Imageless computer-assisted versus conventional total hip arthroplasty: one surgeon's initial experience

Fluoroscopy Versus Imageless Optical Navigation in Direct Anterior Approach Total Hip Arthroplasty

BACKGROUND

Utilization of the direct anterior approach (DAA) for total hip arthroplasty (THA) has risen in popularity. Accurate implant placement is a critical factor that influences patient outcomes. The goal of this study was to compare the accuracy and precision of fluoroscopy with imageless optical navigation in DAA THA.

METHODS

This was a cohort study of 640 consecutive primary DAA THAs performed with intraoperative fluoroscopy (n = 300 patients) or imageless optical navigation (n = 304 patients). Accuracy was compared by measuring acetabular cup inclination, anteversion, and leg-length discrepancy (LLD). The proportion of implants placed within the Lewinnek safe zone and those placed within a more precise target of 40 ± 5° inclination and 20 ± 5° anteversion was evaluated.

RESULTS

According to the Lewinnek criteria, there was no difference in the percentage of implants placed within both inclination and anteversion targets (fluoroscopy: 90.3%; navigation: 88.8%, P = 0.519). Using the more precise targets, navigation increased the implants positioned correctly for both inclination and anteversion (fluoroscopy: 50.3%; navigation: 65.6%, P < 0.001). Navigation increased the proportion of implants positioned within the target anteversion zone (fluoroscopy: 71.3%; navigation: 83.8%, P < 0.001) but not inclination (fluoroscopy: 71.9%; navigation: 76.9%, P = 0.147). The mean LLD was higher with the use of fluoroscopy compared with navigation (5.5 mm, standard deviation: 4.1; 4.6 mm, SD: 3.4, P < 0.005). No difference in dislocation rate was observed ( P = 0.643).

CONCLUSION

Both fluoroscopy and imageless optical navigation demonstrated accurate acetabular implant positioning during DAA THA. Navigation was more precise and associated with improved acetabular anteversion placement and restoration of LLD. Navigation is an accurate alternative to fluoroscopy with decreased radiation exposure.

Defining the Learning Period of a Novel Imageless Navigation System for Posterior Approach Total Hip Arthroplasty: Analysis of Surgical Time and Accuracy

Introduction

The use of imageless navigation in total hip arthroplasty (THA) is frequently associated with prolonged surgical times, predominantly during the learning period. The purpose of the present study was to characterize the learning period of a novel imageless navigation system, specifically as it related to surgical time and acetabular navigation accuracy.

Materials and Methods

This was a retrospective observational study of a consecutive group of 158 patients who underwent primary unilateral THA for osteoarthritis by a team headed by a single surgeon. All procedures used an imageless navigation system to measure acetabular cup inclination and anteversion angles, referencing a generic sagittal and frontal plane. Navigation accuracy was determined by assessing differences between intraoperative inclination and anteversion values and those obtained from standardized 6-week follow-up radiographs. Operative time and navigation accuracy were assessed by plotting moving averages of 7 consecutive cases. The learning period was defined using Mann-Kendall trend analyses, student t-tests and nonlinear regression modeling based on surgical time and navigation accuracy. Alpha error was 0.05.

Results

The average surgical time was 67.3 min (SD:9.2) (range 45-95). The average navigation accuracy for inclination was 0.01° (SD:4.2) (range - 10 to 10), and that for anteversion was - 4.9° (SD:3.8) (range - 14 to 5). Average surgical time and navigation accuracy were similar between the first and final cases in the series with no learning period detected.

Conclusions

There was no discernible learning period effect on surgical time or system measurement accuracy during the early phases of adoption for this imageless navigation system.

Achieving Precise Cup Positioning in Direct Anterior Total Hip Arthroplasty: A Narrative Review

Malpositioned implants in total hip arthroplasty are associated with impingement, increased wear, and dislocations, thus precise cup positioning is crucial. However, significant deviations between targeted and actually achieved cup positions have been found even in patients operated by experienced surgeons. When aiming for higher accuracy, various methods based on freehand positioning lead by anatomic landmarks, C-arm fluoroscopy, imageless navigation, or robotic-assisted-surgery have been described. There is a constant development of new products aiming to simplify and improve intraoperative guidance. Both the literature and expert opinions on this topic are often quite controversial. This article aims to give an overview of the different methods and systems with their specific advantages and potential pitfalls while also taking a look into the future of cup positioning in anterior hip replacements.

