Identification of recurring scapular fracture patterns using 3-dimensional computerized fracture mapping

Three-Dimensional Mapping of Scapular Body, Neck, and Glenoid Fractures

OBJECTIVES

The purpose of this study was to report patterns of scapular fractures and define them with a contemporary methodology.

METHODS

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DESIGN

Retrospective study, 2015-2021.

SETTING

Single, academic, Level 1 trauma center.

PATIENT SELECTION CRITERIA

Consecutive patients ≥18 years, presenting with unilateral scapula fracture, with thin-slice (≤0.5-mm) bilateral computed tomography (CT) scans of the entirety of both the injured and uninjured scapulae.

OUTCOME MEASURES AND COMPARISONS

Thin-slice (0.5-mm) CT scans of injured and normal scapulae were obtained to create three-dimensional (3D) virtual models. 3D modeling software (Stryker Orthopedics Modeling and Analytics, Stryker Trauma GmbH, Kiel, Germany aka SOMA) was used to create a 3D map of fracture location and frequency. Fracture zones were delineated using anatomic landmarks to characterize fracture patterns.

RESULTS

Eighty-seven patients were identified with 75 (86%) extra-articular and 12 (14%) intra-articular fractures. The dominant fracture pattern emanated from the superior lateral border (zone E) to an area inferior to the spinomedial angle (zone B) and was present in 80% of extra-articular fractures. A second-most common fracture line propagated from the primary (most-common) line toward the inferior medial scapular border with a frequency of 36%. Bare zones (with 1 or no fractures present) were identified in 4 unique areas. Furthermore, intra-articular fractures were found to be heterogenous.

CONCLUSIONS

The 3D fracture map created in this study confirmed that extra-articular scapular fractures occur in certain patterns with a relatively high frequency. Results provide greater insight into scapular fracture locations and may help to study prognosis of injury and improve treatment strategy including operative approaches and surgical tactics.

Mapping of Orthopaedic Fractures for Optimal Surgical Guidance

Orthopaedic fractures may be difficult to treat surgically if accurate information on the fracture propagation and its exit points are not known. Even with two-dimensional (2D) radiographic images, it is difficult to be completely certain of the exact location of the fracture site, the fracture propagation pattern and the exit points of the fracture. Three-dimensional (3D) computerised tomographic models are better in providing surgeons with the extent of bone fractures, but they may still not be sufficient to allow surgeons to plan open reduction and internal fixation (ORIF) surgery.Fracture patterns and fracture maps are developed to be visual tools in 2D and 3D. These tools can be developed using fractured bones either before or after fracture reduction. Aside from being beneficial to surgeons during pre-surgical planning, these maps aid bioengineers who design fracture fixation plates and implants for these fractures, as well as represent fracture classifications.Fracture maps can be either created ex silico or in silico. Ex silico models are created using 3D printed bone models, onto which fracture patterns are marked. In silico fracture models are created by tracing the fracture lines from a fractured bone to a healthy bone template on a computer. The points of interest in both of these representations are the path of fracture propagation on the bone's surface and exit zones, which eventually determine the surgeon's choice of plate and fracture reduction. Both ex silico and in silico fracture maps are used for pre-surgical planning by the surgeons where they can plan the best way to reduce the fracture as well as template various implants in a low-risk environment before performing the surgery.Recently, fracture maps have been further digitised into heat maps. These heat maps provide visual representations of critical regions of fractures propagating through the bone and identify the weaker zones in the bone structure. These heat maps can allow engineers to develop optimal surgical plates to fix an array of fracture patterns propagating through the bone. Correlation of fractured regions with the mechanisms of injury, age, gender, etc. may improve fracture predictability in the future and optimise the intervention, along with making sure that surgeons do not miss fractures of the bone that may otherwise be hidden from plain sight.

Three-dimensional mapping of sternum fractures from high-energy trauma

BACKGROUND

Sternum fractures are relatively uncommon injuries, which generally occur as a result of a high-energy mechanism and are often associated with significant concomitant injuries. These injuries may result in decreased quality of life if not properly addressed and yet are rarely operated on. The purpose of this project is to evaluate high-energy sternum fracture patterns using a previously published three-dimensional (3D) computed tomography (CT) reconstruction process to produce fracture frequency maps.

METHODS

Patients 18 years and older presenting to a Level I trauma center with sternum fractures due to high-energy trauma between October 2013 and January 2022 were included. A 3D reconstruction and reduction was performed for each sternum using medical image processing software (Materialize NV, Leuven, Belgium). The reconstructions were subsequently overlaid onto a template sternum and normalized using bony landmarks. Fracture lines for each injured sternum were transferred onto the template, creating 3D frequency maps.

RESULTS

A total of 120 patients met inclusion criteria. The study population had a uniform age distribution and 57.5% were male. The most common mechanism of injury was motor vehicle collision (64.2%). The breakdown of sternum fractures were isolated sternal body (55.8%), isolated manubrium (31.7%), and combined sternal body and manubrium fractures (12.5%). No xiphoid fractures were observed. Sternal body fractures were a near even mix of transverse (31.7%), oblique (32.9%), and comminuted (35.4%), while 75.5% of manubrium fractures were oblique. The most common associated injuries included rib fractures (80.8%) and traumatic brain injury (61.7%).

CONCLUSION

This study presents the fractures from sternum injuries in 3D, and provides insight into reproducible sternum injury patterns that have not previously been analyzed in this format. This fracture mapping technique presents numerous injury patterns simultaneously, such that more frequent morphologies can be appreciated for different patient groups.

LEVEL OF EVIDENCE

Diagnostic Tests or Criteria; Level V.

The automized fracture edge detection and generation of three-dimensional fracture probability heat maps

With proven impact of statistical fracture analysis on fracture classifications, it is desirable to minimize the manual work and to maximize repeatability of this approach. We address this with an algorithm that reduces the manual effort to segmentation, fragment identification and reduction. The fracture edge detection and heat map generation are performed automatically. With the same input, the algorithm always delivers the same output. The tool transforms one intact template consecutively onto each fractured specimen by linear least square optimization, detects the fragment edges in the template and then superimposes them to generate a fracture probability heat map. We hypothesized that the algorithm runs faster than the manual evaluation and with low (< 5 mm) deviation. We tested the hypothesis in 10 fractured proximal humeri and found that it performs with good accuracy (2.5 mm ± 2.4 mm averaged Euclidean distance) and speed (23 times faster). When applied to a distal humerus, a tibia plateau, and a scaphoid fracture, the run times were low (1-2 min), and the detected edges correct by visual judgement. In the geometrically complex acetabulum, at a run time of 78 min some outliers were considered acceptable. An automatically generated fracture probability heat map based on 50 proximal humerus fractures matches the areas of high risk of fracture reported in medical literature. Such automation of the fracture analysis method is advantageous and could be extended to reduce the manual effort even further.