Efficacy of the Anatomical-Pelvic-Plane Positioner in 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.

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.

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.

Validity and application of Doiguchi's pelvic tilt measurement method

BACKGROUND

The validity of Doiguchi's pelvic tilt measurement method has not been proven. The objective in our study was to validate the method.

METHODS

Our investigation included 73 total hip arthroplasties (THAs) performed using our cup placement procedure from July 2020 to November 2021. Pelvic tilt formed by the pubic symphysis and sacral promontory (PT_PS) in supine and lateral positions was calculated by two methods (the Doiguchi method and the digital reconstructed radiograph (DRR) method using a 3D computer templating system) based on the transverse and longitudinal diameters of the pelvic ring measured immediately before THA.

RESULTS

There was a strong/moderate correlation in the values of PT_PS between the Doiguchi and DRR methods. However, the value of PT_PS calculated by the Doiguchi method was significantly lower than that calculated by DRR, and there was a partially direct match. On the other hand, there was no significant difference in the value of PT change from supine to lateral position between the Doiguchi and DRR methods. The PT changes based on both methods were strongly correlated, and the PT change calculated by the Doiguchi method was almost identical to that calculated by the DRR method.

CONCLUSIONS

Doiguchi's pelvic tilt measurement method was validated for the first time. These results demonstrated that the ratio of the transverse and longitudinal diameters of the pelvic ring was an important factor defining the change in pelvic tilt. The slope in the linear function of the Doiguchi method was found to be almost the correct value, although the intercept of the linear function exhibited individual differences.

A comparison of accuracy and safety between stem-first and cup-first total hip arthroplasty: a prospective randomised controlled trial

BACKGROUND

The combined anteversion theory to prevent impingement in total hip arthroplasty (THA) has been proposed. However, because stem-anteversion is influenced by the native femoral anteversion and the stem flexion/extension angle, it is often difficult to adjust stem anteversion during surgery. Therefore, the stem-first (combined anteversion) technique may be useful to adjust and achieve appropriate cup anteversion during surgery with respect to the implanted stem anteversion angle. However, the technique may adversely affect cup or stem angle accuracy and result in intra-operative bleeding, post-operative adverse events, and prolonged operative time. It is inconclusive whether either the stem-first or cup-first technique is safe or accurate. Therefore, this study assessed the accuracy and safety of stem-first THA compared to those of cup-first THA.

MATERIALS AND METHODS

This prospective randomised controlled trial analysed 114 patients who were randomly divided into 2 groups (stem-first group: n = 57, cup-first group (control group): n = 57). Primary outcomes included cup and stem angle, the discrepancies from the targeted angle and combined anteversion (evaluated via CT at 3 months postoperatively). Secondary outcomes included intraoperative blood loss, operative time, WOMAC, and adverse events.

RESULTS

There were no significant differences in age, gender, BMI or in the primary and secondary outcomes between the 2 groups.

CONCLUSIONS

Performing stem-first in THA did not adversely affect cup and stem angle accuracy, or result in intraoperative bleeding, prolongation of operative time, or postoperative adverse events. Thus, performing stem-first may be advantageous for achieving combined anteversion theory.

TRIAL REGISTRATION

University Hospital Medical Information Network (UMIN) registration number UMIN000025189.

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.

Pelvic stability during simulated total hip arthroplasty motions: Comparing different hip positioners

Introduction

Total hip arthroplasty (THA) requires forceful maneuvers that can cause the pelvis to shift from its original position. Various methods for stabilizing the pelvis in the lateral decubitus position exist, but there is limited data quantifying the relative stability of each hip positioner. We sought to quantify the pelvic movement that occurred in four commercially available hip positioners during surgeon induced motion of the hip.

Methods

An infrared marker was attached to the ilium of a cadaver secured in the lateral decubitus position. Four commercially available hip positioners were used for positioning: Beanbag, Pegboard, Stulberg, and ExactFit. Rotation and translation was captured using an infrared marker and camera system while the hip was moved through six motions (Flexion, Extension, Internal Rotation, External Rotation, Push, and Pull).

Results

The Beanbag had the greatest amount of rotation and translation of the pelvis, with maximum hip rotation of 41.5°. The Stulberg and Pegboard positioners showed intermediate stability, with a maximum rotation of 7.8° and 17.1°, respectively. The ExactFit hip positioner resulted in the least amount of motion of the pelvis, with a maximum rotation of the pelvis of up to 3.2°. Of the simulated motions performed, internal rotation and flexion of the hip led to the greatest changes in pelvic rotation and translation.

