A new method of registration in navigated hip arthroplasty without the need to register the anterior pelvic plane

Patient-reported outcome differences for navigated and robot-assisted total hip arthroplasty frequently do not achieve clinically important differences: a systematic review

INTRODUCTION

Total hip arthroplasty (THA) using computer-assisted navigation (N-THA) and robot-assisted surgery (RA-THA) has been increasingly adopted to improve implant positioning and offset/leg-length restoration. Whether clinically meaningful differences in patient-reported outcomes (PROMs) compared to conventional THA (C-THA) are achieved with intraoperative technology has not been established. This systematic review aimed to assess whether published relative PROM improvements with technology use in THA achieved minimal clinically important differences (MCIDs).

METHODS

PubMed/MEDLINE/Cochrane Library were systematically reviewed for studies comparing PROMs for primary N-THA or RA-THA with C-THA as the control group. Relative improvement differences between groups were compared to established MCID values. Reported clinical and radiographic differences were assessed. Review of N-THA and RA-THA literature yielded 6 (n = 2580) and 10 (n = 2786) studies, respectively, for analyses.

RESULTS

Statistically significant improvements in postoperative PROM scores were reported in 2/6 (33.3%) studies comparing N-THA with C-THA, though only 1 (16.7%) reported clinically significant relative improvements. Statistically significant improvements in postoperative PROMs were reported in 6/10 (60.0%) studies comparing RA-THA and C-THA, though none reported clinically significant relative improvements. Improved radiographic outcomes for N-THA and RA-THA were reported in 83.3% and 70.0% of studies, respectively. Only 1 study reported a significant improvement in revision rates with RA-THA as compared to C-THA.

CONCLUSIONS

Reported PROM scores in studies comparing N-THA or RA-THA to C-THA often do not achieve clinically significant relative improvements. Future studies reporting PROMs should be interpreted in the context of validated MCID values to accurately establish the clinical impact of intraoperative technology.

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.

Anterior pelvic plane estimation for total hip arthroplasty using a joint ultrasound and statistical shape model based approach

Orienting properly the prosthetic cup in total hip arthroplasty is key to ensure the postoperative stability. Several navigation solutions have been developed to assist surgeons in orienting the cup regarding the anterior pelvic plane (APP), defined by both anterior superior iliac spines (ASIS) and the pubic symphysis. However acquiring the APP when the patient is ready for surgery, i.e., mainly in lateral decubitus, is difficult due to the contralateral ASIS being against the operating table. We propose a method to determine the APP from both (1) alternative anatomical landmarks which are easy to acquire with a navigated ultrasound probe and (2) a Statistical Shape Model (SSM) of the pelvis. After creating a pelvic SSM from 40 data, a SSM-based morphometric analysis has been carried out to identify the best anatomical landmarks allowing the easy determination of the APP. The proposed method has then been assessed with both in silico and in vivo experiments on respectively forty synthetic data, and five healthy volunteers. The in silico experiment shows the feasibility to determine the APP with an average error of 4.7^∘ by only acquiring the iliac crest, the anterior superior iliac spine, the anterior inferior iliac spine, and the pubic symphysis. The average in vivo error using the ultrasound modality was 7.3^∘ with an estimated impact on both the cup anteversion and inclination of 4.0^∘ and 1.7^∘ respectively. The proposed method shows promising results that could allow the determination of the APP in lateral decubitus with a clinically acceptable impact on the computation of the cup orientation.

Spinopelvic Relationship and Its Impact on Total Hip Arthroplasty

The dynamic, complex interaction among the spine, pelvis, and hip is often underappreciated, yet understanding it is vital for both arthroplasty and spinal surgeons. There is an increasing incidence of degenerative hip and spinal pathologies as a result of the ageing population. Furthermore, hip pathology can cause spine pathology and vice versa through “hip-spine” and “spine-hip syndrome.” Consequently, total hip arthroplasty (THA) and spinal fusion surgery, which both affect spinopelvic mobility, are also on the rise. Alteration in spinopelvic motion can affect the orientation of the acetabulum and, therefore, implant positioning in THA, leading to complications such as dislocation, impingement, aseptic loosening, and wear of components. This makes it imperative to assess spinopelvic motion and pelvic tilt prior to patients undergoing THA. In this paper, we explore how the surgeon should proceed to reduce risk of component malalignment, as well as the role of navigation systems in acetabular cup positioning.

