Low Positive Predictive Value of Bone Scan to Predict Impending Complete Fracture among Incomplete Atypical Femoral Fracture

Abstract

BackgroundAlthough bone scan might be useful to detect incomplete atypical femoral fractures (AFFs) earlier than radiographs, there is no study on predicting further progression to a complete fracture among incomplete AFFs. Our purposes are to determine whether bone scan detects impending complete fracture among incomplete AFFs.MethodsWe reviewed 18 patients (20 AFFs) who underwent bone scan at the diagnosis of incomplete AFF and were not treated with prophylactic fixation. A diagnosis of impending complete fracture was made, when the femur completely fractured within 6 months after the scan. We correlated radioisotope uptake with the impending complete fracture to calculate sensitivity, specificity, positive predictive value and negative predictive value of bone scan.ResultsThirteen AFFs (65%, 13/20) showed a positive uptake in bone scan. Among the 13, only one femur was completely fractured within 6 months. None of the 7 femurs without uptake in bone scan fractured. In diagnosing impending complete fracture, the sensitivity of bone scan was 100% and negative predictive value was 100%. However, the specificity (36.8%) and positive predictive value (7.7%) were quite low.ConclusionBone scan has no significant role in detecting the impending complete fracture, and a positive uptake does not mean the necessity of prophylactic fixation of incomplete AFF.

Fraturas atípicas do fêmur associadas ao uso crônico de bisfosfonatos: Uma série de casos de 66 pacientes

“…Authors attribute these findings to the biological effect of bisphosphonate and to a reduction leaving a small diastasis at the fracture focus in some cases. 17,19,20 The average age described in the literature for patients with atypical femur fractures is $ 75 years old, 6 as in our study. Nevertheless, despite affecting elderly patients, atypical femur fractures are not associated with an increased mortality.…”

“…Alguns estudos citam tempo prolongado de consolidação nas fraturas incompletas tratadas de forma não operatória, bem como em fraturas completas submetidas ao tratamento operatório, o que os autores atribuem, além do efeito biológico do bisfosfonato, ao fato de que em alguns casos houve redução com pequena diástase no foco da fratura. 17,19,20 A idade média descrita na literatura dos pacientes portadores das fraturas atípicas do fêmur é de $ 75 anos, 6 assim como foi verificado no presente estudo. Porém, apesar de acometer pacientes idosos, as fraturas atípicas do fêmur não estão associadas ao aumento da mortalidade.…”

“…Alguns estudos citam tempo prolongado de consolidação nas fraturas incompletas tratadas de forma não operatória, bem como em fraturas completas submetidas ao tratamento operatório, o que os autores atribuem, além do efeito biológico do bisfosfonato, ao fato de que em alguns casos houve redução com pequena diástase no foco da fratura. 17 19 20…”

“…Authors attribute these findings to the biological effect of bisphosphonate and to a reduction leaving a small diastasis at the fracture focus in some cases. 17 19 20…”