Conclusion

The ExactFit positioner was associated with the smallest amount of pelvic motion during simulated motions of hip arthroplasty, followed by the Stulberg, Pegboard, and Beanbag positioners. Further studies are required to correlate this information with clinical outcomes following total hip arthroplasty.

Accurate cup placement using a portable navigation system during total hip arthroplasty based on pelvic orientation in the lateral decubitus position

BACKGROUND

We previously proposed an accurate cup placement procedure using a portable navigation system (PNS) for total hip arthroplasty (THA) in the lateral decubitus position; however, as the accuracy of our proposed procedure has not been shown, the aim of this study was to demonstrate the accuracy.

METHODS

We prospectively analyzed 79 hips treated with primary THA; 40 hips treated until June 2020 were included in the conventional procedure (CP) group, and 39 hips treated from July 2020 were included in the modified procedure (MP) group. In the MP, pelvic orientation is considered to the set coordinate axes in addition to the CP using the PNS. The accuracy was based on the difference between the navigation record (NR) and postoperative computed tomography measurement.

RESULTS

The radiographic inclination (RI) and anteversion (RA) accuracies were 1.55° and 2.14°, respectively, in the MP group and 3.03° and 6.20°, respectively, in the CP group (p < 0.001). The error was within 5° of the NR for both the RI and RA in 34 in the MP group (87.2%) and 14 in the CP group (35.0%) (p < 0.001). The error was within 5° of the target angle (RI 40°, RA 15°) for both the RI and RA in 29 hips in the MP group (74.7%) and 12 in the CP group (30.0%) (p < 0.001).

CONCLUSIONS

Our procedure with the consideration of pelvic orientation achieved dramatically improved the accuracy of PNS and was suitable to facilitate accurate cup placement.

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

BACKGROUND

There have been no studies regarding the effectiveness of augmented reality (AR)-based portable navigation systems compared with accelerometer-based portable navigation systems in total hip arthroplasty (THA).

METHODS

We retrospectively compared THAs performed using an AR-based portable navigation system (n = 45) and those performed using an accelerometer-based portable navigation system (n = 42). All THAs were performed with the patient in the lateral decubitus position. The primary outcome was the absolute difference between cup placement angles displayed on the navigation screen and those measured on postoperative X-ray.

RESULTS

The mean absolute differences were significantly smaller in the AR-based portable navigation system group than the accelerometer-based portable navigation system group in radiographic inclination (2.5° ± 1.7° vs 4.6° ± 3.1°; 95% confidence interval 1.1°-3.2°, P < .0001). Similarly, the mean absolute differences were significantly better in the AR-based portable navigation system group in radiographic anteversion (2.1° ± 1.8° vs 6.4° ± 4.2°; 95% confidence interval 3.0°-5.7°, P < .0001). Neither hip dislocation, surgical site infection, nor other complications associated with use of the navigation system occurred in either group.

CONCLUSION

The AR-based portable navigation system may provide more precise acetabular cup placement compared with the accelerometer-based portable navigation system in THA.

Proposal of accurate cup placement procedure during total hip arthroplasty based on pelvic tilt discrepancies in the lateral position

By combining the anatomical-pelvic-plane (APP) positioner with a newly improved navigation system during total hip arthroplasty (THA), it is theoretically possible to determine cup orientation based on the APP while tracking pelvic movement. The purpose of this study was to determine the navigation accuracy and whether the error is related to the pelvic position fixed by the positioner. Fifty hips that underwent primary THA between 2018 and 2020 were analysed. The accuracy was 2.34° at radiographic inclination (RI) and − 5.01° at radiographic anteversion (RA), and the error was within 10° at both RI and RA in only 40 of 50 hips (80.0%). The discrepancy in pelvic sagittal tilt was correlated with the cup orientation error and especially strongly correlated with the RA error (r = − 0.751, p < 0.001). When RI and RA were calculated using a correction formula to determine the true cup orientation based on the pelvic tilt discrepancies, the error in both RI and RA was within 10° in all cases (100%). The navigation accuracy is related to the pelvic position fixed by the positioner, and the correction formula for the target angle that considers pelvic tilt discrepancies can lead to accurate cup placement in the future.