Utilizing Three-Dimensional Head-Lesser Trochanter Distance Could Further Reduce Leg Length Inequality in Primary Bipolar Hemiarthroplasty

Background: The aim of this study was to investigate whether the use of three-dimensional (3-D) computed tomography (CT)-based head-lesser trochanter distance (HLD) could reduce leg length discrepancy (LLD) more than the use of a two-dimensional (2-D) plain film method in primary bipolar hemiarthroplasty. Methods: Propensity score matching (PSM) analysis was used to adjust the confounding factors. A retrospective comparative analysis of 128 patients was performed. In the control group, the leg length was equalized using the 2-D, plain film-based HLD. In the study group, primary bipolar hemiarthroplasty was performed using the 3-D CT-based HLD method. Postoperative LLDs were compared between the two groups using the method of Ranawat. In addition, the Harris hip score (HHS) was evaluated and compared at one year after surgery. Results: A significant difference was observed in mean postoperative LLD between the 2-D HLD group and the 3-D CT HLD group: 1.6 ± 1.2 mm (range, 0.1−6.0 mm) and 1.1 ± 1.2 mm (range, 0.1−5.1 mm), respectively (p < 0.05). Additionally, a higher percentage of patients in the 3-D CT HLD group had an LLD of less than 2 mm. The mean HHS at one year after surgery showed no significant difference between the two groups. Conclusions: To minimize the occurrence of LLD, HLD measurement from a CT scanner may be more accurate than an X-ray. The 2-D and 3-D HLD differences in the 3-D CT HLD group were statistically significant. Using a 3-D, CT-based HLD method might decrease the possibility of an LLD over 2 mm.

Imageless navigation for primary total hip arthroplasty: a meta-analysis study

BACKGROUND

There has been a growing interest in imageless navigation for primary total hip arthroplasty (THA). Its superiority over standard THA is debated. This meta-analysis compared surgical duration, implant positioning, Harris Hip Score and rate of dislocation of imageless navigation versus conventional THA.

METHODS

The present study was conducted according to the PRISMA 2020 guidelines. All the clinical trials comparing imageless navigation versus conventional for primary THA were accessed. In January 2022, the following databases were accessed: PubMed, Web of Science, Google Scholar and Embase. No time constraints were used for the search. The outcomes of interest were to compare cup inclination and anteversion, leg length discrepancy, surgical duration, Harris Hip Score and rate of dislocation of imageless navigation versus conventional THA.

RESULTS

Twenty-one studies (2706 procedures) were retrieved. Fifty-two percent of patients were women. There was between-group comparability at baseline in terms of age, body mass index (BMI), visual analogue scale, Harris Hip Score and leg length discrepancy (P > 0.1). Compared with conventional THA, the navigated group demonstrated slightly lower leg length discrepancy (P = 0.02) but longer duration of the surgical procedure (P < 0.0001). Cup anteversion (P = 0.6) and inclination (P = 0.5), Harris Hip Score (P = 0.1) and rate of dislocation (P = 0.98) were similar between the two interventions.

CONCLUSION

Imageless navigation may represent a viable option for THA.

Effectiveness of an accelerometer-based portable navigation for intraoperative adjustment of leg length discrepancy in total hip arthroplasty in the supine position

BACKGROUND

This study aimed to examine the accuracy of the HipAlign® accelerometer-based portable navigation system by measuring the intraoperative leg length change of patients who underwent total hip arthroplasty (THA) and comparing the measured leg length discrepancy (LLD) determined by the navigation system and a freehand technique.

METHODS

A total of 61 patients who underwent THA using the anterolateral approach in the supine position were included in this study and divided into two groups: those who underwent THA with navigation (Group N; N = 31) and with the freehand technique (Group F; N = 30). Statistical analyses were performed to compare the intraoperative leg length change, pre- and post-LLD, absolute values of post-LLD, and the number of patients with the postoperative LLD within 10 mm and 5 mm between the two groups. Additionally, we examined the correlation between the leg length change obtained through intraoperative navigation and measured from the radiographs. Moreover, to evaluate the navigation accuracy, we examined the correlation between the absolute error of leg length change and cup orientation.

