Intraoperative frozen section analysis for detection of fracture-related infection in nonunion of the upper limb. Diagnostic accuracy study.

Introduction: During revision surgery for the management of patients presenting with long-bone upper extremity nonunion, it is crucial to rule out fracture-related infection (FRI). This is especially true if there are clinical signs suggestive of FRI, or if there is a history of prior FRI, open wound fracture, or surgery. This study aimed to determine the efficacy of frozen section analysis (FSA) in providing real-time diagnosis of FRI in patients with upper-limb long-bone nonunion undergoing revision surgery.

Patients And Methods: We included previously surgically treated patients who underwent revision surgery for chronic/late-onset nonunion of the long bones of the upper limbs over a 9-year period. We retrospectively applied the FRI criteria to identify eligible patients and recorded their clinical features and demographic characteristics. In all included patients, samples for microbiological analysis and FSA were collected simultaneously during revision surgery. Patients were categorized according to intraoperative culture results as having aseptic or infected nonunion. The sensitivity, specificity, positive and negative predictive values, and accuracy of FSA test were calculated and compared using microbiological analysis as the reference standard test. The concordance rate between FSA and definitive histopathology was also determined.

Results: Sixty-two patients who were surgically treated for nonunion of the arm or forearm were included in this study. Septic nonunion was diagnosed intraoperatively in 9 patients based on FSA findings, while microbiological analysis confirmed septic nonunion in 8 patients. The sensitivity and specificity of FSA were 88 % (95 % confidence interval [CI] [47, 100]) and 96 % (95 % CI [87, 100]), respectively. Positive and negative predictive values were 78 % (95 % CI [47, 93]) and 98 % (95 % CI [89, 100]), respectively, with an overall test accuracy of 95 % (95 % CI [87, 99]). Cohen's Kappa coefficient between FSA and definitive histopathology was 0.74 (95 % CI [0.5, 1]).

Conclusions: FSA showed high sensitivity and specificity for the detection of active infection during revision surgery for nonunion of the upper limb. Owing to its high negative predictive value, it can reliably rule out active infections during revision surgery. Since the results are obtained immediately during revision surgery, this approach offers the significant advantage of enabling real-time decision-making.