Pelvic Tilt Reduces the Accuracy of Acetabular Component Placement When Using a Portable Navigation System: An In Vitro Study

Background

A portable navigation system (PNS) was recently introduced. The PNS enables surgeons to place the acetabular component accurately. While the margin of the error for the cup abduction and anteversion was larger than the values obtained from a computed tomography-based navigation system. We hypothesized that the accuracy of the PNS might be affected by pelvic tilt.

Material and Methods

A bone substitute model of the pelvis was used in this in vitro study. We set the acetabular component using PNS. We set the acetabular component angle after changing the sagittal, coronal, and axial pelvic tilt. We calculated the difference between the angle displayed on the PNS display and the actual angle of the acetabular component. The difference in inclination angle was defined as ΔRI, and the difference in the anteversion angle was defined as ΔRA. We evaluated the trends in this ΔRI and ΔRA due to the pelvic tilt.

Results

In this in vitro study, the placement of the acetabular component was accurate in the neutral position; ΔRI was 0.5 ± 0.7° and ΔRA was 1.0 ± 0.7°. Sagittal pelvic tilt and axial pelvic tilt increased both the ΔRA and ΔRI (P = .017). Coronal tilt increased ΔRI but did not change ΔRA.

Conclusions

While the PNS may enable surgeons to place accurate component placement in the neutral position, its accuracy decreased by pelvic tilt. The surgeons should use a solid pelvic lateral positioner for reducing discrepancies in pelvic tilt when using the PNS in the lateral decubitus position.

Changes in patient-perceived leg length discrepancy following total hip arthroplasty

PURPOSE

Leg length discrepancy (LLD) after total hip arthroplasty (THA) prevents functional recovery and reduces patient satisfaction. We investigated impact of changes in patient-perceived LLD on patient satisfaction and walking ability.

METHODS

one hundred and forty-nine patients with unilateral hip osteoarthritis undergoing THA from 2014 to 2017, (125 women, 24 men; average age, 68.5 years) with an objective LLD < 1 cm were included. Outcome measures included the patient-perceived LLD, Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index, 10-m walking speed, and affected leg loading rate, assessed preoperatively and at 3 weeks, 3 months, and 1 year postoperatively.

RESULTS

The absolute patient-perceived LLD (mean ± SD) (the number of patients with perceived LLD > 5 mm) were 6.4 ± 9.6 mm [88 patients (59%)] preoperatively; and 2.2 ± 4.0 mm [48 (32%); p < 0.001], 0.7 ± 2.3 mm [17 (11%); p < 0.001], and 0.4 ± 1.6 mm [10 (7%); p = 0.095] at 3 weeks, 3 months, and 1 year postoperatively, respectively. All outcome measures improved over time. One year postoperatively, a weak positive correlation between the patient-perceived LLD and WOMAC or 10-m walking speed (r = 0.24, 0.23, respectively) was found. The risk of patient-perceived LLD persisting > 1 year postoperatively was 5.5-fold higher in patients who exhibited it at 3 months and those with a WOMAC score > 10 at 3 months postoperatively, using multivariate logistic regression.

CONCLUSION

Achieving a post-THA objective LLD < 1 cm significantly reduced the patient-perceived LLD up to 3 months postoperatively. The residual patient-perceived LLD at 1 year postoperatively was predicted from the WOMAC score or the presence of patient-perceived LLD at 3 months after THA.

LEVEL OF EVIDENCE

Therapeutic level IV.

Risk factors for pressure ulcers from the use of a pelvic positioner in hip surgery: a retrospective observational cohort study in 229 patients

Background

Intraoperatively acquired pressure ulcers are serious postsurgical complications requiring additional treatment, reoperation, and extended hospitalization. No study has investigated the frequency of the ulcers caused by compression with a pelvic positioner, which is used in hip surgeries to stabilize patients in the lateral decubitus position.

Methods

This retrospective study investigated the risk factors and the frequency of the ulcers caused by the use of pelvic positioners in hip surgeries. The records of patients who underwent surgical procedures under general anesthesia at our institution between January 1, 2016 and March 31, 2018 were reviewed. The inclusion criterion for the assessment of risk factors was hip surgery in the lateral decubitus position stabilized by a pelvic positioner. The exclusion criteria were patients with trauma, missing data, or a pre-existing pressure ulcer. Finally,.the study included 229 patients (265 hip surgeries). All the patients were positioned in the lateral decubitus position with the assistance of either a pelvic positioner, which had a single support fixture located over the pubic symphysis or a double support fixture located over the bilateral anterior superior iliac spine. Intraoperatively acquired pressure ulcers were diagnosed when ulcers were absent on admission and the redness that was observed immediately after surgery remained after 24 h. Multivariate analysis was used to identify factors associated with an increased risk for ulcers.