RESULTS

The postoperative LLD was significantly lower and the number of patients with the postoperative LLD within 5 mm was significantly higher in Group N, compared with Group F. Additionally, the amount of leg length change measured intraoperatively by the navigation system was strongly correlated with the values obtained by the postoperative radiographic measurement with a small absolute error and minimal wasted time. Moreover, a significant positive correlation was found between the absolute error of the leg length change and that of the cup inclination.

CONCLUSIONS

Our study demonstrates that the accelerometer-based portable navigation system is useful for the intraoperative adjustment of leg length discrepancy during THA for patients in the supine position, as it provides good accuracy and minimizes required time for use.

Utilization of technology-assisted total hip arthroplasty in the United States from 2005 to 2018

Background

Successful outcomes in total hip arthroplasty (THA) rely in part on accurate component positioning, which may be optimized through the use of computer navigation and robot-assistance. Therefore, we queried a large national database to characterize national trends in technology-assisted THA utilization, determine whether these technologies were associated with increased hospital charges, and identify demographic factors associated with technology-assisted THA.

Methods

Using the Nationwide Inpatient Sample database, patients that underwent conventional THA, computer-navigated THA, and robot-assisted THA from 2005 to 2018 were identified. Patient and hospital demographics, charge data, and payer characteristics were collected. Temporal trends in utilization were reported. Univariate analyses were performed to compare differences between groups with multiple logistic regression analysis to account for confounders.

Results

In total, 3,428,208 patients undergoing THA from 2005 to 2018 were identified, of which 63,136 (1.8%) used computer navigation and 32,660 (1.0%) used robot-assistance. National utilization of computer navigation in THA increased from 0.1% to 1.9% between 2005 and 2018, while utilization of robot-assisted THA increased from <0.1% to 2.1% from 2008 to 2018. On multivariate analysis, technology-assisted THA was most commonly performed in urban hospitals in the Northeastern United States. Median hospital charges were increased for technology-assisted THAs relative to conventional THAs ($66,089 ± $254 vs $55,418 ± $43).

Conclusions

Computer navigation and robot-assistance in THA demonstrated a consistent increase in utilization during the period examined, representing 4.0% of THAs performed in 2018. Patient and hospital characteristics including risk of mortality, geographic region, and teaching status were associated with increased utilization. Utilization of computer navigation was associated with increased hospital charges.

WITHDRAWN: Comparison of the accuracy between imageless navigation and manual freehand approaches for total hip arthroplasty: a systematic review and meta-analysis

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A review of computer-assisted orthopaedic surgery systems

BACKGROUND

Computer-assisted orthopaedic surgery systems have great potential, but no review has focused on computer-assisted surgery systems for the spine, hip, and knee.

METHODS

A systematic search was performed in Web of Science and PubMed. We searched the literature on computer-assisted orthopaedic surgery systems from 2008 to the present and focused on three aspects of systems: training, planning, and intraoperative navigation.

RESULTS AND DISCUSSION

In this review study, we reviewed 34 surgical training systems, 31 surgical planning systems, and 41 surgical navigation systems. The functions and characteristics of the surgical systems were compared and analysed, and the current concerns about and the impact of the surgical systems on doctors and surgery were clarified.

CONCLUSION

Computer-assisted orthopaedic surgery systems are still in the development stage. Future surgical training systems should include synthetic models with patient anatomy. Surgical planning systems with automatic planning should be developed, and surgical navigation systems with multimodal fusion, robotic assistance and imaging should be developed.

