Templating In Total Hip Arthroplasty Research Articles

A more accurate method to determine the magnification of radiographs when templating for hip arthroplasty?

The use of digital templating for Total Hip Arthroplasty (THA) is now the standard approach for pre-operative planning. Digital templating holds potential to reduce operative time and post-op complications however, this often relies on imprecise assumptions.

Accuracy of Preoperative Templating in Total Hip Arthroplasty With Special Focus on Stem Morphology: A Randomized Comparison Between Common Digital and Three-Dimensional Planning Using Biplanar Radiographs

BackgroundAccurate preoperative planning is a key component of successful total hip arthroplasty (THA). The purpose of the present study was to compare the accuracy and reliability of three-dimensional (hipEOS) and common digital two-dimensional (TraumaCad) templating with special focus on stem morphology. Methods51 patients undergoing THA were randomized to two groups. Preoperative planning was performed on 23 patients with hipEOS (3D) and on 28 patients with TraumaCad (2D) planning software. Planning results were compared with the implanted component size. Inter- and intraobserver reliability as well as planning accuracy of both planning methods with special focus on straight and short stem design were recorded. ResultsIntraobserver reliability of both planning methods was good for component planning (ICC2,1: 0.835-0.967). Interobserver ICC2,1 for stem and cup planning were higher for 3D templating (3D ICC2,1: 0.906-0.918 vs. 2D ICC2,1: 0.835-0.843). Total stem and cup size predictions were within 2 sizes for 3D and within 3 sizes for 2D planning. Comparing short stem planning accuracy of both planning methods, absolute difference between implanted and planned component size was significantly lower in 3D planning (P = .029). There was no significant difference in straight stem (P = .935) and cup (P = .954) planning accuracy. ConclusionOur findings suggest that 3D templating with hipEOS software has a good overall reliability and may have a better planning accuracy of short stem prostheses than digital templating with TraumaCad software. Assuming that the number of implanted short stem prostheses will further increase in coming years, a more precise planning with 3D technique can contribute to improve surgery outcome.

A novel calibration method for digital templating of total hip arthroplasty: a prospective clinical study of dual scale type single marker calibration in supine radiographs.

External calibration markers (ECM) are the standard of care for digital templating in joint replacements. Spherical mono markers are known to be unreliable. Fixed calibration factors (FCF) can reduce the overall error by placement of markers, but do not address individual patient anatomy. Dual scale calibration marker (DSCM) methods were developed to improve precision of calibration but require two markers. This prospective observational study is the first to analyse the application of a dual scale type single marker (DSSM) method in supine radiographs. One hundred patients with unilateral total hip arthroplasty (THA) underwent anterior-posterior pelvis X-ray with ECM and DSSM. The femoral THA head components were used as internal reference (ICM). An empirical fixed calibration factor (FCF; 120%) was used as comparator. Absolute differences of ICM and both ECM and DSSM were calculated. Absolute relative deviations (ARD) were calculated. Mean absolute calibration factor differences of ECM, FCF and DSSM from ICM were 0.105 (0.002-0.182), 0.016 (0.082-0.013) and 0.011 (0.056-0.009), respectively. ARD differences between ECM and DSSM as well as FCF and DSSM were significant (p < 0.001). The DSSM method showed superior results over ECM and FCF to predict the optimal calibration factor in supine radiographs. The novel DSSM method could be used to improve digital templating in supine radiographs without need for additional markers.

Pre-operative templating in THA. Part II: a CT-based strategy to correct architectural hip deformities.

Pre-operative templating for total hip arthroplasty (THA) remains inaccurate due to improper magnification and alignment. We aimed to describe an improved templating strategy using computed tomography (CT) to predict component sizes and offsets with greater accuracy. We analysed 184 CT images acquired for pre-operative templating of primary THA. We aimed to restore native (pre-arthritic) femoral offset and limb length, by raising the head center to the level of the templated cup center cranio-caudally, but maintaining the pathologic (pre-operative) head center medio-laterally (except in medialized hips). Acetabular offset (AO) and femoral offset (FO) were measured on pre-operative CT scans, during acetate templating, and on post-operative true antero-posterior radiographs. The post-operative offsets were within ± 5mm from templated estimates in 174 hips (91%) for AO, in 116 hips (61%) for FO, in 111 hips (58%) for GO, and in 134 hips (70%) for neck cut level. The post-operative hip architecture reproduced the templated hip architecture within ±5mm in 77 hips (40%). The agreement between planned and post-operative parameters was moderate for stem size (0.57), cup size (0.62), AO (0.50), but fair for FO (0.45). The AO decreased in most arthritic types, notably in lateralized hips (6.6mm), but remained unchanged in medialized hips. The FO increased in most arthritic types (1.8-3.1mm) but remained unchanged in medialized and lateralized hips. We described a strategy for pre-operative templating in THA. Despite the accuracy of CT, the authors found significant variations between planned and post-operative reconstructions, which suggest that pre-operative templating should only be used as an approximate guide.

