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

Robotic-assisted total hip arthroplasty utilizing a fluoroscopy-guided system produced similar cup accuracy and precision relative to a computerized tomography-based robotic platform

Robotic assistance for total hip arthroplasty (THA) has been demonstrated to improve accuracy of acetabular cup placement relative to manual, unassisted technique. The purpose of this investigation was to compare the accuracy and precision between a fluoroscopy-based robotic total hip arthroplasty platform (FL-RTHA) and a computerized tomography-based (CT-RTHA) platform. The study included 98 consecutive FL-RTHA and 159 CT-RTHA procedures performed via direct anterior approach (DAA). All cases were performed for a pre-operative diagnosis of osteoarthritis, avascular necrosis, or rheumatoid arthritis. Primary outcome variables included cup implantation accuracy and precision (variance). Implantation accuracy was calculated as the absolute value of the difference between pre-operative target cup angles (inclination and anteversion) and the same post-operative angles. Percentage placement in the Lewinnek safe zone was also measured for both cohorts. The FL-RTHA and CT-RTHA cohorts demonstrated a 1.2° difference in absolute values for cup inclination accuracy (4.6° ± 3.6 vs. 3.4 ± 2.7; p = 0.005), and no difference in absolute values for cup anteversion accuracy (4.7° ± 4.1 vs. 4.6 ± 3.4; p = 0.991). Cohorts demonstrated similar precision for cup inclination and anteversion placement parameters, as well as equivalent Lewinnek safe zone placement. The use of a fluoroscopy-based robotic assistance platform for primary DAA THA resulted in similar accuracy and precision of acetabular cup placement when compared to a CT-based robotic assistance system.

Improved short-term outcomes for a novel, fluoroscopy-based robotic-assisted total hip arthroplasty system compared to manual technique with fluoroscopic assistance

BACKGROUND

While robotic-assisted total hip arthroplasty (RA-THA) has been associated with improved accuracy of component placement, the perioperative and early postoperative outcomes of fluoroscopy-based RA-THA systems have yet to be elucidated.

METHODS

This retrospective cohort analysis included a consecutive series of patients who received manual, fluoroscopy-assisted THA (mTHA) and fluoroscopy-based RA-THA at a single institution. We compared rates of complications within 90 days of surgery, length of hospital stay (LOS), and visual analog scale (VAS) pain scores.

RESULTS

No differences existed between groups with respect to demographic data or perioperative recovery protocols. The RA-THA cohort had a significantly greater proportion of outpatient surgeries compared to the mTHA cohort (37.4% vs. 3.8%; p < 0.001) and significantly lower LOS (26.0 vs. 39.5 h; p < 0.001). The RA-THA cohort had a smaller 90-day postoperative complication rate compared to the mTHA cohort (0.9% vs. 6.7%; p = 0.029). The RA-THA cohort had significantly lower patient-reported VAS pain scores at 2-week follow-up visits (2.5 vs. 3.3; p = 0.048), but no difference was seen after 6-week follow visits (2.5 vs. 2.8; p = 0.468).

CONCLUSION

Fluoroscopy-based RA-THA demonstrates low rates of postoperative complications, improved postoperative pain profiles, and shortened LOS when compared to manual, fluoroscopy-assisted THA.

The quest for optimal femoral torsion angle measurements: a comparative advanced 3D study defining the femoral neck axis

PURPOSE

There is high variability in femoral torsion, measured on two-dimensional (2D) computed tomography (CT) scans. The aim of this study was to find a reliable three-dimensional (3D) femoral torsion measurement method, assess the influence of CAM deformity on femoral torsion measurement, and to promote awareness for the used measurement method.

METHODS

3D models of 102 dry femur specimens were divided into a CAM and non-CAM group. Femoral torsion was measured by one 2D-CT method described by Murphy et al. (method 0) and five 3D methods. The 3D methods differed in strategies to define the femoral neck axis. Method 1 is based on an elliptical least-square fit at the middle of the femoral neck. Methods 2 and 3 defined the centre of mass of the entire femoral neck and of the most cylindrical part, respectively. Methods 4 and 5 were based on the intersection of the femoral neck with a 25% and 40% enlarged best fit sphere of the femoral head.

