Digital templating in total hip arthroplasty: Additional anteroposterior hip view increases the accuracy

Accuracy of Total Hip Arthroplasty Templating Using Set Calibration Magnifications

Background Templating for total hip arthroplasty has been adopted over recent decades as a reliable and accurate method for pre-operative planning. The use of calibration markers for this process provides a recognised benefit at the expense of cost, availability and error. Many surgeons use a set magnification of 118% to account for calibration errors when templating total hip arthroplasty. This study aims to assess the accuracy of templating with standardised magnifications and assess the effect of BMI on templating accuracy. Materials and methods A retrospective analysis was performed using a single-surgeon series of 119 consecutive total hip arthroplasties. Anteroposterior radiographs were taken pre- or post-operatively without calibration hardware. Pre-operatively, the total hip arthroplasty was templated on TraumaCad (BrainLab Inc, Westchester, IL) using either 118% or 119% calibration magnification. Post-operative magnification was calibrated using the known femoral head diameter. Templated and implanted prostheses were compared for size. Results At 118%, 61.1% of cups matched those templated with 96.3% of cups within two sizes. At 119%, 52.5% of cups used matched their templates with 100% within two sizes. There was no significant difference between 118% and 119% cup size prediction (p=0.49). A trend was noticed in increasing magnification error with increasing BMI. However, BMI had no significant effect on the accuracy of templating cup size within two cup sizes (p=0.58). Conclusion. Templating acetabular cups using a set magnification of 118% or 119% yields accurate results and provides a reliable method to template without calibration equipment. Whilst BMI can affect magnification error, this has no significant effect on the accuracy of implanted cups and stems within two sizes.

Can the intra-operative measurement of the diameter of the femoral head help surgeons to choose the best size of the acetabular cup?

PURPOSE

We hypothesized that the intra-operative measurement of the femoral head may increase the accuracy of the acetabular cup size optimal selection in total hip arthroplasty (THA). The purpose of this clinical research was to analyze the correlation between the estimated cup size from intra-operative measurement of the femoral head and the pre-operative templated cup size.

METHODS

A prospective observational single-center study was conducted from June 2019 to January 2020 including primary THA (n = 100). All cases were pre-operatively templated. The measurement of the anterior-posterior diameter of the femoral head was routinely intra-operatively performed. Any definitive implanted cup was considered as "oversized" when the size was > 4 mm than the diameter of the native head.

RESULTS

The median (interquartile range) size of the implanted cup, pre-operative planned cup size, and diameter of the femoral head were measured 52 (50-54) mm, 50 (48-54) mm and 49 (45-51) mm, respectively. Pre-operative planned size cup accurately predicted the implanted cup or differed in only one size (2 mm) in 77 (78%) cases. Otherwise, intra-operative femoral head measurement method accurately predicted the implanted or differed in only one size (2 mm) in 51 (87%) cases (p = 0.097).

CONCLUSION

The intra-operative femoral head measurement is a simple and reliable tool to help the surgeons choose the best size of the acetabular cup and is as reliable as the pre-operative templating in order to avoid cup oversizing in THA. Utmost caution is warranted whenever the cup reamer is > 4 mm than the anterior-posterior diameter of the native head.

Is analog preoperative planning still applicable?-comparison of accuracy of analog and computer preoperative planning methods in total hip arthroplasty

Background

Preoperative planning is an integral part of total hip arthroplasty and has a significant impact on surgical technique and clinical outcome. The variety of types and sizes of endoprosthesis components makes the procedure more demanding and generates a need for accurate preoperative planning. The objective of this study was to analyze an analog method of preoperative planning of primary total hip arthroplasty based on templates overlaying on preoperative radiograms and compare its accuracy for predicting the size, both the stem and cup, with computer planning methods.

Methods

A retrospective cohort study based on 360 X-ray images of hip joints in 348 patients qualified for total hip arthroplasty between 2018 and 2019. The study group consisted of 136 men and 212 women, with an average age of 65 years (56 to 85 years). Material included both cementless and cemented endoprostheses.

Results

In the analyzed material, the accuracy of cup planning using the analog method was 85% (P<0.001) and 77% (P<0.001) in the planning of stem size. However, using the computer method, planning accuracy was 82% (P<0.001) for the cup and 72% (P<0.001) for the stem.

Conclusions

Both methods of preoperative planning remain effective. The analog method of preoperative planning is simple, precise, and repeatable in choosing the type and size of endoprosthesis components with an accuracy of 85% and 77% for the cup and stem respectively. The accuracy of planning depends on the type of endoprosthesis and in the case of the cemented endoprosthesis, it is lower than in cementless.

