Biomechanical Study on Personalized Titanium Alloy Short Femoral Prosthesis / 医用生物力学

Objective To evaluate biomechanical properties of the personalized titanium alloy short femoral prosthesis by finite element analysis. Methods Based on the validated femoral finite element model, the base of the femoral neck was simulated, and by inserting different short femoral prostheses, four total hip replacement (THR) models, namely, the SMF stem model (Model A), BE1 stem model (Model B), MINI stem model (Model C) and personalized stem model (Model D) were established, respectively. The same loads and constraints were applied to four groups of models, and the von Mises stress distribution and deformation were calculated and analyzed, so as to compare mechanical stability of each model. Results The deformation of all THR models was smaller than that of the femur model under physiological state. The deformation of Model B was close to that of Model C, and the deformation of Model A was close to that of Model D. The peak stress of Model C was higher than that of the other 3 models, reaching 9555 MPa. The overall stress trend was Model C > Model B > Model D> Model A > Model under physiological state. Conclusions The peak stress, stress distribution of personalized short femoral stem were similar to that of SMF stem, with reasonable stress distribution, small stress shielding of the proximal femur, minimum overall deformation and shear stress of the prosthesis, and its effectiveness and stability could meet the requirements of human biomechanics, which could provide references for joint surgeons and prosthesis researchers.

Effects of femoral prosthetic materials on artificial knee arthroplasty performance / 中国组织工程研究

BACKGROUND: Aseptic loosening of the femoral prosthesis is one of the important issues affecting the life of knee joint replacement. Particles from tibial polyethylene component wear and stress shielding are the main causes of this loosening, which are all related to the femoral prosthesis materials. OBJECTIVE: To study the effects of femoral prosthesis materials on the stress of the distal femur of the knee joint and the contact pressure on the polyethylene component by finite element method. METHODS: Knee arthroplasty models with four materials, titanium alloy, cobalt-chromium alloy, titanium-hydroxyapatite functional gradient biomaterial (FGBM I), titanium-bioactive glass functional gradient biomaterial (FGBM II), were established; the prosthesis was endowed with different material properties in the Abaqus finite element software. The stress distribution of the important vulnerable path in the femur and the changes of contact pressure on the polyethylene component under different materials were studied. RESULTS AND CONCLUSION: (1) Compared with the currently used titanium alloy and cobalt-chromium alloy, functional gradient biomaterials could significantly increase the stress at the femoral-prosthetic interface and the stress in the pathway of an important vulnerable region of the femur. In those materials, FGBM I increased most significantly. (2) Maximum stress of FGBM I and FGBM II prostheses on polyethylene insert was 20.41% and 19.98% lower than cobalt-chromium alloy, 20.07% and 19.63% lower than titanium alloy. (3) The results showed that functionally gradient biomaterials could produce higher stress at the distal end of the femur and lower contact pressure on the polyethylene insert, reducing the wear and stress shield on polyethylene insert, and FGBM I has significant effects.

Total Hip Arthroplasty on Treatment of Traumatic Arthritis Caused by Internal Fixation Failures of Intertrochanteric Fractures / 中山大学学报(医学科学版)

[Objective]To investigate the efficacy of total hip arthroplasty(THA)on the treatment of traumatic arthritis that caused by internal fixation failures of intertrochanteric fractures.[Methods]During January 2009 and March 2016,35 cases of trau?matic arthritis(male:18 cases;female17 cases;49 ~ 86 years old,with an average age of 68.5 years)caused by internal fixation failures or malunion of intertrochanteric fractures,were undergo THA. Among 35 cases,13 cases were performed with the proximal femoral fixation stems,10 cases were with distal fixation stems,and 12 cases were with extended stems.[Results]With 3~65 months follow-up,the hip joint HSS score was elevated from 44.1(31 ~ 65)preoperative to 82.5(58 ~ 94)postoperative without obvious loosening. No postoperative deep infectionwas found. The femoral stems in 2 cases were found to sink 5 mm and 10 mm,respectively. No obvious prosthesis loosening was found. Taken together ,the satisfaction rate of THA on the joint function of traumatic arthritis was 91.4%.[Conclusion]Total hip arthroplasty is recommended as an effective approach for treating traumatic arthritis caused by internal fixation failures of intertrochanteric fractures. Distal fixed prosthesis was recommended due to bone sclerosis or defects of proximal femur. Coupled with emphasis on reconstruction of the greater trochanter ,good therapeutic effects could be achieved.

