Management of Leg Length Inequality

James J. McCarthy, MD, and G. Dean MacEwen, MD

Disclosures

J South Orthop Assoc. 2001;10(2) 

In This Article

Treatment Methods

Treatment of leg length inequality involves many different approaches, such as orthotics, epiphysiodesis, shortening, and lengthening, which can be used alone or combined in an effort to achieve equalization of leg lengths.

Leg length inequality of 2 cm or less is usually not a functional problem. Often, leg length can be equalized with a shoe lift, which usually corrects about two thirds of the leg length inequality. Up to 1 cm can be inserted in the shoe. For larger leg length inequalities, the shoe must be built up. This needs to be done for every shoe worn, thus limiting the type of shoe that the patient can wear. Leg length inequalities beyond 5 cm are difficult to treat with a shoe lift. The shoe looks unsightly, and often the patient complains of instability with such a large lift. A foot-in-foot prosthesis can be used for larger leg length inequalities. This is often done as a temporizing measure for young children with significant leg length inequalities. The prosthesis is bulky, and a fixed equinus contracture may result.

Epiphysiodesis is a reliable procedure that inhibits growth with few complications. This obviously cannot be done on skeletally mature patients, and the final leg length inequality and the degree of growth inhibition need to be predicted and are subject to errors. Because the procedure effectively shortens the longer leg and is usually done on the uninvolved side, it may be unappealing to the patient and family.

One of the most useful indications for epiphysiodesis is in conjunction with limb lengthening for large leg length inequality. By performing an epiphysiodesis, a second or third lengthening may be avoided. If a patient has a 10 cm limb length inequality and has gained 7 cm by lengthening, an appropriately timed epiphysiodesis can result in limb length equality for the final 3 cm discrepancy, without the need for a second lengthening.

Phemister[36] described another technique for epiphysiodesis. He removed a section of the epiphysis, then rotated it 90° and replaced the bone. Currently, the most common technique is the percutaneous drill epiphysiodesis, done with the aid of image intensifier. This technique has been reported to result in physeal closure in 85% to 100% of patients,[37,38,39,40] with few complications.[41] Scott et al[41] compared the Phemister technique with the percutaneous technique and found the results to be similar. They preferred the percutaneous technique because of the ease of the procedure and decreased morbidity. Staple epiphysiodesis can be done, but it results in more complications and is more invasive. Often the staples are prominent or they back out.[42] Staple epiphysiodesis has the theoretical advantage of allowing for growth after staple removal. Percutaneous epiphysiodesis using transphyseal screws have also been used in an effort to provide a reversible method of inhibiting growth with less morbidity. This technique has been used primarily in the ankle for correction of angular (valgus) deformity.[21,43] We use epiphysiodesis commonly to correct predicted leg length inequality up to 5 or 6 cm.

Shortening techniques can be used after skeletal maturity to achieve leg length equality. Shortening can be done in the proximal femur using a blade plate or hip screw, in the mid-diaphysis of the femur using a closed intramedullary (IM) technique (Figs 2 and 3), or in the tibia. Shortening is an accurate technique[44] and involves a much shorter convalescence than lengthening techniques.[44,45] Quadriceps weakness may occur with femoral shortenings, especially if a mid-diaphyseal shortening of greater than 10% is done.[46] If the femoral shortening is done proximally, no significant weakness should result. Tibial shortening can be done, but there may be a residual bulkiness to the leg, and risks of nonunion and compartment syndrome are higher (Fig 4).[47,48] If a tibial shortening is done, shortening over an IM nail and prophylactic compartment release are recommended. We limit the use of shortenings to 4 to 5 cm leg length inequality in patients who are skeletally mature.

Figure 2.

Femur after shortening over an intramedullary nail.

Figure 3.

(Left) Intramedullary saw making second osteotomy, 4 cm proximal to first (completed) osteotomy. (Right) Internal hook chisel is used to split fragment of bone.

Figure 4.

Tibial shortening over intramedullary nail, 5 months postoperatively.

Lengthening is usually done by corticotomy and gradual distraction. This technique can result in lengthenings of 25% or more, but typically lengthening of 15%, or about 6 cm, is recommended.[49] The limits of lengthening depend on patient tolerance, bony consolidation, maintenance of range of motion, and stability of the joints above and below the lengthened limb.