RESULTS

3D methods resulted in higher femoral torsion measures than the 2D method; the mean torsion for method 0 was 8.12° ± 7.30°, compared to 9.93° ± 8.24° (p < 0.001), 13.21° ± 8.60° (p < 0.001), 8.21° ± 7.64° (p = 1.00), 9.53° ± 7.87° (p < 0.001) and 10.46° ± 7.83° (p < 0.001) for methods 1 to 5 respectively. In the presence of a CAM, torsion measured with method 4 is consistently smaller than measured with method 5.

CONCLUSION

2D measurement might underestimate true femoral torsion and there is a difference up to 5°. There is a tendency for a higher mean torsion in hips with a CAM deformity. Methods 4 and 5 are the most robust techniques. However, method 4 might underestimate femoral torsion if a CAM deformity is present. Since method 5 is independent of a CAM deformity, it is the preferred technique to define expected values of torsion.

A review of robotic-assisted total hip arthroplasty

Total hip arthroplasty (THA) is a successful surgical method for hip replacement but still poses challenges and risks. Robotic-assisted THA (rTHA) using new generation robotic systems has emerged to improve surgical precision and outcomes. The purpose of this paper is to review the literature on rTHA, with a focus on its advantages, such as individualized preoperative planning, intraoperative assistance, and improved accuracy in implantation, especially in complex cases. Additionally, it aims to explore the disadvantages associated with the use of rTHA, including high costs, the learning curve, and prolonged operation time compared to manual THA (mTHA), which are critical drawbacks that require careful consideration and efforts for minimization. Some financial analyses suggest that rTHA may offer cost-effectiveness and reduced postoperative costs compared to mTHA. While technological advancements are expected to reduce technical complications, there are still debates surrounding long-term outcomes. Practical limitations, such as limited availability and accessibility, also warrant attention. Although the development of rTHA shows promise, it is still in its early stages, necessitating critical evaluation and further research to ensure optimal patient benefits.

Readmission rate and healthcare utilization outcomes of computer-assisted fluoroscopy-based hip navigation versus manual total hip arthroplasty

INTRODUCTION

The study evaluates the technology of fluoroscopy-based hip navigation that has shown to improve implant positioning in total hip arthroplasty (THA).

METHODS

Premier Healthcare data for patients undergoing manual THA or fluoroscopy-based hip navigation THA between 1 January 2016-30 September 2021, were analyzed 90- and 365-day post-THA. The primary outcome was inpatient readmission. Secondary outcomes were operating room (OR) time, length of stay, discharge status, and hospital costs. Baseline covariate differences were balanced using fine stratification and analyzed using generalized linear models.

RESULTS

Among 4,080 fluoroscopy-based hip navigation THA and 429,533 manual THA balanced patients, hip-related readmission rates were statistically significantly lower for the fluoroscopy-based hip navigation THA cohort vs. manual THA for both 90-day (odd ratio [95% CI]: 0.69 [0.52 to 0.91] and 365-day (0.63 [0.49 to 0.81] follow-up. OR time was higher with fluoroscopy-based hip navigation THA vs. manual THA (134.65 vs. 132.04 minutes); however, fluoroscopy-based hip navigation THA patients were more likely to be discharged to home (93.73% vs. 90.11%) vs. manual THA. Hospital costs were not different between cohorts at 90- and 365-day post-operative.

CONCLUSIONS

Fluoroscopy-based hip navigation THA resulted in fewer readmissions, greater discharge to home, and similar hospital costs compared to manual THA.

Is It Necessary to Obtain Lateral Pelvic Radiographs in Flexed Seated Position for Preoperative Total Hip Arthroplasty Planning?