Pre-operative planning in THA. Part III: do implant size prediction and offset restoration influence functional outcomes after THA?

Few studies evaluated clinical benefits of pre-operative templating in total hip arthroplasty (THA). We investigated whether mismatch between planned and real implant sizes and medio-lateral offsets compromises THA outcomes. We reviewed records of 184 primary THAs with pre-operative CT scans used for templating. Acetabular offset (AO), femoral offset (FO) and global offset (GO) were measured on pre-operative CT scans, during acetate templating, and post-operative antero-posterior radiographs. Multivariable analyses were performed to determine if Forgotten Joint Score (FJS) and Oxford Hip Score (OHS) at > 2years were associated with differences between post-operative and planned parameters. The FJS and OHS were not influenced by mismatch of component sizes nor of FO and GO. The FJS was better when the post-operative AO was greater than planned (p = 0.050). The FJS differed among arthritic types (p = 0.015). Multivariable analyses confirmed that older patients had better OHS (beta - 0.16; p = 0.033) and FJS (beta 0.74; p = 0.002), medialized hips had worse FJS (beta - 20.1; p = 0.041) and hips with greater AO than planned had better FJS (beta 1.71; p = 0.024) CONCLUSIONS: Implanting a component of different size than planned did not compromise THA outcomes, but medialized hips had worse scores, and conservative acetabular reaming improved scores.

The accuracy of pre-operative digital templating in total hip arthroplasty performed in a low-volume, resource-constrained orthopaedic unit

Aims: Total hip arthroplasty (THA) is considered one of the most successful surgical procedures in modern medicine. The success of THA is well documented, and includes high patient satisfaction rates, low morbidity rates and cost-effective surgery. Most publications come from THA performed in high-volume arthroplasty units, done in high-income countries. Limited data is available on THA performed in low-volume, low-income countries. The aim of this study was to evaluate the accuracy of digital templating in a low-volume, resource constrained orthopaedic unit from 2016 to 2017. We introduced a standardised hip radiography programme, followed by a stepwise pre-operative templating method. We compared the implant sizes inserted during THA with the templated sizes determined pre-operatively. This was to deduct whether digital templating in a low volume arthroplasty unit is accurate and of the same value as digital templating done in a high-volume unit. Methods: A descriptive retrospective study was conducted on all patients who received elective primary uncemented THA in a low-volume, resource-constrained orthopaedic unit. Pre-operative radiographs were done according to guidelines published by Scheerlinck followed by pre-operative templating using the Impax Orthopaedic tools® software and a stepwise technique described by Bono. Implanted prosthesis sizes, as recorded in operation notes, were retrospectively compared to pre-operative templating. Results: A total of 56 participants were included (30 females, 26 males), with a mean age of 55.5 (32–78) years. On the acetabular side, in 71% (n=40; p<0.001) there was a cumulative difference of one implant size between the templated cup size and the actual cup size used. On the femoral side, in 79% (n=44; p<0.001) there was a cumulative difference of one implant size between the templated stem size and the actual stem size used. Oversizing of the implants was more prevalent, with 20% (n=11) of the acetabular components oversized by two or more sizes and 13% (n=7) of the femoral components oversized by two or more sizes. Conclusion: With the introduction of a standardised radiology programme and a stepwise templating technique, the benefits and accuracy of pre-operative templating done in a low-volume, resource-constrained orthopaedic unit is comparable to published data done in high-volume arthroplasty units. Level of evidence: Level 4

Efficacy of conventional method of preoperative templating in implant size selection in patent undergoing total hip arthroplasty

Preoperative templating in total hip arthroplasty is useful in providing details to restore the normal biomechanics and also reduce the guess work. This study was done to asses the efficacy of traditional templating method in the modern times for implant size selection in patient undergoing total hip arthroplasty. We evaluated the accuracy of preoperative templating in 60 primary total hip arthroplasty. Exact size was predicted of 36.6 % acetabulum and 58.3% femoral component. Accuracy was increased to 88.8 % for acetabulum and 90% when one size variation was taken into account. Accuracy of size prediction was better for cemented as compared to uncemented implants. Cemented acetabulum was predicted 54.5% as compared to 26.6% for uncemented implants. Cemented femoral component was predicted in 77.3% vs 47.4% for uncemented femoral stem.

