Histological features of the ACL remnant in partial tears

article i nfo Background:The aim of thisstudy was to investigate thehistological features of the remaining fibers bridging the femur and tibia in partial ACL tears. Methods:Twenty-six ACL remnantswere harvested frompatients whohad arthroscopiccriteriaconcordant with apartialtear.Histological analysisincludescellularity,bloodvessel density evaluationandcharacterizationof the femoral bony insertion morphology. Immunohistochemical studies were carried out to determine cells positive for α-smooth actin and for mechanoreceptor detection. Results: In these samples, a normal femoral insertion of the remnant was present in 22.7% of the cases. In 54% of the samples, substantial areas of hypercellularity were observed. Myofibroblasts were the predominant cell type and numerous cells positive for α-smooth actin were detected at immunostaining. Blood vessel density was increased in hypercellularity areas and in the synovial sheet. Free nerve endings and few Golgi or Ruffini corpus- cles were detected in 41% of the specimens. The cellularity was correlated to the time between injury to surgery (p =0 .001). Conclusion:Competent histological structures including a well-vascularized synovial sheet, numerous fibroblasts and myofibroblasts and mechanoreceptors were found in ACL remnants. These histological findings bring addi- tional knowledge towards the preservation of the ACL remnant in partial tears when ACL reconstruction or aug- mentation is considered. Clinical relevance: Descriptive laboratory study.