酒精灭活骨复合人工假体治疗股骨远端骨巨细胞瘤及有限元分析

目的 探讨酒精灭活骨复合人工假体治疗股骨远端骨巨细胞瘤的临床疗效.方法 2007年1月至2008年10月应用酒精灭活骨复合旋转铰链膝关节治疗股骨远端骨巨细胞瘤5例,男3例、女2例;年龄22～40岁,平均29.6岁.3例为术后复发病例,2例伴病理性骨折.均为CampanacciⅢ级.选择1名18岁成年男性健康志愿者,利用...     

髓腔改变对股骨近端假体-骨界面应力的影响

目的 建立股骨近端假体-骨界面应力有限元分析模型.并对中国成年人股骨近端正常受力、翻修过程中扩髓条件下进行静态有限元分析.方法 运用逆向工程与有限元的理论.对CT图像采用了滤波、边界提取、二值化等方法进行处理,所得数据用CAD软件经过曲线重构、曲面重构、实体重构,加工出股骨应力模型.将不同载荷施加与假体-骨界面,改变股骨骨皮质的厚度、假体长度等参数,进行静态模拟应力分析.结果 建立起以国人股骨为基础的有效的假体-骨界面应力分布规律三维有限元模型.股骨的受力主要集中在小转子和大转子之间的股骨距分布区域,并且随着载荷的增加而递增;假体增粗至原来的120%时,股骨最大应力已经接近极限应力值.结论 构建的解剖型股骨假体-骨界面三维有限元模型,几何相似性好.模拟应力分析结果提示接受关节置换的患者应该尽量避免登山等接近加载量极限的活动;对于髓腔骨缺损严重的翻修患者提倡应用骨移植材料.谨慎采用增粗假体固定.     

Anatomy of the epicondyles of the distal femur: MRI analysis of normal knees

Knowledge of precise anatomic landmarks and relationships of the distal femur can be helpful in knee surgery, especially primary and revision total knee arthroplasty. We analyzed 104 consecutive routine knee magnetic resonance imaging studies to define useful landmarks and relationships. The epicondyles are described, and the relationship of the epicondyles to the joint line is defined in multiple planes. Some significant gender differences were noted. The distance from the epicondyles to the joint line correlates with the transepicondylar width of the distal femur. This information can be helpful in determining appropriate joint line position intraoperatively. The posterior condylar angle averaged 3.11 degrees for all patients, and a tendency for the posterior condylar angle to increase with age was noted, but further study of this tendency is needed.     

Prosthetic replacement of the distal femur for primary bone tumours

Over a 16-year period, 135 custom-made distal femoral prostheses, based on a fully constrained Stanmore-type knee replacement, were used in the treatment of primary malignant or aggressive benign tumours. Survivorship analysis showed a cumulative success rate of 72% at five years and 64% at seven years. Intact prostheses in 91% of the surviving patients gave good or excellent functional results. Deep infection was the major complication, occurring in 6.8% of cases; clinical aseptic loosening occurred in 6.0%. Revision surgery was carried out for loosening and infection, and the early results are encouraging. We conclude that prosthetic replacement of the distal femur can meet the objectives of limb salvage surgery.     

In vivo estimation of bone stiffness at the distal femur and proximal tibia using ultra-high-field 7-Tesla magnetic resonance imaging and micro-finite element analysis

The goal of this study was to demonstrate the feasibility of using 7-Tesla (7T) magnetic resonance imaging (MRI) and micro-finite element analysis (μFEA) to evaluate mechanical and structural properties of whole, cortical, and trabecular bone at the distal femur and proximal tibia in vivo. 14 healthy subjects were recruited (age 40.7 ± 15.7 years). The right knee was scanned on a 7T MRI scanner using a 28 channel-receive knee coil and a three-dimensional fast low-angle shot sequence (TR/TE 20 ms/5.02 ms, 0.234 mm × 0.234 mm × 1 mm, 80 axial images, 7 min 9 s). Bone was analyzed at the distal femoral metaphysis, femoral condyles, and tibial plateau. Whole, cortical, and trabecular bone stiffness was computed using μFEA. Bone volume fraction (BVF), bone areas, and cortical thickness were measured. Trabecular bone stiffness (933.7 ± 433.3 MPa) was greater than cortical bone stiffness (216 ± 152 MPa) at all three locations (P < 0.05). Across locations, there were no differences in bone stiffness (whole, cortical, or trabecular). Whole, cortical, and trabecular bone stiffness correlated with BVF (R ≥ 0.69, P < 0.05) and inversely correlated with corresponding whole, cortical, and trabecular areas (R ≤ −0.54, P < 0.05), but not with cortical thickness (R < −0.11, P > 0.05). Whole, cortical, and trabecular stiffness correlated with body mass index (R ≥ 0.62, P < 0.05). In conclusion, at the distal femur and proximal tibia, trabecular bone contributes 66–74% of whole bone stiffness. 7T MRI and μFEA may be used as a method to provide insight into how structural properties of cortical or trabecular bone affect bone mechanical competence in vivo.     

