EM segmentation of the distal femur and proximal tibia: a high-throughput approach to anatomic surface generation

Fully automated segmentation of computed tomography (CT) images remains a challenge for musculoskeletal researchers. The surfaces generated from image segmentations are valuable for surgical evaluation and planning. Previously, we demonstrated the expectation maximization (EM) algorithm as a semi-automated method of bone segmentation from CT images. In this work, we improve upon the methodology of probability map generation and demonstrate extended applicability of EM-based segmentation to the distal femur and proximal tibia using 72 CT image sets. We also compare the resulting EM segmentations to manual tracings using overlap metrics and time. In the case of the distal femur, the resulting quality metrics had mean values of 0.91 and 0.95 for the Jaccard and Dice metrics, respectively. For the proximal tibia, the Jaccard and Dice metrics were 0.90 and 0.95, respectively. The EM segmentation method was 8 times faster than the average manual segmentation and required less than 4% of the human rater time. Overall, the EM algorithm offers reliable image segmentations with an increased efficiency in comparison to manual segmentation techniques.     

Coronal subluxation of the proximal tibia relative to the distal femur after opening wedge high tibial osteotomy

Background

The coronal subluxation of the proximal tibia relative to the distal femur is a common radiological finding in patients with knee osteoarthritis. The purpose was to evaluate whether the coronal subluxation was corrected after opening wedge high tibial osteotomy (OWHTO), and whether this subluxation was one cause of inconsistency between the actual and predicted alignments (correction loss).

The effect of the dimensions of the distal femur and proximal tibia joint surfaces on the development of knee osteoarthritis

The aim of this study was to determine whether the dimensions of the distal femur and proximal tibia joint surfaces affect the etiology of knee osteoarthritis (OA). The study comprised the records of 1,324 patients who had been admitted to hospital with knee pain. Anterioposterior (AP) and lateral radiographs of the knee were taken. Using the Kellgren‐Lawrence Scale, the patient group comprised Stages 2, 3, and 4 radiographs and the controls comprised Stages 0 and 1 radiographs. Four lengths were measured for each patient in both groups: femur mediolateral (femur ML), tibia mediolateral (tibia ML), femur anteroposterior (femur AP), and tibia anteroposterior (tibia AP). Osteophytes were not included in the measurements in the patient group. All the measurements were repeated by two researchers at two different times. The groups were compared in terms of these measurements and the correlations between them. The mean femur ML length was significantly greater in the patient group than the control group (P = 0.032) and the mean femur AP length was significantly less (P = 0.037). In addition, the difference between the femur ML and AP lengths was significantly high in the patient group (P < 0.001). The difference between the tibia and femur ML lengths was significantly high in the patient group (P < 0.001) and the difference between the tibia and femur AP lengths was higher in the control group (P = 0.001). A longer femur ML and a shorter femur AP, together with a greater difference between these two lengths and a greater difference between the tibia ML and femur ML lengths, could be a risk factor for developing knee OA. More extensive anatomical and biomechanical studies in the future will enable these results to be corroborated. Clin. Anat. 28:672–677, 2015. © 2015 Wiley Periodicals, Inc.     

A reliable method for measuring proximal tibia and distal femur bone mineral density using dual-energy X-ray absorptiometry

PurposeTo assess the intra- and inter-rater reliability of a standardized protocol for measuring proximal tibia and distal femur bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA).MethodsTen able-bodied individuals (7 males) participated in this study. During one measurement session, the knee of each participant was scanned twice by rater 1 using DXA. Both scans were analyzed twice by rater 1 as well as once by a second rater. Intraclass correlation coefficients (ICCs), standard error of measurements (SEMs) and smallest detectable differences (SDDs) were calculated for the outcome measures proximal tibia and distal femur BMD. A decision study was performed to determine the effect of study protocol adjustments (i.e. increasing the number of scan repetitions, or scan analyses by the same rater) on SEM and SDD values.ResultsHigh intra- and inter-rater ICCs (0.97–0.98) were found for both proximal tibia and distal femur BMD. Low SEMs (0.017–0.028 g/cm²) and SDDs (0.047–0.077 g/cm²) were found, with a slightly better result for proximal tibia BMD. Increasing the number of scan analyses by the same rater did not markedly reduce SEM and SDD values, while increasing the number of scan repetitions did.ConclusionsProximal tibia and distal femur BMD can be reliably assessed with this method.     

