DEVELOPMENTAL ANATOMY OF THE MENISCUS IN THE SKELETALLY IMMATURE OBJECTIVES and BACKGROUND • Although the morphologic anatomy of the meniscus is well-studied, meniscal development in the skeletally immature remains unclear. • In adults, the lateral and medial meniscus is thought to have proportionally less coverage over the tibial plateau in comparison to pediatric subjects. The purpose of this study is to investigate the anatomic relationship of the meniscus and tibial plateau in pediatric cadaveric specimens and how meniscus coverage of the tibial plateau changes with age. METHODS • Twenty-nine cadaveric pediatric knees ranging from 1 month to 36 months of age underwent gross dissection to expose the medial and lateral menisci. • Axial view photographs of the tibial plateau with attached menisci were taken. • Then, both lateral and medial menisci were removed. • Subsequent photos were taken of the tibial plateau with menisci removed. See Figures 1 and 2. – A ruler was placed in the field at the level of the plateau in each image to aid in quantitation of meniscus and plateau area. • A quantitative image-analyzer was used to calculate the area of the medial and lateral meniscus as well as the medial and lateral tibial plateaus. RESULTS • An independent samples t-test demonstrated a difference between the medial and lateral compartments. In Table 1 and Table 2, the difference in percent coverage between the medial (x = 52.66%) and lateral (x = 64.71%) meniscus is statistically significant (p<0.001**). • ANOVA indicated that medial and lateral meniscus percent coverage does not significantly vary by tibial plateau length (p > .05) DISCUSSION • Previously collected data by Bloecker et al. reported that in adults, the lateral meniscus covers approximately 59% of the lateral tibial plateau, while the medial covers about 50% of the medial tibial plateau. • This study indicated that the pediatric meniscus covered proportionally more area than the adult menisci. CONCLUSIONS • Understanding age-related meniscal anatomy may provide a better understanding of meniscus development. • Percent coverage of both the lateral and medial meniscus over tibial plateau length appears to decrease with age in pediatric cadaveric specimens. This decreasing trend is more apparent in specimens of 24 months to 36 months in age and may be further substantiated by data from older specimens. Acknowledgements: Allosource, Centennial, CO Correspondence: Kevin Shea : [email protected] 1 George Washington University, Washington, DC. 2 Georgetown University School of Medicine, Washington, DC. 3 St. Luke’s Hospital System, Boise, ID. 4 University of Minnesota, St. Paul, MN. 5 Texas Scottish Rite Hospital for Children, Dallas, TX. 6 The Ohio State University, Columbus, OH. TIBIAL PLATEAU LENGTH n MEDIAL MENISCUS % COVERAGE LATERAL MENISCUS % COVERAGE 2.25—2.75 cm (group 1) 8 53.66% 62.99% 2.75—3.25 cm (group 2) 7 54.79% 63.92% 3.25—3.75 cm (group 3) 6 56.01% 61.84% 3.75—4.5 cm (group 4) 6 52.87% 63.62% Mean 27 52.66%** 64.71%** Age n Medial meniscus area/ Medial plateau area Lateral meniscus area/ Lateral plateau area 1 month 5 55.46% 67.84% 3 months 5 54.58% 65.91% 4 months 6 55.85% 60.44% 5 months 2 55.78% 67.62% 10 months 2 50.02% 64.37% 12 months 4 47.79% 64.81% 24 months 4 40.89% 69.17% 36 months 1 51.88% 54.19% FIGURE 2. Axial view of tibial plateau with the menisci removed. FIGURE 1 REFERENCES: Bloecker K, Wirth W, Hudelmaier M, Burgkart R, Frobell R, Eckstein F. Morphometric Differences between the Medial and Lateral Meniscus in Healthy Men - A Three-Dimensional Analysis Using Magnetic Resonance Imaging. Cells Tissues Organs [serial online]. March 2012;195(4):353-364. Available from: Academic Search Complete, Ipswich, MA. Nicolas G. Anchustegui 1 , Jessica F. Burlile, BA, BS 2 , Connor G. Richmond, BS 3 , Marc Tompkins, MD 4 , Henry B. Ellis, MD 4 , Philip L. Wilson, MD 5 , Laura C. Boucher, PhD, ATC 6 , Kevin G. Shea, MD 3 MEDIAL LATERAL FIGURE 2 TABLE 2. Percent meniscus coverage of the tibial plateau delineated by age. FIGURE 3. The percent coverage of the menisci and the area of the medial and lateral meniscus plotted against age and tibial plateau length. FIGURE 1. Axial view of dissected 3 month old male knee with the lateral and medial meniscus intact. MEDIAL LATERAL TABLE 1. Percent meniscus coverage of the tibial plateau delineated by tibial plateau length.