Analysis of factors affecting the change in relative patellar height after robotic-assisted primary total knee arthroplasty / 中华骨科杂志

Objective:To analyze the factors affecting the relative height change of the patella after primary robotic-assisted total knee arthroplasty (R-TKA).Methods:The data of 97 patients with osteoarthritis of the knee treated with R-TKA admitted from June 2021 to March 2022 were retrospectively analyzed, including 15 males and 82 females, aged 70.0±5.4 years (range, 58-80 years). The bone resection parameters of the robotic system were recorded intraoperatively, including the bone resection amount of the medial and lateral distal femur, medial and lateral posterior femoral condyle and medial and lateral tibial plateau. The Blackburne-Peel index (BPI) and Caton-Deschamps index (CDI) were used to measure the preoperative and postoperative relative patellar height on lateral radiographs, as well as the posterior tibial slope (PTS) and the change in patellar ligament length before and after surgery. The relationship between the change in relative patellar height and the variables of interest was analyzed using partial correlation and multiple linear regression.Results:The mean postoperative CDI was lower than preoperatively (0.79±0.15 vs. 0.91±0.13, t=9.69, P<0.001), and the percentage of patients with postoperative CDI<0.6 was higher than preoperatively (9.3% vs. 0; χ 2=12.92, P<0.001); the differences in mean postoperative BPI and percentage of patients with postoperative BPI<0.45 were not statistically significant compared to preoperatively (0.69±0.13 vs. 0.71±0.17, t=1.35, P=0.182; 11.3% vs. 17.5%, χ 2=1.50, P=0.220). The mean patellar ligament length on the first postoperative day was 2.29 mm shorter than preoperatively, there was a statistically significant difference ( t=5.90, P<0.001). Partial correlation analysis showed that the amount of patellar ligament length change was positively correlated with the amount of BPI and CDI change ( r=0.84, P<0.001; r=0.70, P<0.001), and the amount of PTS change and the mean distal femoral bone resection were negatively correlated with the amount of BPI ( r= -0.41, P<0.001; r=-0.32, P=0.002) and CDI ( r=-0.23, P=0.029; r=-0.25, P=0.017) change. In contrast, the amount of posterior femoral condyle bone resection and tibial plateau bone resection did not correlate with the change of BPI and CDI. Multiple linear regression analysis showed that the amount of patellar ligament length change, PTS change and the distal femoral bone resection were factors influencing the change of BPI ( β=0.03, P<0.001; β=-0.01, P<0.001; β=-0.02, P=0.021) and CDI ( β=0.02, P<0.001; β=-0.01, P=0.001; β=-0.02, P=0.008). Conclusion:Amount of patellar ligament length change, PTS change and the distal femoral bone resection are factors affecting the BPI. In order to obtain a better relative patellar height in the primary R-TKA, attention should be paid to the adjustment of the distal femoral bone resection and PTS, while taking the necessary measures to reduce the postoperative patellar ligament length changes.

The future of joint surgery: the application of digital orthopaedic technology in joint surgery / 中华骨科杂志

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.

Intra-articular hyaluronic acid injection for knee osteoarthritis / 中华骨科杂志

As one of the major causes of disability in the elderly population,knee osteoarthritis is a common degenerative joint disease.The general treatment approaches for knee osteoarthritis include physical therapy,nonsteroidal anti-inflammatory drugs (NSAIDs),intra-articular injection of steroid hormones,viscosupplementation and surgery,etc.Hyaluronic acid (HA) is a kind of macromolecule which plays pivotal roles in the articular physiology as a key component of synovial fluid and cartilage.Intra -articular injection of hyaluronic acid (IA-HA) is established as a local therapy to restore the viscoelasticity of synovial fluid and achieve physiological stability.Numerous clinical trials have demonstrated that IA-HA is effective in relieving pain and reducing structural damage in patients with knee osteoarthritis.Generally,the pain-relieving activity of IA-HA is comparable to or higher than that of NSAIDs,intra-articular corticosteroids,and physical therapy.In addition,IA-HA treatment is tolerated and is associated with less adverse events in comparison with NSAIDs,which elicits gastrointestinal bleedings and is associated with increased mortality.Studies in the mechanisms of action also revealed that HA could specifically bind to the membrane receptor (such as CD44) and adhesion molecules (ICAM-1) in cells.The connection may stimulate functional activities,including cell migration and proliferation.However,debates on whether hyaluronic acid produces significant clinical benefits still exist in the literature and different clinical practice guidelines.The variability in pharmaceutical property of different HA products,the severity of knee osteoarthritis,treatment protocol and injection technique can potentially have impacts on the outcomes of treatment of knee osteoarthritis with IA-HA.

