Prediction of the Size of the Fragment in Comminuted Coronoid Fracture Using the Contralateral Side: An Analysis of Similarity of Bilateral Ulnar Coronoid Morphology

OBJECTIVE: To evaluate the morphological similarity of bilateral coronoid process. METHODS: A total of 128 sets of computed tomography images of bilateral coronoid process from patients between January 2015 and December 2016 were acquired for three‐dimensional reconstruction to generate a coronoid process model. The patients were aged between 31.4 ± 9.3 years. The upper 40% of the coronoid process was trimmed as targeted fragment for morphological analysis. The height, length, width as well as the radius of the medial and lateral facet of the targeted fragment were compared in terms of laterality, age, and gender. To evaluate the similarity of the articular surface of the coronoid process, a local coordinate was created and coordinate transformation algorithm was developed to realign the bilateral coronoid process for the following matching. Then Delaunay triangulation was introduced for calculation of the area of the articular surface. After matching of articular surface of the upper 40% of bilateral coronoid process, the overlapping area of the articular surface was quantified to assess the similarity in morphology and compared in regard to age and gender. RESULTS: In this study, the height of the target fragment was 12.40 ± 2.74 mm, which was 12.62 ± 2.06 mm for male patients and 12.13 ± 3.76 mm for female patients (t = 0.94, P = 0.35). The height of the target fragment was 12.79 ± 1.76 mm for patients >40 years and 13.23 ± 3.16 mm for patients <40 years (t = 1.11, P = 0.27). The height of the target fragment of left and right coronoid process was 12.26 ± 3.40 mm and 12.74 ± 2.79 mm (t = 1.15, P = 0.25). The length of the target fragment was 23.81 ± 2.67 mm, which was 23.86 ± 2.11 mm for male patients and 23.76 ± 2.85 mm for female patients (t = 0.23, P = 0.82). The length of the target fragment was 22.92 ± 1.96 mm for patients >40 years and 23.23 ± 2.14 mm for patients <40 years (t = 0.76, P = 0.45). The length of the target fragment of left and right coronoid process was 22.52 ± 2.89 mm and 21.66 ± 3.01 mm, respectively (t = 1.00, P = 0.32). The width of the target fragment was 23.12 ± 1.92 mm on average, which was 23.06 ± 1.54 mm for male patients and 23.19 ± 2.82 mm for female patients (t = 0.33, P = 0.74). The width of the target fragment was 24.82 ± 2.23 mm for patients >40 years and 23.46 ± 3.38 mm for patients <40 years (t = 1.56, P = 0.12). The width of target fragment of left and right coronoid process was 24.42 ± 2.22 mm and 24.47 ± 2.69 mm, respectively (t = 1.31, P = 0.19). The radius of medial facet was 6.44 ± 1.01 mm, which was 6.41 ± 1.39 mm for male patients and 6.47 ± 0.95 mm for female patients (t = 0.28, P = 0.78). The radius of medial facet was 6.82 ± 1.28 mm for patients >40 years and 6.46 ± 0.94 mm for patients <40 years (t = 1.31, P = 0.19). The radius of medial facet of left and right coronoid process was 6.43 ± 1.24 mm and 6.64 ± 1.34 mm (t = 1.60, P = 0.11). The radius of lateral facet was 11.84 ± 3.71 mm, which was 11.61 ± 4.24 mm for male patients and 12.11 ± 3.09 mm for female patients (t = 0.74, P = 0.46). The radius of medial facet was 11.82 ± 3.28 mm for patients >40 years and 12.46 ± 3.94 mm for patients <40 years (t = 1.02, P = 0.31). The radius of lateral facet of left and right coronoid process was 11.97 ± 5.31 mm and 10.29 ± 3.29 mm, respectively (t = 1.70, P = 0.09). The covering percentage of the articular surface of the upper 40% of bilateral coronoid process was 87% ± 12% with the covering percentage as 85.3% ± 14.2% for male patients and 90.0% ± 11.2% for female patients (t = 0.75, P = 0.41). The covering percentage was 88.2% ± 11.7% for patients >40 years and it was 87.4% ± 13.2% for patients <40 years (t = 0.98, P = 0.33). CONCLUSIONS: The present study suggested that bilateral coronoid process shares high similarity in terms of 3D structure and articular surface morphology, which suggested that the osseous architecture of the coronoid process with comminuted fracture could be predicted by the morphological information of the contralateral side.