Experimental Study On Changes Of Proprioceptors After Anterior Cruciate Ligament Reconstruction

Object:The assessment and functional reconstruction of anterior cruciate ligament (ACL) injury is one of the most important topics in orthopedics,sports medicine and rehabilitation medicine. Even though ligament reconstruction of the ruptured ACL can restore the mechanical integrity of the knee, the proprioception still can not restore to the level before the injury.As a result, the proprioception reconstruction of ACL injury is of great significance.But domestic there have still been few researches related with proprioceptor morphology of ruptured ACL after reconstruction. The objective of the experiment is to investigate neurohistology changes during proprioception restore of the knee joint and to provide a theoretical basis on clinical rehabilitation treatments by observing the change of implant morphology and quantity after the anterior cruciate ligament reconstruction using patellar tendon autograft.Methods: 15 adult New Zealand white rabbits was used in this study.Experiment rabbits'one side of knee joint were selected randomly and performed anterior cruciate ligament reconstruction using patellar tendon autograft as experimental group , The contralateral side served as control group. Experiment rabbits were fixed on bench with supine position. After anesthesia satisfaction,we disinfected and spread aseptic towel.An arc incision about 3 cm on anteriomedialis of experiment rabbits hind legs was made. The patellar tendon was exposed and medial semi-patellar tendon was cut,at the length of 3cm and width 2cm or so. Two sides of patellar tendon were weaved and sutured with 3-0 dacron suture and reserved.Then the patella were dislocated to lateral direction and anterior cruciate ligaments thoroughly were exposed and excised completely.With genuflex 90°position, bone tunnels at the diameter 2.4mm of were drilled at anterior cruciate ligament amphi-insertions of femur and tibia. One extremity of tendon was drawn through bone tunnels of femur and tibia and engrafted into articular cavity.The position of patellar tendon was adjusted into the center of the knee. Door-shaped nails were nailed at external aperture of bone tunnels in proper positions. Two extremities of tendon were tensed and fixed using suture.Wound was flushed using Sodium Chloride. Articular capsule, subcutaneous tissue, skin were sutured layer by layer using 1# suture and bound with asepsis bandages. After operation, the knee joints of experimental rabbits were not be fixed, making them free-running. Penicilin was injected twenty thousand units each day for 7days. General state of health of the experimental rabbits were observed. At the end of third week, sixth week, twelfth week postoperatively, five experimental rabbits were sacrificed respectively with ear edge vein aeroembolism. Specimen of graft were incised at the upper,low insertions. The medial half of the patellar tendon of the other side knee joint was used as control group. The method of drawing the materials was as same as above. The specimen was fixed using buffer formaldehyde solution and then was performed histology, immunohistochemical study and image analysis to count the nerve immunohistochemical staining results of patellar tendon tissue respectively.Results: 1 General state of health observation:At second weeks postoperatively, every experiment rabbits appeared to be dropping. At nineth weeks postoperatively, 2cases appeared stiffness of knee joint and the range of motion was from 0°to 35°, which has been lasting for the end of experiment. As for the rest experiment rabbits, passive range of motion was normal. Postoperatively wound of reconstructed side healed normally and had no infection for every rabbits. 2 Observation of histomorphology aspects: In the control group, the normal rabbit patellar tendon using HE staining is dense collagen tissue. Collagen fibers line up in order and nuclear is uniformity and eumorphism. There was no hyperplasia of collagen fibers; In the experimental group tissues necrosis was key feature postoperative 3 weeks. There was fibroblasts in disorder and a zone of necrosis in central transplants which was collagen fiber bundle out of order and the quantity of the cells reduced. Postoperative 6 weeks in the experimental group, there was collagen with a relatively larger number and a more regularity alinement. Cells in graft has larger number that were mainly fibroblasts and cells and the fibers were disorder. The number of cells reduced in center department and necrotic tissue was still visible. Nucleus was round-shaped and cell proliferation could be seen. Postoperative 12 weeks, in the experimental group there was collagen with a relatively larger number and which mainly were fibroblasts and graft cells and fibers still showed the overall disorder. 3 Observation of immunohistochemical aspects:via microscope Pacini corpuscles,Ruffini corpuscles,morphologically unclassified sensory corpuscles and free nerve endings are visible. Pacini corpuscle were oval with multi-layered tunics like skin of onion with the thickness of 25-40μm;Ruffini corpuscle mostly appeared to be oval with a thin layer of connective tissue capsule via microscope,which had various sizes and shapes, the magnus for the 300-550μm with 100μm-thickness ectocyst and the small for the 180-300μm,with 10-50μm-thickness ectocyst.Free nerve endings mostly appeared to be non-medullated nerve branch and no encapsulation via microscope and there were no significant changes in their morphology postoperative 3 weeks, 6 weeks,12 weeks.4 Image analysis and calculation results aspects:the data were analysed statistically by the Wilcoxon signed-rank test.The median of Ruffini corpuscles were 3 at 3 weeks,4 at 6weeks , 6 at 12weeks postoperatively in the reconstruction group and 7 at 3 weeks,6 at 6weeks , 10 at 12weeks in the control group, which were lower in the reconstruction group (p =0.014, 0.046, 0.045). The median of Pacinian corpuscles were 2 at 3 weeks,4 at 6weeks,4 at 12weeks postoperatively in the reconstruction group and 5 at 3 weeks,8 at 6weeks , 8 at 12weeks in the control group,which were lower in the reconstruction group (p=0.013,p=0.011,p=0.015).The median of free nerve endings were 16 at 3 weeks, 18 at 6 weeks postoperatively and 25 at 3 weeks,26 at 6weeks, which were lower in the reconstruction group (p=0.036,p=0.045).The median of free nerve endings were 20 at 12weeks postoperatively.There were no significant differences between the control group and the reconstruction group(P=0.344), Postoperatively 3,6 weeks the total numbers of mechanoreceptors were significantly decreased and the differences were statistically significant between experimental group and control group (P<0.05).Postoperatively 12 weeks there was no significant statistical differences between the two groups(P>0.05).Conclusion:1 There were Pacinian corpuscles , Ruffini corpuscles morphologically unclassified sensory corpuscles and free nerve endings in patellar tendon.2 There was no significant morphology change on propriocept- ors of reconstructed implant.3 The quantity proprioceptors of reconstructed implant decreas- ed firstly and increased later,which was an indiction of proprio- ceptors regeneration.