The distal part of the radius is the most common localisation of fractures of the human body. Dislocated intraarticular fractures of the distal radius (FDR) are frequently treated by open reduction and internal fixation with a volar locking plate (VLP) under fluoroscopic guidance. Typically the locking screws are placed subchondral near the joint line to achieve maximum stability of the osteosynthesis. To avoid intraarticular screw placement an intraoperative virtual implant planning system (VIPS) as an application for mobile C-arms was established. The aim of the study was the validation of the implemented VIPS comparing the intraoperative planning with the actual placement of the screws. The study was conducted as a single-centre randomised controlled trial in a primary care institution. The hypothesis of the study was that there is conformity between the virtual implant position and the real implant placement. 30 patients with FDR type A3, C1 and C2 according to the AO-classification were randomised in two treatment groups and allocated either in the conventional or in the VIPS group in which the patients underwent an intraoperative planning before screw placement. The randomisation was performed on the basis of a computer-generated code. After fracture reduction an initial diaphyseal fixation of the plate was done. Then the matching of the three-dimensional virtual plate with the image of the real plate in the fluoroscopy shots in two planes was performed automatically. The implant placement was planned intraoperatively in terms of orientation, angulation and length of the screws. After the placement of four or five locking screws the implant position was verified with an intraoperative three-dimensional mobile C-arm scan. The locking screws near the joint line were examined and compared in relation to the actual and the planned inclination angle, the azimuth angle which is determined analogue to a compass rose and the screw-tip distance. The planned and actual parameters of the locking screws were then statistically analysed applying the Shapiro-Wilk - and the Students t-test.Background
Patients/Material and Methods
Digital planning of implants in regard to position and size is done preoperatively in most cases. Intraoperative it can only be made by navigation systems. With the development of the VIPS-method (Virtual Implant Planning System) as an application for mobile C-arms, it is possible to do an intraoperative virtual planning of the screws near the joint in treatment of distal radius fractures by plating. Screw misplacement is a well known complication in the operative treatment of these fractures. The aim of this prospective randomised trial was to gain first clinical experiences and to compare VIPS with the conventional technique. The study hypothesis was that there will be less screw misplacement in the VIPS group. We included 40 patients with distal radius fractures type A3, C1 and C2 according to the AO-classification. In a pilot study the first 10 Patients were treated by the VIPS method to gain experience with VIPS in a clinical set-up. The results of the pilot-study are not part of this analysis. Then 15 Patients were web-based randomised into two groups. After diaphysial fixation of a 2.4 mm Variable Angle Two-Column Volar Distal Radius Plate and fracture reduction matching of a three-dimensional virtual plate to the two-dimensional image of the plate in the fluoroscopy shots in two plains was performed automatically in the VIPS group. The variable angle locking screws were planed in means of direction and length. Drilling was done by the use of the Universal Variable Angle Locking Drill Guide that was modified by laser marks at the rim of the cone to transfer the virtual planning. The drill guide enables drilling in a cone of 30°. In the control group the same implant was used in a conventional technique that means screw placement by the surgeon without digital planning. After implant placement an intraoperative three-dimensional scan was performed to check the position and length of the screws near the joint. OR- and fluoroscopy-time was documented. In addition the changes of misplaced screws were engaged.Background
Methods
The goal of this study was to validate accuracy and reproducibility of a new 2D/3D reconstruction-based program called “HipRecon” for determining cup orientation after THA. “HipRecon” uses a statistical shape model based 2D/3D deformable registration technique that can reconstruct a patient-specific 3D model from a single standard AP pelvic X-ray radiograph. Required inputs include a digital radiograph, the pixel size, and the film-to-source distance. No specific calibration of the X-ray, or a CAD (computer-assisted design) model of the implant, or a CT-scan of the patient is required. Cup orientation is then calculated with respect to the anterior pelvic plane that is derived from the reconstructed 3D-model. The validation study was conducted on datasets of 29 patients (31 hips). Among them, there were 15 males and 14 females. Each dataset has one post-operative X-ray radiograph and one post-operative CT-scan. The post-operative CT scan for each patient was used to establish the ground truth for the cup orientation. Radiographs with deep centering (7 radiographs), or of pelvises with fractures (2 radiographs), or with both (1 radiograph), or of non-hemispherely shaped cup (1 radiograph) were assessed separately from the radiographs without above mentioned phenomena (18 radiographs) to estimate a potential influence on the 2D/3D reconstruction accuracy. To make the description easier, we denote those radiographs with above mentioned phenomena as non-normal cases and those without as normal cases. The cup anteversions and inclinations that were calculated by “HipRecon” were compared to the associated ground truth. To validate the reproducibility and the reliability, one observer conducted twice measurements for each dataset using “HipRecon”. The mean accuracy for the normal cases was 0.4° ± 1.8° (−2.6° to 3.3°) for inclination and 0.6° ± 1.5° (−2.0° to 3.9°) for anteversion, and the mean accuracy for the non-normal cases was 2.3° ± 2.4° (−2.1° to 6.3°) for inclination and 0.1° ± 2.8° (−4.6° to 5.1°) for anteversion. Comparing the measurement from the normal radiographs to those from the non-normal radiographs using the Mann-Whitney U-test, we found a significant difference in measuring cup inclination (p = 0.01) but not in measuring cup anteversion (p = 0.3). Bland-Altman analysis of those measurements from the normal cases indicated that no systematical error was detected for “HipRecon,” as the mean of the measurement pairs were spread evenly and randomly for both inclination and anteversion. “HipRecon” showed a very good reproducibility for both parameters with an intraclass correlation coefficient (ICC) for inclination of 0.98 (95% Confidence Limits (CL): 0.96–0.99) and for anteversion of 0.96 (95% CL: 0.91–0.98). Accurate assessment of the acetabular cup orientation is important for evaluation of outcome after THA, but the inability to measure acetabular cup orientation accurately limits one's ability to determine optimal cup orientations, to assess new treatment methods of improving acetabular cup orientation in surgery, and to correlate the acetabular cup orientation to osteolysis, wear, and instability. In this study, we showed that “HipRecon” was an accurate, consistent, and reproducible technique to measure cup orientation from post-operative X-ray radiographs. Furthermore, our experimental results indicated that the best results were achieved with the radiographs of non-fractured pelvises that included the anterior superior iliac spines and the cranial part of the non-fractured pelvis. Thus, it is recommended that these landmarks should be included in the radiograph whenever the 2D/3D reconstruction-based method will be used
