[Low frequency of missed or invisible hip fracture in X-ray examination. The rule-of-2--a simple method for quality assessment].

A new method for quality check of roentgen diagnosis of femoral neck fracture is presented. Use of the rule-of-2 means that only cases with two X-ray examinations of the hip before surgery need to be reviewed. This rule identifies a small subset which contains the false negative cases. Quality analysis of this group, approximately 10% of the material, yields all the false negatives. During the 1990's quality studies of radiography of hip fractures were performed at the University Hospital in Lund and the method later tested at the Kristianstad Central Hospital. The false negative rate was 1.6 to 2.2% in Lund and 3.5% in Kristianstad. However, the majority of the false negative cases represented fractures that were invisible even at review of the films (i.e. undisplaced fractures, impacted fractures or stress fractures). Missed diagnoses (i.e. fracture visible at review of films) were only present in 0.4 to 1%. The method presented is simple. It can be used in all hospitals that have databases for X-ray examinations and for orthopedic surgical procedures. If, in addition to conventional X-ray, MR of the hip is performed as an emergency procedure in questionable cases, the false negative rate of hip fracture diagnosis will be zero.