Biomechanical Study Of Varus Ankle Joint Osteoarthritis

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Ankle joint pressure change in varus malalignment of the tibiaBackground: Varus malalignment of tibia could alter ankle biomechanics,might lead to degenerative changes of the ankle joint.However,previous studies failed to report the detailed changes of ankle biomechanics in varus malalignment of tibia.The aim of this biomechanical study was to evaluate ankle joint pressure change in response to the gradual progression of varus malalignment of tibia.Methods 8 fresh-frozen human cadaver legs were tested in this study.Varus malalignment of tibia and a total of 600 N compressive force was simulated using a custom made fixture.Intra-articular sensors(Teck Scan)were inserted in the ankle joint to collected ankle joint pressure data.The testing sequence was 0°,2°,4°,6°,8°,10°,12°,14°,16°,18°,and 20° of tibial varus.Results As the tibial varus progressed,the center of force(COF)shifted laterally both for medial and lateral aspect of the ankle joint.For medial aspect of ankle joint,the lateral shift reached its maximum at 6o [2.76(1.46)mm,p=0.001] and 8o [2.76(1.62)mm,p=0.002],while for lateral aspect of ankle joint,the lateral shift reached its maximum at 12o [2.11(1.19)mm,p=0.002],thereafter,the COF shifted medially as the tibial varus progressed.The lateral joint pressure ratio was 0.481(0.125)at 0o and 0.548(0.108)at 10o and 0.517(0.101)at 20o.Significant differences were found between 0o and 10o(p=0.002),10o and 20o(p=0.002)of tibial varus.Conclusions For mild tibial varus deformities,there was a lateral shift of COF and lateral stress concentration within the ankle joint,while as the deformity progressed,COF shifted medially and lateral stress concentration decreased.This may be a compensation for varus deformity of the tibia due to the dip of subtalar articulation.Part ? Effect of the structure of the posterolateral ankle ligament on the stability of the ankle jointBackground: We have already discovered 23 patients during the work of the outpatient department and operations whose unstable signs on the posterolateral ankle.The anterior drawer test demonstrated normal during the physical examinations while the spaces of the posterior tibiotalar joints increased in stress X-ray plain films.ATFL intact and posterolateral ligaments lax were found during operations too.It is important to make existence claims and illuminate the mechanism of posterolateral ankle instability.Methods: A finite element model of the ankle was established for simulating to cut off posterolateral ligaments in turn.Ankle movements with tibia rotation under load on five forefoot positions were simulated as well.Results: The difference values with tibia external rotation were negative,and the positive results occurred with tibia internal rotation.The tibia-talus difference values in some forefoot positions were 2 ~ 3 mm after PTFL together with CFL or/and PITFL were cut off.The tibula-talus difference values were 2.21 ~ 2.76 mm after both PTFL and CFL were cut off.The tibia-fibula difference values were small.The difference values increased by 2 ~ 5 mm after cutting off the PITFL.Conclusions: Posterolateral ankle ligaments,especially CFL and PITFL,play a significant role in maintaining ankle stability.The serious injuries of both CFL and PITFL would affect posterolateral ankle stabilities.PITFL was important to subtalar joint stability.Part ? 1.Imaging measurements under stress and functional assessment of patients with posterolateral ankle instabilityBackground: Chronic instability of ankle joint is an important cause of osteoarthritis of ankle joint.In clinical practice,we found that some patients with unstable ankle joints had negative or weakly positive preclinical physical examination of drawer test,but varus test under stress was significantly positive.The disease in this group of patients can be defined as chronic posterolateral ankle instability.At present,there is no clinical report on the effect of surgical treatment for such patients.This study will review the effect of anterolateral ankle ligament reconstruction in patients with this particular type of ankle instability.Methods: From January 2010 to December 2015,a total of 30 patients with chronic posterolateral ankle instability were collected,including 21 females and 9 males.The average age is 36(18-48 years)years old.All patients had a course of disease longer than 2 years and no significant relief of symptoms after conservative treatment for more than 6 months.All patients underwent posterolateral ankle ligament reconstruction.The score of American Orthopaedic Foot and Ankle Society Ankle and Hindfoot(AOFAS-AH)before and 12 months after surgery,and the values of anterior talus movement and varus under stress of ankle arthrography before and 12 months after surgery were recorded and compared.Results: All patients were followed up for more than 12 months.The average preoperative AOFAS-AH score of patients in this group was 65.4±6.3 points,and the average postoperative AOFAS-AH score was 93.5±5.6 points.The mean value of talus anterior displacement was 10.2±4.5mm before operation and 4.7±2.4mm after operation.The mean value of talus varus was 15.6°±4.1° before operation and 5.1°±2.5° after operation.Conclusions: The reconstruction of the posterolateral ankle ligament can effectively improve the ankle pain and other uncomfortable symptoms in patients with chronic posterolateral instability of the ankle joint,and is also an important means to prevent the occurrence of varus osteoarthritis of the ankle joint.Part ? 2.Periarticular osteotomy for the treatment of severe varus osteoarthritis of the ankle : medium to long term follow-upBackground: Whether periarticular osteotomy is appropriate for stage 3B osteoarthritis in Takakura ankle osteoarthritis classification remains to be determined.The purpose of this study was to evaluate the efficacy of periarticular osteotomy in the treatment of ankle osteoarthritis of Takakura 3B.Methods: From February 2008 to August 2013,we performed periarticular osteotomy of the ankle on 21 patients who met the inclusion criteria.The mean age of the patients at the time of surgery was 53.7±5.8 years(range 39 ~ 61 years).The mean follow-up time was 87.7±19.5 months(range 61 ~ 125 months).Imaging studies included the TAS Angle,TLS Angle,and TT Angle of the talus.Using the American Orthopaedic Foot and Ankle Society Ankle Hindfoot Scale(AOFAS-AH),Visual Analogue Scale(VAS),Short Form-36(SF-36),Ankle arthritis Scale(AOS)for functional evaluation.Results: All patients were followed up.TAS Angle was improved from 82.8±2.4 to 90.3±2.3.The TLS Angle changed from 77.5±2.8 to 79.4±2.7.The preoperative and postoperative TT angles were 13.4±3.6 and 4.8±3.6,respectively.In terms of functional evaluation,the preoperative VAS and AOFAS-AH scores were 5.7±1.3 and 48.0±15.8 respectively,and the postoperative VAS and AOFAS-AH scores were 2.5±1.9 and 74.8±11.5 respectively.The mean SF-36 scale increased from 41.2±13.1 to 66.7±14.9.AOS scores were improved from 61.4±12.5 to 27.5±17.8.One patient underwent total ankle arthroplasty 3 years after surgery.Four patients were still in stage 3B,including the one who underwent ankle arthroplasty.Four patients improved to stage 3A,11 patients improved to stage 2,and 2 patients improved to stage 1.Conclusions: Periarticular osteotomy combined with auxiliary surgery can restore the normal alignment of the ankle joint and change the abnormal stress distribution of the ankle joint,so as to improve the patient's function and the imaging stage.