Lower extremity traumatic vascular injury at a level II trauma center: an analysis of limb loss risk factors and outcomes.

AIM: The objectives were to review in our series the risk factors, management and outcomes of patients who sustained vascular injuries in the lower limbs and to determine the effect of risk factors and treatment on the outcome of the injured extremity. METHODS: Fifty-six patients submitted to surgical treatment were retrospectively reviewed. Results were analysed in terms of type of operation and reconstruction, intraoperative and 30 day complications, reconstruction occlusion, major amputation and mortality. RESULTS: The mechanism of trauma was blunt in 30.4% and penetrating in 69.6%. The overall primary amputation rate was 5.4%, the overall secondary amputation rate was 1.8%. The overall intraoperative and postoperative mortality were 1.8% and 5.4% respectively. At univariate analysis, the presence of compartment syndrome and ischemia time >6 hours were associated with a significantly higher risk of early reconstruction thrombosis (both P=0.03). It showed also that the number of patent vessels (P=0.0000) and the presence of a MESS score >7 (P=0.0000) significantly affected primary amputation, and that the occurrence of postoperative deep wound infection or sepsis (P=0.0000), of tibio-peroneal trunk injury (P=0.003) and of a MESS score >7 (P=0.004) significantly affected secondary amputation. CONCLUSION: The number of patent arteries (0-1), the presence of a MESS score >7, the incidence of tibio-peroneal trunk injury and the occurrence of postoperative deep wound infection are significant independent factors for limb loss. The presence of compartment syndrome and of ischemia time >6 hours are associated with a significantly higher risk of early reconstruction thrombosis.

Probing myosin structural conformation in vivo by second-harmonic generation microscopy.

Understanding of complex biological processes requires knowledge of molecular structures and measurement of their dynamics in vivo. The collective chemomechanical action of myosin molecules (the molecular motors) in the muscle sarcomere represents a paradigmatic example in this respect. Here, we describe a label-free imaging method sensitive to protein conformation in vivo. We employed the order-based contrast enhancement by second-harmonic generation (SHG) for the functional imaging of muscle cells. We found that SHG polarization anisotropy (SPA) measurements report on the structural state of the actomyosin motors, with significant sensitivity to the conformation of myosin. In fact, each physiological/biochemical state we probed (relaxed, rigor, isometric contraction) produced a distinct value of polarization anisotropy. Employing a full reconstruction of the contributing elementary SHG emitters in the actomyosin motor array at atomic scale, we provide a molecular interpretation of the SPA measurements in terms of myosin conformations. We applied this method to the discrimination between attached and detached myosin heads in an isometrically contracting intact fiber. Our observations indicate that isometrically contracting muscle sustains its tetanic force by steady-state commitment of 30% of myosin heads. Applying SPA and molecular structure modeling to the imaging of unstained living tissues provides the basis for a generation of imaging and diagnostic tools capable of probing molecular structures and dynamics in vivo.

New techniques in linear and non-linear laser optics in muscle research.

This review proposes a brief summary of two applications of lasers to muscle research. The first application (laser tweezers), is now a well-established technique in the field, adopted by several laboratories in the world and producing a constant stream of original data, fundamental for our improved understanding of muscle contraction at the level of detail that only single molecule measurements can provide. As an example of the power of this technique, here we focus on some recent results, revealing the performance of the working stroke in at least two distinct steps also in skeletal muscle myosin. A second laser-based technique described here is second-harmonic generation; the application of this technique to muscle research is very recent. We describe the main results obtained thus far in this area and the potentially remarkable impact that this technology may have in muscle research.