Accelerometer-based Portable Navigation System Research Articles

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.

Two- and three-dimensional measurements of leg length change using an accelerometer-based portable navigation system in total hip arthroplasty

BackgroundThe aim of this study was examining the accuracy of accelerometer-based portable navigation systems (HipAlign) when measuring leg length changes using two-dimensional (2D) and three-dimensional (3D) methods.MethodsInclusion criteria were patients ≥ 20 years old with symptomatic hip disease who underwent primary total hip arthroplasty (THA) in the supine position using HipAlign between June 2019 and April 2020. The exclusion criteria were patients who underwent THA via a posterior approach. We examined correlations between the leg length change measurement with HipAlign and either 2D or 3D measurement. We performed a multivariate analysis to determine which factors may have influenced the absolute error results.ResultsThis study included 34 patients. The absolute error in leg length change between the HipAlign and 3D measurement (4.0 mm) was greater than the HipAlign and 2D measurement (1.7 mm). There were positive correlations between leg length change with HipAlign and 2D and 3D measurements. Male patients had larger errors with 2D measurement. No significant factors were identified for 3D measurement.ConclusionHipAlign provided acceptable measurement accuracy for leg length changes.

The accuracy of an accelerometer-based portable navigation system for total hip arthroplasty using 3D CT measurement in the supine position: a prospective multicenter study

PurposeThis multicenter prospective study aimed to evaluate the accuracy of the cup alignment of an accelerometer-based portable navigation system (AP navigation) for a total hip arthroplasty (THA) in spine position. MethodsThis study prospectively enrolled 324 THAs using supine position in 9 hospitals. An AP navigation was used for cup fixation and the intraoperative navigation data (cup alignment, pelvic tilt, and pelvic rotation) were recorded. Computed tomography (CT) of the pelvis was performed 2 weeks post-operatively and cup alignment was measured on 3D-CT images. ResultThe accuracy (absolute difference in cup alignment between the intraoperative navigation record and postoperative 3D-CT measurements) was 3 ​± ​3° (mean ​± ​standard deviation) for cup inclination and 3 ​± ​3° for cup anteversion. The pelvis tilted anteriorly in 148 hips (46%) and posteriorly in 162 hips (50%), and did not tilt in 14 hips (4%). The pelvis rotated toward the operating side in 179 hips (55%), toward the contralateral side in 112 hips (35%), and did not rotate in 33 hips (10%). Multiple regression analysis showed that the patients’ characteristics (sex, body mass index, diagnosis, Crowe classification, laterality, intraoperative pelvic tilt, intraoperative pelvic rotation, and cup size) and the surgical factors (approach, preparation time, number of screws, and institution) did not affect the accuracy of the navigation system. ConclusionsThis is the first prospective multicenter study of this navigation system. The accuracy was not affected by patient characteristics, surgical factors, or substantial pelvic movement during cup fixation.

The Accuracy of a Portable Accelerometer-Based Navigation System for Tibial Alignment Can be Reliable during Total Knee Arthroplasty for Obese Patients.

A portable accelerometer-based navigation system can be useful for achieving the target alignment. Tibial registration is based on the medial and lateral malleoli; however, the identification of landmarks may be difficult in obese (body mass index [BMI] >30 kg/m2) patients whose bones are not easily palpable from the body surface. This study compared tibial component alignment achieved using a portable accelerometer-based navigation system (Knee Align 2 [KA2]) in obese and control groups and aimed to validate the accuracy of bone cutting in obese patients. A total of 210 knees that underwent primary total knee arthroplasty using the KA2 system were included. After 1:3 propensity score matching, there were 32 and 96 knees in the BMI >30 group (group O) and BMI ≤30 group (group C), respectively. The absolute deviations of the tibial implant from the intended alignment were evaluated in the coronal plane (hip-knee-ankle [HKA] angle and medial proximal tibial angle) and sagittal plane (posterior tibial slope [PTS]). The inlier rate of each cohort, which was defined as tibial component alignment within 2 degrees of the intended alignment, was investigated. In the coronal plane, the absolute deviations of the HKA and MPTA from the intended alignment were 2.2 ± 1.8 degrees and 1.8 ± 1.5 degrees in group C and 1.7 ± 1.5 degrees and 1.7 ± 1.0 degrees in group O (p = 1.26, and p = 0.532). In the sagittal plane, the absolute deviations of the tibial implant were 1.6 ± 1.2 degrees in group C and 1.5 ± 1.1 degrees in group O (p = 0.570). The inlier rate was not significantly different between group C and group O (HKA: 64.6 vs. 71.9%, p = 0.521; MPTA: 67.7 vs. 78.1%, p = 0.372; PTS: 82.2 vs. 77.8%, p = 0.667). The accuracy of tibial bone cutting for the obese group was comparable to that of the control group. An accelerometer-based portable navigation system can be useful when attempting to achieve the target tibial alignment in obese patients. LEVEL OF EVIDENCE: Level IV.

