The Biomechanics Research Of Flap Of A Big Toe With Phalanx Ungual For Thumb Ⅱ° Defect Reconstruction

Objective:The thumb II°defect will lose 50% functionof one thumb and 25% function of one side hand,which gravelyaffects hand function.With the development of microsurgerytechnology,the method of thumb reconstruction is gradually rich various,and among them,the flap of a big toe is to be the most broad. Similar skin texture and the framework oforganization with regular thumb, not cuting down the toe number,not affectting the function of pelma bearing a heavyburden,especially the beautiful appearance is that the other repairing method does not have. The articular surface of paratelum phalanx bottom is magnanimoust,forming expandingbone ridge,not physiologyical matching with the thumb proximal phalanx .Operation persons often wipe out the ar-ticular surface according to experiences,but the range doesnot have a standard to be consulted. It is easy to send outwound arthritis then,which gravely affects the arthrosis activityand the function of the rebuilding thumb. For this reason,ourtopic will construct the thumb model defected according to II°,studying the biomechanics differentchanges between thearticular surface of a thumb proximalphalanx and a paratelumphalanx and providing the theory basis and the best operation scheme for thumb reconstruction.Methods: Select and use 20 fresh cadaveric specimens,40examples in total,differently reserved from metacarpophalangeal joints and distal interphalangeal joints of the homonymy toes, holding the two sides articular capsule absolutely.Cut off the ulnaris articular capsule of the thumb and insertthe pressuresensitive film.The specimen is placed in CSS 44020 series biomechanics testing machine,speeded with 5N/s,gradually loaded at 100N, the force condition maintaininghalfminutes,and measure mechanics changes of the articular surfacewith the interphalangeal joint buckling 0°, 45°, 90°.The 40 specimens random are divided into five groups,each groupincluding 8 specimens,marking with A, B, C, D, E group,respectively cutting off 1/10,1/9,1/8,1/7,1/6 of the articular surface of the toe phalanx bottom. Messure themec-hanics changes of the articular surface with thesame methodand then deal with the data by statistics method.40 volunteers,80 examples in total,were examined by ultrasonograph Philips IE33 (the company of Holland Philips)with the detector frequency being 1.7-3.4MHz. The thumb orthe toe is held out straight naturally, the detector placed ondistal phalanx or phalanx ungual.The detector were spreadedwith the lotus root mixture,using water bag.With upper ins-trument electron scale,measuring the bone horizontal stroke footpath.Result: 1 The contact area and pressure of interphalangeal joint:we find that by the analysis to pressure-sensitive film,inW,A,B,C,D group,the value did not displayed a stati-stical difference(p>0.05);the contact area in every zonation tendedto have a redistribute.The condyle zonation and the area between condyles tended to decrease,the other area increased.They had shown a statistical difference(p<0.05).InE group,the total contact area and each zonation all increased,showing a significant statistical difference (p<0.05 or p<0.01).2 The change of the contact pressure in the interphala-ngeal joint:through the measurement of the pressure,comparingwith the intact specimen,we found that in W,A,B,C,Dgroup,the mean pressure and the peak pressure of each zo-nation did not display a significant change.But in Egroup,themean pressure and the peak pressure of each zonation increasedand showed a significant statistical difference (p<0.05).Conclusion: 1 When we use flap of a big toe with phal-anx ungula toreconstruct thumb.The articular surface of para-telum phalanxbottom is not physiological matching with thethumb proximalphalanx,which can gravely affect the rebuilding thumb appearance,so we should cut off parties of the articularsurface.2 When 1/6 of the articular surface of paratelum phalanxbottom was cttted off on both side of the phalanx, the mec-hanics index changed obviously.The contact area in each zo-nation decreased and the mean pressure and the peak pressureincreased significantly,which can lead to traumatic arthritis of the joint.