Predictors for outcome of exchange arthroplasty for periprosthetic joint infections after primary total knee arthroplasty / 中华传染病杂志

Objective To evaluate the overall failure rate of one or two-stage exchange arthroplasty for infections in total knee arthroplasty (TKA) and the predictors affecting the outcome of exchange.Methods Thirty-nine cases received one or two-stage exchange arthroplasty for periprosthetic joint infections after primary TKA in Shanghai Sixth People's Hospital affiliated to Shanghai Jiao Tong University School of Medicine and Southeast Hospital affiliated to Xiamen University from January 2012 to November 2014 were reviewed.Periprosthetic tissue and articular fluid of all patients were analyzed by bacterial culture.All patients were followed up for more than one year.C-reactive protein (CRP),erythrocyte sedimentation rate (ESR),procalcitonin (PCT) and blood routine were tested every four weeks,and the evaluation on pain,total periprosthetic function,range of motion and deformation of arthroplasty were conducted.Differences between groups were analyzed using chi-square test or Student's t test when appropriate.A stepwise selection approach in logistic regression analysis was used to screen key predictors for outcome of one or two-stage exchange for infections in TKA.Results There were 39 patients who had undergone one or two-stage exchange for infections in TKA,including 20 males (51.3％) and 19 females (48.7％) with an average age of (62.4±11.7) years.Among the 39 patients,18 gram-positive strains were isolated from specimens,and 6 gram negative strains,2 Mycobacterium tuberculosis and 1 candida albicans.Ten of 39 reimplantations developed reinfection.Between the success and failure groups,there were significant differences in the time from primary TKA to revision (P =0.023),operative time (P =0.029),multidrug resistant organisms (P =0.045),the preoperative and post-operative ESR (P=0.002 and P＜0.001,respectively) and post-operative CRP (P=0.018).Multivariable logistic regression analysis demonstrated that time from primary TKA to revision (OR =0.96,95％CI:0.92-1.00,P=0.025),preoperative ESR (OR=0.97,95％CI:0.95-1.00,P=0.045) and post-operative ESR (OR =0.94,95％ CI:0.91-0.98,P =0.002) were independent indicators associated with the outcome of one or two-stage revision.Conclusions The failure rate after revision for infected TKA is relatively high.The time from primary TKA to revision,preoperative and post-operative ESR could predict the outcome of one or two-stage revision effectively.

The incidence and risk factor for agitation after the general anesthesia from 500 pediatric patients / 重庆医学

Objective To identify the incidence and risk factors that are associated with agitation after general anesthesia from 500 pediatric patients .Methods Data about any kinds of the index from 500 pediatric patients ,ASA Ⅰand Ⅱ ,receiving gen‐eral anesthesia were recorded .such as the age ,sex ,weight ,anxious before the anesthesia ,kinds of the disease ,class of ASA ,kinds and dosage of the anesthesia drug ,such as ketamine ,propfol ,sevoflurane ,fentanyl ,the intubation ,length of anesthesia time ,the re‐covery time and the agitation grade .According to the agitation grade ,all the patients divided into two group ,the agitation group and the non‐agitation group .Logistic regression with a descending stepwise algorithm was performed to identify independent variables . The discriminative power of the Logistic regression model was checked with a receiver operating characteristic curve .Results Agi‐tation meeting the predefined criteria occurred in 153 patients(30 .6% ) .The Logistic analysis identified the following varables to be associated with agitation after the anesthesia:age ,sex ,weight ,anxious before the anesthesia ,the use of the ketamine and the sevoflurane ,the intubation .The agitation correlation coefficients for the age ,sex ,and the use of the ketamine were negative ,other‐wise the weight ,anxiety ,the use of sevoflurane and the intubation were positive .The area of ROC was 0 .850 .Conclusion This study contributes to the identification of patients with a high risk for agitation after general anethesia .The index of the age ,sex , weight ,anxious before the anesthesia ,the use of the ketamine and the sevoflurane ,the intubation should be comprehensive evalua‐ted .

