MUSCULOSKELETAL MODELING IN DETERMINING THE EFFECT OF BOTULINUM TOXINON THE HAMSTRINGS OF PATIENTS WITH CROUCH GAIT

This studs aimed to determine the effect of hamstring botulinum toxin A (Btx-A) injection in 10 children with crouch gait in terms of change s in muscle length and lower-limb kinematics. Before Btx-A injection l imb kinematics were recorded. Maximum hamstring lengths and excursions were calculated by computer modelling of the lower limb. Data were co mpared with the averaged hamstring lengths of 10 control children. Ham strings were defined as short if their length was shorter than the ave rage maximum length minus one standard deviation. Gait analysis was re peated a weeks after isolated hamstring Btx-A injection. Pre- and post injection kinematic data and muscle lengths were then compared. Four o f 18 injected limbs in three subjects had short medial hamstring befor e injection, none of the subjects had short lateral hamstrings. Muscle excursion was significantly reduced in the short and adequate maximum muscle length groups. A significant increase in the semimembranosus a nd semitendinosus length in all of the injected limbs was noted. only in the short muscle group was a significant increase in muscle excursi on observed. Knee extension improved by 13 degrees in the adequate mus cle length group and by 15.6 degrees in the short muscle length group. Pelvic tilt and hip flexion increased in both groups non-significantl y. Average walking speed postinjection increased from 0.60 ms(-1) to 0 .71 ms(-1). Short hamstrings are over-diagnosed in crouch gait. Hamstr ing Btx-A injection in patients with crouch gait produces significant, repeatable muscle lengthening and improved ambulatory function.