Biplanar Low-Dose Radiography is Accurate for Measuring Combined Anteversion after Total Hip Arthroplasty

Abstract

Background

Acetabular component position alone has not been predictive of stability after total hip arthroplasty (THA). Combined anteversion of the acetabulum and femur has the potential of being more predictive of stability. Unfortunately, femoral component position is difficult to measure on plain radiographs. Computed tomography (CT) is the gold standard for measuring implant position post-operatively, but CT exposes patients to a substantial amount of radiation.

Questions/Purposes

We sought to determine whether biplanar low-dose radiography can be used to accurately measure both acetabular and femoral implant position after THA.

Methods

Twenty patients underwent standing low-dose biplanar spine-to-ankle radiographs and supine CT scans 6 weeks after THA. Measurements of acetabular inclination, acetabular anteversion, and femoral anteversion were performed by two blinded observers and compared.

Results

The average absolute differences between biplanar radiographs and CT scans were 2° ± 2° for acetabular inclination, 3° ± 2° for acetabular anteversion, and 4° ± 4° for femoral anteversion between EOS measurements and CT measurements. Interobserver agreement was good for acetabular inclination, acetabular anteversion, and femoral anteversion (Cronbach's α = 0.90) using biplanar low-dose imaging.

Conclusion

Biplanar radiography is a reliable low-radiation alternative for measuring acetabular inclination, acetabular anteversion, femoral version, and thus combined anteversion compared to CT. Femoral anteversion had the most variability but is still clinically relevant.

Keywords

total hip arthroplasty imaging implant position computed tomography anteversion

Introduction

Implant position plays a major role in mechanical stability and accelerated bearing wear after total hip arthroplasty (THA) [20, 32, 35]. The standard modality for assessing implant position after THA is a two-dimensional (2D) anteroposterior (AP) radiograph, due to low radiation dose and low cost. Acetabular component position (inclination and anteversion) can be measured relative to the coronal reference frame defined by the radiograph itself. Alternatively, a cross table lateral may also be useful when determining acetabular anteversion [24, 27]. However, recent studies have demonstrated that the traditional “safe zone” for acetabular component position on an AP radiograph may not reduce the risk of dislocation [1, 8]. The acetabular position accounts for only half of the hip replacement; femoral implant position is an essential element in determining impingement-free arc of motion [6, 28]. Unfortunately, a shortcoming of conventional radiographs is their inability to measure femoral anteversion.

Femoral anteversion can be measured using three-dimensional (3D) imaging technologies, such as computed tomography (CT), where it is possible to choose a coronal reference frame according to femoral landmarks, such as the posterior condylar axis. But most surgeons do not routinely order CT scans post-operatively to measure implant position due to clinical practicality, cost, and radiation concerns. The ability to measure femoral stem anteversion in THA patients routinely may be beneficial to surgeons as they consider the role of combined anteversion (both acetabular and femoral anteversion) on THA stability [6, 28].

Biplanar radiography has recently started to be used as a means for measuring hip component position [17, 18]. Biplanar radiography can calculate 3D patient information from two simultaneous frontal and lateral radiographs of a standing patient without stitching or vertical distortion and has been shown to be more reliable than conventional 2D radiographs for lower extremity measurements [11]. Previous studies have validated biplanar imaging for 3D reconstruction of lower limbs in adults and children [2, 3, 10, 25, 29, 30]. However, only one study has reported on the accuracy of biplanar radiography for measurement of THA implant position [14]. A major limitation of this study was the use of dry bone models, which do not have the additional tissues that could limit visibility of anatomic landmarks in patients. Therefore, the purpose of this prospective study was to assess the accuracy and reproducibility of measuring hip component position using biplanar radiography compared to the gold standard method of CT in a series of patients who underwent THA.

