Intro to Limb Lengthening
Printer-friendly versionMethods of Lengthening
Limb-Lengthening Process
Complications of Lengthening Surgery
Physical and Occupational Therapists
[ Please scroll down to view the entire webpage ]
Limb Lengthening: How Does It Work?
The limb lengthening process works by gradually growing new bone and soft tissues (skin, muscle, nerves, blood vessels, etc). This new growth is called tissue regeneration.
Bone and soft tissue regenerate when they are distracted (pulled apart) at a very slow rate of approximately 1 mm per day. If the rate of distraction is faster than this, bone may fail to form between the two ends of the bone that are being pulled apart. Then, soft tissues, such as muscle, may experience contracture (get too tight) or nerves may become paralyzed. If the rate of distraction is too slow, premature consolidation may occur (the bone may consolidate too soon), preventing the lengthening device from further pulling it apart.
There are many different lengthening devices used. The most common are external fixators, which are devices that attach to the bone by means of thin wires or thicker pins that have a screw threading at their attachment to the bone. There are also lengthening devices that are fully implanted inside the bone. These devices do not require external pins. The different devices are described separately.
There are two phases of lengthening until the bone is fully healed: the distraction phase and the consolidation phase. The distraction phase is the lengthening phase. After the desired length is obtained, the newly regenerated bone is still very weak because of lack of calcium within it. The hardening and calcification of this new bone is called the consolidation phase.
A variety of orthopedic devices are used to distract the bone and soft tissues. The decision regarding which device to use is an individualized one dependent upon the desired correction.
There are two general types of devices: external fixators and internal fixators. The external devices attach to the bone from outside the body by means of wires and threaded pins. The internal devices are implanted inside the body and lie on the bone or inside the marrow cavity of the bone.
The best known and most versatile techniques are with monolateral (one-sided or straight bar) external fixators (e.g., Orthofix, EBI) and circular external fixators (e.g., Ilizarov, TSF). External fixators are applicable to almost all cases. To shorten the time in the external fixator, a combination of the external fixator method with an internal nail to perform the lengthening over nail (LON) technique. However, this method is not applicable to all cases.
A fully implantable self-lengthening nail (ISKD) is also used. It has an internal mechanism that performs the lengthening and thereby eliminates the need for an external fixator. This method is available for certain cases.
External Fixation Alone
When only an external fixator is used, the fixator needs to remain in place for both the distraction and consolidation phases. If the fixator were removed at the end of the distraction phase, the new bone would collapse and reshorten. Therefore the external fixator needs to remain in place until the regenerated bone appears solid enough on the radiographs (x-rays). At that point, the device can be removed. Often, a cast is applied to temporarily protect the bone from breakage for an additional short time.
The total time in the external fixator can be estimated to be approximately 1 month for each centimeter lengthened in children and 1.5 to 2 months or longer per centimeter in adults.
Lengthening over Nail
Lengthening over Nail or LON was developed in order to decrease the external fixator treatment time, eliminate the need for post-removal casting, and decrease the risk of breakage of the new bone.
With LON, a metal rod is inserted into the bone along with the external fixator. The rod fits in the marrow cavity of the center of the bone, and the external fixator is applied around the peripheral part of the bone so that the external fixator pins do not come in contact with the metal rod. The bone is lengthened as described above.
After lengthening is completed, the patient goes back to the operating room for the insertion of special screws that lock the rod to the bone. With screws at both ends of the rod on opposite sides of the lengthening zone, the external fixator is no longer needed, and is removed during the same operation.
Therefore, the total external fixation treatment time is much shorter, and is equal to the distraction phase. This usually reduces external fixator time to less than half.
Fully Implantable Lengthening Nails and Prostheses
The most recent development is that of a fully implantable devices that can lengthen the limb from within.There is no need for an external fixator.This has many advantages, including no risk of pin infection, no muscle tethering by the pins, less pain, and better comfort. Unfortunately, this method is mostly limited to older children and adults. Therefore, many patients cannot be treated by this method.
