Imageless Navigation System Research Articles

Evaluating Alternative Registration Planes in Imageless, Computer-Assisted Navigation Systems for Direct Anterior Total Hip Arthroplasty.

(1) Background: Imageless computer navigation systems have the potential to improve the accuracy of acetabular cup position in total hip arthroplasty (THA). Popular imageless navigation methods include locating the patient in a three-dimensional space (registration method) while using a baseline to angle the acetabular cup (reference plane). This study aims to compare the accuracy of different methods for determining postoperative acetabular cup positioning in THA via the direct anterior approach. (2) Methods: Fifty-one participants were recruited. Optical and inertial sensor imageless navigation systems were used simultaneously with three combinations of registration methods and reference planes: the anterior pelvic plane (APP), the anterior superior iliac spine (ASIS) and the table tilt (TT) method. Postoperative acetabular cup position, inclination, and anteversion were assessed using CT scans. (3) Results: For inclination, the mean absolute error (MAE) was lower using the TT method (2.4° ± 1.7°) compared to the ASIS (2.8° ± 1.7°, p = 0.17) and APP method (3.7° ± 2.1°, p < 0.001). For anteversion, the MAE was significantly lower for the TT method (2.4° ± 1.8°) in contrast to the ASIS (3.9° ± 3.2°, p = 0.005) and APP method (9.1° ± 6.2°, p < 0.001). (4) Conclusion: A functional reference plane is superior to an anatomic reference plane to accurately measure intraoperative acetabular cup inclination and anteversion in THA using inertial imageless navigation systems.

A novel imageless accelerometer-based navigation system improves acetabular cup placement accuracy during total hip arthroplasty in the lateral decubitus position.

The accuracy of acetabular cup placement using conventional portable imageless navigation systems in total hip arthroplasty (THA) in the lateral decubitus position remains challenging. Several novel portable imageless navigation systems have been developed recently to improve cup placement accuracy in THA. This study compared the accuracy of acetabular cup placement using a conventional accelerometer-based portable navigation (c-APN) system and a novel accelerometer-based portable navigation (n-APN) system during THA in the lateral decubitus position. This retrospective cohort study compared 45 THAs using the c-APN and 45 THAs using the n-APN system. The primary outcomes were the absolute errors between the intraoperative and postoperative values of acetabular cup radiographic inclination and anteversion angles and the percentage of cases with absolute errors within 5°. Intraoperative values were shown on navigation systems, and postoperative measurements were conducted using computed tomography images. The median absolute errors of the cup inclination angles were significantly smaller in the n-APN group than in the c-APN group (3.9° [interquartile range 2.2°-6.0°] versus 2.2° [interquartile range 1.0°-3.3°]; P = 0.002). Additionally, the median absolute errors of the cup anteversion angles were significantly smaller in the n-APN group than in the c-APN group (4.4° [interquartile range 2.4°-6.5°] versus 1.9° [interquartile range 0.8°-2.7°]; P < 0.001). Significant differences were observed in the percentage of cases with absolute errors within 5° of inclination (c-APN group 67% versus n-APN group 84%; P = 0.049) and anteversion angles (c-APN group 62% versus n-APN group 91%; P = 0.001). The n-APN system improved the accuracy of the cup placement compared to the c-APN system for THA in the lateral decubitus position.

Body morphometry did not affect the accuracy of a second-generation, miniature imageless navigation system for total hip arthroplasty (THA) using a posterior approach

