Summary

This arthroscopic meniscus mobility study hopes to establish normal age-based arthroscopic meniscal mobility and meniscal rim width to aid in saucerization and post-operative outcomes.

Abstract

Background

Pediatric patients with isolated meniscal pathology are commonly associated with a discoid meniscus and often present with peripheral rim instability1. Following saucerization, evaluation of peripheral rim instability is routine, however normal mobility of pediatric menisci when probed is yet to be studied. Restoring normal meniscus stability after discoid meniscus resection is critical, as central region discoid meniscus tissue excision can significantly increase abnormal meniscus motion and lead to knee mechanical symptoms.

Hypothesis

We hypothesized establishing a normal age-based arthroscopic meniscal mobility and meniscal rim width would aid in saucerization and post-operative outcomes.

Methods

Fresh-frozen pediatric cadaveric knee specimens were arthroscopically evaluated by fellowship-trained pediatric sports medicine surgeons. Surgeons were instructed to probe the anterior, body, and posterior horns of the medial and lateral menisci during the diagnostic arthroscopy. Mobility was described as percent mobile translation as a reference of the tibial plateau. Measurements of medial and lateral 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 to determine appropriate translation. Descriptive data and Mann-Whitney U test were reported.

Results

33 knees with a mean age 7.15 years (3 - 11), 52.5% females, and 48.8% left knees. The majority of each horn of the medial meniscus translated 0-20% (84% anterior, 92% body, and 96% posterior), seven specimens were noted to have translation of the horn > 20 %. The lateral meniscus demonstrated increasing variability in terms of translation with 44% of the anterior horn and 40% of the posterior horn translating > 20%. Three lateral meniscus posterior horns (12%) translated > 50% without morphologic features of a discoid meniscus. Globally, the medial and lateral meniscus size increases with age with the lateral meniscus measuring larger than the medial meniscus. Additionally, when specimens were grouped by age, widths for the medial meniscal body, posterior horn, distance between free edge, and distance between roots (p=0.042; p=0.027; p=0.032; p=0.036) and lateral meniscal anterior horn and distance between free edge were found to be significant (p=0.031; p<0.001).

Conclusion

Normal lateral meniscal morphology demonstrates some mobility with some more than 50% of the tibial plateau. Medial meniscus is relatively immobile. Meniscal rim size, when measured arthroscopically, increases with age which will be useful in determining the magnitude of saucerization. Focusing upon avoiding too much meniscus instability after discoid meniscus saucerization may be essential to improving outcomes for this challenging condition.