Early assessment of extremity compartment syndrome by biochemical markers in a rat model.

BACKGROUND: This experimental study aimed to define a biochemical marker that will enable early diagnosis of acute compartment syndrome (ACS) of extremities, a mortal condition that occurs due to trauma. METHODS: A total of 15 Wistar rats were included in the study in which saline infusion technique, a clinically compatible ACS model, was applied. After the rats were anesthetized with ketamine-xylazine, the in-compartment pressure of the hind limb was slowly increased with saline delivered through the angiocatheter, and after reaching the target compartment pressure, the pressure level was kept with a rubber tourniquet. The in-compartment pressure level was continuously monitored with a pressure transducer. The rats were divided into three groups. No intervention was applied to the control group (CG) (n = 3). In study group 1 (SG1) (n = 6), ACS was created using the saline infusion technique, keeping the in-compartment pressure between 30 and 40 mmHg for 45 min. In study group 2 (SG2) (n = 6), ACS was created using the saline infusion technique, keeping the in-compartment pressure between 30 and 40 mmHg for 90 min. Fasciotomy was performed on all rats. Tissue samples were obtained for histopathological examination and blood samples for biochemical analysis. RESULTS: Total oxidant status (TOS) (p = 0.004), ischemia-modified albumin (IMA) (p = 0.030), aspartate transferase (AST) (p = 0.003) and neopterin (p = 0.012) levels differed significantly between groups in the early period of muscle ischemia. In fact, TOS levels differed significantly between the groups even in the cellular phase where signs of ischemia were not observed (p = 0.048, p = 0.024). According to histopathological evaluation, there was no significant difference between the groups. DISCUSSION: TOS can be detected in the early reversible stage of ischemia, when the histopathological findings of ACS do not occur.

Microwave tomography for functional imaging of extremity soft tissues: feasibility assessment.

It is important to assess the viability of extremity soft tissues, as this component is often the determinant of the final outcome of fracture treatment. Microwave tomography (MWT) and sensing might be able to provide a fast and mobile assessment of such properties. MWT imaging of extremities possesses a complicated, nonlinear, high dielectric contrast inverse problem of diffraction tomography. There is a high dielectric contrast between bone and soft tissue in the extremities. A contrast between soft tissue abnormalities is less pronounced when compared with the high bone-soft tissue contrast. The goal of this study was to assess the feasibility of MWT for functional imaging of extremity soft tissues, i.e. to detect a relatively small contrast within soft tissues in closer proximity to high contrast boney areas. Both experimental studies and computer simulation were performed. Experiments were conducted using live pigs with compromised blood flow and compartment syndrome within an extremity. A whole 2D tomographic imaging cycle at 1 GHz was computer simulated and images were reconstructed using the Newton, MR-CSI and modified Born methods. Results of experimental studies demonstrate that microwave technology is sensitive to changes in the soft tissue blood content and elevated compartment pressure. It was demonstrated that MWT is feasible for functional imaging of extremity soft tissues, circulatory-related changes, blood flow and elevated compartment pressure.

An experimental assessment of the risk of compartment syndrome during knee arthroscopy.

The purpose of this study was to objectively evaluate the risk of compartment syndrome as a complication during arthroscopy, particularly with the use of mechanical infusion systems. Little experimental data are available. This study shows that when elevated compartment pressures occur, extravasated fluid dissipates quickly, minimizing the risk of compartment syndrome and subsequent neuromuscular damage. Twelve live pig hind limbs (six swine) were used. Three additional limbs were used as shams. After anesthesia and portal placement for mechanical fluid infusion, two standardized capsulotomies were created to allow free extravasation of fluid. We dynamically monitored intraarticular pressure, and intracompartmental pressure in the anterior (leg), deep posterior (leg), and quadriceps (thigh) compartments. Nerve conduction studies were performed on the tibial and peroneal nerves. Data collection began at the onset of fluid infusion and continued after infusion ceased until elevated compartment pressures fell below 20 mm Hg. There were two study variables: intraarticular pressure (100, 150, or 200 mm Hg) and time of fluid ingress (30, 60, or 90 minutes). Following this, the swine were evaluated serially for 13 to 16 days. Repeat nerve conduction studies, muscle biopsies (in the three previously mentioned compartments), and electromyography were performed 13 to 16 days following the operation. Maximum compartment pressures during fluid infusion averaged 78.75 mm Hg. Significant variability existed when comparing the interrelationships of infusion time, maximum compartment pressures, time of resolution of elevated pressures, and intraarticular pressures. Most importantly, elevated compartment pressures resolved quickly (mean, 25.5 minutes; range, 0 to 100 minutes; n = 36 compartments) when stopping fluid infusion. Nerve conduction studies were normal on all postoperative studies. Electromyographic (EMG) analysis showed normal study results in the biceps, gracilis, abductor digiti quinti, and adductor digiti segundi. Although EMG analysis of the tibialis anterior and extensor digitorum brevis showed 1+ fibrillation (1+ to 4+ scale), this was seen in sham studies with tourniquet alone (no fluid infusion). Muscle biopsies were without evidence of myonecrosis. Finally, 5 of 6 swine ambulated without difficulty on the first postoperative day, whereas 1 swine limped for 2 days. All swine were normal by the 3rd postoperative day and also at the end of the study. These data show that in this model, the risk of developing sequela from compartment syndrome during arthroscopy is minimal, even when there exists significant fluid extravasation and elevated compartment pressures.