Does Augmented Reality-based Portable Navigation Improve the Accuracy of Cup Placement in THA Compared With Accelerometer-based Portable Navigation? A Randomized Controlled Trial.

Previous studies reported good outcomes of acetabular cup placement using portable navigation systems during THA. However, we are aware of no prospective studies comparing inexpensive portable navigation systems using augmented reality (AR) technology with accelerometer-based portable navigation systems in THA. (1) Is the placement accuracy of the acetabular cup using the AR-based portable navigation system superior to that of an accelerometer-based portable navigation system? (2) Do the frequencies of surgical complications differ between the two groups? We conducted a prospective, two-arm, parallel-group, randomized controlled trial involving patients scheduled for unilateral THA. Between August and December 2021, we treated 148 patients who had a diagnosis of osteoarthritis, idiopathic osteonecrosis, rheumatoid arthritis, or femoral neck fracture and were scheduled to undergo unilateral primary THA. Of these patients, 100% (148) were eligible, 90% (133) were approached for inclusion in the study, and 85% (126) were finally randomized into either the AR group (62 patients) or the accelerometer group (64 patients). An intention-to-treat analysis was performed, and there was no crossover between groups and no dropouts; all patients in both groups were included in the analysis. There were no differences in any key covariates, including age, sex, and BMI, between the two groups. All THAs were performed via the modified Watson-Jones approach with the patient in the lateral decubitus position. The primary outcome was the absolute difference between the cup placement angle displayed on the screen of the navigation system and that measured on postoperative radiographs. The secondary outcome was intraoperative or postoperative complications recorded during the study period for the two portable navigation systems. There were no differences between the AR and accelerometer groups in terms of the mean absolute difference in radiographic inclination angle (3° ± 2° versus 3° ± 2° [95% CI -1.2° to 0.3°]; p = 0.22). The mean absolute difference in radiographic anteversion angle displayed on the navigation screen during surgery compared with that measured on postoperative radiographs was smaller in the AR group than that in the accelerometer group (2° ± 2° versus 5° ± 4° [95% CI -4.2° to -2.0°]; p < 0.001). There were few complications in either group. In the AR group, there was one patient each with a surgical site infection, intraoperative fracture, distal deep vein thrombosis, and intraoperative pin loosening; in the accelerometer group, there was one patient each with an intraoperative fracture and intraoperative loosening of pins. Although the AR-based portable navigation system demonstrated slight improvements in radiographic anteversion of cup placement compared with the accelerometer-based portable navigation system in THA, whether those small differences will prove clinically important is unknown. Until or unless future studies demonstrate clinical advantages that patients can perceive that are associated with such small radiographic differences, because of the costs and the unquantified risks associated with novel devices, we recommend against the widespread use of these systems in clinical practice. Level I, therapeutic study.

A new accelerometer-based portable navigation system provides high accuracy of acetabular cup placement in total hip arthroplasty in both the lateral decubitus and supine positions.

No studies have compared the accuracy of acetabular cup placement in total hip arthroplasty (THA) in the supine and lateral decubitus positions using the same portable navigation system. Thus, this study aimed to compare the accuracy of acetabular cup placement using a new accelerometer-based portable navigation system combined with an infrared stereo camera and inertial measurement unit between the supine and lateral decubitus positions. This retrospective study compared 45 THAs performed in the supine position (supine group) and 44 THAs performed in the lateral decubitus position (lateral group) using the same portable navigation system. The primary outcome was the absolute errors of cup placement angles, defined as the absolute values of the differences between cup radiographic inclination and anteversion angles displayed on the navigation system and those measured on postoperative computed tomography images. No significant difference in the median absolute error of the cup inclination angle (supine group 1.7° [interquartile range 0.8°-3.1°] vs. lateral group 2.1° [interquartile range 1.0°-3.7°]; p = 0.07) was found between the two groups. Similarly, no significant difference in the median absolute error of the anteversion angle (supine group 1.9° [interquartile range 0.8°-3.4°] vs. lateral group 2.1° [interquartile range 0.9°-3.1°]; p = 0.42) was found. This new accelerometer-based portable navigation system may provide high accuracy of the cup placement in THA in the lateral decubitus and supine positions.

