The Influence of Orthotics on Lower Limbs Biomechanics in CP

Abstract

The biomechanics of the human body has a direct impact on the quality of gait cycle. Patients with Cerebral Palsy (CP) often present incorrect gait patterns associated with structural deformities which directly influence the locomotor functions. The key to therapeutic success in those patients is the use of lower limb orthotics of the AFO type. This type of orthopedic devices should correct the skeletal deformities, optimize function and ensure high quality of daily use. Alignment of the lower limb supported by orthotics in all planes is crucial for changing the abnormal position of the ground reaction force (GRF) vector during a pathological gait cycle. GRFs produce an external moment of forces that causes extension or flexion of the lower limb in the sagittal plane. At the same time, those external conditions are balanced by an internal moment of forces generated by muscles. Some of the muscles are not directly attached to the joints but still support their function. This mechanism is called biomechanical coupling. This interesting relationship is also related to the inclination or reclination of the shank vertical angle (SVA) against the foot fixed on the ground in the midstance (MST) phase of gait. An optimal SVA angle is 7-12 degrees of tibial inclination. An insufficient or excessive SVA angle can be controlled by ankle foot orthotics (AFO). Those types of splints provide for better control of foot clearance during the swing phase and support distal stability of the lower limb chain during the stance phase of the gait cycle. An interdisciplinary approach is the key to success in the therapy of CP children who use lower limb orthotics. Nowadays, tridimensional gait analysis is an important tool for objective monitoring of those patients. It shows all kinematic and kinetic data recorded during gait with AFO and therefore helps to fine-tune orthotics used by CP patients.