Lower limb length discrepancy (LLD) is a frequent condition in pediatric orthopedics. Even moderate discrepancies can induce pelvic obliquity and compensatory scoliosis, modifying the distribution of joint loads at the hips and lumbar spine. These biomechanical imbalances are suspected to contribute to early degenerative conditions such as osteoarthritis or chronic low back pain.

The aim of this study is to quantify the biomechanical impact of LLD in children aged 10 to 15 years, using a combination of low dose biplanar EOS imaging (EOS Imaging System) and synchronized ground reaction force (GRF) measurements from integrated force platforms. These data will be used in musculoskeletal models developed in collaboration with the Biomechanics and Impact Mechanics Laboratory (LBMC, Laboratoire de Biomécanique et Mécanique des Chocs), enabling the estimation of hip joint and lumbar intervertebral disc loads.

This is the first pediatric study integrating EOS imaging, force platforms, and personalized musculoskeletal modeling to explore the mechanical consequences of LLD. The findings are expected to improve clinical reasoning and guide early therapeutic strategies.

Lower limb length discrepancy (LLD) is a frequent condition in pediatric orthopedics. Even moderate discrepancies can induce pelvic obliquity and compensatory scoliosis, modifying the distribution of joint loads at the hips and lumbar spine. These biomechanical imbalances are suspected to contribute to early degenerative conditions such as osteoarthritis or chronic low back pain.

The aim of this study is to quantify the biomechanical impact of LLD in children aged 10 to 15 years, using a combination of low dose biplanar EOS imaging (EOS Imaging System) and synchronized ground reaction force (GRF) measurements from integrated force platforms. These data will be used in musculoskeletal models developed in collaboration with the Biomechanics and Impact Mechanics Laboratory (LBMC, Laboratoire de Biomécanique et Mécanique des Chocs), enabling the estimation of hip joint and lumbar intervertebral disc loads.

A temporary orthopedic compensation (shoe lift) will also be tested to assess its immediate biomechanical effect. Participants will be evaluated at baseline (two EOS acquisitions: with and without compensation) and at 2 years (without compensation).

This is the first pediatric study integrating EOS imaging, force platforms, and personalized musculoskeletal modeling to explore the mechanical consequences of LLD. The findings are expected to improve clinical reasoning and guide early therapeutic strategies.

Inclusion Criteria:

• Children aged 10-15 years
• Anatomical LLD > 5 mm, clinically measured
• EOS imaging indicated by the pediatric orthopedic surgeon in routine care
• Ability to stand still for 30 seconds without assistance
• Covered by social security
• Parental consent and non-opposition obtained

Exclusion Criteria:

• - Functional or postural LLD without true anatomical discrepancy
• History of major pelvic or spinal surgery
• Severe neurological or orthopedic condition preventing standing (e.g. cerebral palsy, progressive myopathy)
• Fixed equinus deformity preventing plantar support
• Major lower limb deformity (severe genu varum/valgum)
• Contraindication or inability to undergo EOS imaging

The study population will consist of approximately 100 pediatric patients (aged 10 to 15 years) presenting with an anatomical lower limb length discrepancy (LLD) greater than 5 mm, confirmed by clinical evaluation. Participants will be recruited consecutively during routine outpatient visits at the Pediatric Orthopedics Department of Hôpital Femme-Mère-Enfant (HFME), Hospices Civils de Lyon, Bron, France. This hospital is a tertiary referral center in pediatric orthopedics, receiving children from the Rhône-Alpes region and beyond.

All included patients will undergo EOS imaging as part of their standard clinical assessment for LLD, ensuring that the study is fully integrated within the regular care pathway. The cohort therefore represents a specialized clinical sample of children with LLD, rather than a general population or community-based sample.