IntroductionSome modern imageless navigation platforms for total hip arthroplasty (THA) rely on virtual frontal and sagittal planes determined with the patient in the lateral decubitus position. Body morphometry that changes with gender, body mass index, and other demographic factors may affect accuracy in patient positioning and consequently, navigation accuracy. The objective of this study was to analyze the influence of patient factors on the intraoperative accuracy of a second-generation imageless computer-assisted surgery platform. Methods325 consecutive patients undergoing posterior approach, navigated THA arthroplasty for primary osteoarthritis by a single surgeon were retrospectively reviewed. An optic-based imageless navigation system referenced off a generic sagittal and coronal plane was used to determine acetabular inclination and anteversion. Acetabular accuracy was determined by assessing differences between intraoperative values and those obtained from measuring standardized 6-week follow-up radiographs. The effect of age, gender, BMI, race, ethnicity, and laterality on acetabular accuracy was assessed via t-tests, Pearson correlation and ANOVA. ResultsGender had a significant impact on raw inclination accuracy (females and males had an average error of 1.41° and −1.03°, respectively – p < 0.001). There was a weak correlation between acetabular accuracy and patient age and BMI as a continuous variable (both absolute γ < 0.2). No difference was found between acetabular accuracy and BMI groups. ConclusionThis second-generation imageless computer assisted device provided accurate cup positioning regardless of patient's BMI. Gender was the only factor impacting inclination accuracy.

The Alignment of the Tibial Component in Total Knee Arthroplasty: Is a Technology-Assisted System Better Than Conventional Instrumentation?

Background Technologies such as navigation and robotics are aimedat improving tibial alignment in total knee arthroplasties (TKA) and eliminating the errors resulting from the use of manual instrumentation. Methods This prospective study analyzed 130 arthroplasties in order to determine whether navigation can improve the frontal mechanical axis of the tibia and whether the postoperative angulation of this axis differs from the preoperative one. The mean patient age was 71.8 years, and the mean BMI was 31.17. Eighty-six patients were female. The same cemented TKA model and the same imageless navigation system were used in all cases. Results The mean postoperative tibial angle following implantation was 87.65°, without any statistically significant differences with respect to the previous angulation. However, navigation was seen to result in a nearly neutral tibial axis, a larger number of cases (41.5%-60.8% {p = 0.002}) aligned within the safe zone (90° ± 3°), a smaller number of outliers, and a clustering of values around the mean. Conclusions Navigation improves the frontal positioning of the tibial component in total knee arthroplasties but does not offer any advantages as compared with conventional instrumentation.

Imageless navigation system (Naviswiss) provides accurate component position in total hip arthroplasty with lateral decubitus position for end-stage hip osteoarthritis: a prospective cohort study with CT-validation

AimsThe Naviswiss system (Naviswiss AG, Brugg, Switzerland) is a handheld imageless navigation device used to improve the accuracy of implant positioning in total hip arthroplasty (THA). However, clinical data for leg length discrepancy and femoral offset is lacking, and the validity of the system has not been reported for patients undergoing THA in the lateral decubitus position. This study aimed to report the accuracy of the device in this patient population.MethodsPatients underwent THA in the lateral decubitus position performed by a single surgeon. Component position measured by the device intraoperatively was compared to postoperative measurements on computed tomography (CT) scans. Agreement between the navigation system and postoperative measurements was reported for acetabular cup inclination, acetabular cup version, femoral offset, and leg length discrepancy.ResultsThirty-three patients were included in the analysis. The mean difference between intraoperative and postoperative CT measurements was within 2° for angular measurements and 2 mm for leg length. Absolute differences in the two indices were up to 4° and 3 mm. The mean bias was 1°–2° overestimation for cup orientation and up to 2 mm overestimation for leg length change. However, 95% limits of agreement did not exceed absolute thresholds of 10° and 10 mm, especially after correction for bias. One case (3%) was declared intraoperatively for issues with fixation on the greater trochanter.ConclusionsThe accuracy of the Naviswiss system falls within clinically acceptable recommendations for acetabular cup placement, femoral offset, and leg length for total hip arthroplasty with a anterolateral approach in lateral decubitus position. The system could be further improved with regression-based bias correction.

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

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. 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. The average surgical time was 67.3min (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. 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.

Accuracy of Leg Length and Offset Measurements During Total Hip Arthroplasty Using an Imageless Navigation System.

