Introduction. Uncemented components necessitate accurate intraoperative assessment of size to avoid complications such as calcar fracture and subsidence whilst maintaining bone stock on the acetabular side. Potential problems can be anticipated pre-operatively with the use of a templating system. We proposed that pre-operative digital templating could accurately assess femoral and acetabular component size. Methods. Pre-operative templating data from 100 consecutive patients who received uncemented implants (Trident cup, Accolade stem) and who were operated on by the senior author were included in the study. Calibrated pelvis anterior-posterior X-rays were templated with Orthoview™ software. Demographic data, templating data (stem and cup size, femoral neck cut), operative records (actual stem and cup size, head size) and post-operative data (femoral stem alignment, radiographic leg length, acetabular cup abduction angle) were collected. Results. There were 51 males and 49 females with a mean age of 60 yrs (SD = 7.3 yrs). Seventy five percent of stems were templated to within 0.5 size and 98% to within 1 size. A total of 80% of cups were templated to within 2mm and 98% to within 4mm. 62% of head length was accurately template. Seven patients were converted from a templated 132° to a 127° femoral prosthesis neck angle. The acetabulum cup abduction angle was 45° (SD = 4.81) and stem alignment was 1.5° (SD = 1.13). The mean lower limb length discrepancy was +0.05mm (SD = 5.1 mm) post-operatively. Conclusion. Digital templating is a accurate method of assessing femoral and acetabular component sizes. This allows surgeons to foresee potential problems and also recognize an intra-operative error when a large discrepancy exists between a trial component and the templated size

With the advent of digital radiology, our institution has introduced digital templating for preoperative planning of total hip arthroplasty (THA). Prior studies of the accuracy of digital templating had contradictory results. This study compares the accuracy of digital and analog templating for THA. Ninety patients were recruited. Sixty-eight patients had analog pre-operative templating while 22 patients had digital templating. A retrospective review of medical records obtained the sizes of hip implants inserted during THA and patient demographics. The templated hip sizes were compared with the actual hip implants inserted. Accuracies of both templating methods were compared in four outcomes: prediction of acetabular cup size, prediction of femoral stem size, prediction of femoral offset and prediction of femoral neck length. Digital templating was more accurate than analog templating in predicting acetabular cup size, femoral stem size and femoral offset. Analog templating was more accurate in predicting femoral neck length. However, only the comparison of femoral offset achieved statistical significance (p-value = 0.049). After stratifying the data by BMI, digital templating was more accurate than analog templating in predicting acetabular cup and femoral stem sizes for patients with high BMI. For patients with BMI = 25-30, accuracy of digital templating was 100.0% for cup and 80.0% for stem while accuracy of analog templating was 74.1% for cup and 74.1% for stem. For patients with BMI > 30, accuracy of digital templating was 84.6% for cup and 69.2% for stem while that of analog templating was 75.0% for cup and 66.7% for stem. Digital templating outperformed analog templating in all the outcomes except femoral neck length. In addition, digital templating was significantly more accurate in predicting femoral offset. This study showed that digital templating has the potential to reduce errors in pre-operative planning for THA

