[ 18 F]FDG PET accurately differentiates infected and non-infected non-unions after fracture fixation

Abstract

Purpose

Complete fracture healing is crucial for good patient outcomes. A major complication in the treatment of fractures is non-union. The pathogenesis of non-unions is not always clear, although implant-associated infections play a significant role, especially after surgical treatment of open fractures. We aimed to evaluate the value of [¹⁸F]FDG PET in suspected infections of non-union fractures.

Methods

We retrospectively evaluated 35 consecutive patients seen between 2000 and 2015 with suspected infection of non-union fractures, treated at a level I trauma center. The patients underwent either [¹⁸F]FDG PET/CT (N = 24), [¹⁸F]FDG PET (N = 11) plus additional CT (N = 8), or conventional X-ray (N = 3). Imaging findings were correlated with final diagnosis based on intraoperative culture or follow-up.

Results

In 13 of 35 patients (37 %), infection was proven by either positive intraoperative tissue culture (N = 12) or positive follow-up (N = 1). [¹⁸F]FDG PET revealed 11 true-positive, 19 true-negative, three false-positive, and two false-negative results, indicating sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of 85 %, 86 %, 79 %, 90 %, and 86 %, respectively. The SUV_max was 6.4 ± 2.7 in the clinically infected group and 3.0 ± 1.7 in the clinically non-infected group (p <0.01). The SUV_ratio was 5.3 ± 3.3 in the clinically infected group and 2.6 ± 1.5 in the clinically non-infected group (p <0.01).

Conclusion

[¹⁸F]FDG PET differentiates infected from non-infected non-unions with high accuracy in patients with suspected infections of non-union fractures, for whom other clinical findings were inconclusive for a local infection. [¹⁸F]FDG PET should be considered for therapeutic management of non-unions.

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