Augmented Reality- vs Accelerometer-Based Portable Navigation System to Improve the Accuracy of Acetabular Cup Placement During Total Hip Arthroplasty in the Lateral Decubitus Position

Retrospective study comparing the accuracies of handheld infrared stereo camera and augmented reality-based navigation systems for total hip arthroplasty

BACKGROUND

The use of portable navigation systems (PNS) in total hip arthroplasty (THA) has become increasingly prevalent, with second-generation PNS (sPNS) demonstrating superior accuracy in the lateral decubitus position compared to first-generation PNS. However, few studies have compared different types of sPNS. This study retrospectively compares the accuracy and clinical outcomes of two different types of sPNS instruments in patients undergoing THA.

METHODS

A total of 158 eligible patients who underwent THA at a single institution between 2019 and 2022 were enrolled in the study, including 89 who used an accelerometer-based PNS with handheld infrared stereo cameras in the Naviswiss group (group N) and 69 who used an augmented reality (AR)-based PNS in the AR-Hip group (group A). Accuracy error, navigation error, clinical outcomes, and preparation time were compared between the two groups.

RESULTS

Accuracy errors for Inclination were comparable between group N (3.5° ± 3.0°) and group A (3.5° ± 3.1°) (p = 0.92). Accuracy errors for anteversion were comparable between group N (4.1° ± 3.1°) and group A (4.5° ± 4.0°) (p = 0.57). The navigation errors for inclination (group N: 2.9° ± 2.7°, group A: 3.0° ± 3.2°) and anteversion (group N: 4.3° ± 3.5°, group A: 4.3° ± 4.1°) were comparable between the groups (p = 0.86 and 0.94, respectively). The preparation time was shorter in group A than in group N (p = 0.036). There were no significant differences in operative time (p = 0.255), intraoperative blood loss (p = 0.387), or complications (p = 0.248) between the two groups.

CONCLUSION

An Accelerometer-based PNS using handheld infrared stereo cameras and AR-based PNS provide similar accuracy during THA in the lateral decubitus position, with a mean error of 3°-4° for both inclination and anteversion, though the AR-based PNS required a shorter preparation time.

A novel imageless accelerometer-based navigation system improves acetabular cup placement accuracy during total hip arthroplasty in the lateral decubitus position

INTRODUCTION

The accuracy of acetabular cup placement using conventional portable imageless navigation systems in total hip arthroplasty (THA) in the lateral decubitus position remains challenging. Several novel portable imageless navigation systems have been developed recently to improve cup placement accuracy in THA. This study compared the accuracy of acetabular cup placement using a conventional accelerometer-based portable navigation (c-APN) system and a novel accelerometer-based portable navigation (n-APN) system during THA in the lateral decubitus position.

MATERIALS AND METHODS

This retrospective cohort study compared 45 THAs using the c-APN and 45 THAs using the n-APN system. The primary outcomes were the absolute errors between the intraoperative and postoperative values of acetabular cup radiographic inclination and anteversion angles and the percentage of cases with absolute errors within 5°. Intraoperative values were shown on navigation systems, and postoperative measurements were conducted using computed tomography images.

RESULTS

The median absolute errors of the cup inclination angles were significantly smaller in the n-APN group than in the c-APN group (3.9° [interquartile range 2.2°-6.0°] versus 2.2° [interquartile range 1.0°-3.3°]; P = 0.002). Additionally, the median absolute errors of the cup anteversion angles were significantly smaller in the n-APN group than in the c-APN group (4.4° [interquartile range 2.4°-6.5°] versus 1.9° [interquartile range 0.8°-2.7°]; P < 0.001). Significant differences were observed in the percentage of cases with absolute errors within 5° of inclination (c-APN group 67% versus n-APN group 84%; P = 0.049) and anteversion angles (c-APN group 62% versus n-APN group 91%; P = 0.001).

CONCLUSIONS

The n-APN system improved the accuracy of the cup placement compared to the c-APN system for THA in the lateral decubitus position.

