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MR imaging of meniscal tears with discoid lateral meniscus
1Department of Radiology, Kinki University School of Medicine, Osakasayama, Osaka, Japan.
Objective:
To study MR findings of meniscal tears with discoid lateral menisci (DLMs) and to evaluate the incidence and accuracy of MRI compared to arthroscopical surgery.
Material And Methods:
MR appearances of surgically proved torn discoid lateral menisci (DLM) were studied in 57 knees (40 patients). They were all performed with a 1.5T MR before surgery. MR sequences included T1- and T2* weighted images on both coronal and sagittal planes and 3D-axial images with a slice thickness of 0.7 mm.
Result:
Of 57 DLMs, there were 32 complete DLMs and 25 incomplete DLMs. Twenty-five of 32 complete DLMs had tears; including seven with intrasubstance tear, five with radial tear, five with other kinds of tears and eight with severe tears involving whole meniscus. On the other hand, 13 of 25 incomplete DLMs had tears; including two with intrasubstance tear, six with radial tear, four with other kinds of tears and one with severe tears. All DLMs were correctly diagnosed on MR images. Twenty-seven of 38 tears with DLM were correctly identified on conventional 2D MR images. This yielded 71.1% sensitivity, 100% specificity and 80.7% overall accuracy. When adding axial 3D MR images to 2D MR images, 36 of 38 tears were correctly diagnosed. A combination of both techniques yielded a sensitivity of 94.7% and a specificity of 100%. Ten of 11 radial tears with DLM were correctly identified on 3D axial images, where only three of them could be diagnosed on conventional 2D images. Eight of nine intrasubstance tears were correctly identified on 3D axial images, where six of them could be diagnosed on conventional 2D images.
Conclusion:
DLMs had a much higher incidence of meniscal tears than normally shaped lateral menisci and MR is the only modality of choice to evaluate them before surgery. Especially 3D axial MR images were quite useful in the detection of intrasubstance and radial tears often associated with DLMs.
Insights
Discoid lateral menisci (DLMs) have a high incidence of tears. Magnetic resonance imaging (MRI) accurately detects these tears, with 3D axial sequences significantly improving the identification of complex tears.
Area of Science:
- Orthopedic imaging
- Radiology
- Knee anatomy
Background:
- Discoid lateral menisci (DLMs) are an anatomical variation with a higher predisposition to meniscal tears compared to normal menisci.
- Accurate preoperative diagnosis of DLMs and associated tears is crucial for effective surgical planning and patient outcomes.
Purpose of the Study:
- To characterize the magnetic resonance (MR) imaging findings of meniscal tears in DLMs.
- To evaluate the diagnostic accuracy of MRI in detecting meniscal tears associated with DLMs, comparing it with arthroscopic surgery findings.
Main Methods:
- Retrospective analysis of MR images from 57 knees with surgically confirmed DLMs (40 patients) using a 1.5T MR scanner.
- MR sequences included T1- and T2*-weighted coronal and sagittal images, and high-resolution (0.7 mm slice thickness) 3D axial images.
- Comparison of MR findings with arthroscopic surgical results.
Main Results:
- Of 57 DLMs, 32 were complete and 25 were incomplete. Tears were present in 25/32 complete DLMs and 13/25 incomplete DLMs.
- Overall MR diagnosis of DLMs was 100% accurate.
- Conventional 2D MRI detected 71.1% of tears, while the addition of 3D axial images improved tear detection to 94.7% sensitivity.
- 3D axial imaging was particularly effective for detecting intrasubstance and radial tears, often missed on 2D sequences.
Conclusions:
- DLMs exhibit a significantly higher incidence of meniscal tears than normally shaped lateral menisci.
- MRI is the preferred imaging modality for evaluating DLMs and associated tears prior to surgery.
- 3D axial MR sequences substantially enhance the detection of complex tear patterns, including intrasubstance and radial tears, in DLMs.