How Much Meniscal Translation Is Normal? A Pediatric Physiological Arthroscopic Meniscus Mobility Study.

BACKGROUND

Pediatric patients with a discoid meniscus often present with peripheral rim instability. Following saucerization, evaluation of peripheral rim instability is routine. However, the normal mobility of pediatric menisci when probed has yet to be studied. The purpose of this study is to establish normal age-based arthroscopic meniscal mobility and meniscal rim width parameters to aid the treating surgeon in identifying an unstable peripheral rim and determining the appropriate amount of saucerization.

METHODS

Forty fresh-frozen pediatric cadaveric knee specimens under the age of 12 years were arthroscopically evaluated. Surgeons were instructed to probe the anterior horn, body, and posterior horn of both the medial and lateral menisci during the diagnostic arthroscopy. Mobility was described as a percentage of mobile translation, with the tibial plateau as the reference. Measurements of meniscal horn widths were performed using an arthroscopic probe. Menisci were excluded if they had abnormal morphology or if visualization of the compartment was inadequate. Descriptive data and Mann-Whitney U tests were reported.

RESULTS

Each horn of the medial meniscus typically translated 0% to 20%, while the lateral meniscus demonstrated greater variability in mobility across the tibial plateau -51.6% of the anterior horn, 48.2% of the menisci at the level of the popliteus, and 29.0% of the posterior horn translated more than 20%. Globally, the medial and lateral meniscus width increased with age, and the lateral meniscus measured larger than the medial meniscus. When specimens were stratified by age group, widths for the medial posterior horn, distance between the meniscal free edge, and distance between roots ( P =0.004; P =0.02; P <0.001) and lateral anterior horn, body, posterior horn, distance between free edge, and distance between the meniscal roots were found to be significantly different ( P =0.04, 0.01, 0.002, 0.01, and 0.04).

CONCLUSION

Lateral meniscal morphology demonstrates more mobility compared with the medial meniscus. Meniscal rim size, when measured arthroscopically, varies between horns and increases with age, which may be useful in determining the extent of saucerization.

LEVEL OF EVIDENCE: Level IV.