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.