Pelvic pitch and roll during total hip arthroplasty performed through a posterolateral approach. A potential source of error in free-hand cup positioning

Accelerometer-based portable navigation system shows no superior accuracy over pelvic alignment guide for acetabular cup placement in total hip arthroplasty in lateral decubitus position

BACKGROUND

Total hip arthroplasty (THA) using a portable navigation system (PNS) incurs costs per procedure. However, it does not require a large console. This study aimed to compare the accuracy of acetabular cup placement using a pelvic alignment guide (PAG) attached to the pelvis and an accelerometer-based PNS in THA performed in the lateral decubitus position.

METHODS

We retrospectively analyzed 100 hips that underwent primary THA in the lateral decubitus position between July 2018 and January 2021. The PAG was used in 50 hips, whereas the PNS was used in the other 50. Cup placement accuracy was measured using postoperative computed tomography scans, comparing errors in inclination and anteversion angles. The surgical time, blood loss, and complications were recorded. The follow-up period was at least 2 years in all cases.

RESULTS

The mean absolute error of the inclination angle was similar between the groups (the PAG group: 3.7° ± 2.3° [range, 0.0-9.0]; the PNS group: 3.7° ± 2.3° [range, 0.2-10.5], p = 0.705). The mean absolute error of the anteversion angle was significantly smaller in the PAG group than in the PNS group (3.0° ± 2.4° [range, 0.0-9.7] vs. 6.5° ± 4.8° [range, 0.3-17.3], p < 0.001). The PAG group had a higher proportion of hips within 5° and 10° of the target angle (64 vs. 42%, P = 0.028, and 100 vs. 74%, p < 0.001, respectively). The PNS group had six hips with anteversion errors of 15° or more. Surgical time and blood loss were lower in the PAG group. The PNS group had one dislocation, whereas the PAG group did not.

CONCLUSION

The accelerometer-based PNS did not demonstrate superior cup alignment accuracy compared to the PAG in THA performed in the lateral decubitus position. This finding informs surgeons that computer-assisted surgery is not necessarily superior to conventional THA using a PAG.

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.

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.

Optimization of Acetabular Cup Abduction by Adjusting Pelvic Pitch

Background

The purposes of this study were to determine the accuracy of our cup positioning method and to evaluate the dislocation rate after total hip arthroplasty (THA).

Methods

After positioning the patient in the lateral decubitus position on the operation table, an anteroposterior view of the hip was taken. The pelvic pitch was measured on the X-ray. A positive pitch was defined as the caudal rotation of the upper hemipelvis. Our target abduction of the cup was 43°. We used the cup holder to guesstimate the cup abduction. In a preliminary study, we found that the weight of the cup holder increased the pelvic pitch by 5°. Thus, the target abduction of the cup holder was calculated by a formula: 43° - pelvic pitch - 5°. During the cup insertion, the cup holder was anteverted to the calculated target according to the concept of combined anteversion. We evaluated 478 THAs (429 patients), which were done with the use of the method.

Results

The mean cup abduction was 43.9° (range, 32.0°-53.0°) and the mean error of cup abduction was 2.4° (standard deviation [SD], 2.0°; range, 0.0°-11.0°). The mean cup anteversion was 28.5° (range, 10.0°-42.0°) and the mean error of cup anteversion was 6.7° (SD, 5.2°; range, 0.0°-27.6°). Of all, 82.4% of the cups (394 / 478) were within the safe zone: 30°-50° abduction and 10°-35° anteversion. During 2- to 5-year follow-up, no hip dislocated.

Conclusions

Our adjusting method according to the pelvic pitch can be a reliable option for optimizing the cup abduction in THA.

Measurement accuracy of the acetabular cup position using an inertial portable hip navigation system with patients in the lateral decubitus position

Accurate cup placement is critical to ensure satisfactory outcomes after total hip arthroplasty. Portable hip navigation systems are novel intraoperative guidance tools that achieve accurate cup placement in the supine position; however, accuracy in the lateral decubitus position is under debate. A new inertial portable navigation system has recently become available. The present study investigated the accuracy of measurements of the cup position in 54 patients in the lateral decubitus position using this system and compared it with that by a goniometer. After cup placement, cup abduction and anteversion were measured using the system and by the goniometer, and were then compared with postoperatively measured angles. Absolute measurement errors with the system were 2.8° ± 2.6° for cup abduction and 3.9° ± 2.9° for anteversion. The system achieved 98 and 96% measurement accuracies within 10° for cup abduction and anteversion, respectively. The system was more accurate than the goniometer for cup anteversion (p < 0.001), but not for abduction (p = 0.537). The system uses a new registration method of the pelvic reference plane and corrects intraoperative pelvic motion errors, which may affect measurement accuracy. In the present study, reliable and reproducible intraoperative measurements of the cup position were obtained using the inertial portable navigation system.

