| BackgroundOsteochondral injuries of the talus（OLT）is the most common articular cartilage disease of the ankle,which mainly refers to the injury of articular cartilage and subchondral bone of the talus.OLT can lead to ankle pain,instability,osteoarthritis and even disability,affecting patients’ daily life.In recent ten years,with the vigorous development of foot and ankle surgery,the treatment strategies and technologies of talus osteochondral defects have changed with each passing day,and new clinical studies have emerged one after another,but the treatment options are still controversial.For asymptomatic lesions,conservative treatment can be recommended.Conservative treatment can alleviate symptoms in a short time,but it is easy to relapse due to insufficient healing of lesions.Symptomatic OLT with non-surgical treatment failure usually needs surgical treatment.The choice of surgical treatment depends on the stage,location and size of OLT.It is found that for lesions less than 150 mm2,arthroscopic microfracture treatment can achieve satisfactory results.For lesions larger than 150 mm2,the success rate of simple microfracture treatment is low,and open osteochondral transplantation can be used for treatment.OLT occurs more often in the medial region of the talus.Osteochondral transplantation usually requires medial malleolus osteotomy to achieve sufficient intra-articular exposure.Therefore,medial malleolus osteotomy has become an established method to enter the medial talus for the treatment of various injury diseases related to talus.Options for medial malleolus osteotomy include transverse,inverted U or V,crescent,oblique,biplane chevron osteotomy and step cut osteotomy.However,in addition to oblique,Chevron and step cut osteotomy,the above approach has limited intra-articular exposure because the osteotomy is located at or below the ankle level.Oblique osteotomy has simple operation and wide exposure range,but the structure of medial malleolus is unstable after operation,which is easy to lead to bone nonunion,rotation deformity and translation.At present,chevron osteotomy and step cut osteotomy are highly respected at home and abroad.These two osteotomies provide extensive exposure,extensive cancellous surface for healing,and have better internal stability.However,recently,more and more studies have shown that the above two traditional osteotomy methods will produce osteotomy surface displacement and form malunion,which may induce traumatic ankle arthritis.Studies have shown that the rate of malunion after biplane chevron osteotomy is 30%.Malunion occurs in 15 of 50 ankles（based on the displacement of more than 2mm on X-ray film）.In addition,the traditional medial malleolus osteotomy is easy to damage the posterior tibial tendon,so special attention should be paid to protect the posterior tibial tendon during osteotomy.Therefore,there is still a lack of a surgical method to solve the above problems in the field of medial malleolus osteotomy.This study intends to gradually complete the design,biomechanical analysis and clinical verification of the new medial malleolus osteotomy from three aspects:autopsy,finite element analysis and clinical application practice.To provide a new method and new idea for the surgical treatment of talus osteochondral injury.ObjectiveA new medial malleolus osteotomy technology is designed.The new medial malleolus osteotomy can minimize the osteotomy area and fully expose the injured part of talus cartilage.During the operation,it can safely avoid damaging the anatomical structure of the medial malleolus.There is no displacement of the osteotomy surface after the operation and has good stability of the medial malleolus.MethodFirstly,the anatomical study of the ankle was carried out,and the anatomical characteristics of the ankle were analyzed in detail by autopsy.The maximum width of the anterior posterior diameter of the medial malleolus,the distance from the midpoint of the maximum width of the anterior posterior diameter of the medial malleolus to the tip of the medial malleolus,the distance from the tip of the medial malleolus to the posterior tibial tendon,the distance from the lowest point of osteotomy to the posterior tibial tendon,the width of 1 cm above the ankle point,the overall width of the horizontal ankle joint were measured and recorded Distance from ankle point to tibial metaphysis,anterior posterior diameter of distal tibial articular surface,distance from tibial side to fibular side of distal tibial articular surface（width of ankle point）.Based on the data,a new medial malleolus osteotomy was designed and compared with the traditional chevron medial malleolus osteotomy（v-medial malleolus osteotomy）.The specimens were subjected to a new medial malleolus osteotomy and a traditional V-shaped medial malleolus osteotomy.The surgical design of the new medial malleolus osteotomy is briefly described as follows.After cutting the joint capsule and exposing the medial malleolus,first drill a hole from the front and rear sides of the medial malleolus with a 2.0 mm drill bit at about 0.6-1.2 cm above the distal front edge of the tibia,and then drill a hole from the inside to the outside of the bone,and then bend the ankle metatarsus,Using a 10 mm wide micro sagittal saw blade,the first osteotomy was performed about 1.5-2.0 cm above the leading edge of the distal tibia on the transverse plane of the ankle.The