Digital orthopedic technologies are increasingly being applied to the clinical practice of joint surgery. These technologies include artificial intelligence, virtual/augmented/mixed reality, 3D printing, computer navigation, robotic-assisted joint replacement surgery, and other digital orthopedic technologies. Digital orthopedic technologies continue to empower joint surgeons, simplify complex operations, achieve precision in simple operations, and to make precise operations more individualized. Thus, they are becoming important development directions for joint surgery in the future. With the help of advances in computer-aided design and additive manufacturing technology, customized joint prostheses and bone tissue repair materials provide great convenience for reconstruction of complex bone defects during revision surgery. Various types of computer-assisted navigation technologies and robot-assisted surgery technologies can help doctors improve the accuracy of osteotomy and prosthesis implantation significantly. However, to fundamentally improve patients' satisfaction after joint replacements, we need to use digital orthopedics technologies to explore the ideal target value of arthroplasty. Further, we use personalized preoperative planning with objective and accurate assessment technology of soft tissue balance, precise intraoperative operations, and the use of customized prostheses to achieve individualized and precise joint arthroplasty. Various digital orthopedic technologies have their own advantages and disadvantages. Joint surgeons should have an in-depth understanding of these technologies and make full and reasonable use of these technologies to benefit the majority of patients.

Objective To compare the effect between computer assisted navigation total knee replacement and conventional total knee replacement on rotation alignment,mechanical axes,comPOnent position and clinical outcomes.Methods Eighty-two patients were recruited into this pmspoctive study according to entry criteria and were randomly selected into either control group which treated with standard knee replacements or navigation assisted group which operated with navigation assisted total knee replacements.To analyze the rotation of the femoral component and the tibial component in the transverse plane.the combined rotation of both components and mismatch between two components,the mechanical axes,which were measured from postoperative radiographs and computed tomography images.To compare the functional outcomes at 6 weeks and 6 months.Results There were significant diffefences(P＜0.05)in following parameters between control group and navigation assisted group:average rotation of femoral component were 1.51°±3.55°in control group and-0.63°±3.04°in navigation assisted group,the combined rotation of both components were 2.85°±4.07°in control group and 0.28°±3.43°in navigation assisted group,mismatch between components were 1.44°±4.55°in conlrol group and-0.43°±2.86°in navigation assisted group.There were no significant differences between two groups in rotation of tibial component.In addition,analysis showed that patients in navigation assisted group had significantly better mechanical axes and functional outcomes at 6 weeks.Conclusion The use of navigation can help avoid malrotation and errors in axial rotation,and provides improved alignment accuracy as well as better functional outcomes at 6 weeks.

Objective To analyse the causes of non-union and delayed union in distal femur and assess the clinical outcomes of retrograde intramedullary interlocking nail(RIIN). Methods Between June 1995 and December 1998, 15 cases of non-union and delayed union of distal femur were treated with RIIN. There were 9 males and 6 females, the average age of the patients was 34.5 years(range 23 to 46 years). At surgery, the failed implants were removed in all 15 cases, bone graft was performed in 10 cases, closed reaming was done in 5 cases. 11 patients also received knee adhesion release operation. The X-ray examination and KSS knee functional score were used to evaluate the results. Results The average duration of follow-up was 14.5 months. All patients achieved solid bone union at an average of 6.4 months. There were no malunion, infection and refracture in this series. According to the KSS rating system, the average range of motion(ROM) was 93.5 degrees, increased by 28 degrees(42.7％ ) compared with the preoperation ROM. The average knee score was 96 points. The excellent result was obtained in 13 cases, good in 2 cases. The average knee function score was 90.5 points. Conclusion The main reasons for non-union and delayed union were improper selection of the indications and use of implants. Retrograde intramedullary interlocking nail is one of the effective alteratives for treatment of distal femur non-union and delayed union. It can provide a stable and reliable fixation which is of benefit for early functional exercise. Bone grafting, closed reaming technique and knee joint adhesion release should be considered in order to enhance the bone healing and the improvement of knee ROM and function.