Ultimate Determination of P.F.C Femoral Prosthetic size in TKR for the Elderly Patients / 대한정형외과연구학회지

PURPOSE: To analyze the clinical and radiologic results after total knee arthroplasties using down-sizing femoral prosthesis for tight fitting in patients over 75 years old. SUBJECTS AND METHODS: The study tracked the histories of 99 elderly patients aged 75 and over who underwent total knee arthroplasties with at least five years of follow-up from January 1st, 2005 to December 31st, 2007. The average age of the 99 patients was 78.58 years, and 17 women an 82 men patients underwent 78 cases of total knee arthroplasties on the right and 77 cases of total knee arthroplasties on the left. The HSS score and VAS scoring systems were introduced for clinical analysis. We compared the results of the width of the radiolucent line in 7 sections around the femoral component, 7 sections around the tibia component and 5 sections in the patella component using the American Knee Society Radiographic Evaluation and Scoring system respectively. RESULT: The average period of postoperative follow-up study was 6.2 years. The average femoral prosthesis size in preoperative measurement was 2.41 while the size selected in surgery was 1.89. The average VAS score decreased from 8.15 in preoperative measurement to 2.85 in postoperative measurement. Clinical significant loosening or dislocation of femoral prosthesis was not observed. Although the radiolucent line was observed in 5 cases, the score was less than 4. CONCLUSION: Total knee arthroplasties using down-sizing femoral prosthesis does not increase osteolysis and dislocation of femoral prosthesis but does reduce pain and help patients return to normal activities. Therefore this study showed that total knee arthroplasties using down-sizing femoral prosthesis helped elderly patients aged 75 and over.

Fractures around femoral prosthesis after artificial hip replacement / 中国组织工程研究

BACKGROUND:With the wide application and in-depth research of artificial hip joint, more secondary fractures around femoral prosthesis are reported. OBJECTIVE:To investigate the reasons, preventive measures, classification and treatment method of fractures around femoral prosthesis after artificial hip replacement. METHODS:The clinical data of the type classification, treatment method and clinical efficacy of fractures around femoral prosthesis after artificial hip replacement were retrospectively analyzed. The multi-level study was performed to investigate the trend of the relevant literatures. According to the Vancouver classification criteria, the various types of fractures and the results and complications of various treatment methods were analyzed, the treatment methods of different fractures were identified, and the effective and objective evaluation criteria were established to provide references for the clinical treatment. RESUTLS AND CONCLUSION:The fractures around femoral prosthesis after artificial hip replacement were closely related with the age of the patients, basic diseases, osteoporosis and selection of prosthesis type. The Vancouver classification criteria and treatment programs have guiding significance to the clinical efficacy. The fractures should be treated with different methods according to the different types in order to promote the fracture healing. The fractures around femoral prosthesis after artificial hip replacement were commonly treated with shape memory alloy embracing fixator, minimal y invasive fixation system, locking compression plate, al ograft cortical bone plates, carbon fiber, impaction bone grafting and renovation. In the practice application, various methods are often used in combination. For the patients with B2 and B3 type fractures, we should pay attention to the bone grafting around the fractures and the inner and outer medul ary cavity.

