Digital templating in primary total hip and knee arthroplasty

The use of digital radiography is becoming more prevalent in orthopedics. This transition impacts the ability to preoperatively plan for implants in total hip arthroplasty (THA) and total knee arthroplasty (TKA). This article reports on the clinical success of digital templating using the Advanced Case Plan (Stryker Imaging, Flower Mound, Texas) system in primary THA and TKA. Digital radiographs of 269 consecutive patients undergoing primary THA (93 cases) or TKA (176 cases) were templated using the Advanced Case Plan digital software package. A 25.4-mm metallic sphere was used as a calibrating marker. Anteroposterior hip and lateral knee radiographs were digitally templated preoperatively and compared to the actual size of the implants at the time of surgery. The accuracy of calibrating images using the metallic sphere was validated by measuring the diameter of femoral heads on 25 postoperative hip radiographs. Digital templating was accurate in predicting the correct implant size in 58.5% of THAs and 66% of TKAs. In 93% of THAs and 98.5% of TKAs, preoperative templating was within 1 size of the final implant. There were no cases in which the predicted implant size varied from the final components by >2 sizes. Calibrating the image using the metallic sphere marker was found to be highly accurate, predicting the correct femoral head size within 1.5 mm in all 25 cases (7 hemiarthroplasties and 18 THAs). Digital templating is an effective means for predicting the size of THA and TKA components, thus remaining a viable option as we transition into the modern era of digital radiography. Future studies will evaluate interobserver reliability and the impact of level of training on templating accuracy.     

Digital pre-operative templating is more accurate in total hip replacement compared to analogue templating

We prospectively evaluated the accuracy of digital compared to analogue pre-operative templating in 50 consecutive primary hip replacements between April 2006 and June 2007. The senior author pre-operatively templated implant size using TraumaCad (Orthocrat Limited, Israel). Thirty-one Exeter primary hip and 19 hybrid hip replacements were performed. Hips were templated using radiographs calibrated against a spherical metal ball. For each hip, an AP pelvis view was used. Acetabular implants used were either Trident PSL or Exeter contemporary cup (Stryker). Femoral stem was Exeter (Stryker). Predicted implant sizes were documented. Post-operatively, the predicted implant size was compared to the implanted components. All post-operative films showed good fit of components and there were no intraoperative or post-operative fractures. The intra-rater reliability (ICC) of analogue templating was 0.96 and digital templating was 0.90. Accurate templating score for acetabular cup was 46% (digital) 43% (analogue), femoral offset was 80% (digital) 70% (analogue), femoral stem was 76% (digital) 60% (analogue). The differences between templating and actual implant sizes were plotted in Bland–Altman plot. Digital templating produced narrower confidence interval compared to analogue templating. Digital templating proved to be statistically, significantly more accurate compared to analogue templating for acetabluar cup and femoral stem. Our data indicate that digital templating is more reliable in predicting actual implant sizes for total hip arthroplasty when performed by the operating surgeon.     

Comparison of digital and plain radiography preoperative templating in total knee arthroplasty

We present the results of prospective evaluation of digital compared to plain radiographic preoperative templating for primary total knee replacement. All consecutive patients undergoing primary knee replacement were eligible. Patients with previous knee replacement or without calibrated digital or plain radiographs were excluded. Plain radiographs were templated against acetate templates. Digital images were templated with the help of commercial software TraumaCad. A 25-mm spherical metal ball placed nearest to the affected knee joint acted as calibration object. The ICC value for intra-rater reliability was 0.846 for tibial templating and 0.840 for femoral templating. PFC sigma cruciate substituting components were implanted in all patients. Twenty-eight consecutive patients between April 2006 and June 2007 were included. Accurate digital templating score was 80% for tibial implant and 40% for femur. Accuracy of analog templating was 55% for tibial implant and 50% for femur. There was no mismatch of over one size. The differences between templated and implanted sizes were plotted against their mean in Bland–Altman plot. The 95% confidence interval of the differences between digital and actual sizes were: 0.78 to −0.75 sizes for tibial implant and 1.15 to −0.93 sizes for femoral implant. The 95% confidence interval of the differences between plain and actual sizes were: 0.38 to −0.99 size for tibial implant and 0.93 to −1.32 size for femoral implant. The two tailed P value for difference between digital and analog templating from a Wilcoxon matched pair signed rank test was 0.021 for tibia and 0.006 for femur. We found preoperative templating by the operating surgeon reliable and accurate but digital templating did not offer any additional advantage.     