Materials and Methods

After institutional review board approval, 20 patients undergoing unilateral cementless THA consented to this analysis of post-operative THA alignment. All patients had supine CT scans and standing EOS biplanar radiography taken 6 weeks post-operatively (Fig. 1). CT images of the pelvis and femur were segmented using Mimics software (Materialise, Leuven, Belgium), and component position was measured using Geomagic Studio (Morrisville, NC, USA) and Creo Parametric (PTC Creo, Needham, MA, USA). CT reconstruction methods have been shown to be accurate for determining acetabular cup orientation [4, 15, 21, 31]. Post-operative acetabular angles (acetabular inclination and anteversion) and femoral angles (femoral anteversion) were measured on biplanar radiographs using sterEOS® software (EOS Imaging Acquisition System, EOS Imaging Inc., Paris, France). Anatomic references were used to define acetabular and femoral component position on both biplanar radiographs and CT in order to avoid angular differences that can occur with pelvic tilt or femoral rotation in supine or standing positions (changes in functional implant alignment). The anterior pelvic plane (APP) (defined by the two anterior superior iliac spines and the pubic symphysis) was used as an anatomic reference for acetabular inclination and anteversion (Fig. 2). The most posterior part of the femoral condyles was used as an anatomic reference for femoral anteversion (defined as the angular difference between the axis of the femoral neck and the posterior bi-condylar axis; Fig. 3). Two blinded observers (C.E., T.M.), a musculoskeletal radiologist and an experienced user engineer, measured hip angles using sterEOS software. For the purpose of this study, a senior musculoskeletal radiologist (T.M.) and an expert user engineer (C.E.), trained prior to the start of this study to identify the necessary anatomic landmarks, performed the measurements. The primary outcomes were acetabular inclination, acetabular anteversion, and femoral anteversion measured using biplanar radiography compared to the gold standard CT method in the same patients.

Fig. 1

a 3D computed tomography (CT) reconstruction of pelvis (coronal view) and femur (transverse view). Implants are shown in green; CT femoral anteversion in this patient was 12.4°. b Simultaneous and orthogonal acquisition of these standing anteroposterior and lateral radiographs allowed for 3D implant position measurements (cup inclination, cup anteversion, and femoral anteversion).

Fig. 2

Cup position on radiographs was measured using the sterEOS workstation which requires users to manually identify anatomic and implant landmarks including the anterior superior iliac spines (blue and red +) and the ring of the acetabular component (green circles).

Fig. 3

a Sagittal and anteroposterior views of the femoral stem where the neck axis (in red) is manually identified to measure femoral anteversion. b Sagittal and anteroposterior views of a right knee, where the medial (light blue) and lateral (dark blue) femoral condyles of the knee to measure femoral anteversion.

We calculated the deviations in cup inclination, cup anteversion, and femoral anteversion found using biplanar radiographs from the reference CT values and stated the means and standard deviations of the respective amounts. The differences in these means were tested for statistical significance by the Mann–Whitney Rank Sum Test. To check the accuracy of the biplanar radiographic measurement method, we determined the Pearson correlation between the paired results of two measurements. Correlation coefficients greater than 0.8 were assessed as good and hence as confirming the high reliability of the measurement procedure. Interobserver reliability was calculated using the Cronbach's α (∝) coefficient of reliability. In each case, the significance level was set at p < 0.05. All statistical tests were performed with SPSS Statistics, Version 25 (IBM, New York, NY, USA).

Results

The mean absolute differences between biplanar radiography and CT measurements were 2° ± 2° for acetabular inclination, 3° ± 2° for acetabular anteversion, and 4° ± 4° for femoral anteversion. There was no significant difference in these errors (Table 1). Measurements by two observers showed good correlations to CT values, with Pearson correlation coefficients greater than 0.78 for all hip angles (Table 1). While measurement with biplanar radiograph was only slightly different than reference values, substantial outliers have to be taken into account. In one measurement of acetabular anteversion and four measurements of femoral anteversion, there were greater than 10° difference between biplanar radiography and CT measurements (highlighted by black circles in Fig. 4). The two observers made an error in femoral anteversion measurements in two different patients. This may be explained by users incorrectly identifying anatomic landmarks, such as the anterior superior iliac spines on the pelvis or the posterior femoral condyles on the knees (Fig. 3). Interobserver agreement was good for acetabular inclination (Cronbach's α = 0.83), acetabular anteversion (Cronbach's α = 0.89), and femoral components (Cronbach's α = 0.89) using EOS imaging.

