Can we safely deform a plate to fit every bone? Population-based fit assessment and finite element deformation of a distal tibial plate

Convenient design method for customized implants based on bionic vein structure features

Matching implants to bones is crucial for customized orthopedic medicine. Existing methods for designing customized implants predominantly adopt the parameterized deformation method that uses a fragmented representation of semantic parameters. Such a representation cannot provide information integration management and therefore restricts the retrieval of information regarding implant features and the improvement of customized design efficiency. Therefore, this study proposes a rapid design method for customized implants based on bionic vein structure features. First, a bionic vein structure was designed to represent the implant type. Second, the bionic vein structure was represented by a digraph structure with morphological and dimensional features. Finally, the implant model was rapidly built by retrieving the sketch and other modeling operations. Common implants such as the T-shaped plate, L-shaped plate, clover plate, and femoral stem prosthesis were used as explanations or test cases. The experimental work shows that combining the traditional parametric deformation method with bionic vein structure features in our present method is flexible and efficient results, and can improve the efficiency of customized implant design.

Bone morphological feature extraction for customized bone plate design

Fractures are difficult to treat because of individual differences in bone morphology and fracture types. Compared to serialized bone plates, the use of customized plates significantly improves the fracture healing process. However, designing custom plates often requires the extraction of skeletal morphology, which is a complex and time-consuming procedure. This study proposes a method for extracting bone morphological features to facilitate customized plate designs. The customized plate design involves three major steps: extracting the morphological features of the bone, representing the undersurface features of the plate, and constructing the customized plate. Among these steps, constructing the undersurface feature involves integrating a group of bone features with different anatomical morphologies into a semantic feature parameter set of the plate feature. The undersurface feature encapsulates the plate and bone features into a highly cohesive generic feature and then establishes an internal correlation between the plate and bone features. Using the femoral plate as an example, we further examined the validity and feasibility of the proposed method. The experimental results demonstrate that the proposed method improves the convenience of redesign through the intuitive editing of semantic parameters. In addition, the proposed method significantly improves the design efficiency and reduces the required design time.

Analysis of the Curvature and Morphologic Features of the Lumbar Vertebral Endplates Through the Transverse Section: A Radioanatomical Study

BACKGROUND

Knowledge concerning the curvature of the vertebrae through the transverse section is of clinical significance. However, relevant reports are scarce. This study investigated the features based on the cross-sections of lumbar vertebral endplates to provide information for clinical practice.

METHODS

Computed tomography images of 78 subjects were retrospectively reviewed. The geometric morphometrics was performed, and the curvature of the vertebral endplates was calculated by the self-written MATLAB algorithm. The principal component analysis, the canonical variate analysis, the discriminant function analysis, and the Mann-Whitney U test were performed. Statistical significance was set at P < 0.05.

RESULTS

No gender difference was found. In contrast, a morphologic difference was found between the superior and inferior lumbar vertebral endplates and between different segments. More specifically, the shape of the endplates gradually changes from the renal shape at superior L1 to the shell-like shape at inferior L5. The mean curvature values of the lateral anterior border were all around 0.60 cm^-1, whereas the mean curvature values of the lateral posterior borders range from 0.66 to 1.09 cm^-1 from L1 to L5. From L1 to L3, the mean and maximum curvature of the lateral posterior superior vertebral endplates decrease. The trend could also be found on the lateral posterior border of the inferior endplates from L1 to L3.

CONCLUSIONS

The current study described morphologic variations and curvature of the lumbar vertebral endplates, which have not been reported previously. The different curvature distribution could provide important information for surgeons and manufacturers.

Automatic estimation of morphological characteristics of proximal tibia for precise plate treatment using model matching

Plate treatment is currently the standard treatment of proximal tibia fracture. Morphological characteristics can help orthopedic surgeons understand anatomic information of tibia and choose well-matched plate for reducing difficulties in plate treatment. However, manual measurement of morphological characteristics of patient's tibia is time-consuming and labor-intensive. Therefore, this study proposes an automatic method to accurately estimate the morphological characteristics of patient's tibia for assisting plate treatment. In the off-line stage, an average shape with typical characteristics was computed from 422 tibia models, and the morphological characteristics of the average shape were measured by the orthopedic surgeon. In the on-line stage, the point's correspondence between the average shape and every tibia model was created by the proposed morphable model matching method firstly. Then, the morphological characteristics of tibia for every patient were estimated automatically based on the point's correspondence and characteristics of average shape. The effectiveness of the method was validated by comparing the manual measured and automatic-estimated characteristics. In addition, the basic experiments of virtual and real plate implantation preliminarily confirmed that the automatic-estimated morphological characteristics were helpful for plate treatment. In all, we propose an automatic and accurate estimation method of morphological characteristics for a large-scale library of Chinese tibia models, which provides orthopedic surgeons with scientific and quantitative description of tibia.