ObjectiveTo study the influence of stress－ relaxation plate on disorganization andrepair of the cortex under the plate. MethodsA washer made of viscoelastic polyethylene was placedbetween the screw and the screw hole of a conventional stainless rigid plate(RP) to form a stress－ relax-ation plate(SRP). Both SRP and RP were applied to the osteotomized New Zealand rabbit tibia, thefracture healing process of either fixing with SRP or RP(control) was put under comparative study bypolarized light microscopy, in situ hybridization of collagen mRNA and immunohistochemistry tech-nique from 2 to 36 weeks postoperatively. ResultsThe study of plated bone remodeling showed thatthe degree of cortex osteoporosis beneath the plate was similar between the SRP and RP group 12 － weekpostoperatively. The organization of the bone structure in the SRP group happened later and milder thanthat of the RP group, and the repair process began 12 weeks after implantation. So the resorption cavi-ties became smaller and the structure of collagen fibers became well oriented along, and the osteoblastslying on the surface of resorption cavities expressed and synthesized type Ⅰ collagen 8 to 12 weeks afterimplantation. The changes above increased significantly in most cavities by 36 weeks. No expression andsynthesis of any kind of collagen could be observed during 12 to 36 weeks after implantation in the RPgroup. ConclusionWithout removal of the bone plate, the SRP fixation not only reduces the degreeof plated bone osteoporosis, but also makes the disorganized bone structure return to normal by the ex-pression and synthesis of type Ⅰ collagen mRNA of osteoblasts lying on the surface of resorption cavities.

Objective To investigate the influence of low frequency micromovement induced by an external fixator with controlled micromovement device on callus formation and fracture healing. Methods 39 sheep were involved in the study. After transverse osteotomy with a gap of 2 mm was done at the mid-shaft of both tibias, the hind limbs were fixed with unilateral external fixators with controlled micromovement device. 10 days after osteotomy, one hind limb of the sheep was randomly selected to have micromovement. According to different micromovement frequencies, the sheep were randomly divided into 3 groups: Group A, 0.5 Hertz; Group B, 1 Hertz; Group C, 5 Hertz. The micromovement had an amplitude of 0.25mm and stopped by the end of the fourth postoperative week (30 min/d). The other hind limb of each sheep did not have micromovement and served as the control. Macrostructural and histological observations, radiographic examinations, and biomechanical tests were done respectively at 4, 6, 9 weeks after osteotomy. Results Macrostructural observations and X-ray examinations revealed a large amount of callus formation with a peak at the end of the fourth postoperative week in the 3 experimental groups. Histological analysis showed faster endochondral ossification and osteoid formation in the experimental groups than in the control by the sixth postoperative week, with the highest rate in Group B (1Hz). Biomechanical tests proved that the bending stiffness in the experimental groups was superior to that in the control, with the strongest in Group B (1 Hz). Conclusions Low frequency-micromovement at the fracture sites can promote callus formation and accelerate mineralization at the early stage of fracture healing. A frequency of 1 Hz can produce the best results.

Objective To observe the differences of the reactive oxygen species(ROS) and mitochondrial membrane potential(??m) in mitochondrial DNA-depleted SK-Hep1 and its parent cells.Methods ?0SK-Hep1 cell line was generated by treating SK-Hep1 with ethidium bromide.Flow cytometry(FCM) and laser scanning confocal microscopy were used to detect ROS and ??m.Results Fluorescence intensity of ROS in ?0SK-Hep1 cells was significantly higher than that of the parent cells(35.5 vs 15.6),and the ??m was lower in ?0SK-Hep1 cells(55.0 vs 65.9).Conclusion ?0SK-Hep1 cells showed elevated ROS and lower ??m.These changes might contribute to the variation of phenotypes.

Objective To analyse the reasons of failure of metal- backed patellar component and observe the clinical outcome of the revision procedure. Methods Thirty isolated patellar revision for failed metal- backed patellar components following total knee arthroplasty in 22 patients were reviewed. All had similar total condylar knee prosthesis inserted with retention of the posterior cruciate ligament and resurfacing of the patella. There were 4 males and 18 females. Knee Society Score rating system was used for the final evaluation. Results In average the failure occurred in 62.3 months (ranged from 26 to 96 months). The majority of patients presented with metallic crepitus(80％ ) and pain of the knee(70％ ). At surgery, full thickness polyethylene wear exposing the metal- backing was present in 76.7％ with surface damage of the femoral components in 36.7％ . There was tilting of patella in 9 knees and dislocation of patella in 2 knees. All 30 knees underwent successful isolated patellar component revision with cemented polyethylene patellar buttons. Final follow- up averaged 42.5 months, all manifestations were reported significant improvement in 22 patients. The average knee score improved from 73 points(ranged from 27 to 88) pre- revision to 87 points(ranged from 60 to 100) at the final follow- up. Conclusion Resurfacing of the patella in total knee arthroplasty with metal- backed patellar components carries a significant risk of early failure. Malalignment and maltracking of patella may be a predisposing factor to early failure in metal- backed patellar components.