1: Surgery
For lengthening and deformity correction, the bone is usually cut through a very small incision to minimize injury to tissue. After surgery, most patients remain in the hospital for 1 to 3 days. A more complex procedure may require a longer inpatient hospital stay.
Rehabilitation starts the day after surgery. Occupational therapists prepare special splints to support the hand or foot during treatment. Before discharge, all patients are taught to transfer from bed to chair to toilet, and to walk using crutches or a walker, if allowed. Before discharge patients are taught how to adjust their lengthening device to accomplish the necessary corrections of deformity or length. Patients are also taught how to care for pin sites in cases of external fixation.
2: Distraction Phase
Lengthening usually begins a few days or a week after surgery (latency period). With external fixation, this is done manually. The manual turns are performed by the patient or family. With implantable lengthening devices, the lengthening is performed either by small twists or pressure on the leg. Because bone is a living substance, when the bone ends are gradually distracted (pulled apart), new bone grows between the bone ends. The lengthening rate is usually 1 mm per day but may be slower or faster depending on the tolerance of the bone and soft tissues to the distraction process.
Most patients experience little pain during the day. Aching or difficulty sleeping at night is not unusual but is well controlled with medications as needed. This varies from patient to patient according to individual pain tolerance and the type of treatment being performed.
Physical therapy is required on an outpatient basis in all cases during the distraction phase. These sessions are designed to stretch muscles to help them grow and to maintain joint flexibility. In most cases, we allow partial or complete weight bearing as tolerated. Weight bearing actually stimulates the bone to grow, much in the same way stretching stimulates muscles and other soft tissues to grow. Most patients are allowed to shower and even to swim during the lengthening process, even with an external fixator in place. During the distraction phase, patients need to be examined and x-rays obtained every 2 to 3 weeks to evaluate bone growth, nerve and muscle function, and pin sites, and to monitor for and prevent complications. The lengthening rate may be adjusted at these visits.
3: Consolidation Phase
After the desired lengthening or deformity correction has been achieved, all adjustments to the lengthening device cease. Newly regenerated bone is weak at that point, and would be unable to resist shortening or breakage without the continued support of the external or internal fixation device.
When lengthening is performed with external fixation alone, the external device remains in place until the end of the consolidation phase. The average total external fixation treatment time for children is 1 month per centimeter and for adults can be as long as 2 months per centimeter.
The longer treatment time for adults is the reason we prefer to use the lengthening over nails (LON) or fully implantable method in adults whenever possible. In the case of LON, the external fixator is removed at the end of the distraction phase by performing minor outpatient surgery, in which the internal rod is connected to the bone at its sliding end. The external fixator can be removed because the bone is supported from the inside by the rod. Therefore, the external fixator is in place only for the distraction phase. The consolidation occurs with the rod alone.
In the case of internal lengthening, the device stops automatically at the desired length and the rod supports the bone until it is fully hardened. Bone healing is judged based on the x-rays. X-rays show us how much calcium is in the bone. (Calcium appears white on radiographs; the whiter the bone, the more calcium is present.) When there is sufficient calcium throughout the region where the bone was separated (distraction gap), the bone is judged to be healed. The x-rays must be obtained approximately once per month to evaluate bone healing.
Once the bone looks sufficiently healed enough so that it will not collapse, the external fixiator rods are temporarily removed to reduce the tension on the bone. This is called dynamization and is the last step before fixator removal. Usually the external fixator is removed one month after dynamization. The apparatus can usually be removed one month later.
Phase 6: Removal of the External Fixator
For patients who undergo treatment with external fixation alone, the apparatus can be removed with the patient awake or under anesthesia. Most patients prefer a general anesthetic. Removal of an external fixator is an outpatient procedure. After removal, many patients require a cast for a month of additional protection. Patients with internal fixation in place usually do not require a cast because the internal hardware protects the bone until it is fully hardened.
COMPLICATIONS OF LENGTHENING SURGERY
There are many potential complications with lengthening surgery. Meticulous surgical technique, vigilant follow-up, and aggressive rehabilitation are the most important factors to prevent and even treat complications. Because lengthening occurs gradually, complications also occur in slow motion. It is important to prevent complications and to recognize if they are occurring.