Incidence and risk factors of hypotension after spinal anesthesia induction in 1 000 patients / 中华全科医师杂志

The clinical parameters of 1 000 patients undergoing spinal aesthesia were recorded and analyzed.Hypotension fulfilling the predefined criteria occurred in 173 patients.The logistic regression analysis revealed that the regression coefficients of height,weight and amount of fluid infusion during anesthesia were negative while those of age,emergency operation,hypertension/hypotension,heart disease,American Society of Anesthesiologists score,use of sedative drugs and sensory blocking level of anesthesia positive.The area of receiver operating characteristic was 0.905.This study contributes to the identification of patients with high risks for hypotension after spinal induction.

Pathogenic analysis in different types of orthopedic implant infections / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Diversity of orthopedic infections with various local environments affects the pattern and prevalence of pathogens. It is not well-characterized whether different pathogens have different propensity to cause different types of orthopedic infections. We aimed to investigate the frequency of different pathogens derived from orthopedic infections, and determine the relationship between the prevalence of clinical isolates and the type of orthopedic implants, especially focusing on staphylococci.</p><p><b>METHODS</b>From January 2006 to December 2011, orthopedic infections were identified retrospectively from clinical microbiology laboratory and orthopedic medical records. The sources of orthopedic infections were divided into two main groups: those associated with implants and those not associated with implants. Implants-associated infections were further subdivided into five subgroups: arthroplasty, internal fixation, external fixation, internal and external fixation, and others. We analyzed microbiological spectrum in different groups and subgroups. Antibiotic susceptibility of staphylococci was analyzed.</p><p><b>RESULTS</b>Only coagulase-negative staphylococci (CoNS) was significantly more likely to be associated with implants-associated infections (P = 0.029). The overall pathogens prevalence of arthroplasty was significantly different from other subgroups (P < 0.05). 65% isolates from external fixation was Gram-negative bacteria. Some percentage (55%) of S. aureus and (83%) CoNS were resistant to methicillin. No resistance to glycopeptide was seen in all of staphylococci.</p><p><b>CONCLUSIONS</b>Staphylococcus aureus was the most frequent isolates in orthopedic infections but was not associated with the presence or absence of implants. Only CoNS was implants-associated, especially for arthroplasty infection. Cefazolin alone is not enough for orthopedic surgery prophylaxis in settings with a high prevalence of methicillin-resistant staphylococci.</p>

Analgesic efficacy of parecoxib in total knee arthroplasty and total hip arthroplasty surgery / 中华创伤杂志

Objective To evaluate the analgesic effect of parecoxib in total knee arthroplasty (TKA) and total hip arthroplasty (THA).Methods The study was a prospective,randomized and double-blind trial and was operated by the same group of surgeons in 101 patients with TKA and 105 patients with THA.According to analgesic protocol,the patients were divided into three groups:Group One ( intravenous injection with parecoxib),Group Two ( periarticular injection with parecoxib) and Group Three ( the control group).The postoperative visual analog scores (VAS),range of motion ( ROM),the ability of straight leg raising and the incidence of nausea and vomiting complications were examined and compared between the three groups.Results There were no significant differences in VAS (6,12,24,36,48,72 hours after operation),ROM ( 24 hours after operation) and the ability of straight leg raising between Group One and Group Two ( P ＞ 0.05 ),but all of them were significantly higher than those in Group Three ( P ＜ 0.05 ).Nausea,vomiting and other adverse effects did not significandy increase with the use of parecoxib.Conclusions Both intraoperative intravenous injection and periarticular injection with parecoxib have a good analgesia effect on TKA and THA,which are beneficial to the rapid recovery of joint function in patients.The simple and practical method provides an effective adjunct to a multimodal analgetic approach in improving the postoperative course of TKA and THA.

Hip arthroplasty for failed internal fixation of intertrochanteric fractures / 中华骨科杂志

Objective To respectively analyze the results and complications of hip arthroplasty for failed intertrochanteric hip fractures treating with internal fixation.Methods From July 2004 to June 2006,32 patients(24 males and 8 females)were treated with hip arthroplasty after the failed internal fixation of intertrochanteric fractures.The mean age was 71 years(range,57-81 years)at the time of the hip arthroplasty.The average interval from fracture to arthroplasty was 40 months(range,5-70 months).Fifteen patients had been treated with sliding hip screw,10 with intramedullary nail,5 with plate and screws,2 with multiple screws.The failure modes were nonunion in 8 patients,implant cut out from the femoral head in 9,avascular necrosis of the femoral head in 7,and traumatic arthritis in 8 patients.Cemented stems were used in 12 hips,and uncemented stems in 20 hips.Standard prostheses were used in 25,long-stem prostheses in 7.Results Twenty-eight patients were followed up for a minimum of 4 years after the hip arthroplasty,with the mean period of 5 years(range,4-6 yeas).For these 28 patients,the average preoperative Harris Hip Score was 37(range,32-45),and 88(range,84-95)at the latest follow-up.The average acetabular inclination was 44°(range,42°-48°).No loosing was found in cotyloid components.Nine of 10 cemented femoral components had cementation rated as grade C,and 1 as grade A.Three had heterotopic bone six months postoperatively,and 2 were Brooker type Ⅱ,one was type Ⅲ.Conclusion Hip arthroplasty is an effective salvage procedure after the failed treatment of an intertrochanteric fracture in an older patient.

