Preoperative Templating Research Articles

Smart Technology and Orthopaedic Surgery: Current Concepts Regarding the Impact of Smartphones and Wearable Technology on Our Patients and Practice.

While limited to case reports or small case series, emerging evidence advocates the inclusion of smartphone-interfacing mobile platforms and wearable technologies, consisting of internet-powered mobile and wearable devices that interface with smartphones, in the orthopaedic surgery practice. The purpose of this review is to investigate the relevance and impact of this technology in orthopaedic surgery. Smartphone-interfacing mobile platforms and wearable technologies are capable of improving the patients' quality of life as well as the extent of their therapeutic engagement, while promoting the orthopaedic surgeons' abilities and level of care. Offered advantages include improvements in diagnosis and examination, preoperative templating and planning, and intraoperative assistance, as well as postoperative monitoring and rehabilitation. Supplemental surgical exposure, through haptic feedback and realism of audio and video, may add another perspective to these innovations by simulating the operative environment and potentially adding a virtual tactile feature to the operator's visual experience. Although encouraging in the field of orthopaedic surgery, surgeons should be cautious when using smartphone-interfacing mobile platforms and wearable technologies, given the lack of a current academic governing board certification and clinical practice validation processes.

The Effect of Femoral Malrotation in Offset Templating for Total Hip Arthroplasty: A Cadaveric Study and Curvilinear Analysis

AbstractTechniques allow assessment of preoperative offset in hip arthroplasty. This study assessed femoral rotation in preoperative offset templating using a cadaveric model. Ten femurs were imaged at degrees of rotation. Offset was measured. A generalizable equation predicting change in offset was derived with a curvilinear model. Statistically significant differences at rotational positions were found. For 30 degrees of internal rotation, 2.1 mm change in adjusted mean offset existed; for 30 degrees of external rotation, 8.4 mm change existed. Improved awareness of malrotation of the proximal femur and templating adjustments may improve total hip arthroplasty outcomes. This study reflects level of evidence III.

Using MRI Measurement to Improve Accuracy of Femoral Component Sizing in Oxford Unicompartmental Knee Arthroplasty.

Unicompartmental knee arthroplasty (UKA) can achieve better kinematics and faster recovery than total knee arthroplasty. The Phase III Oxford UKA system has five sizes of femoral components to approximate the normal knee geometry. However, these different sizes may also induce problems, such as the misselection of component size. Different criteria have been proposed to predict the ideal size preoperatively. However, no single method can be applied universally. Therefore, this study aimed to develop a preoperative measurement using knee magnetic resonance imaging (MRI) to predict femoral component size. A total of 68 patients who underwent UKA were investigated from June 2019 to April 2020. 16 knees using a different MRI protocol were excluded. We developed an MRI measurement method to determine femoral size instead of gender- and height-based methods. The accuracy of different methods was compared using postoperative true lateral view radiographs. Three different kinds of gender- and height-based criteria, preoperative templating and intraoperative spoon measurement were compared. The accuracy of MRI measurement was 90.3%. Therefore, a significant difference was found between MRI measurements and all other methods, such as templating or gender- and height-based methods. In conclusion, the MRI measurement method can be concluded to accurately predict femoral component size in UKA. This method could be used regardless of different ethnic groups, individual knee geometry, or soft tissue tension.

Anterior Closing Wedge Proximal Tibial Osteotomy and Revision Anterior Cruciate Ligament Reconstruction With Quadriceps Tendon Autograft

Background: Anterior cruciate ligament (ACL) ruptures are among the most common injuries in young athletes and active adults. Reconstruction of the ACL most often leads to good functional outcomes and return to full activities. However, a number of patients experience ACL graft failures requiring revision surgery. The reasons for ACL graft failure are often multifactorial, though recent attention has been given to elevated posterior tibial slope (PTS) as a risk factor for recurrent ACL injuries. Indications: In patients with 2 or more ACL reconstruction failures with a PTS ≥12 degrees, anterior closing wedge proximal tibia osteotomy (ACWPTO) may be indicated to reduce the risk of recurrent ACL graft failure and allow return to full activities. Technique Description: This surgical technique video demonstrates the ACWPTO using a case example in a young athlete. Preoperative templating on lateral radiograph is used to determine the amount of correction for the closing wedge. The osteotomy is completed using K-wires and a free hand biplanar cutting technique with the tibial tubercle left in place. This is performed with a concomitant revision ACL reconstruction using quadriceps tendon autograft. Results: There are 2 small cases series published with good clinical outcomes and return to sport activities. No ACL graft failures were reported in either study with short-term follow-up. Discussion: In this surgical technique video, we review the literature indicating elevated PTS as a risk factor in ACL injuries and recurrent ACL graft failures. We highlight important technique pearls and pitfalls to avoid complications during the surgical demonstration. Finally, we review postoperative rehabilitation guidelines and clinical outcomes within the existing literature. In patients with recurrent ACL graft failures, ACWPTO provides a safe and reliable technique to correct an elevated PTS and return patients back to full activities with reduced risk of ACL graft re-tear.