Effect of training level on accuracy of digital templating in primary total hip and knee arthroplasty

The use of digital radiography and templating software continues to become more prevalent in orthopedics as the number of total hip arthroplasty (THA) and total knee arthroplasty (TKA) procedures increases every year. The purpose of this study was to evaluate the effect of training level on the accuracy of digital templating for primary THA and TKA. Digital radiographs of 97 patients undergoing primary THA (49 cases) and TKA (48 cases) were retrospectively templated using OrthoView digital planning software (OrthoView LLC, Jacksonville, Florida). Anteroposterior hip and lateral knee radiographs were digitally templated and compared with the actual size of the implants used intraoperatively. An implant sales representative, physician assistant, medical student (J.D.K.), resident (A.R.H.), and fellowship-trained arthroplasty surgeon (B.R.L.) templated all cases independently after a standardized orientation and were blinded to the actual component sizes used for surgery. The medical student, resident, and arthroplasty surgeon retemplated the same 97 cases 1 month later to determine intraobserver reliability. Digital templating was accurate in predicting the correct implant size in 33% of THAs and 54% of TKAs. In 73% of THAs and 92% of TKAs, digital templating was within 1 size of the actual implant used, and in 88% of THAs and 99% of TKAs, templating was within 2 sizes of the final components. In no cases did the templated implant size vary by >3 sizes from the final components. Interobserver reliability for templating THAs and TKAs showed good reliability as measured by intraclass correlation coefficient (ICC) (ICC(THA)=.70; ICC(TKA)=.86). Intraobserver reliability for templating THAs had excellent reliability for the resident and arthroplasty surgeon, with a kappa coefficient (κ) of 0.92, and good reliability for the medical student (κ=0.78). Intraobserver reliability for templating TKAs showed excellent reliability among all examiners (κ=0.90).     

The magnification of digital radiographs in the trauma patient: Implications for templating

Introduction

Digital radiographs are increasingly used for planning orthopaedic surgical procedures, despite the fact that they are frequently not calibrated to correct for magnification. The typical magnification of digital radiographs in the trauma patient has not yet been reported. The aims of this study were to assess the magnification of such radiographs, and to discuss if and when accurate calibration is required for trauma templating.

Materials and methods

The operative notes and postoperative radiographs of 227 trauma patients were obtained. Each patient had undergone one of the following procedures: hip hemiarthroplasty, femoral nailing, tibial nailing, ankle plating, humeral nailing, humeral plating, or forearm plating. The dimensions of the implants used were measured on the uncalibrated postoperative radiographs using the hospital's Picture Archiving and Communication System software. The actual dimensions of the orthopaedic implants were obtained from the operation notes, and these were compared with the radiographic measurements. The intraobserver and interobserver variability of the radiographic measurements was also assessed.

Results

The radiographic magnification was greatest for the femoral head, and most variable for the femoral shaft. The magnification was least for the forearm. In general the magnitude and variability of magnification was least at the peripheries. There was good correlation between the measured and actual dimensions of the implants. The intraobserver and interobserver variability between the radiographic measurements was extremely small.

Conclusion

Despite the ease and convenience of performing measurements on digital radiographs, these measurements are unreliable if the radiograph has not been calibrated. We believe that careful calibration of digital radiographs is essential for accurate templating in the trauma patient, although is less critical when templating the humeral canal, the tibial canal, the ankle and the forearm.     