Background. Digital templating is a critical part of preoperative planning for total hip arthroplasty (THA) that is increasingly used by orthopaedic surgeons as part of their preoperative planning process. Digital templating has been used as a method of reducing hospital costs by eliminating the need for acetate films and providing an accurate method of preoperative planning. Pre-operative templating can help anticipate and predict appropriate component sizes to help avoid postoperative leg length discrepancy, failure to restore offset, femoral fracture, and instability. A preoperative plan using digital radiographs for surgical templating for component size can improve intraoperative accuracy and precision. While templating on conventional and digital radiographs is reliable and accurate, the accuracy of templating on digital images acquired with a novel biplanar imaging system (EOS Imaging Inc, Cambridge, MA, USA) remains unknown. EOS imaging captures whole body images of a standing patient without stitching or vertical distortion, less magnification error and exposes patients to less radiation than a pelvis AP radiograph. Therefore, the purpose of this study was to compare EOS imaging and conventional anteroposterior (AP) xrays for preoperative digital templating for THA, and compare the results to the implant sizes used intraoperatively. Methods. Forty primary unilateral THA patients had preoperative supine AP xrays and standing EOS imaging. The mean age for patients was 61 ± 8 years, the mean body mass index 29 ± 6 kg/m. 2. and 21 patients were female. All patients underwent a THA with the same THA system (R3 Acetabular System and Synergy Cementless Stem, Smith & Nephew, TN, USA) by a single surgeon. Two blinded observers preoperatively templated using both AP xray and EOS imaging for each patient to predict acetabular size, femoral component size, and stem offset. All templating was performed by two observers with standard software (Ortho Toolbox, Sectra AB, Linköping, Sweden) [Figure 1] one week prior to surgery, and were compared using the Cronbach's alpha (∝) coefficient of reliability. The accuracy of templating was reported as the average percent agreement between the implanted size and the templated size for each component. Results. For templating acetabular component size, the exact size was predicted for 48% using AP xrays and 70% using EOS imaging, and within 1 size for 88% using xrays and 98% using EOS imaging. For templating femoral component size, the exact size was predicted exactly for 33% using AP xrays and 60% using EOS imaging, and within 1 size for 85% using xrays and 98% using EOS imaging (Figure 2). Interobserver agreement was excellent for acetabular components (Cronbach's α = 0.94) and femoral components (Cronbach's α = 0.96) using EOS imaging. Conclusions. This study demonstrates that preoperative digital templating for THA using EOS imaging is accurate, with excellent interobserver agreement. EOS imaging has less magnification error, which may partially explain the accuracy of our templating method

Introduction. Aim of this study is to assess any differences in digital templanting accuracy of a modular short femoral stems implanted with 2 different appoaches (direct anterior and posterolateral). Material and Methods. From December 2012 to Jenaury 2014 100 patient undergoing to a THA using the same implant with a short femoral modular stem were prospectively included in the study and divided in 2 groups according to the surgical approach. All the patients underwent to the same preoperative radiological protocol and the digital templating. The digital templating results were compared with the truly inserted implant size and a statistical analysis was carried on. Results. For the cup the mean percentage of agreement (±2 size) was 90.0 % in Anterior approach-group and 89.6 % in the the posterolateral approach group. For the mean percentage of agreement (± 2 size) was 88.0 % in and 89.1 % respectively. Likewise there was a statistical significant better accuracy in the modular femoral neck accuracy in the anterior approach (±2 size) and a statistical significant higher percentage of modular femoral neck with an increased antiversion in the posterolateral approach. Discussion. In our experience digital templating in short modular femoral stem seems to be less accurate for the posterior-lateral approach in term of both femoral neck length and antiversion. A possible explanation may be not a technical error but just a surgeon behavior to overcorrect the templating to prevent dislocation potentially more common using a postero-lateral approach

Introduction. When total knee arthroplasty (TKA) or unicompartmental knee arthroplasty (UKA) was indicated for the patient, it is important to perform the exact preoperative planning. Conventionally we created the plan based on the Xp films and transparent acetate sheets. Recntly, the digital radiographs and templating systems were introduced in hospitals and utilized for the preoperative planning. The purpose of this study is to investigate the accuracy of the digital templating by comparing the size of the implants between those chosen by the planning and those actually selected during the operation. Materials and methods. We investigated the plans of 715 knees with TKAs and 238 knees with UKAs between 2010 and 2014. There were 89 men and 438 women with average age of 72.1. There were 867 osteoarthritis, 46 rheumatoid arthritis, 39 osteonecrosis and 1 revision TKA. We created the preoperative planning using Electronic Picture and Communication system (PACS) and templating system (Advanced Case Plan 2.2 / Stryker). [Fig. 1] During the operation we have checked the actual femoral and tibial sizes of the implants, and compared them with preoperative plannings. Results. The exact matching of the sizes of the implants between the planning and the operation with TKAs were 59.4% for the femoral components, 52.7% for the tibial components and 32.4% for both components. [Fig. 2] While those figures with UKAs were 88.7%, 67.6% and 63.0% respectively. [Fig. 3] The matching within 1 size difference of the size of the implants between the planning and the operation were 92.4% with TKAs and 95.8% with UKAs. Discussion. Our study suggested that the digital templating of the TKAs and UKAs had satisfactory accuracy to use as preoperative planning for the operation. The accuracy was better in femur than that of tibia. The difference of the accuracy indicate the probable presence of the hyperplasia of the medial tibial condyle that we cut off to get good ligamtnt balancing. The accuracy of the UKAs was better than that of TKAs. During UKAs, we initially chose the predicted size of the devise and cut the bone, and then finally select the size of the implant. While during TKAs, we measure the size of the bone and then cut the bone. This difference of the operative procedure may result in the higher accuracy of UKAs. We conclude that digital templating for preoperative planning of TKAs and UKAs had satisfactory accuracy

