can either be located inside or outside the body, and the choice depends on the goals of the surgery and the body part involved.
2) Waiting Phase: After the cut and device placement, the device is not activated for a period of between a day and five days. This waiting period allows for the early stages of bone healing to begin.
3) Active Growth Phase: Over several days to a few weeks, the distractor device is slowly activated either once or twice a day. This slow movement gradually stretches the newly formed bone, promoting more growth. This phase continues until the required length has been reached.
4) Settling Phase: After the desired length has been achieved, the distractor is left in place for several weeks. During this time, the new bone begins to harden and eventually looks like mature bone. The device keeps the bone from moving, which helps the bone to continue developing.
A common use for this procedure is to lengthen the lower jaw in babies and children who have a restricted airway due to a severely underdeveloped jaw. The cut is made at the back of the jaw, and then a distractor device is attached and tested to make sure everything moves correctly. The growth is often performed more than necessary, as some shrinkage is likely to occur afterward.
Another use for this technique is for facial bone advancements. Distraction devices are placed and then tested to ensure there aren’t any obstructions. The device is usually left in place for about two months before removal.
This technique can also be used to expand the skull in patients with craniosynostosis, a condition where the joints between the bones of the baby’s skull close prematurely. After the cut is made, a distractor device is placed and checked to ensure proper mobility.
Overall, craniofacial osteogenesis is a versatile technique that can help improve various conditions and deformities.
Possible Complications of Craniofacial Distraction Osteogenesis
Distraction osteogenesis is a medical procedure often used to fix problems with bones in your jaw. While the procedure is generally safe, there are some risks to consider, though many are rare and have solutions available. Here are a few potential issues you may encounter.
First, the procedure might not result in the perfect alignment of the jaw. However, doctors usually overcorrect the jaw placement a bit, expecting some degree of relapse. This way, the final result is still satisfactory.
Another issue could be the device used in the operation failing, more commonly in procedures involving the jawbone. But this is quite rare, with the failure rate being close to 1%.
Sometimes, the device used may push through the skin instead of moving the bone. This can happen if the bone segments are impeded or can’t move freely as required. During the procedure, doctors make sure that the bones can move along the right path to avoid this complication.
Teeth could also be damaged during the procedure. To avoid this, your doctor will study your jaw and teeth beforehand and strategically position the surgical cuts. Using advanced 3D imaging and virtual planning techniques, doctors can also reduce the chance of damage to your teeth.
Important nerves located in the face and jaw could be affected during the surgery. Precaution is taken to avoid this, but permanent nerve damage is very rare and occurs in less than 1% of such procedures.
Malocclusion, or misaligning of teeth, is another risk of jaw surgery. You might need orthodontics or braces later to correct your dental arrangement. It’s also possible to develop temporomandibular joint symptoms, which are problems related to the joint connecting your jaw to your skull.
In rare cases, the fluid cushioning your brain and spinal cord, called cerebrospinal fluid, may leak. However, small leaks are generally not harmful and can be managed easily.
You might also notice some scarring after the procedure. The risk is lower if the surgical incisions are made in irregular shapes, and if particular techniques are used to minimize the effects. However, if scarring does occur, it can be treated later with further surgical procedures.
The chance of infection is minimized by using systemic (affecting your entire body) antibiotics during the procedure, and topical (applied on the skin) antibiotics post-procedure. In some higher-risk operations, additional antibiotics may be used.
What Else Should I Know About Craniofacial Distraction Osteogenesis?
Distraction osteogenesis is a medical procedure used to help patients suffering from misshaped skull bones. This approach can relieve blocked upper airways or reduce pressure inside the skull that’s due to craniosynostosis – the premature fusion of skull bones. It’s often used in treating people with skull or face abnormalities.
Mandibular distraction osteogenesis, a specific type which focuses on the lower jaw, has shown exceptional results in avoiding or removing a tube from the windpipe in almost 98% of patients with a specific facial anomaly known as isolated Pierre Robin Sequence. However, it is less effective for those with lower airway issues like tracheomalacia, where the windpipe is softer than normal. For these patients, some doctors might delay lower jaw distraction given that the rate of needing a windpipe opening remains similar whether the procedure is performed or not.
When carried out for a sunken-in face, distraction osteogenesis can significantly enhance the facial look, safeguard the eyes from harmful eye pressures, alleviate increased skull pressure, and effectively treat sleep apnea. Additionally, it can increase the success rate of facial advancement surgery compared to traditional rigid methods and may avoid follow-up operations, often needed with traditional surgeries in childhood.
Expanding the skull by distraction osteogenesis can be less difficult than traditional single-stage expansion surgery, particularly at the back of the skull. It has fewer complications and allows for a much greater skull expansion, enabling successful correction of increased skull pressure.