A Novel Method for Accurate Preoperative Templating for Total Hip Arthroplasty Using a Biplanar Digital Radiographic (EOS) System.

Background:Accurate preoperative planning for total hip arthroplasty (THA) relies on conventional anteroposterior radiographs. The difficulty of determining the magnification factor of radiographs is a major limitation. Despite the use of markers for calibration, identifying the plane of the hip joint is a major challenge. The aim of this study was to evaluate the accuracy of a novel method for image calibration and preoperative planning in THA involving the use of a biplanar radiographic (EOS imaging) system and a self-designed coin device.Methods:Biplanar radiographs (with the self-designed coin device) and a conventional anteroposterior radiograph (with a coin) were made for 26 patients after primary THA. The agreement between the actual and calculated diameters for each method was assessed using the concordance correlation coefficient (CCC) and Bland-Altman plots. In addition, 15 patients undergoing primary THA were prospectively enrolled to evaluate the EOS imaging-based method (EOS method), with biplanar radiographs made with use of the coin device. The accuracy of the preoperative predicted size of the implants was evaluated.Results:Both the EOS and conventional anteroposterior radiograph-based methods were reliable in repeated measurements of the diameter of the artificial femoral head in the reproducibility study, with the average CCCs for both methods >0.990. The agreement between the actual and EOS-based calculated diameters of the artificial femoral head was excellent, with a CCC of >0.990, while the agreement was poor between the actual and anteroposterior radiograph-based calculated diameters, with a CCC of <0.75. The EOS method exhibited a lower absolute difference (0.09 ± 0.07 mm) between the actual and calculated diameters compared with conventional anteroposterior radiography (1.26 ± 0.86 mm) (p < 0.001). EOS-based preoperative plans also exhibited excellent performance on the accuracy of the planning of the cups and stems; only 1 patient (6.7%) had a final implanted cup that differed by 1 size from the predicted size. Two patients (13.3%) had final implanted stems that differed by 1 size from the predicted size, and for 1 patient (6.7%), the stem size was off by ≥2 sizes.Conclusions:We describe a novel and easy-to-use method for the accurate calibration of radiographs and preoperative planning for THA. The EOS method evaluated in this study is an alternative method for preoperative planning in clinical practice.

Pre-operative templating in THA. Part I: a classification of architectural hip deformities.

While numerous classifications of hip arthritis have been proposed, none considered the magnitude and direction of femoral head translation relative to the native acetabulum. A more precise classification of architectural hip deformities is necessary to improve preoperative templating and anticipate surgical challenges of total hip arthroplasty (THA). The purpose of the present study was to introduce a classification system to distinguish different types of architectural hip deformities, based on femoral head translation patterns, and to evaluate its repeatability using plain radiographs (qualitative) and Computed Tomography (CT) measurements (quantitative). We studied pre-operative frontal and lateral hip radiographs and CT scans of 191 hips (184 patients) that received primary THA. The distance between the femoral head center (FC) and the acetabular center (AC) was measured, as well as femoral offset, acetabular offset, head center height, acetabular floor distance and femoral neck angle. The hips were classified qualitatively using frontal plain radiographs, and then quantitatively using CT scans (with an arbitrary threshold of 3mm as Centered, Medialized, Lateralized, Proximalized or Proximo-lateralized. The agreement between qualitative and quantitative classification methods was compared for applying the same classification. Qualitative classification identified 120 centered (63%), 8 medialized (4%), 49 lateralized (26%), 3 proximalized (2%), and 11 proximo-lateralized (6%) hips, while quantitative classification identified 116 centered (61%), 8 medialized (4%), 51 lateralized (27%), 5 proximalized (3%), and 11 proximo-lateralized (6%) hips. The agreement between the two methods was excellent (0.94; CI 0.90-0.98). Medialization reached 9.7mm, while lateralization reached 10.9mm, and proximalization reached 8.5mm. Proximalized and proximo-lateralized hips had more valgus necks, while medialized hips had more varus necks (p = 0.003). The classification system enabled repeatable distinction of 5 types of architectural hip deformities. The excellent agreement between quantitative and qualitative methods suggests that plain radiographs are sufficient to classify architectural hip deformities.