[Introduction]. Short tapered wedge-shaped cementless (TW) stems have been widely used for several years. The concept of fixation of TW stem is wedge-fit fixation in the proximal metaphysis. Developmental dysplasia of the hip (DDH) has anatomical abnormality, such as excessive femoral anteversion, short femoral neck length, narrow femoral cavity, or proximal-distal mismatching of the femoral canal. Therefore, Mismatching between stem and bone might be occurred in DDH. We evaluated intramedullary matching of short TW stem for DDH by three dimensional (3D) digital template in order to clarify whether mismatching between stem and bone is seen in DDH implanted short TW stem. [Materials and Methods]. One hundred hips (92 patients) with DDH were performed preoperative simulation for total hip arthroplasty by 3D digital template system (ZedHip: Lexi, Tokyo, Japan). The average age was 63.5 years old. There were 12 males and 80 females. The average bone mass index was 21.5 kg/m. 2. Femoral canal shape was normal in 71, champagne-flute in 16 and stovepipe in 13 hips. Bone quality was classified into type A in 23, type B in 74 and type C in 3 hips. Preoperative computed tomography data were used for 3D digital template and reconstructed to 3D femoral model. Short TW stem (Taperloc Complete Microplasty: Biomet, Warsaw, IN) model constructed from computer-assisted design was matched to the reconstructed femoral model. Short TW stem model was in principle implanted according to the femoral neck anteversion with neutral alignment (varus and valgus < 2 degrees, flexion and extension < 2 degrees) at the coronal and sagittal plane of the femur. Stem size was determined in order to obtain the largest intramedullary matching at the coronal plane. Area of stem fitting with the cortical bone was investigated at 10 mm intervals above and below of mid minor trochanter. Intramedullary matching pattern was classified into proximal mediolateral metaphyseal fit, proximal flare fit and diaphyseal fit at multiple reconstructed planes of the 3D femoral model according to stem fitting area. [Results]. Ninety-three percent of stem could be implanted with neutral alignment at the coronal plane, and 86 percent at the sagittal plane. The average stem anteversion was 31.4 degrees. Over 70 percent of stem could be fit with the medial and lateral cortical bone at 10 mm above and below of mid minor trochanter. Intramedullary matching pattern was proximal mediolateral metaphyseal fit in 49%, proximal flare fit in 44% and diaphyseal fit in 7%. [Discussion and Conclusion]. Early migration or failure of osteointegration of TW stem was recently published. Diaphyseal fixation or mismatching between stem and bone is considered as risk factors of early failure of TW stem. In this study, proximal metaphyseal fit, such as mediolateral metaphyseal fit or flare fit, could be achieved in 93% of DDH patients. Mismatching between stem and bone, such as diaphyseal fit, was observed only in 7% of DDH. Short TW stem is good choice for DDH in order to avoid of diaphyseal fixation followed by early migration of stem and decreased osteointegration