Early Aseptic Loosening after Total Knee Replacement Using Legacy Posterior Stabilized-Flex Prosthesis / 대한정형외과학회잡지

PURPOSE: We analyzed the patterns and causative factors of early aseptic loosening after total knee arthroplasty (TKR) using a legacy posterior stabilized (LPS)-flex prosthesis. MATERIALS AND METHODS: We examined 483 cases that occurred in 311 patients who underwent TKR using LPS-flex by single surgeon between August 2001 and March 2007 and who were followed-up for at least 2 years. The loosened group included 25 cases that exhibited early aseptic loosening on radiograph, the remaining 458 cases were regarded as the control group, and analysis was performed. RESULTS: The mean loosening period was 34.7 months and femoral component loosening alone was found in 22 cases (88%). There were no statistically significant differences in age, body mass index, or pre-operative range of motion between the 2 groups, but varus deformity was more severe in the loosened group (mean 8.92degrees) than in the control group (mean 5.21degrees) (p=0.003). Protrusion of the femoral component proximally over posterior condyle of the distal femur were more prominent in the loosened group (mean 20.3%) than in the control group (mean 13.4%) (p=0.001). CONCLUSION: Early loosening after TKR using LPS-flex prosthesis developed mostly in the femoral component. Choosing a proper size for the femoral component and cutting level for the distal femur should be considered.

Análisis de la funcionabilidad de prótesis ortopédicas transfemorales / Analysis of the functional qualities of trans-femoral orthopedic prostheses

Introducción: la funcionabilidad de los artificios protésicos de miembros inferiores suele expresarse en términos de relacionar sus beneficios operacionales con aquellas necesidades funcionales y de bienestar del amputado. Este bienestar se relaciona fundamentalmente con un mínimo gasto energético del paciente y con la ausencia de enfermedades en las articulaciones residuales y que se inducen por la prótesis durante el régimen de marcha. Objetivo: evaluar la funcionabilidad de prótesis transfemorales utilizadas en Cuba mediante la integración de los resultados del análisis cinemático de la marcha del amputado, combinados con análisis de mecánica de sólidos rígidos aplicando simulaciones numéricas. Métodos: el análisis de la marcha de 8 pacientes con amputaciones unilaterales transfemorales y 5 sujetos normales (control) se realizó mediante técnicas videográficas. Se efectuó la estimación dinámica de las fuerzas que actúan en los segmentos articulares y se determinaron las tensiones y deformaciones que sufren las zonas del muñón y de la articulación del tobillo mediante el método de los elementos finitos. Resultados: cambios significativos en la dinámica de los segmentos articulados del tobillo-rodilla y cadera se reflejan como el resultado de la asimetría de la marcha del miembro protésico y el sano. Tal desequilibrio sugiere ser una de las principales causas de las enfermedades degenerativas de la cadera observadas en este tipo de paciente. Conclusiones: el análisis de la funcionabilidad de los artificios protésicos transfemorales solo es posible mediante la integración de los métodos cinemáticos de caracterización de la marcha, métodos dinámicos que establezcan la posibilidad de replicar la actividad del miembro sano. Mediante este estudio fue posible además el estudio de la resistencia mecánica y se vincularon todos los resultados a la aparición de enfermedades tanto en el miembro intacto como en el residual

Introduction: the functional quality of the prosthetic devices of lower extremities is usually expressed in terms to relate the functional benefits to those functional needs and the wellbeing of the amputee. This wellbeing is related mainly to a minimal energetic output of patient and to the lack of diseases of residual joints induced by the prosthesis during the gait. Objective: to assess the functional qualities of trans-femoral prostheses used in Cuba by the integration of results of kinematics analysis of the gait of amputee, combined with mechanics analysis of rigid solids applying numerical simulations. Methods: the gait's analysis of 8 patients with trans-femoral unilateral amputations and 5 normal subjects (controls) was made by videographic techniques. The dynamics estimation of strengths acting on the articular segments was carried out and determination of strain and deformations suffering the stump zones and of the ankle joint by finite elements method. Results: the significant changes in the dynamics of ankle-knee-hip articulation segments are present as the result of gait asymmetry of the prosthetic limb and the healthy one. This imbalance may be one of the leading causes of degenerative diseases of hip observed in this type of patient. Conclusions: the analysis of functional qualities of trans-femoral prosthetic devices only is possible by means of the integration of cinematic methods of gait characterization, dynamic methods establishing the possibility to replicate to the activity of healthy limb. Using this study also it was possible the mechanical resistance study linking all results to the appearance of diseases of intact limb as well as the residual one

