Supracondylar humeral fractures are the most common elbow injury in children, usually sustained from a fall on the outstretched hand. Iatrogenic ulnarnerve injury is not uncommon following cross K wiring. NNH is the number of cases needed to treat in order to have one adverse outcome. A systemic review was undertaken to calculate relative risks, risk difference and number needed to harm following management of supracon-dylar fractures with cross or lateral K wires. It was found that there was one iatrogenic ulnar nerve injury for every twenty-seven cases that were managed with crossed K wires. The aim of this study was to calculate the number of cross K wiring of supracondylar fractures of the humerus that would need to be performed for one iatrogenic ulnar nerve injury to occur. Iatrogenic ulnarnerve injury is not uncommon following cross K wiring of supracondylar fractures of the humerus. To date there are no clinical trials showing the benefit of cross K wiring over lateral K wiring in the management of supracondylar fractures of the humerus in children. If it can be confirmed that lateral K wiring is as effective as crossed K wiring, iatrogenic ulnar nerve injury can be avoided. A systematic review of iatrogenic ulnar nerve injuries following management of supracondylar fractures was conducted. The databases MEDLINE 1966 – present, EMBASE 1980 – present, CINAHL 1982 – present, CDSR, and DARE were searched along with a meticulous search of the Journal of Paediatric Orthopaedics from 1998 to 2004. Of the two hundred and forty-eight papers identified, only thirty-six met the inclusion criteria. The papers where both lateral crossed K wires were used as treatment were identified for calculating relative rates, risk difference and number needed to harm. NNH was 7.69. When a sensitivity analysis removing two studies that had five subjects or fewer and a 100% ulnar nerve injury rate was peformed, the NNH was 27.7. In other words, there was one iatrogenic ulnar nerve injury for every twenty-seven cases that were managed with crossed K wires.