Improving Acetabular Component Positioning in Total Hip Arthroplasty: A Cadaveric Study of an Inertial Navigation Tool and a Novel Registration Method

Background: Incorrect acetabular component positioning in total hip arthroplasty (THA) has been associated with poor outcomes. Computer-assisted hip arthroplasty increases accuracy and consistency of cup positioning compared to conventional methods. Traditional navigation units have been associated with problems such as bulkiness of equipment and reproducibility of anatomical landmarks, particularly in obese patients or the lateral position. Purpose: We sought to evaluate the accuracy of a novel miniature inertial measurement system, the Navbit Sprint navigation device (Navbit, Sydney, Australia), to navigate acetabular component positioning in both the supine and lateral decubitus positions. We also aimed to validate a new method of patient registration that does not require acquisition of anatomical landmarks for navigation. Methods: We performed THA in a cadaveric study in supine and lateral positions using Navbit navigation to record cup position and compared mean scores from 3 Navbit devices for each cup position on post-implantation CT scans. Results: A total of 11 cups (5 supine and 6 lateral) were available for comparison. A difference of 2.34° in the supine direct anterior approach when assessing acetabular version was deemed to be statistically but not clinically significant. There was no statistically significant difference between CT and navigation measurements of cup position in the lateral position. Conclusion: This cadaveric study suggests that a novel inertial-based navigation tool is accurate for cup positioning in THA in the supine and lateral positions. Furthermore, it validates a novel registration method that does not require the identification of anatomical landmarks.

Accuracy of a novel accelerometer-based navigation (Naviswiss) for total hip arthroplasty in the supine position

BACKGROUND

This study aimed to determine the accuracy of acetabular cup insertion using a novel accelerometer-based navigation system in total hip arthroplasty (THA).

METHODS

A single-surgeon study was conducted in which 62 prospective patients with navigation and 42 retrospective patients without navigation in a supine position were compared. Absolute values for errors of radiographic inclination and anteversion were calculated. Navigation error was also calculated. Factors that affected absolute value of navigation error in cup alignment were determined.

RESULTS

In the navigation group, mean absolute errors for radiographic inclination and anteversion were 4.1° and 4.3°, respectively. In the control group, mean absolute errors were 6.6° in inclination (p < 0.01) and 5.9° in anteversion (p = 0.04). Mean absolute values of navigation error were 2.8° in inclination and 2.8°in anteversion. Factors affecting navigation errors were not found.

CONCLUSION

This novel accelerometer-based navigation system significantly increased the accuracy of cup placement during THA in the supine position.

Novel Measure of Acetabular Cup Inclination and Anteversion During Total Hip Arthroplasty

PURPOSE

The purposes of the present research were to assess the accuracy and usability of the inertial navigation system (INS).

MATERIALS AND METHODS

The accuracy of the device navigation subsystem was assessed using benchtop testing. The usability was assessed through simulated use with surgeons. These results were compared to recent cadaveric results for the same system.

RESULTS

The navigation subsystem had an overall mean absolute error of 1.21° and a maximum absolute error across all devices of 4.79°. The device was found to be usable and to add an estimated 7 minutes to surgery time.

CONCLUSION

The INS uses a novel approach to provide the surgeon with accurate and fast acetabular cup inclination and anteversion angles during THA.

