[Is surgery of the hip adductor muscles justified in children with cerebral palsy?].

INTRODUCTION

Restricted passive hip abduction in children with cerebral palsy (CP) may be caused by uninhibited resting contractions and/or retractions, i.e., shortened muscle body or tendons. Pathological short tendons require surgical intervention, but lack of muscle body elasticity responds to physiotherapy or a postural splinting. Clinical examination can distinguish between short tendons and short muscle body. The thigh is slowly and passively extended while palpating the tendon. Tension is detected in the tendon when the leg is at angle Ao. The elastic tension of the muscle body then increases until no further movement is possible, at angle Amax. The difference Amax-Ao is an index of the structural length of the muscle body. If this difference is reduced during passive straightening there is shortening of the muscle body; if it is displaced it indicates shortening of the tendon. The value Ao indicates the muscular or tendon origin of the retraction for a given passive limitation (Amax). This study defines the physiological values of Ao and the relative precisions of chemical and instrumental measurements.

MATERIALS AND METHODS

A total of 30 children aged 9-11 years, 10 CP patients (7 girls and 3 boys, mean age 10.3 years) and 20 controls (11 girls and 9 boys, mean age 10.5 years) were studied. All the CP children had lower limb spasticity and adopted an adduction posture. None had undergone hip muscle surgery. Ao and Amax were measured clinically with a goniometer and EMG to monitor muscle silence, and experimentally using a deformable parallelogram and force transducers.

RESULTS

The minimum physiological value of Ao was 8 degrees with the knee flexed and 0 degree with the knee extended. Smaller values of this angle indicated tendon retraction. The difference between Ao and Amax in the controls and CP children was < or = 10 degrees; the reproducibilities of the clinical measurement of Ao and Amax were very similar.

DISCUSSION

Clinical examination provides an acceptably accurate method of distinguishing between tendon and muscle body retraction of adductor muscles in CP children. The conditions required for successful measurement are: careful examination with strict positional reference and sufficiently relaxed pelvic muscles. A hip extension angle Ao of less than 8 degrees with the knee flexed or 0 degree with the knee straight indicates tendon retraction requiring tendon surgery, otherwise, the retraction involves only the muscle body. This reduced elasticity can be overcome by prolonged extension (at least 6 hours/24). Effective muscle extension may be hindered by non-suppressed adductor contractions. This must be overcome prior to physiotherapy by surgery of the ramus ant. n. obturatorii.

CONCLUSION

Clinical measurement of Ao of adductor muscles is a reliable way of distinguishing between tendon retractions requiring surgery and muscle body retractions resulting from staying too long in a position with the muscle shortened. This muscle body shortening can be due to lack of physiotherapy or a stretching apparatus treatment, pathological contractions, or compensation for disorders of the controlateral limb.