When an extremity is being lengthened, the principle of the elasticity limitation of living tissues is always considered to be a guide fo avoid injuries to the nerves, blood vessels and periostium. It is generally believed that the lengthening should not exceed 10~15% of the original length of the bone. In order to attain a safe and large scale lengthening of a limb, the authors, under the condition of secure fixation of bone ends and early functional excercise of the diseased limb by using a specially des-gned external fixator, adopted a gradual lengthening with a slow speed of 1~1.25mm/d.Eighty cases of epiphysial distraction and 63 cases of metaphyseal osteotomy to lengthen extremities were studied. It was found that the expected lengthening in all the cases was achieved with a lengthening rate of 9~84.3% of the original length. It was 30~84.3% in 16 cases. The absolute lengthening was 6~16 cm in 69 cases. In one case, the femur and tibia were elongated at the same time, and a large shortening of 22 cm of the right lower limb was corrected in a one-stage operation (131 days).Experiments were performed on 15 goats. The lengthening rate of the tibia was 28.6~64.8% of the original length, with an average of 50.2%. In both the clinical and experimental studies, no nerve or blood vessel injury or non-union of the bone was found.The authors proposed a new concept different from the principle of elasticity limitation of livingissues. It is believed that nerves, blood vessels and periostium possess good adaptation capacity to slowand gradual lengthening. Low tension from traction can stimulate the tissues of the extremity to grow synchronously with the slow gradual lengthening and no injury will be inflicted to the structures and functions of the tissues concerned.

Sixty cases of different types of patellar fractures were treated from December 1986 to October 1990 by a self-designed miniature external fixator. The patients were followed-up for 6 months to 4 years, and there was not a single case of infection, prepatellar bursitis or early degeneration of the knee joint. The structure of the fixator is simple and the operation is easy. It is a versatile tool, because it can be used either for extension or for compression.since the pins are inserted without operation, it gives rise to little pain. Under the present treatment bone healing is rapid and the function of the knee joint is well preserved. The rate of excellent result reaches 98.2 per cent

Objective To evaluate the effect of limb lengthening on the perineurial barrier and vascular permeability of peripheral nerve. Methods Thirty-two rabbits with limb lengthening of 10％ , 20％ , 30％ and 40％ were used in this study; 8 animals were allocated in each group. Sixteen were employed for the electron microscopic(EM) observation and the others for the investigation of perineurial barrier and vascular permeability of the tibial nerves. Results Even if the elongation reached 40％ of the original length of the tibia, both the perineurium and inner membrane of capillary was still intact, the perineurial barrier and vascular permeability maintained normal; however, EM examination revealed increase of a large number of vacuoles and the increase of the number of mitochondria in the cell of the perineurial membrane. Conclusion It is the gradual limb lengthing of

Objective:To study the effects of unilateral posterior crossbite on masticatory muscle functions pattern by using electromyography(EMG).Methods:20 subjects(11 males and 9 females)with unilateral posterior crossbite were selected.Subjects were instructed to stay mandibular postural position and to make maximum bite in intercuspal position(ICP)and bilateral chewing.EMG data of the left and right masseter and anterior temporalis muscles were recorded.Asymmetry index of masseter muscles(ASMM) and asymmetry index of temporalis muscles(ASTA)were calculated and compared.20 subjects with individual normal occlusion were used as control.Results:Compared to control group,masseter and temporal muscle activities in unilateral posterior crossbite group were lower in maximum bite and bilateral chewing;The activities of two muscles at crossbite side were lower than that at noncrossbite side.Under maximum bite and bilateral chewing,ASMM and ASTA in unilateral posterior crossbite group were significantly higher than those in control group;ASMM and ASTA in Subjects with one posterior tooth crossbite is lower than subjects with several teeth crossbite.Conclusion:It can be suggested that unilateral posterior crossbite may damage the function of mastication muscle.