Total hip templating using a marker ball (vs. 21% magnification): no difference in accuracy but increase in potential harm

Background: Digital templating for total hip arthroplasty (THA) can help plan the surgical procedure. Magnification marker balls (MB), placed at the time of a digital radiograph have become an acceptable technique to assist with templating despite lack of evidence that they add accuracy. We compared templating accuracy using a standard 21% magnification technique versus a MB. Methods: Two blinded evaluators independently performed retrospective templating on 50 consecutive THA patients. Inter-rater reliability was assessed with interclass correlation coefficients and did not differ across techniques. Accuracy between each templating technique and final implant size was evaluated using Pearson correlations, paired t-tests, and McNemar’s tests. Results: Correlations between final implant size and template estimates were significant and did not differ between techniques. Absolute differences between final size and template estimates also did not differ. Both techniques had equal accuracy within one size of implant size: acetabulum: 62% versus 66%, femur: 78% versus 72%. When differences between templating estimates and actual sizes were examined more minutely, MB yielded a greater rate of 1-size and 2-size larger errors, while 21% magnification yielded a higher rate of 1-size smaller errors. Conclusions: Digital templating using 21% magnification or MB were equally accurate. However, when finer discriminations were made between templating estimates and the final actual size, 21% magnification had better directional accuracy and the advantage of improved clinic efficiency. Using MB, the components tended to be over-estimated, particularly femoral components, which could have a substantial negative impact, especially if the surgeon is trying to match implant with template size.

Radiographic Calibration With a Prosthetic Femoral Head Allows Accurate Preoperative Templating for Total Hip Arthroplasty.

Templating for total hip arthroplasty requires proper radiographic calibration. One option for radiograph calibration is using a cobalt-chrome femoral head ball. The authors reviewed radiographs and clinical data for patients undergoing primary total hip arthroplasty. Radiographs were calibrated using a 28-mm cobalt-chrome femoral head ball. Agreements between templated and actual implant size were calculated. The templated acetabulum matched within one size of the actual acetabulum in 76.7% to 80.0% of cases. The templated femur matched within one size of the actual femur in 83.3% to 93.3% of cases. This technique is an attractive option when a standardized calibration marker is unavailable. [Orthopedics. 2019; 42(3):e346-e349.].

Total Hip Arthroplasty Templating: A Simple Method to Correct for Radiograph Magnification.

Several factors can cause magnification errors when templating. Parallax, distance from the plate, and printing or monitoring the radiographs can lead to errors. Steel balls, 25.4 mm, underwent radiography on a standard radiograph plate in different positions from the center of the x-ray beam for evaluation of parallax and at different heights from the x-ray table for evaluation of the effects of distance on magnification. Difference in size between the center steel ball and the peripheral balls was less than 0.3 mm. As a metal ball was brought from table top to a 6-inch elevation, there was up to a 25% magnification. A simple correction factor can be calculated to correct magnification error. The diameter of the surgically removed femoral head divided by the diameter of the femoral head on the preoperative radiograph yields a correction factor. This factor multiplied by the template-determined lesser trochanter-to-center yields the length to be created during surgery. This adjusts for all causes of magnification. [Orthopedics. 2019; 42(3):e322-e325.].

Templating Hip Arthroplasty.

BACKGROUND:Different methods have been developed and employed with variable degrees of success in pre-operative templating for total hip arthroplasty. Preoperative templating, especially digital templating, has been claimed to have increased the effectiveness of total hip arthroplasty by improving the precision of prediction of prosthetic implant size.AIMS:The overall aim of this systematic review is to identify whether the use of pre-operative templating in total hip arthroplasty procedures has resulted in increased accuracy, reliability and precision of the procedure. Various methods of templating, like traditional acetate overlay and digital method of templating that includes a single radiographic marker and double radiographic marker methods, have been compared to establish the most reliable method of templating.METHODS:We searched the PubMed, Google Scholar Cochrane Central Register of Controlled Trials (CENTRAL), and MEDLINE (1966 to present), EMBASE (1980 to present), CINAHL (1982 to present), Psych INFO (1967 to present) and Clinical Trials Gov.CONCLUSION:The results of this systemic review suggest that preoperative templating is resulting in an enormous increase in the accuracy of total hip arthroplasty and among various methods, King Mark is the most reliable method.

