| Objective:Knee osteoarthritis is a common disease in aging society.Medial opening wedge high tibial osteotomy(MOWHTO)is of great application value.However,the existing surgical techniques and internal fixation systems still cannot meet the clinical needs,which restricts the promotion and application of this technique.The purpose of this study is:(1)In view of the existing problems such as patellar lower position after MOWHTO operation,lack of protective mechanism of posterior tibial blood vessels during operation,and damage of medial stability of the knee joint,the osteotomy line was redesigned based on the observation of anatomical structure around the knee joint by imaging and anatomy.The feasibility of the new surgical method was verified from the aspects of anatomy,geometry and biomechanics.(2)Clinical studies were carried out to compare the new surgical method-Anterior popliteus transtibial tuberosity high tibial osteotomy(APTT-HTO)and Biplanar-high tibial osteotomy(Biplanar HTO),to verify the operability and effectiveness of the surgery.(3)In view of the non-anatomical design of the existing internal fixation system,the screw direction did not consider the alignment of blood vessels,the bone plate stress concentration,the lack of posterior medial support of the tibial plateau and other problems,new bone plate shape was designed based on the three-dimensional computer aided design(CAD)system,and the finite element analysis(FEA)technology was used to screen and verify the optimal bone plate shape.Methods:(1)Based on imaging observation,intraoperative observation of patellar tendon insertion,and verification of cadaver specimens,the specific partition of patellar tendon insertion at tibial tubercle was determined,and the osteotomy line was designed.Compared with Biplanar-HTO,Biplanar-distal tibial tuberosity osteotomy(Biplanar-DTO)and Uniplanar-distal tibial tuberosity osteotomy(Uniplanar-DTO),the relationship between osteotomy lines and anatomical structures in different osteotomy methods was observed,and the area of osteotomy and the volume of wedge space after splitting were measured.FEA static mechanical analysis technique and classical mechanical testing methods were used to observe the compressive performance,stress distribution of bone and internal fixation and the maximum compressive stress that could be sustained by different osteotomy methods.(2)A total of 28 patients who received MOWHTO treatment for medial compartment osteoarthritis of knee joint in the Affiliated Hospital of Guizhou Medical University from August 2020 to January 2022 were included.According to different surgical methods,they were divided into APTT-HTO group and Biplanar HTO group.The operative time,intraoperative fluoroscopy times and postoperative wound drainage volume of the two groups were recorded and compared.The patients were followed up to 12 months after surgery,and the postoperative visual analog scale(VAS)and the Knee society score(KSS)were compared between the two groups.The postoperative changes of patellar height and posterior tibial slope(PTS)were observed to compare the efficacy of the two surgical methods.(3)The anatomical surface of the medial side of the tibia was extracted based on the CT data of the lower limbs of healthy adults.According to the anatomical and mechanical characteristics of the proximal tibia and APTT-HTO,the possible shapes of the bone plates(AA plate,AP plate,PA plate and PP plate)were designed and drawn.The shape fit of the bone plates was observed by using digital modeling and 3D printing technology and the autopsy experiment.The orientation of the locking screw is limited based on the position of the neurovascular sheath behind the knee joint.The FEA technique was used to observe the stress distribution,axial displacement and spacing fretting of different internal fixation models under different stress environments,and compared with T-shaped bone plates to screen the optimal bone plate shape.Results:(1)The insertion of the patellar tendon was only in the A and B areas of the tibial tubercle.The osteotomy line of APTT-HTO was designed to be close to the lower edge of the insertion of the patellar tendon,and at the same time ran in the area covered by the popliteal muscle.Compared with the biplanar osteotomy and uniplanar osteotomy,the osteotomy line was completely covered by the popliteal muscle.The wedge-shaped bone defect volume in the APTT-HTO group was 7.20±0.26 ml,and the difference was not statistically significant compared with Biplanar HTO group and Biplanar DTO group(P>0.05).The area of osteotomy in the APTT-HTO group was the largest(3859.28±143.40 mm~2).It was significantly larger than Uniplanar-DTO(2143.02±30.97 mm~2),the difference was statistically significant(P<0.05).The maximum axial displacement of the