Aim To test the strength of Kraekow bilateral locking stitchfor tendon or ligament free end fixation and evaluate the stitch which wasused in reconstruction of cruciate ligament or secure fixation of soft tissue tobone. Methods Twenty-four specimens of patellar tendon free end, whichwere divided into 3 groups according 2 or 3 stitches and 6 subgroups ac-cording No1 Ethilon or 0.4 mm diameter stainless steel wire different suturematerials, fixed with Krackow locking stitch, were undertaken the tensiletest respectively, so as to find out the least stitches and efficient suture pat-tern. Results 2 Krackow locking stitches had more strength than that of0.4 mm diameter stainless steel wire, the fixation strength of 2 stitcheswhich used No1 Ethilon was more than 80 N, superior to the failure strengthof material itself, it still maintained the same strength if the first stitch wasacross the tendon tissuetransversely. There was no significant differencebetween 2 and 3 Krackow locking stitches in suture strength statistically, thefixation strength was superior to the suture material, it could reduce the'suture exposure when the first stitch is across the tendon tissue while main-tains a comparable strength to other suture. Conclusion If attempt to makea higher strength of suture, we should focus on selecting a stronger materialsor adding the suture materials in number rather than the stitch number.

To study the expression of bone morphogetic protein(BMP) and transforming growth factor β１（TGF-β１) in regenerative gap during lengthening period. Method: The right tibia of 14 mature rabbits were lengthened using metaphyseal osteotomy. Distraction was started on the 4th day postoperatively, 1mm per day and conducted twice each day. The expression of endogenesis BMP and TGF-β１ in regeneraive gap were observed during ten weeks after distraction by histology and immunohistochemisty. Results: The result showed that bone morphogetic protein(BMP) and transfoming growth factor β１(TGF-β１) were expressed in chondrocytes, osteoblasts, and fibroblasts. The expression of BMP was at a high level in initial two weeks after distraction while the expression of TGF-β１ was increased step by step. Then both of them decreased alonged with lengthening proceeding. Two weeks after distracting stopped, the expression of BMP could not being observed. But the expression of TGF-β１ could being observed all stage after distraction stopped. Conclusion: BMP and TGF-β１ were expressed persistently in regenerative gap during bone lengthening.

Objective To investigate the adaptation of metabolism of arthrodial cartilage for limb lengthening. Methods Thirty New Zealand rabbits were randomized into two groups, limb lengthening group (group A) and delay observation group (group B). Every group was subdivided into three sub-groups according to distraction degree: 10%, 20% and 40%. Upper-tibia metaphysis lengthening was adopted at 1 mm/d rate of distraction and iconography changes of knee joint were observed with X-ray, the morphologic changes of chondrocyte and cartilago articularis on tibial flat were observed with light and electric microscope. The changes of cartilage surface were observed with scanning microscope. Results 1) There was no obvious iconography change of knee at every time phase in each group. 2) Pale of cartilage on tibial flat were just noted in group A40 and B40. 3) The arrangement of chondrocyte was disorder in A40, some degenerating and generating chondrocytes were found in the same group. The number of chondrocytes increased, and the volume was expanded in group B20 or B40, the degenerating chondrocytes were not found in the same group. 4) Low-grade expansion of endoplasmic reticulum and swelling of chondrosome were found in part of chondrocyte in group B40 contrasting with the other groups. The numbers of endoplasmic reticulum and matrix alveolus increased in chondrocyte. The same changes were observed in group A. 5)The cartilage surface lost its smoothness during distraction, and this kind of changes were more severe when distraction increased. Conclusion The articular cartilage showed certain adaption to stimulation of distraction during low degree distractions. To greater distraction degrees some abnormality in metabolism of arthrodial cartilage may occure.

