Utility of technetium-99m-methylene diphosphonate single-photon emission computed tomography/computed tomography fusion in detecting post-traumatic chronic-infected nonunion in the lower limb.

Background: This study aimed to evaluate fused images of single-photon emission computed tomography/computed tomography (SPECT/CT), stand-alone whole-body scintigraphy (WBS) and stand-alone CT in the diagnosis of post-traumatic chronic-infected nonunion osteomyelitis (OST) of the lower limb.

Patients And Methods: The imaging data from 144 patients with known/suspected chronic-infected fracture nonunion in the lower limbs following internal/external fixation between June 2015 and December 2017 were reviewed retrospectively. Technetium-99m-methylene diphosphonate SPECT/CT scans were performed on the patients. For each patient, the diagnosis on the basis of each imaging approach was classified as yes (OST), no (no OST), or equivocal by experienced nuclear medicine physicians and radiologists. An intraoperative bacterial culture experiment was conducted as our gold standard. The diagnostic sensitivity, specificity, accuracy, positive predictive value, negative predictive value, κ coefficient, significance level, and agreement level were analyzed.

Results: The diagnosis on the basis of SPECT/CT fused images showed a sensitivity of 91.3%, a specificity of 84.6%, and accuracy of 88.9% compared to that based on WBS, with a sensitivity of 52.2%, a specificity of 15.4%, accuracy of 38.9%, and CT, with a sensitivity of 65.2%, a specificity of 23.1%, accuracy of 50.0%. The fused images can show the precise sites of post-traumatic chronic-infected OST. Considerable agreement (κ 0.679) was found between the SPECT/CT diagnosis and an intraoperative bacterial culture test (WBS, κ 0.218; CT, κ = 0.184).

Conclusion: Technetium-99m-methylene diphosphonate SPECT/CT imaging fusion can improve diagnostic confidence for post-traumatic patients with chronic nonunion OST. This imaging approach can achieve an accurate diagnosis by revealing the precise location and scope of OST with high sensitivity and specificity, which has important implications for surgical guidance by providing the precise location of OST.