Table 1.

Summary of measurement errors comparing computed tomography (CT) to biplanar radiography for hip angles

Measure	Observer 1 Cup inclination (°)	Observer 2 Cup inclination (°)	Observer 1 Cup anteversion (°)	Observer 2 Cup anteversion (°)	Observer 1 Femoral anteversion (°)	Observer 2 Femoral anteversion (°)
Mean absolute difference	0.24	0.65	− 0.13	− 1.72	3.67	2.47
Standard deviation	1.97	2.01	3.43	4.04	3.65	5.28
Range	4.6 − 4.0	3.7 − 4.4	7.3 − 7.8	5.8 − 9.8	11.3 − 1.3	13.6 − 14.8
95% confidence interval range	1.10 − 0.63	1.53 − 0.23	1.37 − 1.63	0.05 − 3.49	5.27 2.07	4.79 0.16
Pearson correlation coefficient^*	r = 0.87, p < 0.01	r = 0.89, p < 0.01	r = 0.85, p < 0.01	r = 0.78, p < 0.01	r = 0.91, p < 0.01	r = 0.88, p < 0.01

Reliability of biplanar radiography measurements compared to reference CT measurements

Fig. 4

Scatter plots showing computed tomography (CT) and biplanar radiography measurements for cup inclination (a), cup anteversion (b), and femoral anteversion (c) in the same 20 patients. If CT and biplanar radiography measurements are a perfect match for a patient, a data point falls on the dotted black line. Black circles identify data points where biplanar radiography measurements differed from CT measurements by more than 10°.

Discussion

While CT scans are the gold standard for measuring total hip component positions, they are not obtained during weight-bearing and cannot be used routinely in clinical practice due to cost and high radiation exposure. Therefore, this study sought to consider whether biplanar radiography can accurately and reliably measure acetabular and femoral component position in patients after THA, while exposing patients to lower X-ray emission compared to conventional techniques [22].

Our study has limitations. Landmarks can be difficult to identify and in five patients, we had an error greater than 10° in either acetabular or femoral anteversion. In addition, we were limited by our study size of 20 patients. However, we determined that 20 patients were required to achieve 80% power to detect a minimum proportion of 70% positive tests (versus null kappa of 0.00) between two groups using intraclass correlation coefficients. Also, we did not analyze the reproducibility of the CT measurements that we performed in this study, but it has previously been shown that intraobserver and interobserver agreement in CT measurements is high [24].

Training and practice are necessary to identify anatomic landmarks correctly on biplanar radiographs. Biplanar radiography has been compared to 2D radiographs for lower extremity measurements [11], to CT for assessment of limb length [7], to CT for measuring femoral and tibial rotational alignment [10], to conventional radiographs or saw bones for THA acetabular component position [14, 18], and to conventional radiographs for femoral offset [19]. One study has validated biplanar radiography for measuring acetabular component position using four pelvic phantom models [5], and another study has validated it for measuring femoral stem position using 28 femoral stems implanted in composite femurs [12]. We found an expected error of 2° for acetabular anteversion, 3° for acetabular anteversion, and 4° for femoral anteversion in patients, which should be clinically significant and provide useful information to the surgeon without requiring a CT scan. Conventional radiographs may be useful for measuring varus or valgus stem alignment [16], but cannot be used to measure femoral anteversion. While we found the greatest error associated with measuring femoral anteversion, we feel that biplanar radiography can provide information on whether a patient has high or low femoral stem anteversion, and this additional information may be useful as the patient is followed after THA. For the purpose of this study, a senior musculoskeletal radiologist and an engineer performed the measurements and they were trained prior to the start of this study to identify the necessary anatomic landmarks. In one patient, there was an error of more than 10° in acetabular anteversion and in four patients, there was an error of more than 10° in femoral anteversion (see black circles in Fig. 4). Error can occur from incorrectly identifying landmarks such as the anterior superior iliac spines on the pelvis (Fig. 2) or the posterior femoral condyles on the knees (Fig. 3b). However, if a user is properly trained, biplanar radiography can replace CT imaging for measuring THA component position. Training to gain competence should be done with a musculoskeletal radiologist in order to properly identify bony landmarks and implant landmarks, such as the rim of the metal acetabular component. We recommend evaluating user competence with a set of biplanar images where acetabular and femoral component position is known from additional CT imaging or sawbone models, to gain confidence in a new user's ability to make measurements on biplanar radiographs.