Forehead Flap Templates for Nasal Reconstruction Digitally Developed From 2D and 3D Images.

The forehead flap is the gold standard procedure for nasal reconstruction to address a partial or complete rhinectomy. Traditionally, the three-dimensional (3D) nasal defect is manually templated intraoperatively to design the two-dimensional (2D) flap shape on intact morphology. In this clinical study, digital preoperative planning is used to template with computer-assisted design and manufacturing. Preoperative digital templates were implemented for 3 representative patients (1 in Supplementary Digital Content, http://links.lww.com/SCS/D60). This includes designs for a hemi-rhinectomy case from 3D mirroring, a partial total rhinectomy case generated from a 3D scan, and a total rhinectomy case generated from a 3D morphable model based on a prepathology 2D photo. Digital unwrapping flattened the patient's 3D nasal geometry designs to 2D skin flap shapes. Finally, the 2D designs were printed as traceable intraoperative templates at a 1:1 scale. This clinical study demonstrates the application of digital 3D preoperative templating to improve workflow for nasal reconstruction.

Preoperative planning of total knee arthroplasty: reliability of axial alignment using a three-dimensional planning approach.

Preoperative templating of total knee arthroplasty (TKA) can nowadays be performed three-dimensionally with software solutions using computed tomography (CT) datasets. Currently there is no consensus concerning the axial orientation of TKA components in three-dimensional (3D) planning. To assess intra-/inter-observer reliability of detection of different bony landmarks in planning axial component alignment using axial CT images and 3D reconstructions. Intra- and inter-observer reliability of determination of four predefined axial femoral and tibial axes was calculated using data from CT scans. Axes determination was performed on the axial slices and on the 3D reconstruction using preoperative planning software. In summary, 61 datasets were analyzed by one medical student (intra-observer reliability) and 15 datasets were analyzed by four different observers independently (inter-observer reliability). For the femur, clinical epicondylar axis and posterior condylar axis showed the best reliability with an inter-observer variability of 0.7° and 0.5°, respectively. For the tibia, posterior condylar axis provided best reliability (inter-observer variability: 1.7°). Overall variability was greater for tibial than for femoral axes. Reliability of axis determination was more accurate using axial CT slices rather than 3D reconstructions. The femoral clinical epicondylar axis is highly reliable. Landmarks for the tibia are not as easily identifiable as for the femur. The tibial posterior condylar axis presents the axis with highest reliability. Based on these results, clinical epicondylar axis for orientation of the femoral TKA component and posterior condylar axis for the tibial implant, both defined on axial slices can be recommended.

Radiographic Assessment of the Proximal Femoral Anatomy in An Indigenous African Adult Population

Background: Hip surgeries such as fracture fixation, corrective osteotomy, hemiarthroplasty, or total hip arthroplasty require accurate preoperative templating for a successful outcome. Such templating is done using the proximal femur and the acetabulum radiographs, depending on the planned surgery. Understanding the normal radiographic anatomy of the proximal femur is crucial to differentiate a normal from pathological anatomy. Proximal femoral anatomic indices include the femoral head diameter, femoral neck diameter, femoral neck length, femoral offset, femoral neck axis length and the femoral neck-shaft angle. Aim: This study assesses and establishes the average values of the proximal femoral anatomy in an indigenous African adult population. Method: This cross-sectional study examined 190 normal anteroposterior (AP) radiographs of the pelvis. The mean age, weight and height of the subjects were obtained. The following proximal femoral anatomic parameters were measured: femoral neck length (FNL), femoral neck diameter (FND), femoral head diameter (FHD), femoral neck-shaft angle (FNSA), femoral offset (FO) and femoral neck axis length (FNAL). The authors compared the mean difference of the parameters between the genders and the age categories and assessed the parameter correlations with the patients’ weight and height. Results: Males constituted 63 (33.2%) of the study population. The mean age of the subjects was 51.46 years (SD = 16.37). The mean weight was 76.13 kg, while the mean height was 1.62 m. The mean values of the proximal femoral parameters were as follows: FNL 4.52cm, FND 3.42cm, FHD 4.76cm, FNSA 132.960, FO 4.09cm, and FNAL 10.34cm. Males have a significantly higher mean value in all the parameters except the FO. None of the parameters showed any significant difference among the age categories except the FNL. A post-hoc analysis showed that the difference in the FNL lies between the young and the elderly age groups. The subjects’ height correlated with all the parameters except FNSA, while the weight correlated with the FND, FNSA and FNAL. Conclusion: The proximal femoral anatomy in Africans differed from those published in foreign literature. This knowledge is crucial for implant manufacturing companies and preoperative templating for hip surgeries. KEY WORDS: Proximal femur, Anatomy, Black population.

