There are many potential complications with lengthening surgery. Meticulous surgical technique, vigilant follow up, and aggressive rehabilitation are crucial to preventing complications. Since lengthening is gradual, most complications can be identified early, while they are developing. This is why the results of lengthening are very dependent on the experience of the surgeon. A more experienced surgeon not only knows how to perform the surgery better but knows how to spot potential complications as they develop and act swiftly to address them.
Nerve injury is unusual with femoral lengthening and more often occurs in tibial lengthening. During distraction, if the patient complains of pain in the dorsum (back, upper surface) of the foot or asks for frequent massage of the foot, this is likely referred pain from entrapment of the peroneal nerve. The pain may present as hyperesthesia (increased sensitivity) or hypoesthesia (reduced sensitivity).
Potential nerve complications are identified using quantitative sensory testing using the Pressure Sensitive Sensory Device (PSSD) or near nerve conduction using fine electrodes.
Nerve problems identified early can usually be treated by slowing the rate of distraction. If symptoms continue or motor signs develop, the patient may require a peroneal nerve decompression. This is a minor surgical procedure in which the peroneal nerve is identified and surrounding soft tissues are released to relieve pressure on the nerve. Dr. Paley has used nerve decompression surgery to successfully treat nerve injury.
Poor or Failure of Bone Formation
Bone regeneration is usually reliable, however, in some cases hypotrophic regenerate requires slowing of the distraction rate. The rates can be slowed to 3/4, 1/2, or 1/4 mm per day. If the regenerate bone does not improve, a decision will need to be made as to whether lengthening may be continued knowing that the resultant bone defect will likely need to be bone grafted.
Biphosphonate infusion (e.g. zolidronic acid) can be used to prevent bone resorption while permitting bone formation. At the conclusion of lengthening, if the distraction gap does not fill, a bone graft will need to be performed.
Incomplete Osteotomy or Premature Consolidation
Lack of separation of the osteotomy site after a week of distraction may be due to an incomplete osteotomy or a periosteal hinge that will not separate. Continued distraction can lead to an acute separation of the bone ends. There may be an audible pop, and the separation is usually quite painful. The pain will continue until the bone is acutely shortened. If the bone does not separate or if the patient or parents wish to avoid a painful separation, a reosteotomy will be performed.
If the bone is healing quickly during distraction, this can be recognized on the follow up x-rays. Dr. Paley will recommend increasing the lengthening to 5 quarter-turns per day or up to 3 half-turns per day. This should be done a week at a time and closely monitored to avoid delayed bone formation.
Joint Subluxation / Dislocation
Joint stability is judged radiographically (via x-rays). In the hip, a break in Shenton’s line or increased medial-lateral, head-teardrop distance indicates subluxation (partial dislocation) of the hip. Hip subluxation does not usually occur if there is adequate coverage of the femoral head. However, adduction and flexion contracture predisposes the hip to subluxation even with adequate coverage.
If hip subluxation occurs during lengthening or consolidation, the patient is immediately taken to the operating room for soft tissue releases. A closed reduction of the hip is also performed. The external fixator is then extended to the pelvis to protect the hip joint.
In the knee, tendency towards flexion contracture predisposes the tibia to posterior subluxation. Prevention of knee subluxation involves a combination of soft tissue releases and extension of the external fixator across the knee to the tibia during femoral lengthening. This is done with hinges to permit knee motion.
In the ankle, the joint is often fixed in a 90 degree position during lengthening of the tibia. This protects the ankle from subluxation. After the lengthening, the foot is released and range of motion exercises can begin.
In implantable limb lengthening (i.e. the PRECICE), in which fixation cannot span the joint to protect it, specialized braces are worn to maintain and protect the joints.
Fractures associated with limb lengthening can be divided into those that occur while the fixator is on, those that occur at the time of removal, and those that occur after removal.
In the past, Dr. Paley noticed an unacceptably high level of femoral fractures after fixator removal. To correct this, we started prophylactically Rush rodding the femur at the time of removal. This new protocol virtually eliminated the complication of refracture after lengthening.
Joint Stiffness & Contracture
A contracture is a shortening of the muscle and occurs when the soft tissues cannot accommodate changes in bone length. In tibial lengthening, the gastrocnemius muscle resists lengthening, and the patient is at risk of developing knee flexion contractures, plantar flexion contractures, and toe flexion contractures. In femoral lengthening, the rectus femoris and hamstring muscles resist lengthening, and the patient is at risk of developing flexion deformities of the knee.
Joint stiffness is preventable. Surgical release or lengthening of the specific soft tissues reduces the joint reactive forces on the joint due to lengthening. Physical therapy is essential to successful limb lengthening. We will not perform lengthening if the patient cannot organize outpatient physical therapy on a daily basis.
For more information, see Rehabilitation & Physical Therapy
If the knee gets stiff to flexion despite adequate rehab, a quadricepsplasty can be performed. When there is a concomitant flexion contracture, Dr. Paley will choose either open or closed treatment: closed requires an external fixator and gradual distraction. Open means posterior capsule release. Physical therapy, including dynamic splinting can be used first to obtain extension of the knee before considering quadricepsplasty surgery.
For patients undergoing tibial lengthening, where the foot is not immobilized, an ankle splint is used to maintain the foot position at 90 degrees. Physical therapy should focus on stretching the ankle to prevent contracture of the Achilles tendon.