Total Hip Arthroplasty Using Imageless Computer-Assisted Navigation-2-Year Follow-Up of a Prospective Randomized Study

The purpose of this study is to compare computer-assisted to manual implantation-techniques in total hip arthroplasty (THA) and to find out if the computer-assisted surgery is able to improve the clinical and functional results and reduce the dislocation rate in short-terms after THA. We performed a concise minimum 2-year follow-up of the patient cohort of a prospective randomized study published in 2014 and evaluated if the higher implantation accuracy in the navigated group can be seen as an important determinant of success in total hip arthroplasty. Although a significant difference was found in mean postoperative acetabular component anteversion and in the outliers regarding inclination and anteversion (p < 0.05) between the computer-assisted and the manual-placed group, we could not find significant differences regarding clinical outcome or revision rates at 2-years follow-up. The implantation accuracy in the navigated group can be regarded as an important determinant of success in THA, although no significant differences in clinical outcome could be detected at short-term follow-up. Therefore, further long-term follow-up of our patient group is needed.

Trends and patient factors associated with technology-assisted total hip arthroplasty in the United States from 2005 to 2014

Background

Technology-assisted total hip arthroplasty (TA-THA) using either computer-assisted navigation or robotic assistance has become increasingly more popular. The purpose of this study was to examine the trends and patient factors associated with TA-THA.

Methods

This is a retrospective review utilizing the National Inpatient Sample, a large national database incorporating inpatient hospitalization information. International Classification of Diseases, 9th Revision codes were used to identify patients with hip osteoarthritis who underwent primary total hip arthroplasty (THA). Patients were then separated into those who underwent TA-THA or conventional THA. Outcomes of interest included annual TA-THA utilization; patient and hospital characteristics associated with TA-THA; and trends for length of stay (LOS), cost, and discharge to home.

Results

From 2005 to 2014, a total of 2,588,304 patients with hip osteoarthritis who underwent THA were identified in the National Inpatient Sample database. Of those, 39,700 (1.5%) underwent TA-THA. The number of TA-THA procedures increased from 178 (0.1% of all THA) in 2005 to 10,045 (3.0% of all THA) in 2014, which represented a 30-fold increase in incidence (P-trend <.0001). TA-THA was associated with Hispanic race, higher patient income, and the Western region of the United States. During the study period, there was a trend toward decreased LOS and increased discharge to home for both TA-THA and conventional THA. TA-THA was associated with higher inpatient cost.

Conclusion

TA-THA is being increasingly used in the United States and is associated with specific patient factors. However, the value of TA-THA compared to conventional THA remains unclear and should be assessed with future research.

Level of Evidence

III (retrospective cohort study).

Portable Accelerometer-Based Navigation System for Cup Placement of Total Hip Arthroplasty: A Prospective, Randomized, Controlled Study

BACKGROUND

Malposition of the acetabular component during total hip arthroplasty (THA) is associated with increased risk of dislocation, reduced range of motion, and accelerated wear. The purpose of this study is to compare cup positioning with a portable, accelerometer-based hip navigation system and conventional surgical technique.

METHODS

In a prospective, randomized, clinical study, cups were implanted with a portable, accelerometer-based hip navigation system (navigation group; n = 55) or conventional technique (conventional group; n = 55). THA was conducted in the lateral position and through posterior approach. The cup position was determined postoperatively on pelvic radiograph and computed tomography scans.

RESULTS

An average cup abduction of 39.2° ± 4.6° (range, 27° to 50°) and an average cup anteversion of 14.6° ± 6.1° (range, 1° to 27.5°) were found in the navigation group, and an average cup abduction of 42.9° ± 8.0° (range, 23° to 73°) and an average cup anteversion of 11.6° ± 7.7° (range, -12.1° to 25°) in the conventional group. A smaller variation in the navigation group was indicated for cup abduction (P = .001). The deviations from the target cup position were significantly lower in the navigation group (P = .001, .016). While only 37 of 55 cups in the conventional group were inside the Lewinnek safe zone, 51 of 55 cups in the navigation group were placed inside this safe zone (P = .006). The navigation procedure took a mean of 10 minutes longer than the conventional technique.

CONCLUSION

Use of the portable, accelerometer-based hip navigation system can improve cup positioning in THA.

Clinical efficacy of orthopilot navigation system versus conventional manual of total hip arthroplasty: A systematic review and meta-analysis

BACKGROUND

To compare the clinical efficacy between Orthopilot navigation system and conventional manual surgery in total hip arthroplasty (THA).