Comparing the accuracy of three-dimensional mini-optical portable navigation and accelerometer-based portable navigation system for acetabular cup placement during total hip arthroplasty.

This study compared the accuracy of three dimensional (3D) mini-optical navigation and accelerometer-based portable navigation systems for cup positioning during a total hip arthroplasty (THA) in the supine position. This retrospective cohort study assessed data for 77 hips using 3D mini-optical navigation (n = 37) and accelerometer-based portable navigation (n = 40). The patients underwent THA through the mini-anterolateral approach in the supine position using a portable navigation system. We assessed the preoperative target angles, recorded intraoperative cup angles, postoperative CT imaging angles, cup angle measurement errors, and other clinical parameters. The mean absolute differences in radiographic inclination were similar between 3D mini-optical navigation and accelerometer-based portable navigation systems during THA in the supine position (2.8° ± 1.7° vs 2.8° ± 1.9°, p = 0.637). The mean absolute differences in radiographic anteversion were also similar (2.6° ± 2.3° vs 2.5° ± 1.9°, p = 0.737). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of > 5°) was significantly associated with body mass index (BMI) in accelerometer-based portable navigation but not in 3D mini-optical navigation. This is the first study to compare the accuracy of cup positioning between 3D mini-optical and accelerometer-based navigations in THA in the supine position. Both portable navigation systems accurately identified the orientation of cup placement. The accuracy of 3D mini-optical navigation is not affected by high BMI and may be preferred over other options in such patients.

Augmented Reality- vs Accelerometer-Based Portable Navigation System to Improve the Accuracy of Acetabular Cup Placement During Total Hip Arthroplasty in the Lateral Decubitus Position.

There have been no studies regarding the effectiveness of augmented reality (AR)-based portable navigation systems compared with accelerometer-based portable navigation systems in total hip arthroplasty (THA). We retrospectively compared THAs performed using an AR-based portable navigation system (n= 45) and those performed using an accelerometer-based portable navigation system (n= 42). All THAs were performed with the patient in the lateral decubitus position. The primary outcome was the absolute difference between cup placement angles displayed on the navigation screen and those measured on postoperative X-ray. The mean absolute differences were significantly smaller in the AR-based portable navigation system group than the accelerometer-based portable navigation system group in radiographic inclination (2.5° ± 1.7° vs 4.6° ± 3.1°; 95% confidence interval 1.1°-3.2°, P < .0001). Similarly, the mean absolute differences were significantly better in the AR-based portable navigation system group in radiographic anteversion (2.1° ± 1.8° vs 6.4° ± 4.2°; 95% confidence interval 3.0°-5.7°, P < .0001). Neither hip dislocation, surgical site infection, nor other complications associated with use of the navigation system occurred in either group. The AR-based portable navigation system may provide more precise acetabular cup placement compared with the accelerometer-based portable navigation system in THA.

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

BackgroundThis 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. MethodsA 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. ResultsThe 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. ConclusionsOur 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.

Usefulness of an Accelerometer-Based Portable Navigation System for Total Knee Arthroplasty: A Multicenter Prospective Randomized Controlled Trial.

An accelerometer-based portable navigation system was recently introduced to improve prosthetic alignment during total knee arthroplasty (TKA). The purpose of this multicenter prospective randomized controlled trial (RCT) was to evaluate the effects of this accelerometer-based portable navigation system for achieving more accurate alignment during TKA in the clinical setting. One hundred patients with primary varus osteoarthritis of the knee were enrolled in this prospective RCT conducted in 5 hospitals. A navigation system was utilized in 50 patients (navigation group), and a conventional intramedullary femoral guide and an extramedullary tibial guide were utilized in 50 patients (conventional group). At 6 months postoperatively, weight-bearing radiographs were obtained of the whole operative leg. An experienced surgeon who was blinded to the treatment assignments then measured the alignment to 1 decimal place with use of computer software. Power analysis showed that 41 knees were required in each group. There were no complications as a result of the use of the accelerometer-based portable navigation system. Postoperative radiographs were obtained in 45 patients from each group. There were no significant differences in sex, age, height, body weight, body mass index, preoperative femorotibial angle, and operative time between groups. The absolute differences of the femoral prosthesis (p = 0.01), tibial prosthesis (p < 0.01), and hip-knee-ankle angle (p < 0.01) from a neutral mechanical axis were less in the navigation group compared with those in the conventional group. Alignment outliers (>2° away from the neutral mechanical axis) of the tibial prosthesis and hip-knee-ankle angle were less in the navigation group (9% and 27%, respectively) compared with those in the conventional group (31% and 49%; p = 0.01 and p = 0.04, respectively). To our knowledge, this is the first multicenter prospective RCT to evaluate an accelerometer-based portable navigation system. An accelerometer-based portable navigation system provides more accurate prosthetic and limb alignment in the coronal plane than conventional techniques, without extended operative time or an increased rate of complications. The results of this study may help orthopaedic surgeons decide whether or not to use an accelerometer-based portable navigation system. Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Accuracy of acetabular cup insertion in an anterolateral supine approach using an accelerometer-based portable navigation system.