Accuracy of portable navigation during THA in patients with severe developmental dysplasia of hip

INTRODUCTION

Correct cup placement in total hip arthroplasty (THA) for patients with developmental dysplasia of the hip (DDH) is considerably difficult. This study aimed to analyze the orientation accuracy of cup insertion during THA using a portable navigation system in patients with DDH.

MATERIALS AND METHODS

In this retrospective cohort study, we analyzed data from 64 patients who underwent THA using infrared stereo camera-matching portable navigation. Patients underwent THA via the anterolateral approach in the lateral decubitus position. Navigation records for intraoperative cup angles, postoperative cup angles measured on computed tomography (CT) images, and cup angle measurement differences were measured and compared between patients with non-DDH/mild DDH and severe DDH. Furthermore, the predictive factors for outliers of accurate acetabular cup placement were analyzed.

RESULTS

The average measurement absolute abduction differences (postoperative CT-navigation record) were 3.9 ± 3.5° (severe DDH) and 3.3 ± 2.6° (non-DDH/ mild DDH), and the anteversion differences were 4.7 ± 3.4° (severe DDH) and 2.3 ± 2.1° (non-DDH/ mild DDH). The anteversion difference was different between the two groups. Multivariate analysis showed that the navigation difference (absolute difference in anteversion between postoperative CT and navigation records of > 5°) was significantly associated with severe DDH (odds ratio [OR]: 3.3; p = 0.049, 95% confidence interval [CI]: 1.0-11.1) and posterior pelvic tilt (OR: 1.1; p = 0.042, 95% CI: 1.0-1.27).

CONCLUSIONS

In patients with severe DDH, it is important to pay close attention during THA using portable navigation. However, the average difference was < 5º even in patients with severe DDH, and the accuracy may be acceptable in a clinical setting when the cost is considered.

Accuracy of cup placement and pelvic motion in total hip arthroplasty in the lateral decubitus position using a new computed tomography-based navigation system with augmented reality technology

INTRODUCTION

This study aimed to investigate the accuracy of cup position and assess the changes in pelvic tilt during primary total hip arthroplasty (THA) in the lateral decubitus position using a new computed tomography (CT)-based navigation system with augmented reality (AR) technology.

MATERIALS AND METHODS

There were 37 cementless THAs performed using a CT-based navigation system with AR technology in the lateral decubitus position and 63 cementless THAs performed using manual implant techniques in the lateral decubitus position in this retrospective study. Postoperative cup radiographic inclination and anteversion were measured using postoperative CT, and the proportion of hips within Lewinnek's safe zone was analyzed and compared between the two groups. The mean absolute values of navigation error were assessed. Intraoperative pelvic tilt angles were also recorded using navigation system.

RESULTS

The percentage of cups inside Lewinnek's safe zone was 100% in the navigation group and 35% in the control group (p < 0.001). The mean absolute values of navigation error in inclination and anteversion were 2.9° ± 2.1° and 3.3° ± 2.4°, respectively. The mean abduction angle of the pelvis was 5.1° ± 4.8° after placing the patients in the lateral decubitus position and 4.1° ± 6.0° after cup placement. The mean posterior tilt angle was 6.8° ± 5.1° after placing the patients in the lateral decubitus position and 9.3° ± 5.9° after cup placement. The mean internal rotation angle was 14.8° ± 7.4° after cup placement. There were no correlations between the navigation error in inclination or anteversion and the absolute values of changes of the pelvic tilt angle at any phase.

CONCLUSIONS

Although progressive pelvic motion occurred in THA in the lateral decubitus position, especially during cup placement, the CT-based navigation system with AR technology improved cup placement accuracy.

