| Objectives: To evaluate the feasibility of allogenetic cortial bone cross-pin used as aclinical fixation method in anterior cruciate ligament reconstruction based onbiomechanical and histological data and outcome of radiology.Methods: The first section, fresh deep frozen allogenetic cortical bone were machinedinto cross-pins wich is4.0mm in diameter and75.0mm in length. Biomechanicalparameters compared with Rigidfix were collected while cross-pins were tested inthree-piont-bending test and double-shear test. On the other hand the pull out test andcycling test were carried out in a goat model to reconstruct anterior cruciate ligamentwith achilles tendon autograft fixed by human4.0mm ACBCP and3.3mm Rigidfixserved as control. Maximum failure load, yield load and stiffness of fixation in singleload to pull out test were comparerd between two groups. Special stiffness anddisplacement at cycle1,30,200,400,1000was also compared in between. The secondsection, to test the biomechanical profile of ACBCP sterilized with colbat-60, ethyleneoxide and hydrogen peroxide low temperature plasma, the unprocessed ACBCP servedas control. The third section, goat ACBCP, Rigidfix and Endobutton (1.5mm loop) wereused to fix Achilles tendon in a goat ACLR model. Postoperative changes in X-ray andCT scan were studied. Histological evolution of radiology between ACBCP and hostbone was made while histological development of tendon-bone interface was alsoobserved. Moreover, the maximum failed load and stiffness of different fixations overtime (right after surgery,10weeks and24weeks) were compared in single load to pullout test.Results: Maximum failed load of4.0mm human ACBCP was88.008±4.852N inthree-point-bending test and1236.998±201.940N in double-shear test. Maximumfailed load of Rigidfix in double-shear test was807.929±110.511N. The maximumshear strength of ACBCP was significantly superior to that of Rigidfix, P <0.05. In single load to failure test ex vivo, yield load and maximum failed load of ACBCPfixation complexity (867.104±132.856N,1032.243±196.281N) different from thatof Rigidfix (640.935±42.836N and800.568±64.890N) significantly, P=0.000.However, there was no significant difference of stiffness between ACBCP group(247.116±31.897N/mm) and Rigidfix group (220.413±51.332N/mm). group, P=0.179. In cycling test ex vivo, the special stiffness and displacement at cycle1,30,200,400and1000exhibited no significant difference between ACBCP group and Rigidfixgroup, P>0.05. In animal test, there was no fracture of ACBCP.3of14specimensfixed with ACBCP incorporated to the host bone. Broken Rigidfix was found in1of14specimens. That all the soft tissue grafts of the two groups were pulled out from thefemoral tunnel was the failure mode of single load to failure test over10weekspostoperatively.24weeks after surgery, all the grafts of the two groups failed at thelevel of femoral tunnel entrance. No significant difference of the maximum failed loadand stiffness among groups were observed, P>0.05. All the grafts of the three fixationmethods healed to the bone tunnel. Bone tunnel enlargement of the three groups wasevaluated on CT scan. The average increases in diameter of ACBCP group werecomparable to those of Rigidfix group (P>0.05). The degree of tunnel enlargement inEndobutton group was higer than that of either ACBCP group or Rigidfix group,particularly from for the anteroposterior view (P <0.05).Conclusions: Allogenetic cortical bone cross-pin possesses satisfactory biomechanicalprofile, such as bending strength and shear strength; In single load to failure test ex vivo,the average maximum failed load and yield load of ACBCP group are superior to that ofRigidfix group which is suitable for an aggressive rehabilitation program. In animal test,either ACBCP incorporate to host bone or absorbed and substituted by fibroid tissue, itdosen’t compromise the fixation effect. |
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