Biomedical subjects
Publications and source records attributed to B Roszek.
Annex II of the Medical Device Directive (MDD) is used frequently by manufacturers to obtain CE-marking. This procedure relies on a full quality assurance system and does not require an assessment of the individual medical device by a Notified Body. An investigation into the availability and the quality of technical documentation for Annex II devices revealed severe shortcomings, which are reported here.
Effects of decreasing stimulation frequency on length-force characteristics were determined for rat medial gastrocnemius muscle. The peripheral nerve was stimulated supramaximally with a succession of twitch and frequencies of 100, 50, 40, 30, and 15 Hz. Active peak tetanic and twitch forces and active muscle geometry were analyzed. Optimal muscle length and active slack length shifted significantly (P < 0.05) to higher muscle length by a maximum of 2.8 and 3.2 mm, respectively. Further significant effects were found for distal fiber length and mean sarcomere length of distal fiber (increases) and for fiber angle and aponeurosis length (decreases). Neither muscle length range between active slack and optimal length nor aponeurosis angle was altered significantly. We concluded that decreasing stimulation frequency-dependent length-force characteristics are affected by a complex interaction of length-dependent calcium sensitivity, potentiation of the contractile system, distribution of sarcomere length, and interactions between force exerted and aponeurosis length. Length-dependent calcium sensitivity seems to be a major factor determining the magnitude of the shift of optimal muscle length.
In vivo strain measurements at 8 locations on the tibia of the goat were performed. Successive in vitro calibrations were used to determine the assumed linear relationship between the measured strain signals and the external loads (3 forces and 3 moments) at the tibia. For the reconstruction of the in vivo external loads from the strain data, a transformation matrix was created from the calibration experiments, using 'singular-value decomposition'. The method is a reliable technique for measuring in vivo loads during functional gait and gives reproducible results.