Background
Magnetic resonance imaging (MRI) is often indicated in the diagnosis of pediatric knee trauma, but using traditional MRIs in children can be time-consuming, require anaesthesia, and sometimes cause discomfort. Recently, 3D turbo spin echo (TSE) MRIs with isotropic datasets have been found to reduce acquisition times substantially, but they have been little-studied in pediatric patients. The purpose of our study was to determine the arthroscopy-based diagnostic performance of 10-minute isotropic 3D TSE MRI for the detection of internal derangement in children with acute knee trauma.
Methods
Institutional review board approval was obtained for prospective data collection, and informed consent and assent were obtained from all parents and children, respectively. The final study group consisted of 60 children (38 boys, 22 girls; 11 (2-16) years-of-age) with acute knee trauma who underwent 10-minute isotropic 3D prototype CAIPIRINHA SPACE MRI at 3 T and subsequent arthroscopic knee surgery. Two fellowship-trained musculoskeletal radiologists retrospectively evaluated the MRI studies independently and resolved discrepancies through consensus. Outcome variables included image quality, motion artifacts, meniscal abnormalities, cruciate ligament tears, and cartilage lesions. Statistical analysis included the diagnostic performance of MRI with arthroscopy as the reference standard and inter-reader agreements using kappa statistics.
Results
All studies were suitable for diagnostic interpretation with good-to-very-good image quality and little-to-no motion degradation in the majority of cases. The sensitivities/specificities/accuracies of MRI were 0.93/0.93/0.93 for 15/60 (25%) medial meniscal tears, 0.95/0.90/0.92 for 21/60 (35%) lateral meniscal tears, 0.83/1.0/0.92 for 10/60 (17%) discoid menisci, 1.0/0.95/0.98 for 16/60 (27%) anterior cruciate ligament tears, 1.0/0.95/0.98 for 2/60 (3%) posterior cruciate ligament tears, 1.0/1.0/1.0 for 5/60 (8%) osteochondritis dissecans lesions, and 0.71/0.97/0.84 for 48 (13%) defects in 360 cartilage segments. The inter-reader agreements were overall good-to-very-good (kappa, 0.730 -1.00).
Conclusion
10-minute isotropic 3D TSE MRI of the knee is feasible in children with acute knee trauma and yields high diagnostic accuracies for the diagnosis of internal knee derangement. Accuracies for the detection of meniscal tears, discoid menisci, anterior and posterior cruciate ligament tears, osteochondritis dissecans lesions, and cartilage defects ranged from 84-100%. Using previously published protocols for pediatric 2D MRI knee exams with total acquisition times of 25 minutes as a benchmark for traditional MRI, a 10-minute protocol could increase the efficiency by a factor of two or more, and thus substantially improve the availability of MRI and timely care for children with acute knee trauma.
| Diagnostic performance of MRI for the diagnosis of internal knee derangement | ||||||||
|---|---|---|---|---|---|---|---|---|
| Entity | Reader | Kappa | TP | FPJ | TIM | FP | Sens. | Spec. |
|
Medial Meniscus
Tear (Prevalence: 15/60, 25%) |
A | 0.822 (0.655 −990) | 14 | 1 | 42 | 3 | 93% (68-100%) | 93% (82-99%) |
| B | 13 | 2 | 43 | 2 | 87% (60-98%) | 96% (85-99%) | ||
| Consensus | 14 | 1 | 42 | 3 | 93% (68-100%) | 93% (82-99%) | ||
|
Lateral Meniscus Tear
(Prevalence: 21/60, 35%) |
A | 0.861 (0.730-0.993) | 20 | 1 | 35 | 4 | 95% (76-100%) | 90% (76-97%) |
| B | 20 | 1 | 35 | 4 | 95% (76-100%) | 90% (76-97%) | ||
| Consensus | 20 | 1 | 35 | 4 | 95% (76-100%) | 90% (76-97%) | ||
| Discoid Lateral Meniscus (Prevalence: 10/60, 17%) | A / B | 1.000 (1.000-1.000) | 5 | 1 | 54 | 0 | 83% (52-98%) | 100% (97-100%) |
| Anterior Cruciate Ligament (Prevalence: 16/60, 27%) | A | 0.960 (0.881 − 1.000) | 16 | Q | 43 | 1 | 100% (79-100%) | 98% (88-100%) |
| B | 16 | Q | 42 | 2 | 100% (79-100%) | 95% (85-100%) | ||
| Consensus | 16 | 0 | 42 | 2 | 100% (79-100%) | 95% (85-100%) | ||
| Posterior Cruciate Ligament (Prevalence: 2/60, 3%) | A / B | 1.000 (1.000- 1.000) | 2 | 0 | 58 | 0 | 100% (40-100%) | 100% (97-100%) |
| Medial Femoral Condyle Osteochondrit is dissecans (Prevalence: 5/60, 8%) | A / B | 1.000 (1.000- 1.000) | 5 | 0 | 55 | 0 | 100% (48-100%) | 100% (94-100%) |
| Cartilage Defects (Prevalence: 48/360, 13%) | A | 0.730 (0.618 − 0.843) | 37 | 13 | 304 | 10 | 74% (60-85%) | 97% (94-98%) |
| B | 35 | 16 | 300 | 11 | 68% (54-81%) | 96% (94-98%) | ||
| Consensus | 34 | 14 | 303 | 9 | 71% (56-83%) | 97% (95-99%) | ||