EFFECTS OF SUPINE POSITIONING AND FRACTURE POST PLACEMENT ON THE PERINEAL COUNTERTRACTION FORCE IN AWAKE VOLUNTEERS

An instrumented traction post was used to determine the magnitude and direction of the countertraction force applied to the perineum of 15 a wake volunteers for a series of 12 positions used in fracture surgery and compared with their corresponding neutral position controls. The r esults demonstrated that adduction of the affected limb and abduction of the contralateral limb applied the greatest force to the perineum w ith ipsilateral and contralateral placement of the fracture post. Thes e two maneuvers increased the perineal countertraction force 80% above their respective neutral readings. Abduction of the affected limb red uced the traction force by 50% with ipsilateral and contralateral plac ement of the fracture post. Flexion-abduction-external rotation of the contralateral leg reduced the forces applied to the perineum by 60% w hen the fracture post was placed contralateral to the affected limb. C ontralateral placement of the post decreased the perineal countertract ion force 46% below the value for ipsilateral post placement for this maneuver. Internal and external rotation of the affected limb had no e ffect on the perineal countertraction force for either placement of th e post. There was a significant decrease in the perineal forces for th e neutral positions after adduction of the affected limb and abduction of the contralateral limb with ipsilateral placement of the post, ind icating that the volunteers shifted on the fracture table in response to pain. There was no significant difference in the direction of the c ountertraction force for the various positions. The results of this st udy suggest that positioning the affected limb in slight abduction dur ing surgery and avoiding adduction of the affected limb or abduction o f the unaffected limb may reduce the incidence of iatrogenic pudendal nerve palsy associated with intraoperative traction.