Internal vs. External Fixation Devices – Everything You Need To Know

The debate of internal vs. external fixation mainly comes down to affordability and convenience. Both internal and external fixation devices have fixed fractures, congenital deformities, and limb length discrepancies for ages. Today, they’re helpful in cosmetic height surgery, and both methods have their different purposes and advantages.

Keep reading if you’re curious to see how each device fits into the broader world of orthopedics.

What is an External Fixator & How is it Used?

The critical feature of external fixators is the hardware that’s attached to the outside of the limbs. This outer part can consist of a single metal bar or multiple rings, and these bars or rings connect to the muscles and bones through threaded pins and wires.

The pins and wires in external fixators hold the bone in place so fractures can heal. In the case of fixing limb length discrepancies or cosmetic height surgery, the patient can move these wires with external knobs or screws to pull the bone apart gradually.

Types of External Fixators

External fixators range from single metal bars to complex rings attached with rods and can even be combined with internal fixators to make them more convenient to use.

Fully External

Entirely external fixators can come as a single metal rod or consecutive rings around the arms or legs. In both cases, metal pins or wires pass through muscle and bone and attach to the rod or rings outside.

These devices generally fix acute fractures or correct limb length discrepancies, though external fixation also plays a role in limb lengthening since 1951, at the dawn of the Ilizarov apparatus.

Combined Internal Nail and External Fixator

Lengthening Over Nail (LON) and Lengthening and Then Nailing (LATN) are two methods combining internal nails and external fixators so that removal of the fixators is possible earlier than purely external methods.

Doctors primarily use both methods for cosmetic limb lengthening. They’re incredibly convenient when healing fractures or fixing deformities in bones that can’t fit thicker intramedullary nails like PRECICE or STRYDE.

During LON, the surgeon inserts a nail of small diameter inside the bone. Wires are then threaded through the muscle and the bone and connect to the external fixator, which generally consists of two or three rings.

With LATN, the nail is inserted into the bone once lengthening completes and remains inside until it’s fully healed.[1]

In either case, the surgeon removes the external fixator can as soon as the bone fully lengthens.

Devices Used

There are mainly three devices used for external fixation in combination with pins, wires, and screws.

Monolateral Rail

A monolateral rail or monorail external fixator consists of a metal rod with metal pins attached to it. These metal pins connect to a distraction rod. The surgeon attaches the pins to the concerned bone after making a small incision. A knob on the outer part then turns to extend the divided bone.[2]

This device primarily finds use in fixing wrist or distal radius fractures, limb length discrepancies, and deformity correction. It needs to be left in place until the bone fully hardens. Cosmetically, it’s found use in arm lengthening surgery, being successfully able to lengthen the humerus or upper arm bone by up to 9 cm.[3]

Ilizarov Apparatus

The Ilizarov apparatus is the most common circular external fixator, and it holds wires in place for healing fractures and fixing congenital deformities. It’s also prominently used in both the LON and LATN methods of limb lengthening.

Ilizarov consists of two or three rings attached by rods and to the bone by metal wires threaded through the muscle. It’s the oldest device for cosmetic height surgery. The patient can manually turn the screws on the outside to move the wires, and hence, the bone fragments apart.

Taylor Spatial Frame (TSF)

The TSF is a redesign of the Ilizarov, which consists of four carbon fiber rings connected by six struts. These struts attach to the bone by wires, like Ilizarov.

Each strut lengthens independently, enabling manipulation of the bone in three dimensions. The TSF can exclusively alter the angle, rotation, spatial position, and length of the bone.

This device generally heals bone misalignment or malunions when fractured bones don’t heal appropriately at the point where they broke.

Benefits

Since external fixation devices are less convenient than internal ones, they tend to be much more affordable. This affordability is a significant factor for people looking to treat a limb deformity over a long time or for cosmetic limb lengthening. Both of these procedures are costly and involve additional expenses related to physical therapy etc.

Downsides and Risks

External fixators are cumbersome, often getting in the way of everyday activities like work or intimacy. Though LON and LATN reduce the time patients need to wear them, they can still be quite an inconvenience.

