| Objective: Volar capsular ligaments complex is an important stable structure of wrist joint. Whlie a person falling down, his wrist joint often extends, this leads to the fracture and dislocation of wrist or distal radius, which accompanies with the complex being injured. Arthralgia and functional impairment of the wrist joint emerge easily. In clinic, some surgeons only emphasize on the treatment of fracture or dislocation of the wrist, but often ignore reparation of the capsular ligaments complex. At present, the external fixator devices are applied widedly in clinic. To investigate the different circumstances of the complex(.normal, injured, repaired, repaired +the external fixation, injured+the external fixation) by loading the wrist on its dorsal, recording the load-translation curve dynamically. To compare the difference of the load variation. Through the test, maybe we can evaluate the effect of volar capsular ligaments complex for the stability of wrist, and provide basic biomechanical theoretical criteria for clinic application the external fixation.Methods and Material: Take 9 upper limbs specimen from fresh adult cadavers to make wrist joint-bone capsular ligaments complex specimen, by simulating to fix the external fixation at the shaft of second metacarpal bone and its basal body, in the Shaft of radius as well, 4 screwes are twisted respectively through the specimen. One Kirschner wire(3.0mm diameter) is used to penetrate the distal ends of the second～fifth metacarpal bones, the other one Kirschner wire is used to fix the shaft of radial bone and ulnar bone. The specimen is fixed between the apparatus exactly. To unify injured standard: cutting off volar capsular ligaments complex(including the radial ligament complex and ulnaris ligament complex) from the malleolus radialis to malleolus ulnaris. To unify repaired standard: suturing the injured complex with 4-~# suture silks. At the beginning of test, every specimen maintains neutral postion. According to normal condition, injured condition, repaired condition, repaired plus fixed device, injured plus fixed device in turn, between the tendinous sheath of extensor hallucis longus and lister tubercular, with the velocity 10mm/min the load is applied on the specimen. The translation changes from 0cm to 2.5cm during the test. The instrument (INSTRON maded in USA) records translations-load curve at the same time. In order to understand the importance of the volar capsular ligaments complex toward the stablility of wrist, conduct a analysis using statistics software SPSS13.0 to compare the difference of load on each group of wrist joints on the condition of the same changed translation(1.5cm, 2.0cm, 2.5cm).Results: When the translation to extending of wrist is respectively under 1.5cm, 2.0cm, 2.5cm, averaged load is 60.74±20.60 newton, 138.46±12.93 newton, 312.87±37.15 newton under the normal condition of the Volar capsular ligaments complex. For the injured complex group, respectively averaged load is 35.23±13.88 newton, 87.17±24.22 newton and 198.16±37.14 newton. For the repaired complex group, respectively averaged load is 44.36±20.79 newton, 97.524±23.29 newton and 225.66±30.96 newton; for the repaired condition plus fixed device group, the changing load is 168.40±29.2 newton, 288.99±54.29 newton, 543.15±74.33 newton; for the injured condition plus fixed device group, the load is 139.00±33.18newton, 257.97±55.74newton, 450.35±29.38 newton. Conduct statistical analysis analysis of variance and rank-sum test), there is no statistical difference between the injured group and the repaired (P＜0.05), but analyzing the other groups, the result is P＜0.05 among them.Conclusions: Volar capsular ligaments complex is an important anatomic structure for keeping the stability of wrist joint. The carpal instability is arising on the condition of the injured complex, but only repairing the injured complex can not restore stability of wrist joint The external fixation can effectively help to diminish relative translation of injured capsular ligaments complex, reduce the load of repaired complex and protect the complex accordingly. The device plays an important role for the stability of wrist joint.
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