BackgroundTo study the morphology of the human spine and new spinal fixation methods, scientists require cadaveric specimens, which are dependent on donation. However, in most countries, the number of people willing to donate their body is low. A 3D printed model could be an alternative method for morphology research, but the accuracy of the morphology of a 3D printed model has not been determined.MethodsForty-five computed tomography (CT) scans of cervical, thoracic and lumbar spines were obtained, and 44 parameters of the cervical spine, 120 parameters of the thoracic spine, and 50 parameters of the lumbar spine were measured. The CT scan data in DICOM format were imported into Mimics software v10.01 for 3D reconstruction, and the data were saved in .STL format and imported to Cura software. After a 3D digital model was formed, it was saved in Gcode format and exported to a 3D printer for printing. After the 3D printed models were obtained, the above-referenced parameters were measured again.ResultsPaired t-tests were used to determine the significance, set to P<0.05, of all parameter data from the radiographic images and 3D printed models. Furthermore, 88.6% of all parameters of the cervical spine, 90% of all parameters of the thoracic spine, and 94% of all parameters of the lumbar spine had Intraclass Correlation Coefficient (ICC) values >0.800. The other ICC values were <0.800 and >0.600; none were <0.600.ConclusionIn this study, we provide a protocol for printing accurate 3D spinal models for surgeons and researchers. The resulting 3D printed model is inexpensive and easily obtained for spinal fixation research.

BackgroundThe management of displaced intra-articular calcaneal fractures (DIACFs) remains challenging and controversial. A prospective randomized controlled trial was conducted to compare percutaneous reduction, cannulated screw fixation and calcium sulfate cement (PR+CSC) grafting with minimally invasive sinus tarsi approach and plate fixation (MISTA) for treatment of DIACFs.MethodsUltimately, 80 patients with a DIACFs were randomly allocated to receive either PR+CSC (N = 42) or MISTA (N = 38). Functional outcomes were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot scores. Radiological results were assessed using plain radiographs and computed tomography (CT) scans, and postoperative wound-related complications were also recorded.ResultsThe average time from initial injury to operation and the average operation time in the PR+CSC group were both significantly shorter than those in the MISTA group (p < 0.05). There were significantly fewer complications in the PR+CSC group than those in the MISTA group (7.1 % vs 28.9 %, p < 0.001). The calcaneal width immediate postoperatively and at the final follow-up in the MISTA group were obviously improved compared to those in the PR+CSC group (p < 0.001). The variables of sagittal motion and hindfoot motion of the AOFAS scoring system in the PR+CSC group were significantly higher than those in the MISTA group (p < 0.05). The good and excellent results in the two groups were comparable for Sanders Type-II calcaneal fractures, but the good to excellent rate in the MISTA group was significantly higher for Sanders Type-III fractures (p < 0.05).ConclusionThe clinical outcomes are comparable between the two minimally invasive techniques in the treatment of Sanders Type-II DIACFs. The PR+CSC grafting is superior to the MISTA in terms of the average time between initial injury and operation, operation time, wound-related complications and subtalar joint activity. However, the MISTA has its own advantages in improving the calcaneal width, providing a more clear visualization and accurate reduction of the articular surface, especially for Sanders Type-III DIACFs.Trial registrationChiCTRIOR16008512. 21 May 2016.

BackgroundHip fracture is a severe and common injury that occurs predominantly in the elderly. Blood loss in the perioperative period is associated with a greater risk of dying in anaemic patients. The aim of the study was to explore the best way to treat stable intertrochanteric fractures, taking hidden blood loss into account.MethodsThis prospective, randomised blinded study included patients aged over 65 years with stable intertrochanteric fractures (Evans grades I and II). The patients were allocated to one of two groups treated via extramedullary or intramedullary fixation. Patient data were retrieved from electronic charts. Functional recovery was evaluated using the Functional Recovery Score of Zuckerman. Postoperative complications were also recorded. The formula of Nadler and Gross was used to calculate blood loss.ResultsThere were 92 patients in the extramedullary and 106 in the intramedullary group. Age, sex, the cause of injury, the type of fracture, the observed blood loss, functional recovery, time to union, complications, and American Society of Anesthesiologists classification did not differ significantly between the two groups (all p-values > 0.05). The frequencies of lung infection, electrolyte imbalance, and hypoproteinemia differed between groups (all p-values < 0.05). Total and hidden blood loss were higher in the intramedullary group (p = 0.001).ConclusionExtramedullary (compared with intramedullary) fixation of stable intertrochanteric fractures significantly reduces perioperative blood loss but affords similar functional outcomes and times to union. In view of the morbidity and complications associated with acute anaemia and transfusions, extramedullary fixation may be the optimal choice for treatment of stable fractures, being associated with reduced blood loss.Trial registrationThe study was retrospectively registered at the Chinese Clinical Trial Registry, number: ChiCTR-INQ-16009754, trial registration date: 6th Nov. 2016.

