| Backgroud and purpose: The anterior cruciate ligament(ACL) is an important structure for the stability of the knee joint. Because of its unique anatomy and the articular enviroment, the capability of self-repair is limited and always can not heal naturally. Surgical reconstruction using biologic graft has gradually become the major method in the treatment of the anterior cruciate ligament–deficient knee. Currently recommended graft choices for ACL reconstruction include biological autograft and allograft materials. The bone-patellar tendon-bone graft is the most widely used biological graft both in autografts and allografts. Currently, there still exist heated debase on which graft should be selected. Quite a few comparative research concerned about which graft should be selected, but few concerned about bone-patellar tendon-bone between autograft and allograft. Bone tunnel enlargement is a common phenomenon following reconstruction of the anterior cruciate ligament. Most reports dealing with tunnel enlargement derived their data from direct two-dimension measurement of the diameter between the two sclerotic margins of the bone tunnel at its widest dimension perpendicular to the longitudinal axis of the bone tunne on plain radiographs. As a matter of fact, it is quite hard to distinguish the exact tunnel borderline through radiographs. Magnetic resonance imaging provides a harmless tool exempt from x-ray exposure and an accurate method sensitive to the signal change of marrow and soft tissu around the tunnel. The aim of this study is to compare the biological remodeling process of bone-patellar tendon-bone between autograft and allograft through biomechanical, histological and ultrastructural analysis, and to establish the correlation between MRI appearance and histological finding of the graft and the tibial bone tunnel; and to study the preliminary clinical effects of ACL reconstruction and as well as to use MRI as a method to evaluate the remodeling process of the graft and the tibial bone tunnel after surgery . Methods: 1. The fate of autogenous and allogenous bone-patellart tendon-bone were observed and compared histologically and biomechanically at 12 weeks and 24 weeks after ACL reconstruction in dogs whose one knee was transplanted with autograft while the other with allograft. MRI were performed at 12 weeks and 24 weeks after sacrifice. 2. A clinical research was done on 50 cases with unilateral ACL rupture. Isometric endoscopical ACL reconstruction were performed using bone-patellar tendon-bone autograft (n=20) or allograft (n=30). All the patients complied the same rehabilitation program after surgery. IKDC 2 000 and Lysholm subjective questionnaire were sent to those patients at 3, 6, 12, 18 months after ACL reconstruction, respectively. IKDC 2 000 knee examination were performed at 12 and 18 months. MRI examination were performed every 3 months for both groups. Results: 1. The animal experiment showed there had a very significant increase on the maximum tensile load at 24 weeks in both autograft and allograft and no significant difference presented between autograft and allograft at 24 weeks after surgery, although there existed some difference on the maximum tensile load at 12 weeks after reconstruction. The tidemark line was identified at 12 weeks and very similar to the normal one at 24 weeks in autograft group and discontinuous and irregular in allografts. The rate of remodeling process was somewhat faster in autografts than in allografts, but there showed similar remodeling process between two groups 24 weeks after implantation. The proportion of large-diameter fibers were (11±5)% and (17±4)% at 12weeks, and were (2±1)% and (4±2)% at 24 weeks, respectively. The proportion of small-diameter fibers were(89±5)% and (83±4)% at 12 weeks, and (98±1)%和(96±2)% at 24 weeks, respectively. Meanwhile We found the ring-shaped low-signal area around the bone tunnel on magnetic resonance image was the newly formed woven bone under light microscopy. 2. Clinical research showed residual anterior knee pain and patellofemoral crepitus were more likely to occur in autograft group, but there showed almost no significant difference in knee stability and the final subjective and objective evaluation of 2000 IKDC and Lysholm-Tegner score between the two groups. MRI analysis showed that there was a slower process of "ligamentation"in allograft group, 12 months for autograft while15 to 18 months for allograft. Most of the tibial bone tunnel enlargement occurred at the entrance of the bone tunnel. The percentage of the tibial tunnel enlargement was significantly higher within the first 6 weeks after surgery, yet there existed no significant difference between autograft and allograft at 6 weeks, 3, 6 and 9 months after surgery (p<0.05). Bone plug healing, with disappearance of the low-signal-intensity interface between the graft and osseous tunnel had achieved by 3 to 6months after surgery in autograft group and 6 to 12 months in allograft group. Conclusion: 1. The animal experiment showed similar remodeling and healing process between autograft and allograft following ACL reconstruction though the remodeling rate was somewhat faster in autograft . 2. From the prelimilary follow-up, there showed almost the same clinical outcome following bone-patellar tendon-bone reconstruction between autograft and allograft. 3. MRI evaluation of the graft and tibial tunnel provided valuable information for the assessment of the remodeling process following ACL reconstruction using bone-patellar tendon-bone autograft or allograft. |
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