Three-dimensional morphology of the distal femur based on surgical epicondylar axis in the normal elderly population

BackgroundWe aimed to analyze the surface morphology of the distal femur in three dimensions for the healthy elderly, based on the concept that the surgical epicondylar axis (SEA) is a better surrogate for the flexion–extension axis of the knee joint.MethodsWe studied 77 healthy elderly volunteers (40 males and 37 females; age, 68 ± 6 years). The medial and lateral contact lines were calculated three-dimensionally, using the highest points of the medial and lateral condyles in 201 cross-sectional planes around the SEA (every 1°, −60° (hyperextension) to 140° (flexion)). A piecewise fitting function consisting of two linear segments was applied to detect the inflection point of the constant radii in the sagittal plane. The main assessment parameters were knee flexion angle at the inflection point of the radius (inflection angle), mean radius from 0° to the inflection angle (constant radius), and coronal tilt angle of the contact line.ResultsThe inflection angles, constant radii, and coronal tilt angles were 78.2 ± 8.6°, 26.1 ± 2.3 mm, and −0.6 ± 3.2° and 65.6 ± 9.2°, 23.9 ± 2.2 mm, and 6.2 ± 3.2° in the medial and lateral condyles, respectively (all, P < 0.001). The coronal alignment was 88.7 ± 2.2°.ConclusionsThe medial and lateral femoral condyles showed asymmetrical morphologies with the almost ‘constant’ radius of sagittal curvature from 0° to around 80° and 65° of knee flexion, respectively.     

Morphometry of the proximal tibia to design the tibial component of total knee arthroplasty for the Korean population

We carried out an anthropometric analysis using three dimensional computer tomographic measurements of the cut surface of the proximal tibia in 200 knees that were obtained from 50 male and 50 female Korean cadavers. We measured the mediolateral (ML), middle anteroposterior (AP), medial and lateral anteroposterior dimensions and the aspect ratio (ML/AP) of the resected proximal tibial surface; we then compared this data with the five conventionally used symmetric total knee components. We found that the ML (73.5+/-5.6 mm) and AP (47.3+/-3.8 mm) average dimensions of our study population were smaller than the dimensions of the symmetric commercially available TKA implants. We found a progressive decrease in the aspect ratio with the increasing anteroposterior dimension of the proximal tibia, as compared to the constant aspect ratio shown by the conventional tibial prostheses. The smaller sized prostheses were found to show mediolateral undersizing and the larger sized prostheses were found to show mediolateral overhang. This study may provide guidelines for designing a suitable tibial component of total knee prostheses for the Korean population, the aspect ratio of which decreases with increasing anteroposterior dimension.     

Gender and age related differences in foot morphology

Objective

This study has assessed age-related changes of foot morphology for developing appropriate footwear with particular reference to the elderly.

Methods

Anatomical parameters such as foot length, circumference and height and ankle length, circumference and height were assessed in a sample of males (n = 577) and females (n = 528) divided into three age groups. The groups included young-adult, aged between 20 and 25 years; adult, aged between 35 and 55 years; and old, aged between 65 and 70 years individuals.

Results

In terms of gender differences, in young-adult individuals the sex-related morphological differences observed, are just related to a significantly lower length of foot in females. In adult subjects morphological parameters investigated were significantly lower in females even after normalization for foot length. In old individuals, no differences of the parameters were found after normalization for foot length. Comparative analysis of morphometric data between young-adult and adult individuals revealed that the instep length was smaller in adults. The opposite was observed for the great toe and medial foot arch height. Length of ankle was higher in adult than in young-adult individuals, whereas ankle circumference and height were smaller. In old vs adult individuals foot circumference showed the most relevant age-related differences.

Conclusions

Feet anatomy presents specific characteristics in different ages of life. The ideal footwear should take into account these characteristics. This is true primarily for the elderly for minimizing the risk of falls or of other problems related to inappropriate footwear.     