tibial plateau in the APTT-HTO group and the Uniplanar DTO group was the smallest under the mechanical conditions of standing,sitting-standing instant,walking maximum stress instant,and the difference was statistically significant compared with the Biplanar HTO group and the Biplanar DTO group(P<0.05).But there was no statistically significant difference in the maximum equivalent stress of the hinge between the four groups(P>0.05).The APTT-HTO group and Uniplanar DTO group had the smallest maximum equivalent stress of bone plates,while the APTT-HTO group had the smallest maximum equivalent stress of screws,and the difference was statistically significant(P<0.05).The simulated bone compression performance tests of different osteotomy methods showed that the four osteotomy methods had similar force-displacement curves,and the APTT-HTO group had the maximum axial pressure 1499.33±79.00N,which had statistical significance compared with Uniplanar DTO group(P<0.05).(2)Among the 28 patients,15 cases in the APTT-HTO group had an average varus correction degree of 12.19±4.85°,and 13 cases in the Biplanar HTO group had an average varus correction degree of 11.23±3.02°.The operative time and intraoperative fluoroscopy times in APTT-HTO group were lower than those in Biplanar-HTO group,and the difference was statistically significant(P<0.05).Significant improvement was observed in pain VAS and KSS scores in both groups(P<0.05).In the APTT-HTO group,PTS(9.32±2.04°),Caton-Deschamps index(CDI)(0.95±0.11)were obtained 12 months after surgery.There was no statistically significant difference in PTS and CDI compared to their preoperative values.(P>0.05).In the Biplanar-HTO group,PTS(13.27±1.99°)at 12 months after operation was significantly higher than that before operation(8.86±1.99°),CDI(0.64±0.10)was significantly lower than that before operation(0.97±0.16),and the difference was statistically significant(P<0.05).(3)The four types of bone plate models(AA,AP,PA and PP)3D printed after modeling with Solid Works software can achieve good anatomical adhesion of the head end,body and tail end,and can achieve good coverage of the anterior medial and posterior medial tibial platform.The maximum axial displacement of tibial plateau,the maximum equivalent stress of hinge,the maximum equivalent stress of bone plate and the maximum equivalent stress of screw in the PA plate group were the smallest under the mechanical conditions of standing,sitting-standing instant,walking maximum stress instant,and the differences were statistically significant(P<0.05).By drawing the curve of axial displacement change at points a,b and c,it can be seen that the overall slope of the curve of PA plate group is the lowest,and the curve is closest to the X-axis,which can effectively prevent the increasing of PTS and the loss of the height of the open gap.Conclusions:(1)The APTT-HTO surgical program designed based on the precise positioning of patellar tendon insertion and the direction of popliteal muscle can fully protect the insertion of patellar tendon and maintain the height of patella.The osteotomy line runs within the coverage of popliteal muscle,which increases the vascular protection mechanism behind the proximal tibia compared with the existing surgical methods.Secondly,APTT-HTO has a larger osteotomy surface area and does not increase the wedge-shaped bone defect volume compared with biplanar osteotomy,which has potential bone healing advantages.Finally,APTT-HTO osteotomy line design does not increase hinge stress,and can reduce the stress concentration of bone plates and screws,with good compression performance.(2)Both APTT-HTO and Biplanar HTO can effectively treat medial compartment osteoarthritis of knee joint with varus deformity.With the improvement of lower limb alignment,pain symptoms can be significantly reduced and knee joint function can be improved.Compared with Biplanar HTO,APTT-HTO can effectively avoid the occurrence of postoperative patella low and prevent the increasing of PTS.Its single planar osteotomy design is simpler to operate and can reduce the operative time and intraoperative fluoroscopy times.(3)Based on the characteristics of the curve of the medial side of the tibia,the position of the blood vessels around the knee joint and the mechanical characteristics of the proximal tibia,all the bone plates designed can fit well to the medial bone surface of the tibia,effectively reducing soft tissue harassment.The PA plate screened by FEA technology can provide good posteriorally medial support of the tibial plateau.At the same time,the internal fixation stress can be well dispersed to avoid stress concentration,while effectively resisting axial pressure,maintaining correction angle and postoperative PTS. |
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