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.

Quantifying anterior pelvic roll during total hip arthroplasty in the lateral decubitus position

BACKGROUND

Unintended pelvic positional change is an acknowledged intra-operative problem for hip arthroplasty, seen commonly with procedures performed in the lateral position. If unrecognised, such changes can dramatically alter final acetabular component anteversion potentially resulting in suboptimal construct performance. It has previously been suggested that pelvic roll of just 13° may be enough to place an otherwise perfectly orientated cup outside of conventional ± 10° safe zones. Using the real-time tracking capacity of a commercially available optical navigation system, we aimed to accurately quantify pelvic roll occurring during total hip arthroplasties (THAs) performed in the decubitus position.

METHODS

Prospectively collected data for 107 consecutive, unilateral, THAs were interrogated to determine the magnitude of pelvic movement around a central longitudinal axis (i.e. AP roll). Correlation statistics with patient age and body mass index (BMI) were also calculated.

RESULTS

A mean pelvic roll of 9.5° was observed, being anterior in 96% of cases. Of these, 18.3% of hips had a magnitude of roll greater than 13°. There were no statistically significant independent correlations observed between age (p = 0.87) or BMI (p = 0.59) and mean roll.

CONCLUSIONS

Errors in achieving acetabular target version may result in numerous post-operative concerns including instability/dislocation, bearing wear, squeaking, range-of-movement limitation and increased revision rate. In a general cohort, our findings suggest a mean anterior pelvic roll during THA of nearly 10°. Without purposeful correction, this may cause substantial deviation from intended target positions. Future work is indicated to map changing pelvic roll during THA which is likely to follow a nonlinear trajectory. Level of evidence: IV. .

Use of Surgical Approach Is Not Associated With Instability After Primary Total Hip Arthroplasty: A Meta-analysis Comparing Direct Anterior and Posterolateral Approaches

INTRODUCTION

Posterolateral approach (PA) has been historically associated with an increased risk of dislocation after primary total hip arthroplasty (THA), especially when compared with the direct anterior approach (DAA). However, current evidence is inconsistent regarding the risk of dislocation with either approach. The purpose of this study is to determine whether surgical approach influences joint stability.

METHODS

A systematic search in PubMed, MEDLINE, and Embase databases was performed. Randomized controlled trials (RCTs) and non-RCTs comparing DAA with PA in primary THA were included. Pooled effect measure of risk differences, relative risk and mean differences for postoperative dislocation, acetabular implant positioning, and leg length discrepancy were calculated.

RESULTS

Twenty-five studies (5 RCTs and 20 non-RCTs) of 7,172 THAs were assessed. There were no significant differences in dislocation rates between approaches (risk difference = -0.00, 95% confidence interval: -0.01 to 0.00; P = 0.92; I2 = 0%). Results were similar in the subgroup analysis of RCTs (P = 0.98), posterior soft-tissue repair (P = 0.50), and learning curve (P = 0.77). The acetabular implant was better positioned within the safe zone in the DAA group (relative risk = 1.17; 95% confidence interval: 1.03 to 1.33; P = 0.01), but no significant differences were found in cup inclination (P = 0.8), anteversion (P = 0.10), and leg length discrepancy (P = 0.54).

CONCLUSION

Dislocation rates after THA are not different between DAA and PA. Furthermore, no differences in the rate of dislocation were associated with cup positioning or surgical factors related with hip instability. Therefore, the surgical approach has little influence in prosthesis instability after primary THA.

LEVEL OF EVIDENCE

Level III.

Accuracy of acetabular cup placement using an angle-adjusting alignment guide with laser pointer in total hip arthroplasty

PURPOSE

To evaluate cup-positioning accuracy in total hip arthroplasty (THA) using a novel angle-adjusting alignment guide with laser pointer and determine whether level of surgical experience affects accuracy of cup placement or not.