Comparison between accuracy of augmented reality computed tomography-based and portable augmented reality-based navigation systems for cup insertion in total hip arthroplasty

Augmented reality (AR) has been used for navigation during total hip arthroplasty (THA). AR computed tomography (CT)-based navigation systems and AR-based portable navigation systems that use smartphones can also be used. This study compared the accuracy of cup insertion during THA using AR-CT-based and portable AR-based navigation systems. Patients with symptomatic hip disease who underwent primary THA in the supine position using both AR CT-based and portable AR-based navigation systems simultaneously between October 2021 and July 2023 were included. The primary outcome of this study was the absolute difference between cup angles in the intraoperative navigation record and those measured on postoperative CT. The secondary outcome was to determine the factors affecting the absolute value of the navigation error in radiographic inclination (RI) and radiographic anteversion (RA) of the cup, including sex, age, body mass index, left or right side, approach, and preoperative pelvic tilt. This study included 94 consecutive patients. There were 11 men and 83 women, with a mean age of 68 years. The mean absolute errors of RI were 2.7° ± 2.0° in the AR CT-based and 3.3° ± 2.4° in the portable AR-based navigation system. The mean absolute errors of RA were 2.5° ± 2.1° in the AR CT-based navigation system and 2.3° ± 2.2° in the portable AR-based navigation system. No significant differences were observed in RI or RA of the cup between the two navigation systems (RI: p = 0.706; RA: p = 0.329). No significant factors affected the absolute value of the navigation errors in RI and RA. In conclusion, there were no differences in the accuracy of cup insertion between the AR CT-based and portable AR-based navigation systems.

THA-Net: A Deep Learning Solution for Next-Generation Templating and Patient-specific Surgical Execution

BACKGROUND

This study introduces THA-Net, a deep learning inpainting algorithm for simulating postoperative total hip arthroplasty (THA) radiographs from a single preoperative pelvis radiograph input, while being able to generate predictions either unconditionally (algorithm chooses implants) or conditionally (surgeon chooses implants).

METHODS

The THA-Net is a deep learning algorithm which receives an input preoperative radiograph and subsequently replaces the target hip joint with THA implants to generate a synthetic yet realistic postoperative radiograph. We trained THA-Net on 356,305 pairs of radiographs from 14,357 patients from a single institution's total joint registry and evaluated the validity (quality of surgical execution) and realism (ability to differentiate real and synthetic radiographs) of its outputs against both human-based and software-based criteria.

RESULTS

The surgical validity of synthetic postoperative radiographs was significantly higher than their real counterparts (mean difference: 0.8 to 1.1 points on 10-point Likert scale, P < .001), but they were not able to be differentiated in terms of realism in blinded expert review. Synthetic images showed excellent validity and realism when analyzed with already validated deep learning models.

CONCLUSION

We developed a THA next-generation templating tool that can generate synthetic radiographs graded higher on ultimate surgical execution than real radiographs from training data. Further refinement of this tool may potentiate patient-specific surgical planning and enable technologies such as robotics, navigation, and augmented reality (an online demo of THA-Net is available at: https://demo.osail.ai/tha_net).

Does a Commercially Available Augmented Reality-based Portable Hip Navigation System Improve Cup Positioning During THA Compared With the Conventional Technique? A Randomized Controlled Study

BACKGROUND

Portable hip navigation systems have been developed to combine the accuracy of cup positioning by large console navigation systems with the ease of use and convenience of conventional surgical techniques. Although a novel augmented reality-based portable hip navigation system using a smartphone (AR navigation) has become available recently, no studies, to our knowledge, have compared commercially available AR navigation with the conventional technique. Additionally, no studies, except for those from designer-surgeon series, have demonstrated the results of AR navigation.

QUESTIONS/PURPOSES

(1) Does intraoperative use of commercially available AR navigation improve cup positioning compared with the conventional technique? (2) Are operative factors, clinical scores, and postoperative course different between the two groups?

