Understanding Leg Length Discrepancy (LLD)

Leg Length Discrepancy (LLD) is a condition where there is a measurable difference in the lengths of an individual’s legs. While minor discrepancies are common and often asymptomatic, larger differences can lead to functional and musculoskeletal problems, impacting mobility, posture, and overall quality of life.

Common Causes of Leg Length Discrepancy

1. Congenital Causes

Some individuals are born with differences in limb length due to genetic factors or developmental abnormalities. Conditions such as congenital short femur or fibular hemimelia can result in significant LLD from birth.

2. Developmental and Growth Disorders

Growth plate injuries or conditions like hemihypertrophy, where one side of the body grows more than the other, can lead to LLD. Diseases like neurofibromatosis or Blount’s disease may also contribute to uneven limb development.

3. Post-Traumatic LLD

Fractures involving the growth plate in children can cause premature closure, leading to growth arrest and subsequent limb length discrepancies. Conversely, some fractures can heal in an overgrown state, leading to lengthening.

4. Post-Surgical LLD

Surgical interventions, such as hip replacements or femoral fractures requiring fixation, can sometimes result in a discrepancy if proper alignment is not maintained.

5. Infections and Other Pathologies

Bone infections (osteomyelitis), tumors, or inflammatory conditions affecting bone growth can lead to LLD. These conditions may cause destruction or premature closure of growth plates.

6. Neuromuscular Disorders

Conditions such as cerebral palsy or poliomyelitis can cause muscle imbalances that affect limb growth and function, leading to functional or structural LLD.

Diagnosis of Leg Length Discrepancy

Diagnosis involves a thorough clinical examination, including:

• Physical Examination: Assessing gait, pelvic tilt, and compensatory mechanisms like scoliosis.
• Imaging: Standing long-leg X-rays, CT scans, or MRI to accurately measure discrepancies and assess underlying pathology.

Management of Leg Length Discrepancy

The treatment approach depends on the severity of the discrepancy and patient symptoms. In a paediatric patient, treatment is determined by the Childs predicted leg length discrepancy at skeletal maturity.

Non-Operative Management

• Shoe Lifts: Effective for discrepancies under 2 cm, shoe lifts can help equalise leg lengths and alleviate symptoms. Small show lifts can be a simple insert that goes directly into a normal shoe.
• Physical Therapy: Strengthening and stretching exercises to address muscular imbalances and postural adaptations.
• Orthotics: Custom braces or inserts to improve biomechanics and reduce functional impact. Orthotics include custom shoes where larger lifts are built into the sole of the shoe

Operative Management

Surgical intervention is considered when discrepancies are significant (typically >2 cm) or symptomatic.

1. Epiphysiodesis (Growth Plate Modulation)

• A minimally invasive procedure performed in growing children where the growth plate is temporarily or permanently fused to allow the shorter limb to catch up.
• Used in cases where future growth projections suggest a manageable correction.

2. Leg Lengthening Procedures

• External Fixation (Ilizarov Technique): Gradual bone distraction using an external frame to stimulate new bone growth.
• Internal Lengthening Nails (e.g., PRECICE system): A motorised, implantable nail that gradually lengthens the bone under controlled conditions.
• Complications: Infection, joint stiffness, nerve injuries, and muscle contractures.

3. Leg Shortening Procedures

• Femoral or Tibial Shortening Osteotomy: Indicated for discrepancies >5 cm where lengthening is impractical. Involves removing a bone segment and internal fixation.
• Complications: Loss of muscle strength, knee and hip dysfunction, or altered gait mechanics.

Cosmetic Limb Lengthening: High Risk, High Cost

While primarily used for functional correction, limb lengthening has gained popularity for cosmetic purposes. Individuals seeking to increase height undergo controlled osteotomies with external or internal fixation devices. However, this is a high-risk procedure with significant complications, including:

• Infections and Nonunion: The prolonged distraction process increases the risk of infections and poor bone healing.
• Nerve and Vascular Injury: Stretching tissues beyond their natural limits can lead to nerve damage, chronic pain, and circulatory issues.
• Joint Stiffness and Muscle Contractures: Patients often require extensive rehabilitation to regain function and mobility.
• Psychological Impact: The lengthy and painful recovery process, coupled with high financial costs, can take a toll on mental well-being

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** Please read my seperate blog on cosmetic leg lengthening.

Conclusion

Leg Length Discrepancy is a complex condition with various causes and treatment options. While minor discrepancies may be managed conservatively, significant differences often require surgical intervention. Advances in limb lengthening techniques have improved outcomes, but these procedures carry notable risks, especially when performed for cosmetic reasons. A comprehensive assessment by an orthopaedic specialist is essential to determine the most appropriate course of action based on individual needs and long-term functional goals.

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