Resected femoral anthropometry for design of the femoral component of the total knee prosthesis in a Korean population / 대한해부학회지

We measured the mediolateral (ML) and anteroposterior (AP) length, height and widths of the anterior, posterior and inferior section of the resected distal femurs using three dimensional computer tomographic measurements in 200 knees from 100 cadavers. We also calculated the aspect ratio (ML/AP) and compared the measured parameters with that of six conventionally used total knee femoral prostheses. We found that the average ML (70.2+/-5.5 mm) and AP (53.9+/-3.8 mm) dimensions from our study were lower than those reported from Western populations. The aspect ratio showed a progressive decline with an increasing antero-posterior dimension. All of the compared designs showed undersizing for the mediolateral dimension distally and for the widths of the resected medial and lateral posterior femoral condyles. But some of the compared designs showed oversizing for the height of the resected medial and lateral posterior femoral condyles. This study provides guidelines for designing a suitable femoral component for total knee prostheses that fit Asian populations.

Caracterização de uma haste femoral de Ti-6Al-4V não cimentada / Characterization of a cementless Ti-6Al-4V femoral stem

O objetivo deste estudo foi determinar a viabilidade de produção de uma prótese femoral de titânio garantindo a qualidade da matéria prima e as características das superfícies. Um protótipo foi criado pelo Método de Elementos Finitos em AutoCad® 2000. A simulação dos esforços demonstrou uma tensão de von Mises 8,1 vezes menor que a tensão crítica para escoamento do material. Na determinação dos constituintes metálicos, obteve-se: Fe  =   0,06%, Al  = 6,20%, V  = 3,57%, O  = 0,115%, N  = 0,003%, H  = 0,010%, e ausência de metais pesados. As propriedades elasto-plásticas da amostra tiveram valor médio de dureza de 4,45 (3,92 a 4,79) GPa e o módulo de elasticidade variou de 112,12 a 140,77  GPa (média  = 134,33). O coeficiente de rugosidade médio (DP) no cone foi de 0,60  (0,03) μm; na região jateada de 12,2 (0,8) μm e na ponta de 0,41 (0,01) μm. Nos ensaios de fadiga e de corrosão não foram observadas alterações. A análisegranulométrica do pó do material depositado demonstrou predominância de partículas médias (75  μm a 180  μm; 84%). A espessura da camada do material depositado apresentou valor médio de 52,7  μm (0 a 318  μm), porosidade média de 16% (variandode 3% a 41%), poros de diâmetro médio de 88,5  μm e profundidade média de 28,2  μm. A tensão (força por unidade de área) de adesão da camada porosa depositada revelou valoresde 15 a 17  MPa. Em conclusão, os resultados dos testes e ensaios técnicos estão dentro das normas internacionalmente recomendadas e padronizadas para implantes metálicos em titânio estando essa prótese de acordo com os padrões internacionaisde qualidade e segurança.

The objective of this work was to study the feasibility of manufacturing a cementless femoral prosthesis in Brazil, in compliance with internationalstandards of quality assurance. A virtual prototype by the Finite Elements Model in AutoCad® 2000 was assessed and demonstrated a von Mises tension 8.1 below the deformation point. In determining the metallic components, the percentages were Fe  = 0.06%, Al  = 6.20%, V  = 3.57%, O  = 0.115%, N  = 0.003%, H  = 0.010% without any contamination due to heavy metals. The elasto-plastic properties showed an average value of hardness of 4.45 (3.92 to 4.79) GPa and elasticity module varied from 112.12 to 140.77  GPa (mean  = 134.33). The average coefficient of roughness (SD) in the cone was 0.60 (0.03) μm, 12.2 (0.8) μm in the plasma spray coating region, and 0.41 (0.01) μm in the tip. In the assays for fatigue and corrosion no changes were observed. The grain size analysis of the deposited material dust demonstrated predominantly (84%) medium size particles (75  μm to 180  μm). The thickness of the deposited material layer presented average value of 52.7  μm (0 to 318  μm), average porosity of 16% (varying from 3% to 41%) and pores of average diameterof 88.5  μm and average depth of 28.2  μm. The force of adhesion of the deposited porous layer showed values between 15  and  17  MPa. Results were in accordance with the norms and tests internationally recommended and standardized for metallic implants in titanium alloy and  the femoral prosthesis manufactured with national technology was in accordance with international standards of design, quality and safeness.