METHODS

In this randomized trial, 72 patients undergoing THA were randomly assigned to undergo either commercially available AR navigation or a conventional technique for cup placement. All patients received the same cementless acetabular cups through a posterior approach in the lateral decubitus position. The primary outcome of the present study was cup positioning, including the absolute differences between the intended target and angle achieved, as well as the number of cups inside the Lewinnek safe zone. Our target cup position was 40° abduction and 20° anteversion. Secondary outcomes were operative factors, between-group difference in improvement in the Hip Disability and Osteoarthritis Outcome Score (HOOS), and the postoperative course, including the operative time (between the start of the surgical approach and skin closure), procedure time (between the first incision and skin closure, including the time to insert pins, registration, and transfer and redrape patients in the navigation group), time taken to insert pins and complete registration in the navigation group, intraoperative and postoperative complications, and reoperations. The minimum follow-up period was 6 months, because data regarding the primary outcome-cup positioning-were collected within 1 week after surgery. The between-group difference in improvement in HOOS, which was the secondary outcome, was much lower than the minimum clinically important difference for the HOOS. No patients in either group were lost to follow-up, and there was no crossover (the randomized treatment was performed in all patients, so there was no difference between an intention-to-treat and a per-protocol analysis).

RESULTS

The use of the commercially available AR navigation slightly improved cup positioning compared with the conventional technique in terms of the absolute difference between the desired and achieved amounts of cup abduction and anteversion (which we defined as "absolute differences"; median 1° [IQR 0° to 4.0°] versus median 5° [IQR 3.0° to 7.5°], difference of medians 4°; p < 0.001 and median 2° [IQR 1.9° to 3.7°] versus median 5° [IQR 3.2° to 9.7°], difference of medians 2°; p = 0.001). A higher proportion of cups were placed inside the Lewinnek safe zone in the navigation group than in the control group (94% [34 of 36] compared with 64% [23 of 36]; p < 0.001). Median operative times were not different between the two groups (58 minutes [IQR 49 to 72 minutes] versus 57 minutes [IQR 49 to 69 minutes], difference of medians 1 minute; p = 0.99). The median procedure time was longer in the navigation group (95 minutes [IQR 84 to 109 minutes] versus 57 minutes [IQR 49 to 69 minutes], difference of medians 38 minutes; p < 0.001). There were no differences between the two groups in improvement in HOOS (27 ± 17 versus 28 ± 19, mean difference -1 [95% CI -9.5 to 7.4]; p = 0.81). In the navigation group, no complications occurred in the pin sites; however, one anterior dislocation occurred. In the conventional group, one hip underwent reoperation because of a deep infection.

CONCLUSION

Although the use of commercially available AR navigation improved cup positioning in THA, the improvement in clinical scores and postoperative complication rates were not different between the two groups, and the overall magnitude of the difference in accuracy was small. Future studies will need to determine whether the improvement in the percentage of hips inside the Lewinnek safe zone results in differences in late dislocation or polyethylene wear, and whether such benefits-if any-justify the added costs and surgical time. Until or unless more compelling evidence in favor of the new system emerges, we recommend against widespread use of the system in clinical practice.

LEVEL OF EVIDENCE

Level Ⅱ, therapeutic study.

Augmented reality-assisted versus conventional total hip arthroplasty: a systematic review and meta-analysis

BACKGROUND

Extended reality (XR), including virtual reality, augmented reality (AR), and mixed reality, has been used to help achieve accurate acetabular cup placement in total hip arthroplasty (THA). This study aimed to compare the differences between XR-assisted and conventional THA.

METHODS

In this systematic review and meta-analysis, electronic databases including PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials (CENTRAL), and clinicaltrials.gov were searched for studies from inception to September 10, 2023. The outcomes were accuracy of inclination and anteversion, duration of surgery, and intraoperative blood loss. Meta-analysis was performed using Review Manager 5.4 software.

RESULTS

A total of five studies with 396 patients were included in our study. The pooled results indicated AR-assisted THA had better accuracy of inclination and anteversion than conventional THA (SMD = - 0.51, 95% CI [- 0.96 to - 0.07], P = 0.02; SMD = - 0.96, 95% CI [- 1.19 to - 0.72], P < 0.00001), but duration of surgery and intraoperative blood loss were similar in the two groups.

