Growth of The Pediatric Knee Meniscus: A Cadaveric Study

OBJECTIVES: The menisci of the knee (Figure 1) play a critical role in maintaining structural integrity, as well as in load bearing and shock absorption. In adolescent patients, meniscal tear is a very common sports injury, and is frequently associated with concomitant traumatic injuries including tibial eminence fracture or ACL tear. Depending on the severity of meniscal tear, surgical treatment options include arthroscopic partial or total meniscectomy, with a reported 78-88% success rate. Given the high incidence of pediatric meniscal injuries and reliance on landmarks to guide arthroscopic meniscus repair, surprisingly few human pediatric cadaveric studies are reported in the current literature. The primary purpose of our research was to evaluate the rates at which different zones of the meniscus rim lengthen with age during early adolescence. Our null hypothesis was that meniscus rim length is unrelated to patient age, tibial plateau width, or to lateral-medial meniscus width. METHODS: From images of 29 dissected cadaveric knee specimens between 1 month and 132 months of age obtained on a copy stand (14 left knee, 15 right knee), we made direct length measurements from the inner to outer meniscus rim at 45 degree intervals (12, 1:30/10:30, 3:00/9:00, 4:30/7:30 o’clock, 6 o’clock) using Autodesk Fusion 360 software (Figure 2). We also measured width between the outer medial and lateral meniscus rims, as well as CT measurements of coronal and sagittal width of the tibial plateau using OsiriX DICOM software. Generalized linear models were used to evaluate the associations of meniscal length measurements with age, tibial width, and meniscal width measurements. All statistical analyses were completed with a two-sided level of significance of 0.05. RESULTS: All meniscal length measurements were predicted to increase significantly as age increases (p < 0.01 for all), as coronal tibial width increases (p < 0.05 for all), and as lateral-medial meniscal width increases (p < 0.001 for all). Other than the lateral 3 o’clock measurement (p = 0.119), all meniscal length measurements were predicted to increase significantly as sagittal tibial width increases (p < 0.05 for the rest). Interestingly, the posterior zones of the medial meniscus (6 o’clock and 4:30/7:30 o’clock) were found to increase in length at a faster rate than the anterior zones (Figure 3), which supports our hypothesis that increased weight bearing is correlated with meniscus growth. The same length correlation was not identified in the lateral meniscus. Furthermore, the anterior zones of the medial meniscus (12 o’clock and 1:30/10:30 o’clock) were found to have the slowest rate of growth, presumably due to reduced weight bearing function anteriorly. CONCLUSIONS: We reject our null hypothesis that meniscus rim length is unrelated to age, tibial plateau width, or to lateral-medial meniscus width. Surprisingly, the posterior zones of the medial meniscus were found to grow at a faster rate with age compared to the anterior zones, which we attribute to the effect of increased weight bearing experienced by the posterior zones during knee bending exercise. Additionally, the anterior, lesser-weight bearing regions of the medial meniscus were found to develop at the slowest rate out of all zones measured. Further studies are underway to generalize these observations to all adolescent patients. This information will be useful for meniscus repair and transplantation surgical planning.