Overview of External Fixation Principles and Overview
Doctors have used a technique called external fixation to treat broken bones for over 2000 years, starting with Hippocrates. Simply put, this method keeps the broken bone in place and protects the surrounding tissue. The way doctors use this technique has changed a lot over the years, but the basic principles are the same. It helps keep the bone’s length, position, and rotation consistent during healing. External fixation can be used temporarily or for the entire healing process, and sometimes, it is used along with other internal methods. This is a key skill for doctors treating trauma injuries, specifically for breaks in the arms, legs, and pelvis.
How a fracture heals depends on the type of treatment used and how stable the fracture is. For instance, if the fracture is very stable, such as when a technique called compression plating is used, healing will occur in a specific way. If the fracture is less stable, like when external fixation is used, the healing process is different. The amount of stability in the bone can be altered depending on how the external fixation is set up.
There are several ways to change the level of stiffness and stability. For example, changing the arrangement of the pins used in the process can improve stability. Putting more pins, increasing their spread, and placing them closer to the break all help. But the placement must also consider any future surgeries. Increasing the size of the pins can also strengthen the setup, but larger pins could also potentially lead to new fractures.
Different types of pins, like self-drilling pins, trocar tip pins, and hydroxyapatite-coated pins are available. Strengthening the setup could also include increasing the size of the rods, placing them closer to the bone, or using more than one rod. The rods are attached to the pins using clamps. Nowadays, carbon fiber, being stiffer than stainless steel, is often used for these rods.
The various types of external fixators include uniplanar, multiplanar, unilateral, bilateral, and circular fixators. Depending on the shape and stability needed, these different techniques can be used. Some allow the patient to put weight on the limb and move their joints during treatment, but these are harder to apply. More complex setups include hybrid frames, which combine different techniques.
There’s no one-size-fits-all when it comes to treating fractures. The level of stability must be just right for healing to take place. That’s why it’s crucial for doctors to understand the basics of treating fractures because more stable isn’t always better when it comes to external fixation.
Anatomy and Physiology of External Fixation Principles and Overview
Understanding the specific structure of the body’s anatomy, depending on where an injury is and what type of supporting device is used, plays a significant role in treatment. In particular, certain devices called circular frames require a deep understanding of your body’s anatomy. This piece will give an overview of the safe areas and potential structures at risk when pins are placed in your thigh bone (femur), shin bone (tibia), pelvis, upper arm bone (humerus), and forearm in medical procedures.
In an experiment involving cadavers (dead bodies used for scientific study), researchers found out that a branch of the femoral nerve (a nerve in the leg) crosses the front part of the femur at an average distance of 5.8 cm and 2 cm from a certain point. The joint reflection, which is important in avoiding penetration into the knee joint that could lead to joint inflammation, can be as high as 7.4 cm above the knee cap or patella. The femoral artery (a major artery in the leg) lies directly in front of the femoral head and moves down the thigh bone. A “safe zone” has been found for placing pins on the femur to ensure lesser risk. However, pins placed on the outer side of the femur does not pose a risk to important structures like nerves and blood vessels, but these could cause some tension in the tissues known as the fascia lata and vastus lateralis.
Regarding safe pin placement in the tibia, you can feel a border just under the skin which is suitable. The advice is for pins to be placed at least 14 mm from the knee to avoid penetrating into the knee joint. Special care has to be taken to avoid injuring a bundle of nerves and blood vessels. The heel bone (calcaneus) has many nerves structures around it and particularly, a nerve called the medial calcaneal nerve is at the most risk when a specific type of pin is placed.
There are two main ways of fixing the pelvis externally. The iliac crest site (top part of the hip bone) can be easily felt and found quickly. Inserting a pin here is safe as long as the inner and outer surfaces of the pelvis are not penetrated. Another technique involves using a medical imaging technique (fluoroscopic visualization) as finding the exact point to insert the pin is more challenging.
Fixing external devices to the arm is quite tricky due to the sensitive positions of nerves and blood vessels. When placing such devices on the upper arm, care must be taken to preserve a certain nerve (the axillary nerve) and not to breach far beyond the inner side. When placing pins into the upper arm bone, it is safe to target the bony parts around the elbow. When placing pins in the lower arm, certain nerves can be at risk, and this can be prevented by careful identification and palpation of these nerves before they run into the forearm.