METHODS

Electronic databases were searched to identify randomized controlled trials (RCTs) investigating Orthopilot navigation system versus conventional manual in patients undergoing THA. Outcome measurements include anteversion angle, inclination angle, preoperative leg length discrepancy, postoperative leg length discrepancy and femoral offset. Statistical software Stata 12.0 was used for data-analysis.

RESULTS

A total of 5 studies were finally included in this meta-analysis. The results showed that the conventional manual group have a less anteversion angle than that in Orthopilot navigation system group (weighted mean difference (WMD) = 4.67, 95% confidence interval (CI) = 3.53, 5.82, P = .000). And pooled analysis showed that the inclination angle in Orthopilot navigation group was less than that in conventional manual group (WMD = -4.19, 95% CI = -8.00, -0.37, P = .031). There was no significant difference between the preoperative leg length discrepancy and postoperative leg length discrepancy (P > .05). Orthopilot navigation system compared with conventional manual procedure was associated with decreased of femoral offset by 2.76 (WMD = -2.76, 95%CI = -3.90, -1.62, P = .000).

CONCLUSION

Both Orthopilot navigation system and conventional THA result in significant improvements in patient function with similar overall complication rates and have their own edges in cup position.

Trends in computer navigation and robotic assistance for total knee arthroplasty in the United States: an analysis of patient and hospital factors

Background

Computer navigation and robotic assistance technologies are used to improve the accuracy of component positioning in total knee arthroplasty (TKA), with the goal of improving function and optimizing implant longevity. The purpose of this study was to analyze trends in the use of technology-assisted TKA, identify factors associated with the use of these technologies, and describe potential drivers of cost.

Methods

The Nationwide Inpatient Sample database was used to identify patients who underwent TKA using conventional instrumentation, computer navigation, and robot-assisted techniques between 2005 and 2014. Variables analyzed include patient demographics, hospital and payer types, and hospital charges. Descriptive statistics were used to describe trends. Univariate and multivariate analyses were performed to identify differences between conventional and technology-assisted groups.

Results

Our analysis identified 6,060,901 patients who underwent TKA from 2005 to 2014, of which 273,922 (4.5%) used computer navigation and 24,084 (0.4%) used robotic assistance. The proportion of technology-assisted TKAs steadily increased over the study period, from 1.2% in 2005 to 7.0% in 2014. Computer navigation increased in use from 1.2% in 2005 to 6.3% in 2014. Computer navigation was more likely to be used in the Western United States, whereas robot-assisted TKAs were more likely to be performed in the Northeast. Increased hospital charges were associated with the use of technology assistance ($53,740.1 vs $47,639.2).

Conclusions

The use of computer navigation and robot-assisted TKA steadily increased over the study period, accounting for 7.0% of TKAs performed in the United States in 2014. Marked regional differences in the use of these technologies were identified. The use of these technologies was associated with increased hospital charges.

Clinical efficacy of OrthoPilot navigation system versus conventional manual total hip arthroplasty: A systematic review and meta-analysis

Objective

This study was performed to compare the clinical efficacy between the OrthoPilot navigation system and conventional manual surgery in patients undergoing total hip arthroplasty.

Methods

The Embase, PubMed, CINAHL, and Cochrane databases were searched for clinical trials. The outcome measurements were the anteversion angle, inclination angle, and complications. Review Manager 5.3 statistical software was used for the data analysis.

Results

Significant differences were found in the femoral offset and overall complication rate between the conventional and navigation groups. Additionally, the conventional group had significantly less anteversion than the navigation group. However, the navigation group had significantly better inclination. The operation time was significantly shorter in the conventional than navigation group.

Conclusion

Both the OrthoPilot navigation system and conventional total hip arthroplasty result in significant improvements in patient function with similar overall complication rates and have their own advantages in achieving good cup position. The conventional procedure has a shorter operation time than does use of a navigation system.

Minimal Increase in Total Hip Arthroplasty Surgical Procedural Time with the Use of a Novel Surgical Navigation Tool

Background

Computer-assisted navigation has proven effective at improving the accuracy of component placement during Total Hip Arthroplasty (THA); however, the material costs, line-of-site issues and potential for significant time increases have limited their widespread use.

Objective

The purpose of this study was to investigate the impact of an imageless navigation device on surgical time, when compared with standard mechanical guides.