Comparison of the accuracies of computed tomography-based navigation and image-free navigation for acetabular cup insertion in total hip arthroplasty in the lateral decubitus position

Image-free navigation has been proven as reliable as that using computed tomography (CT) in positioning the acetabular cup in total hip arthroplasty (THA), but previous studies rarely included hip dysplasia cases. The purpose of the present study was to determine the accuracies of CT-based navigation and image-free navigation for acetabular cup insertion, including hip dysplasia cases. Sixty-three hips were studied, including 57 with hip dysplasia. The hips were divided into two groups based on the registration point of image-free navigation. In Group I, the ipsilateral anterior superior iliac spine (ASIS) and the L5 spinous process were registered in 31 hips. In Group II, bilateral ASIS points were registered in 32 hips. Final component orientation was measured from postoperative CT scans. The accuracy of cup orientation was compared between CT-based and image-free navigation. In Group I, the cup inclination was more accurate with CT-based navigation (1.9°) than with image-free navigation (4.4°, p=.009). Cup anteversion was also more accurate with CT-based navigation (2.9°) than with image-free navigation (7.1°, p<.001). In Group II, the accuracies of cup inclination and anteversion showed no differences between CT-based and image-free navigation. The accuracy of cup positioning was better with CT-based navigation than with image-free navigation when the ipsilateral ASIS and L5 spinous process were digitized. However, accuracy was similar when bilateral ASIS points were digitized.

Evaluating Alternate Registration Planes for Imageless, Computer-Assisted Navigation During Total Hip Arthroplasty

BACKGROUND

Imageless computer navigation improves component placement accuracy in total hip arthroplasty (THA), but variations in the registration process are known to impact final accuracy measurements. We sought to evaluate the registration accuracy of an imageless navigation device during THA performed in the lateral decubitus position.

METHODS

A prospective, observational study of 94 patients undergoing a primary THA with imageless navigation assistance was conducted. Patient position was registered using 4 planes of reference: the patient's coronal plane (standard method), the long axis of the surgical table (longitudinal plane), the lumbosacral spine (lumbosacral plane), and the plane intersecting the greater trochanter and glenoid fossa (hip-shoulder plane). Navigation measurements of cup position for each plane were compared to measurements from postoperative radiographs.

RESULTS

Mean inclination from radiographs (41.5° ± 5.6°) did not differ significantly from inclination using the coronal plane (40.9° ± 3.9°, P = .39), the hip-shoulder plane (42.4° ± 4.7°, P = .26), or the longitudinal plane (41.2° ± 4.3°, P = .66). Inclination measured using the lumbosacral plane (45.8° ± 4.3°) differed significantly from radiographic measurements (P < .0001). Anteversion measured from radiographs (mean: 26.1° ± 5.4°) did not differ significantly from the hip-shoulder plane (26.6° ± 5.2°, P = .50). All other planes differed significantly from radiographs: coronal (22.6° ± 6.8°, P = .001), lumbosacral (32.5° ± 6.4°, P < .0001), and longitudinal (23.7° ± 5.2°, P < .0001).

CONCLUSION

Patient registration using any plane approximating the long axis of the body provided a frame of reference that accurately measured intraoperative cup position. Registration using a plane approximating the hip-shoulder axis, however, provided the most accurate and consistent measurement of acetabular component position.

Reduced Risk of Revision with Computer-Guided Versus Non-Computer-Guided THA: An Analysis of Manufacturer-Specific Data from the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man

Computer-assisted total hip arthroplasty (THA) is known to improve implantation precision, but clinical data demonstrating an improvement in survivorship and patient-reported outcome measures (PROMs) are lacking. Our aim was to compare the risk of revision, PROMs, and patient satisfaction between cohorts who underwent THA with and without the use of computer guidance.

Methods

We used the data set and linked PROM data of the National Joint Registry of England, Wales, Northern Ireland and the Isle of Man. Our sample included THAs performed for osteoarthritis using cementless acetabular components from a single manufacturer (cementless and hybrid THAs). An additional analysis was performed limiting the sample size to cementless-only THAs. The primary end point was revision (any component) for any reason. Kaplan-Meier survivorship analysis and an adjusted Cox proportional-hazards model were used.