CONCLUSION

This systematic review and meta-analysis found that AR-assisted THA had better accuracy of inclination and anteversion than conventional THA, but the duration of surgery and intraoperative blood loss were similar in the two groups. Based on the pooled results, we suggested that AR can provide more precise acetabular cup placement than conventional methods in THA.

Accuracy comparison of cup positioning during total hip arthroplasty using Hip Align and AR-Hip in the supine position

INTRODUCTION

The aim of this study is to compare the accuracy of acetabular cup positioning between the accelerometer-based navigation system and the augmented reality-based navigation system during THA in the supine position.

MATERIALS AND METHODS

This retrospective study included 66 patients (70 hips) who underwent THA using two types of portable navigation system, Hip Align or AR-Hip, in the spine position. The absolute difference between the intraoperative navigation record and postoperative measurement using computed tomography data was evaluated. Preoperative clinical factors that decreased the accuracy of cup positioning by ≥ 3° were analyzed via multiple logistic regression analyses.

RESULTS

The average absolute error of inclination was 2.8 ± 2.6° in Hip Align and 2.7 ± 1.8° in AR-Hip, and absolute anteversion error was 2.5 ± 2.0° in Hip Align and 2.6 ± 2.2° in AR-Hip, and there was no significantly different between the two navigation systems. There was a significant association between the absolute measurement error (≥ 3°) of cup inclination and patients' BMI in the Hip Align group [odds ratio (OR) 1.350; 95% confidence interval (CI) 1.035-1.760; p = 0.027], but not in the AR-Hip group.

CONCLUSIONS

The accuracy of the acetabular cup positioning between the Hip Align and AR-Hip showed no difference during THA in the spine position. The high BMI could have negative influence on the accuracy of cup positioning in THA using Hip Align, thus AR-Hip could be designable for obesity patients.

Intraoperative Pelvic Tilt and Axial Rotation During Total Hip Arthroplasty Through the Direct Anterior Approach is Affected by the Acetabular Retractor and Cup Impactor

Background

Intraoperative pelvic motion during total hip arthroplasty (THA) in the supine position affects acetabular cup placement and occurs at each step of THA; however, there are no reports of pelvic motion changes during each stage of THA via the direct anterior approach (DAA). This study aimed to evaluate pelvic motion at each step of THA through the DAA.

Methods

From March to October 2022, 71 hips were prospectively measured for intraoperative pelvic tilt and axial rotation during THA through the DAA at a single center. These parameters were measured during each surgical step using the augmented reality-hip navigation system.

Results

Both pelvic tilt and axial rotation were maximal during acetabular cup placement. The mean intraoperative pelvic tilt and axial rotation during cup placement were 4.8 ± 2.6° (95% confidence interval, 4.19-5.41°) and 4.2 ± 3.3° (95% confidence interval, 3.42-4.98°), respectively. The effects of the acetabular retractor and cup impactor on pelvic tilt and axial rotation were comparable. Spearman's correlation tests showed significant correlation between axial rotation and body mass index (r = -0.444, P = .00011).

Conclusions

The pelvis tilts forward and rotates toward the surgical side during THA through the DAA. The effects of the acetabular retractor and cup impactor on pelvic motion are comparable. Cup implantation must take into account pelvic movement, and it must be recognized that the pelvis is moving at that time, even with only the acetabular retractor inserted, compared to before the skin incision.