Segmental amputation for recurrent malignant bone tumors of the distal femur

We describe an alternative method for lengthening a short femoral stump after wide amputation of a malignant bone tumor of the distal femur in two patients. The method consists of two procedures during the operation. The first procedure is amputation of the affected cylindrical segment of the involved limb. The second procedure is elongation of the amputation stump using the tumor-free segment of the ipsilateral lower leg as a free composite osseous myocutaneous graft. Both patients had good function and were satisfied with the results with no complications or tumor recurrence 4 years postoperatively. We think the segmental amputation is a good procedure that results in a longer functional stump in patients who have above-knee amputation.     

Gender differences in trabecular bone architecture of the distal radius assessed with magnetic resonance imaging and implications for mechanical competence

High-resolution magnetic resonance imaging (hrMRI) has recently made it possible to evaluate trabecular bone structure in vivo. Despite obvious gender differences in fracture incidence at the distal radius, little is known about gender differences in trabecular bone microarchitecture and its relationship to the structural strength of the forearm. The aim of this study was to determine trabecular bone structure in the distal radius of elderly women and men and its correlation with failure loads of the distal radius as determined in a fall configuration. Specifically, we tested the hypotheses that structural indices differ between women and men and that they offer information that is independent from BMD for predicting structural strength. Intact right arms were obtained from 73 formalin-fixed cadavers (age 80±11 years, 43 women, 30 men). Trabecular structural indices (apparent bone volume fraction [app. BV/TV], trabecular number [app. Tb.N], trabecular separation [app. Tb.Sp], trabecular thickness [app. Tb.Th] and fractal dimension [Frac.Dim]) were assessed in the distal metaphysis, using hrMRI with 156 µm in-plane resolution and proprietary digital image analysis, while BMD was measured with dual X-ray absorptiometry (DXA). Women displayed significantly lower BMD (–29.8%, p <0.001), app. BV/TV (–8.2%, p <0.05) and app. Tb.Th (–10.2%, p <0.001) than men, whereas app. Tb.N, app. Tb.Sp. and fractal dimension did not differ significantly. Structural parameters differed between normal and osteopenic women (BV/TV: –11%, p <0.01; Tb.Th: –8%, p <0.001) and between normal and osteoporotic women BV/TV: –21%, p <0.001; Tb.Th: –16%, p <0.001). App. BV/TV, app. Tb.Th and fractal dimension provided information independent from BMD in the prediction of radial failure loads in multiple regression models. These findings imply that it should be of clinical interest to monitor both bone mass and trabecular microstructure for predicting osteoporotic fracture risk.     

Assessment of trabecular and cortical architecture and mechanical competence of bone by high-resolution peripheral computed tomography: comparison with transiliac bone biopsy

Summary

We compared microarchitecture and mechanical competence parameters measured by high-resolution peripheral quantitative computed tomography (HR-pQCT) and finite-element analysis of radius and tibia to those measured by histomorphometry, micro-CT, and finite-element analysis of transiliac bone biopsies. Correlations were weak to moderate between parameters measured on biopsies and scans.

Introduction

HR-pQCT is a new imaging technique that assesses trabecular and cortical bone microarchitecture of the radius and tibia in vivo. The purpose of this study was to determine the extent to which microarchitectural variables measured by HR-pQCT reflect those measured by the “gold standard,” transiliac bone biopsy.

Methods

HR-pQCT scans (Xtreme CT, Scanco Medical AG) and iliac crest bone biopsies were performed in 54 subjects (aged 39?±?10 years). Biopsies were analyzed by 2D quantitative histomorphometry and 3D microcomputed tomography (µCT). Apparent Young’s modulus, an estimate of mechanical competence or strength, was determined by micro-finite-element analysis (µFE) of biopsy µCT and HR-pQCT images.

Results

The strongest correlations observed were between trabecular parameters (bone volume fraction, number, separation) measured by µCT of biopsies and HR-pQCT of the radius (R 0.365–0.522; P?<?0.01). Cortical width of biopsies correlated with cortical thickness by HR-pQCT, but only at the tibia (R?=?0.360, P?<?0.01). Apparent Young’s modulus calculated by µFE of biopsies correlated with that calculated for both radius (R?=?0.442; P?<?0.001) and tibia (R?=?0.380; P?<?0.001) HR-pQCT scans.