Transpedicular transdiscal screw fixation is an alternative technique used in lumbar spine fixation; however, it requires an accurate screw trajectory. The aim of this study is to design a novel 3D-printed custom drill guide and investigate its accuracy to guide the trajectory of transpedicular transdiscal (TPTD) lumbar screw fixation. Dicom images of thirty lumbar functional segment units (FSU, two segments) of L1–L4 were acquired from the PACS system in our hospital (patients who underwent a CT scan for other abdomen diseases and had normal spine anatomy) and imported into reverse design software for three-dimensional reconstructions. Images were used to print the 3D lumbar models and were imported into CAD software to design an optimal TPTD screw trajectory and a matched custom drill guide. After both the 3D printed FSU models and 3D-printed custom drill guide were prepared, the TPTD screws will be guided with a 3D-printed custom drill guide and introduced into the 3D printed FSU models. No significant statistical difference in screw trajectory angles was observed between the digital model and the 3D-printed model (P > 0.05). Our present study found that, with the help of CAD software, it is feasible to design a TPTD screw custom drill guide that could guide the accurate TPTD screw trajectory on 3D-printed lumbar models.

Lines are important features for Airborne Laser Scanning (ALS) point clouds processing and model reconstruction, in which the lines are often detected by a Hough Transformation (HT) similar to in image processing. In fact, feature lines represent the edges of buildings, which are man-made objects and often have orthogonal, parallel and other relationships of regularity. In this paper, we propose a method for detecting and refining the line features from ALS data in consideration of these relationships of regularity. First, an angle and ρ voting algorithm is applied to conduct line detection to obtain the primary results. Second, an optimization process called structure sensitive competition, which relies on a line stability descriptor (LSD), refines the detected line segments. Finally, this proposed method is tested and compared to HT algorithm on a group of buildings with different complexity. The quality indicators, completeness, correctness and quality, show that the quality of the extracted lines can be substantially improved after the structure sensitive optimization.

Objective: At present, it is still uncertain whether single screw has the same stability as double screws in the treatment of ulnar coronal process basal fracture (Regan-Morry type III). So, we aimed to compare the pull-out force and anti-rotation torque of anterior single/double screw-cancellous bone fixation (aSSBF, aDSBF) in this fracture, and further study the influencing factors on anatomical and biomechanical stability of smart screw internal fixations.Methods: A total of 63 adult volunteers with no history of elbow injury underwent elbow CT scanning with associated three-dimensional reconstruction that enabled the measurements of bone density and fixed length of the proximal ulna and coronoid. The models of coronal process basal fracture, aSSBF and aDSBF, were developed and validated. Using the finite element model test, the sensitivity analysis of pull-out force and rotational torque was carried out. Results:The pull-out force of aSSBF model was positively correlated with the density of the cancellous bone and linearly related to the fixed depth of the screw. The load pattern of pull-out force of aDSBF model was similar to that of aSSBF model. The ultimate torque of aDSBF model was higher than that of aSSBF model, but the load pattern of ultimate torque of both models was similar to each other when the fracture reset was satisfactory, and the screw nut attaches closely to coronoid process. Moreover, with enhancement of initial pre-tightening force, the increase of ultimate torque of both models was small. Conclusions:In addition to three pull-out stability factors of smart screw fixations, fracture surface fitting degree and nut fitting degree are the other two important anatomical and biomechanical stability factors of smart screw fixations both for rotational stability. When all pull-out stability and rotational stability factors meet reasonable conditions simultaneously, single or double screw fixation methods are stable for the treatments of ulnar coronoid basal fractures.