METHODS

We included 117 hips in 104 patients who underwent THA using the novel guide. We retrospectively reviewed 44 hips in 40 patients who underwent THA before the novel guide was introduced. We compared differences in cup angles between the novel guide group and the conventional guide group as well as the discrepancies in targeted angles between the experienced surgeon group and the inexperienced surgeon group.

RESULTS

There were 114/117 hips (97.4%) within the Lewinnek safe zone in the novel guide group and 32/44 hips (72.7%) within the safe zone in the conventional guide group. There were significantly fewer outliers in the novel guide group (p < 0.001). In the experienced surgeon group, the mean absolute errors in inclination and anteversion were 2.0 ± 1.7° and 2.1 ± 2.3°, respectively; which were not significantly different from those in the inexperienced surgeon group (2.3 ± 2.1° and 2.8 ± 2.3°, respectively).

CONCLUSION

The novel angle-adjusting alignment guide with laser pointer is a simple tool that provides better accuracy of cup position than that obtained using conventional guides. Accurate cup placement is possible using the novel guide, regardless of surgeons' experience.

Robot-Assisted Total Hip Arthroplasty for Arthrodesed Hips

Background

Conversion of arthrodesed hips to total hip arthroplasty (THA) remains technically demanding. This study aims to evaluate the safety and efficacy of robot-assisted THA in arthrodesed hips.

Methods

We retrospectively analyzed 45 ankylosing spondylitis patients with hip arthrodesis in the Chinese PLA General Hospital between August 2018 and August 2019. All surgeries were carried out by one single surgeon. The patients were followed at 3 months after surgery. Gender, body mass index, angle of hip arthrodesis, operating time, intraoperative fluoroscopic times, postoperative length of hospitalization, cup positioning, postoperative leg length discrepancy, offset discrepancy, intraoperative and postoperative complications, and postoperative Harris Hip Score were collected for all patients.

Results

Twenty-two patients (35 hips) who underwent robot-assisted THA and 23 patients (37 hips) who underwent manual THA were enrolled in this study. There were no significant differences in demographics and arthrodesed angles between the two groups. The fluoroscopic times during manual THA were significantly higher than those during robot-assisted THA (2.16±1.61 vs 0.47±0.61, respectively, p=0.000). In the robotic group, the percentage of acetabular cups within the safe zone was significantly greater than in the manual group (94.29% vs 67.56%, respectively, p=0.042). For manual THA, the anteversions were significantly different between the left and right sides (21.14±7.86 vs 16.00±6.32, respectively, p=0.042); however, no such significant difference was found in robot-assisted THA.

Conclusion

Compared with manual THA for arthrodesed hips, robot-assisted THA had significant advantages in improving the frequency of achieving cup positioning within the target zone with diminished radiation dose and no increase in operating time.

Acetabular positioning is more consistent with the use of a novel miniature computer-assisted device

INTRODUCTION

Computer-assisted surgery (CAS) relying on registration of the anterior pelvic plane (APP) allows precise acetabular component placement. We determined the variability of cup placement in patients who underwent THA with and without the use of CAS that does not rely on the registration of APP.

METHODS

Fifty-one patients who underwent staged-bilateral THAs, one without CAS (control), and a subsequent one with CAS (study group), were included. Acetabular inclination and anteversion were measured on standardized post-operative radiographs. Variance in cup position and Lewinnek's zone proportionality were compared between the groups. Multiple regressions were performed to identify factors affecting variability in acetabular component placement.

RESULTS

The mean inclination for the control and study group was 42.7° (SD 4.5) and 42.5° (SD 2.9), respectively. The inclination variance was 20.5° and 8.2° respectively (p = < 0.001). Cup inclination was more consistent in the study than in the control group (deviation from the mean: 2.3° vs. 3.8°, p < 0.001). The mean anteversion for the control and the study group was 25.5° (SD 7.4) and 26.8° (SD 4.3), respectively. The anteversion variance was 54.2° and 18.2° respectively (p = <0.001). Consistency in cup anteversion was significantly improved with CAS (deviation from the mean: 3.4° vs. 5.8°; p = 0.002). Lewinnek's zone proportionality was not affected by the use of  CAS. In the linear regression analysis, CAS significantly increased consistency in cup inclination (p = 0.01). Patient's factors including BMI and laterality affected consistency of cup placement.

CONCLUSION

CAS without referencing the APP allows a more consistent orientation of the acetabular component when compared to freehand placement.