Introduction Leg length and offset are important considerations in total hip arthroplasty (THA). Navigation systems are capable of providing intra-operative measurements of leg length and offset, and high accuracy has been shown in experimental studies. This study assesses the accuracy of an imageless navigation system with a pinless femoral array (Hip 5.1, BrainLAB, Feldkirchen, Germany) in measuring leg length and offset changes in vivo. Methods A prospective, consecutive series of 37 patients undergoing navigated THA were included in the study. Intra-operative measurements of leg length and offset were recorded using the navigation system. For each patient, pre- and post-operative digital radiographs were scaled and analyzed to provide radiographic measurements for comparison. Results Measurements of leg length change made by the navigation system showed a strong correlation with the size of change measured radiographically (R = 0.71; p<0.0001). The mean difference between the radiographic and navigational measurement was 2.6mm ± 3.0mm (0.0-16.0mm) (mean, SD, range). The navigation system was accurate to within 1mm of the radiographic measurement in 49% of cases, within 2mm in 66% of cases, and within 5mm in 89% of cases. Measurements of offset change by the navigation system also showed a correlation with radiographic measurements, albeit less pronounced (R = 0.35; p=0.035). The mean difference between navigational and radiographic measurements was 5.5mm ± 4.7mm (0.0-16.0mm) (mean, SD, range). The navigation system was accurate within 1mm of the radiographic measurement in 22% of cases, within 2mm in 35% of cases, and within 5mm in 57% of cases. Conclusions This research demonstrates in vivo that an imageless, non-invasive navigation system is a reliable tool for intra-operative leg length (accurate within 2mm) and to a lesser extent offset measurement (accurate within 5mm) when compared to standard practice of plain film radiographs.

EVALUATING ALTERNATIVE REGISTRATION METHODS AND REFERENCE PLANES FOR IMAGELESS, COMPUTER-ASSISTED NAVIGATION DURING SUPINE TOTAL HIP ARTHROPLASTY

Imageless computer navigation systems have the potential to improve acetabular cup position in total hip arthroplasty (THA), thereby reducing the risk of revision surgery. This study aimed to evaluate the accuracy of three alternate registration planes in the supine surgical position generated using imageless navigation for patients undergoing THA via the direct anterior approach (DAA).Fifty-one participants who underwent a primary THA for osteoarthritis were assessed in the supine position using both optical and inertial sensor imageless navigation systems. Three registration planes were recorded: the anterior pelvic plane (APP) method, the anterior superior iliac spines (ASIS) functional method, and the Table Tilt (TT) functional method. Post-operative acetabular cup position was assessed using CT scans and converted to radiographic inclination and anteversion. Two repeated measures analysis of variance (ANOVA) and Bland-Altman plots were used to assess errors and agreement of the final cup position.For inclination, the mean absolute error was lower using the TT functional method (2.4°±1.7°) than the ASIS functional method (2.8°±1.7°, ρ = .17), and the ASIS anatomic method (3.7°±2.1, ρ &lt; .001). For anteversion, the mean absolute error was significantly lower for the TT functional method (2.4°±1.8°) than the ASIS functional method (3.9°±3.2°, ρ = .005), and the ASIS anatomic method (9.1°±6.2°, ρ &lt; .001). All measurements were within ± 10° for the TT method, but not the ASIS functional or APP methods.A functional registration plane is preferable to an anatomic reference plane to measure intra-operative acetabular cup inclination and anteversion accurately. Accuracy may be further improved by registering patient location using their position on the operating table rather than anatomic landmarks, particularly if a tighter target window of ± 5° is desired.

Computer-Assisted Navigation Accurately Delivers Preoperative Targets for Acetabular Component Orientation During Direct Anterior Approach Total Hip Arthroplasty.