Background

Many of the current total hip arthroplasty (THA) planning tools only consider sagittal pelvic tilt in the standing and relaxed sitting positions. Considering that the risk of postoperative dislocation is higher when bending forward or in sit-to-stand move, sagittal pelvic tilt in the flexed seated position may be more relevant for preoperative planning. We hypothesized that there was a significant difference in sagittal pelvic tilt between the relaxed sitting and flexed seated positions as measured by the sacral slope in preoperative and postoperative full-body radiographs.

Methods

This was a multicenter retrospective analysis of the preoperative and postoperative simultaneous biplanar full-body radiographs of 93 primary THA patients in standing, relaxed sitting, and flexed seated positions. The sagittal pelvic tilt was measured using the sacral slope relative to the horizontal line.

Results

The mean difference between the preoperative sacral slope in the relaxed sitting position and the flexed seated position was 11.3° (-13° to 43°) (P < .0001). This difference was >10° in 52 patients (56%) and >20° in 18 patients (19.4%). The mean difference between the postoperative sacral slope in a relaxed sitting position and the sacral slope in a flexed seated position was 11.3° (P < .0001). This difference was >10° in 51 patients (54.9%) and >30° in 14 patients (15.1%) postoperatively.

Conclusions

There was a significant difference in sagittal pelvic tilt between the relaxed and flexed seated positions. A flexed seated view provides valuable information that might be more relevant for preoperative THA planning in order to prevent postoperative THA instability.

The learning curve for a novel, fluoroscopy-based robotic-assisted total hip arthroplasty system

BACKGROUND

Adoption of robotic-assisted total hip arthroplasty (RA-THA) systems can improve the accuracy of acetabular cup placement, but no group has reported the learning curve of novel, fluoroscopy-based RA-THA systems.

METHODS

A learning-curve cumulative summation (LC-CUSUM) analysis was performed on a consecutive series of the first 100 patients who received fluoroscopy-based RA-THA by the study surgeon. Operative times and specific robotic timepoints were compared between learning and proficiency phases.

RESULTS

Implementation of fluoroscopy-based RA-THA was associated with a learning curve of 12 cases. A 6-min increase in operative time was seen during the learning phase compared to the proficiency phase (44.3 ± 4.4 vs. 38.0 ± 7.1 min; p < 0.001), with a 3-min longer robotic cup impaction sequence during the learning phase (7.8 ± 1.9 vs. 4.8 ± 1.3 min; p < 0.001).

CONCLUSION

Adoption of fluoroscopy-based RA-THA is associated with a brief learning curve of 12 cases, with the most significant improvements in surgical efficiency realised during acetabular cup placement.

Design of Proposed Software System for Prediction of Iliosacral Screw Placement for Iliosacral Joint Injuries Based on X-ray and CT Images

One of the crucial tasks for the planning of surgery of the iliosacral joint is placing an iliosacral screw with the goal of fixing broken parts of the pelvis. Tracking of proper screw trajectory is usually done in the preoperative phase by the acquisition of X-ray images under different angles, which guide the surgeons to perform surgery. This approach is standardly complicated due to the investigation of 2D X-ray images not showing spatial perspective. Therefore, in this pilot study, we propose complex software tools which are aimed at making a simulation model of reconstructed CT (DDR) images with a virtual iliosacral screw to guide the surgery process. This pilot study presents the testing for two clinical cases to reveal the initial performance and usability of this software in clinical conditions. This model is consequently used for a multiregional registration with reference intraoperative X-ray images to select the slide from the 3D dataset which best fits with reference X-ray. The proposed software solution utilizes input CT slices of the pelvis area to create a segmentation model of individual bone components. Consequently, a model of an iliosacral screw is inserted into this model. In the next step, we propose the software CT2DDR which makes DDR projections with the iliosacral screw. In the last step, we propose a multimodal registration procedure, which performs registration of a selected number of slices with reference X-ray, and based on the Structural Similarity Index (SSIM) and index of correlation, the procedure finds the best match of DDR with X-ray images. In this pilot study, we also provide a comparative analysis of the computational costs of the multimodal registration upon various numbers of DDR slices to show the complex software performance. The proposed complex model has versatile usage for modeling and surgery planning of the pelvis area in fractures of iliosacral joints.

