| Study Background:As a kind of degenerative joint diseases, osteoarthritis is found in aged people commonly, and it is the most frequent joint disease in the word, whose sickness rate ascensuses quickly accompanied with the increasing age. The osteoarthritis can occur in all joints, accompanied with pain, engorgement, attrition murmur, deform and limitation of activity in corresponding joint. The soreness usually occurs after hyperactivity , abates after resting. Arthrodial cartilage's aegeneration and hyperosteogeny are the pathology characters of osteoarthritis. It usually occurs in knee joint, hip joint, spinal column and ankle joint. It occurs in knee joint most frequently, accounting for 41%.The final diagnosis rate of knee joint osteoarthritis is about 60%-70% in 60-70 years old, because the knee joint is one which endures more weight loading, activities, surgical trauma, exertion, pathogenic wind-cold easily. The KOA can lead to the affected limb's squatting and stair activity disturbance. The generally breakdown of arthrodial cartilage leads to joint function disturbance, enstrophe, flexion contracture abnormity, dearticulation, long-term bed, loss viability in advanced stage of affection. However, there is no method which can reverse the course of osteoarthritis, the pathogenetic condition will develop and aggravate in bulk of sufferers. So the study of pathogenesy and prevention-cure of osteoarthritis becames a hot point gradually.For the past few years the domain of biomechanics in medical science has developed quickly, and the high tibial osteotomy and anterior tibial tubercle advancement are applied generally in clinic as the important therapeutics for intermediate-stage osteoarthritis. The high tibial osteotomy cures the osteoarthritis by correcting line of hind limb force. After HTO, the abnormal axial ray's rectification of biomechanics can change the abnormal weight loading surface on the tibial plateau, change the burden of the joint, degrade intraosseous pressure, promote the formation of the new joint surface, relieve pain and disease. The anterior tibial tubercle advancement cures the chondropathy in patellofemoral joint complicated with KOA by increasing the force arm extending knee joint and degrade the pressure in patellofemoral joint. The chondropathy in patellofemoral joint complicated with KOA can induce corrodibility breakdown on patellofemoral joint, while the abrasion of osteophyma and corpus liberum can aggravate the damage of the joint surface. After ATTA, the reduction of the pressure of the patellofemoral joint will relieve the abrasion in the activity of extending the knee joint, meanwhile it also can relieve the symptom of pain.Now the biomechanics study's emphasis on correlated operation is knee joint, and the experiment object is cadaver's knee joint on the whole. However the research in the change of stress distribution in ankle joint need more reconstruction. In fact, knee varus not only induces the change of the gravimetric point and line of force, but also influences the biomechanics characters of neighbouring joint, and the line of force of the homolateral ankle joint will change too. The normal axial ray of hind limb is the hypothesis to guarantee reasonable stress distribution of extremity and joint. After the change of the axial ray of hind limb, the stress on the knee and ankle joints becames to disproportion, and the joint surfaces of the knee and ankle joints incline contrasting the ground. The ankle joint will occur chronic injury after a long time, and form traumatic arthritis accompanied with pain in corresponding joint. Otherwise knee exo-pendulum may occur in the patient suffered the KOA, whose knee joint swings outwards after the heel contact of affected limb, and it will aggravate unreasonable stress distribution and damage in the knee and ankle joints. The pain in ankle joint usually occurs in the patient who suffered severe knee varus, so the deep going study on the changes of knee and ankle joints' biomechanics character synthetically is very necessary, according with the basic characteristics of TCM of viewing the human body as an organic whole. Objective:To simulate the mechanism of the high tibial osteotomy and anterior tibial tubercle advancement, deal with the bone specimens of lower limb from the cadaver by installing different angles of varus and different heights of tibial tubercle advancement. Diversity values of force on tibiofemoral joint, patellofemoral joint, tibiotalus joint and ligament patellae were measured synchronously in the progress of compression and decompression with the system of computer-pressure transducer. And statistics will be analyzed to approach the effects of stress distribution in knee and ankle joints, the dependability between the changes of the stress in knee and ankle joints, according to comparing the two operations. Then visual field of the study of the KOA complicated with knee varus will be opened. Methods:Choose six cadaver hind limb specimens soaked in formalin, the tibiofemoral angles of which are measured strictly in 170°,fhe knee and ankle joints space of which are uniform, the arthrodial cartilages of which are integrity and lubricous, and the sclerotins of which are normal and no anatomical variation. Disarticulate the six cadaver hind limb specimens from hip joint, and take out of the patella tendon after rejecting soft tissue(use tensile force transducer to measure the change of patellar tendon by replacing the patellar tendon for the need of the experiment).However, remain anterior-posterior cruciate ligaments and medial-lateral meniscuses to avoid effection on normal stress distribution of knee joint, keep the integrities of the upper and infer tibiofibula ligaments to avoid destroying ankle mortise. Remain the integrities of tibiofemoral joint surface, patellofemoral joint surface, tibiotalus joint surface, to make up to six groups cadaver hind limb specimens(including femur, patella, tibia, fibula, talus).Firstly, we fix three screws respectively on tibial tubercle, 3cm above the condyles of femur, the center of patella. Secondly, we bend two Kirschner wires whose diameters are 2．