Digital templating was used in 50 patients who underwent THA using Merge Ortho software, Cedara. Clinical examination was performed first, to measure leg lengths and account for pelvic obliquity and flexion deformity. Good quality digital radiographs were obtained with anteroposterior and lateral views extending beyond the tip of the femoral component and the cement restrictor. A coin was placed on the ASIS to help in determining radiological magnification. Digital radiographs were saved in DICOM format and imported to EndoMap software system. A 6-step technique was used for templating as follows:. Radiographic assessment; looking at the quality of bone, amount of bone stock, dysplasia, osteophytes, and other abnormalities. Correction of magnification; following the specific instructions of the software, by measuring the diameter of the coin on the digital radiograph. 3. Measuring leg length discrepancy; the software system automatically calculated the leg length discrepancy, even in the presence of pelvic obliquity (Figure1). 4. Templating acetabular component; the desired cup was selected from the implant library after identifying important landmarks. The size and position was modified to fit the acetabulum and to restore the center of rotation of the hip, considering minimal bone removal and sufficient bone coverage laterally. Templating femoral component; the size and position of the desired stem was adjusted to fit the femoral canal, different offsets were compared to find the best match for the patient's original offset. Correction of leg length discrepancy and measuring length of neck resection; the height of the femoral stem was adjusted to correct any leg length discrepancy by placing the center of the head above the center of the cup by the same length of discrepancy. Then the level of the neck resection was marked at the level of the stem collar and the femoral neck cut was measured by a digital ruler from the tip of the lesser trochanter to the mark of neck resection. In case of leg length discrepancy, the height of the femoral neck cut was adjusted accordingly to compensate for the leg length discrepancy. For example, if the affected leg is 20 mm short, place the centre of the head 20 mm above the centre of the cup. Intraoperatively, the surgeon performed the femoral neck osteotomy at the level determined by preoperative templating. Postoperatively, the leg length was measured and compared to the preoperative leg length. Preoperatively, the leg length discrepancy ranged from 5 to 30 mm. In all cases, the leg was short on the side of THR (ipsilateral). Leg length discrepancy was adjusted in all THR cases. Postoperatively, the accuracy of the correction was found to be within 5 millimeters i.e. less than 5mm of shortening or lengthening). Intraoperatively, the level of femoral neck cut ranged from 1 to 44 mm. Digital templating is useful in adjusting leg length discrepancy. In addition, there were other benefits such as predication of femoral and acetabular implant sizes, restoration of normal hip centre, and optimization of femoral offset

Various types of tibial alignment guides exist, the results in performing the tibial resection in total knee arthroplasty (TKA) are more or less than we desired. In addition, it is difficult to estimate the accuracy of tibial component alignment with radiograph because it is difficult to get true frontal and lateral view. In this study, we use new tibial alignment guide and estimate tibial component alignment by using postoperative CT scan. 30 knees underwent TKA using an accelerometer-based, portable navigation device (KneeAlign 2) and postoperative CT scans were obtained. Postoperative CT scans of the lower limbs analysed by 3D digital template system (Athena), demonstrated that 96.6% of the tibial components were placed within 90°± 2°to the mechanical axis in the coronal plane, and 96.6% of the components were placed within 3°± 2°to the mechanical axis in the sagittal plane. As a result of this study, an accelerometer-based, portable navigation device can expect to decrease outliers in tibial component alignment

Restoration of joint line in total knee arthroplasty (TKA) is important for kinematics of knee and ligamentous balance. Especially in revision TKA, it may be difficult to identify the joint line. The aim of this study is to define the relationship between epicondyles and articular surface using CT based three-dimensional digital templating sofware $“Athena” (Soft Cube, Osaka, Japan). 137 knees with osteoarthritis, all caces were grade 2 or lower in Kellgren-Lawrence index, were investigated. Perpendicular lines were dropped from the prominences of the medial and lateral femoral epicondyles to the most distal points of articular surfaces and distances of the lines were measured on the axial and coronal planes. The femoral width was measured as the distance between medial and lateral epicondyles. Each of the distance described above was converted to a ratio by dividing by the femoral width. On the axial plane, the average distance from epicondyles to the posterior articular surfaces were 29.4±2.2mm on the medial side and 21.2±2.3mm on the lateral side. The average of the femoral width was 75.2±4.1mm. On coronal plane, the average distance from epicondyles to the distal articular surfaces were 25.2±2.8mm on the medial side and 21.4±2.5mm on the lateral side. The ratio for the distance from epicondyles to the distal and posterior joint line compared to femoral width was 0.39±0.02, 0.28±0.03, 0.33±0.03 and 0.28±0.03. The distance from epicondyles to the distal and posterior joint line correlates with the femoral width of the distal femur. This information can be useful in determining appropriate joint line

