Variations of relative anteversion of the femoral neck during walking

Summary Based on the geometric model developed by Netter [11], we determined the different positions of the femoral neck during monopodal support in walking in relation to a fixed frontal plane of reference (relative anteversion). This relative anteversion ranges on average from 24° of retroversion at the beginning of support to 15° of anterversion at the end if loading. We then studied the relations possibly existing between relative anteversion and acetabular orientation on the one hand, and the orientation of the resultant of the articular stresses on the other (both being variables during monopodal support in walking). The results showed that relative anteversion is well correlated with variations of position of the acetabulum since, at most, the deviation between the respective axes did not exceed the anatomic deviation due to absolute anteversion of the femoral neck and acetabulum. Lastly, analysis of the relations obtained with the orientation of the resultant of the articular stresses allowed a better comprehension of the functional distribution of forces.

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Variations de l'antéversion relative du col fémoral au cours de la marche

Résumé Nous inspirant de la modélisation géométrique développée par R. Netter dans sa thèse, nous avons déterminé les différentes positions du col fémoral au cours de l'appui monopodal de la marche par rapport à un plan frontal fixe de référence (antéversion relative). Cette «antéversion relative» s'échelonne en moyenne de 24° de rétroversion en début d'appui à 15° d'antéversion en fin d'appui. Nous avons alors étudié les relations pouvant exister entre l'antéversion relative et l'orientation de l'acétabulum, d'une part, et, d'autre part, l'orientation de la résultante des sollicitations articulaires (toutes deux variables au cours de l'appui monopodal de la marche). Les résultats nous ont montré que l'antéversion relative est bien corrélée aux variations de position de l'acétabulum puisque, au maximum, l'écart entre leurs axes respectifs ne dépasse pas l'écart anatomique du à l'antéversion absolue du col et de l'acétabulum. Enfin, l'analyse des rapports existant avec l'orientation de la résultante des sollicitations articulaires nous permet de mieux entrevoir la répartition fonctionnelle des contraintes.

     

不同X线方法计算髋臼杯前倾角的准确性和可靠性研究

[目的]本文研究了文献上7种X线片测量髋臼前倾角的可靠性和准确性,以总结出适合临床应用的测量方法.[方法]对2011年9月20日～10月20在积水潭医院矫形骨科进行初次全髋关节置换的60个病人60例髋关节进行了CT和X线片测量髋臼假体前倾角研究.以CT测量结果为金标准,三位独立的测量者使用7种X线测量方法测量的前倾角结果与CT测量的结果进行了比较以评估各种方法的准确性,并评估了各种测量方法的组内和组间测量的可靠性.[结果]所有7种X线测量方法均有很高的组内和组间测量可靠性.与CT测量结果相比较,Widmer方法和Visser方法是不准确的,其他方法均是准确的.Visser方法与解剖学前倾角有正向强相关性.[结论]7种X线测量髋臼假体前倾角的方法中Lewinneck、Hassan、Ackland、Liaw、和Pradhan方法是可靠和准确的,Wid-mer方法和Visser方法是不准确的,但Visser方法可以用于测量髋臼假体的解剖学前倾角.考虑到测量的准确和计算的简便性,建议临床上采用Lewinneck方法和Liaw方法测量髋臼假体的前倾角.     

Surgeon Error in Performing Intraoperative Estimation of Stem Anteversion in Cementless Total Hip Arthroplasty

To examine the accuracy of intraoperative estimation of stem anteversion in total hip arthroplasty (THA), we compared the intraoperatively estimated stem anteversion (estimated prosthetic anteversion) to stem anteversion measured by postoperative computed tomography (true anteversion) in 73 hips in 73 patients. Estimated prosthetic anteversion was significantly greater than true anteversion by 5.8°, and the mean absolute value of surgeon error was 7.3° ranging from 11° underestimation to 25° overestimation. Surgeons tended to overestimate when the true anteversion was smaller. A multivariate analysis showed that advanced knee osteoarthritis significantly increased surgeon error. These results indicated that estimated prosthetic anteversion was generally larger than true anteversion and that the grade of knee osteoarthritis affected the degree of surgeon error.     

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty

Purpose

The combined anteversion (CA) technique is a method in which the cup is placed according to the stem anteversion in total hip arthroplasty (THA). We examined whether the CA technique reduced the dislocation rate, and the distribution of CA with the manual placement of the cup.

Methods

We retrospectively reviewed 634 hips in 579 patients with primary cementless THA. In 230 hips using the CA technique [CA(+)], a CA of 50 ± 10° was the aim. In the remaining 404 hips [CA(−)], the cup was first placed targeting 20° of anteversion. The post-operative CA was measured using the computed tomography (CT) images in 111 hips.

