Radiological and biomechanical evaluation of the effects of percutaneous K wire application of the medial epicondyle on ulnar nerve

Radiological and Biomechanical Evaluation of the Effects of Percutaneous K Wire Application of the Medial Epicondyle on Ulnar Nerve Objective: To evaluate and compare the changes in ulnar nerve tension and strain at different elbow positions radiologically and mechanically before and after the application of the medial K wire. Methods: 10 fresh frozen cadaver upper extremity specimens were used in the evaluation. Using an ultrasonography and a micro strain gauge, strain and tension on the ulnar nerve were measured in 3 different elbow positions positions (elbow full extension, elbow flexion-forearm supination and elbow flexion-forearm pronation). Minimum, maximum and mean stress and strain values were compared statistically. Results: Kischner wire applied to the medial epicondyle and the measurements of the ulnar nerve on the longtidunal plane were performed. The mean values of elbows with full extension are statistically lower than the mean values in elbows with 90 degrees flexion- forearm supination and the elbows in 90 degrees flexion - forearm pronation positions. Statistical evaluations were performed between all of the groups. Elbow 90 degree flexion – forearm pronation both minimum and maximum and mean values were statistically higher in the group including the specimens with Kischner wire applied. The mean values in the elbow full extension and elbow 90 degree flexion- forearm supination positions were statistically similar in the specimens with and without the Kischner wire applied. Discussion: Although many methods were tried in an effort to prevent ulnar nerve palsy in the past, there is no consensus on a definitive treatment technique for the absolute prevention of ulnar nerve paralysis in the treatment algorithm. Thanks to the relative stability obtained after the application of the lateral Kischner wire, the application of K wire to the medial epicondyle with the elbow in a slightly extended position is a technique that can be applied to reduce the risk of ulnar nerve paralysis. Despite the application of this technique, it has been reported that ulnar nerve damage can be observed in cases where a splint is placed in the 90 degree flexion position. We argue that the position of the elbow joint in the postoperative period may contribute to VII ulnar nerve paralysis as a result of the change in the balance of the surrounding tissues through soft tissue tension and strain. In the statistical evaluation between all groups, both the minimum, maximum and mean values in the 90 degree elbow flexion-forearm pronation position were statistically higher in the specimen group where Kischner wire applied to the medial epicondyle. Therefore, as a result of our measurements, the least preferred elbow position in the postoperative period should be, is 90 degrees elbow flexion-forearm pronation. In the ultrasonographic measurements made on the nerve in the longtidunal plane in which Kischner wire was applied, the maximum values in the elbow full extension position were statistically lower than the maximum values of elbow flexion - forearm supination and elbow flexion - forearm pronation maximum. Therefore, it would be appropriate to avoid elbow flexion as much as possible, taking into account the reduction during the splint application, since the lowest maximum values that can be reached in the procedures with Kischner wire are achieved in the elbows with full extension position.