A patient-specific predictive model increases preoperative templating accuracy in hip arthroplasty

Evaluation of a stepped, fixed-height magnification marker stand for use with a 100-mm marker in implant sizing prediction in 52 total hip replacement procedures in dogs

OBJECTIVE

To describe the use of a 100-millimeter marker placed on a stepped, fixed-height magnification marker stand to measure radiographic magnification on accuracy of implant size prediction when used for canine total hip replacement (THR) implant size selection.

STUDY DESIGN

Retrospective study.

ANIMALS

Fifty-two hips in 45 dogs.

METHODS

This study evaluated 52 consecutive canine total hip replacement surgery pre-planning procedures involving 45 dogs with 7 undergoing staged bilateral THRs. Data collected included demographic information, measured radiographic magnification for magnification recalibration, implant size prediction of the cups (52) and the stems (52) based on digital templates superimposed on digital radiographs, and the actual implant sizes used during surgery.

RESULTS

Use of the magnification marker stand (MMS) and template application system resulted in an accurate prediction of implant size of 98/104 implants (94.2%) implants.

CONCLUSION

A 100-mm marker placed on a magnification marker stand was a viable method to measure and recalibrate for magnification on digital radiographs during the template process to predict the THR implant sizes that should be available when the surgery begins.

CLINICAL SIGNIFICANCE

This stepped calibration marker stand is helpful in determination of an accurate preoperative THR implant size prediction, lowering implant stock thresholds, operating time, and associated complications. Additionally, the radiographic documentation of the marker's step height allows for indefinite confirmation of the magnification marker height used and for accurate repeatability for all follow-up imaging examinations and contralateral procedure planning.

Predicting Implant Size in Total Hip Arthroplasty

Background

Efficient resource management is becoming more important as the demand for total hip arthroplasty (THA) increases. The purpose of this study is to evaluate the ability of linear regression and Bayesian statistics in predicting implant size for THA using patient demographic variables.

Material and methods

A retrospective, single-institution joint-replacement registry review was performed on patients who underwent primary THA from 2005 to 2019. Demographic information was obtained along with primary THA implant data. A total of 11,730 acetabular and 8536 femoral components were included. A multivariable regression model was created on a training cohort of 80% of the sample and applied to the validation cohort (remaining 20%). Bayesian posterior probability methods were applied to the training cohort and then tested in the validation cohort to determine the 1%, 5%, and 10% error tolerance thresholds.

Results

The most predictive regression model included height, weight, and sex (cup: R² = 0.57, all P < .001; stem mediolateral size [M/L]: R² = 0.32, all P < .001). Removing weight had a minimal effect and resulted in a more parsimonious model (cup: R² = 0.56, all P < .001; stem M/L: R² = 0.32, all P < .001). Applying the posterior probability estimate to the validation cohort in the Bayesian model using height, weight, and sex demonstrated high accuracy in predicting the range of required implant sizes (95.3% cup and 90.4% stem M/L size).

Conclusion

Implant size in THA is correlated with demographic variables to accurately predict implant size using Bayesian modeling. Predictive models such as linear regression and Bayesian modeling can be used to improve operating room efficiency, supply chain inventory management, and decrease costs associated with THA.

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

BACKGROUND

Accurate preoperative planning is a key component of successful total hip arthroplasty (THA). The purpose of the present study was to compare the accuracy and reliability of three-dimensional (hipEOS) and common digital two-dimensional (TraumaCad) templating with special focus on stem morphology.

METHODS

51 patients undergoing THA were randomized to two groups. Preoperative planning was performed on 23 patients with hipEOS (3D) and on 28 patients with TraumaCad (2D) planning software. Planning results were compared with the implanted component size. Inter- and intraobserver reliability as well as planning accuracy of both planning methods with special focus on straight and short stem design were recorded.

RESULTS

Intraobserver reliability of both planning methods was good for component planning (ICC_2,1: 0.835-0.967). Interobserver ICC_2,1 for stem and cup planning were higher for 3D templating (3D ICC_2,1: 0.906-0.918 vs. 2D ICC_2,1: 0.835-0.843). Total stem and cup size predictions were within 2 sizes for 3D and within 3 sizes for 2D planning. Comparing short stem planning accuracy of both planning methods, absolute difference between implanted and planned component size was significantly lower in 3D planning (P = .029). There was no significant difference in straight stem (P = .935) and cup (P = .954) planning accuracy.

CONCLUSION

Our findings suggest that 3D templating with hipEOS software has a good overall reliability and may have a better planning accuracy of short stem prostheses than digital templating with TraumaCad software. Assuming that the number of implanted short stem prostheses will further increase in coming years, a more precise planning with 3D technique can contribute to improve surgery outcome.

A new and improved acetabular cup digital templating method and its clinical application

BACKGROUND AND OBJECTIVE

Preoperative acetabular cup templating has an important auxiliary effect on hip surgery. The traditional acetabular cup templating method requires the measuring person to have some experience in total hip replacement (THA) surgery since the measurement results vary from person to person with differences between different measuring persons. To obtain stable templating results, we designed a new acetabular cup templating method and tested the inter-person measuring differences and measurement accuracy of this method. Meanwhile, the clinical application of this method was preliminarily explored.

MATERIALS AND METHODS

The pattern of this new method was manual labeling of imaging characteristic points and then programmed automatic measurements. The measurement process was performed entirely by orthopedic graduate students without any experience in hip replacement surgery. The inter-person measuring difference was evaluated by comparing the templating results of three measuring persons. The accuracy of the templating was evaluated by comparing the templating results with the actual size of the prosthesis in the surgery. The correlation between the position of the acetabular cup and the templating error was analyzed to explore the clinical significance of the templating results. This study was a retrospective study which included templating in a total of 406 cases for total hip replacement with cementless cup prosthesis. Digital measurements were performed using the Matlab software from MathWorks. The statistical comparison was performed using Kendall's W test.