Functional Alignment Philosophy in Total Knee Arthroplasty – Rationale and technique for the varus morphotype using a CT based robotic platform and individualized planning

Introduction: Alignment techniques in total knee arthroplasty (TKA) continue to evolve. Functional alignment (FA) is a novel technique that utilizes robotic tools to deliver TKA with the aim of respecting individual anatomical variations. The purpose of this paper is to describe the rationale and technique of FA in the varus morphotype with the use of a robotic platform. Rationale: FA reproduces constitutional knee anatomy within quantifiable target ranges. The principles are founded on a comprehensive assessment and understanding of individual anatomical variations with the aim of delivering personalized TKA. The principles are functional pre-operative planning, reconstitution of native coronal alignment, restoration of dynamic sagittal alignment within 5° of neutral, maintenance of joint-line-obliquity and height, implant sizing to match anatomy and a joint that is balanced in flexion and extension through manipulation of implant positioning rather than soft tissue releases. Technique: An individualized plan is created from pre-operative imaging. Next, a reproducible and quantifiable method of soft tissue laxity assessment is performed in extension and flexion that accounts for individual variation in soft tissue laxity. A dynamic virtual 3D model of the joint and implant position that can be manipulated in all three planes is modified to achieve target gap measurements while maintaining the joint line phenotype and a final limb position within a defined coronal and sagittal range. Conclusion: Functional alignment is a novel knee arthroplasty technique that aims to restore constitutional bony alignment and balance the laxity of the soft tissues by placing and sizing implants in a manner that it respects the variations in individual anatomy. This paper presents the approach for the varus morphotype.

Improving Acetabular Component Positioning in Supine Direct Anterior Total Hip Arthroplasty with a Transparency Template: A Novel, Simple, and Cost-effective Technique

Purpose

A novel and simple method to ensure accurate acetabular component anteversion and inclination intraoperatively with the use of a transparency template is described.

Materials and Methods

Patients who underwent total hip arthroplasty (THA) via direct anterior approach (DAA) from June 2019 to January 2020 were included. A transparency template that can be placed over the image intensifier monitor to allow surgeons an accurate reading of the acetabular component position intraoperatively was designed, developed and utilized to determine effectiveness. The first template consists of two perpendicular lines indicating the “trans-ischial line” and the “pubic symphysis/coccyx”. The second template consist of a line indicating 45° inclination and parallel lines of corresponding distances apart required to achieve 20° anteversion based on Lewinnek's formula: version=sin^-1 (D1/D2), where D1: minor axis and D2: major axis of the component. This template was used throughout the acetabular part of the surgery, from reaming to impaction of component. Postoperative acetabular inclination, anteversion, surgical duration, length of stay, as well as complications were recorded.

Results

Twenty-six patients were included in this study. Mean postoperative acetabular cup inclination was 43.46±3.09° and mean version was 19.98±2.89°. A total of 21 patients (80.8%) fell within the Callanan safe zone and all 26 patients (100%) were within the Lewinnek safe zone.

Conclusion

The transparency template is a simple, reproducible, and effective tool with a minimal learning curve and no requirement for expensive equipment. This template has the potential to assist surgeons, especially those who are less experienced with DAA THA, in obtaining better postoperative radiographic outcomes.

Can robotic technology mitigate the learning curve of total hip arthroplasty?

Aims

Traditionally, acetabular component insertion during total hip arthroplasty (THA) is visually assisted in the posterior approach and fluoroscopically assisted in the anterior approach. The present study examined the accuracy of a new surgeon during anterior (NSA) and posterior (NSP) THA using robotic arm-assisted technology compared to two experienced surgeons using traditional methods.