Determination of accuracy of preoperative templating of noncemented femoral prostheses

The purpose of this study was to determine the accuracy of preoperative templating of primary, noncemented femoral components. A retrospective review of charts and radiographs was performed on 74 hips in 64 patients who had undergone either noncemented total hip arthroplasty (THA) or placement of an endoprosthesis (including bipolar). Preoperative radiographs were templated by a total joint arthroplasty attending surgeon, a senior orthopaedic resident, and a junior resident. The templated size corresponded to the actual femoral implant used in approximately 50% of cases. When femoral prostheses within one size above or below the templated size were included, the accuracy of preoperative templating rose to 88–95%. When implants within two sizes of the templated size were included, the accuracy approached 100%. Factors associated with discrepancies in the size of femoral stem used included placement of an undersized implant, presence of metal hardware that obscured the ability to template accurately, proximal bone deformity, sclerotic bone, acute femoral neck fracture, and inadequate preoperative radiographs. The accuracy of templating increased gradually with the level of training. The most experienced investigator was able to template within one size of the actual implant used in 95% of cases, compared with 88% and 82% for the less experienced investigators. Acute femoral neck fractures and proximal bone deformity were associated with the largest discrepancies in templated sizes.     

Effect of introduction of digital radiographic techniques on pre-operative templating in orthopaedic practice

AIM: To assess whether the introduction of digital radiographic acquisition has altered the magnification of pelvic radiographs compared to standard acquisition techniques, and whether this influences preoperative implant templating for total hip arthroplasty. SETTING: District general hospital orthopaedic out-patient department. PATIENTS AND METHODS: 51 sets of patient radiographs were studied, where digital and standard radiographic techniques had been used for each patient. Key bony landmarks were measured, the scaled ruler analysed and the femur templated to gauge the most appropriate implant size of implant. RESULTS: Introduction of digital techniques has resulted in a mean magnification of 97%, whereas most manufacturers' templates assume a magnification of 115-120%. For the Exeter femoral component, the templated size showed only moderate correlation with that templated from a standard radiograph (kappa index 0.46), although the offset templated showed good correlation (kappa index 0.89). CONCLUSIONS: Surgeons should be aware that introduction of digital techniques of radiograph acquisition may reduce the magnification of the film and, therefore, reduce the accuracy of pre-operative templates supplied by the manufacturers of implants, resulting in incorrect selection of implants.     

Digital templating in total hip arthroplasty in the NHS: ��computer says no����

Preoperative planning plays an important role in any surgical procedure and total hip replacement (THR) is no exception. Templating of radiographs allows preoperative assessment of the correct size of implant to be used, lowers the risk of periprosthetic fracture, helps restore femoral offset and leg length, facilitates the optimisation of alignment and ensures the correct implants sizes are available. All of these reduce the intraoperative pressures leading to the selection of incorrectly sized implants. This study assessed whether there is adequate provision of the current NHS Picture Archiving and Communication Systems (PACS) to allow optimal digital templating for THRs. Data were collected using a telephone questionnaire requesting information from the on-call orthopaedic SpR in 28 Greater London and surrounding area NHS Hospitals. PACS were used in all 28 (100%) hospitals that were contacted. Digital templating software was available in 14 (50%) hospitals. Despite this, none of them performed digital templating regularly. In the 50% that did have digital templating, this was not routinely done for the following reasons; only 3 (10.7%) allowed easy access to the software to the SpRs; only one SpR received formal training on how to use the system; only one hospital regularly used methods to accurately allow the software to assess magnification for accurate sizing (e.g. sizing balls). Digital PACS systems have made great improvements in the access of radiographs in the NHS. In orthopaedic practice, however, we have shown that the benefit of digital templating is being overlooked within the NHS.     

A Comparison of Acetate vs Digital Templating for Preoperative Planning of Total Hip Arthroplasty : Is Digital Templating Accurate and Safe?

The purposes of this study were to compare the accuracy of acetate and digital templating for primary total hip arthroplasty (THA) and to determine if digital templating is safe. Preoperative planning was performed on 50 consecutive preoperative radiographs during 2005. Templating results were compared with the actual hip implants used. Interrater reliability of acetate templating and accuracy of acetate and digital templating were recorded. Digital measurement overestimated acetabular size (P < .001) and underestimated the femoral size (P = .03). The absolute errors were larger for digital compared with acetate templating; however, mean absolute errors did not differ significantly (acetabulum, P = .090; femur, P = .114). Acetate and digital templating can accurately predict the size of THA implants. Digital templating was determined to be acceptably safe for preoperative planning of primary THA operations.     