Biomechanical study of Ni-Ti shape memory alloy stemless femoral prosthesis / 中国矫形外科杂志

[Objective]To evaluate the biomechanical features of Ni-Ti shape memory alloy stemless femoral prosthesis.[Method]Using CT(computer tomography) scanning photographs of adult femur,three-dimensional model of the femur was built by CAD(computer aided design) software.Based on the the structure of femoral model,shape memory alloy stemless femoral prosthesis was designed.Three-dimensional finite element model was created for the normal femur,Ni-Ti shape memory alloy stemless femoral prosthesis,and traditional stemmed hip prosthesis.Under static loads and walking loads,the Von Mises stress distributions of each model were analyzed and compared.[Result]The stress distribution of shape memory alloy stemless femoral prosthesis was not obviously different from normal femur,stemless femoral prosthesis's proximal femoral stress was close to that of normal femoral model but significantly higher than traditional stemmed hip prosthesis.Von Mises stress of memory alloy claws was distributed evenly,and the Max was only 13.23Mpa,there was no stress concentration.[Conclusion](1) Ni-Ti shape memory alloy stemless femoral prosthesis has great biomechanical properties,may reduce the stress-shieding effect of the proximal femur.The fixed method that use memory alloy claws can make prosthesis fixed firmly to the bone and reduce stress concentration.

Application of modular femoral prosthesis in total hip revision surgery for Paprosky type Ⅲ bone defect of proximal femur / 中国矫形外科杂志

[Objective]To report the mid-term results and main points of modular femoral prosthesis in total hip revision surgery for Paprosky type Ⅲ bone defect of the proximal femur.[Method]Nine cases of Paprosky type Ⅲ bone defect of the proximal femur were treated with modular femoral prosthesis MP and ZMR from May 2003 to October 2006.There were 5 males and 4 females with the age range of 39-65 years(mean age 57 years).All the patients were followed up for 8-34 months(mean 19 months).Causes for revision included loosening and osteolysis of primary cemented prosthesis in 7,and coral face prosthesis sterile loosening in 2.The shortest time from the last operation to the revision was 4 years,and the longest was 12 years.There were 5 of type ⅢA and 4 of type ⅢB according to the Paprosky bone defect classification.[Result]The Harris score was 35 points(28-54) before operation and 85(70-90) after operation.Seven patients walked without the help of crutches,one had a mild pain in the thigh and a leg crispation of 2.5 centimeter,and the other having a medium pain in the thigh limping with a crutch.No significant loosening,infection or osteolysis of distal femur was found.One prosthesis sinking 12 mm in 1 case.[Conclusion]Total hip revision surgery for Paprosky type Ⅲ femoral bone defect using modular femoral prosthesis has optimal mid-term results.It offers stabilization both in the initial and late stages.Due to the separation of prosthetic stem from the proximal prosthesis,the implantation is easy to fix.Modular femoral prosthesis,which is benificial to control offset,anteversion angle,and limb length makes the total hip revision surgery simpler and safer.

Impaction bone grafting in THA revision with freeze-dried allograft and anatomic cemented femoral stem / 中国矫形外科杂志

[Objective]To explore the efficacy and result of femoral component revision by using impaction bone grafting technique with anatomic cemented stem and freeze-dried allograft.[Method]Anatomic cemented stem combined with freeze-dried allograft were used in IBG for 49 cases of femoral revisions from Jan,2001 to Dec 2005.36 cases(73%)of which had severe bone loss(Paprosky grades ⅢB and Ⅳ).The mean follow-up time was 35.3 months(26~52 months).Harris Hip Score System and radiography were used to evaluate the clinical results.[Result]The mean Harris Hip Score was improved from 44.6 points preoperatively to 88.3 points at final evaluation.Good and excellent scores were about 89.8%.No major femoral stem subsidence was found in our patients.There were one case of dislocation(2%),one case of deep infection(2%)and 3 cases of femoral fractures during operations(6.1%),which were not related to the selection of femoral component and the type of allograft.[Conclusion]The impaction bone grafting technique by using freeze-dried allograft and the anatomic cemented femoral prosthesis for femoral revision was feasible and the short and mid-term result was good.Longer follow-up was needed to evaluate the long term result.