The external obturator footprint as a landmark in total hip arthroplasty through a direct anterior approach: a CT-based analysis.

Anatomical landmarks for templating of total hip arthroplasty (THA) that are visible both during surgery and on radiographs are rare. If surgery is performed through a direct anterior approach the external obturator tendon (EO) is consistently visible. To use this point as a reference the exact position and dimensions of the footprint need to be known. To determine the location and dimension of the EO footprint on pelvic radiographs by correlating the EO anatomy in CT scans with conventional radiographs. CT scans and radiographs of 200 patients were analysed. The EO tendon was identified on CT scans; the height of its footprint, and its distance to the tip of the greater trochanter and to the anatomical axis of the femur was measured. The accuracy and inter-rater reliability in the identification of the EO footprint was determined. The EO tendon was visible on all CT scans and it's footprint was identifiable on all corresponding radiographs. It's cranio-caudal dimension was 6.4 ± 1.4 mm. It's distance to the tip of the greater trochanter was 16.0 ± 3.1 mm. The EO footprint was located 5.2 ± 3.7 mm lateral to the femoral anatomical axis. There was no significant difference regarding the accuracy of EO footprint localisation on radiographs among the 2 readers. The EO footprint on the greater trochanter is consistently visible on CT scans and radiographs. As the variability of the footprint dimension is small, this structure may serve as a useful landmark in THA, particularly when performed through a direct anterior approach.

Is computerised 3D templating more accurate than 2D templating to predict size of components in primary total hip arthroplasty?

The aim of this study was to compare the accuracy of preoperative templating in total hip arthroplasty (THA) using conventional 2-dimensional (2D) and computed tomography (CT)-based 3-dimensional (3D) measures. One hundred and sixteen consecutive primary THAs were analysed. The preoperative diagnosis was primary osteoarthritis in all cases. The 2D templating and the 3D templating were performed by two different residents. All templating results were available for the orthopaedic surgeon performing the procedure. Accuracies with regard to the predicted and actual implant sizes were determined for each procedure. Implantation of the size as planned was defined as "exact", whereas the use of components within one size larger or smaller (±1) as planned were defined as "accurate." The 3D templating was significantly more accurate in predicting implant sizing compared to 2D templating for primary total hip arthroplasty (THA). The difference was statistically significant for the cup templating (''exact'' p = 0.02; ''accurate'' p = 0.01) and for the stem templating (''exact'' p = 0.04; ''accurate'' p = 0.01). Our results support the superiority of 3D templating over 2D templating in predicting implant size.

Accuracy of predictive magnification factor for preoperative templating in total hip arthroplasty

Accuracy of predictive magnification factor for preoperative templating in total hip arthroplasty

Scaling Marker Position Determines the Accuracy of Digital Templating for Total Hip Arthroplasty.

Digital templating systems foster patient-specific measurements for preoperative planning. We aim (1) to verify the accuracy of a templating system, (2) to describe the effects of scaling marker position on the accuracy of digital templating of the hip, and (3) to provide a practical guide for scaling marker position using patient body mass index (BMI). A scaling sphere was placed in five positions along the anterior-posterior axis of an acetabular implant and pelvis phantom, and x-rays were obtained. Each radiograph was templated for the acetabular component and recorded. A retrospective review identified CT scans of preoperative hip arthroplasty cases. The center of the greater trochanter was calculated from these CT scans as the percent distance from the anterior thigh and recorded with the patient's BMI. By centering the scaling sphere on the acetabular component, an accurate cup size was achieved. A difference of 3.5cm in sphere placement resulted in a full cup size magnification error. Positioning the scaling sphere at the level of the pubic symphysis resulted in a difference of four cup sizes. This patient population had an average BMI of 28.72kg/m2 (standard deviation 6.26kg/m2) and an average position of the center of the greater trochanter of 51% (standard deviation of 6%) from the anterior surface of thigh. Digital templating relies on scaling marker position to accurately estimate implant size. Based on the findings in this study, scaling markers for hip imaging should be placed laterally, mid-thigh in the anterior-posterior direction for patients with a BMI between 25 and 40kg/m2. If abnormal hip anatomy or extremes of BMI are discovered, then scaling sphere positioning should be optimized on a case-by-case basis. Digital templating systems for total hip arthroplasty must use precisely placed scaling markers at the level of the hip joint to allow for accurate implant size estimation.