Pre-operative digital templating in cemented hip hemiarthroplasty for neck of femur fractures

Pre-operative digital templating allows the surgeon to foresee any anatomical anomalies which may lead to intra-operative problems, and anticipate appropriate instruments and implants required during surgery. Although its role is well-established in successful elective total hip arthroplasty, little work has been done on its use in hip hemiarthroplasty in neck of femur fractures. We describe our initial experience of digital templating in 40 consecutive patients who have undergone cemented hip hemiarthroplasty, assessing templating accuracy between templated implant sizes to actual implant sizes. 81% of implanted heads were templated to within two head sizes, and 89% of implanted stems were templated to within two sizes. Although there was a moderately strong correlation of 0.52 between templated and actual head sizes, this correlation was not demonstrated in femoral stem sizes. Mean leg length discrepancy was −2.5 mm (S.D. 8.5), and the mean difference in femoral offset between the operated and non-operated hip was −1 mm (S.D. 4.4). Digital templating is a useful adjunct to the surgeon in pre-operative planning of hip hemiarthroplasty in the restoration of leg length and femoral offset. However, its accuracy is inferior to that of elective total hip arthroplasty.     

Reliability of preoperative templating in total knee arthroplasty

The purpose of this study was to determine the reliability of preoperative templating in primary total knee arthroplasty and the influence of the seniority of the surgeon on templating. A retrospective study of 25 randomly selected total knee replacements was undertaken, with templating of preoperative radiographs by four surgical staff members. These included a consultant, a specialist registrar and two senior house officers. Reliability for an exact match between template size and implant actually used was 49% for the femoral component and 67% for the tibial component. The statistical agreement between templated size and actual implant size was classed as only fair to moderate. There was no statistical difference in templating reliability between junior and senior surgical staff. These results indicate that the current system of templating for total knee arthoplasties is prone to error and can only be used as an approximate guide.     

The accuracy of computed tomography for determining femoral and tibial total knee arthroplasty component rotation

Patellofemoral complications, instability, and tibial polyethylene wear after total knee arthroplasty (TKA) resulting from malrotation of the tibial or femoral components (or both) may be difficult to diagnose based on physical examination and standard knee radiographs. The preoperative assessment of implant rotational alignment is critical in planning treatment because the femoral or tibial component (or both) may need to be revised if malpositioned. The purpose of this study was to ascertain the accuracy of computed tomography (CT) scan for determining rotational alignment of femoral and tibial components in TKA. TKA components were inserted in human cadaver specimens at neutral and 5 degrees of external or internal rotation. For each position, the amount of rotation, determined from digital photographs, was compared with CT scan. The correlation coefficient between these two values averaged 0.87, which was significant at P < .05. The CT scan protocol described in this study can be applied clinically to patients with patellofemoral complaints to confirm or rule out the presence of component malrotation.     

Scaling digital radiographs for templating in total hip arthroplasty using conventional acetate templates independent of calibration markers

We describe a scaling method for templating digital radiographs using conventional acetate templates independent of template magnification without the need for a calibration marker. The mean magnification factor for the radiology department was determined (119.8%; range, 117%-123.4%). This fixed magnification factor was used to scale the radiographs by the method described. Thirty-two femoral heads on postoperative total hip arthroplasty radiographs were then measured and compared with the actual size. The mean absolute accuracy was within 0.5% of actual head size (range, 0%-3%) with a mean absolute difference of 0.16 mm (range, 0-1 mm; SD, 0.26 mm). Intraclass correlation coefficient showed excellent reliability for both interobserver and intraobserver measurements with intraclass correlation coefficient scores of 0.993 (95% CI, 0.988-0.996) for interobserver measurements and intraobserver measurements ranging between 0.990 and 0.993 (95% CI, 0.980-0.997).     

Digital templating facilitates accurate leg length correction in total hip arthroplasty

