Histology of the torn meniscus: a comparison of histologic differences in meniscal tissue between tears in anterior cruciate ligament-intact and anterior cruciate ligament-deficient knees.

PURPOSE: The purpose of this case control study was to evaluate possible preexisting structural differences between torn menisci in anterior cruciate ligament-intact and anterior cruciate ligament-deficient knees.
MATERIALS AND METHODS: Subjects were prospectively enrolled into the study from new patient referrals to the orthopaedic clinic. Forty-four meniscal specimens were retrieved during routine arthroscopy. The anterior cruciate ligament-deficient group included 24 patients (15 men and 9 women, average age of 26.5 years, SD = 9.5) with 24 acute, displaced, longitudinal, bucket-handle tears of the medial meniscus in unstable, anterior cruciate ligament-deficient knees. The anterior cruciate ligament-intact group included 20 patients (14 men and 6 women, average age of 30.4 years, SD = 13.4) with similar tears in anterior cruciate ligament-intact knees. Longitudinal and transverse section specimens were stained with hematoxylin and eosin and safranin O, divided into zones based on proximity to the tear, and graded on safranin O uptake or tissue composition.
RESULTS: Descriptive statistics and chi2 analyses were used to assess differences between groups within each zone. Significant differences (P < .05) were observed between anterior cruciate ligament-deficient and anterior cruciate ligament-intact specimens stained with hematoxylin and eosin in zone 3 for both transverse and longitudinal cuts. Significant differences were not found between anterior cruciate ligament-deficient and anterior cruciate ligament-intact specimens stained with safranin O.
CONCLUSION: Longitudinal meniscal tears occurring in anterior cruciate ligament-intact knees may result from early degenerative disease processes. Attempted repair of this diseased tissue may fail to have a positive effect on long-term preservation of the meniscus.