depth of this incision reaches two-thirds of the anterior sagittal plane of the medial malleolus and one-third of the medial coronal plane.The second osteotomy was performed on the medial tibial in the sagittal plane,about 1.5-2.0 cm away from the outside,and the depth reached the anterior third of the medial malleolus in the sagittal plane.The third osteotomy was performed on the coronal plane and connected with the above two incisions.Then turn the medial malleolus of osteotomy to the metatarsal side onto the triangular ligament,expose the inner side of talus formix,and perform relevant talus operations.Finally,the medial malleolus osteotomy block was restored and fixed by pre drilling with two 3.5-4.0mm cancellous lag screws.Suture the skin.The traditional chevron medial malleolus osteotomy is based on the methods described in the literature and will not be repeated.After completing the design of the new osteotomy from the autopsy level,in order to further compare the new osteotomy with the traditional medial malleolus osteotomy,the three-dimensional finite element method was used to reconstruct the bone around the ankle to generate a 3D model,the osteotomy areas of the two osteotomy methods were compared,and the four internal fixation methods were analyzed from the aspects of stress distribution and osteotomy surface displacement,The traditional medial malleolus osteotomy combined with double screws are fixed in parallel from the inside down to the outside up,the new medial malleolus osteotomy combined with double screws are fixed vertically and cross,the double screws are fixed in parallel from the inside out,and the double screws are fixed in parallel from the front to the back.The best internal fixation method is selected.Finally,the new medial malleolus osteotomy was applied to clinical practice,approved by the ethics committee,and obtained the informed consent of each enrolled patient.A total of 18 patients（19 ankles）received autologous periosteal iliac bone graft or osteochondral graft for OLT through new medial malleolus osteotomy.The time from the beginning of incision to the completion of osteotomy was recorded,that is,the operation time.All patients underwent clinical and imaging evaluation before operation as part of follow-up.Visual analog scale（VAS）and American Orthopaedic Foot and Ankle Society ankle hindfoot scale（aofas-ah）were used after operation.During preoperative examination,MRI was performed to measure the size and location of the lesions.The OLT size was measured by the formula:defect area=ab π/4=length of coronal plane × Sagittal length × 0.79（calculated from the maximum coronal and sagittal length on MRI）,measured using an image processing system.The location and size of the defect were reconfirmed during the operation.X-ray examination and X-ray measurement were performed at 6,8 and 12 weeks after operation and at the final follow-up.The displacement was accurately measured on the postoperative X-ray film of the final follow-up by PACS.When the postoperative X-ray film showed osteotomy cortical bone healing,it was determined that the healing was complete.The operation was performed under nerve block anesthesia or combined spinal epidural anesthesia.Patients were allowed to start passive activities two weeks after operation.Patients were encouraged to perform active range of motion and carry out partial weight-bearing under the ankle brace six weeks after operation.After clinical and imaging confirmed that the osteotomy site healed,unprotected weight-bearing was finally allowed.Continuous variables are expressed as mean ± standard deviation.Paired t-test or Fisher exact test were used for data analysis.P<0.05 was statistically significant.SPSS version 21.0 was used for statistical analysis.ResultsAfter measurement,we obtained that the distance between the anterior and posterior diameter of the maximum width of the medial malleolus is 38mm,the distance between the midpoint of the anterior and posterior diameter of the medial malleolus and the tip of the medial malleolus is 25mm,and the shortest distance between the tip of the medial malleolus and the posterior tibial tendon is 6mm.The maximum width of ankle point is 32mm.The width of 1cm-4cm on ankle acupoint is 46mm,44mm,40mm and 35mm respectively.At the maximum plantar flexion of the ankle,the talus can be exposed for 20 mm at most,and only the talus injury in zone 1 can be exposed.The distance between ankle point and metaphysis is 27mm.When the ankle joint is in the maximum plantar flexion position and the new medial malleolus osteotomy reaches 1/2 of the front of the medial malleolus,the talar cartilage injury in zone 4 can be fully exposed,and the shortest distance from the lowest point to the posterior tibial tendon is 6mm.The minimum distance between the fibular edge of the distal articular surface of the tibia and the axis of the tibia is 10mm.In other words,the distal tibial articular surface needs osteotomy of about 6mm from the tibial side to the fibular side,which is enough to expose the talar cartilage injury in zone 4.The new medial malleolus osteotomy is performed on the articular surface of the distal tibia.The distance between the front edge of the tibia and the axis point of the tibia is 4mm,that is,the distance between the anterior and posterior osteotomy of the articular surface of the distal tibia is 10mm.The osteotomy area of distal tibial articular surface is about 10mm × 6mm=60 mm2。