Despite its success, total hip arthroplasty (THA) remains associated with potentially significant complications associated with component malposition. Preoperative planning can mitigate some of these potential concerns; however, the accurate intraoperative delivery of preoperative targets can be challenging. Computer-assisted navigation may assist with intraoperative target delivery, although the integration of these two technologies is relatively uncommon. We retrospectively reviewed cases of THA planned with a computed tomography-based preoperative planning software and performed with the use of an imageless, computer-assisted navigation system. Postoperative acetabular component orientation from radiographs was compared with preoperative targets and intraoperative navigation measurements. A total of 76 patients were included in the analysis. The mean anteversion target (20.0°±3.1°) did not differ significantly from the mean intraoperative navigation measurement (20.5°±3.3°; P=.30; mean difference, 2.2°±2.3°). The mean radiographic measurement (26.6°±6.5°) differed from the target by a mean of 7.5°±6.1° (P<.001). The mean inclination target (38.4°±1.9°) did not differ significantly from the mean intra-operative measurement (38.0°±1.5°; P=.20; mean difference, 1.3°±1.7°) but differed from the radiographic measurement by a mean of 5.2°±4.2° (41.8°±5.6°; P<.001). No adverse events were reported in the 90-day period following the index procedure. Our study demonstrated that an imageless navigation system can accurately deliver computed tomography-derived preoperative targets for acetabular component orientation. Differences noted on radiographs may be due to the difference in patient positioning for the postoperative imaging (standing) as compared with preoperative imaging or surgery itself (supine). [Orthopedics. 2023;46(4):218-223.].

The Impact of Varying Femoral Head Length on Hip External Rotation During Posterior-approach Total Hip Arthroplasty

BackgroundPrior investigations of total hip arthroplasty (THA) have studied the effects of prosthetic femoral head size and stem offset on hip range of motion (ROM), impingement risk, and overall hip stability to optimize the return to activities of daily living. However, the relationship between femoral head length and hip ROM, specifically external rotation (ER), has not been evaluated. The aim of our study was to intraoperatively assess how femoral head length affects hip ROM during a posterior approach THA. MethodsThirty-two patients undergoing a primary elective THA through a posterior approach were prospectively included. After final femoral stem insertion, femoral head trials were performed using the targeted head length, followed by the shorter (−3.0 to −3.5 mm) and longer (+3.0 to +4.0 mm) head length configurations. At each length, hip ER was measured using an intraoperative goniometer from an imageless navigation system. ER values across the three head lengths were compared using a repeated-measures analysis of variance and paired t-tests. ResultsVarying femoral head lengths demonstrated a statically significant and reproducible effect on intraoperative ER range (analysis of variance; P < .001) in each patient. An increased femoral head length (mean 3.4 mm) significantly decreased (P < .001) ER range by 10.8 ± 3.3° while a shortened femoral head length (mean 3.5 mm) significantly increased (P < .001) the ER ROM by 6.0 ± 3.8°. ConclusionsThe results of this study demonstrate the sensitivity of hip ROM to incremental changes in femoral head length. As ER is important for activities of daily living, inadvertent lengthening should be avoided.

A new robotically assisted technique can improve outcomes of total knee arthroplasty comparing to an imageless navigation system.

Robotic assisted total knee arthroplasty (RTKA) has shown improved knee alignment and reduced radiographic outliers. However, there remains debate on functional outcomes and patient-reported outcomes (PROMs). This study compares the 1-year clinical outcomes of a new imageless robotically assisted technique (ROSA Knee System, Zimmer Biomet, Warsaw, IN) with an imageless navigated procedure (NTKA, iAssist Knee, Zimmer, Warsaw, IN). The study is a retrospective analysis of prospectively collected data that compared the functional outcomes and PROMs of 50 imageless RTKA with 47 imageless NTKA at 1-year follow-up. Baseline characteristics, intraoperative and postoperative information were collected including complications, revisions, Knee Society Score (KSS), Knee injury and Osteoarthritis Outcome Score (KOOS) score, and Forgotten Joint Score (FJS-12). Radiographic analysis of preoperative and postoperative images evaluating hip-knee-ankle (HKA) angle was performed. There was no difference regarding baseline characteristics between the groups. Mean operative time was significantly longer in the RTKA group (122min vs. 97min; p < 0.0001). Significant differences were reported for the "Pain" (85 [RTKA] vs 79.1 [NTKA]; p = 0.0283) subsection of the KOOS score. In addition, RTKA was associated with higher maximum range of motion (119.4° vs. 107.1°; p < 0.0001) and better mean improvement of the arc of motion by 11.67° (23.02° vs. 11.36°; p < 0.0001). No significant differences were noted for other subsections of KOOS, KSS, FJS-12, complications, or limb alignment at 1-year follow-up. Imageless RTKA was associated with longer surgical time, better pain perception and improved ROM at 12-month follow-up compared with NTKA. No significant differences were reported on other PROMs, complication rates and radiographic outcomes. III.