双侧股骨近端对称性及解剖形态的三维重建研究

目的建立正常成人双侧股骨近端的三维模型,分析双侧股骨近端形态并测量解剖形态的相关参数,研究双侧股骨近端的对称性及解剖形态。方法选取50例正常成人双侧股骨近端CT扫描数据,其中男性27例,女性23例;年龄20～65岁,平均年龄44.52岁。扫描参数:扫描层厚0.625 mm,扫描电压120 kV,扫描电流100 mA。扫描范围:自双侧股骨头上10 mm至小转子中点平面下50 mm。将双侧股骨近端CT薄层扫描数据利用Mimics 10.01软件进行三维重建,将左侧股骨与右侧股骨镜像模型相配准,对配准后模型进行三维测量,并测量左右股骨近端的形态参数,使用SPSS 16.0软件对测量结果进行统计分析。结果股骨近端形态和髓腔内部结构有明显的个体差异性,双侧股骨近端形态及内部结构具有高度对称性。股骨头直径为(45.71±4.08)mm,股骨头高度为(53.61±5.43)mm,偏心距为(39.91±5.07)mm,股骨颈中央直径为(36.71±3.75)mm,颈干角为(127.88±6.28)°,股骨颈长度(46.61±4.74)mm,小粗隆中点所在平面的髓腔内径为(26.21±4.59)mm,其中偏心距、颈干角与白种人形态参数相比,差异有显著统计学意义(P<0.01);提供了一种验证双侧股骨对称性的新方法。结论正常成人双侧股骨内外部形态存在一定的对称性,变异较小,为股骨形态的测量提供理论依据;三维重建更利于对股骨近端形态参数的测量;新配准方法的提出对于临床中股骨近端骨折的诊治具有重大意义。     

Gender differences in distal femoral morphology and the role of gender specific implants in total knee replacement: a prospective clinical study

Gender differences in distal femoral morphology may affect femoral component fit using a standard range of prostheses. The clinical relevance of this is controversial.Standardised measurements were taken from the distal femora of 50 males and 50 females during total knee replacement (TKR). Corresponding measurements were taken from the respective gender specific and standard femoral components. No demographic differences were noted.Significant differences in both frequency and magnitude existed in the medial-lateral femoral component overhang between the sexes. In females, standard implants overhung at the anterior flange width (AFW) by > 2 mm in 24/50 (48%) and by > 3 mm in 17/50 (34%) (p < 0.001). Also at the anterior medial-lateral width (MLA) 29/50 (58%) overhung by > 2 mm and 24/50 (48%) by > 3 mm (p < 0.001). In males, standard implants overhung by > 2 mm in 1/50 (2%). In females, gender specific implants overhung by > 2 mm in 3/50 (6%). Females had a mean aspect ratio of 1.02 (0.82 to 1.35) and men 0.98 (0.79 to 1.19).Femoral component overhang can occur in females undergoing TKR and a gender specific implant would reduce the potential for medial-lateral overhang. Long term studies are awaited to quantify the clinical implications of overhang.     

Effects of a sliding plate on morphology of the epiphyseal plate in goat distal femur

The aim of this study was to observe the effects of a sliding plate on the morphology of the epiphyseal plate in goat distal femur. Eighteen premature female goats were divided randomly into sliding plate, regular plate and control groups. Radiographic analysis and histological staining were performed to evaluate the development of epiphyseal plate at 4 and 8 weeks after surgery. In the sliding plate group, the plate extended accordingly as the epiphyseal plate grows, and the epiphyseal morphology was kept essential normal. However, the phenomenon of the epiphyseal growth retardation and premature closure were very common in the regular plate group. In addition, the sliding plate group exhibited more normal histologic features and Safranin O staining compared to the regular plate group. Our results suggest that the sliding plate can provide reliable internal fixation of epiphyseal fracture without inhibiting epiphyseal growth.     

