Musculoskeletal modelling in determining the effect of botulinum toxin on the hamstrings of patients with crouch gait

Abstract

This study aimed to determine the effect of hamstring botulinum toxin A (Btx‐A) injection in 10 children with crouch gait in terms of changes in muscle length and lower‐limb kinematics. Before Btx‐A injection limb kinematics were recorded. Maximum hamstring lengths and excursions were calculated by computer modelling of the lower limb. Data were compared with the averaged hamstring lengths of 10 control children. Hamstrings were denned as short if their length was shorter than the average maximum length minus one standard deviation. Gait analysis was repeated 2 weeks after isolated hamstring Btx‐A injection. Pre‐ and postinjection kinematic data and muscle lengths were then compared. Four of 18 injected limbs in three subjects had short medial hamstring before 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 and semitendinosus length in all of the injected limbs was noted. Only in the short muscle group was a significant increase in muscle excursion observed. Knee extension improved by 13° in the adequate muscle length group and by 15.6° in the short muscle length group. Pelvic tilt and hip flexion increased in both groups non‐significantly. Average walking speed postinjection increased from 0.60 ms‐1 to 0.71 ms‐1. Short hamstrings are over‐diagnosed in crouch gait. Hamstring Btx‐A injection in patients with crouch gait produces significant, repeatable muscle lengthening and improved ambulatory function.

Effects of distal hamstring lengthening on sagittal motion in patients with diplegia

“…Content validity refers to the extent to which a measure represents all logical facets of the phenomenon being measured. We presume that the content validity of modeled hamstring length has been established, in view of the number of studies that have attempted to measure hamstring length [13,14,25,26]. Concurrent validity concerns the correlation with other well-defined methods that have been previously validated.…”

Muscle length and lengthening velocity in voluntary crouch gait

“…A very important assumption in this study as well as in many other modeling studies [2][3][4]9], is that muscles are modeled as simple strings, acting between origin and insertion. Geometrical origin-insertion length might be a valid estimate for the total length of the muscle-tendon complex, especially when wrapping points are accounted for.…”

The role of estimating muscle-tendon lengths and velocities of the hamstrings in the evaluation and treatment of crouch gait

“…Several research groups have estimated the muscle-tendon lengths [18][19][20][21][22][23] and/or velocities [2,24] of the hamstrings during normal and crouch gait. A consistent finding from these studies is that not all persons with crouch gait walk with hamstrings that are shorter than normal [18][19][20][21][22][23][24] or slower than normal [2,24].…”