Abstract
Introduction It has been shown that venting decreases the forces required to distract the hip, however, it is unknown how venting may impact hip distractibility at higher traction forces. Our purpose was to determine the impact venting has on hip distractibility at a wide range of traction forces. Methods Nine cadaveric hemi-pelvises were included in the analysis, and mounted on an axial traction table. Fluoroscopic shots were taken at 12.5 pound (lbf) intervals from 0 up to 200 lbf in two states: (1) prior to any instrumentation or venting (native) and (2) after the hip had been vented with 10 mL of air. Joint space was calculated in millimeters at each force interval in both capsular states. The force at which each hip achieved initial distraction (defined as >3 mm of an increase in joint space) and the final joint space at 200 lbf was recorded and averaged in both groups. Comparisons were made via paired T-tests. Results Seven male hips and two female hips were used in this study. Mean force required to achieve >3 mm of an increase in joint space was 56.9 +/- 25.1 lbf in the native state and 19.4 +/- 9.1 lbf in the vented state (P=<0.001), a 66% mean reduction in force. At 200 lbf, mean joint space was 13.3 +/- 2.65 mm in the native state and 14.2 +/- 2.53 (P=0.001) in the vented state. Conclusions Venting of the hip decreases the force required to achieve adequate distraction by 66% and increases the total amount of distraction in the hip even at high distractive forces.