Methods

We retrospectively reviewed prospectively collected data from 61 consecutive primary unilateral THA cases (posterior approach) performed by a single surgeon. Procedural time (incision to closure) for THA performed with (intervention) or without (control) a computer-assisted navigation system was compared. In the intervention group, the additional time associated with the use of the device was recorded. Mean times were compared using independent samples t-tests with statistical significance set a priori at p<0.05.

Results

There was no statistically significant difference between procedural time in the intervention and control groups (102.3±28.3 mins vs. 99.1±14.7 mins, p=0.60). The installation and use of the navigation device accounted for an average of 2.9 mins (SD: 1.6) per procedure, of which device-related setup performed prior to skin incision accounted for 1.1 mins (SD: 1.1) and intra-operative tasks accounted for 1.6 mins (SD: 1.2).

Conclusion

In this series of 61 consecutive THAs performed by a single surgeon, the set-up and hands-on utilization of a novel surgical navigation tool required an additional 2.9 minutes per case. We suggest that the intraoperative benefits of this novel computer-assisted navigation platform outweigh the minimal operative time spent using this technology.

Leg length correction in computer assisted primary total hip arthroplasty: A collective review of the literature

AIM

The aim of this study was to determine whether computer assisted surgery (CAS) can provide a more accurate, reproducible technique to achieve equal leg lengths in total hip arthroplasty (THA) and to compare the clinical outcome with conventional on table judgement of leg lengths in unilateral total hip replacement.

METHODS

A collective review of the literature was undertaken utilizing applicable databases. Research criteria were the following: (1) Developing and developed country studies, (2) level II, III, IV and V studies, (3) human subjects only, (4) period of study from 1996 to 2017 - English text only. The identified publications were assessed for their relevance and methodology and 20 articles were selected.

RESULTS

The overall evaluation of the results demonstrates that CAS provides a more accurate reproduction of limb length in THA compared to conventional freehand THA. Short to medium-term studies have demonstrated no benefit in clinical outcome scores. There is a high degree of correlation between measurements provided by CAS intraoperatively and radiographic measurements postoperatively.

CONCLUSION

CAS provides a more accurate, reproducible technique to achieve limb length equality in THA compared to conventional freehand THA, however more intensive long-term studies are required to establish the effect on implant longevity and revision surgery rates in the two groups.

A new mini-navigation tool allows accurate component placement during anterior total hip arthroplasty

Introduction

Computer-assisted navigation systems have been explored in total hip arthroplasty (THA) to improve component positioning. While these systems traditionally rely on anterior pelvic plane registration, variances in soft tissue thickness overlying anatomical landmarks can lead to registration error, and the supine coronal plane has instead been proposed. The purpose of this study was to evaluate the accuracy of a novel navigation tool, using registration of the anterior pelvic plane or supine coronal plane during simulated anterior THA.

Methods

Measurements regarding the acetabular component position, and changes in leg length and offset were recorded. Benchtop phantoms and target measurement values commonly seen in surgery were used for analysis. Measurements for anteversion and inclination, and changes in leg length and offset were recorded by the navigation tool and compared with the known target value of the simulation. Pearson's r assessed the relationship between the measurements of the device and the known target values.

Results

The device accurately measured cup position and leg length measurements to within 1° and 1 mm of the known target values, respectively. Across all simulations, there was a strong, positive relationship between values obtained by the device and the known target values (r=0.99).

Conclusion

The preliminary findings of this study suggest that the novel navigation tool tested is a potentially viable tool to improve the accuracy of component placement during THA using the anterior approach.

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.

