Kinematic and dynamic biomechanical values in relation to muscle activity during contact head impact

OBJECTIVE

For the evaluation of neck injury the relative distance was observed between a marker placed on the forehead and a marker placed on the shoulder and also by change of the angle. To compare the severity of head injury a value of maximum head acceleration was used, HIC and a 3 ms criterion. All criteria were related to the activity of musculus sternocleidomastoideus and musculus trapezius in a situation of expected or unexpected contact impact.

MATERIALS AND METHODS

The situation was recorded using a Qualisys system, head acceleration of probands in three axes was recorded using the accelerometer, activity of neck muscles was monitored by a mobile EMG.

RESULTS

Maximum head acceleration was 5.61 g for non-visual and 5.03 g for visual. HIC36 was 6.65 non visual and 5.97 for visual. 3-ms criterion was 5.37 g for non-visual and 4.89 g for visual and max. force was 291 N for non-visual and 314 N for visual. The average time of muscle activation of the observed group without visual perception is 0.355 s after hitting an obstacle, with visual perception 0.085 s before the crash.

CONCLUSIONS

Kinematic values indicate more favourable parameters for neck injuries for visual. Head injury criteria show an average decrease of about 10% for visual. We can conclude that the visual perception means a significant increase in pre-activation of the observed muscle group of almost 745% and lower activation in following phase of approximately 90%.

[Combined sciatic/3-in-1 block in routine surgical care]

For decades it has been known that the combined sciatic and femoral nerve block could be used for operations on the leg. Nevertheless, it is used in very few hospitals as a routine method for surgical anesthesia and only few publications exist in this area. To highlight some practical aspects, we have produced a retrospective study of 660 cases of femoral and sciatic nerve blocks used exclusively for operating purposes. For all blocks we used a nerve stimulator. For the sciatic nerve we normally used the posterior approach. The femoral nerve was blocked in the "3 in 1" method of Winnie to include the obturator and lateral femoral cutaneous nerves as well. All patients had been premedicated (Table 3). In 67% we used bupivacaine 0.5%, in 29% prilocaine 1%, in 4% mixed agents, and in 5 cases mepivacaine 1.5%. We added epinephrine 1:400,000 in all cases except those with cardiac contraindications. The maximal dose was 80 ml or 9.76 mg/kg prilocaine and 105 ml or 7.72 mg/kg bupivacaine. Both doses were tolerated without complications. Applying strict criteria (Fig. 1 + 2), the overall failure rate was 17.7% (Table 1): depending on the anesthesiologist administering the block 7.1%-27.8% (Fig. 3) and on the type of operation 4.6%-42.3% (Table 2). The most important factor influencing the failure rate was the anesthesiologist. The individual failure rate of the first 30 blocks of each anesthesiologist (V30) was nearly equal to the overall individual failure rate (Fig. 3). The form and time of premedication and the extent of sedation did not influence the results.(ABSTRACT TRUNCATED AT 250 WORDS)