Limb lengthening surgery can correct significant leg length differences and, in selected cases, increase bone length for other reconstructive or stature-related goals. However, it is a complex treatment that involves gradually separating a surgically divided bone while the body forms new bone in the gap.
Because the bone is being lengthened over time, the surrounding muscles, tendons, nerves, blood vessels and joints must also adapt. This makes complications possible even when the procedure is carefully planned and performed.
Some problems are temporary and can be managed by adjusting the lengthening rate, physical therapy or medication. Others may require an additional procedure, and a small number can have lasting effects.
Understanding these risks is an important part of deciding whether limb lengthening is appropriate. You can learn more about the procedure and its overall treatment process on the Limb Lengthening Surgery page.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
What Are the Main Risks of Limb Lengthening Surgery?
The risks vary according to the technique used, the bone being lengthened, the amount of lengthening planned, the patient's health and the reason for surgery.
Possible complications include:
- Infection
- Delayed bone healing
- Failure of the new bone to unite properly
- Joint stiffness or contracture
- Muscle and tendon tightness
- Nerve irritation or injury
- Blood vessel problems
- Changes in bone alignment
- Problems with the lengthening device
- Fracture or weakness of the newly formed bone
- Pain and prolonged discomfort
- Need for additional surgery
Not every patient experiences these problems, and their likelihood varies substantially between different treatment methods and clinical situations.
1. Infection
Infection is one of the most recognised complications of limb lengthening, particularly when an external fixator is used. External fixation involves pins or wires passing through the skin and into the bone. The areas around these pin sites can become irritated or infected during treatment.
Many superficial infections can be managed with local care and antibiotics, but deeper infections can be more serious and may require additional treatment.
Internal lengthening nails avoid exposed pin sites, which can reduce some of the infection-related problems associated with external fixation. However, an internal implant does not eliminate the possibility of infection.
2. Delayed Bone Healing or Nonunion
The purpose of distraction osteogenesis is to encourage new bone to form gradually between the separated bone segments. Sometimes the regenerate bone does not develop or mature as expected.
This may result in delayed union, meaning the new bone takes longer than expected to become sufficiently strong. In more difficult cases, the bone may fail to unite properly, known as nonunion.
Management depends on the underlying problem and may include slowing or temporarily stopping distraction, modifying weight-bearing, changing the treatment approach or performing another procedure. Bone grafting or revision surgery may be required in some cases.
3. Premature Bone Healing
The opposite problem can also occur. If new bone forms too quickly, the gap may begin to close before the planned amount of lengthening has been achieved.
This is known as premature consolidation. If the new bone becomes too mature to continue distraction effectively, the treatment plan may need to be modified and an additional procedure may sometimes be necessary.
4. Muscle Tightness and Joint Contractures
As the bone becomes longer, the surrounding muscles and tendons are placed under increasing tension. They do not always lengthen at exactly the same rate as the bone.
This can cause muscle tightness, reduced flexibility and stiffness around nearby joints. In more significant cases, a joint can become fixed in an abnormal position, known as a contracture.
The hip, knee and ankle may be affected depending on which bone is being lengthened. Regular physical therapy, stretching, strengthening exercises and close monitoring of joint movement are therefore important parts of treatment.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
5. Nerve Problems
Nerves also have to adapt as the limb gradually becomes longer. Excessive tension or compression can cause symptoms such as tingling, numbness, altered sensation or weakness.
Nerve problems may improve when the distraction rate is reduced or treatment is modified. However, significant nerve injury can require additional intervention and, in some cases, may result in persistent symptoms.
New numbness, weakness or other neurological symptoms during lengthening should therefore be reported promptly rather than ignored as a normal part of recovery.
6. Blood Vessel and Circulation Problems
Blood vessels are also affected by the gradual change in limb length. Although serious vascular complications are uncommon, stretching or compression of a vessel can interfere with circulation.
Symptoms such as unusual swelling, changes in skin colour or temperature, severe pain, or other sudden changes in the limb require urgent medical assessment.
7. Problems With the Newly Formed Bone
The new bone, often called the regenerate, must gradually become strong enough to support the limb. Several problems can occur during this process. The regenerate may be weak, develop an abnormal shape, mature too slowly or, less commonly, consolidate too quickly.
If the new bone remains weak after the lengthening phase, the risk of fracture can increase. Regular imaging helps the surgical team assess how the regenerate is developing and determine whether the treatment schedule needs to be adjusted.
8. Bone or Joint Alignment Problems
Limb lengthening is not simply a matter of creating a gap between two bone segments. The segments also need to remain appropriately aligned as the bone is gradually distracted.
