L'apport de l'analyse électromyographique de la marche dans l'étude du pied spastique de l'infirme moteur d'origine cérébrale : étude préliminaire

PURPOSE OF THE STUDY: This preliminary study describes the methodology and the results of gait analysis in cases of equinus and equino-varus deformity of the foot in cerebral palsy children. The ultimate goal was to establish an aid to decision in spastic foot surgical management. MATERIAL: A prospective series of 12 walking children (16 feet) with cerebral palsy has been evaluated prior to surgical correction of equinus or equino-varus deformity of the foot. The mean age was 8 years (range 4 to 11 years of age). METHOD: The pattern of muscle activity during gait cycle has been recorded by surface electrodes for the tibialis anterior, the triceps and the peroneae and by implanted electrodes for the tibialis posterior. Foot switches have been used to differentiate swing and stance gait phases. The results were compared with these of a series of normal children previously published. RESULTS: In four cases, the dynamic equinus was due to an extended or continuous contraction of the triceps surae. The varus deformity appeared to originate from two muscles: the tibialis posterior in 9 cases and the tibialis anterior in 1 case. Both muscles were responsible for the deformity in 2 cases. Two muscular activation patterns were observed in the tibialis posterior: inverted (2 feet) or permanent (9 feet). From the main muscle which was responsible for deformity, we have determined the surgical technique which was most appropriate to restore the muscular balance. DISCUSSION: Our observations confirm Perry's hypothesis, namely that selective and phasic control during the walking cycle does not occur for patients suffering from cerebral palsy. Different surgical procedures were chosen according to the literature on this subject. In the treatment of equinus deformity, lengthening of the Achilles tendon is a satisfactory technique for hemiplegic patients. But we prefer gastrocnemius recession described by Vulpius in spastic diplegia in order to avoid over-lengthening or calcanal gait. If it can be shown that posterior tibial muscle overactivity is the cause of equinovarus, we perform a posterior tibial tendon lengthening, as proposed by Ruda and Frost, or a split posterior tibial tendon transfer as developed by Green. If the posterior tibial muscle is active only during the swing phase, we accomplish a split posterior tibial tendon transfer through the interosseus membrane as advocated by Saji. If the anterior tibial muscle is continuously active, a split anterior tibial tendon transfer to the cuboid described by Hoffer is performed. If the activity is continuous in both the tibial posterior and the tibial anterior muscles, we add a posterior tibial myotendinous lengthening to the split anterior tibial tendon transfer. CONCLUSION: Since 1992, we have developed in our institution a gait analysis laboratory in order to bring objective data in the process of decision making for tendon transfer surgery. With 4 years experience, this objective support now seems to us compulsory in decision of type of transfer. The goal of this preliminary study was to explain how we use the data and match these to our experience and literature