Gait analysis of patients with resurfacing hip arthroplasty compared with metal-on-metal bigfemoral-head total hip arthroplasty / 中华骨科杂志

Objective To compare gait patterns in patients with metal-on-metal resurfacing hip arthroplasty(RHA)and big-femoral-head total hip arthroplasty(BHA)at one year postoperatively.Methods From June 2006 to March 2009,two groups of 30 RHA and BHA patients participated in the study.Gait parameters,knee and hip joint range of motions(ROMs)in gait cycles were measured at one year postoperatively by Vicon gait analysis system,and the values were used to calculate affected/unaffected ratios of patients themselves.Results No significant difference were found in affected/unaffected ratios of cadence,single limb support time,foot off,peak value of vertical ground reaction force,the hospital for special surgery score and the university of California at Los Angeles activity assessment between the two groups.However,several ROM affected/unaffected ratios in RHA group(hip range of flexion/extension,abduction/adduction,and rotation were 1.0323,0.9747,and 1.0558,respectively.The knee range of flexion/extension for affected/unaffected ratios was 1.0027)were significantly higher than those in BHA group(the corresponding values were 0.8615,0.7824,0.8162,0.9472,respectively).The P values were 0.007,0.005,0.006,and 0.037,respectively.Conclusion(1)Gait parameters of patients who underwent RHA and BHA were close to normal values at one year postoperatively.(2)At the follow up time point,joint ROMs of RHA patients are larger than those of BHA patients during gait cycle.(3)RHA can retain enough bone stock for future revision option,moreover,it can achieve maximum recovery of joint function.

Biomechanical comparison of surgical operation and non-operation therapy for acute damnification of elbow ulnar collateral ligament in rabbits / 中华创伤杂志

Objective To compare the difference of therapeutic effect of surgical operation and non-operation for acute damnification of elbow ulnar collateral ligament in rabbits.Methods A total of 81 New Zealand rabbits were randomly and equally divided into three groups(27 rabbits per group),ie,Group A(control group):the ulnar collateral ligaments of right elbow joint were only enclosed;Group B:the ulnar collateral ligaments of right elbow joint were severed and sutured;Group C:the ulnar collateral ligaments of right elbow joint were severed,without suture.The biomechanics was detected at time intervals of 3 and 6 weeks.Results Twelve weeks after transplantation,the displacements of the ligaments in Groups B and C were(6.06±0.4)mm and(7.72±0.44)mm,with statistical difference(P ＜ 0.05).The displacement of the ligaments in Group A was(5.87±0.46)mm,which was similar to that of Group B(P＞0.05).The maximum loads of the ligaments of Groups B and C were(68.23±5.64)N and (42.45±3.66)N respectively,with statistical difference(P＜0.05).The maximum load of the ligaments of Group A was(72.86±2.99)N,which was similar to that of Group B(P ＞ 0.05).The rigidities of the ligaments of Groups B and C were(11.33±1.52)N/mm and(5.52±0.67)N/mm respectively,with significant difference(P ＜ 0.05).The rigidities of the ligaments of Group A was(12.49±1.44)N/mm,which was similar to that of Group B(P ＞ 0.05).The power consumption of the ligaments of Groups B and C were(0.206±0.017)J and(0.163±0.013)J respectively,with statistical difference(P＜0.05).The power consumption of the ligaments of Group A was(0.213±0.010)J,which was similar to that of Group B(P＞0.05).Conclusion Surgical operation is more effective than the non-operation in dealing with acute damnification of the ulnar collateral ligaments of elbow ulnar collateral ligament in rabbits.

