Using the Ilizarov method, one can lengthen bones of both the upper and lower extremities, including bones of the hand and foot and the surrounding soft tissue.

The most commonly lengthened bones in the lower extremity include the tibia and fibula, the femur, and the metatarsals. In the upper extremity, the most commonly lengthened bones are the humerus, the radius and ulna, and the metacarpal bones.

Consideration is given to lengthening of the surrounding soft tissues, which include the muscle tendon unit, neurovascular bundle, and skin.¹¹

During bone lengthening, the tension in the surrounding soft tissue may predispose the lengthened segment to deformity.^{13, 20} Frequently encountered deformities include the following:

During large lengthenings, care is necessary to prevent subluxation or dislocation of the adjacent joint.²⁰

Femoral lengthening, especially in the setting of congenital short femur, may result in hip or knee subluxation or dislocation secondary to associated deficient acetabular coverage at the hip and the high frequency of deficient cruciate ligaments at the knee.

Tibial lengthening may cause knee or ankle subluxation and progressive equinus deformity of the foot.

Metatarsal and metacarpal lengthening can cause metatarso- or metacarpophalangeal subluxation.

All of these issues are considered during any lengthening procedure.

The term distraction osteogenesis implies synthesis of new bone by slow, gradual (no more than 1 mm per 24 hours) controlled distraction of the bone fragments under conditions of rigid fixation.¹¹

The new bone is formed mostly by intramembranous ossification and, to a lesser extent, through endochondral ossification.^{9, 11}

To provide maximum construct stability and to minimize soft tissue trauma, it is important to maintain the two fragments well apposed to each other following the corticotomy.

Distraction is a good tool for influencing reparative regeneration of both the bone and the soft tissue (“stretching tension,” as described by Ilizarov). However, the new regenerate ossifies and remodels slowly.

Gradually removing distraction and applying mild compression increases the rate of remodeling. Therefore, the regenerate becomes more rigid against bending loads.

Functional load is a strong stimulus for the improvement of blood flow and allows organic remodeling of the regenerated osseous part. The extent of load depends on the stability of fragments and the amount of regenerate.

The natural history of the limb length discrepancy (LLD) depends on the condition causing the LLD.²² A partial list of causes are as follows:

Upper extremity discrepancy or shortening usually does not cause major functional problems but may result in significant cosmetic deformities.

Predicted lower extremity discrepancy of 2 to 5 cm may be dealt with by long-leg epiphysiodesis in children or by leg lengthening using the Ilizarov technique. LLD greater than 5 cm usually is amenable to leg lengthening.²²

Untreated LLD of more than 3 cm may result in pelvic obliquity, visual gait disturbance, short-legged gait, or structural/nonstructural scoliosis.²²

The underlying cause of a leg length discrepancy can typically be elucidated by careful history and physical examination.

The common symptoms at presentation are limp, compensatory gait mechanics, pelvic obliquity, and nonstructural scoliosis.

Physical findings depend on the etiologic factors.²²

In hemihypertrophy (both syndromic and nonsyndromic), the affected extremity may be larger in both length and girth. In classic hemihypertrophy, upper extremity hypertrophy as well as hemifacial asymmetry may be present. Vascular overgrowth syndromes may be associated with cutaneous or deep hemangiomas, which may alter surgical approaches to attempted limb equalization.

Clinically, LLD is best measured by the block test, in which the shorter leg is placed on increasingly larger measured blocks until the posterior iliac crest is level. Discrepancies as small as 2 cm are accurately detected by this method, and detection of discrepancies is largely unaffected by patient size or body mass.²⁵ Direct measurement of leg length from anterior superior iliac spine to the tip of medial or lateral malleolus is significantly less accurate.

True leg length is measured from the anterior superior iliac spine to the tip of the medial malleolus. It is important to place the legs in identical positions to measure true leg length.

Apparent leg length is measured with the patient supine with the legs parallel to each other. The landmarks are the umbilicus to the tip of medial malleolus. Pelvic obliquity and fixed deformities of the hip and knee affect the reading. This method is also significantly less accurate than block measurement.

Range of motion is noted for all joints, primarily the hip, knee, ankle, and subtalar joints. The ankle joint range of motion is measured with the knee in extension and flexion.²²

Plain radiographs have traditionally been used to document the objective measurement of LLD (FIG 1).

Full-length (hip to ankle) anteroposterior (AP) radiographs are obtained in standing position with both patellae facing directly anteriorly. The appropriate-sized block is placed beneath the shorter leg to level the pelvis. A long x-ray cassette (51 inches) is used with the x-ray beam center focused on the knee from a distance of 10 feet. A radiolucent ruler often is used to assist in calculation of limb discrepancies.

Skeletal age can be determined by a left hand/wrist radiograph in combination with the Greulich and Pyle method.⁸

Parental and sibling height may be useful in interpreting predicted height in the previously mentioned methods.

In LLD secondary to physeal growth arrest, graphical or arithmetic methods are helpful in determining appropriate timing of epiphysiodesis.

No treatment is required for a predicted LLD less than 2 to 2.5 cm at maturity.

A shoe lift can be used as treatment for leg length discrepancies at maturity less than 2 cm.

A prosthesis may be necessary if deformities are so severe that adequate length or ambulatory ability cannot be achieved by operative methods.