A three-dimensional computed tomography study of distal femoral morphology in Japanese patients: Gender differences and component fit

BackgroundPrevious anthropometric studies have reported gender differences in distal femoral morphology. However, to date, very few studies have investigated the knee morphology of Japanese adults and possible gender differences. The purpose of this study was to examine the distal femoral morphology of Japanese patients, to characterize anatomical differences between male and female, and to evaluate the need to create gender-specific knee prostheses.Material and methodsWe evaluated 80 knees in 40 male and 40 female Japanese patients scheduled for total knee arthroplasty (TKA). The mediolateral (ML) and anteroposterior (AP) dimensions of the knees at different levels were measured preoperatively using three-dimensional computed tomography, and ML/AP aspect ratios were calculated.ResultsOn the distal femoral cut surface, the mean ML widths were 74.9 mm for male and 65.1 mm for female, and the mean AP lengths were 63.4 mm for male and 58.9 mm for female. Such values were generally smaller compared to data from European and North American studies. In this study, the mean ML/AP aspect ratios were 1.31 for male and 1.25 for female, higher than those from non-Asian regions. The ML/AP ratios of Japanese patients were negatively correlated with distal femoral AP length.ConclusionsJapanese female had a relatively narrower femoral width for a given AP length than male. Our study suggests the utility of Japanese-specific implants and provides useful insights for manufacturers to design components of appropriate sizes and aspect ratios for Japanese TKA patients.     

胫骨近端后侧数字化三维形态学测量及临床意义

目的　研究胫骨近端后侧数字化形态学测量的方法,探讨其对胫骨后侧平台骨折诊疗的意义。  方法　对60例健康成人胫骨干燥标本进行CT扫描,图像导入Mimics 10.01软件建立数字化三维模型,测量相关解剖参数,分析其分布规律与相关关系。  结果　后侧正中高度（8.46±1.62）mm,后内侧高度（12.27±1.93）mm,后内侧斜坡长度（14.71±2.27）mm,后内侧平台斜坡角（132.02±11.62）°,后内侧斜坡骨干角（147.28±10.72）°,后外侧高度（11.31±1.74）mm,后外侧斜坡长度（14.45±2.26）mm,后外侧平台斜坡角（124.01±9.81）°,后外侧斜坡骨干角（141.88±9.09）°,所有测量参数双侧差异无统计学意义（P＞0.05）。后正中高度、后外侧高度和后外侧斜坡长度与胫骨全长具有相关性（P＜0.01）。   结论　本研究建立的胫骨近端数字化三维模型仿真度高,解剖参数测量结果精确度高,能为胫骨后侧平台骨折临床治疗和内固定物设计提供解剖学依据。     

中国人股骨头缺血性坏死股骨近端的形态研究

目的 研究股骨头缺血性坏死（AVN）股骨近端的形态,为选择、设计假体提供解剖学依据。方法 收集2004年1月至2008年8月因股骨头缺血性坏死行人工全髋关节置换术的病例186例（281髋）,拍摄股骨近端标准X线正侧位片,测量各节段数据,拟合内外前后四条曲线来描述髓腔形态,并依据年龄和性别分组分析各节段数据的差别。结果 排除由于皮质不清晰和塌陷严重的原因无法获得的完整资料病例59例外,共获得127例AVN患者的股骨近端数据,拟合了内外前后四条曲线,依据年龄分组在股骨内侧曲线远端上存在统计学差异（P<0.05）,依性别分组髓腔各曲线均无统计学差异,平均数据与以往国人正常人数据比较,在小转子及其以上节段存在较大差异。结论 获得了AVN股骨近端在标准X线正侧位片上的大宗数据,拟合了描述髓腔形态的内外前后四条曲线,推断AVN可能是影响股骨近端髓腔形态的独立因素。     

Morphological measurements of the posterior surface of the normal proximal tibia in a healthy Chinese population