The purpose of this study was to determine the accuracy of acetabular cup insertion during total hip arthroplasty (THA) in a supine position using an accelerometer-based portable navigation system. A single-surgeon study was conducted in which 62 prospective patients with navigation and 42 retrospective patients without navigation as historical controls were compared. The patients underwent THA via an anterolateral supine approach. The absolute values of errors of radiographic inclination and anteversion were calculated. The navigation error was also calculated. The factors that affected the absolute values of errors of cup alignment were determined. The mean absolute error of the postoperative CT measurement from the target angle for radiographic inclination was 3.8° in the navigation group and 6.6° in the control group (P < 0.001). The mean absolute error for anteversion was 3.3° in the navigation group and 5.9° in the control group (P < 0.001). The mean absolute values of navigation error were 3.7° ± 2.8° in inclination and 3.0° ± 2.6° in anteversion. Changes in the pelvic tilt angle among preoperative, intraoperative, and postoperative were the significant risk factors for the absolute values of navigation error of anteversion relative to the anterior pelvic plane. Other factors affecting the absolute values of errors in the navigation group were not found for radiographic inclination and anteversion. The portable navigation system significantly improved the accuracy of cup inclination and anteversion. Changes in the pelvic tilt were the risk factors for the error of anteversion relative to the anterior pelvic plane.

Comparison of accuracy of cup position using portable navigation versus alignment guide in total hip arthroplasty in supine position.

Accelerometer-based portable navigation systems in supine total hip arthroplasty (THA) have been developed, but there are no reports on the accuracy of cup placement. We aimed to investigate and compare the accuracy of the accelerometer-based portable navigation system versus the acetabular alignment guide placed on the pelvis in THA using the direct anterior approach (DAA). Both devices tracked changes in the pelvic position. In this single-centre, retrospective study, we reviewed 115 hips in 113 patients who underwent primary THA via the DAA using an accelerometer-based portable navigation system in the supine position (portable navigation group) and 106 hips in 101 patients who underwent THA using an acetabular alignment guide (alignment guide group) as controls. Hips were evaluated postoperatively using computed tomography to measure cup orientation. The accuracy of cup orientation was compared between the 2 groups. Absolute values of inclination error were 3.1° ± 2.2° and 2.9° ± 2.3° (p = 0.708) in the portable navigation and alignment guide groups and those of anteversion error were 2.8° ± 2.3° and 3.7° ± 2.7°, respectively (p = 0.005). The number of cups placed within 10° of error was 98.3% and 96.2% in the portable navigation and alignment guide groups, respectively (p = 0.304). The portable navigation group had significantly more hips (72.2%) placed within a 5° margin of error than did the alignment guide group (56.6%) (p = 0.016). High accuracy in cup placement was achieved using accelerometer-based portable navigation in supine THA. Using a navigation system may contribute to improved long-term outcomes.