Biplanar imaging allows measurement not only of anatomic definitions of component position but also functional component position in standing or sitting [9, 23]. Therefore, we may be able to start to consider the impact of pelvic tilt and femoral torsion on functional combined anteversion. Few studies have been able to report on the impact of combined anteversion on hip dislocation, since most centers do not obtain post-operative CT scans of THA patients. One study has shown that a combined anteversion technique reduced the rate of dislocation by six times in cementless THA [26]. Hip surgeons understand well the importance of femoral anteversion, and CT studies have shown that femoral stem anteversion is highly variable [6]. In our study, femoral stem anteversion ranged from 3 to 25° on CT, while other studies have shown the range of cementless femoral component version to be as extreme as 30° retroversion to 45° anteversion [34]. The concept of combined anteversion was introduced by Ranawat et al. in 1991 [28], suggesting the sum of the cup anteversion and stem anteversion should be 45° for women and between 20 and 30° for men. Subsequently, several mathematical models were developed to determine the combination of cup inclination and anteversion, and stem anteversion providing the greater range of motion and lower risk of cup-stem impingement [13, 33, 35]. However, future studies need to consider variability in post-operative femoral anteversion and whether femoral anteversion can be predicted pre-operatively.

Dislocation continues to be one of the leading causes of revision surgery, and variations in both acetabular and femoral implant position may contribute to the risk. We believe that biplanar imaging will be an important tool for considering the impact of implant position on hip stability, since we can now collect data on a large series of patients to identify patient outliers who have extreme retroversion or anteversion of either the acetabular or the femoral component.

Electronic Supplementary Material

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM1_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM1_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM2_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM2_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM3_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM3_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM4_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM4_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM5_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM5_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM6_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM6_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Electronic supplementary material

Electronic supplementary material, 11420_2018_9659_MOESM7_ESM - Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty

Electronic supplementary material, 11420_2018_9659_MOESM7_ESM for Biplanar Low-Dose Radiography Is Accurate for Measuring Combined Anteversion After Total Hip Arthroplasty by, http://orcid.org/0000-0003-3321-4753 Esposito Christina I., PhD, Miller Theodore T., MD, Lipman Joseph D., MS, Carroll Kaitlin M., BS, Padgett Douglas E., MD, Mayman David J., MD, Jerabek Seth A., MD, in HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery

Footnotes

Electronic supplementary material

The online version of this article (10.1007/s11420-018-09659-7) contains supplementary material, which is available to authorized users.

Compliance with Ethical Standards

Conflict of Interest

Christina I. Esposito, PhD, and Kaitlin M. Carroll, BS, declare that they have no conflicts of interest. David J. Mayman, MD, reports stock or stock options from Imagen Technologies and OrthAlign; personal fees for consultancy, lectures, and grants from Smith & Nephew; and board membership with the Knee Society. Douglas E. Padgett, MD, reports board membership with American Joint Replacement Registry, Journal of Arthroplasty, and Hip Society; personal fees and royalties from DJ Orthopaedics and PixarBio; and stock or stock options from PixarBio. Joseph D. Lipman, MS, reports royalties from Exactech, Inc., LimaCorporate, Mathys Ltd., and Ortho Development Corporation. Seth A. Jerabek, MD, reports personal fees, speakers’ fees, royalties, and grants from Stryker and stock and stock options from Imagen Technologies. Theodore T. Miller, MD, reports educational fees from Amirsys Publishing Co.

Human/Animal Rights

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2013.

Informed Consent

Informed consent was obtained from all patients for being included in this study.

Required Author Forms

Disclosure forms provided by the authors are available with the online version of this article.

