| Objective: The complex of capsule-collateral ligament is the most importantstatic structure that maintains the lateral stability of MCPJ. There are 4 modesof complex including normal, radial rupture, radial repair and fixed withexternal fixator. Based on lateral stress test and longitudinal stretch test, werecord biomechanical special parameters such as rupture position, maximalload of rupture & rupture displacement, lateral laxity angulation of stabilityto offer theoretical evidence for reparation of complex and the use of externalfixator clinically.Methods and Material: Maked the 48 2nd MCPJ of fresh cadaver tospecimen with gradual dissection. The specimens were distributed randomlyto two groups- A and B. Under 4 conditions of the complex which includenormal, radial rupture, radial repair and fixed with external fixator, there waslongitudinal stretch test on group A and lateral stress test on group B.Mini-apparatus was done by rnyself and specimen was mounted on it withextension in 0 degree. Record rupture position, maximal load of rupture &rupture displacement under 4 conditions on Group A. Record lateral laxityangulation and maximal stress-load of MCPJ under 4 conditions on Group B.All data were analyzed with statistical software(SPSS13.0) and one-wayanalysis of variance was performed to compare the stability of MCPJ under 4 conditions of two groups.Results: Group A- longitudinal stretch test: Average stretch displacement ofnormal capsule-collateral ligament was 4.82mm and maximal stretch load ofit was 868.35 Newtons. Rupture position of collateral ligament: 1 was inorigin, 1 was in insertion and 4 was in intermedial. Average stretchdisplacement of capsule- collateral ligament after radial rupture was up to6.27mm and its maximal stretch load was obviously decreased to 719.80Newtons. As radial rupture its stability was decreased outstandinglycompared with normal. Average stretch displacement of radial repair was4.98mm and decreased compared with normal conditions. Also its maximalstretch load was average 808.51 Newtons. Compared with normal condition,stability of radial reparation condition was not decreased. Compared withradial rupture, its stability was increased outstandingly. Average stretchdisplacement of MCPJ fixed with external fixator after radial rupture andreparation was 3mm and average maximal stretch load was 1462.10 Newtons.There had a statistical variance and indicated that stability is increasingobviously after fixed with external fixator. Group B- lateral stress test: Whencapsule-collateral ligament was normal, average lateral laxity angulation ofMCPJ was 14.35 degree and maximal load was 124.20 Newtons. After radialrupture of MCPJ its lateral laxity angulation was increased to 23.34 degreeand its maximal load was 73.71 Newtons. Compared with normal condition,stability of MCPJ after radial rupture was diminished outstandingly. Laterallaxity angulation of MCPJ after reparation was 16.32 degree. As to thenormal condition, stability of MCPJ was as same as the normal condition; asto radial rupture condition, its stability was increased. Lateral laxityangulation of MCPJ fixed with external fixator after radial rupture and reparation was 5.00 degree and maximal load was increased to 567.67Newtons. There was a outstanding statistical variance and had a increasingstability after using external fixator.Conclusions: The complex of capsule-collateral ligament is the mostimportant structure that maintains the lateral stability of MCPJ. Oflongitudinal stretch test average maximal stretch displacement of normalMCPJ was 4.82mm. After destroying average maximal stretch displacementwas up to 6.27mm; maximal load was 719.80 Newtons. It manifested that theanti-stretch character was decreased obviously. After reparation maximalstretch displacement was 4.98mm, stability and anti-stretch character wereincreased. The stability of MCPJ fixed by external fixator was excellent,which does good to reparation of injuries and functional rehabilitation. Of thelateral stress test, average lateral laxity angulation of normalcapsule-collateral ligament was 14.35 degrees and maximal load was 124.20Newtons. Then the MCPJ was stable. Lateral laxity angulation of MCPJ afterradial rupture turned bigger and the MCPJ instability. Lateral laxityangulation of MCPJ after reparation was increased to 16.32 degrees thatindicated reparation improved the stability of MCPJ. The stability of MCPJfixed with external fixator after reparation has a recovery. Therefore,clinically we use the external fixator to brace and lock reasonablely based onmaximal stretch displacement and the fixation principle of fixator preventingarthrogryposis and reinjury of ligament. Also lateral stress test give us areference for clinical diagnosis and surgical reparation of capsule-collateralligament injury.
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