Most complications are completely reversible by nonoperative or operative means. It is critical to treat complications very aggressively to end up with normal function and no negative sequellae (secondary consequences) from surgery.
This is why the results of lengthening are very dependant on the experience of the surgeon. A more experienced surgeon not only knows how to perform the surgery better, but knows how to prevent and treat complications so that there is no residual problem at the end of treatment.
Bone Complications
Delayed Union or Nonunion
Bone regeneration is usually reliable especially in children. It is important to monitor the bone healing by x-ray every two weeks to make sure it is keeping up with the increasing distraction gap. If the bone healing lags behind, then the rate of lengthening should be decreased. Delay in bone healing can be due to damage to the periosteal and endosteal tissues of the bone at the time of the osteotomy. For this reason, using a small incision and performing the osteotomy in a low energy minimal invasive fashion is important. Instability of the external fixation is another cause of delayed healing. It is important to recognize this and to stabilize the external fixator. Delay in bone healing leads to delay in removal of the external fixator. If the bone fails to heal completely then a bone defect or nonunion may result. It is important to recognize this, then perform surgery to excise the cyst or fibrous tissue in the gap and to bone graft the defect. This usually results in healing of the bone within three months of the surgery.
Premature Consolidation
If the bone healing is abundant or fast, the bone may heal prematurely. This can be recognized on the x-rays and the rate of lengthening should be increased to 5 quarter turns per day or to 3 half turns per day. This should only be done for a week at a time to make sure that the bone formation does not suddenly get delayed. If there is a failure to increase the distraction gap then the bone is prematurely consolidated. In these cases the bone should be reosteotomized (cut) in the operating room.
Axial Deviation
During lengthening, the muscle, fascia, and bone regenerate tissues create forces to resist the lengthening. These forces are often unbalanced and tend to bend the bone during the lengthening. The resultant deformity needs to be recognized and corrected at the end of the distraction phase. If the deformity is not recognized or corrected then the bone will heal with deformity.
Soft Tissue Complications
Muscle Contractures
Contractures (shortening of the tissue or muscle) occur when the soft tissues cannot accommodate changes in bone length. To treat contractures effectively, one needs to identify the potential problem muscles. In tibial lengthening, for example, the problem muscles are the gastrocnemius ( largest muscle in the calf) and toe flexors. As a result, patients can develop knee flexion, ankle plantar flexion, and toe flexion contractures.
In the femur, both rectus femoris and hamstring muscles resist lengthening. This can result in a fixed flexion (flexed or bent) deformity of the knee and a flexion range-of-motion deficit.
Lengthening of the humerus (long bone in the arm) involves the fewest problems. If problems do arise, they are the result of biceps and brachioradialis tightness. In the forearm, finger flexors tighten more quickly, causing proximal and distal interphalangeal flexion and hyperextension of the metacarpophalangeal joints.
Despite these problems, contractures can be treated with the following modalities:
Passive stretching and soft tissue mobilization: Patients should take pain medications 30 minutes before receiving therapy. A muscle is prepared for stretching by applying moist heat for 15 minutes before activity. The antagonist muscle should always be activated before stretching the agonist muscle. The muscle can thereby be relaxed by means of reflexive inhibition. Another effective method of reducing pain during range-of-motion exercises is to immobilize the skin over the pin site with tight gauze wraps. This reduces skin motion around the pins.
In general, biarticular muscles (muscles that work on two joints) should be stretched 20 to 30 times per session, and uniarticular muscles (muscles that work on one joint) should be stretched 10 to 15 times per session. When stretching a biarticular muscle, obtain maximum stretch in the direction opposite that of the muscle action at both proximal and distal joints, and hold each stretch for 20 to 30 seconds. Some examples of biarticular muscle stretch include rectus femoris stretch with the hip in full extension, and knee flexion and ankle dorsiflexion with knee extension to stretch the gastrocnemius muscle.
