The purpose of this article was to use finite element analysis (FEA) to study the relationship of tibial tunnel (TT) with fracture pattern and implants. A computed tomography scan of full-length tibia and fibula was obtained. Models were built after three-dimensional reconstruction. The corresponding plates and screws were constructed and assembled together with fracture models. FEA was performed and contourplots were output. The Von Mises stresses of nodes and displacements of elements were extracted. Student’s t test was used to compare the values of Von Mises stresses and displacements between corresponding models. Differences in Von Mises stresses and displacements of fragments and implants between models with and without TT were nearly all statistically significant. However, the displacements of fragments and implants for all models were < 2 mm. TT in fracture models had larger Von Mises stresses than TT in intact tibial model. However, displacements of TT in fracture models showed similar or even smaller results to those in intact tibial model. Although almost all the tested parameters were statistically significant, differences were small and values were all below the clinical threshold. This study could promote open reduction and internal fixation with one-stage reconstruction for treatment of tibial plateau fractures associated with anterior cruciate ligament (ACL) ruptures.

We built a joint replacement loosening model based on the original rabbit model of infection and evaluated the performance characteristics of ¹⁸F-FDG and ⁶⁸ Ga-FAPI in evaluating infection and loosening. After surgery, the rabbits were divided into four groups, with six individuals in the control group and 10 each in the aseptic loosening, S. aureus and S. epidermidis groups. PET/CT and serological examination were performed three times at two-week intervals. After the rabbits were euthanized, micro-CT, tissue pathology, pullout tests and scanning electron microscopy (SEM) were performed. The pullout test and SEM showed the feasibility of the aseptic loosening model. ¹⁸F-FDG showed similar performance in the control and loosening groups. The SUVmax of the S. aureus group was consistently higher than that of the S. epidermidis group. As for ⁶⁸ Ga-FAPI, the SUVmax of the control group was lowest in the second week and gradually increased over subsequent weeks. The SUVmax of the loosening group began to exceed that of the control group after the second week. The SUVmax of the S. aureus group in the second week was the lowest among the four groups and increased as the number of weeks increased. The pathology results showed concordance with the performance of PET/CT. Linear regressions between SUVmax and serology showed that ¹⁸F-FDG was positively correlated with CRP and IL-6, while ⁶⁸ Ga-FAPI revealed negative correlations with CRP and IL-6 in the second week and positive correlations in the sixth week. In addition, the SUVmax and MT(target)V of both ¹⁸F-FDG and ⁶⁸ Ga-FAPI were negatively correlated with bone volume/trabecular volume (TV) and bone surface area/TV. In this longitudinal observation, ⁶⁸ Ga-FAPI showed greater sensitivity than ¹⁸F-FDG in detecting diseases, and ⁶⁸ Ga-FAPI had no intestinal or muscular uptake. The MT(target)V of ⁶⁸ Ga-FAPI was larger than that of ¹⁸F-FDG, which meant that ⁶⁸ Ga-FAPI had the potential to define the scope of lesions more accurately. Finally, the SUVmax of ⁶⁸ Ga-FAPI could not differentiate between loosening and infection; further study of the diagnostic criteria is warranted.

We evaluate the O6-methylguanylmethyltransferase (MGMT) methylation status noninvasively by analyzing radiomics features of 11C-methionine (MET) PET images, which may reflect the detailed biological properties of gliomas. Fifty-seven patients with histopathologically confirmed gliomas, who were initially examined with 11C-MET PET/MR were retrospectively enrolled. Quantitative uptake of MET was assessed using conventional, histogram and texture features. These features were compared between the two groups classified by MGMT promoter methylation status. The histogram features (Skewness and Kurtosis) of the MGMT methylated group were significantly higher than those of the MGMT unmethylated group (Skewness: 0.90±0.71 vs. 0.49±0.45; P=0.01) (Kurtosis: 1.36±2.30 vs. 0.08±0.65; P=0.003), but there were no significant differences in Skewness or Kurtosis between the groups in glioma-grade-matched subgroup analysis. Moreover, there was no significant difference in other features between the methylated group and unmethylated group. The histogram features (Skewness and Kurtosis) of MET PET/MRI may be two key indicators to detect MGMT methylation status in gliomas and valuable predictors for the clinical responses of patients scheduled to receive temozolomide chemotherapeutics.

Background: The diagnosis of a periprosthetic joint infection (PJI) is always a difficult point in research on the surgery of joints. The current diagnostic criteria include a comprehensive analysis of multiple tests; however, there are no effective visual examinations yet that can differentiate between aseptic loosening and the PJI.Case presentation: This case report describes four patients with symptomatic total hip arthroplasty (THA), two cases of loosening and two cases of infection. Although the four cases were correctly diagnosed by the tissue culture, preoperative tests and pathological examination could not effectively distinguish an infection from a non-infection. Based on a preclinical study and theoretical feasibility, gallium-68 (⁶⁸Ga)-labeled fibroblast activation protein inhibitor positron emission tomography/computed tomography (⁶⁸Ga-FAPI PET/CT) was performed. Through ⁶⁸Ga-FAPI PET/CT scanning, not only were the causes diagnosed correctly but the lesions were also located.Conclusion: When the lesion is located between the bone and the prosthesis, ⁶⁸Ga-FAPI PET/CT could differentiate aseptic loosening from periprosthetic joint infection (PJI). ⁶⁸Ga-FAPI PET/CT has clear advantages over routine examinations and has a prospective application in detecting PJI.

Purpose: The existing periprosthetic joint infection (PJI) models have obvious limitations, and studies of PJI on animal models using PET/computed tomography (CT) for diagnosis are still lacking. Thus, the aim of this study was to establish a new PJI model and ¹⁸F-fluorodeoxyglucose (FDG) and ⁶⁸Ga-fibroblast activation protein inhibitor (FAPI) were employed to study their performance. Methods: A novel PJI model of rabbit was developed by placing two screws in the tibia and femur. Based on bacteria concentration, the animals were divided into five groups, control, 10⁴, 10⁵, 10⁶ and 10⁷. ¹⁸F-FDG and ⁶⁸Ga-FAPI PET/CT were performed continuously in next 2 weeks and maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean), metabolic target volume (MTV) and total lesion glycolysis/total lesion fibrosis were calculated as the metrics. Results: As for SUV_max, all data of ¹⁸F-FDG were larger than that of ⁶⁸Ga-FAPI in the same group for both weeks. For the performance of ¹⁸F-FDG, no definitive conclusion could be drawn for SUV_max and SUV_mean. As for ⁶⁸Ga-FAPI, the 10⁴ group was significantly larger than 10⁵, 10⁶ and 10⁷ groups for SUV_max and SUV_mean in both weeks (P < 0.05). MTV of ⁶⁸Ga-FAPI was found to be almost always larger than that of ¹⁸F-FDG in the same group. Conclusion: The mechanism of ⁶⁸Ga-FAPI is totally different from ¹⁸F-FDG and this unique property of ⁶⁸Ga-FAPI shows a promising prospect in detecting infection boundary and may even distinguish a small number or a large number of bacterial infections.