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.

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.

Transverse fracture was inflicted to the tibia of goats and specially designed external fixator was used for fixation to observe the relationship of different intensity of compres-sive force with fracture-healing.It was found in vitro test that the external fixator possessed less effect of stress protection.X-ray examination revealed that the stronger the compressive force was applied,the later the external callus would appear and the less amount of external callus would form.In the 6th week after fracture,the fracture line became oblierated in cases with mild compression while a transparent line in the external callus could be seen on x-ray films in those cases with heavy compression.Though there was no significant difference of the parameters of torsionmetry among different groups,the strength of the healed fracture with mild compression was nearer to the strength of a normal bone than that with heavy compression.Histo-logical examination revealed that all the bone unions belonged to secondary bone healing and bone callus became less matured along with the increase of compressive force.

The histological and biomechanical aspects of the osteogenesis in metaphysioto-my lengthening of the tibia were observed in 45 immature rabbits,which were divided into 3 groups as follows:(1)Group A:After metaphysiotomy,the periosteum and endosteum of the transected boneends were well-preserved.(2)Group B:After metaphysiotomy,the periosteum about 0.7 cm in width on the 2 bone ends was circumcised.Then the 2 bone ends were aligned without disturbing the endosteum.(3)Group C:After metaphysiotomy,a part of the bone marrow and endosteum in the 2 bone ends wwere removed.Then the 2 bone edns were well aligned and the periosteum was sutured up.In all the experimental animals,the tibia was lengthened by 1mm/day.It was found that in Group A,the formation and remodelling of the new bone in the lengthened area occurred quite early after metaphysiotomy and the new bone was good in its biomechanical quality;in Group B,the formation of new bone was retarded and the biomechanical quality of the new bone was not satisfactory;and in Group C,new bone formation was sluggish in the early stage after metaphysiotomy but it wwas active in the late stage,and the neww bone formed was similar to that of Group A in its histological morphology and biomechanical quality.The periosteum could grow synchronously with the slow traction without any tearing.In addition,osteotomy and mechanical traction could stimulate and accelerate periosteal osteogenesis.It is believed that an intact periosteal cuff is of significance in the osteogenesis of the lengthened area since it serves as a restriction framework for the adherent growing of the connection between the new bones of the 2 bone ends and periosteal osteogenesis plays a more important role than endosteal osteogenesis in the bony healing of the lengthened area.

Objective To compare the effects of point contact-dynamic compression plates (PC-DCP) and dynamic compression plates (DCP) on bone structure and mechanical properties of the plated bone in the intact goat tibia model. Methods Ten matured goats were used. The bilateral intact tibia of goats were fixed with DCP and PC-DCP respectively. The goats were sacrificed at 12 and 24 weeks after operation, and the tibiae were harvested. The structure of bone under plate was studied both by CT scan and histomorphology. The mechanical properties of the plated bone were examined by torsional test. Results At 12 weeks after internal fixation, there was obvious osteoporosis in the cortical bone underneath the plate in the DCP group compared with that of the PC-DCP group. Both of the cortical bone thickness underneath the plate and the torsion strength of the plated tibiae were significantly higher in the PC-DCP group than that in DCP group (P0.05). Conclusion The underlying bone resorption after rigid plate fixation is induced by both the disturbance of the bone blood supply and stress shielding. However, the former is the main cause in the early stage of fixation. PC-DCP is able to prevent bone resorption in the early stage of fixation.

Objective To evaluate clinical results of arthroplasty with the UNIVERS 3-D prosthesis in unstable shoulder arthritis. Methods 16 cases, which were 10 males and 6 females aging from 35 to 79 years (mean, 56.3 years), underwent shoulder arthroplasty with the UNIVERS 3-D prosthesis because of unstable arthritis. The patients were evaluated before surgery, at 12 months and the most recent follow-up with an average follow-up of 30.8 months(mean, 12-50 months) by Constant and normalised Constant score, and reviewed by the radiological analysis on preoperative and postoperative X-rays including AP, scapular and axillary views. Constant and normalised Constant score improvements at 12 months and the most recent follow-up evaluation were compared with the preoperative scores using paired-samples t test. Results 1) 8 out of 11(72.7%) cases with mild inferior humeral or glenoid exostosis. 2) The Constant score improved from 43.8?13(normalized Constant score, 51.36%?15.40% ) to 70.6?17.69(normalized Constant score, 86.44%?22.12%). The pain, activity, mobility and strength scores had been improved obviously. 3)Only one case had the radiolucent line around the uncemented humeral component with radiolucent index of less than 1. No any periglenoid component radiolucency, no shift or subsidence in humeral component, no migration and tilt in glenoid component, no change and loosening in the junction bolt between humeral stem and head. 4) Two cases were experienced postoperative complications including impingement of prosthesis with osteophytes, and PE-inlay loosening received revision surgery. Conclusion Excellent clinical results can be obtained by the shoulder arthroplasty using the UNIVERS 3-D prosthesis with low incidence of radiolucency and postoperative complication.

Objective To investigate the clinical experiment of arthroscopically assisted debridement and tibiotalar arthrodesis with half-ring sulcated external fixator for treatment of total ankle joints tuberculosis. Methods From January 2001 to April 2005, 6 patients (4 males and 2 females), with a mean age of 33 years old (range, 28 to 44 years old) and mean duration of 13 months, received arthroscopically assisted debridement and tibiotalar arthrodesis with half-ring sulcated external fixator. All patients had received at least 3 weeks standard drug treatment for tuberculosis before the operation. After thoroughly debridement under arthroscopy using anterolateral and anteromedial approaches, a half-ring sulcated external fixator was used to fix the ankle joint at the neutral position. 4 days (2-7 days) after the operation, patients could walk with partially weight bearing. All patients replied to our questionnaire and the average follow-up was 21.3 months, with a range of 6-42 months. Patients returned for a clinical and radiolographic evaluation every week before the tibiotalar joints union. The external fixator apparatus were removed after the joint fused. Results Fusion occurred in all patients, the average time to clinical and radiographic union was 12.5 weeks (9-17 weeks). 3 patients were graded as excellent: no pain with a stable fusion. The others were graded as good: mild pain, occasional limp with a stable fusion. There were no sinus or other complications occurred. Conclusion There are considerable advantages using arthroscopically assisted debridement and tibiotalar arthrodesis with half-ring sulcated external fixator for treatment of total ankle joints tuberculosis without serious bone defect, include: limited invasion, quickly recovery, thoroughly debriding the tuberculose focus. And the half-ring sulcated external compression fixator could achieve stable and elastic fixation with adjustable rigidity. And patients can walk earlier to promote ankle fusion and decrease related complications.