Digital templating of pre-operative radiographs is increasingly utilised by surgeons before total hip arthroplasty (THA) as part of an adequate preoperative preparation to minimise complications. Templating can accurately predict the required implant sizes but its use in facilitating correction of leg length discrepancy (LLD) has been underreported in the literature. We performed a retrospective analysis of a cohort of consecutive patients undergoing primary THA. A comparison was made of the implant sizes templated with actual sizes used. In addition, pre-operative leg-length discrepancy (LLD) was noted and compared with intra-operative measurement of LLD correction and post-operative LLD correction seen on postoperative radiographs, as measured by two independent observers. Statistical analysis was performed to investigate the correlation between pre- and postoperative measurements. Fifty nine patients that had primary THA were investigated, 42 with hybrid replacements, 17 with cemented replacements. Spearman's-rho 2-tailed correlation between templated and implanted femoral offset, stem size and acetabular cup size was 0.850, 0.709 and 0.834 respectively (p < 0.01 for all). Correlation between the pre-operative templated LLD and the measured post-operative corrected LLD was 0.841 (p < 0.01). No difference existed between hybrid and cemented hips or the presence or absence of a contralateral hip replacement. In this study, templating for THA was significantly accurate in predicting the required femoral and acetabular implant sizes. In addition, the correction of pre-operative LLD was accurately performed, as evidenced by measurement on post-operative films. The results of this study support the pre-operative digital templating of radiographs in total hip arthroplasty.     

Digital templating in hip hemiarthroplasty: Is it possible to accurately predict femoral head size from magnification alone?

BackgroundTemplating is an integral part of pre-operative planning in elective hip arthroplasty to achieve favourable long-term outcomes, but its applications in trauma surgery remain limited. When templating from radiographs without a calibration marker, there is always an element of magnification which must be accounted for. Our aim was to establish our institute-specific magnification and to determine whether using this to predict femoral head size in hemiarthroplasty was more accurate than using set magnifications previously reported in the literature.Materials & methodsFifty consecutive patients who underwent hip hemiarthroplasty were retrospectively identified, their pre-operative radiographs reviewed and femoral head measured with templating software. Intra- and inter-observer reliability analyses were performed. Using this value, and two set values of 15% and 21% magnification, we attempted to predict femoral head sizes of our original cohort. The results were compared using paired t-test to ascertain if there was any significant difference in accuracy.ResultsWe established our institute-specific magnification as 17%. Inter- and intra-observer reliability were excellent. However, using this magnification we were only able to correctly predict to within ± one femoral head size in 49% of patients. There was no significant difference in accuracy comparing our institute-specific magnification with other magnifications from the literature.ConclusionWe would not recommend using magnification factor in digital templating software as this could potentially lead to errors in predicting final femoral head size in hip hemiarthroplasty and adversely affect patient outcomes.     

Effect of Body Mass Index on Digital Templating for Total Hip Arthroplasty

Background

Digital templating is becoming more prevalent in orthopedics. Recent investigations report high accuracy using digital templating in total hip arthroplasty (THA); however, the effect of body mass index (BMI) on templating accuracy is not well described.

Artificial Intelligence to Identify Arthroplasty Implants From Radiographs of the Knee

BackgroundRevisions and reoperations for patients who have undergone total knee arthroplasty (TKA), unicompartmental knee arthroplasty (UKA), and distal femoral replacement (DFR) necessitates accurate identification of implant manufacturer and model. Failure risks delays in care, increased morbidity, and further financial burden. Deep learning permits automated image processing to mitigate the challenges behind expeditious, cost-effective preoperative planning. Our aim was to investigate whether a deep-learning algorithm could accurately identify the manufacturer and model of arthroplasty implants about the knee from plain radiographs.MethodsWe trained, validated, and externally tested a deep-learning algorithm to classify knee arthroplasty implants from one of 9 different implant models from retrospectively collected anterior-posterior (AP) plain radiographs from four sites in one quaternary referral health system. The performance was evaluated by calculating the area under the receiver-operating characteristic curve (AUC), sensitivity, specificity, and accuracy when compared with a reference standard of implant model from operative reports.ResultsThe training and validation data sets were comprised of 682 radiographs across 424 patients and included a wide range of TKAs from the four leading implant manufacturers. After 1000 training epochs by the deep-learning algorithm, the model discriminated nine implant models with an AUC of 0.99, accuracy 99%, sensitivity of 95%, and specificity of 99% in the external-testing data set of 74 radiographs.ConclusionsA deep learning algorithm using plain radiographs differentiated between 9 unique knee arthroplasty implants from four manufacturers with near-perfect accuracy. The iterative capability of the algorithm allows for scalable expansion of implant discriminations and represents an opportunity in delivering cost-effective care for revision arthroplasty.     

