Joint Venting Prior to Hip Distraction Minimizes Traction Forces During Hip Arthroscopy

Purpose: This study evaluates the effect of venting on distraction of the hip during arthroscopy on a post-free traction table for fixed traction forces ranging from 0 to 100 pounds (lbs). Methods: Patients underwent surgery by the senior author (S.K.A.) between November 2018 and July 2019. Inclusion criteria were primary hip arthroscopy requiring central compartment access. Patients were positioned in 10-15 degrees Trendelenburg on a post-free traction table. Prior to instrumentation, fluoroscopic images of the operated hip joint were taken at 25-lb intervals from 0 to 100 lbs of axial traction. Traction was released for 15 minutes. Venting with 20 mL of air was performed and fluoroscopic images were repeated at all traction intervals. Joint displacement was measured at all intervals. An unvented control group underwent the same axial traction protocol for comparison. Results: Sixty-one consecutive patients underwent study protocol. Fifty-eight hips in 57 patients were included. Thirty-two (55.2%) were female; mean age was 31 +/- 13 years and mean body mass index was 25.7 +/- 6.2. Paired samples analysis demonstrated mean differences in distraction distance prior to and after venting of 0.27, 2.60, 4.09, 4.54, and 2.31 mm at 0, 25, 50, 75, and 100 lbs of traction, which were significant (P < .001) at all traction intervals. Significantly more vented hips distracted at least 10 mm at 25-100 lbs traction (P < .001). An unvented control group showed no significant differences between the first and second traction application. Conclusions: Venting prior to applying traction on a post-free traction table increases the distraction distance achieved for a given traction force at multiple levels of traction in comparison to the pre-vented state. Our results suggest venting the hip joint prior to the application of traction may serve to reduce the maximal amount of traction required to safely instrument the hip arthroscopically. Level of Evidence: IV, case series.