Is it likely for legs to come out different lengths after orthopedic surgery for a femur (thigh bone) fracture?

Leg Length Discrepancy After Femur Fracture Surgery

Leg length discrepancy after femur fracture surgery is common but not inevitable—the likelihood depends primarily on fracture stability, patient age, and surgical technique, with rates ranging from 12-40% for discrepancies ≥10mm.

Incidence and Clinical Significance

• In pediatric femur fractures, 40% of patients develop leg length discrepancy ≥10mm, with 12.5% experiencing discrepancies ≥20mm 1
• The most common pattern is overgrowth of the injured femur (occurring in 38 of 45 patients with discrepancy in one long-term study), with mean lengthening of 14.1mm 2
• Shortening occurs less frequently (7 of 45 patients), with mean shortening of 14.3mm 2

Primary Risk Factors for Leg Length Discrepancy

Patient-Related Factors

• Age 4-9 years at time of injury significantly increases overgrowth risk (P = 0.04) 2
• Patients younger than 13 years show continued changes in leg length beyond the traditional 2-year post-injury window 2

Fracture-Related Factors

• Fracture stability is the single most important predictor, with length-unstable fractures having 4-fold increased odds of developing discrepancy ≥10mm (OR 4.0, P = 0.020) 1
• Axial deviation >10 degrees increases overgrowth risk (P = 0.04) 2
• Multiple repositions (≥2 attempts) significantly increase overgrowth (P = 0.0005) 2

Treatment-Related Factors

• Delayed surgical treatment beyond 48 hours increases overgrowth risk (P = 0.0035) 2
• Plate fixation carries the highest risk of inducing overgrowth (P = 0.0003) compared to other fixation methods 2
• Intramedullary nailing shows lower rates of leg length discrepancy compared to conservative treatment or plate fixation 2

Temporal Pattern of Leg Length Changes

The traditional teaching that overgrowth stabilizes after 2 years is incorrect:

• In 16 of 34 patients followed beyond 2 years, the growth rate of the affected femur actually decreased, reducing leg length discrepancy by 5-15mm 2
• Overgrowth continued in 7 patients beyond 2 years, increasing by 5-10mm 2
• In 12 patients aged ≥13 years at initial review, no further change occurred 2

Prevention Strategies During Surgery

Positioning Considerations

• Maintain hip flexion within 90 degrees during procedures to avoid nerve compression and positioning-related complications 3
• Periodic assessment of limb position during prolonged procedures is recommended 3
• Avoid excessive hip extension beyond comfortable preoperative range 3

Surgical Technique

• Minimize number of reduction attempts to reduce overgrowth stimulus 2
• Achieve anatomic reduction with axial deviation <10 degrees 2
• Consider early definitive fixation (within 48 hours) when clinically appropriate 2
• Choose fixation method based on fracture pattern—avoid plate fixation when intramedullary nailing is feasible 2

Common Pitfalls to Avoid

• Do not assume leg length discrepancy is permanent at 2 years post-injury—continued monitoring through skeletal maturity is necessary, particularly in patients under age 13 2
• Do not overlook fracture stability assessment—this is the strongest predictor of discrepancy and should guide treatment planning 1
• Do not delay surgical treatment unnecessarily—delays beyond 48 hours increase overgrowth risk 2
• Recognize that some overgrowth is physiologic—the injured femur typically overgrows by 10-15mm as part of normal healing response 2

Monitoring Recommendations

• Serial radiographic measurements comparing bilateral femur lengths at regular intervals until skeletal maturity 2
• Clinical leg length assessment at each follow-up visit 1
• For patients under age 13, continue monitoring beyond the 2-year mark as further changes are likely 2