Meta-analysis of literatures on hip arthroplasty treating femoral neck fracture in the elderly / 中华创伤杂志

Objective To analyze the literatures on arthroplasty treating femoral neck fracture in the elderly so as to evaluate the value of arthroplasty in treating femoral neck fracture in the elderly. Methods The literatures published from 1991 to 2007 on arthroplasty treating femoral neck fracture in the elderly were retrieved via PubMED and Ovid database to compare the mortality. Dislocation, revision and Harris score after operation. The heterogeneity was tested and the data dealt by meta-ana]ysis. Then, we talculated the OR value and 95% confidence interval. Results The study included 10 related pa-pers involving hemi-arthroplasty(HA)and total hip arthroplasty(THA)treating femoral neck fracture in the elderly. There was no statistical difference between HA and THA in aspect of mortality. No heteroge-neity existed in dislocation and revision, with the Q value of 4. 03 and 2. 78 respectively(P>0. 1). THA had a high dislocation rate but lower incidence of revision, in comparison with HA. The heterogeneity of Harris score was confirmed with the Q value of 23. 94(P<0. 1), with relative risk(RR) of 0. 79, OR of 0. 35 and 95% CI of 0. 23-0. 53. Conclusions As for hip function recovery, THA is better than he-mi-arthroplasty and THA should be the first choice for femoral neck fracture. However, for patients who can not tolerate operation or have anticipated life span less than 5 years, hemi-arthroplasty should be cho-sen.

The effect of computer assisted navigation on axial alignment of lower extremity in total knee replacement / 中华骨科杂志

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.

Anatomic and clinical retrospective study of two-incision minimally invasive total hip replacement / 中国综合临床

Objective To investigate the safe zone and the soft tissue damage of two-incision minimally in-vasive total hip replacement,and to retrospectively analyze the clinical result.Method 20 adult cadavers(40 hips) were used for anatomic research.The Course of the later femoral cutaneous nerve was recorded.The angle between the intermission of the piriformis muscle and gluteus medius muscle with horizontal plane was also recorded.Analogue operation was taken on 3 fresh cadavers to assess the injury extent of soft tissues around incisions.27 cases under-went two-incision minimally invasive total hip replacement.Results LFCN was found potentially at risk as far as 6～71 mm medial to anterior superior iliac spine(ASIS)along the inguinal ligament,as much as 21～112 mm distal on the lateral border sartorius muscle from the ASIS.With the operative leg fully adducted,flexed over the nonopera～tire leg and the patella placed horizontal,the angle between the intermission of the piriformis muscle and gluteus medius muscle with horizontal plane is(60±5)°(range 55°-68°).Imitating modified two-incision THA on 3 freshhips revealed muscle contused on gluteus medius-piriformis muscle and gluteus minimus muscle.The average length of the anterior incision was 5.0 cm(4.6～6.5 cm)and of the posterior incision 3.7 em(3.0～4.2 cm).All of the patients were ambulant the day after surgery.Blood transfusion was carried out in 4 cases including one case of femo-ral neck fracture.The patients were followed up for 18 months(13～25 months).No other complications occurred.The mean Harris score was 94.5(92～96).Conclusion Front incision from the point inferior ASIS 3 cm and 1cmlater from ASIS vertically 6 cm should be chosen and the real incision should be 60°with horizontal plane.GIuteus medius,piriformis muscle and ghteus minimus muscle will be contused in two-incision minimally invasive surgeryto-tal hip replacement.Two-incision total hip replacement has the advantage of being muscle sparing and minimally in-vasive with less blood loss and rapid recovery.However,this technique is time consuming,technically demanding,and requires fluoroscopy.

Erythromycin and alendronate inhibit aseptic loosening in murine osteolysis model / 中国矫形外科杂志

[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.

Experimental study on influence of controlled low frequency micromovement on fracture healing / 中华创伤骨科杂志

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.

Developmentof micromovement external fixture for treatment of bone fracture / 医疗卫生装备

The s tr ucture of a micromovement external fixture for treatment of diaphyseal long bo ne fracture is presented in this paper.Minisize DC geared motor and screw drive are used to transmit the power.Micro controller is used to control the micromove ment extent and frequency.This device can give the fractured bone ends micromo vement stress stimulation,so as to improve the forming and calcifying of the ca llus,and to accelerate the fracture healing process.This device can be applied t o the research on micromovement treatment of bone fracture.

Isolated metal- backed patellar component revision following total knee arthroplasty / 中华骨科杂志

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.

Total hip arthroplasty using the minimally invasive two-incision approach / 中华骨科杂志

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.

THE EFFECT OF STRESS-RELAXATION PLATE FIXATION ON THE REMODELING OF THE CORTEX UNDER PLATE / 中国修复重建外科杂志

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.