Positioning: Optimal maximal positions vary based on the affected body parts. For example, patients undergoing tibial lengthening should be positioned with the knee extended straight and the ankle flexed up. Knee extension along with hip abduction is a desirable position for patients who are undergoing femoral lengthening. Patients undergoing humeral lengthening need elbow extension. Patients undergoing forearm lengthening require elbow extension (elbow straight), wrist in slight dorsiflexion (bent upward and backward), and finger extension (straight).
Splints: Custom designed splints help to keep the soft tissues (muscles and tendons) stretched properly. Using a splint to place a muscle under tension for as many hours as possible helps prevent contractures by obtaining plastic response in the connective tissue.
Dynamic splinting: In certain situations, we use special dynamic splints. These are different from static splints because they include a spring-like or elastic mechanism to produce elongation of the tissues through a low-load prolonged-duration stretch. Dynamic splints work most effectively in treating knee and elbow flexion contractures. Note that splints work only in optimal positions, and that their tension should always be increased gradually. These types of splints are also often used for the fingers and toes.
Muscle Weakness
In addition to joint stiffness, patients may experience muscle weakness. This is caused by lack of use (because the patient cannot walk normally). Pain can also inhibit muscle function, adding to weakness. The following modalities help in the management of muscle weakness:
Electrical stimulation: Electrical stimulation can be used as an adjunct to a strengthening program and to augment voluntary muscle contraction. To accomplish this, a muscle stimulator machine is applied to the surface of the limb (the thigh, for example) and a low-level electrical signal stimulates the underlying muscle to contract. Some children do not tolerate this well.
Hydrotherapy (water therapy): Hydrotherapy helps patients avoid significant muscle weakness, especially when both legs are being lengthened. It promotes active range of motion. The natural buoyancy allows simulated weight bearing. The higher the level of the water (chest-deep versus waist-deep, for example), the more "weightless" one feels. Hydrotherapy also helps in keeping pin sites clean.
Progressive weight bearing: Programs of progressive weight bearing are important through all phases of limb lengthening rehabilitation. During the lengthening phase, patients should be encouraged to perform weight bearing as prescribed. Some patients may experience pain from increased weight bearing, and the increased weight bearing can cause undue stress on the pins or wires. Weight bearing is even more critical during the consolidation phase. The patient should progress from two crutches to one and then to none. He or she should also perform closed chain exercises. (Closed chain exercises are resistive exercises in which the load is applied through the feet, such as leg press, stair climber, and bicycle). Many patients can walk without assistive devices and have no limp during the latter part of the consolidation phase.
Nerve Injury
Nerve injury is not common and occurs primarily in patients who are undergoing tibial lengthening. It happens when certain nerves do not stretch enough to accommodate the bone lengthening. Peroneal nerve (outer side of the leg) symptoms during tibial lengthening are caused by referred pain in the dorsum (back) of the foot. This pain may present initially as hyperesthesia (increased sensitivity) and then as hypoesthesia (reduced sensitivity). Weakness in the muscles that control toe and foot action are sometimes observed. Pain medications usually do not help. Referred pain in the top of the foot is increased with knee extension and is relieved by flexing the knee. When signs of peroneal nerve irritation occur, the use of a dynamic knee extension splint should be discontinued and knee extension exercises should be reduced.
A patient who may be developing this condition should notify the doctor as soon as possible. In most cases, reducing the rate of lengthening reduces the symptoms of nerve injury. In cases in which patients do not respond to rate reduction, peroneal nerve decompression surgery is required. This involves a small incision and, at most, an overnight hospital stay. When indicated, nerve decompression prevents permanent nerve injury and allows the nerve to recover. This, in turn, allows the lengthening to continue.
PHYSICAL AND OCCUPATIONAL THERAPISTS
The efforts of the entire team of physical and occurapational therapists, family members and caregivers will determine the success of the limb lengthening process. Physical and occupational therapists play a critical role in limb lengthening and skeletal deformity correction. A successful functional outcome depends on the quality and amount of therapy a patient receives. Success also depends on the involvement of the family members and caregivers. Physical therapists should encourage families and care providers to attend the physical therapy sessions. There, they can learn the optimal positions for stretching and the passive stretching exercises. With team effort, limb lengthening rehabilitation can be successful.
