AN EXPERIMENTAL ASSESSMENT OF THE RISK OF COMPARTMENT SYNDROME DURINGKNEE ARTHROSCOPY

The purpose of this study was to objectively evaluate the risk of comp artment syndrome as a complication during arthroscopy, particularly wi th the use of mechanical infusion systems. Little experimental data ar e 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 ex travasation of fluid. We dynamically monitored intraarticular pressure , and intracompartmental pressure in the anterior (leg), deep posterio r (leg), and quadriceps (thigh) compartments. Nerve conduction studies were performed on the tibial and peroneal nerves. Data collection beg an at the onset of fluid infusion and continued after infusion ceased until elevated compartment pressures fell below 20 mm Hg. There were t wo study variables: intraarticular pressure (100, 150, or 200 mm Hg) a nd time of fluid ingress (30, 60, or 90 minutes). Following this, the swine were evaluated serially for 13 to 16 days. Repeat nerve conducti on studies, muscle biopsies (in the three previously mentioned compart ments), and electromyography were performed 13 to 16 days following th e operation. Maximum compartment pressures during fluid infusion avera ged 78.75 mm Hg. Significant variability existed when comparing the in terrelationships of infusion time, maximum compartment pressures, time of resolution of elevated pressures, and intraarticular pressures. Mo st importantly, elevated compartment pressures resolved quickly (mean, 25.5 minutes; range, 0 to 100 minutes; n = 36 compartments) when stop ping fluid infusion. Nerve conduction studies were normal on all posto perative 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 ex tensor digitorum brevis showed 1+ fibrillation (1+ to 4+ scale), this was seen in sham studies with tourniquet alone (no fluid infusion). Mu scle biopsies were without evidence of myonecrosis. Finally, 5 of 6 sw ine ambulated without difficulty on the first postoperative day, where as 1 swine limped for 2 days. All swine were normal by the 3rd postope rative day and also at the end of the study. These data show that in t his model, the risk of developing sequela from compartment syndrome du ring arthroscopy is minimal, even when there exists significant fluid extravasation and elevated compartment pressures.