Examination of Component Placement Accuracy in Total Knee Arthroplasty Using an Accelerometer-Based Portable Navigation System

Examination of Component Placement Accuracy in Total Knee Arthroplasty Using an Accelerometer-Based Portable Navigation System

Evaluation of the accuracy of acetabular cup orientation using the accelerometer-based portable navigation system

BackgroundAccurate orientation of acetabular and femoral components is important during total hip arthroplasty (THA). In recent years, several navigation systems have been developed. However, these navigation systems for THA are unpopular worldwide because of their high cost. We assessed the orientation accuracy of cups inserted using a disposable accelerometer-based portable navigation system for THAs. MethodsThis was a prospective cohort study. We analyzed 63 hips with navigation prospectively and 30 hips without navigation retrospectively as historical control. The patients underwent THA via the mini anterolateral approach in the supine position using an accelerometer-based portable navigation system. We compared the preoperative target angles, intraoperative cup angles using navigation records, postoperative angles using postoperative CT data, measurement errors of cup angles, and clinical parameters such as sex, treated side, age at surgery, and body mass index (BMI). ResultsThe average absolute error (postoperative CT-navigation record) was 2.7 ± 2.1° (inclination) and 2.7 ± 1.8° (anteversion), and the absolute error (postoperative CT-preoperative target angle) was 2.6 ± 1.9° (inclination) and 2.7 ± 2.2° (anteversion). The absolute error between postoperative CT and target angle with navigation was significantly lower than the error without navigation (inclination; p = 0.025, anteversion; p = 0.005). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of over 5°) was significantly associated with BMI value (OR: 1.3, 95% CI: 1.1–1.7). The absolute measurement error of cup inclination and anteversion was significantly correlated with patients’ BMI (inclination error: correlation coefficient = 0.53, p < 0.001, anteversion error: correlation coefficient = 0.58, p < 0.001). ConclusionsThe clinical accuracy of accelerometer-based portable navigation is precise for the orientation of cup placement, although accurate cup placement was affected by high BMI. This is the first study to report the accuracy of accelerometer-based portable navigation for THA in the supine position.

Improved implant alignment accuracy with an accelerometer-based portable navigation system in medial unicompartmental knee arthroplasty

This study aimed to examine the accuracy of tibial implant alignment using an accelerometer-based portable navigation system in unicompartmental knee arthroplasty (UKA). This retrospective matched case-control study reviewed 51 UKAs performed using an accelerometer-based portable navigation system, matched with 51 UKAs performed using conventional extramedullary rods. Coronal alignment and posterior slope of the tibial implant were measured on postoperative radiographs, and differences from preoperative planning were examined. Outliers and accuracy of tibial implant alignment were compared between the portable navigation and conventional groups using Fisher's exact test and Mann-Whitney U test, respectively. In the portable navigation group, 100% of the implants were aligned within 3.0° of both target coronal and sagittal implant alignment. In the conventional group, 76.5% and 88.2% of the implants were within 3.0° of both target coronal and sagittal implant alignment. Statistical analysis revealed that outliers of coronal and sagittal alignment were significantly less in the portable navigation group than in the conventional group (P < 0.05). In addition, the absolute value difference between postoperative measurement and preoperative planning of both coronal and sagittal alignment was significantly smaller in the portable navigation group than in the conventional group (P < 0.05). The portable navigation system improved the accuracy of tibial implant alignment in UKA. We found that 100% of the implants were aligned within 3.0° of both target coronal and sagittal implant alignment. The portable navigation system decreased the outliers of tibial coronal and sagittal alignment. Retrospective case-control study, Level III.

Accuracy of cup orientation and learning curve of the accelerometer-based portable navigation system for total hip arthroplasty in the supine position

To assess the accuracy of cup orientation and learning curve of the disposable accelerometer-based portable navigation system for total hip arthroplasty (THA) in the supine position. A total of 75 patients who underwent THA through the anterolateral supine approach (ALS) with an accelerometer-based portable navigation system for the supine position (HipAlign®) between July 2017 and October 2018 were analyzed in this study. We compared the intraoperative cup angles using navigation records with the postoperative angles using postoperative computed tomography (CT) data. All patients were categorized into the following groups according to the course of three discrete, sequential operative time periods: 1-25 (initial group), 26-50 (intermediate group), and 51-75 (recent group). We compared the accuracy of cup inclination and anteversion among the three groups. The time required for navigation and the operative time of all patients were measured. The average absolute error in measurement (postoperative CT-navigation record) was 2.6° ± 2.7° (inclination) and 2.8° ± 2.7° (anteversion). There were no significant differences among the three groups. The average time required for navigation and the operative time were 365.1 ± 90.3 s and 76.1 ± 1.6 min, respectively. The required time for HipAlign® navigation and operative time were constant in most patients, except for those of the initial five cases. The accelerometer-based portable navigation system provides good accuracy of cup orientation, has a short learning curve, and requires a minimal surgical time for THA in supine position.

An accelerometer-based portable navigation system improved prosthetic alignment after total knee arthroplasty in 3D measurements.