Introduction. Leg length and offset are important considerations in total hip arthroplasty (THA). Navigation systems are capable of providing intra-operative measurements, which help guide the surgeon in leg length and offset adjustment. Objective. This controlled study investigates whether the use of computer navigation leads to more accurate achievement of pre-operative leg length and offset targets in THA. Method. A total of 61 patients were included in the study. A prospective, consecutive series of 24 patients undergoing navigated total hip arthroplasty were compared to an historic, consecutive series of 37 patients who underwent total hip arthroplasty without the use of navigation. The changes made to leg length and femoral offset were measured from scaled pre- and post-operative digital radiographs. The target changes to leg length and femoral offset were recorded from pre-operative digital templating sessions. Results. No statistically significant differences in terms of age, sex and body mass index were found between the two groups. Femoral offset targets were more closely achieved in the navigated cohort compared with the non-navigated group (P < 0.05). The mean deviation from the pre-operative target offset change was 2.9 ± 2.7 mm in the navigated group, and 5.1 ± 4.6 mm in the non-navigated group. For leg length, no statistically significant difference was found between the navigated and non-navigated cohorts in the difference between planned targets and radiographic changes (P=0.78). The mean deviation from target leg length change was 3.9 ± 2.9 mm in the navigated group and 4.2 ± 3.4 mm in the non-navigated group. When the navigation system was employed, procedure time was longer by a mean of 6 minutes, however this finding was not statistically significant (P=0.084). Conclusion. The use of navigation helps the surgeon to achieve their pre-operative goals for offset change. The navigation system was not shown to impact leg length management

The anterior curve of the tibial plateau cortex represents a realiable and reproducible landmark which may help aligning the tibial component with the femoral component and the extensor mechanism. Few studies analyzed the tibial component rotational alignment during total knee arthroplasty. Malrotation can affect both patello-femoral and tibio-femoral postoperative function. We evaluated the rotational relationship between femur and tibia, and we investigated which tibial landmark consistently matches the rotation of the femoral epicondylar axis in full extension (Fig 1). Axial magnetic resonance images of 124 normal knees (statistical power 1-beta=0.8) were analyzed separately by three authors. Scanograms were obtained with the knee in full extension and with the long axis of the foot (second metatarsal bone) aligned on the neutral sagittal plane. The surgical epicondylar axis was drawn and projected over the proximal tibia and tibial tuberosity slices. Multiple anatomical tibial rotational landmarks were drawn and symmetric tibial component digital templates of different sizes were aligned according to each landmark. Alignment of the virtual tibial components was then compared to that of the projected femoral epicondylar axis (Fig 2). The best antero-posterior line to achieve rotational matching between the components was drawn on the proximal tibia slice of each patient. Results of rotation (positive = external rotation, negative = internal) relative to the epicondylar axis were (Fig 3): (a) Medial third-to the middle third of the tibial tubercle 1.2°+/−5.7, (b) Akagi's line (centre of the posterior cruciate ligament tibial insertion to the most medial part of the tibial tubercle) -11.5+/−6.5, (c) The anterior curved tibial plateau cortex (curve-on-curve matching between the tibial template and the anterior cortex) 1.0+/−2.9. Intraclass correlation coefficient resulted 0.923, 0,881, and 0.949 for the Akagi's line, Middle third of tibial tubercle, and the curve-on-curve reference respectively. The anterior curve of the tibial plateau cortex represents a realiable and reproducible landmark which may help aligning the tibial component with the femoral component and the extensor mechanism (Fig 4, 5)