Conclusions

The associations between peripheral (HR-pQCT) and axial (transiliac biopsy) measures of microarchitecture and estimated mechanical competence are significant but modest.     

Calculated stress-shielding in the distal femur after total knee replacement corresponds to the reported location of bone loss

This study sought to determine the similarities between features of calculated stress-shielding and observed bone loss in the distal femur after total knee replacement. Stress-shielding was determined by comparing the magnitudes and distributions of strain energy density, calculated using three-dimensional finite element models of the intact bone, the bone after total knee replacement with bonding assumed at all prosthesis-bone interfaces, and the bone after total knee replacement with bonding assumed only at the distal interface. The loading condition simulated static lifting with the knee flexed at 45°, producing tibiofemoral and patellofemoral joint reactions of 900 and 450 N, respectively. The maximum magnitudes of strain energy density calculated using the total knee replacement models were less than 15% of the corresponding magnitudes from the intact bone model. The greatest difference was found to occur at the anterior distal corner of the femur, suggesting this location as the one most vulnerable to stress-shielding. Clinically observed bone loss after total knee replacement frequently occurs at this location. At the anterior distal corner, the calculated magnitudes for the two total knee replacement models were similar, suggesting that stress-shielding at this location was not reduced by limiting fixation only to the distal interface. Although the study corresponded to one loading condition and one geometry of the total knee replacement femoral component with the inherent limitations of model calculations, the results suggest a possible scenario for stress-shielding.     

Hardness, an indicator of the mechanical competence of cancellous bone

Hardness and calcium content in compact bone are strongly related. Variation in Young's modulus is produced mainly by variations in mineralisation. Therefore, there should be a relationship between hardness and Young's modulus. We demonstrate this. The calcium content of cancellous bone and adjacent compact bone in several species shows little difference, the cancellous bone having approximately 10% less calcium. The hardness of cancellous bone in Bos is approximately 12% less than that of adjacent compact bone, and the calcium is approximately 2% less. These lines of evidence make it unlikely that the Young modulus of cancellous bone material is much different from that of compact bone. Similar evidence suggests that the yield stress of cancellous bone is similar to that of adjacent compact bone.     

股骨远端肿瘤性缺损两种不同内固定方法的有限元分析

目的比较股骨远端骨肿瘤手术中两种不同内固定重建方法的生物力学差别,为临床选择更理想的内固定方法提供理论依据。方法模拟股骨远端骨肿瘤瘤段切除病例,分别采用锁定钢板和交锁髓内钉内固定方法进行重建,建立该模型三维有限元模型,导入ABAQUS软件系统进行有限元分析,当给予平行于股骨长轴轴向压缩700N情况下,比较锁定钢板和交锁髓内钉的位移和应力分布情况。结果两组模型应力均未达到屈服应力,锁定钢板的应力分布比较均匀,接近正常值,最大应力为50 Mpa,股骨头最大位移为2.9 mm。髓内钉的最大应力为85 Mpa,股骨头最大位移为3.8 mm。结论锁定钢板和交锁髓内钉都能用于股骨远端骨肿瘤切除后的重建手术,锁定钢板比交锁髓内钉更稳定,刚度更大。     

Clinical cone beam computed tomography compared to high-resolution peripheral computed tomography in the assessment of distal radius bone

Summary

Clinical cone beam computed tomography (CBCT) was compared to high-resolution peripheral quantitative computed tomography (HR-pQCT) for the assessment of ex vivo radii. Strong correlations were found for geometry, volumetric density, and trabecular structure. Using CBCT, bone architecture assessment was feasible but compared to HR-pQCT, trabecular parameters were overestimated whereas cortical ones were underestimated.

Introduction

HR-pQCT is the most widely used technique to assess bone microarchitecture in vivo. Yet, this technology has been only applicable at peripheral sites, in only few research centers. Clinical CBCT is more widely available but quantitative assessment of the bone structure is usually not performed. We aimed to compare the assessment of bone structure with CBCT (NewTom 5G, QR, Verona, Italy) and HR-pQCT (XtremeCT, Scanco Medical AG, Brüttisellen, Switzerland).

Methods

Twenty-four distal radius specimens were scanned with these two devices with a reconstructed voxel size of 75 μm for Newtom 5G and 82 μm for XtremeCT, respectively. A rescaling-registration scheme was used to define the common volume of interest. Cortical and trabecular compartments were separated using a semiautomated double contouring method. Density and microstructure were assessed with the HR-pQCT software on both modality images.

