Arthroscopy and irrigation control.

Saline flow through 2.2, 3.8, and 5.0 mm arthroscopes was studied by varying inflow pressure from 0 to 20 kPa, corresponding to the effect of gravity from 0 to 7 feet. The relation between knee joint distention and intraarticular pressure was studied in 25 patients under general anesthesia, and the secondary effect on gravity flow was calculated. Without distention, flow due to gravity alone was adequate through the larger arthroscopes, but diminished rapidly to low values by distending the joint. Even with a 5.0 mm arthroscope and bags at 7 feet (20 kPa), inflow was low when the joint was distended for arthroscopy. Effective clearing by high flow, combined with distention for hemostasis of capsular vessels, demands the use of a pump. Pump irrigation is most effective and also safe when controlled directly by the surgeon.