The accuracy and reliability of preoperative templating for metal-on-metal hip resurfacing

Advances in imaging for pre-surgical planning in hip resurfacing arthroplasty

BACKGROUND

Accurate preoperative templating is essential for the success of hip resurfacing arthroplasty (HRA). While digital radiograph is currently considered the gold standard, stereoradiograph and CT converted 3D methods have shown promising results. However, there is no consensus in the literature regarding the preferred modality for HRA templating, and angular measurements are often overlooked. Thus, this study aimed to: (1) compare the performances of different modality in implant sizing and angle measurements, (2) evaluate the measurement reproducibility, (3) assess the impact of severe osteoarthritis on femoral head sizing, and (4) based on the analysis above, explore the optimal imaging and planning strategy for HRA.

HYPOTHESIS

An optimal imaging modality exists for HRA planning regarding implant sizing and angular measurements.

MATERIALS AND METHODS

Preoperative imaging data from seventy-seven HRA surgeries were collected. Three raters performed templating using digital radiograph, stereoradiograph, and CT converted 3D models. Measurements for femoral head size, neck-shaft angle, and calcar-shaft angle were obtained. The femoral head sizing was compared to the intraoperative clinical decision. The reproducibility of measurements was assessed using the intraclass correlation coefficient (ICC). Correlations were examined between sizing disagreement and osteoarthritis grade (Tonnis Classification).

RESULTS

Digital radiograph, stereoradiograph, and 3D techniques predicted one size off target in 27/77 (35%), 49/70 (70%), and 75/77 (97%) of cases, respectively, corresponding to 1.8±1.6 (0 to 5.67), 0.9±0.7 (0 to 2.67), and 0.4±0.4 (0 to 1.67) sizes off target, indicating statistically significant differences among all three modalities, with p-values all below 0.01. There were no statistically significant differences among the different modalities for angular measurements. Measurements showed moderate to excellent reproducibility (ICC=0.628-0.955). High-grade osteoarthritis did not impact image sizing in any modality (r=0.08-0.22, all p>0.05).

DISCUSSION

CT converted 3D models were more accurate for implant sizing in HRA, but did not significantly outperform other modalities in angular measurements. Given the high costs and increased radiation exposure associated with CT, the study recommended using CT scans selectively, particularly for precise femoral head sizing, while alternative imaging methods can be effectively used for angular measurements.

LEVEL OF EVIDENCE

III; retrospective comparative diagnostic study.

Three-Dimensional Preoperative Planning Software for Hip Resurfacing Arthroplasty

Three-dimensional planning of hip arthroplasty is associated with better visualisation of anatomical landmarks and enhanced mapping for preoperative implant sizing, which can lead to a decrease in surgical time and complications. Despite the advantages of hip resurfacing arthroplasty (HRA), it is considered a technically challenging procedure and associated with inaccurate implant placement. This study aimed to examine the validity, reliability, and usability of preoperative 3D Hip Planner software for HRA. Fifty random cases of various hip osteoarthritis severity were planned twice by two junior trainees using the 3D Hip Planner within a one-month interval. Outcome measures included femoral/cup implant size, stem-shaft angle, and cup inclination angle, and were assessed by comparing outcomes from 2D and 3D planning. An adapted unified theory of acceptance and use of technology (UTAUT) survey was used for software usability. Bland-Altman plots between 3D and 2D planning for stem-shaft and inclination angles showed mean differences of 0.7 and -0.6, respectively (r = 0.93, p < 0.001). Stem-shaft and inclination angles showed inter-rater reliability biases of around -2° and 3°, respectively. Chi-square and Pearson's correlation for femoral implant size showed a significant association between the two assessors (r = 0.91, p < 0.001). The 3D test-retest coefficient of repeatability for stem-shaft and inclination angles were around ±2° and ±3°, respectively, with a strong significant association for femoral implant size (r = 0.98, p < 0.001). Survey analyses showed that 70-90% agreed that 3D planning improved expectancy in four domains. 3D hip planner appears to be valid and reliable in preoperative HRA and shows significant potential in optimising the quality and accuracy of surgical planning.

Determining the accuracy of preoperative total hip replacement 2D templating using the mediCAD® software

Background

Templating is a preoperative planning procedure that improves the efficiency of the surgical process and reduces postoperative complications of total hip arthroplasty (THA) by improving the precision of prediction of prosthetic implant size. This study aimed to evaluate the accuracy of the preoperative cup and stem size digital 2D templating of THA with mediCAD^® software and find the factors that influence the accuracy, such as indication for surgery, patients’ demographics, implant brand, and the assessors’ grade of education.

Methods

We retrospectively retrieved 420 patient template images of all patients who underwent THA between March 2018 and March 2021. Templating of all included images was processed using mediCAD^® software a day before surgery by a newcomer physician to hip arthroplasty course (PGY-2 orthopedic resident or hip surgery fellow). Preoperative templating cup and stem sizes were compared with the actual inserted implant sizes.

Result

After excluding ineligible patients, this study included 391 patients, 193 (49.4%) males and 198 (50.6%) females with a mean age of 43.3 ± 14.9. The average cup sizes predicted before and after surgery were 52.12 ± 14.28 and 52.21 ± 15.05 respectively, and the mean delta cup size (before and after surgery) was 2.79 ± 2.94. The delta stem size before and after surgery has a mean value of 1.53 ± 1.49. The acetabular cup components, measured within ± 0, ± 1, and ± 2 sizes, were 28.9%, 63.9%, 83.1% accurate, respectively. The femoral stem design component measured within ± 0, ± 1, and ± 2 sizes were 27.2%, 61.0%, 78.6% accurate, respectively. Wagner Cone^® stem brand, DDH patients, and females showed significantly higher accuracy of stem size templating. Revision THA has the lowest accuracy in terms of cup size templating. The compression of accuracy rate between resident and fellow revealed no significant differences. Also, no significant difference was detected between the accuracy of templating performed in the first months with the second months of the arthroplasty course period.

Conclusion

Our study showed that under mentioned condition, templating using mediCAD^® has acceptable accuracy in predicting the sizes of femoral and acetabular components in THA patients. Digital software like mediCAD^® remains favorable because of the short learning curve, user-friendly features, and low-cost maintenance, leading to level-up patient care and THA efficacy. Further studies are necessary for clarifying the role of the assessor’s experience and expertise in THA preoperative templating.

Level of evidence

Level III (retrospective observational study).

Radiographic templating of total hip arthroplasty for femoral neck fractures

PURPOSE

The purpose of this study was to evaluate the use of pre-operative digital templating to minimize complications including limb length discrepancy (LLD), intraoperative fractures and early dislocations in patients with intracapsular femoral neck fractures.

METHODS

We retrospectively compared 23 patients undergoing total hip arthroplasty (THA) for intracapsular femoral fractures with pre-operative digital templating and 48 patients without templating.

RESULTS

The mean post-operative LLD was significantly lower in patients who had pre-operative templating than in the control group (6.7 vs. 11.5 mm, p = 0.023). Only three patients (13 %) with templating had LLD greater than 1.5 cm, compared to the 15 patients (31 %) without templating (p = 0.17). In eight cases the final femoral stem size matched the templated size, while 19 patients were within two size increments. Complications included one dislocation and one intra-operative fracture in the control group.

CONCLUSION

The present study demonstrated that careful pre-operative planning may reduce LLD in patients undergoing THA due to intracapsular hip fractures.