Biomechanical Study Of Lateral Ligaments Of Ankle Joint Holding Ankle Stable

Objective: To measure stability of ankle joint by selective cuttinglateral ligaments of ankle joint, invest the contribution of each ligament inankle stability, to provide fundamentally theoretical criteria for clinicaldiagnose and treatment.Materials and Methods: 18 cases fresh adult ankle joints was taken inlateral ligaments anatomy which include anterior talofibular ligament(ATFL), calcaneofibular ligament(CFL), and posterior talofibularligament(PTFL). These specimens were divided into 3 groups randomly,each group had 6 cases. The ATFL, CFL, and PTFL were cut in turn in group1. The CFL, PTFL and ATFL were cut in turn in group 2. The PTFL,ATFL,and CFL were cut in turn in group 3. We would get 8 kinds of model,①18cases ligaments were intact,②6 cases ATFL was cut,③6 cases CFL wascut,④6 cases PTFL was cut,⑤6 cases ATFL and CFL were cut,⑥6 casesCFL and PTFL were cut,⑦6 cases PTFL and ATFL were cut,⑧18 casesATFL, CFL and PTFL were cut. The anterior drawer test were done on allthe specimens with several different stress. We took lateral-media ankle X-ray and measured anterior talar translation(ATT). Ankle joints were putvarus with several different stress on lateral ankle, anterior-posterior ankleX-ray was taken, talar tilt(TT) was measured. SPSS 13.0 was used toanalyzed ATT and TT.Results: All the specimens were done anterior drawer test, whenwithout stress, 50 N and 100 N stress exerted from anterior to posterior, ATTincreases with the stress raising, when stress added to 150 N and 200 N, ATTstop increasing. ATT was 9.3 mm when ATFL was cut with 100 N stressexerted, the ankle joint was unstable. When the CFL was cut or PTFL wascut alone, the CFL and PTFL were cut together, ATT does not increaseobviously. There was no statistical significance in ATT between the groupwith ATFL cut alone and the group with ATFL and PTFL cut. ATT was 11.3mm when ATFL and CFL were cut, and ATT was 13.3 mm when all thelateral ligaments were cut. All the specimens were exerted stress on thelateral of ankle joints so as to let ankle joint be varus. When without stress,50 N and 100 N stress exerted, TT increased with the stress raising, whenstress added to 150 N and 200 N, TT stop increasing. TT was 6.1°when CFLwas cut with 100 N stress exerted, there was statistical significance compareto the group which the ligaments were intact, but the ankle joint was notunstable. When ATFL and CFL were both cut, TT was 10°, the ankle jointwas unstable. TT was 16.6°when all the lateral ligaments were cut. WhenATFL or PTFL was cut, the ankle joints were stable. When ATFL and PTFLwere cut or CFL and PTFL were cut, the ankle joints were stable too.Conclusions: ATFL can restrict talus translate forward. Talus willtranslate forward and ankle joint was unstable when ATFL was cut no matter CFL was intact or not. Talus would be varus when CFL was cut, but anklejoint was not unstable on the lateral, when ATFL was injured simultaneously,the ankle joint would be unstable. Therefore we can tell ATFL was the maintissue to restrict talus move forward, and it was important to restrict talusadduct especially when CFL was cut. ATFL would be injured firstly when theankle joint was injured with the position of plantar flexion and inversion, theankle joint would be unstable on the anterior-posterior and lateral directionwhen CFL was injured too. ATFL and CFL were the main structure tomaintain the lateral ankle joint stable. PTFL was not important in maintainthe lateral ankle joint stable, it constrain talus varus when ATFL and CFLwere injured.