Results

Strong correlations were found for geometry parameters (r?=?0.98–0.99), volumetric density (r?=?0.91–0.99), and trabecular structure (r?=?0.94–0.99), all p?<?0.001. Correlations were lower for cortical microstructure (r?=?0.80–0.89), p?<?0.001. However, absolute differences were observed between modalities for all parameters, with an overestimation of the trabecular structure (trabecular number, 1.62?±?0.37 vs. 1.47?±?0.36 mm^?1) and an underestimation of the cortical microstructure (cortical porosity, 3.3?±?1.3 vs. 4.4?±?1.4 %) assessed on CBCT images compared to HR-pQCT images.

Conclusions

Clinical CBCT devices are able to analyze large portions of distal bones with good spatial resolution and limited irradiation. However, compared to dedicated HR-pQCT, the assessment of microarchitecture by NewTom 5G dental CBCT showed some discrepancies, for density measurements mainly. Further technical developments are required to reach optimal assessment of bone characteristics.

     

Fixation of experimental osteotomies of the distal femur in rabbits with bone cement and cyanoacrylate

Summary A distal femoral osteotomy was fixed with liquid cyanoacrylate and bone cement in 25 rabbits. Follow-up was done at 1, 3, 6, 12, and 24 weeks. The distal portion of each femur was removed, fixed in alcohol, embedded in methylmethacrylate, sawed to 80 m thickness for OTC-fluorescence study and microradiography, and cut to 5-m sections for histological analysis. Radiological and careful microscopic (OTC labeling, microradiographic, and histological) studies showed healing of the osteotomies during the first 6 weeks after operation. However, at 12 and 24 weeks' follow-up only four of ten osteotomies had healed. According to these observations it is obvious that fixation of an osteotomy of the cancellous bone with bone cement and cyanoacrylate does not provide sufficient stability for successful healing.

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Zusammenfassung Die distalen Femurosteotomien von 25 Kaninchen wurden mit Zyanoakrylat und Knochenzement fixiert. Die Nachuntersuchungen fanden nach 1, 3, 6, 12 and 24 Wochen statt. Der distale Teil von jedem Oberschenkelknochen wurde entnommen, in Alkohol fixiert, in Methylmethacrylat gegossen und für die histologischen Studien auf 5 m Dicke geschnitten und für die OTC-Studien und Microradiographie auf 80 m gesägt. Die radiologischen und genauen mikroskopischen (OTC, Mikroradiographie, Histologic) Untersuchungen zeigten, daß die Osteotomien während den ersten sechs Wochen heilten. Später dagegen waren die Resultate ungenügend, denn nur 4 von 10 Osteotomien waren nach 12 and 24 Wochen geheilt. Auf Grund dieser Resultate ist zu schlieBen, daB eine genügend stabile Osteotomie des spongiösen Knochens durch Fixation mit Knochenzement and Zyanoakrylat nicht erreicht und somit die Heilung gestört wurde.

     

Regional analysis of bone mineral density in the distal femur and proximal tibia using peripheral quantitative computed tomography in the ratin vivo

The use of peripheral quantitative computed tomography (pQCT) was investigated for the measurement of volumetric bone mineral density (BMD) in mg·cm⁻³. Two studies were undertaken. In the first study, the precision of pQCTin vivo andex vivo was tested at 14 weeks postovariectomy (OVX). In the second study, the efficacy of a standard antiresorptive treatment, 17β-estradiol (E2), was tested 6 weeks post-OVX. The precision for total (compact plus trabecular) BMD was 1.3–1.9%, and that for trabecular BMD was 2.4–2.7%. There was excellent agreement between trabecular BMD measurementsin vivo andex vivo (r=0.91). Significant reductions in trabecular BMD were observedin vivo at 14 and 6 weeks following ovariectomy in the femur, in each study. The loss of trabecular BMD depended on slice location, and varied from 0 to 22% at 6 weeks, and from 0 to 26% at 14 weeks (P<0.001, at the affected locations). The antiresorptive effect of treatment was demonstrated in the 6-week study: there was no significant difference in BMD between sham-operated and E2-treated OVX rats.     

Long bone florid reactive periostitis ossificans: a case in the distal femur mimicking osteosarcoma

Florid reactive periostitis ossificans is a well-known benign lesion classically described in hands and feet which histopathological features can lead to a misdiagnosis of osteosarcoma. To the best of our knowledge, there is only one previous report of this lesion in a long bone. In this study we report a case of florid reactive periostitis ossificans located in the distal metaphysis of the left femur that histologically mimicked an osteosarcoma and discuss the differential diagnosis between these two entities to warn about a diagnostic pitfall.     