Use of a novel imageless navigation system reduced fluoroscopy exposure and improved acetabular positioning in anterior approach total hip arthroplasty: a case-control study.

Direct anterior approach (DAA) for total hip arthroplasty (THA) frequently utilizes fluoroscopy. The purpose of this study is to assess the impact of using a novel, imageless THA navigation system on radiation exposure and acetabular cup placement consistency. This was a retrospective, single-surgeon cohort study of a consecutive group of patients who underwent DAA THA for osteoarthritis. An optic-based imageless navigation system was used to determine intraoperative acetabular inclination and anteversion angles referenced off of a generic coronal and sagittal plane in 71 cases (study group). These were compared with 71 manual cases (control group) for fluoroscopy exposure, operative duration, and acetabular placement variation. Cohorts were similar in their distributions of sex, race, ethnicity, and body mass index. Comparisons between groups were made using independent samples t tests. Alpha error was 0.05. Study patients experienced significantly less fluoroscopy exposure time {3.59 [Standard Deviation (SD) 1.95] vs. 9.15 (SD 5.98) seconds; p < 0.001} and dosage (0.30 [SD 0.23] vs. 0.78 [SD 0.63] mGy; p < 0.001). Study and control patients had similar operative times [82.69 (SD 11.70) vs. 89.54 (SD 14.60) minutes; p = 0.09]. The study group had a significantly lower radiographic variation for inclination and anteversion, based on mean proximity to the centroid of each cohort [3.55 (SD 1.88) vs. 5.39 (SD 3.51); p < 0.001] and also a greater proportion of cases that fell within 1 SD of the mean cohort inclination and anteversion (40.8% vs. 21.1%; p = 0.009). Use of a novel imageless navigation system for DAA THA significantly reduced fluoroscopic radiation exposure and improved consistency in acetabular cup placement.

Image-Less THA Cup Navigation in Clinical Routine Setup: Individual Adjustments, Accuracy, Precision, and Robustness.

Background and Objectives: Even after the ‘death’ of Lewinnek’s safe zone, the orientation of the prosthetic cup in total hip arthroplasty is crucial for success. Accurate cup placement can be achieved with surgical navigation systems. The literature lacks study cohorts with large numbers of hips because postoperative computer tomography is required for the reproducible evaluation of the acetabular component position. To overcome this limitation, we used a validated software program, HipMatch, to accurately assess the cup orientation based on an anterior-posterior pelvic X-ray. The aim of this study were to (1) determine the intraoperative ‘individual adjustment’ of the cup positioning compared to the widely suggested target values of 40° of inclination and 15° of anteversion, and evaluate the (2) ‘accuracy’, (3) ‘precision’, and (4) robustness, regarding systematic errors, of an image-free navigation system in routine clinical use. Material and Methods: We performed a retrospective, accuracy study in a single surgeon case series of 367 navigated primary total hip arthroplasties (PiGalileoTM, Smith+Nephew) through an anterolateral approach performed between January 2011 and August 2018. The individual adjustments were defined as the differences between the target cup orientation (40° of inclination, 15° of anteversion) and the intraoperative registration with the navigation software. The accuracy was the difference between the intraoperative captured cup orientation and the actual postoperative cup orientation determined by HipMatch. The precision was analyzed by the standard deviation of the difference between the intraoperative registered and the actual cup orientation. The outliers were detected using the Tukey method. Results: Compared to the target value (40° inclination, 15° anteversion), the individual adjustments showed that the cups are impacted in higher inclination (mean 3.2° ± 1.6°, range, (−2)–18°) and higher anteversion (mean 5.0° ± 7.0°, range, (−15)–23°) (p < 0.001). The accuracy of the navigated cup placement was −1.7° ± 3.0°, ((−15)–11°) for inclination, and −4.9° ± 6.2° ((−28)–18°) for anteversion (p < 0.001). Precision of the system was higher for inclination (standard deviation SD 3.0°) compared to anteversion (SD 6.2°) (p < 0.001). We found no difference in the prevalence of outliers for inclination (1.9% (7 out of 367)) compared to anteversion (1.63% (6 out of 367), p = 0.78). The Bland-Altman analysis showed that the differences between the intraoperatively captured final position and the postoperatively determined actual position were spread evenly and randomly for inclination and anteversion. Conclusion: The evaluation of an image-less navigation system in this large study cohort provides accurate and reliable intraoperative feedback. The accuracy and the precision were inferior compared to CT-based navigation systems particularly regarding the anteversion. However the assessed values are certainly within a clinically acceptable range. This use of image-less navigation offers an additional tool to address challenging hip prothesis in the context of the hip–spine relationship to achieve adequate placement of the acetabular components with a minimum of outliers.

