Background: Available conventional tibial tubercle lateralization (TTL) parameters fail to account for individual patient size or anatomy. Purposes: To evaluate the predictive ability of individualized TTL parameters and clarify the best predictor of patellar dislocation (PD) and to determine the relationship of the best predictor with other risk factors of PD with quadriceps isotonic contraction. Study Design: Cohort study (diagnosis); Level of evidence, 2. Methods: A total of 15 patients with PD (28 knees) and 14 controls (28 knees) underwent 4-dimensional computed tomography, and the image with the knee fully extended and quadriceps isotonically contracted was selected for evaluation. The following TTL parameters were measured on the images: tibial tubercle–trochlear groove (TT-TG) distance, tibial tubercle–Roman arch distance, and tibial tubercle–posterior cruciate ligament distance, as well as their ratios to femoral condylar width and patellar width (PW). In addition, the following parameters were measured: Insall-Salvati ratio, Blackburne-Peel ratio, Caton-Deschamps ratio, modified Insall-Salvati ratio, bisect offset index, congruence angle, lateral patellar tilt, lateral trochlear inclination, sulcus depth, sulcus angle, trochlear groove medialization, patella–patellar tendon angle, patellofemoral axis angle (P-FAA), patellar articular facet–patellar tendon angle, patellar articular facet–femoral axis angle (PA-FAA), and patellar shape according to Wiberg type. The area under the receiver operating characteristic curve (AUC) was calculated to access the diagnostic accuracy of the TTL parameters for PD, and the TTL parameters with high diagnostic ability were evaluated for correlation with the remaining parameters. Results: The TT-TG/PW ratio had the best diagnostic ability for PD (AUC = 0.890). The TT-TG/PW ratio was positively correlated with bisect offset index, congruence angle, lateral patellar tilt, P-FAA and PA-FAA ( r = 0.610, 0.465, 0.635, 0.553 and 0.418, respectively; P≤ .027 for all), and TT-TG/PW ratio was greater in knees with type II versus type III patella ( P = .017). Conclusion: With the knee fully extended and quadriceps isotonically contracted, the TT-TG/PW ratio was found to be the best predictor of PD and reflected individualized TTL, which helps with clinical preoperative planning.

The X-Ray machine serves as a crucial auxiliary tool in surgical settings, collaborating with surgical navigation systems to facilitate intra-operative 2D fluoroscopic image navigation and provide a reliable foundation for 2D-3D registration navigation technology. The attainment of precise navigation for both 2D fluoroscopic images and 3D preoperative CT/MRI images hinges upon the efficient and accurate calibration of X-Ray machine. Conventional calibration techniques for X-Ray machine, whether conducted online or offline, are characterized by excessively intricate calibration processes, imposing significant time demands during surgery and resulting in diminished surgical efficiency. We propose a novel permanent calibration ( PerCal ) strategy employing a self-developed X-Ray Source Tracker ( TRKR-S ), Image Plate Tracker ( TRKR-IP ) and Portable Calibrator ( CALP ), aiming to streamline surgical procedures and enhance overall surgical efficiency. This strategy reframes the X-Ray machine calibration challenge into the determination of the spatial position of the X-Ray source in relation to TRKR-S and the 2D fluoroscopic image relative to TRKR-IP . In the intra-operative navigation scenario, solely collecting position information of TRKR-S and TRKR-IP under the optical camera during perspective scanning enables real-time and precise intra-operative 2D fluoroscopic image navigation. Meanwhile, the initialization mechanism for projection coordinate frame ( IM-Proj ) has been proposed to ensure the effective solution of the PerCal problem. Furthermore, the Membership Criterion for 2D/3D marker points ( MC-2D/3D ) has been formulated with the aim of expeditiously and precisely determining the mapping correlation between spatial marker points within the 3D calibration scene and their corresponding marker points on the 2D fluoroscopic image. The efficacy of the proposed PerCal strategy combining IM-Proj and MC-2D/3D is validated through ablation experiments using a G-Type Arm, confirming its calibration accuracy and timeliness. The AMSE errors for frontal and lateral perspectives were denoted as 0.332±0.026mm and 0.53±0.023mm, respectively. Notably, it necessitates only one calibration session to attain permanent reuse of calibration data in spinal surgery navigation. The navigation registration time is confirmed not to exceed 10 seconds, affirming the accuracy and efficiency of PerCal .