Registration in the supine position improve the accuracy of cup placement in total hip arthroplasty using a portable navigation system

Portable navigation systems have been developed for use in total hip arthroplasty (THA) in recent years. Although intraoperative registration in the lateral decubitus position or the supine position is need to create the three-dimensional coordinate system, it is not clear which position is appropriate. The purpose of this study was to assess the accuracy of cup placement in primary THA in the lateral decubitus position using an image-free handheld navigation device with registration in the lateral decubitus or the supine position, and clarify which position is appropriate. This retrospective study included 129 consecutive cementless THAs performed using an image-free handheld navigation device in the lateral decubitus position. Registration in the first 68 hips was performed in the lateral decubitus position and the last 61 hips was performed in the supine position. Postoperative cup radiographic inclination and radiographic anteversion were assessed, and the accuracy was compared between the two groups. The mean absolute errors of the postoperative measured inclination and anteversion from the target angles were 3.9° ± 2.2° and 4.8° ± 3.5° in the lateral group and 2.9° ± 2.7° and 3.2° ± 2.7° in the supine group (p < 0.05). The percentage of cups inside Lewinnek's safe zone was 94% in the lateral group and 95% in the supine group (ns). The mean absolute values of navigation error in inclination and anteversion were 3.1° ± 2.1° and 4.2° ± 2.8° in the lateral group and 2.3° ± 2.0° and 3.1° ± 2.4° in the supine group (p < 0.05 and p < 0.05). Registration in the supine position improved the accuracy of cup insertion compared with the lateral decubitus position in THA using an image-free handheld navigation device in the lateral decubitus position.

Accuracy of augmented reality with computed tomography-based navigation in total hip arthroplasty

BACKGROUND

Augmented reality (AR) provides the surgeon with direct visualization of radiological images by overlaying them on the patient. This study aimed to evaluate the accuracy of cup placement using a computed tomography (CT)-based AR navigation system.

METHODS

Sixty-five prospectively enrolled patients underwent primary cementless total hip arthroplasty (THA) in a supine position using this novel AR navigation system, and changes in pelvic flexion angle (PFA) were evaluated. Absolute navigation errors were defined as the absolute differences between angles in the intraoperative navigation record and those measured on postoperative CT. Factors affecting the absolute navigation error in cup alignment were determined.

RESULTS

Mean absolute change in PFA between preoperative CT and reduction was 2.1° ± 1.6°. Mean absolute navigation errors were 2.5° ± 1.7° in radiographic inclination (RI) and 2.5° ± 2.2° in radiographic anteversion (RA). While no factors significantly affecting absolute navigation error were found for RI, absolute change in PFA between preoperative CT and reduction correlated significantly with the absolute navigation error for RA.

CONCLUSION

This CT-based navigation system with AR enabled surgeons to place the cup more accurately than was possible by freehand placement during THA in a supine position.

Does Augmented Reality-based Portable Navigation Improve the Accuracy of Cup Placement in THA Compared With Accelerometer-based Portable Navigation? A Randomized Controlled Trial

BACKGROUND

Previous studies reported good outcomes of acetabular cup placement using portable navigation systems during THA. However, we are aware of no prospective studies comparing inexpensive portable navigation systems using augmented reality (AR) technology with accelerometer-based portable navigation systems in THA.

QUESTIONS/PURPOSES

(1) Is the placement accuracy of the acetabular cup using the AR-based portable navigation system superior to that of an accelerometer-based portable navigation system? (2) Do the frequencies of surgical complications differ between the two groups?

METHODS

We conducted a prospective, two-arm, parallel-group, randomized controlled trial involving patients scheduled for unilateral THA. Between August and December 2021, we treated 148 patients who had a diagnosis of osteoarthritis, idiopathic osteonecrosis, rheumatoid arthritis, or femoral neck fracture and were scheduled to undergo unilateral primary THA. Of these patients, 100% (148) were eligible, 90% (133) were approached for inclusion in the study, and 85% (126) were finally randomized into either the AR group (62 patients) or the accelerometer group (64 patients). An intention-to-treat analysis was performed, and there was no crossover between groups and no dropouts; all patients in both groups were included in the analysis. There were no differences in any key covariates, including age, sex, and BMI, between the two groups. All THAs were performed via the modified Watson-Jones approach with the patient in the lateral decubitus position. The primary outcome was the absolute difference between the cup placement angle displayed on the screen of the navigation system and that measured on postoperative radiographs. The secondary outcome was intraoperative or postoperative complications recorded during the study period for the two portable navigation systems.