Strain distribution in the proximal human femur after insertion of CF/PEEK femoral stems / 中国矫形外科杂志

[Objective]To develop a new femoral prosthesis that can integrate with femur compactly and increase proximal femoral stress transfer,and further improves the long-term curative effect of total hip arthroplasty.[Method]Five pairs of human cadaver femora were divided equally into two groups one of which received a cobalt-chrome molybdemum alloy(CoCrMo) implant and the other a carbon fiber reinforced polyetheretherketone composite(CF/PEEK) implant.Six strain-gauge rosettes were attached to the external surface of each implant and proximal femora.The loading conditions simulated single-limb stance and the strains were recorded first with the femora intact and then with the femoral components of two different designs implant inserted.[Result]After the insertion of a femoral component,the normal pattern of a progressive proximal-to-distal increase in strains was similar to that in the intact femur and the strain was maximum near the tip of the prosthesis.On the medial and lateral aspects of the proximal femur,thc strains were reduced after implantation of both types of implant.The pattern and magnitude of the strains,however,were closer to those in the intact femur after insertion of the CF/PEEK stem than that of CoCrMo stem.[Conclusion]Our findings suggest that the CF/PEEK stem can provide immediate postoperative stability,better proximal loading transfer in the metaphysis and further reduce stress shielding,bone resorption and osteanabrosis,thus prevent the implant from failuri.

Study on intelligent trans-femoral prosthesis with terrain identification / 中国康复理论与实践

@#ObjectiveTo investigate the necessary of letting the intelligent knee joint be adaptive to the road terrain and the key technology of knee moment control method. MethodsBased on data from gait analysis and the dynamic model of lower limb,the knee moments while people walking on the path of different terrain were obtained. Terrain identification method was based on the features of electromyography(EMG) signals of the thigh,and the EMG of some muscles was detected. The methods were applied to an intelligent trans-femoral prosthesis developed for tests in the laboratory.ResultsConsiderable variation of the knee moments appeared when people walking on the path of different terrain,as well as that of the features of EMG of some muscles.ConclusionIt is necessary to make the intelligent knee joint be adaptive to the road terrain,and it is possible to be achieved with satisfied motion of the leg and the trajectory of ankle joint by the intelligent transfemoral prosthesis being studied which can identify the features of EMG signals.

The initial stability of CF/PEEK femoral stem after total hip replacement / 中华创伤骨科杂志

Objective To explore the initial stability of a carbon fiber reinforced polyetheretherketone composite (CF/PEEK) stem in human femurs after total hip replacement. Methods 8 pairs of human cadaveric femurs were used to test the CF/PEEK prosthesis versus a conventional cementless stem of cobalt-chrome molybdemum alloy(CoCrMo). The bone-femoral prosthesis interface motion was measured in vitro using displacement transducers. Combined axial and torsional loads and simulated single-leg stance loading were applied. Subsidence, rotation and interface motion were measured with load cycles up to 1 000 N. Results The extent of the micro-motion in the proximal femoral region was larger than that in the distal femoral region. The CF/PEEK composite prosthesis showed less dynamic micro-motion in the proximal region compared with the CoCrMo alloy prosthesis stem, with the average difference being 42%. The extent of the distal micro-motion in the 2 groups was small but the difference was significant (P

Application of modular femoral prosthesis in total hip revision surgery for bone defects / 中华创伤杂志