Digital templating for the implantation of a curved short hip stem with an anterolateral MIS approach shows gender differences in digital templating

PurposeDigital templating shows reliable accuracy for straight stem systems. In recent years, the implantation of short stems through minimally invasive approaches has gained more popularity. Minimally invasive approaches (MIS) show the risk of undersizing femoral components. Therefore, we questioned the planning adherence for a curved short stem and a bi-hemispherical acetabular cup implanted through an anterolateral MIS approach.MethodsA consecutive series of 964 hips (index surgery between 2014 and 2019) with Fitmore® curved short stem and Allofit/-S® acetabular cup (both ZimmerBiomet Inc, Warsaw, IN) were included. Preoperative digital templating was conducted anterior–posterior (AP) digital radiographs of the hip using mediCAD® version 5.1 (Hectec GmbH, Altdorf, Germany). The templates of acetabular and femoral components (offset option and stem size) were retrospectively evaluated for general adherence, and according to sex, BMI and planner’s experience.ResultsPlanning adherence for the exact offset option was 70.6 and 21.6% for exact offset option and stem size. Adherence for acetabular cup ± 1 size was 74.8%. A significant difference between male and female patients for the offset option could be found (p = 0.03, z = −2983). In 22.5% of male patients, an offset option one size higher and in 12.3% of female patients an offset option one size smaller than templated was used intraoperativelyConclusionDigital templating for the Fitmore® stem in cementless THA with a minimally invasive anterolateral approach shows comparable planning adherence to the existing literature for this cementless short stem. However, a lower planning adherence was detected compared to conventional straight stem systems. In male patients, the femoral offset is frequently undersized and in female patients frequently oversized compared to the preoperative plan. Surgeons should be aware of this difficulty in digital templating for Fitmore® hip stem.

A Novel Measurement Using Digital Radiography to Minimize Fluoroscopy in Total Hip Arthroplasty

AbstractPreoperative templating for total hip arthroplasty (THA) is fraught with uncertainty. Specifically, the conventional measurement of the lesser trochanter to the center (LTC) of the femoral head used in preoperative planning is easily measured on a template but not measurable intraoperatively. The purpose of this study was to examine the utility of a novel measurement that is reproducible both on templating and in surgery as a more accurate and practical guide. We retrospectively reviewed 201 patients with a history of osteoarthritis who underwent primary THA. For preoperative templating, the distance from the top of the lesser trochanter to the equator (LeTE) of the femoral head was measured on a calibrated digital radiograph with a neutral pelvis. This measurement was used intraoperatively to guide the choice of the trial neck and head. As with any templating technique, the goal was to construct a stable, impingement-free THA with equivalent leg lengths and hip offset. In evaluating this novel templating technique, the primary outcomes measured were the number of trial reductions and the amount of fluoroscopic time, exposures, and radiation required to obtain a balanced THA reconstruction. Using the LeTE measurement, the mean number of trial reductions was 1.21, the mean number of intraoperative fluoroscopy images taken was 2.63, the mean dose of radiation exposure from fluoroscopy was 0.02 mGy, and the mean fluoroscopy time per procedure was 0.6 seconds. In hips templated with the conventional LTC prior to the LeTE, the mean fluoroscopy time was 0.9 seconds. There was a statistically significant difference in fluoroscopy time (p < 0.001). The LeTE is a reproducible measurement that transfers reliably from digital templating to surgery. This novel preoperative templating metric reduces the fluoroscopy time and consequent radiation exposure to the surgical team and may minimize the number of trial reductions.

A novel approach to 3D bone creation in minutes : 3D ultrasound.