RESULTS

There were no differences between the AR and accelerometer groups in terms of the mean absolute difference in radiographic inclination angle (3° ± 2° versus 3° ± 2° [95% CI -1.2° to 0.3°]; p = 0.22). The mean absolute difference in radiographic anteversion angle displayed on the navigation screen during surgery compared with that measured on postoperative radiographs was smaller in the AR group than that in the accelerometer group (2° ± 2° versus 5° ± 4° [95% CI -4.2° to -2.0°]; p < 0.001). There were few complications in either group. In the AR group, there was one patient each with a surgical site infection, intraoperative fracture, distal deep vein thrombosis, and intraoperative pin loosening; in the accelerometer group, there was one patient each with an intraoperative fracture and intraoperative loosening of pins.

CONCLUSION

Although the AR-based portable navigation system demonstrated slight improvements in radiographic anteversion of cup placement compared with the accelerometer-based portable navigation system in THA, whether those small differences will prove clinically important is unknown. Until or unless future studies demonstrate clinical advantages that patients can perceive that are associated with such small radiographic differences, because of the costs and the unquantified risks associated with novel devices, we recommend against the widespread use of these systems in clinical practice.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Visualization, registration and tracking techniques for augmented reality guided surgery: a review

Augmented reality (AR) surgical navigation has developed rapidly in recent years. This paper reviews and analyzes the visualization, registration, and tracking techniques used in AR surgical navigation systems, as well as the application of these AR systems in different surgical fields. The types of AR visualization are divided into two categories ofin situvisualization and nonin situvisualization. The rendering contents of AR visualization are various. The registration methods include manual registration, point-based registration, surface registration, marker-based registration, and calibration-based registration. The tracking methods consist of self-localization, tracking with integrated cameras, external tracking, and hybrid tracking. Moreover, we describe the applications of AR in surgical fields. However, most AR applications were evaluated through model experiments and animal experiments, and there are relatively few clinical experiments, indicating that the current AR navigation methods are still in the early stage of development. Finally, we summarize the contributions and challenges of AR in the surgical fields, as well as the future development trend. Despite the fact that AR-guided surgery has not yet reached clinical maturity, we believe that if the current development trend continues, it will soon reveal its clinical utility.

A new accelerometer-based portable navigation system provides high accuracy of acetabular cup placement in total hip arthroplasty in both the lateral decubitus and supine positions

INTRODUCTION

No studies have compared the accuracy of acetabular cup placement in total hip arthroplasty (THA) in the supine and lateral decubitus positions using the same portable navigation system. Thus, this study aimed to compare the accuracy of acetabular cup placement using a new accelerometer-based portable navigation system combined with an infrared stereo camera and inertial measurement unit between the supine and lateral decubitus positions.

MATERIALS AND METHODS

This retrospective study compared 45 THAs performed in the supine position (supine group) and 44 THAs performed in the lateral decubitus position (lateral group) using the same portable navigation system. The primary outcome was the absolute errors of cup placement angles, defined as the absolute values of the differences between cup radiographic inclination and anteversion angles displayed on the navigation system and those measured on postoperative computed tomography images.

RESULTS

No significant difference in the median absolute error of the cup inclination angle (supine group 1.7° [interquartile range 0.8°-3.1°] vs. lateral group 2.1° [interquartile range 1.0°-3.7°]; p = 0.07) was found between the two groups. Similarly, no significant difference in the median absolute error of the anteversion angle (supine group 1.9° [interquartile range 0.8°-3.4°] vs. lateral group 2.1° [interquartile range 0.9°-3.1°]; p = 0.42) was found.

CONCLUSION

This new accelerometer-based portable navigation system may provide high accuracy of the cup placement in THA in the lateral decubitus and supine positions.