Results

One hip (0.4 %) had a dislocation in the CA(+) group, whereas ten hips (2.5 %) had a dislocation in the CA(−) group. A multivariate analysis showed that primary diagnosis, head size and CA technique significantly influenced the dislocation rate. Patients in the CA(−) group were 5.8 times more likely to have a dislocation compared to the CA(+) group. In the 111 hips with CT images, 81 hips (73.0 %) achieved the intended CA.

Conclusions

Although the manual placement of the cup resulted in 27 % of outliers from the intended CA, the CA technique significantly reduced the dislocation after primary THA.     

Successful reconstruction of natural femoral anteversion using a short femoral stem in total hip arthroplasty surgery

ObjectiveTotal hip arthroplasty (THA) involves postoperative risks, such as thigh pain, periprosthetic fractures, and stress yielding. Short, anatomical, metaphyseal-fitting, cementless femoral stems were developed to reduce these postoperative risks. This study aimed to examine the “MiniMAX” prosthesis, which is a new generation, short, anatomical femoral stem made by Medacta.MethodsPatients underwent a low-dose computed tomography scan. Femoral anteversion was measured. We assessed the position and anteversion of the femoral component and compared them with the unoperated side. We also assessed the patients’ satisfaction and functional levels at 6 months postsurgery using the Harris Hip Score (HHS) and the Oxford Hip Score (OHS).ResultsNineteen individuals were recruited in this study. We found no significant difference in femoral anteversion between the operated hip and the native hip. Using the HHS and OHS questionnaires, we found clinical improvement in the 6-month postoperative scores compared with the preoperative scores.DiscussionThe new-generation, short, anatomical femoral stem made by Medacta is successful in reproducing natural femoral anteversion, while also improving patients’ functioning and lifestyle. Future large-scale, prospective comparison trials are required to further investigate this topic.     

Validation of a new method for determination of cup orientation in THA

Our goal was to validate accuracy, consistency, and reproducibility/reliability of a new method for determining cup orientation in total hip arthroplasty (THA). This method allows matching the 3D‐model from CT images or slices with the projected pelvis on an anteroposterior pelvic radiograph using a fully automated registration procedure. Cup orientation (inclination and anteversion) is calculated relative to the anterior pelvic plane, corrected for individual malposition of the pelvis during radiograph acquisition. Measurements on blinded and randomized radiographs of 80 cadaver and 327 patient hips were investigated. The method showed a mean accuracy of 0.7 ± 1.7° (?3.7° to 4.0°) for inclination and 1.2 ± 2.4° (?5.3° to 5.6°) for anteversion in the cadaver trials and 1.7 ± 1.7° (?4.6° to 5.5°) for inclination and 0.9 ± 2.8° (?5.2° to 5.7°) for anteversion in the clinical data when compared to CT‐based measurements. No systematic errors in accuracy were detected with the Bland–Altman analysis. The software consistency and the reproducibility/reliability were very good. This software is an accurate, consistent, reliable, and reproducible method to measure cup orientation in THA using a sophisticated 2D/3D‐matching technique. Its robust and accurate matching algorithm can be expanded to statistical models. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1583–1588, 2009     

应用三维重建测量股骨颈前倾角的计算机方法研究

目的寻求一种测量结果更符合真实前倾角值的测量方法。方法应用计算机重建股骨CT断层图像获得三维模型,将股骨头拟合成球体以确定股骨头中心;然后截取股骨颈区域并重新分割为断层图像,测量每层的体积进行比较以确定股骨颈峡部,从而确定股骨颈中心;经三维模型表面直接选取内、外髁。结果股骨头中心、股骨颈中心的连线即为颈轴线,内、外髁的连线即为髁状轴,根据Billing对前倾角的定义,两线所形成的夹角即为前倾角。结论该研究符合定义法测量,故测量结果更为可信。     

Patellofemoral characteristics in patients with increased femoral anteversion

In this study, the association between increased femoral anteversion and the characteristics of the patellofemoral joint was investigated in adults. In 17 female control patients, the anteversion angle of the femoral neck measured 12°±8° and 11°±9° for the right and left side, respectively. The sulcus angle of the patellofemoral joint was 145°±10° and 146°±11°, the congruence angle 7.2°±14° and 7.8°±15°, and the lateral patellofemoral angle 5.9°± 6° and 5.7°±6°, respectively. In 15 female patients who were evaluated for clinical symptoms of increased femoral anteversion, the anteversion angle of the femoral neck was 30°±7° and 31°±8° degrees for the right and left side, respectively. The sulcus angle was 143°±8° and 147°±9°, the congruence angle 7.3°±12° and 7.1°±13°, and the lateral patellofemoral angle 6.4°±8° and 6.1°±7°, respectively. There was no correlation between the degree of femoral anteversion and the indices of the patellofemoral relationships. Thus, this study indicates that there is no association between increased femoral anteversion and abnormal patellofemoral characteristics.