Pin site infections – infections caused where the metal wire enters the skin – are also a risk with external fixators but can be treated with antibiotics.

Recovery

Recovery for fractures varies depending on the affected bone. With limb lengthening, healing can take anywhere from a couple of months to a year.

Most limb lengthening patients won’t walk when using external methods as these aren’t weight-bearing. Moreover, if an Ilizarov apparatus is used instead of LON or LATN, patients will have to wear the external fixator until the bone fully heals, making it quite the hassle to get through.

What is an Internal Fixator and How is it Used?

Internal fixators don’t need to be supported by external hardware at any stage of the process. These generally attach directly to the surface of the bone or are placed inside the bone itself.

When it comes to limb lengthening, the surgeon performs a corrective osteotomy by incising the outer layer to divide the bone into two. An internal fixator can lengthen it, and an external remote controller tells the device to extend the bone.

Types of Internal Fixation

There are countless internal fixation devices for every purpose, from fixing broken bones to correcting limb deformities. They range from small devices like wires and plates to invasive, heavy ones like nails.

Plates

Surgeons usually use plates to heal fractures. The first step is to align the broken bone, after which they attach a plate to the outside to hold it in place and allow it to heal.

Plates such as the PRECICE Plate also lend themselves to limb lengthening, usually in pediatric patients. Once the bone is cut and implanted (has a plate attached to it), a remote controller slowly moves the two sides of the plate apart. This method can safely lengthen up to 6.5 cm.[4]

Screws

If there’s a broken bone, chances are the doctor will heal it with screws. Screws are by far the most common method to heal fractures, and these are not just used alone but also in combination with plates, rods, and nails to treat different kinds of fractures.[5]

A screw holds together pieces of broken bone to allow for consolidation. When combined with nails, screws can even fix misalignments and malunions (improperly healed fractures).

Wires and Pins

Wires and pins are thin, smooth rods usually made of stainless steel, and they have a hook at the end and can thread through the skin and muscle into the bone. They’re the saviors of smaller bones like those in the hands and feet.[5]

The surgeon fixes the wire by hanging an anchor or traction from the other end – something with a slight weight to keep the wire taut. These devices are usually a temporary fix before applying a more permanent method but can form part of permanent methods like the Ilizarov apparatus.

Nails and Rods

Gerhard Küntscher first treated fractures with intramedullary nails in World War 2. The medullary cavity is the cavity in the central part of the bone containing the bone marrow. Since the surgeon inserts these nails into this medullary cavity, they’re called intramedullary nails.

These nails are made of titanium or stainless steel and tend to be weight-bearing, allowing for much faster recovery than other internal fixators. With limb lengthening, the surgeon cuts the outer layer of the bone in two before inserting the nail. An external remote controller then controls the elongation with the help of a magnet inside the nail.

The doctor will only remove the nail once the bone fully heals.

Devices Used

Weight-bearing internal fixation devices are usually intramedullary nails inserted into the bone, and the main difference between these is their material. Other nails like Intramedullary Skeletal Kinetic Distractor (ISKD), the Fitbone, and the Guichet Nail are also used but have become outdated.

Dr. Dror Paley of the Paley Orthopedic and Spine Institute developed both PRECICE and STRYDE, and an external remote controller controls both, but their weight-bearing capacity varies. They’re both used for correcting limb discrepancies as well as cosmetic limb lengthening.

PRECICE

The PRECICE nail, the latest version being PRECICE 2.2, is made of titanium and can provide a total height gain of 14.5 cm, tibia (calf) and femur (thigh) combined.[6] However, this nail can’t fully bear weight, and patients will have to use crutches and wheelchairs to get around.

PRECICE costs less than STRYDE, though, and is currently available on the US and UK markets, so it’s a better option than external fixators for those who can’t afford STRYDE.

STRYDE

STRYDE works the same as PRECICE but is made of stainless steel and is fully weight-bearing.[7] Though patients may have to use crutches at the very beginning of their journey, they should be able to walk only a few days after surgery.