AimsThe objective of this study is to assess the use of ultrasound (US) as a radiation-free imaging modality to reconstruct 3D anatomy of the knee for use in preoperative templating in knee arthroplasty.MethodsUsing an US system, which is fitted with an electromagnetic (EM) tracker that is integrated into the US probe, allows 3D tracking of the probe, femur, and tibia. The raw US radiofrequency (RF) signals are acquired and, using real-time signal processing, bone boundaries are extracted. Bone boundaries and the tracking information are fused in a 3D point cloud for the femur and tibia. Using a statistical shaping model, the patient-specific surface is reconstructed by optimizing bone geometry to match the point clouds. An accuracy analysis was conducted for 17 cadavers by comparing the 3D US models with those created using CT. US scans from 15 users were compared in order to examine the effect of operator variability on the output.ResultsThe results revealed that the US bone models were accurate compared with the CT models (root mean squared error (RM)S: femur, 1.07 mm (SD 0.15); tibia, 1.02 mm (SD 0.13). Additionally, femoral landmarking proved to be accurate (transepicondylar axis: 1.07° (SD 0.65°); posterior condylar axis: 0.73° (SD 0.41°); distal condylar axis: 0.96° (SD 0.89°); medial anteroposterior (AP): 1.22 mm (SD 0.69); lateral AP: 1.21 mm (SD 1.02)). Tibial landmarking errors were slightly higher (posterior slope axis: 1.92° (SD 1.31°); and tubercle axis: 1.91° (SD 1.24°)). For implant sizing, 90% of the femora and 60% of the tibiae were sized correctly, while the remainder were only one size different from the required implant size. No difference was observed between moderate and skilled users.ConclusionThe 3D US bone models were proven to be closely matched compared with CT and suitable for preoperative planning. The 3D US is radiation-free and offers numerous clinical opportunities for bone visualization rapidly during clinic visits, to enable preoperative planning with implant sizing. There is potential to extend its application to 3D dynamic ligament balancing, and intraoperative registration for use with robots and navigation systems.Cite this article: Bone Joint J 2021;103-B(6 Supple A):81–86.

The Accuracy and Ability of Preoperative Templating to Restore Femoral Offset in Calcar-Guided Short-Stem Total Hip Prosthesis through Direct Anterior Approach

AbstractThe aim of this study was to assess the applicability and ability of preoperative templating to restore femoral offset and hip length with a calcar-guided short-stem implant design in total hip arthroplasty through the direct anterior approach. Preoperative measurements were performed of femoral offset, hip length, and stem size and compared with the perioperative placed prosthesis in 100 patients undergoing primary total hip replacement through direct anterior approach. Additionally, the pre- and postoperative femoral offset and hip length were compared to evaluate the ability to restore the offset and hip length with this kind of femoral short stem. With an acceptance of 1 size difference pre- and postoperatively, a 94% accuracy of predicting the size of the calcar-guided short stem was achieved with templating. Femoral offset was within means of 5 mm in 82.2% of the patients. Postoperative hip length was within 6 mm in 90% of the patients compared with the preoperative length.The use of preoperative templating for total hip arthroplasty with calcar-guided short-stem implants was proven to be a useful tool to predict the definite implanted size of the femoral prosthesis. Our results show that this new stem design does not significantly differ from previous reported outcomes with other stem designs and is competent to restore the femoral offset and hip length within clinical acceptable range. Level of evidence Level 3 retrospective case study.

480 Preoperative Templating in Hip Hemiarthroplasty Improves Femoral Offset and Function

Abstract The use of preoperative templating for hip hemiarthroplasty increases the likelihood of successfully restoring offset. This study sought to identify whether templating improves radiographic and clinical outcomes in this group. Data belonging to all patients that underwent hip hemiarthroplasty between March 2018 and March 2019 were collected. The patients were grouped based on whether or not their preoperative images were templated. Radiographs were studied retrospectively to calculate preoperative and postoperative offset and LLD for each patient. The clinical outcomes that were measured included the rate of periprosthetic fracture, dislocation and contra-lateral neck of femur fracture for each group. Data was analysed by SPSS. There were 208 patients of which 72 were templated and 136 not templated. The percentage difference between the preoperative and postoperative offset was lower in the templated group (p < 0.05). There was no significant difference in radiographic LLD between the two groups. There was no significant difference in the clinical outcomes between the two groups. A significantly closer restoration to the original offset was achieved with preoperative templating, which is likely to improve function in this group. There were no significant differences in the other clinical outcomes between the two groups.