BackgroundTo measure and calculate the morphological parameters and determine the anatomical characteristics of the posterior surface of the proximal tibia in a healthy Chinese population.MethodsA total of 150 volunteers with normal knees were enrolled. The parameters in the multi-slice spiral computed tomography (MSCT) three-dimensional (3-D) reconstruction images were measured and calculated by two independent qualified observers. The differences and correlation were investigated. The intraclass correlation coefficient (ICC) was used to assess inter-observer reliability.ResultsThe posterior margin of the tibial plateau is presented as two superior arc-shapes. The central angles of these arcs were 118° ± 14° (medial) and 106° ± 20° (lateral). The radii of these arcs both showed a skewed distribution. The median radii of the arcs were 22 mm in the medial and 20 mm in the lateral. There were two significant angles present in the sagittal plane of the posterior cortex of the proximal tibia. The first angles were 39° ± 7° (medial) and 47° ± 7° (lateral). The second angles were 39° ± 4° (medial) and 41° ± 5° (lateral). Significant differences were observed in the central angles and the first angles but not in the second angles between the medial and lateral. There were no significant differences between different gender groups, and between left and right limbs. All of these parameters exhibited excellent to moderate ICC.ConclusionDue to the varying anatomic morphology between the postero-medial and postero-lateral surface of the proximal tibia, the internal fixation implants of these two parts should be designed differently.     

Distribution of lengths of the normal femur and tibia in Korean children from three to sixteen years of age

To develop a standard growth curve of the lower extremity in Korean children from 3 to 16 yr of age, the lengths from a total of 2087 normal long bone segments (582 femurs and 645 tibias in boys, and 417 femurs and 443 tibias in girls) were measured. Children were grouped by years of bone age, which was determined by using the Korean specific bone age standard; TW2-20 method. The growth spurt occurred in girls from eight to eleven years by bone age, and in boys from eleven to thirteen years. The mean tibial length relative to the mean femoral length was 0.78 in boys and 0.79 in girls. The overall growth pattern was similar to that observed in American children in the 1960s. Korean children and adolescents appear to have a different tempo of skeletal maturation during pubertal growth from that of English and American children and adolescents. The Korean standard growth curve and the Korean bone age chart allow determination of the presence of any existent growth abnormalities and prediction of future remaining growth in lower extremities. These normative growth standards can be used for leg-length equalization purposes in children with anisomelia.     

三维数字化重建在中国人胫骨近端形态学研究中的应用

背景：在进行中国人膝关节假体设计以及全膝关节置换时,不仅要考虑到中国人胫骨近端解剖特点和几何形态上的差异,同时也还应该注意不同个体间的差异性。 目的：通过数字化技术分析中国人正常胫骨近端正常形态学参考值的变化。 方法：采集正常中国人两侧膝关节原始CT扫描图像,Mimics 10.1软件系统构建膝关节骨三维数字化模型。并对胫骨近端模型模拟截骨,测量胫骨截面相关线性参数。根据不同性别进行分组观察胫骨近端形态学参考值的变化。 结果与结论：除胫骨平台外侧前后径/内侧前后径、内侧前后径与外侧前后径的差值外,男性横径和前后径值均大于女性,大部分男性受试者所测量胫骨近端各截骨面值与女性受试者相比差异有显著性意义(P < 0.01)。说明正常中国人胫骨近端形态学存在性别个体差异,具体表现在：①不同测量方法形成的测量数据可更加全面反映胫骨近端形态学特征。②胫骨平台前后径/胫骨平台横径比值方面女性大于男性。     

Parosteal osteosarcoma of the distal tibia

We report on the case of a 24-year-old black male who presented to the orthopedic service with a parosteal osteosarcoma of the distal tibia. There have been 206 cases reported on this tumor in all the world's literature, with the distal femur being the most common location; this case report is rare, therefore, because of the unusual location of the tumor. This article was prepared in order to familiarize the general medical community with the occurrence of the tumor and to provide some general background information and treatment recommendations for parosteal osteosarcoma.     

Triangular structure of the proximal femur

The normal human skeleton is remarkably regular in form. Its constancy is demonstrated by the projection of well-recognized lines onto plain radiographs to define many of its relationships. The finding of the geometric symmetry of the normal proximal femur, demonstrated by the projection of an isosceles triangle onto its anteroposterior radiographic view, is presented. The base of this triangle extends between the trochanters and its apex lies at the center of the femoral head. This triangle may reflect the balance of bone modeling that takes place in the proximal femur as a result of the forces acting in the coronal plane. If so, it may then allow for the development of a mathematical expression for bone modeling in this plane.