THE ALTERATION OF KNEE KINEMATICS FOLLOWING INJECTION OF BOTULINUM TOXIN INTO THE RECTUS FEMORIS OF PATIENTS WITH SPASTIC CEREBRAL PALSY

Abstract

The use of botulinum is established in the management of spasticity in cerebral palsy; most series concentrate on its injection into the Gastrocnemeii and hamstrings. During the swing phase, the rectus femoris acts concentrically at the hip, and eccentrically at the knee, to accelerate the thigh while controlling the rate of knee flexion. In spasticity there is prolonged activity with some of the rectus firing concentrically, resulting in a decreased rate of knee flexion, decreased peak flexion and a delay to its occurrence. These factors contribute to poor foot clearance.

Our aim was to establish whether the temporary paralysis of the rectus femoris by botulinum injection can improve knee kinematics.

Patients included were ambulant diplegics with clinical and kinematic evidence of rectus femoris spasticity. Independent clinical assessment was combined with 3D gait analysis pre and post injection. Kinematic Data for sagittal plane knee flexion/extension allowed us to calculate changes in the rate of flexion, the degree of peak flexion and time to its occurrence. Clinical evidence of spasticity was detected using the fast Duncan Ely test. There were 7 patients who underwent 15 injections into Rectus Femoris. Age range: 8–25 years (mean, 14–4 years). From the sagittal plane knee flexion graphs 10/15 had improvement in the rate of knee flexion, 9/15 had improvement in the peak flexion and 8/15 in the time to peak flexion. The mean increase in the fast Duncan Ely was 20. 5 degrees.

Using 3 Dimensional gait analysis we observed an improvement in the kinematic data following injection of the rectus femoris with botulinum.

This was accompanied by a clinical reduction of spasticity as measured by the Duncan Ely test. As with other muscle groups, botulinum injection of the rectus femoris has the potential to be both therapeutic and diagnostic.