Intraoperative knee kinematics measured by computer-assisted navigation and intraoperative ligament balance have the potential to predict postoperative knee kinematics.

This study was designed to analyze the effects of type of activity and cruciate ligament resection on knee kinematics and ligament balance after total knee arthroplasty (TKA), and to determine if intraoperative passive kinematics are associated with active kinematics. Fresh-frozen human cadaveric knees were examined. The knees were mounted on a quadriceps-driven simulator. Cruciate-retaining (CR-TKA) and posterior-substituting (PS-TKA) TKA was performed using a contemporary knee system. Active flexion (closed-kinetic chain [CKC] and open-kinetic-chain [OKC]) and passive flexion were analyzed by recording the knee kinematics using a specifically developed application of an imageless navigation system. An electronic ligament balancer was used to measure the tibiofemoral gap under constant distraction pressure. The femur rotated externally relative to the tibia during passive and active CKC flexion. The femur translated anteriorly from 10° to 50° of flexion after TKA. Beyond 50° of flexion, the femur translated posteriorly in all surgical conditions. The femoral location during active CKC flexion was posterior relative to that during active OKC. Femoral rotation and translation during passive knee flexion correlated significantly with that during active knee flexion. Posterior tilt of the electronic ligament balancer was greater with CR-TKA than with PS-TKA and correlated significantly with the anteroposterior position of the femur. Statement of Clinical Significance: Intraoperative knee kinematics measured by computer-assisted navigation and intraoperative ligament balance have the potential to predict postoperative knee kinematics.

Portable imageless navigation system and surgeon's estimate for accurate evaluation of acetabular cup orientation during total hip arthroplasty in supine position.

This prospective study aimed to clarify whether this novel device can evaluate the cup orientation during total hip arthroplasty (THA) more closely to that measured in postoperative computed tomography (CT) compared to the surgeon's estimate using a manual goniometer. We prospectively performed 30 cementless THAs via the anterolateral approach in supine position between October 2018 and July 2019, wherein cup orientation was evaluated by both a portable imageless navigation system (HipAlign) and a manual goniometer during surgeries. Primary outcome was the absolute estimate error [the absolute value of the difference between cup angles measured by postoperative CT and those measured by HipAlign (group H) or surgeon's estimate using the manual goniometer (group S) during surgery]. The number of outliers of the absolute estimate error (> 10°) in each group was also estimated. The absolute estimate error of cup inclination in groups H and S was 3.3° ± 2.7° and 3.0° ± 2.5°, respectively (p = 0.51), whereas that of cup anteversion was 3.8° ± 3.4° and 6.0° ± 3.7°, respectively (p = 0.0008). The number of outliers of the estimate error in groups H and S was one case (3.3%) and six cases (20.0%), respectively (p = 0.04). In all six outlier cases, surgeons underestimated cup anteversion during surgeries. This portable imageless navigation system was a useful method, especially for avoiding incorrect cup anteversion. Underestimation of cup anteversion during THA in the supine position with the conventional alignment assisting device should be given attention.