The Rate of Correctly Planned Size of Digital Templating in Two Planes—A Comparative Study of a Short-Stem Total Hip Implant with Primary Metaphyseal Fixation and a Conventional Stem

(1) Background: Preoperative templating is mainly conducted on an anteroposterior pelvic overview X-ray. For short stem hip arthroplasty, the choice of the optimal size is especially crucial to avoid complications. Thus, the study aimed to determine if there is an increased rate of correctly planned sizes using two radiological planes. (2) Methods: 50 patients with a conventional stem and 100 with a short stem total hip arthroplasty were analyzed. Without knowing the implanted size, three independent orthopedic surgeons performed digital templating: once using the anteroposterior pelvic overview only and once using the lateral view in addition. (3) Results: The rate of correctly planned sizes (+/−1 size compared to the inserted size) of templating with one plane was 86.3% ± 9.5% in short stem hip arthroplasty and 88.4% ± 6.0% in conventional stem arthroplasty. By adding the lateral view, the rate of correctly planned sizes was 89.9% ± 12.0% for the short stem hip arthroplasty group and 89.4% ± 9.8% for the conventional group (p > 0.1). (4) A potential positive effect of preoperative templating using an additional lateral X-ray view for short stem implants may be suggested based on the results of this study, which did, however, not reach statistical significance.

Morphological variations in proximal femoral nails in Indian scenario and its clinical application

Background: There is an increasing trend of use of cephalomedullary nail for the management of both stable and unstable intertrochanteric and subtrochanteric femoral fractures. Various western and Indian proximal femoral nails with different morphologies are available in Indian market that sometimes creates confusion amongst orthopedic surgeons about which nail to be preferred in different clinical scenarios for accurate outcomes. Material and Methods: Ten different types of long femoral nails with 10 mm diameter (5 Western and 5 Indian) available in Indian market were taken and the morphology of these were studied and compared for 9 parameters. Results: A lot of variation was seen amongst the Indian nails and western nails in proximal diameter, shape of proximal part of nail, distance of lag screw from tip, distance at which actual size of nail becomes 10mm, M-L angle (medio lateral angle), shape of nail shaft, configuration of distal screws, morphology of neck screw and centrum-collum –diaphyseal (CCD) angle. Conclusion: Design of a nail may prove to be superior in some type of patients and fractures but may not be suitable for others. Pre-operative templating is must and surgeons need to consider all the factors in unison while deciding the type of nail to be used. Keywords: Intertrochantric fractures, Proximal femoral nail.

A Simple Procedure for a Common Problem: Screw/Blade Exchange for Symptomatic Lateral Hardware Associated With Fracture Compression Following Dynamic Cephalomedullary Fixation of Pertrochanteric Hip Fractures

A Simple Procedure for a Common Problem: Screw/Blade Exchange for Symptomatic Lateral Hardware Associated With Fracture Compression Following Dynamic Cephalomedullary Fixation of Pertrochanteric Hip Fractures

Is the contralateral lesser trochanter a reliable reference for planning of total hip arthroplasty \u2013 a 3-dimensional analysis

BackgroundPreoperative templating in total hip arthroplasty (THA) is mandatory to achieve appropriate offset and leg length equality. However, templating methods using the contralateral hip might be susceptible to errors resulting from side-differences in the femoral morphology. The distance of the lesser trochanter to the femoral head center (LTFHD) is a frequently used reference parameter for preoperative planning and intraoperative validation during THA. However, currently no three-dimensional (3D) analysis of side differences of the LTFHD exists.MethodsUsing Computer tomography (CT)-based surface models from 100 paired femora (50 cadavers), side-to-side asymmetry of the LTFHD, femoral length, femoral head diameter (FHD) and femoral antetorsion were analyzed. Univariate linear regression models were established to evaluate potential associations between sides regarding LTFHD and FHD as well as a correlation of these parameters with each other.ResultsStatistically significant side-differences were found for the LTFHD (p = 0.02) and FHD (p = 0.03) with a mean absolute side-difference of 1.6 ± 1.4mm (range 0.1–5.5mm) and 0.4mm ± 0.6mm (range 0–3mm), respectively. The ratio between the LTFHD and FHD was consistent with an average value of 1.16 ± 0.08 and reliable between sides with a correlation coefficient (r) of 0.72 (p < 0.01).ConclusionsThe LTFHD is a reliable reference parameter for preoperative templating and intraoperative validation during THA with a high correlation between sides (r = 0.93, p < 0.01). However, 8 % of the investigated specimens revealed a LTFHD of more than 4mm, which should be anticipated during THA to avoid unsatisfiable results.

Advanced Templating for Total Shoulder Arthroplasty.