RESULTS

The results of the three measuring persons were completely identical in 61.8% (251/406) of cases, and the variation in 38.2% (155/406) of cases did not exceed one size of the acetabular cup. The Kendall's W coefficient was 0.977, and p < 0.01. The measurement accuracy is not as good as the traditional method in exactly accurate measurement and ±1 cup size, but it is similar to the traditional method in the ±2 cup sizes. The correlation between the templating error and the position evaluation of the implanted acetabular cups reveals: (1) larger the templating error, larger the proportion of the acetabular cups with poor position; (2) the proportion of acetabular cup with poor position slowly increased when the templating error was from 0 to 1 size, and the proportion rapidly increased when the templating error was from 1 to 2 size.

CONCLUSION

All the patients with clear teardrop bottom and lateral superior edge of acetabulum were able to use our method to predict the size of the acetabular cup. The method has the following advantages: (1) it does not require the measuring person to have any previous experience of the THA surgery, which reduces the labor cost of the templating; (2) the differences between the measuring persons is small, the measurement result can be repeated; (3) it can predict the probability of acetabular cup with poor positioning according to the templating error, and thereby reminding the surgeon to recheck and correct the position of the acetabular cup in time during the surgery.

Magnification of digital hip radiographs differs between clinical workplaces

Preoperative planning for total hip arthroplasty includes templating on anteroposterior radiographs. It is necessary to consider radiographic magnification in order to scale templates accurately. Studies dealing with hip templating report different values of radiographic magnification. It is not clear if the observed difference in magnification between the studies is caused by variability in studied groups, methodology or instrumentation. We hypothesize that there is a difference in magnification between clinical workplaces. Within this study, radiographic magnification was estimated on 337 radiographs of patients after total hip surgery from five orthopaedic departments in the Czech Republic. Magnification was determined for each patient as a ratio between diameter of implanted femoral head measured on radiogram and its true size. One-way ANOVA revealed significant differences in magnification between workplaces (F(4,332) = 132, p≤0.001). These results suggest that radiographic magnification depends on the workplace where it is taken or more precisely on radiographic device. It indicates potential limits in generalizability of results of studies dealing with preoperative planning accuracy to other institutions.

The Accuracy of Digital Templating for Primary Total Hip Arthroplasty: Is There a Difference Between Direct Anterior and Posterior Approaches?

BACKGROUND

The direct anterior approach (DAA) has gained recent popularity for total hip arthroplasty (THA), as it provides immediate feedback on cup position and limb length using fluoroscopy. The purpose of this study is to evaluate any differences in the accuracy of digital templating for preoperative planning of THA, performed with 2 different surgical approaches: DAA using a radiolucent table with intraoperative fluoroscopy and the posterior approach (PA).

METHODS

One hundred thirty-one consecutive patients (148 hips) underwent a THA by a single surgeon, using the same cup and stem designs. Seventy-five hips were performed using the DAA using a fracture table and fluoroscopy. Seventy-three hips were performed using the PA with the patient positioned in lateral decubitus using standard positioners without fluoroscopy. Preoperative radiographs were digitally templated by the same surgeon.

RESULTS

The PA patients had a higher mean body mass index and were more likely to have a preoperative diagnosis of avascular necrosis. The accuracy of templating for predicting the cup size to be within 2 mm was 91% for DAA vs 88% for PA (P = .61). For stem size, the accuracy was 85% (to within 1 size) for the DAA vs 77% for the PA (P = .71). Likewise, there was no significant difference in predicting the final stem's neck angle or femoral offset.

CONCLUSION

Digital templating was found to be a reliable and highly accurate method for predicting component sizes and offset for THA, regardless of using either the PA or the DAA with fluoroscopy.

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.

METHODS

Digital radiographs of 603 consecutive patients (645 hips) undergoing primary THA by a single surgeon were digitally templated using OrthoView (Jacksonville, FL). A 25-mm metallic sphere was used as a calibration marker. Preoperative digital hip templates were compared with the final implant size. Hips were stratified into groups based on BMI: BMI <30 (315), BMI 30-35 (132), BMI 35-40 (97), and BMI >40 (101).

RESULTS

Accuracy between templating and final size did not vary by BMI for acetabular or femoral components. Digital templating was within 2 sizes of the final acetabular and femoral implants in 99.1% and 97.1% of cases, respectively.

CONCLUSION

Digital templating is an effective means of predicting the final size of THA components. BMI does not appear to play a major role in altering THA digital templating accuracy.

Calibration Marker Position in Digital Templating of Total Hip Arthroplasty

BACKGROUND

We report a mathematical method to assess the vertical and horizontal positions of spherical radiopaque objects of known size in conventional radiographs.

METHODS

The reliability and validity of the method were tested in an experimental setting and applied to 100 anteroposterior pelvic radiographs with external calibration markers and unilateral total hip arthroplasty (THA).

RESULTS

We found excellent reliabilities; intraclass correlation coefficients for interobserver and intraobserver reliabilities were 0.999-1.000 (P = .000). The mean normal height of THA was 198 mm (range: 142-243 mm, standard deviation: 18 mm) above the detector. Vertical and horizontal external marker positions differed significantly from the true hip center (THA; P < .001 and P = .017).

CONCLUSION

This method could enhance patient safety by enabling automated detection of malpositioned calibration markers by templating software.