5mm in one extreme for simulating quadriceps femoris tendon and ligament patellae. And we use them to connect knee joint matching the tensile force transducer. Permeate the center of the trochlea tali on the opposite side after drilling upwards a 4mm-diameter hole on the talus. The screw permeates the central hole on the ankle pressure transducer, and the surplus fraction inserts tibiotalus joint surface in the end. Owing to the central hole on the ankle pressure transducer and the central hole on tibiotalus joint surface in the tibia are bigger than the diameter of the screw, the ankle pressure transducer is keeping reactiveness in the progress of the experimentPlace pressure transducers with the volume of 15mm×15mm×5mm on medial-lateral tibia plateau, medial-lateral patellofemoral joint surface, the volume of 15mm×25mm×5mm on ankle joint, the volume of 30mm×30mm×5mm on femoral head. And fix the two cursors of angle transducers on shaft of femur and shaft of tibia. We fix the specimen on versatile experiment machine. The experiment machine pressurize downwards vertically in one pace, and the peak pressure is 30kg,then unload the burden in one pace。There are two groups: we set three postures in the first group, including uniform knee joint space (the tibiofemoral angle is 170°) , adding 3．5mm in the lateral knee joint space (the tibiofemoral angle is 180°), adding 7mm in the lateral knee joint space (the tibiofemoral angle is 190°). We also set three postures in the second group, including pulsing the ending point of simulative ligament patellae 0mm,5mm,lcm.The each three in the two groups overlap one by one, and we take a photograph in each posture. The process of loading repeats three times. In the process of loading and unloading, the genuflex angle of specimen was controlled at 20°with the angle transducers. All the output signals were real-time displayed, recorded as solitary documents in the computer's hard disc by the program compiled with DELPH5．0．This program can reappear the voltage plot of all the transducer according to the change of straining. And statistics will be analyzed to approach the effects of stress distribution in knee and ankle joints, the dependability between the changes of the stress in knee and ankle joints, according to the comparing of two operations styles. Result:Each group of data was taken a homogeneity test for variance in multiplicate samples by the means of Bartlett, and the variance result is homogeneous and comparable. The comparison among the means were run by the means of Student-Newman-Keuls test. There will be statistical difference when P<0．05, predominant statistical difference when P<0．01。1．The change of stress distribution in tibiofemoral jointThe data indicate that the change of stress distribution in tibiofemoral joint is very noticeable with the increasing tendency of knee varus when we set the simulated ligament patellae's height at Omm.Fixing knee joint flexion-angle of the specimen at 20°and setting the loading-force at 30kg. The tibiofemoral angle's change (170°→180°→190°) makes burden shift to medial side and increases the contact stress in medial tibiofemoral joint significantly. There are predominant statistics differences among three groups of data(P<0．01) , contrasted the lateral tibiofemoral joint. The stress percentage of the medial tibiofemoral joint increases noticeably too. There is predominant change in stress distribution in tibiofemoral joint with the increasing tendency of knee varus. The stress and pressure-percentage of medial tibiofemoral joint both increase predominantly. The HTO is a adverse process which makes burden shift to lateral side and relieves the contact stress in medial tibiofemoral joint by Wedge-shape cutting bone.2．The change of stress distribution in patellofemoral jointFixing the height of ligament patellae at 0mm, the contact stress of medial patellofemoral joint increases gradually with the tendency of knee varus's increasing, contrasted by the lateral one. When the tibiofemoral angle is 180°,the statistics difference appears(P<0．05) , the statistics difference is very predominant at 190°(P<0．01) . The pressure-percentage of medial patellofemoral joint increases predominantly too.The contact stresses of the medial and lateral patellofemoral joints degrade noticeable with ligament patellae's raising, When the height is 5mm,the statistics differences appear (P<0．05) , the statistics differences are very predominant at lcm(P<0．01) .In a word ,ATTA can degrade the contact stress in the patellofemoral joint in effect.3．The change of tensile force of the ligament patellaeThe tensile force of the ligament patellae increases gradually with the tendency of knee varus's increasing. When the tibiofemoral angle is 180°,the statistics difference appears(P<0．05) , the statistics difference is very predominant at 190°(P<0．01) . The tensile force of the ligament patellae diminishes gradually with simulated ligament patellae's raising. When the height is 5mm(P<0．05) ,the statistics difference appears, the statistics difference is very predominant at 1cm(P<0．01) .4．The change of stress distribution in ankle jointThe contact stress of lateral ankle joint (including anterolateral quadrant and posterolateral quadrant) increases gradually with the tendency of knee varus's increasing, while the contact stress of medial ankle joint (including anteromedial quadrant, posteromedial quadrant) diminishes gradually. When the tibiofemoral angle is 180°,the statistics difference appears (P<0．05) , and the statistics difference is very predominant at 190°(P<0．01) .In a word, the contact stress of lateral ankle joint increases gradually with the tendency of knee varus's increasing, contrasted by the medial ankle joint. This phenomenon is relevant to ankle joint' compensated valgoid when the hind limb of the patient suffered knee varus is in weight-loading condition. Conclusion:1．There is a very predominant change in stress distribution in tibiofemoral joint with the tendency of knee varus's increasing. The stress and pressure-percentage of medial tibiofemoral joint are increasing predominantly, contrasted by the lateral tibiofemoral joint. The HTO is a adverse process which makes burden shift to lateral side and relieves the contact stress in medial tibiofemoral joint by Wedge-shape cutting bone.2．ATTA can degrade the contact stress in the patellofemoral joint in effect, relieving the abrasion when knee joint extends and flexes.3．The contact stress of lateral ankle joint increases gradually with the tendency of knee varus's increasing, contrasted by the medial ankle joint. This phenomenon is relevant to ankle joint' compensated valgoid when the hind limb of the patient suffered knee varus is in weight-loading condition. As the tendency of knee varus increases gradually, the stress of ankle joint becames to disproportion and chronic injury, resulting in traumatic arthritis. This may be a factor that the pain of ankle joint occurs in the patient suffered serious knee varus. |
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