Purpose: The aim of this retrospective study was to assess the correlation between the occurance of iatrogenic ulnar nerve injury and frontal and saggital angular insertion of the medial pin in pediatric type 3 supracondylar humerus fractures treated with closed reduction and percutaneous fixation using a crossed-pin configuration.

Method: Among 164 patients with type 3 supracondylar humerus fractures, treated with closed reduction and percutaneous fixation using a crossed-pin configuration while the elbow was in hyperflexion, between 1999 and 2003, ninety patients (54 male and 36 female, mean age 6.1 years) with complete clinical and radiological records and follow-up period of at least 6 months were included the study. Frontal humerus-pin angle (FHPA) was the angle between the long axis of humerus and the axis of the medial pin measured on an anteroposterior radiograph. Saggital humerus-pin angle (SHPA) was the angle between the long axis of humerus and the axis of the medial pin measured on a lateral radiograph and expressed as a positive value if the medial pin direction was anteroposterior and as a negative value if the direction was posteroanterior. All the mesurements were made by the same observer blinded to the clinical records of the patients.

Results: Postoperative ulnar nerve injury was observed in 18 patients. The ulnar nerve injury group and control group were similar with respect to age and gender. Mean FHPA was 36.6 and 33.8 degrees in ulnar nerve injury and control groups respectively (p=0.270). Mean SHPA was 12.1 and 1.6 degrees in ulnar nerve injury and control groups respectively, and the difference was significant (p=0.001). All the patients with ulnar nerve injury had complete recovery within 3 months following surgery.

Conclusion: There are several methods to avoid iatrogenic ulnar nerve injury in supracondylar fractures such as insertion of two or three lateral pins, insertion of the medial pin while the elbow is less than 90 degrees of flexion. The findings of this retrospective study revealed that there was a considerable correlation between the occurence of iatrogenic ulnar nerve injury and sagittal angular insertion of the medial pin. We suggest that if a crossed-pin figuration is desired, it is better to insert the medial pin neutral or posteroanterior direction in the sagittal plane if the elbow is in hyperflexion.