Overview
Leg length inequality is a frequent concern for parents and an incidental finding for orthopaedists. Management ranges from no treatment to multistage reconstruction to limb ablation with prosthetic fitting, depending on the size of the inequality and the function of the limb. Treatment relies on estimating the projected discrepancy at skeletal maturity and knowing the dynamics of lower-limb growth. (Tachdjian)
Mild asymmetry is common in healthy people. For example, 32% of 600 military recruits had inequality of 0.5 to 1.5 cm and 4% had more than 1.5 cm, and equal leg lengths were found in only 23% of 1,000 army recruits. (Tachdjian)
Evaluation and Prediction of the Final Discrepancy
Clinical and radiographic assessment of the inequality, identification of the cause, and charting of growth in the skeletally immature child. Cause matters: total physeal destruction (infection, fracture, irradiation, surgical ablation) gives fairly predictable growth loss. Congenital limb deficiencies give a fairly constant percentage of shortening throughout growth. (Tachdjian)
Growth contribution. The distal femoral physis contributes about 37% of total limb length growth (about 9 mm per year) and the proximal tibial physis about 28% (about 6 mm per year). (Tachdjian)
Prediction methods.
Anderson–Green–Messner growth-remaining method and the Menelaus modification of White–Stubbins (based on chronologic age).
Moseley straight-line graph: mean error 0.6 cm in 23 mature patients after epiphysiodesis, versus 0.9 cm for the Anderson–Green–Messner method. It assumes the patient keeps the same percentile skeletal age and that growth inhibition is linear. The Rotterdam straight-line graph modifies this using more modern growth data and is used the same way.
Paley multiplier method: mature length = present length × a multiplier for age and sex. For example, for boys the multiplier is 1.31 at 10 years, 1.18 at 12 years and 1.08 at 14 years. For girls it is 1.19 at 10, 1.07 at 12 and 1.00 at 14. One analysis found it less accurate than skeletal-age methods for timing arrest in vascular malformations.
Shapiro's five patterns of discrepancy development (803 patients): (1) upward slope, constant percentage of inhibition; (2) upward slope with deceleration; (3) upward (or downward) slope then plateau (typical after femoral shaft fracture overgrowth); (4) upward slope, plateau and then upward slope again (proximal femoral problems such as septic arthritis, Perthes, AVN after DDH treatment); (5) upward slope, plateau, then downward slope. Type 1 was typical of proximal femoral focal deficiency, Ollier disease, congenital femoral deficiency with over 6 cm shortening and physeal obliteration. (Tachdjian)
Pitfalls. Prediction is imperfect. Skeletal age from the Greulich and Pyle atlas varies (in one study, 50% of children were assigned a skeletal age differing by more than 1 year between radiologists). In one series only 22 of 67 patients treated by epiphysiodesis had a final discrepancy under 1 cm, mostly due to incorrect use of growth charts or inadequate epiphysiodesis. Longitudinal follow-up with serial scanograms is more reliable than a single examination. (Tachdjian)
Indications and Treatment Selection
Traditionally inequality over 2 to 2.5 cm is treated, but that threshold is hard to justify as absolute. Discrepancy above 5% of the contralateral limb (about 4 cm at maturity in a 50th-percentile patient) and toe-walking are associated with measurable changes in gait and energy cost, so equalization should be attempted above this. Smaller discrepancies are treated based on the individual impact and the patient's concern. A trial shoe lift of 5 mm less than the true discrepancy helps adolescents decide in equivocal cases (usually 2 to 2.5 cm). (Tachdjian)
Always review the options, problems and expected outcomes with patient and family, ideally with a psychologist experienced in children. Lengthening requires commitment to pin care, exercises and follow-up, and treatment may be declined if adherence, family support or understanding is inadequate. (Tachdjian)
Treatment options (Tachdjian Table 20.5)
No treatment: discrepancy under 2 cm.
Shoe lift: consider above 2 cm. Recommended for toe-walkers. Lifts of up to 1 cm can be inside the shoe, larger lifts go on the sole, and lifts over 8 cm are poorly tolerated. There is little evidence of protective benefit.
Extension orthosis or prosthesis: for children who walk with extreme long-leg knee flexion or who hop on the long leg.
Epiphysiodesis: predicted discrepancy over 2 cm. Not as the sole means for discrepancies over 8 cm or with inadequate growth remaining.
Epiphyseal stapling: same indications as epiphysiodesis.
Acute surgical shortening: skeletally mature patients, femoral discrepancy 2–5 cm, tibial discrepancy 2–3 cm.
Acute lengthening: femoral 2–4 cm, tibial 2–3 cm. Avoid in patients at risk of neurovascular injury or with poor bone quality.
Gradual lengthening: femoral discrepancy over 4 cm and inequality with angular deformity needing correction. Avoid with unstable joints next to the segment, or a noncompliant patient.
Epiphysiodesis (Shortening of the Long Leg by Growth Arrest)
Phemister technique: a rectangular cortical block (about 3 cm × 1 to 1.5 cm × 1 cm deep) is removed across the physis, the physis curetted, and the block reversed 180 degrees. White and Stubbins used a diamond-shaped block rotated 90 degrees. Green and Anderson described wide grafts into the diaphysis with drilling of the remaining physis.
