Dynamic Lower Extremity Deformity in Children With Pseudoachondroplasia.

Area of Science:

• Orthopedics
• Biomechanical Engineering
• Pediatric Skeletal Dysplasias

Background:

• Pseudoachondroplasia involves altered cartilage oligomeric matrix protein (COMP) production, leading to rhizomelic dwarfism.
• Common manifestations include lower extremity deformities, osteoarthritis, and ligament laxity.
• Coronal knee angulation and tibial torsion create complex deformities with variable surgical outcomes.

Purpose of the Study:

• To compare 3D gait analysis with radiographic measurements of lower extremity deformities in children with pseudoachondroplasia.
• To assess the correlation between kinematic and static measurements of coronal knee alignment and tibial torsion.

Main Methods:

• Utilized 3D gait analysis to evaluate kinematic deformities in 12 children (3-15 years).
• Compared gait analysis data with static deformities measured via standing anteroposterior radiographs.
• Calculated correlation coefficients between radiographic and kinematic measurements.

Main Results:

• Both methods showed significant variability and strong correlation in coronal knee deformities (r=0.70).
• Mean varus alignment was similar between gait analysis (13.5±13.1°) and radiographs (16.2±17.1°).
• Internal tibial torsion (15±19°) moderately correlated with knee varus (r=0.45, P<0.01).

Conclusions:

• Varus-valgus alignment measurements correlate well between gait analysis and radiographs.
• Tibial torsion is correlated with knee varus, providing a basis for deformity assessment.
• Standing AP radiographs can assess deformity in lieu of gait analysis, but further studies are needed on surgical outcomes and COMP's biological effects.