Anatomical fitting of a plate shape directly derived from a 3D statistical bone model of the tibia

INTRODUCTION

Intra- and inter-population variations of bone morphology have made the process of designing an anatomically well-fitting fracture fixation plate challenging. Although statistical bone models have recently been used for analysing morphological variabilities, it is not known to what extent they would also provide the basis for the design of a new plate shape. This would be particularly valuable in the case where no existing plate shape is available to start the process of fit optimisation. Therefore, this study investigated the anatomical fitting of a plate shape (statistical plate) derived from the mean shape of a statistical 3D tibia bone model in comparison to results available from two other plate shapes.

METHODS

Forty-five 3D bone models of tibiae from Japanese cadaver specimens, as well as 3D models of the plate undersurface of both a commercial and shape optimised Medial Distal Tibia Plate, were utilised from earlier studies. The mean shape of the 3D statistical bone model was generated from the tibia models utilising the Statismo framework. With reverse engineering software, the plate undersurface of the statistical plate shape was derived directly from the mean surface of the statistical 3D bone model. Through an iterative process, the statistical plate model was placed at the correct surgical position on each bone model for fit assessment.

RESULTS

The statistical plate was fitting for 20% of the tibiae compared to 13% for the commercial and 67% for the optimised plate, respectively.

CONCLUSIONS

The plate shape derived directly from a statistical bone model was fitting better than the commercial plate, but considerably inferior to that of an optimised plate. However, the results do clearly indicate that this approach provides an appropriate and solid basis for commencing shape optimisation of the statistical plate. Studies of other anatomical regions are required to confirm whether these findings can be generalised.

Preliminary exploration of a quantitative assessment index for the matching performance of anatomical bone plates using computer

BACKGROUND

To explore a new quantitative index to assess the matching performance of anatomical bone plates using digital technology.

METHODS

CT data of normal tibias of 40 adults were collected. Two brands of medial distal tibia plates were digitized. Two trained orthopedists simulated the surgical operation in Rhino 5.1 software by placing the plate curve on the medial distal tibia surface. The volume of the interstice between the plate curve and the bone surface was measured. The inverse value of this average interstice distance was used as the matching performance index (MPI). A wall thickness analysis tool was used to mark various interstice distances with varied colors.

RESULTS

The Kangli medial distal tibia plate had a MPI of 0.55 ± 0.08 by operator A and 0.55 ± 0.06 by operator B. The general care medial distal tibia plate had a MPI of 0.32 ± 0.06 by operator A and 0.31 ± 0.05 by operator B. There were significant variations in the MPI between the two types of plates by both operators (p < 0.001). And significant variations were observed in the MPI of general care medial distal tibia plates among various operator groups (p = 0.028).

CONCLUSION

This quantitative index of matching performance is straightforward and intuitive. However, we still need a method to improve the experimental repeatability, especially when it comes to a plate with poor matching performance.

New Design Process for Anatomically Enhanced Osteosynthesis Plates

This study evaluated the implementation and effectiveness of an iterative process aimed to quantify and enhance the anatomical fit of an osteosynthesis plate design for the fifth metacarpal bone regarding a defined shape-based acceptance criterion (SAC) while complying with basic clinical requirements and engineering limitations. The process was based on employing virtual tools (a database of individual three-dimensional bone models, statistical analysis of the bone geometry, and proprietary software tools) to evaluate conformity between plate designs and bone shape. The conformity was quantified by the mean distance between plate and bone (MBP). The enhancement was completed when the median MBP of the population was below the SAC threshold. This was fulfilled by the third plate design (two enhancement iterations). The intentionally abstract enhancement process may serve as a guideline for development of plate designs for other indications. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1508-1517, 2019.

Fixation of Displaced Acetabular Fractures With an Anatomic Quadrilateral Surface Plate Through the Stoppa Approach

Satisfactory fixation for displaced acetabular fractures involving the quadrilateral surface remains difficult to obtain with conventional reconstruction plates. To achieve minimally invasive management of fractures of the quadrilateral surface, the authors designed a type of anatomic quadrilateral surface plate (AQSP). A retrospective study to assess the therapeutic results of the AQSP was performed at their institution. A total of 26 patients with quadrilateral surface fractures fixed with an AQSP through the Stoppa approach from February 2014 to February 2015 were included in this study. There were 16 men and 10 women with a mean age of 37.5 years. The patients were followed for a mean of 28.81 months (range, 24-36 months). The mean operative time was 98.85±16.08 minutes, and the mean intraoperative blood loss was 353.85±124.84 mL. Postoperative radiographs and computed tomography scans showed that anatomic and good reductions were obtained in 88.46% (23 patients) and 11.54% (3 patients) of the patients, respectively. Screw loosening was not observed. All of the fractures healed well at a mean of 3.54 months. Two cases of obturator nerve injury and 1 case of corona mortis rupture were observed. However, permanent complications were not observed. The mean Merle d'Aubigné score at final follow-up was 16.38±1.33 points. The authors conclude that satisfactory fixation with the AQSP system can be achieved through the Stoppa approach. [Orthopedics. 2019; 42(2):e180-e186.].