This nail is currently recalled in the US and UK and is more expensive than PRECICE, but it should be back by 2022.[8] The wait may be worth it for those who can afford it.

Benefits

Internal fixators are much more convenient and easier to get around with than external ones. They’re practically invisible apart from the scars and have a much lower chance of fractures since they tend to provide the bone with more stability and strength as it heals.

Downsides and Risks

The main downside of internal fixators is the high cost. At the Paley Institute, STRYDE lengthening can cost anywhere between $97,500 to $280,000 depending on the bones lengthened.[9] It’s also unknown what effects of leaving the nails inside the body long-term may be, so doctors recommend getting them removed once the bone heals.

Recovery

Recovery is faster with internal fixators since the bone heals over the nail. With STRYDE, patients can also walk while it remains inside the body, so the post-recovery period is much easier. Limb lengthening can take up to a year to heal, but physical therapy is smoother without a cumbersome external device.

Internal vs. External Fixation – Which is Better?

There’s no clear answer as to whether internal or external fixation is better. The best option can vary depending on the fracture site, the type of deformity, the patient’s budget, desired height increase or the extent of limb length discrepancy. Only a doctor can advise which device would be best for you.

For limb lengthening, the choice comes down to the patient’s budget, and the higher the budget, the better chance the patient can use PRECICE or STRYDE, which means more comfort during the lengthening process. However, most methods of limb lengthening are nearly 100% successful with a qualified and experienced doctor.[10]

References

[1] Rozbruch, S. R., & Blyakher, A. (n.d.). Abstract: Lengthening and Then Nailing (LATN) of the Tibia [PDF]. https://www.hss.edu/files/LL-Abstract-Lengthening-Then-Nailing-Tibia.pdf

[2] SickKids. (n.d.). Limb lengthening and reconstruction: Monolateral rail. AboutKidsHealth. https://www.aboutkidshealth.ca/article?contentid=2544&language=english

[3] Agrawal, H. K., Singh, B., Garg, M., Khatkar, V., Batra, S., & Sharma, V. K. (2015, June). Cosmetic arm lengthening with monorail fixator. Chinese Journal of Traumatology, 18(3), 170-174. https://www.sciencedirect.com/science/article/pii/S1008127515000826

[4] Kulkarni, R., Singh, N., Kulkarni, G. S., Kulkarni, M., Kulkarni, S., & Kulkarni, V. (2012, May-June). Limb lengthening over plate. Indian Journal of Orthopaedics, 46(3), 339-345. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3377147/

[5] OrthoInfo. (2019, April 22). Internal Fixation for Fractures. OrthoInfo. https://orthoinfo.aaos.org/en/treatment/internal-fixation-for-fractures/

[6] Paley Orthopedic & Spine Institute. (2015, September 26). The PRECICE. Paley Orthopedic & Spine Institute. https://paleyinstitute.org/centers-of-excellence/stature-lengthening/the-precice/#/

[7] Robbins, C., & Paley, D. (n.d.). Stryde Weight-bearing Internal Lengthening Nail. Techniques in Orthopaedics, 35(3), 201-208. https://paleyinstitute.org/wp-content/uploads/Stryde-Weight-bearing-Internal-Lengthening-Nail.pdf

[8] Cyborg 4 Life. (2021, March 15). NuVasive Voluntary STRYDE Nail & Biodur Device Recall – Dr. Dror Paley Limb Lengthening Interview [Video]. YouTube. https://www.youtube.com/watch?v=qBQKYz2gFqw&ab_channel=Cyborg4Life

[9] Paley Orthopedic & Spine Institute. (2015, September 26). Costs & Financial Considerations. Paley Orthopedic & Spine Institute. https://paleyinstitute.org/centers-of-excellence/stature-lengthening/costs-financial-considerations/#/

[10] Rozbruch, S. R. (2020, April 28). Limb Lengthening – An Overview. HSS. https://www.hss.edu/conditions_limb-lengthening-overview.asp