Identifying the procedural gap and improved methods for maintaining accuracy during total hip arthroplasty

Osteoarthritis is a ubiquitous condition, affecting 26 million Americans each year, with up to 17% of adults over age 75 suffering from one variation of arthritis. The hip is one of the most commonly affected joints and while there are conservative options for treatment, as symptoms progress, many patients eventually turn to surgery to manage their pain and dysfunction. Early surgical options such as osteotomy or arthroscopy are reserved for younger, more active patients with less severe disease and symptoms. Total hip arthroplasty offers a viable solution for patients with severe degenerative changes; however, post-surgical discrepancies in leg length, offset and component malposition are common and cause significant complications. Such discrepancies are associated with consequences such as low back pain, neurological deficits, instability and overall patient dissatisfaction. Current methods for managing leg length and offset during hip arthroplasty are either inaccurate and susceptible to error or are cumbersome, expensive and lengthen surgical time. There is currently no viable option that provides accurate, real-time data to surgeons regarding leg length, offset and cup position in a cost-effective manner. As such, we hypothesize that a procedural gap exists in hip arthroplasty, a gap into which fall a large majority of arthroplasty patients who are at increased risk of complications following surgery. These complications and associated treatments place significant stress on the healthcare system. The costs associated with addressing leg length and offset discrepancies can be minor, requiring only heel lifts and short-term rehabilitation, but can also be substantial, with revision hip arthroplasty costs of up to $54,000 per procedure. The need for a cost-effective, simple to use and unobtrusive technology to address this procedural gap in hip arthroplasty and improve patient outcomes is of increasing importance. Given the aging of the population, the projected increases in the volume of procedures over the coming decades and the economic pressures associated with downward pricing pressure and bundled payments, the need to address this gap is underscored.

A Kirschner wire as a transverse-axis guide to improve acetabular cup positioning

PURPOSE

To compare cup-positioning accuracy in total hip arthroplasty (THA) with or without use of a Kirschner wire as a transverse-axis guide for pelvic alignment.

METHODS

Records of 18 men and 73 women (mean age, 60 years) who underwent primary THA with (n=49) or without (n=42) use of a Kirschner wire as a transverse-axis guide for pelvic alignment were reviewed. A 2.4-mm Kirschner wire as a transversea-xis guide was inserted to the anterior superior iliac spine and was parallel to a line linking the left and right anterior superior iliac spine. The safe zone for cup positioning was defined as 30º to 50° abduction and 10º to 30º anteversion. Of the 5 operative surgeons, 2 were classified as experienced (total surgical volume >300) and 3 as inexperienced (total surgical volume of <50). The proportion of patients with the cup in the safe zone was compared in patients with or without use of the transverse-axis guide and in experienced and inexperienced surgeons.

RESULTS

For inexperienced surgeons, the use of the transverse-axis guide significantly improved the proportion of patients with the cup in the safe zone from 90% to 100% for abduction, from 50% to 82.4% for anteversion, and from 40% to 82.4% for both. Patients with the cup inside or outside the safe zone were comparable in terms of body height, weight, BMI, subcutaneous fat thickness, incision length, and acetabular cup size.

CONCLUSION

The use of the transverse-axis guide improved the accuracy of cup positioning by inexperienced surgeons.

Can computer-assisted surgery help restore leg length and offset during THA? A continuous series of 321 cases

INTRODUCTION

Total hip arthroplasty (THA) can bring about complications - particularly leg length differences - that are becoming increasingly litigious. Computer-assisted orthopedic surgery (CAOS) can help optimize the procedure, but its ability to effectively restore leg length is controversial. As a consequence, we carried out a study to determine: (1) its contribution to meeting leg length and offset objectives, (2) its reliability, by evaluating the correlation between radiological and navigation data, (3) its safety, by evaluating navigation-specific and non-specific complications.

HYPOTHESIS

CAOS will help to restore leg length within ± 5 mm in more than 80% of cases.

MATERIAL AND METHODS

A series of 321 continuous cases of cementless THA implanted through the posterolateral approach using CAOS was analyzed retrospectively. With a minimum 1 year follow-up, we evaluated whether the leg length and offset goals were achieved, how well the navigation and radiology data were correlated and whether navigation-specific and non-specific complications occurred. Based on our hypothesis that 80% of patients would have less than 5 mm leg length difference and the null hypothesis (PA = P0) with an alpha of 0.05, 200 observations were required to achieve a power of 90%.

RESULTS

The leg length and offset objectives were achieved in 83.3% and 88% of cases, respectively. Twenty-two patients required a heel wedge to compensate for leg length differences. The correlation between the radiology and surgical navigation data was satisfactory - the Pearson coefficient was 0.79 for length and 0.74 for offset. Intraoperative and postoperative complications or adverse events were found in 14.6% of cases; these were specific to CAOS in 12.1% of cases and non-specific in 2.5% of cases.