Results

There were 41,683 non-computer-guided and 871 (2%) computer-guided cases included in our analysis of the cementless and hybrid group. There were 943 revisions in the non-computer-guided group and 7 in the computer-guided group. The cumulative revision rate at 10 years was 3.88% (95% confidence interval [CI]: 3.59% to 4.18%) for the non-computer-guided group and 1.06% (95% CI: 0.45% to 2.76%) for the computer-guided group. The Cox proportional-hazards model yielded a hazard ratio of 0.45 (95% CI: 0.21 to 0.96; p = 0.038). In the analysis of the cementless-only group, the cumulative revision rate at 10 years was 3.99% (95% CI: 3.62% to 4.38%) and 1.20% (95% CI: 0.52% to 3.12%) for the 2 groups, respectively. The Cox proportional-hazards model yielded a hazard ratio of 0.47 (95% CI: 0.22 to 1.01; p = 0.053). There was no significant difference in the 6-month Oxford Hip Score, the EuroQol-5 Dimension (EQ-5D) and EQ-VAS (Visual Analogue Scale) scores, and patient-reported success rates. Patient satisfaction (single-item satisfaction outcome measure) was higher in the computer-guided group, but this finding was limited by a reduced number of responses.

Conclusions

In our analysis, the use of computer-guided surgery was associated with a lower rate of revision at mean follow-up of 5.6 years. This finding was upheld when the sample was restricted to cementless-only THAs. Causality cannot be inferred in view of the observational nature of the study, and additional studies are recommended to validate these findings.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Lewinnek Safe Zone References are Frequently Misquoted

BACKGROUND

Optimal acetabular component orientation in total hip arthroplasty (THA) is a necessity in achieving a stable implant. Although there has been considerable debate in the literature concerning the safe zone, to date, there has not been any review to determine if these references are consistent with the definition applied by Lewinnek et al. in 1978. Therefore, this article aims to examine the available literature in the PubMed database to determine how often a correct reference to the safe zone as defined by Lewinnek was applied to discussions regarding THA.

METHODS

A search for literature in the PubMed database was performed for articles from 1978 to 2019. Search criteria included terms 'Lewinnek,' 'safe zone,' and 'total hip arthroplasty.' Exclusions included abstract-only articles, non-English articles, articles unrelated to THA, and those lacking full content.

RESULTS

A review of literature yielded 147 articles for inclusion. Overall, only 11% (17) cited the Lewinnek article correctly. Forty-five percent (66) of articles referenced measurements in the supine position, 18% (26) referenced other positions, and 37% (55) did not specify. Nineteen percent (28) reported measurements of the acetabular cup orthogonal to the anterior pelvic plane, while 73% (108) did not, and 7% (11) did not specify. Twenty-three percent (34) measured from computed tomography scans instead of other methods.

CONCLUSIONS

In the discussion of the safe zone regarding THA, only 11% of articles listed are consistent with the definition established by Lewinnek. This warrants further investigation into a consistent application of the term and its implications for THA implant stability and dislocation rates.

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.

Can some early revision total hip arthroplasties be avoided?

Aims

Studying the indications for revision total hip arthroplasty (THA) may enable surgeons to change their practice during the initial procedure, thereby reducing the need for revision surgery. The aim of this study was to identify and describe the potentially avoidable indications for revision THA within five years of the initial procedure.

Patients and Methods

A retrospective review of 117 patients (73 women, 44 men; mean age 61.5 years (27 to 88)) who met the inclusion criteria was conducted. Three adult reconstruction surgeons independently reviewed the radiographs and medical records, and they classified the revision THAs into two categories: potentially avoidable and unavoidable. Baseline demographics, perioperative details, and quality outcomes up to the last follow-up were recorded.