Inserting pins into the bone known as the ulna, which is also easily felt under the skin, is possible along a ridge. Likewise, inserting pins into another bone in the forearm, the radius, is commonly done in the shaft or lower part of the bone because going towards the upper part risks injuring certain nerves. When placing these pins, a small surgical cut and dissection down to the bone is important to avoid risk to a certain nerve (the superficial radial nerve).
Why do People Need External Fixation Principles and Overview
Doctors and surgeons use a method known as external fixation in bone and muscle-related treatments, including accident-related injuries, children’s bone issues, and reconstructive surgery. They attach a system of rods and pins outside the body to treat various issues. Here are a few reasons why they might use external fixation devices:
- For unstable pelvic injuries: If the ring of bones at the base of your spine is injured and unstable, a fixator can help keep things in place while you heal.
- In case of complicated bone fractures near joints: A complex fracture, where a bone (like the thigh bone, shin bone, or arm bones) breaks into many pieces near a joint, may need external fixation.
- When there’s lots of swelling around a broken bone: Sometimes, a fracture can cause a lot of soft tissue swelling. In such cases, a fixator can help while the swelling goes down.
- If the patient is very weak or can’t have an open surgery: Sometimes, if a person’s body can’t manage a major surgery, doctors use fixators as a safer option.
- For broken long bones that are shattered into many pieces: If a large bone like the femur (thigh bone) or tibia (shin bone) gets broken into many pieces, fixators can hold it together while it heals.
- Fractures where a lot of bone is lost: If a fracture results in a big loss of bone material, a fixator can fill the gap while your body grows new bone.
- If there’s open fractures with lost skin and muscle: In cases where the skin and muscles around a break are severely damaged or destroyed, fixators can help stabilize the area.
- To correct deformed limbs or lengthen them: Doctors can use fixators in a technique to gradually straighten a deformed limb or make it longer.
- If there’s bone loss due to a bone infection: A severe bone infection (called osteomyelitis) can destroy parts of a bone. Fixators can help the body rebuild the lost bone.
- For joint stabilization after skin or muscle reconstruction: If a joint needs to be immobilized after surgery to replace lost or damaged skin or muscle, a fixator can hold it steady.
- For joint fusion (arthrodesis): Sometimes, painful joints can be relieved by fusing them together – making them into one solid bone. Fixators can help with this process.
- In case of nonunion or malunion: A bone may not heal (nonunion), or it may heal in the wrong shape (malunion). Fixators can help correct these problems.
- Infections: If a bone or joint is infected, a fixator can help stabilize the area while it’s being treated.
- To help align a fractured bone during surgery: Sometimes, fixators are used during surgery to pull on a broken bone and get it into the right position.
When a Person Should Avoid External Fixation Principles and Overview
External fixation is a type of surgery that’s considered quite safe and minimally invasive. This means it only requires small cuts rather than large ones. It can greatly help a patient when used in the right situation. There are only a few reasons why this surgery might not be a good choice for someone.
Obese patients might have a higher risk because it might be hard to place the small rods, or ‘pins,’ used in the surgery safely. Also, a patient who is less likely to follow doctors’ orders is a concern because they might not return to have the device removed as required. In some cases, fractures around a prosthetic can make it difficult to find enough healthy bone to use for placing the pins.
Overall, the general reasons a patient might not have this surgery include if they refuse to have it, or if they are physically unable to undergo the procedure.
Equipment used for External Fixation Principles and Overview
The following items are needed for a typical procedure using a device called a uniplanar external fixation. This device, applied to the outside of the body, is used to stabilize bone fractures. The specific size of some tools will depend on both the kind of device used and the bone in question.
* 15-blade scalpel: This is a sharp, small knife used for making incisions, or cuts, on the body.
* Dissection scissors: These scissors are often used to separate or cut through tissues.
* Soft tissue retractors: These tools are used to gently move aside or hold back soft body tissues, giving doctors a clear view of the operation area.
* Size-specific trocar with soft tissue protectant sleeve: A trocar is a pointy tool enclosed in a tube (sleeve) to protect the surrounding tissues. The size of the trocar fits the bone and the device used.
* Corresponding drill bit: This is a piece that fits onto a drill, used to create holes in the bone. The specific size of the drill bit will match the device and the bone being operated on.
* T-handle wrench: This tool helps tighten or loosen items during the procedure.
* Tapping drill: This special type of drill is used to create threads in the holes made in the bone, which allows the pins to be screwed in securely.
