Changes Of The Mechanoreceptors In The Different State Remnant Stump Of The Ruptured ACL

Objective:To investigate the morphology and quantity of mechanoreceptors in the different state remnant stumps of the injured anterior cruciate ligaments(ACLs).Methods:Complete ACL stump specimens were collected from 57 volunteer patients who underwent arthroscopic ACL reconstruction surgery.The time interval from injury to surgery was recorded.The patients were divided into two groups according to preoperative Kneelax joint measurement results:Group 1(The difference between the measurement?6mm)and Group 2(The difference between the measurement>6mm).Recordingboth groups'type of ligament injury stump,ACL stump stuck to the posterior cruciate ligament(type A),ACL stump adhesion at the top of the intercondylar fossa(type B),ACL stump stuck in the medial femoral condyle lateral wall(type C),ACL stump free from the joint cavity(type D).Group 1:a total of 20 cases,6 males and 14females;aged 19 to 46 years,mean age 31 years.Cause of injury:12 cases of traffic accidents,6 cases of sports injuries,2 cases because of falling reasons.Time from injuries to surgery for 4 to 110 days,the average time from injury to surgery for 37 days.Group 2:A total of 37 cases,23 males and 14 females;aged 19 to 49 years old,with an average age of 33 years.Causes of injury:19 cases of traffic accidents,sports injuries in 10cases,8 cases because of falling reasons.Time from injuries to surgery for 26 to 522 days,the average time from injury to surgery was 205 days.In group 1,there were 20specimens:0 in type A,3 in type B,17 in type C and 0 in type D.Group 2 included 37cases of ligament specimens,including 20 cases of type A,1 case of type B,2 cases of type C and 14 cases of type D.After H&E staining and immunohistochemical labeling,the morphology,type,and quantity of the mechanoreceptors were observed under an optical microscope.The relationship between the changes of the mechanoreceptors in the remnant stumps and the morphology of the ligament stump/the affected knee stability/the time from injury to surgery were analyzed.Results:20 specimenswere included in Group 1.While 37 specimens were included in Group 2.The distributions of the 4 types of the remnant stumps between the two groups were significantly different(x~2=49.406,P=0.000).The distributions of the 4 types of mechanoreceptors between the two groups were significantly different(x~2=13.84,P=0.002).The number of the mechanoreceptors was positively correlated with the affected knee stability(r=0.63,P=0.018).The number of the mechanoreceptors was not obviously correlated with the time from injury to surgery in Group1(r=-0.37,P=0.136),while it was negatively correlated with the time from injury to surgery in Group 2(r=-0.51,P=0.022).Conclusion:After ACL rupture,the ligament stump in some patients still connect the femur and the tibia to maintain the knee stability,thus the mechanoreceptors in some ACL stump can exist for a long time after injury.