Methods

Prospectively collected data was reviewed for 120 patients at two institutions. Data were collected on the first 30 anterior approach and the first 30 posterior approach surgeries performed by a newly graduated arthroplasty surgeon (all using robotic arm-assisted technology) and was compared to standard THA by an experienced anterior (SSA) and posterior surgeon (SSP). Acetabular component inclination, version, and leg length were calculated postoperatively and differences calculated based on postoperative film measurement.

Results

Demographic data were similar between groups with the exception of BMI being lower in the NSA group (27.98 vs 25.2; p = 0.005). Operating time and total time in operating room (TTOR) was lower in the SSA (p < 0.001) and TTOR was higher in the NSP group (p = 0.014). Planned versus postoperative leg length discrepancy were similar among both anterior and posterior surgeries (p > 0.104). Planned versus postoperative abduction and anteversion were similar among the NSA and SSA (p > 0.425), whereas planned versus postoperative abduction and anteversion were lower in the NSP (p < 0.001). Outliers > 10 mm from planned leg length were present in one case of the SSP and NSP, with none in the anterior groups. There were no outliers > 10° in anterior or posterior for abduction in all surgeons. The SSP had six outliers > 10° in anteversion while the NSP had none (p = 0.004); the SSA had no outliers for anteversion while the NSA had one (p = 0.500).

Conclusion

Robotic arm-assisted technology allowed a newly trained surgeon to produce similarly accurate results and outcomes as experienced surgeons in anterior and posterior hip arthroplasty.

Cite this article: Bone Jt Open 2021;2(6):365–370.

Variability of pelvic axial rotation in patients undergoing total hip arthroplasty

BACKGROUND

Pelvic axial rotation affects the functional orientation of an acetabular component. Every 1° of axial rotation changes functional acetabular anteversion by 1°. There is limited information on pelvic rotation in THA patients, since it is difficult to measure on routine radiographs. Therefore, we used spine-to-ankle biplanar radiography to investigate variability in pelvic rotation in patients before and after THA.

METHODS

In 156 patients undergoing primary unilateral THA, we measured preoperative, 6 weeks and 1 year postoperative pelvic rotation in both standing and sitting positions using a biplanar radiography system. Patients with fixed pelvic rotation had a similar magnitude and direction of pelvic rotation in all standing or sitting images. We further identified patients with position-independent or position-dependent fixed pelvic rotation.

RESULTS

Pelvic rotation was common in THA patients, with 82 patients (53% of 156 patients) having at least 1 image with > 7° of rotational deformity. 12 patients (8% of 156 patients) had fixed rotation, 6 patients (4%) had position-independent fixed axial rotation and 6 patients (4%) had position-dependent fixed axial rotation.

CONCLUSIONS

It may be important to recognise whether a THA patient has a fixed pelvic axial rotational deformity, where 1 hip is consistently forward or backward in functional imaging. Fixed rotation will increase or decrease the functional anteversion of an acetabular component depending on THA side. Further research might better characterise associations and predictors of fixed axial rotation and its impact on patient outcomes after THA.

A review of the evolution of robotic-assisted total hip arthroplasty

INTRODUCTION

Total hip arthroplasty (THA) is currently a very successful operation but continues to evolve as we try to perfect techniques and improve outcomes for our patients. Robotic hip surgery (RHS) began with the 'active' ROBODOC system in the 1980s. There were drawbacks associated with the original ROBODOC and most recently, the MAKO robot was introduced with early promising results.

AIM

The aim of this paper is to provide an up-to-date review surrounding this area and discuss the pros and cons of this technique.

METHODS

A literature review searching Medline, Embase, Ovidsp, Cochrane library, pubmed database and google scholar was performed searching keywords including: 'Robotic hip surgery', 'Robotic orthopaedic surgery', 'Computer assisted hip surgery', 'robotic arthroplasty', and 'computer assisted orthopaedic surgery'.

CONCLUSION

Robotic hip surgery aims to tackle the limitations of the human factor in surgery by promising reproducible and reliable methods of component positioning in arthroplasty surgery. However, as orthopaedic surgeons, we must critically appraise all new technology and support the use providing there is sound robust evidence backing it.