Utility of cement injection to stabilize split-depression tibial plateau fracture by minimally invasive methods: A finite element analysis

BACKGROUND

Treatment for fractures of the tibial plateau is in most cases carried out by stable fixation in order to allow early mobilization. Minimally invasive technologies such as tibioplasty or stabilization by locking plate, bone augmentation and cement filling (CF) have recently been used to treat this type of fracture. The aim of this paper was to determine the mechanical behavior of the tibial plateau by numerically modeling and by quantifying the mechanical effects on the tibia mechanical properties from injury healing.

METHODS

A personalized Finite Element (FE) model of the tibial plateau from a clinical case has been developed to analyze stress distribution in the tibial plateau stabilized by balloon osteoplasty and to determine the influence of the cement injected. Stress analysis was performed for different stages after surgery.

FINDINGS

Just after surgery, the maximum von Mises stresses obtained for the fractured tibia treated with and without CF were 134.9 MPa and 289.9 MPa respectively on the plate. Stress distribution showed an increase of values in the trabecular bone in the treated model with locking plate and CF and stress reduction in the cortical bone in the model treated with locking plate only.

INTERPRETATION

The computed results of stresses or displacements of the fractured models show that the cement filling of the tibial depression fracture may increase implant stability, and decrease the loss of depression reduction, while the presence of the cement in the healed model renders the load distribution uniform.

A numeric approach for anatomic plate design

Osteosynthesis plate designs with high levels of anatomical compliance have been demonstrated to have numerous clinical benefits. The purpose of this paper is to introduce a systematic numeric approach for anatomic plate design on the example of the distal medial tibia. The advantage of using numeric approaches for plate design is to gain objective and complete anatomical input as opposed to cadaveric investigations with limited sample sizes. A recent development in this area is a proprietary technology called SOMA which is based on a large database of 3D bone models generated from thin-slice computer tomographic scans plus associated software tools. In this paper, one of these associated software tools is described which automatically assesses the anatomic fit of osteosynthesis plates based on a large database of bone models. As an example, this tool was applied to assess the mean plate to bone distance of distal medial tibia plates, when fitted onto 444 Caucasian and 310 Asian 3D bone models respectively. The analyses revealed differences in the anatomical compliance of plates from different generations and manufacturers. The anatomical compliance of SOMA designed plates was statistically significantly better compared to all other plates in all groups "Short", "Intermediate" and "Long" and for both ethnicities "Caucasian" and "Asian" (P<0.001). The study has shown that using an underlying database with accompanying computational tools such as SOMA can be a powerful and efficient approach towards the development and advancement of osteosynthesis plates in trauma surgery, ultimately resulting in plates with high levels of anatomical compliance and potential clinical benefits.

Clustering of Morphological Features for Identifying Femur Cavity Subtypes With Difficulties of Intramedullary Nail Implantation

Intramedullary (IM) nail implantation is currently the standard treatment for femoral intertrochanteric fractures. However, individual differences in femur cavity bring a challenge in designing well-matched IM nails and cause difficulties in IM nail implantation. Therefore, there is an intense need to analyze femur cavities to predict difficulties in IM nail implantation to assist the design of IM nails. This study proposed a method to automatically identify subtypes of femur cavities that exhibit differences in potential difficulties in nail implantation by clustering the morphological features of femur models. The unsupervised subtype extraction method offers a scientific approach to stratify patients for designing and choosing well-matched IM nails. First, the quantitative morphological features of 422 femur cavities were extracted from computed tomography patient models. Second, 422 femur cavities were clustered into three distinct subtypes using a density peak-based k-means clustering method to provide a possible solution for the scientific design of IM nails. The effectiveness of the identified subtypes was validated by comparing subtype differences associated with IM nail implantation and the natural attributes of the patient. Quantitative evaluation of the mismatch degree and real clinical cases confirmed that the clustering results were clinically effective, with clear differences in the subtypes. Therefore, particular IM nails designed from the identified subtypes will potentially facilitate IM nail implantation and reduce complications. Compared with state-of-the-art methods, we used the largest scale dataset and unsupervised clustering to achieve subtype identification of femur cavities with clinical significance.