Results

Ulcers developed in 8 of 1810 (0.44%) patients who underwent orthopedic surgery. Seven of the 265 (2.64%) patients who underwent hip surgery in the lateral decubitus position stabilized by a pelvic positioner developed ulcers. All ulcers were located on areas of the body that were compressed by the pelvic positioner. After identifying controls for patient height (less than 154 cm), surgery duration (longer than 180 min), blood loss (more than 355 ml), and type of pelvic positioner used, we identified the independent risk factors for ulcers to be patient height < 154 cm (adjusted odds ratio, 12.8; p-value, 0.032) and the use of pelvic positioners with pubic bone support (adjusted odds ratio, 10.53; p-value, 0.047).

Conclusion

The use of pelvic positioners with pubic bone support should be avoided in patients with a height of < 154 cm to decrease the risk of ulcers.

Patient positioning and cup orientation during total hip arthroplasty: assessment of current UK practice

INTRODUCTION:

Acetabular cup orientation during total hip arthroplasty (THA) remains a challenge. This is influenced by patient positioning during surgery and the method used to orientate the acetabular cup. The aim of this study was to assess current UK practice for patient positioning and cup orientation, particularly with respect to patient supports and techniques used to achieve target version and inclination.

METHODS:

A literature review and pilot study were initially conducted to develop the questionnaire, which was completed by British Hip Society members ( n = 183). As the majority of THA surgical procedures within the UK are performed with the patient in lateral decubitus, orthopaedic surgeons who operated with the patient in the supine position were excluded ( n = 18); a further 6% were incomplete and also excluded ( n = 11).

RESULTS:

Of those who operated in lateral decubitus, 76.6% ( n = 118/154) used the posterior approach. Only 31% ( n = 47/154) considered their supports to be completely rigid. More than 35% ( n = 55/154) were unhappy with the supports that they presently use. The most common methods for controlling operative inclination and version were a mechanical alignment guide (MAG; n = 78/154; 50.6%) and the transverse acetabular ligament (TAL; n = 82/154; 53.2%); 31.2% (48/154) used a freehand technique to control operative inclination.

CONCLUSION:

Limited studies have been conducted whereby patient supports have been analysed and key design principles outlined. With 35.7% of the orthopaedic surgeons surveyed having issues with their current supports, a greater awareness of essential characteristics for patient supports is required.

Efficacy of a Pelvic Lateral Positioner With a Mechanical Cup Navigator Based on the Anatomical Pelvic Plane in Total Hip Arthroplasty

BACKGROUND

The acetabular component orientation in total hip arthroplasty (THA) is of critical importance to the good clinical results. However, traditional widely used cup alignment guides for cup placement are reported to be relatively unreliable. The present study aims at comparing a novel cup alignment guide, which can be attached to our anatomical pelvic plane (APP) pelvic lateral positioner for reducing discrepancies in sagittal pelvic tilt and indicate a targeted cup angle based on the APP, with a conventional cup alignment guide.

METHODS

The subjects were 136 hips of 136 patients who underwent unilateral THA using the APP positioner. The procedure was performed with the conventional cup alignment guide (conventional group; 60 hips) and with the novel cup navigator (mechanical navigator group; 76 hips). Postoperative cup angles and discrepancies of postoperative cup angles (inclination and anteversion angles) from the targeted angles were compared between the 2 groups to evaluate the usefulness of these navigators.

RESULTS

The mean cup angles in the conventional group were 39.0° ± 5.3° for the inclination angle and 21.7° ± 6.4° for the anteversion angle, whereas those in the mechanical navigator group were 40.6° ± 3.2° and 18.3° ± 4.6°, respectively (P = .018, P < .0001). The discrepancies from the targeted angles were 3.5° ± 3.1° for the inclination angle and 4.6° ± 3.4° for the anteversion angle in the conventional group and 2.3° ± 2.3° and 3.2° ± 2.7°, respectively, in the mechanical navigator group (P = .020, P = .012).

CONCLUSION

The mechanical cup navigator easily attachable to the APP positioner is a tool that can improve the accuracy of cup placement in a simple, economical, and noninvasive manner in THA via the lateral position.