Robotic Arm-Assisted Total Hip Arthroplasty to Correct Leg Length Discrepancy in a Patient With Spinopelvic Obliquity

Leg length discrepancy is not an uncommon result of total hip arthroplasty and a major cause of patient dissatisfaction. Spinopelvic obliquity is a less-recognized cause of limb length differences in patients undergoing total hip arthroplasty. The robotic arm has recently been introduced to enhance implant positioning during surgery and to achieve more predictable leg length and offset goals. In this article, we illustrate the case of a patient who presented with a leg length discrepancy associated with significant spinopelvic obliquity. We show the use of the robotic arm total hip application to improve her pelvic obliquity and limb length discrepancy. This approach helped with the patient's symptoms and gait as well as her radiographic pelvic alignment.

Retrospective Comparative Study of the Influence on Quality of Primary Total Hip Arthroplasty by the EndoCert-Certification System in a Communal Hospital

The EndoCert^®-Initiative system sets specific requirements for the structural, process and result quality in certified Arthroplasty Centers in Germany. However, it remains unclear to what extent the certification process can increase the quality in total hip and knee arthroplasty. Aim of the comparative retrospective study is to analyse the change in quality of total hip arthroplasty in a communal hospital before and after the certification process. All primary total hip arthroplasties (n = 366) between 2013 and 2016 were included in the study retrospectively and grouped by treatment period. Treatment was performed in group 1 without clinical pathways, in group 2 pathway-controlled without a valid certificate and in group 3 pathway-controlled after final completion of the certification process. Outcome quality was analysed using quality indicators defined by the EndoCert-Initiative and further predefined indicators. Results show quality improvement under certified pathway-controlled treatment, e.g. time of surgery, cup and stem positioning, blood transfusion rate, periprosthetic fractures. However, improvements were not significantly in all cases and limitations must be recognized. Positive effects of the certification process legitimate capital investment and efforts. Further quality indicators may be implemented in the certification process to improve quality of treatment in arthroplasty.

Preoperative sizing of hip hemiarthroplasties to accurately estimate head size from non- standardised pelvic radiographs: Can it be done?

BACKGROUND

Preoperative sizing of implants for hip fracture patients requiring a hemiarthroplasty is difficult due to non-standardised radiographs, absence of sizing marker, variable patient position and body habitus. We investigated whether a simple tool could help predict femoral head size, allowing surgeons to safely proceed with surgery when implant stocks are limited, and to potentially improve theatre efficiency.

METHODS

Three independent reviewers measured the maximum width of the contralateral (intact) femoral head using PACS software in 50 cases of intracapsular hip fracture. This was linearly regressed on actual implant size to calculate the average magnification coefficient. Inter- and intra-rater reliability were evaluated using intraclass correlation coefficients (ICC).

RESULTS

The best fitting magnification constant was 118% (95% confidence interval 16.0-19.7%), which achieved a mean error of 1.7 mm. Prediction accuracy was significantly improved by allowing a constant (intercept) as a second parameter in the regression model (p = 0.01), which achieved a mean error of just 1.4 mm from the implant used. The inclusion of the constant reduces errors at the upper and lower extremes of head sizes. ICCs for inter- and intra-rather agreement were 0.94 and 0.98 respectively.

CONCLUSION(S)

We have shown that hip hemiarthroplasty head sizes can be reliably and accurately predicted from non-standardised pre-operative radiographs. We have devised a method which can easily be adopted by other centres and tailored to the characteristics of their radiology department.

Total hip arthroplasty planning

Preoperative planning is mandatory to achieve the restoration of a correct and personalized biomechanics of the hip.

The radiographic review is the first and fundamental step in the planning. Limb or pelvis malpositioning during the review results in mislead planning.

Correct templating is possible using three different methods: acetate templating on digital X-ray, digital 2D templating on digital X-ray and 3D digital templating on CT scan.

Time efficiency, costs, reproducibility and accuracy must be considered when comparing different templating methods. Based on these parameters, acetate templating should not be abandoned; digital templating allows a permanent record of planning and can be electronically viewed by different members of surgical team; 3D templating is intrinsically more accurate. There is no evidence in the few recently published studies that 3D templating impacts positively on clinical outcomes except in difficult cases.

The transverse acetabular ligament (TAL) is a reliable intraoperative soft tissue reference to set cup position.

Spine–hip relations in osteoarthritic patients undergoing hip joint replacement must be considered.

Cite this article: EFORT Open Rev 2019;4:626-632. DOI: 10.1302/2058-5241.4.180075

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

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

Assessment of magnification of digital radiographs in total HIP arthroplasty

Objective

Total hip arthroplasty (THA) preoperative planning requires the calibration of X-ray. We evaluate the magnification in standard pelvis hip X-ray and determine its relation with biometric factors.

Methods

The magnification of 140 THA X-ray were calculated with the known femoral head (MF_FH) and acetabular component (MF_AC). Gender, age, height, weight, and BMI were correlated to the magnification.

Results

The MF_FH and MF_AC were 113.2 ± 4,4 and 113,4 ± 3,6 respectively. No significant differences by gender and no correlation with height, weight or BMI.

Conclusion

The X-ray magnification should be calibrated in every institution to improve the accuracy of preoperative planning.