Introduction. Digital x-rays on computer screens are difficult to template due to the lack of standardized magnification. This can be overcome by the use of markers placed onto or next to the patient but have certain shortcomings. Trochanteric marker placements are operator dependant and very difficult to use in the obese patient. Inter- thigh markers are also operator dependent and often embarrassing for radiographer and patient. Anterior combined with posterior markers are very accurate (King et al) but can only be used with a digital template system which is costly and time consuming. We would like to describe a new method of posterior bar markers that are easy to use with standard hip templates. Methods. Over a period of 30 months this method of templating was used on 296 primary total hip replacements. Fifty eight patients had a previous hip replacement with known head diameter which was used as a control to assess the accuracy of enlargement with this method. X-rays were taken of each patient as a standard supine AP of both hips with the patient lying on a marker ruler with 30mm metal bar markers. The X- rays are then loaded onto a PACS digital x-ray system for use in theatre. In theatre the X-rays are enlarged until the 30mm bar markers are enlarged to 31mm on a standard ruler which represents a 20% (as seen in patients with contralateral hip replacements) enlargement of the hip and standard 20% enlarged plastic templates can then be used to measure the neck resection level and assess implant size and offset. The patients with previous contralateral hip replacements were used as controls to evaluate the accuracy of this method by correlating the head size on the enlarged x-ray with the 20% enlarged ruler on the template. Results. This is an easy and reproducible method of taking marked x-rays in our radiology department and no time consuming software is necessary for this method. The level of neck resection differs for every hip with a range of 0–23 mm as measured from a point on the superior area of the femoral neck. In most cases (91%) the selected level of neck resection corresponded to correction of leg length and stability. The remaining cases needed an extra neck resection osteotomy of 1–4 mm. This method correlated well with the final implant size and offset in 97% of cases. Conclusion. The posterior bar marker method is a cheap and easy method to use when templating X-rays prior to hip replacement surgery and is as accurate as any other method without the problem of operator dependency. NO DISCLOSURES

Introduction. Revision hip arthroplasty is a technically challenging operation as proximal bony deficits preclude the use of standard implants. Longer distally fixing stems are therefore required to achieve primary stability. Aims. This work aims to compare the primary stability and biomechanical properties of a new design of tapered fluted modular femoral stem (Redapt®, Smith & Nephew) to that of a conical fluted stem (Restoration®, Stryker). It is hypothesized that the taper will provide improved rotational stability under cyclical loading. Materials & Methods. 7 Pairs of cadaveric femora were obtained according to strict inclusion/exclusion criteria. Each underwent dual energy x-ray absorptiometry and calibration plain-film radiographs were taken. Digital templating was performed using TraumaCad (Voyant Health, Brainlab) to determine implant sizing. Both stems are fluted, modular and manufactured from titanium (figure 1). The control stem (Restoration) featured a straight conical design and the investigation stem (Redapt) a straight tapered design. Implantation was performed by a revision arthroplasty surgeon familiar with both systems. Proximal bone deficiency was reproduced using an extended trochanteric osteotomy with removal of metaphyseal bone before reattaching the osteotomy. Primary stability in the axial, sagittal and coronal planes was assessed using micromotion transducers (HBM, Darmstadt, Germany) (figure 2a) and also by Radiostereometric Analysis (RSA). RSA employs simultaneous biplanar radiographs to measure relative movement. Two 1 mm tantalum beads were mounted on the prosthesis with the centre of the femoral head taken as the third reference point. Beads were placed proximally in the surrounding bone as rigid body markers. Each bone was potted according to the ISO standard for fatigue testing and cyclically loaded at 1 Hz for at least 3 increments (750–350N, 1000–350N, 1500–350N) for 1000 cycles. RSA radiographs were taken at baseline and on completion of each cycle. A strain analysis was concurrently performed using a PhotoStress ® (Vishay Precision Group, Raleigh, USA) photoelastic coating on the medial femoral cortex. Each bone was loaded intact and then with the prosthesis in-situ at 500N increments until strain fringes were identified. Once testing was completed, the stems were sectioned at the femoral isthmus and data is presented on the cross-sectional fit and fill observed. Results. Both stem designs showed comparable primary stability with all stems achieving clinically acceptable micromotion (<150 μm) when loaded at body weight. A larger proportion of the control stems remained stable as loading increased to x2–3 body weight. Transducer-recorded migration appeared greatest in the axial plane (y axis) (figure 2b) with negligible distal movement in the coronal or sagittal planes. Point motion analysis (RSA) indicated most movement to be in the coronal plane (x-axis) (figure 2c) whereas segment motion analysis showed rotation about the long axis of the prosthesis to be largest. Photoelastic strain patterns were transferred more distally in both designs, however substantial stress shielding was also observed (figure 3). Discussion/Conclusion. Both designs achieved adequate distal fixation and primary stability under representative clinical loading conditions. This work supports the continued use of this novel stem design for revision surgery in the presence of extensive proximal bone loss

