Leg shortening can be congenital or caused by injury, infection or other acquired conditions. Leg shortening of more than 2 cm often leads to complaints: The unequal length of the legs results in a misalignment of the pelvis. This causes the spine to become curved. The result is pain and premature wear and tear of the hips and lower spine.
There are shoe elevations or specially made shoes that are designed to compensate for the shortening. However, these are not a helpful solution for most patients.
Callus distraction is a procedure to artificially lengthen bones. Doctors perform it in cases of shortening or axial misalignment of a limb as well as for long bone defects. Even long-distance lengthening of the upper or lower leg bones is possible.
The following complications often occur with the usual treatment with an external fixator:
- Wires can lead to painful infections at entry points, which can also affect bones and joints. The wires, which pierce the skin, muscles and tendons, significantly restrict the mobility of the joints.
- After removal of the external fixator, the newly formed callus tissue can bend, shorten or even break.
- The external fixator is worn for a relatively long time, between 6 and 12 months. This delays rehabilitation and return to work.
- Experience has shown that the bulky fixator places a considerable physical and psychological burden on the patient. Experts have therefore been researching for decades how to lengthen the leg with an internal implant.
The external fixator is a method of correcting leg length discrepancies @ Ольга Альперович /AdobeStock
The Intramedullary Skeletal Kinetic Distractor (ISKD nail) is a modern lengthening nail that avoids the complications of the external fixator. It lengthens mechanically by rotational movements of at least 3° in the area of the severed, lengthening bone.
The ISKD nail consists of a narrow lower and a wider upper nail section. They can be slid into each other and are connected via ratchet mechanisms. The ratchet mechanism is activated when the upper and lower nail sections are rotated by 3° or more. This lengthens the nail slightly.
The mechanism in the nail works in such a way that if the patient turns it a little, the nail automatically becomes longer. The patient must turn the nail 160 times by 3 degrees to lengthen the nail by 1 millimeter.
This rotation already happens when the patient puts some weight on the leg or moves it after the operation, and there is a magnet in the nail. This changes direction when the patient turns the nail. A small monitor measures this process. The monitor shows the daily and total lengthening distance.
If the lengthening is insufficient, the patient can move the leg more in order to achieve the desired lengthening distance.
This also works in reverse. If the extension is excessive, the patient should reduce the load and movement for a short time.
Adult patients can achieve a lengthening of the upper or lower leg of between 2 and 8 cm with the ISKD nail.
A precise clinical and radiological examination is necessary before surgery. Doctors analyze the differences in leg length and possible deformities.
The doctor uses a wooden board to simulate a leg lengthening. He examines whether the misalignment of the hip joints and spine can be corrected.
In addition, a clinical examination of the range of motion and stability of the joints is carried out.
The doctor uses X-ray examinations of the leg axes to detect axial deviations and uses computer tomography to measure the difference in leg length with millimeter precision.
Regular X-ray images are an essential part of the treatment @ H_Ko /AdobeStockThe operation takes 2 to 3 hours. On the following day, the patient is given crutches so that they can put some weight on the operated leg.
The duration of inpatient treatment is approximately 7 days. After discharge from hospital, the patient should attend regular check-ups. During the follow-up examinations, doctors check the extent of the lengthening and joint mobility.
The lengthening of the leg is 1 mm per day. Healing of the extended bone usually takes 2 to 3 days per mm.
With a leg lengthening of 4 cm, a bone healing period of around 4 to 5 months can therefore be expected. Full weight-bearing is possible a few weeks after the lengthening is completed.
Doctors usually perform the procedure under spinal anesthesia. A pain catheter is useful in the first few days after the operation. At the patient's request, doctors can also perform the procedure under general anesthesia.
During bone lengthening, the surrounding soft tissues (muscles, ligaments and tendons) are stretched. The soft tissue tension can be painful. Patients are therefore usually given painkillers.
The patient makes the rotational movements required for the lengthening shortly after the operation. If these are not sufficient, targeted rotational movements are made to activate the lengthening mechanism. The patient is given painkillers for this process.
In addition, the doctor routinely administers antithrombotic injections into the subcutaneous fatty tissue.
Shortly after the operation, the patient is given physiotherapy instructions to help them mobilize their leg quickly. A movement splint and forearm supports are used to help with this. The patient also receives a manual explaining how the nail works.
An external monitor measures the lengthening of the nail. If the lengthening is insufficient, the patient can help with targeted rotational movements. If there is excessive lengthening, the patient should reduce the load for a short time.
After discharge from hospital, outpatient check-ups are initially carried out every 1 to 2 weeks. Once the desired lengthening distance has been reached and radiological evidence of incipient bone formation can be seen, the patient can switch to full weight-bearing.
The patient also practises the mobility of the adjacent joints through physiotherapy exercises. The time at which the patient is able to work depends on their occupation. Sedentary activities are possible a few weeks after completion of the lengthening procedure.
The nail is not suitable for children and adolescents with growth plates that are still open. The nail would damage the growth plates.
In some patients, an excessively narrow or deformed bone marrow space makes it difficult to insert a straight lengthening nail.
In patients who have had a bone infection in the past, doctors critically examine whether to carry out treatment with an extension nail.
As the nail is completely in the bone, the problems and complications of an external fixator are avoided.
These include
- Infections
- Pain at the entry points of the wires
- Severe movement restrictions
- Bone bending
- Delayed rehabilitation
- Low treatment comfort
Leg lengthening should only be performed by experienced centers. Compared to an external fixator, the complications are significantly lower.
However, the general surgical risks also apply here:
- Infections
- Injuries to nerves and vessels
- Formation and spread of a blood clot (thrombosis/embolism)
The specific surgical risks of treatment with the ISKD lengthening nail include
- Premature bone healing (re-sectioning of the bone required)
- Excessively rapid lengthening (treatment by increased weight-bearing, possibly short-term application of a unilateral external fixator)
- Delayed or absent callus regeneration (treatment by insertion of autologous spongy bone from the iliac crest)
- Joint contractures (intensive physiotherapy, soft tissue surgery if necessary)
- Axis errors, leg length discrepancy (surgical correction if necessary)
When does the lengthening nail stop growing?
Doctors adjust the lengthening nail individually to the desired lengthening distance before implantation. Excessive, unwanted lengthening is not possible.
Can I do sports again with the lengthened leg?
As soon as the newly formed bone has fully grown through, you can do sports without any concerns.
Do I need another operation to remove the lengthening nail?
It is not necessary to remove the nail. Normally, only a single surgical procedure is necessary.