Objectives: To propose a reliable and standard 3D assessment method to analyze the effect of weight-bearing (WB) status on the location of patella and clarify the diagnostic performance of 3D parameters for recurrent patellar dislocation (RPD) in WB and non-weight-bearing (NWB) conditions. Methods: Sixty-five knees of RPD patients and 99 knees of controls were included. Eight landmarks, two lines and a coordinate system were defined on 3D bone models of knees based on weight-bearing CT and non-weight-bearing CT. The shift and tilt of patella in three orthogonal axes (X_shift, Y_shift, Z_shift, X_tilt, Y_tilt, Z_tilt) were evaluated. Results: X_shift and Y_shift were significantly higher, Z_shift, X_tilt and Y_tilt were significantly lower in WB condition than NWB condition (p < 0.001, p < 0.001, p = 0.001, p = 0.002, p = 0.010). In both WB and NWB conditions, X_shift, Y_shift and Z_tilt were significantly higher, and X_tilt was significantly lower in the RPD group than the control group (WB/NWB: p < 0.001/p = 0.002, p < 0.001/p = 0.001, p < 0.001/p < 0.001, p < 0.001/p = 0.009). In WB condition, Z_shift and Y_tilt were significantly higher in the RPD group than the control group (p = 0.011, p < 0.001). Z_tilt had the best diagnostic performance for RPD in both WB and NWB conditions, with AUC of 0.887 (95% CI: 0.828, 0.946) and 0.885 (95% CI: 0.822, 0.947), respectively. Conclusions: The 3D measurement method reliably and comprehensively reflected the relative spatial position relationship of the patellofemoral joint. It can be applied to the 3D preoperative planning of patellofemoral procedures. In addition, patellofemoral evaluation under the WB condition was essential to detect subtle underlying risk factors for RPD, with axial lateral patellar tilt being the best predictor. Critical relevance statement: This 3D measurement method under weight-bearing conditions contributes to comprehensively describing the relative spatial position of the patellofemoral joint in a standardized way and can be applied to preoperative evaluation for recurrent patellar dislocation. Key Points: Patellofemoral alignment is a 3D problem, and the accuracy of 2D parameters has been questioned. 3D measurement was reliable and comprehensively reflected relative spatial relationships of the patellofemoral joint. 3D measurements under weight-bearing condition help preoperative evaluation for RPD. Graphical

The quadriceps during activities mainly affect patellar movement in the sagittal plane. This study was to analyze the pattern of sagittal patellar tilt in patellofemoral pain (PFP) patients by four-dimensional computed tomography (4DCT). Thirty-four knees of PFP patients and 34 control knees were scanned with 4DCT. Patella-patellar tendon angle (P-PTA), patella-lateral tibial plateau angle (P-LTPA), patella-screen horizontal line angle (P-SHLA), articular facet of the patella-lateral tibial plateau angle (PA-LTPA), articular facet of the patella-screen horizontal line angle (PA-SHLA), and upper margin of the patella-quadriceps tendon angle (PU-QTA) were used to evaluate the sagittal patellar tilt. Two-factor repeated-measures ANOVA was used to compare all parameters between the two groups. At 30°−40° of flexion, P-PTA was significantly lower in PFP group than in control group (p = 0.004). At 0°–10°, PU-QTA was significantly higher in PFP group than in control group (p = 0.027). During flexion and extension, P-SHLA and PA-SHLA were significantly higher in PFP group than in control group, but there were no significant differences in P-LTPA and PA-LTPA. From − 10° to 30°, P-PTA decreased as the knee flexion angle increased. PU-QTA, P-LTPA, and PA-LTPA also decreased as the knee flexion angle increased, but P-SHLA and PA-SHLA increased. In PFP group, sagittal patellar tilt was abnormal, and patella showed anterior tilt relative to the screen horizontal line during active knee flexion and extension. The pattern of patellar sagittal motion during dynamic process was consistent between PFP and control groups. The characteristics of patellofemoral sagittal alignment should not be ignored when analyzing patellofemoral stability.

Periprosthetic joint infection (PJI) is a major complication following total hip arthroplasty (THA), posing significant diagnostic challenges. This study prospectively evaluated 114 patients from January 2021 to August 2023, including those with PJI and aseptic loosening, using computed tomography (CT) to count enlarged inguinal lymph nodes with a short-axis diameter greater than 5 mm as assessed by two blinded radiologists. Patients with PJI had significantly higher lymph node counts (median 4.5, range 1–13) compared with those with aseptic loosening (median 1, range 0–5). Using a threshold of more than 2.5 enlarged nodes, CT achieved 86.8% sensitivity and 85.5% specificity, with an area under the curve (AUC) of 0.91, which was superior to conventional markers such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). These findings suggest that CT-based enlarged inguinal lymph node counting is a simple, non-invasive, and accurate method for diagnosing PJI, and may enhance current diagnostic strategies. Trial registration number: No. ChiCTR2100050785.