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

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.     

Ultrathin crosslinked membranes at the interface between oil and water

The tensio-active properties of different types of diesters can be used to synthesize two-dimensional model networks at the interface between oil and water. We have systematically studied rubber-elastic, glass-like and transient membranes, which are stabilized and crosslinked by physical or chemical contacts. The kinetics of surface gelation and the mechanical properties of the crosslinked membranes were investigated by measuring two-dimensional rheological parameters, such as the shear modulus or the surface viscosity. The experimental data of these investigations are in fairly good agreement with the theoretical predictions of percolation theories. Further informations on the molecular structure of the crosslinked membranes can be obtained from electron spin resonance (ESR) measurements. Using spin labels of significantly different sizes, which are diffusing from the aqueous environment into the oil phase, it is possible to determine the average mesh size of the interfacial network structure. The systematic study of these ultrathin membranes offers new insights into aspects of current research, and opens interesting new technical applications.