Objective To establish the technique of biphasic seeding of articular chondrocyte s in vitro for cartilage engineering in u sing a self designed biological gel a nd the three-dimensional scaffold a nd observe the efficiency of cartilage regeneration in vitro-tissue engin eered articular cartilage from cell scaffold complex.Methods The articular chondrocytes were iso lated enzymatically from the epiphyseal cartilage of young rabbits,and were then plated i nto the tissue culture flasks and were cultivated.The first passage ar-ticular chondrocytes were collecte d and mixed fully with the self-made l iquid biological gel-matrix at appr oxi-mately 2.5?10 7 cells /ml to form cell-gel fluid.The cell-gel fluid was dropped into the p orous CPPf /PLLA(calcium polyphosphate fiber /poly -L -lactic acid)scaffold,and a cell-gel-scaffold c omplex was formed after being solidified.The complexes were cultivated for 4weeks.The changes of complexes in morphology and synthesis of collagen typeⅡandⅠand aggregates were investigated under the gross and the phase and light microscope.The GAG sulfate content in complexes was quantitatively mea sured by the modified dimethyl-methylene blue method.Results1)After feeded,the porous CPPf /PLLA s caffolds were completely filled with the liquid chondrocyte-gel and the chondrocyte-gel-scaffold comp lexes were well formed by solidification.During the cultivation,the complex es could keep its original shape and m aintain the stable homogeneous three-dimensional distribution of chondrocytes in themselves without cell falling.In the same time,the com-plexes were gradually increasing th e consistency with the elasticity an d lubrication surface.2)The chondro-genesis began in the periphery area a nd extended to the central area of the complexes with the passage of cultivation period.After the 2nd we ek,the complexes were gradually reorganized into the mature engineered cartilage with typical cartilaginous histological structure,with ric h typeⅡcollagen and the strong typical het-erochromia to toluidine blue,but wi th gradually fading negative immunological stain of collagen typeⅠ.Meantime,the scaffold was graduall y de-graded in the complexes.The average content of GAG sulfate in the enginee red cartilages at 4th week was(15.70?2.00)mg /g(wet weight ),and was over 30%of the natural articular cartila ge.Conclusion The technique of chondrocytes biphasic seeding for three-dimensional scaffold has advantages of simple manipulation,fix ing cell stably in the scaffold,main-taining the original shape of the com plexes and the stable homogeneous th ree-dimensional distribution of chondrocytes in the scaffold,and ad vancing the regeneration and matura tion of tissue-engineered articula r cartilage.[

Objective To establish the methods of efficiently isolating chondrocytes from epiphyseal cartilage and observe the basic biological characteristics of the cultured ones. Methods The improved isolation method through three-step enzymatic digestion using 1 g/L trypsase in 1 g/L ethylenediaminetetraacetic acid, 1 g/L hyaluronidase and 2 g/L type Ⅰ collagenase was established to isolate the primary passage chondrocytes from epiphyseal cartilage of young rabbits and its efficiency evaluated. The cellular biological characteristics of the chondrocytes were observed under the inverted and light microscopes. Results (1) All chondrocytes were isolated from the matrix after it was completely digested by three above-mentioned enzymes. The harvested chondrocytes significantly and positively correlated with the wet weight of cartilage. The number of chondrocytes from 1 g of wet cartilage was 32.3?106 with a viability of 97.6% on average. (2) The chondrocytes of the primary and the first passages showed triangle or multi-angle shapes (oval during growth and fusion) with the positive immunohistochemical stain of collagen type Ⅱ and the strong heterochromia to toluidine blue. The chondrocytes after the third passage became spindle-shaped with the negative stain of collagen type Ⅱ and the weak heterochromia to toluidine blue. Conclusions (1) The chondrocyte-isolating method through three-step enzymatic digestion has advantages of high efficiency in harvesting primary chondrocytes, high cellular viability and simple manipulation. (2) The chondrocytes differentiate and lose their special phenotypes gradually with passage.

In order to investingate the stability of the half-ring sulcated external fixator,it was used to fix the bone after artificial fracture of the tibia shaft and tibia lengthening with proximal metaphyseal osteotomy were performed on 20 and 22 goats respectively.After operation,the animals were allowed to roam about freely,walking or jumping.In the fracture group,radigraphy of the tibia shaft,strength determination of the limb,and histological study of the fractured site were performed at the end of the 6th week.And in the lengthening group,x-ray examination and histological study were done after the 10th week.All the findings indicate that the external fixator designed in our department is well qualified to meet the requirement for the fixation of fractrued bones and the lengthened bones as well.