CONCLUSION

This study shows the relevance of CAOS for achieving preoperative leg length objectives, with good correlation between navigation and radiology data, and without major complications.

LEVEL OF EVIDENCE

IV - retrospective study.

Comparison of the reliability of leg length and offset data generated by three hip replacement CAOS systems using EOS™ imaging

INTRODUCTION

Computer-assisted orthopaedic surgery (CAOS) theoretically will help to optimise total hip arthroplasty (THA) results. Although CAOS systems have become more sophisticated, they are not widely used, partially because of their suspect reliability. To assess reliability of these systems, we carried out a study with multiple objectives in mind: (1) establish and compare the accuracy of the leg length (LL) measurement from three CAOS systems; (2) analyse the correlation of LL and offset data generated by these CAOS systems with those of the EOS™ imaging system; (3) determine if the goals of leg length restoration with ±2 and ±5 mm were achieved; (4) evaluate why certain cases fails.

HYPOTHESIS

The three CAOS systems have the same accuracy for LL, and their error is less than or equal to 0.6mm.

MATERIAL AND METHODS

We retrospectively studied 106 cases of primary THA where preoperative and postoperative measures of leg length had been performed with an EOS™ imaging system. The cases were placed in three groups, depending on which CAOS system had been used: group A (Amplivision™, amplitude), group B (Hip Express™, Brainlab), group P (THS™, Praxim). The accuracy of the leg length data was calculated by finding the difference between the data from each CAOS system and the gold-standard EOS measurements.

RESULTS

The leg length accuracy was -0.846 [-5 to 9], -0.675 [-9 to 18] and 0.542 mm [-5 to 13], respectively for groups A, B and P. The accuracy was significantly lower in group A than B (P=0.044) and group P (P=0.038). The Pearson correlation coefficient for CAOS and EOS measurements was 0.189, 0.701 and 0.891 for leg length and 0.668, 0.202 and 0.680 for offset, for groups A, B and P, respectively. No difference between groups were observed relative to the leg length objectives being achieved within ±2 mm (P=0.61) and ±5 mm (P=0.314). There were no differences in terms of the number of CAOS failures: three in group A, one in group B and three in group P (P=0.06).

CONCLUSION

The Praxim™ and Brainlab™ CAOS systems had similar accuracy for leg length measurements, and both were better than the Amplitude™ system. Only the Praxim™ had an error of less than 0.6mm. All the CAOS systems had values less than 1mm, which is considered excellent.

LEVEL OF EVIDENCE

Level IV, retrospective study.

No difference in clinical outcome, bone density and polyethylene wear 5-7 years after standard navigated vs. conventional cementfree total hip arthroplasty

INTRODUCTION

The purpose of this investigation was to compare clinical outcome, component loosening, polyethylene cup wear and periprosthetic bone mineral density between "cup first" navigated and conventional cementless total hip arthroplasty (THA) 5-7 years after surgery.

MATERIALS AND METHODS

Fifty patients who received THA with (n = 25) or without (n = 25) the use of an image-free navigation system by a single surgeon were investigated after a mean follow-up of 6.4 (4.8-7.4) years. The Hip Osteoarthritis Outcome Score (HOOS) and the Harris Hip Score (HHS) were obtained; range-of-motion (ROM) was evaluated by a blinded examiner. Radiographic cup inclination, signs of radiographic loosening and polyethylene wear were analysed with the help of digital analysis software on anterio-posterior radiographs by a blinded examiner. Acetabular and femoral periprosthetic bone density was evaluated with the help of dual-energy X-ray absorptiometry.

RESULTS

We were unable to find any statistical significant or clinically relevant difference for the HOOS, HHS, ROM and polyethylene wear between the navigated and the conventional THA group 5-7 years after surgery. Cup inclination was more precise in the navigated THA group in relation to the target value of 45°.

CONCLUSIONS

Standard "cup first" THA navigation does not improve mid-term functional outcome, bony ingrowth and/or polyethylene wear. New concepts in computer-assisted THA, considering cup and stem as coupled biomechanical partners are needed to justify the effort of navigation in routine operations.