Utility of Adult-Based Discoid Lateral Meniscus Diagnostic Criteria in a Pediatric Population.

BACKGROUND: Commonly cited discoid lateral meniscus (DLM) imaging definitions are based on adult magnetic resonance imaging (MRI) measurements. This pathology commonly presents in pediatric populations; however, whether accepted adult measurements reliably apply to children and adolescents is unknown.

PURPOSE/HYPOTHESIS: This purposes of the study were to determine (1) the utility of applying adult-accepted MRI definitions of DLM to pediatric patients, (2) whether sex differences affect the applicability of the criteria, and (3) whether MRI magnet strength and/or tear presence affect MRI measurements for diagnosing DLM in pediatric patients. It was hypothesized that MRI criteria for DLM would be similar in adults and pediatric patients.

STUDY DESIGN: Case series; Level of evidence, 4.

METHODS: A total of 100 consecutive MRIs from pediatric patients with DLM were evaluated, with 91 scans included. Two study authors independently reviewed the MRIs, evaluating meniscal height and width on sagittal and coronal images, "bow tie signs" on sagittal images, tibial sagittal and coronal width, and tear presence. For analysis, MRI magnet strength was dichotomized into high (>1.5 T) and low (<1.5 T) groups.

RESULTS: The mean age of the patients at MRI evaluation was 12.3 ± 3.4 years; 51% of the patients were male, and 56% of the scans were of left knees. Included patients with DLM showed a mean of 3.68 bow tie signs, a sagittal total anterior to posterior meniscal width/tibial width ratio of 73%, a coronal meniscal width/tibial width ratio of 30%, and a coronal, transverse width of the lateral meniscus at the midportion of the meniscal body of 20.6 ± 7.7 mm. The MRI tesla strength of the images included in this study ranged from 0.3 to 3. It was determined that high- versus low-resolution MRI scans did not affect the inter- or intraobserver reliability of the MRI measurments ( P > .05). However, several measurements showed improved intraclass correlation coefficients with increased tesla strength.

CONCLUSION: This study confirms that pediatric patients with DLM, diagnosed by board-certified pediatric sports medicine orthopaedic surgeons, have measurements on MRI consistent with adult DLM diagnostic criteria. This finding held true regardless of sex or MRI tesla strength. Pediatric patients with DLM had >3 bow tie signs, >70% sagittal tibial plateau coverage, >14 mm coronal width, and >20% coronal tibial plateau coverage on MRI.