Publisher's note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

Abdel

von Roth

Jennings

Hanssen

Pagnano

What safe zone? The vast majority of dislocated THAs are within the Lewinnek safe zone for acetabular component position

Clin Orthop2016474386–391

10.1007/s11999-015-4432-5

Buck

Guggenberger

Koch

Pfirrmann

CWA

Femoral and tibial torsion measurements with 3D models based on low-dose biplanar radiographs in comparison with standard CT measurements

Am J Roentgenol2012199W607–612

10.2214/AJR.11.8295

Chaibi

Cresson

Aubert

Fast 3D reconstruction of the lower limb using a parametric model and statistical inferences and clinical measurements calculation from biplanar X-rays

Comput Methods Biomech Biomed Engin.201215457–466

10.1080/10255842.2010.540758

Craiovan

Renkawitz

Weber

Grifka

Nolte

Zheng

Is the acetabular cup orientation after total hip arthroplasty on a two dimension or three dimension model accurate?

Int Orthop.2014382009–2015

10.1007/s00264-014-2336-8

Demzik

Alvi

Delagrammaticas

Martell

Beal

Manning

Inter-rater and intra-rater repeatability and reliability of EOS 3-dimensional imaging analysis software

J Arthroplasty2016311091–1095

10.1016/j.arth.2015.11.026

Dorr

Malik

Dastane

Wan

Combined anteversion technique for total hip arthroplasty

Clin Orthop.2009467119–127

10.1007/s11999-008-0598-4

Escott

Ravi

Weathermon

EOS low-dose radiography: a reliable and accurate upright assessment of lower-limb lengths

J Bone Joint Surg Am201395e1831–1837

10.2106/JBJS.L.00989

Esposito

Gladnick

Lee

Y-Y

Cup position alone does not predict risk of dislocation after hip arthroplasty

J Arthroplasty2014301109–113

10.1016/j.arth.2014.07.009

Esposito

Carroll

Sculco

Padgett

Jerabek

Mayman

Total hip arthroplasty patients with fixed spinopelvic alignment are at higher risk of hip dislocation

J Arthroplasty20183351449–1454

10.1016/j.arth.2017.12.005

10.

Folinais

Thelen

Delin

Radier

Catonne

Lazennec

Measuring femoral and rotational alignment: EOS system versus computed tomography

Orthop Traumatol Surg Res201399509–516

10.1016/j.otsr.2012.12.023

11.

Guenoun

Zadegan

Aim

Hannouche

Nizard

Reliability of a new method for lower-extremity measurements based on stereoradiographic three-dimensional reconstruction

Orthop Traumatol Surg Res201298506–513

10.1016/j.otsr.2012.03.014

12.

Guenoun

El Hajj

Biau

Anract

Courpied

J-P

Reliability of a new method for evaluating femoral stem positioning after total hip arthroplasty based on stereoradiographic 3D reconstruction

J Arthroplasty201530141–144

10.1016/j.arth.2014.07.033

13.

Hisatome

Doi

Theoretically optimum position of the prosthesis in total hip arthroplasty to fulfill the severe range of motion criteria due to neck impingement

J Orthop Sci201116229–237

10.1007/s00776-011-0039-1

14.

Journé

Sadaka

Bélicourt

Sautet

New method for measuring acetabular component positioning with EOS imaging: feasibility study on dry bone

Int Orthop2012362205–2209

10.1007/s00264-012-1650-2

15.

Kim

Y-H

Cho

K-H

Park

Y-G

Is the acetabular cup orientation after total hip arthroplasty on a two-dimensional or three-dimensional model accurate?

Int Orthop201539819–820

10.1007/s00264-015-2697-7

16.

Kutzner

Freitag

Donner

Kovacevic

Bieger

Outcome of extensive varus and valgus stem alignment in short-stem THA: clinical and radiological analysis using EBRA-FCA

Arch Orthop Trauma Surg2017137431–439

10.1007/s00402-017-2640-z

17.

Lazennec

Brusson

Rousseau M-A. THA patients in standing and sitting positions: a prospective evaluation using the low-dose “full-body” EOS® imaging system

Semin Arthroplasty201223220–225

10.1053/j.sart.2013.01.005

18.

