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.

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

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 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.

Aim: To study the effect of pulsed electromagnetic fields(PEMF) stimulation on the repair of rats grafted sciatic nerve. Methods: One hundred Wistar rats were classified randomly into two groups, a control group (group A, n = 50) and a PEMF group(group B, n = 50). The biological effect of the grafted nerve, the relative lumbar spinal cord and one of the ending organs - triceps muscle was studied at the same time. Results: The neuron's vitality in lumber spinal cord had been stimulated in the PEMF- treated rats. The Wallerian degeneration of the nerve distal to the grafted was accelerated after PEMF stimulation. The increased regeneration of the nerve was found throughout 16 weeks recovery period in PEMF group. Application of PEMF had decreased the atrophy of the triceps muscle caused by denervation and promoted its functional recovery. Conclusion: PEMF stimula- tion may enhance the regeneration of the injured peripheral nerve.

Objective To study the feasibility of polylactic acid(PLA) as carrier of bone morphogenetic protein(BMP), and observe its results of inducing osteogenesis. Methods A 12 mm bone defect experimental model in the left ulna of rabbits was made, the animals were divided into three groups at random, bovine BMP 10 mg with PLA carrier was implanted into the defect area in the experimental group, bovine BMP 10 mg with bovine cancellous bone matrix carrier was implanted in the control group, and nothing was implanted in the blank group. The osteogenesis of the bone in the defect area was observed by regular roentgenography, the histological changes of the bone defect tissue in 4th, 8th, 12th week after operation were studied and the new bone formation was measured by image analysis. Results The results revealed that the bone defect in the experimental group had excellent repair than that seen in the control and blank group, both bone union and the period of bone mature were earlier than that seen in the control and blank groups. There was fibration in the blank group at 12th week. Conclusion The result indicated that PLA is a material able to be used as a carrier of BMP in inducing osteogenesis, it has a better effect of inducing osteogenesis than xenogenous cancellous bone matrix. Compared with other carriers, PLA has the following advantages: 1)It releases BMP gradually during degradation, so the BMP concentration in bone defect can be maintained effectively. 2)It is a material with some rigidity, so is able to exert flexible fixation of the fractures. 3)It can be shaped to adjust itself for the individual fractures. 4)It has a good histocompatibility and an adjustable property. However, the relationship between the molecule weight, aperture of PLA and the best inducing osteogenesis need a further study.

Objective To investigate the expression of nerve tissue protein S-100(S-100)and gap junctional protein connexin 43(Cx43) in rat adenohypophyseal folliculo stellate cells(FSCs) under the influence of ovariectomized osteoporosis(OVX-OP) and estrogen replacement therapy(ERT). Methods Sixty 10 month old female rats were randomly divided into sham operation control group(Sham), ovariectomy group (OVX) and ovariectomy+ERT group (OVX+ERT). L4-6 bone mineral density(BMD) of the animals in Sham group and OVX group were measured by dual energy X-ray absorptiometry(DEXA) at the end of 6 weeks after operation. From 7th week, rats in OVX+ERT group were treated with nilestriol(1 mg?kg -1?week-1) for 6 weeks. Rat L4-6 BMD in OVX+ERT group were measured at the end of 12 weeks after operation. Expression of S-100 and Cx43 in FSCs was detected using immunofluorescent histochemistry and laser scanning confocal microscopy(LSCM). Results L4-6 BMD was significantly lower in OVX group (0.193?0.006) g/cm2 than in Sham group(0.211?0.013) g/cm2 and in OVX+ERT group (0.204?0.010) g/cm2 (P

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.[