Feasibility of in vivo structural analysis of high-resolution magnetic resonance images of the proximal femur

Previously, high resolution MRI to assess bone structure of deep-seated regions of the skeleton such as the proximal femur was substantially limited by signal-to-noise ratio (SNR). With the advent of new optimized pulse sequences in MRI at 1.5 T and 3 T, it may now be possible to depict and quantify the trabecular microarchitecture in the proximal femur. The purpose of this study was to investigate the feasibility of assessing trabecular microstructure of the human proximal femur in vivo with MR imaging at 1.5 T and 3 T. MR images of six young, healthy male and female subjects were acquired using standard clinical 1.5-T and high-field 3-T whole-body MR scanners. Using a T2/T1-weighted 3D FIESTA sequence (and a 3D FIESTA-C sequence at 3 T to avoid susceptibility artifacts) a resolution of 0.234 × 0.234 × 1.5 mm³ was achieved in vivo. Structural parameters analogous to standard bone histomorphometry were determined in femoral head and trochanter regions of interest. Bone mineral density (BMD) measurements were also obtained using dual-energy X-ray absorptiometry (DXA) for the femoral trochanter in the same subjects. The bone structure of the proximal femur is substantially better depicted at 3 T than at 1.5 T. Correlation between the structural parameters obtained at both field strengths was up to R =0.86 for both the femoral head and the trochanteric region. However, the resolution of the images limits the application of 3D structural analysis, making the assessment more akin to 2D textural measures, which may be correlated to histomorphometric but are not identical measures. This feasibility study establishes the potential of MRI as a means of imaging proximal femur structure, and improvements in technique and resolution enhancements are warranted.     

Current concepts in fractures of the distal femur

This paper describes current treatment strategies of distal femoral fractures as well as their evidence based rationale. The treatment of distal femoral fractures has improved with the evolution of plating and nailing technologies. The commonly selected surgical approaches are outlined and surgical treatment techniques including both internal and external fixation are discussed.     

Gender differences in the anatomy of the distal femur

Recently, gender-specific designs of total knee replacement have been developed to accommodate anatomical differences between males and females. We examined a group of male and female distal femora matched for age and height, to determine if there was a difference in the aspect ratio (mediolateral distance versus anteroposterior distance) and the height of the anterior flange between the genders. The Hamann-Todd Collection provided 1207 skeletally mature cadaver femora. The femoral length, the anteroposterior height, height of the lateral and medial flanges and the mediolateral width were measured in all the specimens. The mechanical axis of the femur, the cut articular width and the aspect ratio were assessed. Statistical analysis of the effect of gender upon the aspect ratio and the lateral and medial flanges was undertaken, controlling for age, height and race. The mean aspect ratio of male femora was 1.21 (SD 0.07) and of female femora it was 1.16 (SD 0.06) (p < 0.001). There was no significant difference between male and female specimens in the mean size of the lateral flange (6.57 mm (SD 2.57) and 7.02 mm (SD 2.36), respectively; p = 0.099) or of the medial flange (3.03 mm (SD 2.47) and 3.56 mm (SD 2.32), respectively; p = 0.67). Future work in the design of knee prostheses should take into account the overall variability of the anatomy of the distal femur.     

Detection of bone fragments in pulmonary vessels following extracorporeal shock wave application to the distal femur in an in-vivo animal model

AIM: In urology, single cases of lethal pulmonary embolism following extracorporeal shock wave application to renal concrements have been reported. Therefore, lungs of rabbits were histopathologically investigated following extracorporeal shock wave application to the femur. METHOD: In 8 mature Chinchilla-Bastard rabbits, shock wave application to one distal femur was performed with energy flux density of 0.9 mJ/mm2. In another 6 rabbits, sham-treatment (0 mJ/mm2) to one distal femur was performed. 6 weeks later, the animals were sacrificed and their lungs were blindly investigated by an independent pathologist. RESULTS: In 7 out of the 8 treated animals (0.9 mJ/mm2) but in none of the sham-treated controls, patchy discolorations of the surface of the lung were observed. Furthermore, in 6 out of the 8 treated animals but in none of the sham-treated controls, bony fragments with signs of resorption were observed in lung vessels. CONCLUSION: Application of extracorporeal shock waves with energy flux densities higher than 0.9 mJ/mm2 has been recommended in the literature for the treatment of aseptic non-unions. In this procedure, the possibility of the occurrence of bone fragments in the lung with the potential risk of pulmonary embolism should be regarded.