Pediatric Elbow Fracture Diagnosis Using 3-D MR Imaging

Marrit Thorkelson, R.T.(R)(MR); Robyn Augustyn, B.S.R.T., R.T. (R)(CT); Craig E. Barnes, M.D.

After the cast was removed, swelling and limited range of motion still were present in the elbow. Another radiograph showed an ossified structure overlying the medial joint and a periosteal reaction along the distal dorsal cortex of the right humerus. The findings raised the possibility of a medial epicondylar avulsion fracture, and an MR examination was ordered to evaluate the area.

MR images revealed an avulsion fracture of the right medial condyle and epicondyle. The fragment was displaced medially and rotated; the articular surface was oriented laterally facing the distal humerus, which correlated with the calcification seen on previous radiographs. The displaced, predominately cartilaginous, trochlear and medial epicondyle fracture fragment was visible on cartilage-specific fat-suppressed T1 volume sequences (see Figure 3). MR images were sent to the 3-D Innovation Laboratory and processed into 3-D volume-rendered images for surgical planning using a sequence that isolates bone and cartilage from adjacent structures. Orthopedic surgeons evaluated the images, and determined that an open reduction and internal fixation surgical procedure was required. They performed the procedure on the trochlea and medial epicondyle, using Kirschner wires to repair the fracture. A postoperative radiograph, obtained while the elbow was in a cast, showed Kirschner wire placement and confirmed fracture repair (see Figure 4).

Imaging Techniques

Multiplanar multisequence MR imaging of the right elbow, without gadolinium contrast, was performed with the patient under general anesthesia after several radiographic examinations led to incorrect diagnoses. A 3-D fat-suppressed T1 gradient echo sequence was used to capture volumetric image data and highlight cartilage and bony anatomy. The data were sent to the 3-D Innovation Lab for postprocessing, and technologists used Smart Segmentation (CT Viewer, Intellispace Portal, Philips) techniques, which involved highlighting individual anatomical parts of the elbow and combining them into a 3-D volumetric image. The segmentation tool provides a method to manually segment each part of the anatomy and assign colors to each tissue so that bone and cartilage are easily identified. The 3-D view of the fracture and cartilage revealed their relationship to the displaced osteocartilaginous fracture fragment, which was useful for the radiologist reviewing the MR images as well as for the orthopedic surgeon (see Figure 5). 3-D volume sequences have been used for some time to create coronal, axial, or sagittal reformats from source data. However, the use of 3-D volume sequences to make 3-D volumetric images in musculoskeletal imaging is a new application.

Conclusion

Fractures of the elbow are prevalent in the pediatric population. Although 20% of pediatric elbow fractures involve the medial epicondyle, these types of injuries typically occur in patients older than the child featured in this case summary when the medial epicondyle is at least partially ossified.³ Pediatric fractures of the epicondyle and condyle can be difficult to assess on radiographs. In this case, because of the patient’s age, the lack of ossification of the trochlea and medial epicondyle made the fracture challenging to visualize, necessitating the use of a more sensitive imaging tool. MR imaging was a superior choice because of its ability to image the bones and soft structures of the elbow, including the cartilage. The ability to create volumetric thin-slice sequences using MR imaging opens the door to other innovative uses, and 3-D postprocessing of captured data can assist in MR interpretation and surgical planning.

References

1. Hyatt BT, Schmitz MR, Rush JK. Complication of pediatric elbow fractures. Orthop Clin North Am. 2016;47(2):377-385. doi:10.1016/j.ocl.2015.09.011.
2. Tanabe K, Miyamoto N. Fracture of an unossified humeral medial epicondyle: use of magnetic resonance imaging for diagnosis. Skeletal Radiol. 2016;45(10):1409-1412. doi:10.1007/s00256-016-2434-3.
3. Gottschalk HP, Eisner E, Hosalkar HS. Medial epicondyle fractures in the pediatric population. J Am Acad Orthop Surg. 2012;20(4):223-232. doi:10.5435/JAAOS-20-04-223.