Augmented reality-aided unicompartmental knee arthroplasty

Purpose

To illustrate a surgical technique for augmented reality (AR)-assisted unicompartmental knee arthroplasty (UKA) and report preliminary data.

Methods

We developed an AR-based navigation system that enables the surgeon to see the tibial mechanical axis superimposed on the patient’s leg in addition to the tibial cutting angle. We measured the tibial resection angle in 11 UKAs using postoperative radiographs and calculated the absolute difference between preoperative target angle and postoperative measured angle. The target angle was determined for each patient: mean values were 0.7° ± 1.0° varus in coronal alignment and 5.3° ± 1.4° posterior slope in sagittal alignment.

Results

The angles measured on postoperative radiographs were 2.6° ± 1.2° varus in the coronal plane and 4.8° ± 2.5° posterior slope in the sagittal plane. The absolute differences between the target and measured angles were 1.9° ± 1.5° in coronal alignment and 2.6° ± 1.2° in sagittal alignment. No patients experienced complications, including surgical site infection and periprosthetic fracture.

Conclusion

The AR-based portable navigation system may provide passable accuracy in terms of proximal tibial resection during UKA.

Level of Evidence

IV

Comparing the accuracy of three-dimensional mini-optical portable navigation and accelerometer-based portable navigation system for acetabular cup placement during total hip arthroplasty

INTRODUCTION

This study compared the accuracy of three dimensional (3D) mini-optical navigation and accelerometer-based portable navigation systems for cup positioning during a total hip arthroplasty (THA) in the supine position.

MATERIALS AND METHODS

This retrospective cohort study assessed data for 77 hips using 3D mini-optical navigation (n = 37) and accelerometer-based portable navigation (n = 40). The patients underwent THA through the mini-anterolateral approach in the supine position using a portable navigation system. We assessed the preoperative target angles, recorded intraoperative cup angles, postoperative CT imaging angles, cup angle measurement errors, and other clinical parameters.

RESULTS

The mean absolute differences in radiographic inclination were similar between 3D mini-optical navigation and accelerometer-based portable navigation systems during THA in the supine position (2.8° ± 1.7° vs 2.8° ± 1.9°, p = 0.637). The mean absolute differences in radiographic anteversion were also similar (2.6° ± 2.3° vs 2.5° ± 1.9°, p = 0.737). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of > 5°) was significantly associated with body mass index (BMI) in accelerometer-based portable navigation but not in 3D mini-optical navigation.

CONCLUSIONS

This is the first study to compare the accuracy of cup positioning between 3D mini-optical and accelerometer-based navigations in THA in the supine position. Both portable navigation systems accurately identified the orientation of cup placement. The accuracy of 3D mini-optical navigation is not affected by high BMI and may be preferred over other options in such patients.

Augmented Reality: Mapping Methods and Tools for Enhancing the Human Role in Healthcare HMI

Background: Augmented Reality (AR) represents an innovative technology to improve data visualization and strengthen the human perception. Among Human–Machine Interaction (HMI), medicine can benefit most from the adoption of these digital technologies. In this perspective, the literature on orthopedic surgery techniques based on AR was evaluated, focusing on identifying the limitations and challenges of AR-based healthcare applications, to support the research and the development of further studies. Methods: Studies published from January 2018 to December 2021 were analyzed after a comprehensive search on PubMed, Google Scholar, Scopus, IEEE Xplore, Science Direct, and Wiley Online Library databases. In order to improve the review reporting, the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines were used. Results: Authors selected sixty-two articles meeting the inclusion criteria, which were categorized according to the purpose of the study (intraoperative, training, rehabilitation) and according to the surgical procedure used. Conclusions: AR has the potential to improve orthopedic training and practice by providing an increasingly human-centered clinical approach. Further research can be addressed by this review to cover problems related to hardware limitations, lack of accurate registration and tracking systems, and absence of security protocols.