Lazennec

Rousseau

Rangel

Pelvis and total hip arthroplasty acetabular component orientations in sitting and standing positions: measurements reproductibility with EOS imaging system versus conventional radiographies

Orthop Traumatol Surg Res201197373–380

10.1016/j.otsr.2011.02.006

19.

Lazennec

Brusson

Dominique

Rousseau

M-A

Pour

Offset and anteversion reconstruction after cemented and uncemented total hip arthroplasty: an evaluation with the low-dose EOS system comparing two- and three-dimensional imaging

In Orthop2015391259–1267

20.

Lewinnek

Lewis

Tarr

Compere

Zimmerman

Dislocations after total hip-replacement arthroplasties

J Bone Joint Surg Am197860217–220

10.2106/00004623-197860020-00014

21.

Lin

Lim

Wixson

Milos

Hendrix

Makhsous

Validation of a computer navigation system and a CT method for determination of the orientation of implanted acetabular cup in total hip arthroplasty: a cadaver study

Clin Biomech Bristol Avon2008231004–1011

10.1016/j.clinbiomech.2008.04.015

22.

Mahboub-Ahari

Hajebrahimi

Yusefi

Velayati

EOS imaging versus current radiography: a health technology assessment study

Med J Islam Repub Iran2016303314898869

23.

Maratt

Esposito

McLawhorn

Jerabek

Padgett

Mayman

Pelvic tilt in patients undergoing total hip arthroplasty: when does it matter?

J Arthroplasty2015303387–391

10.1016/j.arth.2014.10.014

24.

McArthur

Cross

Geatrakas

Mayman

Ghelman

Measuring acetabular component version after THA: CT or plain radiograph?

Clin Orthop20124702810–2818

10.1007/s11999-012-2292-9

25.

Morvan

Guerini

Carré

Vuillemin

Femoral torsion: impact of femur position on CT and stereoradiography measurements

Am J Roentgenol2017209W93–W99

10.2214/AJR.16.16638

26.

Nakashima

Hirata

Akiyama

Combined anteversion technique reduced the dislocation in cementless total hip arthroplasty

Int Orthop20143827–32

10.1007/s00264-013-2091-2

27.

Nunley

Keeney

Zhu

Clohisy

Barrack

The reliability and variation of acetabular component anteversion measurements from cross-table lateral radiographs

J Arthroplasty20112684–87

10.1016/j.arth.2011.03.039

28.

Ranawat

Maynard

Modern techniques of cemented total hip arthroplasty

Tech Orthop1991617–25

10.1097/00013611-199109000-00004

29.

Rosskopf

Pfirrmann

CWA

Buck

Assessment of two-dimensional (2D) and three-dimensional (3D) lower limb measurements in adults: comparison of micro-dose and low-dose biplanar radiographs

Eur Radiol2016263054–3062

10.1007/s00330-015-4166-5

30.

Rosskopf

Buck

Pfirrmann

CWA

Ramseier

Femoral and tibial torsion measurements in children and adolescents: comparison of MRI and 3D models based on low-dose biplanar radiographs

Skeletal Radiol201746469–476

10.1007/s00256-017-2569-x

31.

Tsai

T-Y

Dimitriou

Kwon

Y-M

Does total hip arthroplasty restore native hip anatomy? three-dimensional reconstruction analysis

Int Orthop2014381577–1583

10.1007/s00264-014-2401-3

32.

Wan

Boutary

Dorr

The influence of acetabular component position on wear in total hip arthroplasty

J Arthroplasty20082351–56

10.1016/j.arth.2007.06.008

33.

Widmer

K-H

Zurfluh

Compliant positioning of total hip components for optimal range of motion

J Orthop Res200422815–821

10.1016/j.orthres.2003.11.001

34.

Wines

McNicol

Computed tomography measurement of the accuracy of component version in total hip arthroplasty

J Arthroplasty200621696–701

10.1016/j.arth.2005.11.008

35.

Yoshimine

The safe-zones for combined cup and neck anteversions that fulfill the essential range of motion and their optimum combination in total hip replacements

J Biomech2006391315–1323

10.1016/j.jbiomech.2005.03.008