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MRI oblique view accurately evaluates trochlear morphology in patients with patellofemoral instability
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According to study results, the MRI oblique trochlear view accurately evaluates trochlear morphology and better characterizes trochlear dysplasia in patients with patellofemoral instability compared with the standard MRI axial sequences.
“Standard axial MRI cuts are perpendicular to the femoral shaft and provide meaningful images of the proximal trochlea,” Jack Farr, MD, told Healio.com/Orthopedics. “However, for the mid and distal aspects, as the trochlea curves posteriorly, the cut becomes oblique and less clear. Using an oblique imaging cut improves the clarity of the mid and distal trochlea not only for morphology assessment, but also articular cartilage detail.”
Researchers retrospectively reviewed 73 patients with patellofemoral instability using the MRI oblique trochlear view and 73 control patients using standard MRI axial sequences. Investigators assessed the trochlear morphology on axial and oblique trochlear sequences at the following three levels: level 1 at 25%; level 2 at 50%; and level 3 at 75% of the length of the trochlear groove. They also measured the trochlear sulcus angle and sulcus depth at three levels. They compared measurements between the new trochlear sequences and the standard axial sequences.
Results showed that at all three levels, the trochlear sulcus angle and sulcus depth were statistically different between the axial and oblique trochlear views. The trochlear sulcus angle in the axial view for level one, level two and level three was 160°, 146.8° and 134.7°, respectively. In the oblique trochlear view, the sulcus angle was 154.7°, 151.08° and 148°, respectively. The sulcus depth in the axial view was 2.29, 3.97 and 6.25, respectively. In the oblique trochlear view, the sulcus depth was 3.2, 4.18 and 5.14, respectively. Investigators noted the oblique trochlear view showed more uniform sulcus angle and sulcus depth along the trochlea.
Farr said, “The clinical importance of trochlear dysplasia on patellar instability is well recognized, but historical classifications are now being reassessed to improve communication of the patient specific pathoanatomy. Understanding the shape of the mid and distal aspects (shallow, flat or convex) may allow a more precise classification that may impact clinical management. Future research on transferring 2D images into a 3D understanding will continue to evolve.”– by Monica Jaramillo
Disclosures: The researchers report no relevant financial disclosures.
Perspective
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James Bicos, MD
In the article, “Femoral trochlear geometry in patients with trochlear dysplasia using MRI oblique trochlear view,” the authors study whether there is a better way to evaluate trochlear dysplasia on an MRI besides using the standard axial views. Since the trochlea of the knee is not in one plane (studies have shown that trochlear groove orientation is up to 45° off the axial plane), MRI evaluation of the entirety of the trochlear surface can be difficult. Furthermore, the Dejour classification, which is the most predominant system used to describe trochlear dysplasia, has low intra- and interobserver correlations. Studies have questioned whether this limitation of the Dejour classification could be the basis for the variability in the literature regarding the outcomes of patellar instability procedures.
The authors of this study do an excellent job in showing that the oblique trochlear view sequence on an MRI can more accurately evaluate the trochlear morphology to better characterize trochlear dysplasia. This information could be useful to help determine patients that might benefit from trochleoplasty and how much to deepen the trochlear groove.
Oakland University William Beaumont School of Medicine
William Beaumont Sports Medicine Fellowship
Bingham Farms, Michigan
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