[Objective]To observe whether erythromycin and alendronate are effective in treating aseptic loosening in a murine osteolysis model. [Method]Air pouches were established in the back of BALB/c mice by injecting sterile air subcutaneously. After the air pouches were mature, grafts of calvaria from syngeneic mouse donors were implanted in the air pouches and polyethylene debris was injected into the air pouches. Mice were divided into 4 groups. In the first group, saline was injected into the air pouches.In the other three groups, polyethylene debris was used. Saline,erythromycin and alendronate were injected intraperitoneally separately.Pouch tissues were collected at 14 days after polyethylene debris administration for molecular and histologic analysis.[Result] Both erythromycin and alendronate inhibited osteoclastogenesis and bone resorption, but alendronate was not as effective as erythromycin in anti-inflammation.[Conclusion]Both erythromycin and alendronate can be promising drugs for the treatment of aseptic loosening.

Objective To investigate and discuss the feasibility and clinical outcome of the minimally invasive two-incision total hip arthroplasty. Methods From February to June 2004, 17 cases of the minimally invasive two-incision total hip arthroplasty were performed. There were 7 males and 10 females with an average age of 69 years from 58 to 75 years. Preoperative diagnosis of the patients included 5 of osteoarthritis, 4 of osteonecrosis and 8 of femoral neck fracture. The operations were performed with Versys cementless prosthesis and minimally invasive instruments provided by Zimmer Company. Operation time, blood loss, length of incisions, average postoperative hospitalization, and operation related complications were analyzed. Blood transfusion was performed while hemoglobin of the patients was less than 8 g. Results The patients were followed up from 6 to 12 months with an average of 8 months. The average operation time was 95 mins (85 to 170 mins). The average blood loss was 280 ml (190 to 450 ml) and blood transfusion was carried out in 4 cases of femoral neck fracture (average, 400 ml). The average length of anterior incision was 5.0 cm (4.6 to 6.5 cm) and that of posterior incision was 3.7 cm (3.0 to 4.2 cm). All the patients were ambulatory the day after surgery. 11 cases were discharged 5 days and 6 cases discharged 7 days after operation. Postoperative measurement on X-ray film showed that the average angles of abduction and anteversion of acetabular cup were 46?(43? to 55?) and 21?(17? to 23?) respectively. Proximal femoral split fracture occurred in one case, in which the fluoroscopy demonstrated the femoral component was stable and well positioned, and the patient walked without weight-wear for 2 months and was found with stable prosthesis evaluated at 3 and 6 months postoperatively. None of infection, dislocation or injury of vessel and nerve happened. Conclusion Anterior and posterior two-incision total hip arthroplasty has the advantages of muscle sparing, minimally invasive, less blood loss, rapid recovery; however, this technique is time consuming, special instruments and fluoroscopy are needed.

Objective　To explore the influence of stress-relaxation plate(SRP) fixation on the remodeling of cortex under plate. Methods　Twenty-eight New Zealand rabbits were used in this study, the bilateral tibia were osteotomized in the middle and fixed with SRP (experimental group) and rigid plate (control group) respectively. The scanning electron microscopy was used to observe the bone remodeling process from 2 to 48 weeks after operation. Results　There was cortex osteoporosis beneath plate in different degree in both experimental and control groups before 8 weeks, it showed as the disorganization of collagen fiber structure and formation of resorption cavities. In comparison, the osteoporosis degree in experimental group showed milder than that of the control group. After 12 weeks, the resorption cavities became smaller, and the structure of collagen fibers became regular with the alignment parallel to the long axis of cortex. In contrast to the experimental group, the bone osteoporosis under plate of control group exacerbated continuously. Conclusion　Without removal of the bone plate, SRP fixation not only reduce the degree of plated bone osteoporosis, but also make the osteoporosic bone return to normal.