Results

A total of 60 revision THAs (51.3%) were deemed potentially avoidable and 57 (48.7%) were deemed unavoidable. The following were identified as avoidable factors: suboptimal positioning of the acetabular component (29; 48%), intraoperative fracture or a fracture missed on an intraoperative radiograph (20; 33%), early (less than two weeks) aseptic loosening (seven; 11.7%), and symptomatic leg length discrepancy of > 1 cm (four; 6.7%).

Conclusion

A surprisingly large proportion of acute revision THAs are potentially avoidable. Surgeons must carefully evaluate the indications for revision THAs in their practice and identify new methods to address these issues. Cite this article: Bone Joint J 2019;101-B(6 Supple B):97–103.

A new system of computer-assisted navigation leading to reduction in operating time in uncemented total hip replacement in a matched population

Computer-assisted navigation techniques are used to optimise component placement and alignment in total hip replacement. It has developed in the last 10 years but despite its advantages only 0.3% of all total hip replacements in England and Wales are done using computer navigation. One of the reasons for this is that computer-assisted technology increases operative time. A new method of pelvic registration has been developed without the need to register the anterior pelvic plane (BrainLab hip 6.0) which has shown to improve the accuracy of THR. The purpose of this study was to find out if the new method reduces the operating time. This was a retrospective analysis of comparing operating time in computer navigated primary uncemented total hip replacement using two methods of registration. Group 1 included 128 cases that were performed using BrainLab versions 2.1-5.1. This version relied on the acquisition of the anterior pelvic plane for registration. Group 2 included 128 cases that were performed using the newest navigation software, BrainLab hip 6.0 (registration possible with the patient in the lateral decubitus position). The operating time was 65.79 (40-98) minutes using the old method of registration and was 50.87 (33-74) minutes using the new method of registration. This difference was statistically significant. The body mass index (BMI) was comparable in both groups. The study supports the use of new method of registration in improving the operating time in computer navigated primary uncemented total hip replacements.

Improving registration accuracy during total hip arthroplasty: a cadaver study of a new, 3-D mini-optical navigation system

INTRODUCTION

Maintaining accuracy of component placement is an important step in ensuring the long-term stability of components during total hip arthroplasty (THA). Computer-assisted navigation has improved accuracy but errors associated with the registration process are known to impact the accuracy of final measurements. The purpose of this cadaver study was to determine the registration error associated with a novel mini-navigation system.

METHODS

3 board-certified orthopaedic surgeons performed 4 THA procedures each via the posterolateral approach on 6 cadavers (12 hips) using the mini-navigation tool. Pre- and post-operative radiographs and post-operative computed tomography (CT) images were obtained. Image analysis was performed by 2 radiologists not involved in the surgical procedures. During registration, surgeons aligned the alignment rod with the anterior pelvic plane (APP) to provide a reference plane for comparison with traditional navigation. Cup position from the device was compared with measurements gathered from post-op imaging.

RESULTS

The mean difference between CT and device measurements for inclination was -1.7° (standard deviation [SD] 4.9°), while the mean absolute difference was 4.2° (SD 3.2°). The mean difference between anteversion angles calculated from CT scans and from the device was -3.5° (SD 4.5°), with an absolute difference of 4.0° (SD 4.0°). 100% (12/12) of inclination measurements and 92% (11/12) of anteversion measurements fell within both the clinical and statistical limits of agreement when analyzed via the Bland-Altman technique.

CONCLUSIONS

This study demonstrates that the registration error associated with this new mini-navigation system compares favourably with the known registration error associated with traditional navigation systems.

Technology in Arthroplasty: Are We Improving Value?

PURPOSE OF REVIEW

Total joint arthroplasty is regarded as a highly successful procedure. Patient outcomes and implant longevity, however, are related to proper alignment and position of the prostehses. In an attempt to reduce outliers and improve accuracy and precision of component position, navigation and robotics have been introduced. These technologies, however, come at a price. The goals of this review are to evaluate these technologies in total joint arthroplasty and determine if they add value.