Introduction. Preoperative planning is an essential procedure for successful total hip arthroplasty. Many studies reported lower accuracy of two-dimensional analogue or digital templating for developmentally dysplastic hips (DDH). There have been few studies regarding the utility of three-dimensional (3D) templating for DDH. The aim of the present study is to assess the accuracy and reliability of 3D templating of cementless THA for hip dysplasia. Methods. We used 86 sets of 3D-CT data of 84 patients who underwent consecutive cementless THA using an anatomical stem and a rim-enlarged cup. There were six men and 78 women with the mean age of 58 years. The diagnosis was developmental dysplasia in 70 hips and osteonecrosis in 14 hips and primary osteoarthritis in 2 hips. There were 53 hips in Crowe group I, 11 hips in Crowe group II and 6 hips in Crowe group III. Each operator performed 3D templating prior surgery using a planning workstation of CT-based navigation system. Planned-versus-achieved accuracy was evaluated. The templating results were categorized as either exact size or +/− 1 size of implanted size. To assess the intra- and inter-planner reliabilities, 3D templating was performed by two authors blinded to surgery twice at an interval of one month. Kappa values were calculated. The accuracy and the intra- and inter-planner reliabilities were compared between the DDH group (70 hips) and the non DDH group (16 hips). Results. There was no significant difference in accuracy of component sizes between the DDH group and the non-DDH group. The accuracy of templating for cup sizes was 76 % for DDH and 75 % for non-DDH group (p=0.95). If accuracy was expanded to include all cups within one size of the implanted size, the accuracy was 97 % and 94 %, respectively (p=0.51). The accuracy of templating for stem sizes was 60 % for the DDH group and 75 % for the non-DDH group (p=0.27). The accuracy within 1 size was 99 % and 94 %, respectively (p=0.25). Regarding intra-planner reliability, mean kappa value for the cup size was 0.67 in the DDH group and 0.81 for the non-DDH group (p=0.18). Mean kappa value for the stem size was 0.64 in the DDH group and 0.79 for the non-DDH group (p=0.18). There were no significant differences in intra-planner reliability between the DDH and non-DDH group. Regarding inter-planner reliability for the cup size, mean kappa value was 0.33 in the DDH group and 0.37 in the non-DDH group (p=0.14). Mean kappa value for the stem size was 0.46 in the DDH group and 0.69 in the non-DDH group (p=0.07). There were no significant differences in inter-planner reliability between the DDH and non-DDH group. Conclusion. The 3D templating for cementless THA was accurate for hip dysplasia. Intra- and inter-planner reliabilities of the 3D templating were comparable with those of other primary diagnosis, while intra-planner reliability of cup sizes was fair regardless of diagnosis

Magnification of anteroposterior radiographs of the pelvis is variable. To improve the accuracy of templating, reliable and radiographer-friendly methods of scaling are necessary. We assessed two methods of scaling digital radiographs of the pelvis: placing a coin of known diameter in the plane of interest between the patient’s thighs, and using a caliper to measure the bony width of the pelvis. A total of 39 patients who had recently undergone hemiarthroplasty of the hip or total hip replacement were enrolled in the study. The accuracy of the methods was assessed by comparing the actual diameter of the head of the prosthesis with the measured on-screen value. The coin method was within a mean of 1.12% (0% to 2.38%) of the actual measurement, the caliper group within 6.99% (0% to 16.67%). The coin method was significantly more accurate (p < 0.001). It was also reliable and radiographer friendly. We recommend it as the method of choice for scaling radiographs of the pelvis before hip surgery.