Changes in alignment can result in angular deformity, rotation or problems with the position of a nearby joint. Careful planning and repeated imaging are used to identify these changes early.
Some alignment problems can be corrected during treatment, while more significant deformities may require another procedure.
9. Problems With the Lengthening Device
The type of device used can influence the complications a patient may encounter. External fixators can develop problems involving pins, wires, frame components or alignment.
Internal motorised lengthening nails avoid an external frame but introduce implant-specific risks, including mechanical failure or problems with the telescopic lengthening mechanism.
A recent systematic review of externally controlled motorised lengthening nails reported mechanism-related failures in about 4.3% of 2,495 nails across 29 studies. Most reported failures required surgical intervention, although the majority of cases with available outcome data still achieved the intended reconstruction after management.
These figures apply to specific implant systems and should not be interpreted as the risk for every limb lengthening procedure.
10. Pain and Prolonged Discomfort
Pain is expected to some degree after surgery and during the lengthening process. As the bone and surrounding tissues gradually adapt, patients may experience discomfort, muscle tightness or difficulty sleeping.
Persistent or increasing pain, however, should not automatically be considered normal. It can sometimes indicate excessive soft-tissue tension, nerve irritation, infection, problems with the regenerate or another complication.
11. Blood Clots and Other General Surgical Risks
As with other major lower-limb operations, there can be general surgical risks such as blood clots, bleeding, anaesthetic complications and reduced mobility-related problems.
The risk of venous thromboembolism can be influenced by the patient's health, mobility and other individual factors. Preventive measures are therefore considered as part of the overall treatment plan.
Can Limb Lengthening Cause Permanent Problems?
Most patients do not experience every complication listed above, and many problems can be identified and treated before they become permanent. However, limb lengthening can occasionally result in lasting complications.
Potential long-term problems may include persistent nerve symptoms, joint stiffness, deformity, chronic infection, problems with bone healing or lasting functional limitations.
The risk of a permanent problem is influenced by the patient's condition, the amount and rate of lengthening, the technique used, the occurrence of complications during treatment and how quickly those complications are addressed.
Does the Amount of Lengthening Affect the Risk?
It can. Larger amounts of lengthening place greater demands on the muscles, tendons, nerves and joints surrounding the bone.
Research has also suggested that complications become more likely as the amount of lengthening increases relative to the original bone length. This is why a target is not selected simply according to how many centimetres a patient would like to gain.
The surgical team considers the original bone length, soft-tissue flexibility, joint movement, bone quality and the patient's overall treatment goals when determining an appropriate target.
Are Internal Lengthening Nails Safer Than External Fixators?
Neither technique is completely risk-free, and the complication profile is different.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
| Internal lengthening nails | External fixators |
|---|---|
| No external frame or exposed fixation pins | Uses pins or wires connected to an external frame |
| Can reduce some pin-site and external-frame problems | Pin-site infections are a recognised complication |
| Can have implant-specific mechanical complications | Can have frame, wire or pin-related complications |
| May require surgery if the implant malfunctions | May require additional procedures for alignment, infection or bone-healing problems |
Comparative research has not established one technique as universally appropriate for every patient. The choice depends on factors such as the bone involved, the amount of correction required, previous surgery, bone and soft-tissue conditions, and the surgeon's treatment strategy.
What Can Patients Do to Reduce the Risk of Complications?
Not every complication can be prevented, but following the treatment plan carefully can help reduce avoidable problems.
- Attend scheduled imaging and follow-up appointments.
- Follow the prescribed distraction schedule rather than changing it independently.
- Complete physical therapy and recommended stretching exercises.
- Follow weight-bearing restrictions carefully.
- Maintain appropriate nutrition to support bone healing.
- Follow pin-site or wound-care instructions when applicable.
- Report new pain, swelling, numbness, weakness, fever or changes around the surgical site promptly.
Early recognition is particularly important because some complications can be managed more effectively when they are identified before they become advanced.
The Bottom Line
Limb lengthening surgery can provide meaningful correction, but it is not a simple procedure and complications are possible at different stages of treatment. Infection, delayed or abnormal bone healing, muscle tightness, joint stiffness, nerve symptoms, alignment problems and device-related complications are among the risks that need to be considered.
The likelihood of complications depends on the technique, the amount of lengthening, the patient's anatomy and health, and how the limb responds during treatment. Regular imaging, physical therapy, adherence to the treatment plan and early reporting of new symptoms are important for identifying problems before they become more serious.
The goal of successful limb lengthening is therefore not simply to achieve the planned increase in bone length, but to do so while preserving bone healing, joint movement, nerve function and overall limb function.