Relatively speaking,the osteotomy point of traditional osteotomy is just at the posterior tibial tendon,which is easy to damage the posterior tibial tendon during operation.The distance between the projection point of the tibial axis and the anterior and posterior edges of the tibia is 14mm and 14mm respectively,and the distance between the projection point of the tibial axis and the medial and lateral malleolus is 16mm and 16mm respectively.V-shaped medial malleolus osteotomy,the osteotomy apex is 25mm above the ankle acupoint,the downward opening is about 45°,the bone block is turned down together with the triangular ligament,and the ankle joint is turned out at the same time,which can fully expose the talus cartilage injury in zone 4.The distal tibial articular surface needs osteotomy of about 16mm from tibia to fibula.V-shaped medial malleolus osteotomy was performed on the articular surface of the distal tibia.The distance between the anterior tibia and the posterior tibia was 28 mm.Of course,in the actual clinical operation,the range of medial malleolus osteotomy may be smaller than that of autopsy osteotomy,because ankle valgus is seriously limited in cadaver specimens.In clinical practice,ankle valgus has a range of activity.With regard to the comparison of osteotomy area,considering the differences between clinical practice and autopsy,the finite element analysis was also carried out in this study.The results show that when maintaining the neutral position of the ankle,if the lesions in area 4 of the superior talus articular surface are to be exposed,the new medial malleolus osteotomy scheme needs to carry out the first 2/3 rectangular osteotomy to form a rectangular osteotomy surface on the inferior tibial articular surface,In the traditional medial malleolus osteotomy,the anterior inferior and posterior inferior of the medial malleolus are the two vertices for osteotomy.The bone block is similar to a triangular pyramid,forming a triangular osteotomy surface on the distal articular surface of the tibia,and the osteotomy area on the articular surface is greater than the former.In addition,as a rectangular osteotomy,the new medial malleolus osteotomy scheme can also be combined with ankle plantar flexion to reduce the amount of osteotomy.Similarly,it can expose the lesions in zone 4 of the upper articular surface of the talus.In the state of plantar flexion of the ankle,the new osteotomy scheme only needs to carry out the rectangular osteotomy in the front 1/3 of the medial malleolus.It forms a rectangular osteotomy surface on the distal articular surface of the tibia,which is smaller than the traditional medial malleolus osteotomy.In addition,four internal fixation methods are simulated respectively,that is,the traditional medial malleolus osteotomy double screw is fixed in parallel from inside down to outside,the new medial malleolus osteotomy double screw vertical cross approach,the new medial malleolus osteotomy double screw is parallel from inside to outside,and the new medial malleolus osteotomy double screw is parallel from front to back.The calculated peak stresses are 6.952 MPa,6.834mpa,6.944 MPa and 7.133mpa respectively,and the calculated osteotomy surface displacements are 0.221926mm and 0.192431 mm,0.259525 mm and 0.399691 mm.Finally,according to autopsy and finite element analysis,a new osteotomy method of medial malleolus and a vertical cross internal fixation method of double screws were determined.In clinical practice,the data showed that all patients were followed up for more than 24 months,and the articular surface of tibial could be seen in all cases.There were 4 patients with proximal and medial displacement,the proximal was 1.0 ± 0.1 mm and the medial was 0.3±0.1 mm.By 6 weeks after operation,47.3%of patients healed from the clinical and imaging manifestations.After 12 weeks,all patients healed.The average healing time of two screws fixation was 7.4±1.7 weeks.The mean preoperative VAS score was 6.4±1.0 and the mean AOFAS score was 54.2±12.1.At the last follow-up,the mean scores of vas and AOFAS were significantly improved,which were 1.8±1.3 and 84.6±6.6,respectively（P<0.001）.All patients recovered at least leisure sports or moderate heavy physical labor.No patients had internal fixation problems.No tendon injury was found during the operation,and no complications such as ankle stiffness and postoperative infection were found after the operation.ConclusionThe new medial malleolus osteotomy has less trauma,no damage to the central point of the distal tibial joint surface,and the osteotomy area is smaller than that of the traditional osteotomy.Finite element analysis shows that when the new medial malleolus osteotomy and double screw vertical cross fixation,the stress distribution is more uniform,the stress peak is lower,the displacement under load is smaller,and the displacement of osteotomy surface is the lowest.Clinical practice has proved that the new medial malleolus osteotomy can expose most of the OLT in the medial talus and provide enough space for osteochondral transplantation or periosteal iliac bone graft.In addition,the anatomical structure behind the medial malleolus does not need to be deliberately protected,which can shorten the osteotomy time.The results show that the operation provides good internal stability and promotes the early recovery of patients. |
