gms | German Medical Science

Objectives: Incomplete atypical femoral fractures (AFFs) are at risk of progressing into a complete fracture. Although impending complete fractures require prophylactic fixation, there is lack of study on predicting complete fracture among the incomplete AFFs. We developed a scoring system to predict progression into a complete fracture and evaluated its reliability and validity.

Methods: We retrospectively reviewed 46 incomplete AFFs in 44 patients, who did not undergo prophylactic fixation. Among these 46 incomplete fractures, 13 developed a complete fracture within the subsequent 6 months. Clinical information and radiographs were evaluated to identify risk factors of complete fracture within 6 months. A weighted scoring system, including four identified risk factors; the site, severity of pain, status of the contralateral femur, and the extent of radiolucent line, was developed. We evaluated the inter-observer reliability of the system among 3 independent observers by using Intraclass Correlation Coefficiency (ICC) and compared its accuracy with those of each single risk factor using Receiver Operator Characteristic (ROC) curve. The validity of the scoring system was tested in a different cohort of 35 incomplete AFFs in 30 patients.

Results: The mean score was 6.3 ± 1.2 in the non-fracture group and 10.1 ± 1.7 in the fracture group (p<0.001). The probability increased abruptly when the score was 8 points or more. The proposed scoring system showed an almost perfect reliability (ICC, 0.997; 95% CI, 0.995 to 0.998), and higher accuracy than any single risk factor in ROC curve. In the different series for the validity test, the positive predictive value for impending complete fracture was 100% and the sensitivity was 75%, when cut-off value was 8 points.

Conclusion: The progression to complete fracture could be predicted by using our scoring system. Incomplete AFF with scores < 8 points can be treated conservatively, while lesions with scores ≥ 8 require prophylactic fixation.