Interobserver and Intraobserver Reliability of Three-Dimensional Preoperative Planning Software in Total Hip Arthroplasty

BackgroundThe purpose of this study is to clarify interobserver and intraobserver reliabilities of the three-dimensional (3D) templating of total hip arthroplasty (THA). MethodsWe selected preoperative computed tomography from 60 hips in 46 patients (14 men and 32 women) who underwent primary THA. To evaluate interobserver and intraobserver reliability, 6 orthopedic surgeons performed 3D templating twice over a 4-week interval. We investigated intraclass correlation coefficients (ICCs) and percent agreement of component size and alignment, comparing morphological differences in the hip. Reproducibility was also compared between groups with osteoarthritis (OA) and those with osteonecrosis (ON). ResultsThe interobserver reliabilities for mean cup size and stem size were excellent, with ICC = 0.907 and 0.944, respectively. The value was significantly higher in the ON group than in the OA group. In the OA group, the reliability of cup size and alignment decreased in hips with severe subluxation. Percent agreement of stem size was significantly different between the shapes of femoral canal. For intraobserver reliability, the mean ICC of cup size was 0.965 overall, while the value in the ON group was significantly higher than in the OA group. The mean ICC of stem size was 0.972 overall. ConclusionComputed tomography–based 3D templating showed excellent reliability for component size and alignment in THA. Deformity of the affected joint influenced the reliability of preoperative planning.

Templating digital radiographs using acetate templates in Total Hip Arthroplasty

Introduction & objectivePreoperative templating in Total Hip Arthroplasty (THA) has traditionally been done with conventional radiographs. With conventional films being replaced by digital films, it has become difficult for surgeons to template the hip preoperatively, as digital templating involves special software, carries an additional cost and is not freely available. We describe a hybrid technique that involves the use of standard acetate templates, used over digital radiographs on a LCD monitor. Materials and methodsPreoperative digital radiographs of the pelvis were taken with a 30mm diameter spherical metal ball taped onto the greater trochanter. Viewing the digital radiographs on a flat screen LCD monitor, the metal ball on the image was magnified to 30mm as per the scale on the acetate template. The size of the acetabular cup and the femoral stem were then directly read using standard techniques with the acetate templates. To assess accuracy, digital films of 54 hips were retrospectively templated and the estimated size of the implant was compared with the actual size used at surgery. Reliability of the method was tested with Intraclass Correlation Coefficient (ICC). ResultsUsing this technique, it was possible to accurately predict the acetabular cup size in 38/54 (70%) of the hips and to within 1 size in 96% of the hips. The femoral component size was accurately predicted in 24/54 (44%) of the hips and to within 1 size in 82% of the hips. When assessed by two independent observers, there was good intraobserver reliability (ICC value=0.96) and interobserver reliability (ICC value=0.93) for the acetabular templating as well as for the femur (ICC value of 0.93 for intraobserver reliability and ICC value of 0.88 for interobserver reliability). ConclusionIt was possible to accurately and reliably predict the size of the acetabular cup and the femoral stem, using standard acetate onlay templates on digital radiographs, without the use of digital templating software.

Prospective, Randomized, Surgeon-Blinded Comparison of Standard Magnification Assumption vs Magnification Marker Usage for Preoperative Templating in Total Hip Arthroplasty

BackgroundWe undertook this prospective, randomized, surgeon-blinded study to compare the accuracy of using of a magnification marker on preoperative radiographs for templating vs using a standard 21% magnification. MethodsOne hundred consecutive total hip arthroplasties were randomized to preoperative templating using a 25-mm magnification marker (50 patients) or a standard 21% magnification (50 patients). Intraoperative data were collected regarding the actual and predicted size of the femoral and acetabular components. ResultsThe 2 groups were found to be comparable with respect to body mass index (28.9 vs 27.9, P = .26) and gender (P = .69). In the magnification marker group, we predicted the femoral size within 1 size in 80% of the cases and the acetabular component in 94%. In the group of a standard 21% magnification, we predicted the femoral size within 1 size in 90% of the cases and the acetabular component in 96%. These proportions did not statistically differ (femur: χ2P = .16, odds ratio = 2.3, 95% confidence interval = 0.7-7.1; acetabulum: χ2P = .65, odds ratio = 1.5, 95% confidence interval = 0.3-9.6). ConclusionWe did not detect a statistically significant difference in accuracy by using one method over the other when comparing the accuracy of component size selection. As the use of the magnification marker adds to the time and expense of preoperative radiographic acquisition, we feel using a standard 21% magnification is an equally accurate technique.