Numerous fixation devices are available, such as the ring fixator with fine wires, monolateral fixator with half pins, or a hybrid frame. The choice of fixation device depends on the desired goal. A monolateral device is easier to apply and better tolerated by the patient. The disadvantages of monolateral fixation devices include the limitation of the degree of angular correction that can concurrently be obtained; the cantilever effect on the pins, which may result in angular deformity, especially when lengthening the femur in large patients; and the difficulty in making adjustments without placing new pins. Monolateral fixators appear to have a similar success rate as circular fixators, especially with more modest lengthenings (20%).[50]

About 30 days in the fixation device per centimeter of length gained are necessary for both lengthening and consolidation. In general, femoral lengthenings heal faster than tibial, as do lengthenings in younger patients (less than 14 years of age). Treatment of dysplasias, such as achondroplasia, is associated with fewer complications than treatment of limb length inequality.[51,52] The level of the corticotomy does not seem to have a significant effect in the tibia, and mid-diaphyseal appears to be the best in the femur.[51]

Other techniques, such as the Wagner technique, acute lengthening, and physeal distraction, are used much less commonly to obtain limb length equality. The Wagner technique involves immediate and more rapid lengthening followed by bone grafting and plating. When comparing these techniques, Arron and Eilert[53] and DalMonte and Donzelli[54] found that the Ilizarov technique resulted in fewer complications and does not require an additional procedure for plating and bone grafting. When we reviewed our results of lengthening in children with fibular hemimelia, we found that the use of the Ilizarov technique resulted in fewer procedures but increased pain scores and a slightly higher complication rate than the Wagner technique.

Acute correction is difficult to obtain and is limited to about 3 cm. Acute lengthening can be done in the mid-diaphysis of the femur or through an innominate osteotomy. The latter may be indicated for a patient with primary pelvic asymmetry.

Lengthening has also been done through physeal distraction. Although this is a less invasive technique in that no corticotomy is necessary, it can be painful if the physis acutely separates, and it may lead to premature physeal closure and septic arthritis. Currently, we do not routinely perform either acute lengthenings or lengthening through physeal distraction. Experimental methods of producing lengthening, such as transfer of cultured chondrocytes,[55] vascular surgery,[56] and periosteal sleeve resection[55] are being studied.

Large leg length inequalities can be treated by staged lengthenings or by simultaneous ipsilateral femoral and tibial lengthenings. Additionally, lengthenings can be combined with appropriately timed epiphysiodesis in an effort to produce leg length equality. Staged lengthenings are often used for congenital deficiencies such as fibular hemimelia, in which 15 cm or more may be needed to produce leg length equality. We typically plan for the final lengthening to be completed by age 13 or 14 years, and allow at least 3 years between lengthenings.

Lengthening of both the tibia and femur simultaneously requires aggressive therapy and treatment of soft tissue contractures. Curran et al[57] reported the need for surgical release of soft tissue contractures in 3 of 8 patients treated with simultaneous ipsilateral femoral and tibial lengthenings.

Lengthening over an IM nail can be done in an effort to decrease the amount of time the fixator needs to be worn and to prevent angular malalignment (Figs 5 and 6). This technique requires that the patient be skeletally mature and it carries a higher risk of osteomyelitis (up to 15%). Additionally, if premature consolidation occurs, a repeat corticotomy is more difficult.[58,59,60]

Figure 5.

Lengthening over intramedullary nail.

Figure 6.

Placement of fixator with pins posterior to medullary canal.

In this technique,[59] an IM rod is placed in standard fashion. Reaming must be at least 1.5 mm greater than the rod diameter (2 mm is preferable), and the rod should have minimal bowing (to allow for easier distraction). The corticotomy is made before the IM rod is placed and can be done with an IM saw. The fixator is placed with the pins either posterior (Fig 6) or anterior to the rod. A true lateral view is needed to ensure that there is separation between the rod and half pins. A technique of using a guide wire and cannulated drill will help prevent unnecessary drill holes. If the rod is left short, the distal half pins can be inserted below the rod, although this can produce a stress riser below the IM rod. Initially, the rod is locked proximally. After the distraction period, the rod is locked distally and the fixator is removed. Care must be taken to ensure that there is ample rod length for stability distally after distraction. Lengthening over an IM nail will obligatorily lengthen the anatomic axis of the femur, and if significant femoral lengthening is planned, it will medialize the mechanical axis.

A number of designs for totally implantable IM devices are being explored. Such a device would offer the advantages of producing immediate axial stability, preventing angular deformity, and eliminating pin tract infections and scarring. The Albizzia nail uses a ratcheting mechanism that elongates with a rotational maneuver.[61] The biomechanics of this device and standard IM nails are similar and have been well studied.[62] A motorized, programmable IM nail has been developed and is currently under clinical investigation.[63,64] With all IM nails, significant angular correction must be achieved acutely, and even placing the nail in a patient with significant angular deformity may be impossible. The patients need to be close to skeletal maturity to prevent avascular necrosis of the femoral head (in the femur) or proximal tibial physeal closure, and the IM canal must be large enough to accommodate the IM nail.

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