This study aimed to compare prosthetic alignment using three-dimensional (3D) measurements following total knee arthroplasty (TKA) performed using an accelerometer-based portable navigation system (KneeAlign2) versus the conventional technique. A total of 159 patients who had primary osteoarthritis of the knee with varus deformity underwent TKA. The KneeAlign2 system was used for distal femoral resection and tibial resection in 78 knees, and the conventional instrumentation (intramedullary for the femur and extramedullary for the tibia) was used in 81 knees. 3D computed tomography (CT) scans of the whole leg were taken after TKA. Femoral and tibial prosthetic alignments in the coronal, sagittal, and axial planes were measured using computer software. The operation time and estimated blood loss were calculated. Deep venous thrombosis (DVT) and pulmonary embolism (PE) were evaluated using the contrast-enhanced multi-detector row CT at 1 week after TKA. In the femoral coronal plane, the mean and standard deviation of prosthetic alignment from neutral alignment were 1.2° [95% confidence interval (CI) 1.0°-1.4°) in the navigation group and 1.6° (95% CI 1.3°-2.0°) in the conventional group (p = 0.03). The femoral component outliers (> 3° away from the goal alignment) using the navigation system and the conventional technique were 3 and 15%, respectively, in the coronal plane (p < 0.01), and 15 and 43%, respectively, in the sagittal plane (p < 0.01). The outliers in tibial coronal and tibial sagittal planes were not statistically different between the two groups. There were no statistically significant differences between the two groups in operation time, blood loss, DVT, and PE. Using an accelerometer-based portable navigation system decreased the outliers of prosthetic alignment in femoral coronal and sagittal planes, and did not increase the complications such as operation time, blood loss, DVT, and PE. To our knowledge, this study is the first to investigate the usefulness of an accelerometer-based portable navigation system using the validated 3D measurement. III.

Comparison of an Accelerometer-Based Portable Navigation System, Patient-Specific Instrumentation, and Conventional Instrumentation for Femoral Alignment in Total Knee Arthroplasty.

PurposeThe KneeAlign2 (KA2, OrthoAlign Inc.) accelerometer-based portable navigation system and patient-specific instrumentation (PSI; Signature, ZimmerBiomet) are widely used for ideal femoral component alignment in total knee arthroplasty (TKA). However, there has been no comparative study of the KA2 system, PSI, and conventional intramedullary instrumentation (CON). The purpose of this study was to compare the accuracy in achieving proper femoral component alignment and clinical features by using the KA2 navigation system, PSI, and CON.Materials and MethodsWe retrospectively compared the accuracy of femoral component alignment of 34 TKAs performed with the KA2 system for implantation of the femoral component, 32 TKAs with PSI, and 33 TKAs with CON.ResultsIn the coronal plane, use of the KA2 system was more likely to result in optimal femoral component alignment than the CON and PSI (p<0.01). In the sagittal plane, use of the KA2 system was more likely to result in optimal component alignment than PSI, but the difference between the KA2 and CON was insignificant.ConclusionsThe portable accelerometer-based KA2 navigation system enabled ideal femoral implantation in the coronal and sagittal planes, as compared to the PSI or CON.

Usefulness of an accelerometer-based portable navigation system in total knee arthroplasty.

The aim of this study was to evaluate the effects of using a portable, accelerometer-based surgical navigation system (KneeAlign2) in total knee arthroplasty (TKA) on the alignment of the femoral component, and blood loss. A total of 241 consecutive patients with primary osteoarthritis of the knee were enrolled in this prospective, randomised controlled study. There were 207 women and 34 men. The mean age of the patients was 74.0 years (57 to 89). The KneeAlign2 system was used for distal femoral resection in 121 patients (KA2 group) and a conventional intramedullary femoral guide was used in 120 patients (IM group). One patient (0.8%) in the KA2 group and 19 in the IM group had an alignment which was > 3° away from the neutral mechanical axis (p < 0.01). The mean deviation from neutral alignment was 1.01° (standard deviation (sd) 1.0°) in the KA2 group and 1.93° (sd 1.7°) in the IM group (p < 0.01). Blood loss was significantly less in the KA2 group compared with the IM group (784 ml (sd 357) versus 1071 ml (sd 310), p < 0.001). The KneeAlign2 system provides a technically straightforward method for identifying the femoral head and performing an accurate distal femoral resection at TKA with significantly less blood loss compared with a conventional intramedullary guide. Cite this article: Bone Joint J 2017;99-B:1047-52.