Augmented reality-based navigation system applied to tibial bone resection in total knee arthroplasty

BackgroundThis pilot study was performed to examine the accuracy of the AR-KNEE system, an imageless navigation system using augmented reality (AR) technology for total knee arthroplasty. The AR-KNEE system enables the surgeon to view information from the navigation superimposed on the surgical field on a smartphone screen in real time.MethodsUsing the AR-KNEE system, one surgeon resected 10 tibial sawbones with viewing the tibial axis and aiming varus/valgus, posterior slope, internal/external rotation angles, and resection level superimposed on the surgical field. We performed computed tomography of the resected sawbones and measured the varus/valgus, posterior slope, and internal/external rotation angles using a designated computer software. The thickness of the resected bone was measured using digital calipers.ResultsThe absolute differences between the values displayed on the smartphone screen and the measurement values for varus/valgus, posterior slope, internal/external rotation angles, and thickness of the resected bone were 0.5° ± 0.2°, 0.8° ± 0.9°, 1.8° ± 1.5°, and 0.6 mm ± 0.7 mm, respectively.ConclusionsThis pilot study using sawbones suggested that the AR-KNEE system may provide reliable accuracy for coronal, sagittal, and rotational alignment in tibial bone resection during total knee arthroplasty.

Periacetabular osteotomy using an imageless computer-assisted navigation system: a new surgical technique.

Periacetabular osteotomy (PAO) is an effective surgical treatment for hip dysplasia. The goal of PAO is to reorient the acetabulum to improve joint stability, lessen contact stresses and slow the development of hip arthrosis. During PAO, the acetabulum is repositioned to adequately cover the femoral head. PAO preserves the weight-bearing posterior column of the pelvis, maintains the acetabular blood supply and retains the hip abductor musculature. The surgical technique needed to perform PAO is technically demanding, with correct repositioning of the acetabulum the most important—and challenging—aspect of the procedure. Imageless navigation has proven useful in other technically challenging surgeries, although its use in PAO has not yet been investigated. We have modified the standard technique for PAO to include the use of an imageless navigation system to confirm acetabular fragment position following osteotomy. Here, we describe the surgical technique and discuss the potential of this modified technique to improve patient-related outcomes.

Revising Substantial Leg Length Discrepancy in Total Hip Arthroplasty Using Computer-assisted Navigated Systems: A Case Series of Three Patients

One of the primary challenges of total hip arthroplasty (THA) is equalizing the limb lengths to re-establishing normal hip biomechanics. Post-operative leg length discrepancies (LLD) lead to patient dissatisfaction and are a main source of orthopedic malpractice cases. The aim of this case series was to document three cases of substantial LLD that were corrected during THA with the assistance of an imageless computer navigation system. Medical records were reviewed for history and radiographs were consulted. All patients in this series presented with complaints related to hip fractures and reported a significant lengthening of leg length following THA. No surgical complications of adverse events were reported. In these cases, imageless navigation provided intraoperative measurements of leg length which allowed for enhanced accuracy of component placement and improved outcomes following surgery.

Precision and accuracy of imageless navigation versus freehand implantation of total hip arthroplasty: A systematic review and meta-analysis.

Total hip arthroplasty (THA) is named the most successful surgical procedure of the twentieth century. To remain a success in the twenty-first century THA should meet the higher demands of patients and society with regard to technical and functional outcome, costs and implant survival. To meet these demands optimal acetabular cup positioning is necessary. An imageless navigation system (NAV) might prevent malpositioning of the acetabular cup in THA. The aim of this study has been to compare the precision and accuracy of the anteversion and inclination of the acetabular cup position after NAV implantation and after freehand implantation of THA. A systematic review and meta-analysis was conducted to assess the precision (variance) and accuracy (deviation from the target) from all available high-quality randomised control trials to date. Six out of seven studies concluded a statistically significant difference in precision in anteversion between the NAV group and the freehand group. Five out of seven studies concluded a statistically significant difference in precision in inclination. There is a significantly better accuracy for the NAV group than for the freehand group for anteversion (p=0.002) and for inclination (p=0.01). This study showed that NAV placement is more precise and has an improved accuracy for anteversion and inclination than freehand placement of the acetabular cup. However, there is a lack of evidence to support an improved functional outcome and a reduction of complications and revisions.

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.