Longitudinal clinical and radiographic success of total shoulder arthroplasty (TSA) is critically dependent on optimal glenoid component position. Historically, preoperative templating utilized radiographs with commercially produced overlay implant templates and a basic understanding of glenoid morphology. The advent of 3-dimensional imaging and templating has achieved more accurate and precise pathologic glenoid interrogation and glenoid implant positioning than historical 2-dimensional imaging. Advanced templating allows for the understanding of unique patient morphology, the recognition and anticipation of potential operative challenges, and the prediction of implant limitations, and it provides a method for preoperatively addressing abnormal glenoid morphology. Synergistic software, implants, and instrumentation have emerged with the aim of improving the accuracy of glenoid component implantation. Additional studies are warranted to determine the ultimate efficacy and cost-effectiveness of these technologies, as well as the potential for improvements in TSA outcomes.

Machine Learning Predicts Femoral and Tibial Implant Size Mismatch for Total Knee Arthroplasty.

BackgroundDespite reasonable accuracy with preoperative templating, the search for an optimal planning tool remains an unsolved dilemma. The purpose of the present study was to apply machine learning (ML) using preoperative demographic variables to predict mismatch between templating and final component size in primary total knee arthroplasty (TKA) cases.MethodsThis was a retrospective case-control study of primary TKA patients between September 2012 and April 2018. The primary outcome was mismatch between the templated and final implanted component sizes extracted from the operative database. The secondary outcome was mismatch categorized as undersized and oversized. Five supervised ML algorithms were trained using 6 demographic features. Prediction accuracies were obtained as a metric of performance for binary mismatch (yes/no) and multilevel (undersized/correct/oversized) classifications.ResultsA total of 1801 patients were included. For binary classification, the best-performing algorithm for predicting femoral and tibial mismatch was the stochastic gradient boosting model (area under the curve: 0.76/0.72, calibration intercepts: 0.05/0.05, calibration slopes: 0.55/0.7, and Brier scores: 0.20/0.21). For multiclass classification, the best-performing algorithms had accuracies of 83.9% and 82.9% for predicting the concordance/mismatch of the femoral and tibial implant, respectively. Model predictions of greater than 51.0% and 47.9% represented high-risk thresholds for femoral and tibial sizing mismatch, respectively.ConclusionsML algorithms predicted templating mismatch with good accuracy. External validation is necessary to confirm the performance and reliability of these algorithms. Predicting sizing mismatch is the first step in using ML to aid in the prediction of final TKA component sizes. Further studies to optimize parameters and predictions for the algorithms are ongoing.

Pre-operative templating for total hip arthroplasty: How does radiographic technique and calibration marker placement affect image magnification?

IntroductionPre‐operative templating using digital radiography is an effective method of planning for total hip arthroplasty (THA) and requires a generalised fixed magnification factor (MF) or external calibration markers (ECM). The effect on image magnification when changing source‐to‐image distance (SID), object‐to‐image distance (OID) and different imaging conditions is not well described. This study aims to quantify the range of effects manipulation of radiographic parameters can have on image magnification across different body habitus and imaging conditions.MethodsA simple phantom study was performed. A 25 mm ECM was placed at eight different OID values along the anterior–posterior phantom plane at three different SID values and imaging conditions, and X‐rays were obtained. On each radiograph, the ECM was measured using a line calliper tool by three radiographers and recorded. The MF was calculated and recorded.ResultsThe smallest observed image MF was 1.16, for an 8 cm OID, 120 cm SID with the ECM placed within the central ray and the X‐ray detector in bucky underneath the X‐ray table. The largest image MF was 1.40 for a 15 cm OID, 100 cm SID with the X‐ray detector placed underneath an emergency department imaging trolley.ConclusionsDigital pre‐operative templating for THA relies on accurate radiographic positioning and is dependent of the patient body habitus, radiographic parameters and imaging conditions selected by the radiographer. The use of appropriately positioned ECMs – placed medially between the patient’s internally rotated legs at the level of the greater trochanter, lowers the potential for magnification inaccuracies.

Response to Letter to the Editor, "Who Restores Hip Biomechanics More Effectively After a Femoral Neck Fracture? Comparison of Total Hip Arthroplasties Performed Either by Hip Surgeons or Orthopedic Residents".

Response to Letter to the Editor, "Who Restores Hip Biomechanics More Effectively After a Femoral Neck Fracture? Comparison of Total Hip Arthroplasties Performed Either by Hip Surgeons or Orthopedic Residents".