Prospective Validation of a Demographically Based Primary Total Knee Arthroplasty Size Calculator

BackgroundPreoperative planning for total knee arthroplasty (TKA) is essential for streamlining operating room efficiency and reducing costs. Digital templating and patient-specific instrumentation have shown some value in TKA but require additional costs and resources. The purpose of this study was to validate a previously published algorithm that uses only demographic variables to accurately predict TKA tibial and femoral component sizes.MethodsFour hundred seventy-four consecutive patients undergoing elective primary TKA were prospectively enrolled. Four surgeons were included, three of which were unaffiliated with the retrospective cohort study. Patient sex, height, and weight were entered into our published Arthroplasty Size Prediction mobile application. Accuracy of the algorithm was compared with the actual sizes of the implanted femoral and tibial components from 5 different implant systems. Multivariate regression analysis was used to identify independent risk factors for inaccurate outliers for our model.ResultsWhen assessing accuracy to within ±1 size, the accuracies of tibial and femoral components were 87% (412/474) and 76% (360/474). When assessing accuracy to within ±2 sizes of predicted, the tibial accuracy was 97% (461/474), and the femoral accuracy was 95% (450/474). Risk factors for the actual components falling outside of 2 predicted sizes include weight less than 70 kg (odds ratio = 2.47, 95% confidence interval [1.21-5.06], P = .01) and use of an implant system with <2.5 mm incremental changes between femoral sizes (odds ratio = 5.50, 95% confidence interval [3.33-9.11], P < .001).ConclusionsThis prospective series of patients validates a simple algorithm to predict component sizing for TKA with high accuracy based on demographic variables alone. Surgeons can use this algorithm to simplify the preoperative planning process by reducing unnecessary trays, trials, and implant storage, particularly in the community or outpatient setting where resources are limited. Further assessment of components with less than 2.5-mm differences between femoral sizes is required in the future to make this algorithm more applicable worldwide.     

The accuracy of digital templating: a comparison of short-stem total hip arthroplasty and conventional total hip arthroplasty

Purpose

Selection of the correct femoral stem size is crucial in total hip arthroplasty for an uncomplicated implantation and good initial stability. Pre-operative templating has been shown to be a valuable tool in predicting the correct implant size. For short-stem total hip arthroplasty (SHA), which recently is increasingly used, it is unknown if templating can be performed as reliable as conventional total hip arthroplasty (THA).

Methods

A total of 100 hip arthroplasties, 50 with SHA and 50 with THA, were templated by four orthopaedic surgeons each. The surgeons had different levels of professional experience and performed a digital template of the acetabular and femoral component on the pre-operative radiographs. The results were compared with the truly inserted implant size.

Results

For the femoral stems the average percentage of agreement (±1 size) was 89.0 % in SHA and 88.5 % in THA. There was no significant difference among surgeons in the accuracy of templating the correct stem size and no significant difference between templating SHA and THA. For the acetabular component the average percentage of agreement (±1 size) was 75.8 %. However, the more experienced surgeons showed a significant higher accuracy for templating the correct cup size than the less experienced surgeons.

Conclusion

Digital templating of SHA can predict the stem sizes as accurately as conventional THA. Therefore digital templating is also recommendable for SHA, as it helps to predict the implant size prior to surgery and thereby might help to avoid complications.     

Assessment of reproducibility and accuracy in templating hybrid total hip arthroplasty using digital radiographs

In 20 patients undergoing hybrid total hip arthroplasty, the reproducibility and accuracy of templating using digital radiographs were assessed. Digital images were manipulated using either a ten-pence coin as a marker to scale for magnification, or two digital-line methods using computer software. On-screen images were templated with standard acetate templates and compared with templating performed on hard-copy digital prints. The digital-line methods were the least reliable and accuracy of sizing compared with the inserted prostheses varied between -1.6% and +10.2%. The hard-copy radiographs showed better reproducibility than the ten-pence coin method, but were less accurate with 3.7% undersizing. The ten-pence coin method was the most accurate, with no significant differences for offset or acetabulum, and undersizing of only 0.9%. On-screen templating of digital radiographs with standard acetate templates is accurate and reproducible if a radiopaque marker such as a ten-pence coin is included when the original radiograph is taken.