Intra-Articular Pressures of the Canine Stifle and Shoulder Joints during Arthroscopy: A Cadaveric Study

Objectives The aims of this study were to evaluate intra-articular pressure (IAP) upon injection of 10 mL of saline in the canine stifle and shoulder and to evaluate the discrepancy between fluid pump pressure setting and IAP during arthroscopy. Study Design Arthroscopy of 14 cadaveric canine stifles and 14 shoulders was performed with a 3.0-mm arthroscope. Intra-articular pressure was measured with an 18G needle connected to an anaesthetic invasive blood pressure monitor. Readings were obtained (1) in the unadulterated joint, (2) upon injection of 10 mL of saline, (3) every minute thereafter. After the initial two IAP readings, the pressure increased by 10 mm Hg between 30 and 100 mm Hg at a rate of 10 mm Hg every 2 min. Results Saline distention IAP in the stifle were lower than in the shoulder joint, with shoulder joint IAP exceeding 180 mm Hg, which is the proposed human capsular plastic deformation pressure. All fluid pump pressures were significantly lower than measured IAP (p ≤ 0.0001), with the magnitude of difference increasing with pump pressure. Conclusion Saline distention of the shoulder should be done with minimal fluid. Intra-articular pressure can be expected to exceed fluid pump pressure significantly during arthroscopy. At lower pump pressures, the difference between pump pressures and IAP is smaller than at higher pump pressures.