RECENT FINDINGS

Recent studies have demonstrated that navigation and robotics in total joint arthroplasty can decrease outliers while improving accuracy in component positioning. While some studies have demonstrated improved patient reported outcomes, not all studies have shown this to be true. Most studies cite increased cost of equipment and longer operating room times as the major downsides of the technologies at present. Long-term studies are just becoming available and are promising, as some studies have shown decreased revision rates when navigation is used. Finally, there are relatively few studies evaluating the direct cost and value of these technologies. Navigation and robotics have been shown to improve component position in total joint arthroplasty, which can improve patient outcomes and implant longevity. These technologies offer a promising future for total joint arthroplasty.

Revision Total Hip Arthroplasty Using Imageless Navigation With the Concept of Combined Anteversion

BACKGROUND

The purpose of the study was to evaluate the implant positions and clinical results of revision total hip arthroplasty (THA) using an imageless navigation with the concept of combined anteversion.

METHODS

A total of 40 cementless revision THAs (24 men and 16 women) using an imageless navigation with the concept of combined anteversion were retrospectively evaluated. The concept of combined anteversion was applied in cup positioning based on Widmer's equation (cup anteversion + 0.7 × stem anteversion). The mean follow-up period was 80.7 months. Postoperatively, the inclination of the cup was evaluated on standard anteroposterior view of the radiograph, and the anteversion of the cup and femoral stem was evaluated using computed tomography scan. A cup inclination of 40° ± 10° and combined anteversion of the cup and femoral stem of 37° ± 10° based on Widmer's equation were regarded as the "safe zone."

RESULTS

The average anteversion of the revised femoral stems was 15.3° ± 2.9° (range, 9.5°-21.5°), whereas that of the remained femoral stems was 17.4° ± 9.7° (range, 4.2°-29.8°). The inclination, anteversion of the cup, and combined anteversion after revision THA were 42.3° ± 3.1° (range, 32.1°-48.2°), 25.0° ± 2.9° (range, 16.9°-29.5°), and 36.1° ± 3.4° (range, 27.2°-42.9°), respectively. Therefore, the position of the implants, relative to the safe zone, showed no outliers after the revision surgery. Neither dislocation nor osteolysis was observed after the surgery.

CONCLUSION

Favorable results of this study indicate that imageless navigation helps the surgeon in placing the components of revision THA in the safe zone. This study also shows that when this safe zone is consistently obtained, then no postoperative dislocations were observed in these patients over the 6-year follow-up period.

The Evolution of Computer-Assisted Total Hip Arthroplasty and Relevant Applications

In total hip arthroplasty (THA), the accurate positioning of implants is the key to achieve a good clinical outcome. Computer-assisted orthopaedic surgery (CAOS) has been developed for more accurate positioning of implants during the THA. There are passive, semi-active, and active systems in CAOS for THA. Navigation is a passive system that only provides information and guidance to the surgeon. There are 3 types of navigation: imageless navigation, computed tomography (CT)-based navigation, and fluoroscopy-based navigation. In imageless navigation system, a new method of registration without the need to register the anterior pelvic plane was introduced. CT-based navigation can be efficiently used for pelvic plane reference, the functional pelvic plane in supine which adjusts anterior pelvic plane sagittal tilt for targeting the cup orientation. Robot-assisted system can be either active or semi-active. The active robotic system performs the preparation for implant positioning as programmed preoperatively. It has been used for only femoral implant cavity preparation. Recently, program for cup positioning was additionally developed. Alternatively, for ease of surgeon acceptance, semi-active robot systems are developed. It was initially applied only for cup positioning. However, with the development of enhanced femoral workflows, this system can now be used to position both cup and stem. Though there have been substantial advancements in computer-assisted THA, its use can still be controversial at present due to the steep learning curve, intraoperative technical issues, high cost and etc. However, in the future, CAOS will certainly enable the surgeon to operate more accurately and lead to improved outcomes in THA as the technology continues to evolve rapidly.