Introduction: The purpose of this study was to quantify changes in lower limb muscle strength in children with spastic diplegic cerebral palsy 6 months after multi-level orthopaedic surgery.

Method: A consecutive sample of 20 children ( 10 girls and 10 boys, mean age 10.6) with spastic diplegia was studied prospectively. All participants had soft-tissue and bony surgical procedures performed as part of their clinical management. Physiotherapy treatment commenced following surgery. Lower limb muscle strength, pre and 6 months post-surgery, was measured, in addition to routine gait and function assessment. Maximum voluntary isometric strength of 5 muscle groups was measured bilaterally using a digital dynamometer. Paired-samples t-tests were performed.

Results: There was a marked deterioration of muscle strength (p < 0.05) in all muscle groups. Medial hamstrings and hip flexors showed the greatest decline with an average decrease of 54% and 41% respectively. Analysis of gait parameters showed a significant improvement in kinematics (p< 0.05) but a decrease in walking velocity and cadence. Motor function decreased significantly (p< 0.05). There was reduced motor power in 18 of the 20 at 6 months.

Discussion: Our results quantified objectively the magnitude of strength changes after multi-level surgery and show that weakness may be greater and persist longer than expected. This information will be useful for planning treatment after multi-level surgery and is part of a randomised trial investigating strength training. In general there is a decrease in power but an improvement in gait.