* Corresponding size pins: These are rod-like structures that go into the drilled holes to help stabilize the bone. Their size matches that of the drill bit used.
* Bars and clamps: These hold the device in place on the outside of the body, connecting the pins in such a way as to stabilize the bone from outside.
* C-arm fluoroscopy: This is a special type of X-ray machine, which allows the surgeon to view the bone and the device in real time during the procedure, ensuring accurate placement.
How is External Fixation Principles and Overview performed
External fixation is a surgical technique used to stabilize broken bones. This technique is applied in the same way across different bones in the body. The essential step in this process involves inserting a pin into the bone through the skin. It’s crucial that the pin doesn’t pull on the skin or muscle during this process, as this could lead to swelling and infections. A tool like the Penfield-type retractors can be used to separate the bone from the outer layer covering the bone (called periosteum). To avoid trapping tissue, a sharp pointed instrument along with a drill is pushed to the bone. Keeping the drill centered on the bone ensures it goes through the near and far part of the bone. To avoid damaging the bone due to high temperature, plenty of liquid is used while drilling. Some pins are designed to drill on their own, which eliminates the need for the pre-drilling process. However, a study showed that these pins might not be as secure as the ones that require pre-drilling.
In cases of injuries to the pelvis, external fixation is frequently used. The pin can be inserted in two main locations: the iliac wing (large, flat part of the pelvis) and the anterior inferior iliac spine (part of the hip bone). The pins can usually be inserted quickly by experienced doctors and may sometimes require the use of an imaging technique called fluoroscopy. Another pin location, supracetabular pins, are positioned in a dense bone and provide better control of the pelvis. But these require careful placement with the help of fluoroscopy. The external fixator can also be fixed to the back of your pelvis using a device called a C-clamp. This placement should be done with caution as it could potentially over-compress and damage sacral nerves (nerves in your lower back).
For injuries in the upper extremity like the forearm, 3 or 4 mm screws work best for the ulna bone. Care must be taken to avoid damaging the nearby nerves when inserting pins into the radius bone. In some cases, external fixation can be used for broken bones in the arm (humerus), especially in obese patients or when there’s a severe injury. The nerves around the area where the pins are placed must be avoided to prevent damage.
For the lower extremity injuries, external fixation can also be applied to stabilize the femur (thigh bone). Pins can be placed directly on the side or towards the front and side of the femur. Similarly, these pins can be used along with pins on the tibia (shin bone) for better stabilization. Care must be taken to avoid damaging nearby blood vessels and nerves when placing pins on the lower part of the tibia.
After surgery, it’s important to properly care for the pin insertion sites to avoid infections. There are different methods for this, but no specific method has been proven to be superior. In some cases, the pin sites are wrapped with gauze soaked in iodine or other medicines. Reducing movement around the pin can decrease the risk of infection. Sometimes, daily pin care isn’t necessary as long as the patient maintains good hygiene. If there’s skin drainage or redness around the pins, cleaning the pin sites three times a day is advised until the infection clears.
Possible Complications of External Fixation Principles and Overview
Here are some problems that can happen with a procedure called external fixation, which is a type of surgery to fix broken bones:
* Pin site infection: This is when the area where the surgical pin is inserted gets infected.
* Osteomyelitis: This is a severe infection that affects the bone.
* Frame or pin/wire failure or loosening: The frames, pins, or wires used in the procedure could break or come loose.
* Malunion: This is when the broken bone heals incorrectly.
* Non-union: This is when the broken bone doesn’t heal and remains separated.
* Soft-tissue impalement: This happens when the pins or wires accidentally pierce or get stuck in the soft tissue of your body.
* Neurovascular injury: This type of injury affects the nerves and blood vessels.
* Compartment syndrome: This is a serious condition that involves increased pressure in a muscle compartment. It can lead to severe muscle and nerve damage if not treated quickly.
* Refracture around pin: This is when the bone breaks again around the area of inserted pin.
What Else Should I Know About External Fixation Principles and Overview?
External fixation is a technique used in treating broken bones. It not only helps to temporarily hold the broken bones in place but can also offer a permanent solution. It’s particularly useful in severe injury cases where immediate control of damage is required.
This method is quicker and less invasive than some other treatments, leading to less blood loss. Plus, this technique allows more time for swelling in the affected area to go down. As a result, it reduces the chances of further problems like infections and complications with the wound. So, it can be a very effective way of managing fractures, particularly in serious injuries.