Dynamic Lower Extremity Alignment in Children With Achondroplasia

Abstract

The purpose of this study is to analyze lower extremity dynamic malalignment during gait using a 3-dimensional kinematics and kinetics in 13 children (3-17 years old) with achondroplasia and to compare measurements of alignment and malrotation between gait, radiographic, and clinical measures. Gait analysis in the coronal plane showed a varus malalignment of the knee (19 +/- 13 degrees) and variable tibial torsion abnormalities (13 [internal] +/- 15.7 degrees). Radiographs also showed knee varus malalignment (16 +/- 9 degrees); however, there was poor correlation with gait analysis measures (P > 0.05). In the sagittal plane, radiographs showed genu recurvatum deformity (23.5 +/- 13.2 degrees), although the sagittal plane knee kinematics were normal. Kinetic analyses of the knee showed high internal knee valgus moments (external varus moments, 0.48 +/- 0.25 N m/kg), which were significantly different from the normal population (P < 0.05). In conclusion, there is a 3-dimensional, complex, dynamic deformity of the lower extremity present in children with achondroplasia. We recommend a very careful assessment of the limb focusing on both the static and dynamic varus deformity and tibial torsion using a combination of radiographic, clinical, and gait analysis.

Magnetic resonance evaluation of the knee in children and adolescents with achondroplasia

“…Genu recurvatum is more typically associated with achondroplasia rather than inability to fully extend [8]. This notable difference in position may be from hip flexion associated with exaggerated lumbar lordosis and rotation of the pelvis in the supine position, leading to knee flexion as well.…”

“…Mutation in this gene increases FGFR3 function and results in characteristic clinical and radiographic features [3,4]. Increased ligamentous laxity is present throughout the lower extremities and can lead to complex lower-extremity malalignment such as genu varum, genu recurvatum, ankle varus and internal tibial torsion [5][6][7][8][9]. Common radiographic findings include spinal stenosis, thoracolumbar kyphosis, increased lumbar lordosis, decreased interpedicular distance, iliac wing squaring, metaphyseal flaring, thickened and shortened diaphyses of long bones, long fibulae and increased space between the third and fourth metacarpals (trident hand).…”

How Reliable Are Standard Radiographic Measures of the Foot and Ankle in Children With Achondroplasia?

“…Usually, the condition requires realignment surgery with a goal of limb alignment correction or limb lengthening [11,18,20]. The hip and knee alignment in achondroplastic children has been analyzed by Inan et al [7,8]; however, the foot and ankle alignment in achondroplastic children is less well understood and easy to be overlooked [5]. Guichet et al [5] proposed that planning surgery on limbs requires a good understanding of limb mechanics with precise evaluation of any malalignment problems, including the ground reaction applied to the foot and ankle.…”

“…Lower extremity radiographs including weightbearing radiographs of the feet and ankles are crucial for preoperative planning [5,7,8,20], but the reliability of radiographic measures in this patient population is unclear [5], and differences between the ACH population and children without ACH remain poorly characterized.…”

Sık görülen iskelet diplazileri ve hareket analizi özellikleri

“…Ayrıca lomber lordozun artışına sekonder, anterior pelvik tiltin arttığı da gözlemlenmiştir (Şekil 2. a, b). [8] Kalça kinematikleri, artmış pelvik anterior tilt nedeni ile kısıtlı kalça ekstansiyonunu yansıtması dışında normal popülasyon ile uyumlu bulunmuştur. Kalça rotasyonu da normal popülasyonla uyumlu olmasına rağmen değişkenlik göstermiştir.…”