Percutaneous epiphysiodesis (Bowen and Johnson; Canale; Ogilvie): a stab incision directly over the physis and destruction of the physis under fluoroscopy with curets, drills, burrs, a tube saw or reamers. Remove enough physis (Bowen left only the central third), follow the undulations of the physis, and remove it in the AP direction as well as peripherally and centrally. Series reported shorter hospital stay, better cosmesis and less need for therapy, with a few reports of continued growth (13% percutaneous and 15% Phemister in one series) while others reported 100% closure.
Proximal fibula: Stephens recommended not doing proximal fibular epiphysiodesis if under 3–4 years of growth remain, but the Tachdjian authors saw symptomatic fibular head prominence or instability after isolated tibial epiphysiodesis and usually do the fibula whenever the proximal tibia is done. Take care not to injure the peroneal nerve.
Results and complications. Green and Anderson: complication rate (including slow fusion) of 9.3% in 237 epiphysiodeses, with angular deformity needing osteotomy in 4 patients. Makarov's review of 863 patients: 7% had complications (transient neurologic symptoms, knee stiffness, overcorrection in 6, and angular deformity or continued physeal growth in 31). Those with complications were younger, had greater discrepancy and more often a congenital cause. (Tachdjian)
Epiphyseal stapling (Blount): three evenly spaced staples across the physis, extraperiosteal, tines parallel to the physis, confirmed on AP and lateral radiographs. Results varied: some series had staple extrusion or breakage, residual growth, reoperation and need for osteotomy after removal, and Tachdjian's institution no longer uses stapling for leg length correction. (Tachdjian)
Shortening of the Long Leg in the Mature Patient
Femoral shortening of 2–5 cm. Blade plate fixation is an acceptable alternative to closed intramedullary shortening, avoiding fat embolism risk. Skeletally immature patients should not have closed shortening with intramedullary rodding because of the risk of femoral head AVN.
Tibial shortening is done less often because it must be open, the fibula must be osteotomized, and complications such as compartment syndrome, circulatory impairment and foot weakness are more frequent. Reports used step-cut osteotomy with two-screw fixation or intramedullary fixation (2.5 to 5.1 cm). One group recommends limiting tibial shortening to 3 cm. Counsel patients about temporary foot and ankle weakness. (Tachdjian)
Lengthening of the Short Leg
The purpose of treatment is primarily to maximize function and mobility, and only secondarily to address cosmesis. The motivation for treating minor discrepancies should not be to prevent long-term joint or spine injury. Sofield: "improved function, not just increased length, is the objective." (Tachdjian)
Stimulation of growth (periosteal stripping, foreign material, bone pegs) has no effective, reliable method. (Tachdjian)
Indications. Toe-walking begins at about 5% shortening (about 4 cm), so 4 cm expected inequality is a relative indication for lengthening, and serious consideration is warranted when expected shortening approaches 10% (about 8 cm), since shortening procedures would be excessive. Angular deformity with ipsilateral shortening is a relative indication. For discrepancies of 10% or less, the author prefers waiting until skeletal maturity if function is not compromised, which avoids growth disturbance and allows more precise planning. For larger discrepancies, combine lengthening with a timed contralateral epiphysiodesis, or stage lengthenings of 15% to 20% of the original segment length. (Tachdjian)
Acute lengthening (for example transiliac, Salter-modified) is described for limited gains. Older Wagner-type diaphyseal lengthening needed at least three procedures (device and osteotomy, plate and bone graft, plate removal), and was associated with poor regenerate bone, fractures, infection and extensive scarring. (Tachdjian)
Callotasis (Ilizarov and De Bastiani):
Make a limited exposure (usually metaphyseal) and perform a low-energy corticotomy with minimal soft-tissue and periosteal stripping, using osteotome techniques or a series of drill holes joined by an osteotome. Avoid heat necrosis from oscillating saws. The critical factor is minimizing soft-tissue injury, not preserving the medullary artery.
Apply external fixation, keeping the bone fragments in apposition with no initial distraction.
Latency period of 3 to 21 days for callus to form.
Distraction at about 1 mm per day, divided into four 0.25-mm increments (rhythm), adjusted for the quality of new bone.
Consolidation in the fixator, typically about twice as long as the distraction period. The "healing index" is about 30 days per centimeter of lengthening.
After fixator removal, regenerate bone remodels and generally appears normal. It is much more amenable to repeat lengthening than bone formed with the Wagner method.
Regenerate bone depends on rigidity of fixation, damage to soft tissue and medullary canal, rate and rhythm of distraction, patient age, osteotomy location and soft-tissue envelope. Metaphyseal osteotomies heal faster than diaphyseal ones, the proximal tibia faster than the distal, the anterior tibia slower than the posterior, and the side of the surgical approach slower. (Tachdjian)
Gradual lengthening can cause temporary muscle damage and reduced blood flow, and the muscles' resistance to lengthening is a main limit. (Tachdjian)
Complications
Of epiphysiodesis: angular deformity, overcorrection, incomplete arrest or continued growth, knee stiffness, nerve symptoms, and inaccurate prediction leading to residual discrepancy. (Tachdjian)
Of lengthening: injury to muscle, nerve or vessels; overdistraction of muscle or nerve; poor bone formation; joint compression; and the psychological stress of external fixation. (Tachdjian)
Of shortening: fat embolism and AVN with intramedullary rodding in the immature; compartment syndrome, circulatory impediment and foot weakness after tibial shortening. (Tachdjian)
References
Podeszwa D. Limb length discrepancy. In: Herring JA, ed. Tachdjian's Pediatric Orthopaedics. Elsevier. Chapter 20.