Relationship between flexion contractures of the joints of the lower extremities and the sagittal profile of the spine in patients with cerebral palsy: a preliminary report

Background. The considerable incidence of kyphosis in patients with cerebral palsy (CP) causes back pain and aggravates movement disorders. However, few studies have investigated the pathogenesis of this condition.

Aim. To identify the relationship between patient motor abilities, the severity of flexion contractures of the knee and hip joints and spinal sagittal profile changes, and the impact on the latter by surgical correction of flexion contracture of the knee joint.

Material and methods. The study cohort included 17 pediatric CP patients (11 boys and 6 girls) with a mean age of 13.1 ± 1.3 (range, 10–16) years and level 2–4 spastic diplegia according to the Gross Motor Function Classification System. The relationship between radiological indicators of the spine sagittal profile and motor abilities of children, as well as the severity of flexion contractures at the hip and knee, and the degree of insufficiency of the active extension of the knee were investigated. Of these 17 patients, 12 underwent surgery to correct flexion contracture of the knee, which involved lengthening of leg flexors, to analyze the impact of contracture on the sagittal profile of the spine. The following radiological indicators were assessed: angle of thoracic kyphosis (CC), lordosis angle (UL) of the lumbar spine, and sacral inclination angle (SS). The study included patients with a CC of at least 30°.

Results. Results of an X-ray study showed that the severity of kyphosis was 50.7° ± 2.1°, lordosis was 30.3° ± 4.3°, and SS was 30.5° ± 3.3°. There was a significant association between kyphosis and flexion contracture of the knee joint, as well as between lordosis and insufficient active extension of the knee joint. After elimination of the flexion contracture of the knee, the degree of severity of the CC (thoracic kyphosis) was unchanged, while UL (lordosis angle) and SS (sacral inclination angle) increased by approximately 10°.

Conclusion. The severity of kyphosis in patients with CP is mainly dependent on the degree of flexion contracture of the knee joint. Although elimination of contractures does not lead to kyphosis correction, it increases the degree of lumbar lordosis and tilting of the sacrum.