Objective To discuss the midterm results of modular femoral prosthesis in total hip revision surgery for bone defects.Methods From December 2001 to June 2006,by using Link-MP modular femoral prosthesis for muhiple reasons(48 with asepsis loosening,seven with infections using two-stage revision procedure,one with fracture of proximal femur and one with periprosthetie fracture), total hip revision surgery was carried out in 56 eases including 24 males and 32 females with age range of 38-77 years(mean age 58.8years).Causes for revision included sterile prothesis loosening in 48 cases, infection of hip prosthesis in seven and peripheral fracture of femoral stem fracture prosthesis in one.Re- vision for infected femur was all at stageⅡ.Of 56 cases with femoral stem prosthesis loosening,30 had loosening of primary cemented prosthesis and 26 of uncemented prosthesis.According to the Mallory bone defect classification,five eases were with typeⅡbone defect,21 with typeⅢA,28 with typeⅢB and two with typeⅢC.Bone grafting was performed in 12 cases and wire or cable cerelage in 28.Fracture of great trochanter was found in two cases,fracture of femoral stem in three and perforation of femoral stem in one.Results A total of 52 eases half year after operation were followed up for mean 31.78 months (8-56 months).No migration of distal femoral stem was found in all eases except for one ease had 1.5 cm subsidence of proximal femoral stem.The Harris hip score was preoperative 46 scores(21-52)and post- operative 89(79-94).There found no significant limb discrepancy,thigh pain or dislocation.Conclu- sions Total hip revision surgery for femoral bone defect using modular femoral prosthesis has optimal midterm result especially in its advantages of regulating limb length,offset,anteversion,which can help us match the proximal femur with distal femur and achieve initial and long-term stability.

The early results of total hip replacement with a proximally hydroxyapatite-coated femoral component / 中华创伤骨科杂志

Objective To summarize the early results of total hip replacement with a proximally hydroxyapatite-coated femoral component. Methods From February 2000 to October 2003, 65 cases (70 hips) underwent uncemented total hip replacement with a proximally hydroxyapatite-coated femoral component (U2, United Orthopedic Corporation, Taiwan, China). The diagnosis included femoral neck fractures in 30 cases, osteoarthritis in 15 cases, avascular necrosis of the femoral head in 9 cases, loosening of artificial femoral head in 8 cases, rheumatoid arthritis in 2 cases, and arthrodesis in 1 case. Clinical and radiographic evaluations were performed at 1 week, 3 and 6 months postoperatively, and yearly afterwards. Bone mineral density (BMD) of the proximal femur was measured with dual-energy X-ray Absorptiometry (DEXA) for 44 cases. Results Postoperative X-ray films showed that the initial fixation was excellent or good in all the stems. The follow-ups averaged 3 years (2 to 5.5 years). The mean preoperative Harris hip score was 32 (25 to 52) points, which were improved to 96 points at the latest follow-ups. There was no reported incidence of thigh pain at any time throughout our study. And no case needed revision. By the measurements on the X-ray films taken within 1 year postoperatively, 7 of the 70 stems had subsidence of less than 1.5 mm. No hip experienced extensive proximal end osteolysis, intramedullary osteolysis, or loosening. DEXA showed that the BMD values decreased after operation, and then returned rapidly to the normal or near normal ones 3 to 6 months after operation, especially in zones Ⅱand Ⅵwhere the increase was even more significant than at the control side. All the stems were radiographically stable with evidence of osseous ingrowth typically seen in HA-coated zones, according to the criteria proposed by Engh et al. Conclusions Since HA-coating on femoral implants can enhance the initial fixation of implants, accelerate bone ingrowth and osseous fixation of the femoral component, and seal the interface between the implant and bone to prevent ingress of polyethylene particles, it is helpful in improving clinical results of the cementless total hip replacement.

A Failure of the Locking System of the Acetabular Assembly in a Total Hip Replacement

In this study, the author presents the case of one patient who had a Harris-Galante total hip replacement for pigmented villonodular synovitis of the left hip joint, the locking system failed and separation of the polyethylene liner from the acetabular metal shell occurred while the closed reduction of the posterior dislocation of the femoral prosthesis was performed. This study indicates that the design of the acetabular assembly should be modified. The gap between the rims of metal shell and polyethylene liner should be reduced or eliminated.