Comparing External Fixation to Internal Lengthening

Before the introduction of the modern limb lengthening technology, our only option for leg lengthening involved the use of an external fixator or ex-fix, which involves scaffolding of sorts around the leg and pins attaching it to each side of the bone. Patients must manually crank the device daily to spread the bone further and allow the body to lay new bone within the gap.

An internal solution was developed to address many of the common concerns associated with an external fixator. Known as an intramedullary nail, we can now perform the lengthening from the inside out. Just as external fixation is a tried-and-true solution, the internal option has also been proven successful, with about 15,000 implants (trauma and deformity procedures included) performed since its inception.

As a leading trauma surgeon in Southern California, Dr. Basmajian has used both technologies to correct deformities and even handle complex trauma cases. Ultimately, deciding to use one device versus the other is a discussion that patients will have with Dr. Basmajian during consultation. For now, we will quickly discuss the benefits of each option so that you can begin to formulate an opinion on which direction may be best for you.

Cosmetic Considerations

The limb lengthening process is relatively long, and many patients value discretion. An external fixator is obvious and cannot be hidden from sight. This is a dealbreaker for many patients who wish to maintain the confidentiality of their procedure. On the other hand, the intramedullary nail or internal lengthening device is completely invisible once implanted, and no one needs to know that the patient is having lengthening surgery.

Similarly, the external fixator necessarily requires obvious scars. The external fixator is attached to the bone using pins passing through the skin along the tibia and the femur. When wearing shorts, these scars will be more evident for some time after surgery or potentially permanently. On the other hand, the intramedullary nail allows strategic placement of the incisions to reduce visible scarring.

However, there is a significant tradeoff – mobility.

While cosmetically, the intramedullary rod is preferable, it requires that the patient not put any weight on the leg until the lengthening is complete and the bone has hardened. While this was addressed with a newer generation nail (Precice Stryde) that allowed for weight-bearing during the process, this nail was recalled and remains off the market until the manufacturer can address the biocompatibility concerns of the recall. We expect that this will occur sometime in early 2023.

Under and Overcorrection

We found that without rigid compliance, external fixation patients may under or over-lengthen the leg requiring surgical correction. For example, cranking too slowly can cause the bone to fuse prematurely and lose additional lengthening potential. Cranking it too quickly could cause a nonunion of the bone, essentially not allowing the gap to be filled with new bone and once again requiring corrective surgery. This is far less of a concern with the intramedullary nail, as the lengthening process is controlled using magnetic technology and precise electronic guidance.

Infection and Complications

Older external fixation technology is more prone to infection as there are more wounds, and each wound needs to be appropriately maintained throughout the process. Internal options also have the potential for infection. However, this is typically far less of a concern. A 2018 study1 showed that about 18% of patients using internal lengthening experienced a complication after surgery, while about 45% of external fixation patients did.

When it comes to complications, choosing a surgeon and practice with extensive experience and lengthening is key to minimizing these numbers. Complication numbers are very subjective and are often skewed higher due to poor technique, lack of surgical expertise, patient noncompliance, and non-ideal patient selection. Therefore, we are diligent with our preoperative workup and patient instructions.

Pain Levels

Data and anecdotal evidence have shown that the postoperative pain associated with the internal lengthening systems is lower than that of external fixation. However, it is essential to remember that pain is somewhat subjective, with different patients having varying pain thresholds. In all cases, between the long-lasting local anesthetic we use after the procedure as well as proper pain management in the early postoperative period, most patients report acceptable pain levels regardless of the procedure.

Length Discrepancy

While both internal and external solutions show excellent results post-treatment, data shows that internal lengthening resulted in a smaller limb length discrepancy of .3 mm versus external fixation, which resulted in an average of 3.6 mm of discrepancy. While this may not seem significant, patients can often feel the difference even if it is not obvious to passersby.

Resources:

¹Fragomen AT, Kurtz AM, Barclay JR, Nguyen J, Rozbruch SR. A Comparison of Femoral Lengthening Methods Favors the Magnetic Internal Lengthening Nail When Compared with Lengthening Over a Nail. HSS J. 2018 Jul;14(2):166-176. doi: 10.1007/s11420-017-9596-y. Epub 2018 Jan 5. PMID: 29983659; PMCID: PMC6031532.