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[Quantitative study on mechanoreceptors in tibial remnants of ruptured anterior cruciate ligament in human knees].

OBJECTIVE
To evaluate the survival condition and quantitative variation of mechanoreceptors in the tibial remnant of ruptured anterior cruciate ligament (ACL) in human knees.


METHODS
Between April 2009 and May 2010, 60 patients who underwent arthroscopic ACL reconstruction were included and divided into 4 groups according to the time of injury, with 15 patients in each group. In group A, there were 14 males and 1 female aged 20-37 years (mean, 27 years); the injury was caused by traffic accident in 5 cases and by sports in 10 cases, and the time between injury and surgery was not more than 3 months. In group B, there were 14 males and 1 female aged 17-43 years (mean, 24 years); the injury was caused by traffic accident in 2 cases and by sports in 13 cases; and the time between injury and surgery was 3 to 6 months. In group C, there were 11 males and 4 females aged 16-53 years (mean, 28 years); the injury was caused by traffic accident in 2 cases and by sports in 13 cases; and the time between injury and surgery was 6 to 12 months. In group D, there were 12 males and 3 females aged 18-41 years (mean, 26 years); the injury was caused by sports in 11 cases, and the other 4 cases had no defined etiology; and the time between injury and surgery was more than 12 months. Specimens were donated by the volunteers from the anteromedial side of the ACL tibial remnant (40 slices per specimen) and stained via immunohistochemical method. The type, size, and quantity of mechanoreceptors were observed under light microscope.


RESULTS
Totally 80 Ruffini-like corpuscles, 8 Pacini-like corpuscles, 5 atypical neural endings and no distinct Golgi organ-like corpuscles were observed under light microscope in 60 specimens (2 400 slices) of 4 groups. There was no obvious difference in size and type of mechanoreceptors among 4 groups. However, some degenerative and atrophic changes could be observed in the specimens of group D. The total number of mechanoreceptors was 31 (35.2%) in group A, 22 (25.0%) in group B, 23 (26.1%) in group C, and 12 (13.7%) in group D. There was no significant difference (P > 0.05) in Ruffini-like corpuscles and Pacini-like corpuscles among 4 groups. Mechanoreceptors were found in 9, 8, 9, and 6 patients in groups A, B, C, and D, respectively; the detection rates were 60.0%, 53.3%, 60.0%, and 40.0%, respectively; showing no significant difference (P > 0.05).


CONCLUSION
The mechanoreceptors in tibial residual of ruptured ACL have a long survival without obvious degeneration and atrophy within 12 months. So it may contribute to restoration of proprioceptive function after operation if the remnant is preserved during ACL reconstruction.