Handheld Navigation Systems Research Articles

Total knee replacement with an accelerometer-based, hand-held navigation system improves knee alignment: reliable in all patients.

Achieving adequate alignment has traditionally been an important goal in total knee arthroplasty to achieve long-term implant survival. While accelerometer-based hand-held navigation systems (ABN) has been introduced as a way to achieve alignment, there is a limited body of evidence on its accuracy, especially in patients under 65 years with differing etiologies for knee arthritis. This study aimed to assess the precision of a specific ABN system in restoring the mechanical axis and report surgical variables and complications, with particular attention to younger patients. We conducted a retrospective review of 310 primary TKA performed with ABN from May 2016 to February 2021. The mean patient age was 67.4 (SD 8.9) years, with 43% under 65 years and mean body mass index of 33.2 (SD 6.8). The average surgical time was 96.8min (57-171) and the average follow-up was 3.3 years (1.9-6.7). Data regarding length of stay, pain, range of motion (ROM), complications, and reinterventions were collected from the institutional joint arthroplasty registry and the medical records. Preoperative mechanical axis measurements and postoperative radiological data, including mechanical axis, component alignment and mechanical alignment outliers were analyzed. The mean preoperative mechanical axis was 175.4° (SD 7.6), with 248 knees (80%) in preoperative varus. The mean postoperative mechanical axis was 179.5° (SD 1.96) with 98% of knees falling within ± 3° of the neutral mechanical axis. Only 6 knees (2 varus, 4 valgus) fell outside the ± 3° range. And 3 knees (1 varus, 2 valgus) fell outside the ± 5° range. In the sagittal plane, 296 knees (95.5%) knees were within ± 3° of goal of 3 degrees of femoral flexion and 302 (97.4%) knees were within ± 2° of goal 1° of slope for tibial component. Far outliers (alignment outside ± 5° of targeted position) were found in 3 knees. Factors such as posttraumatic arthrosis, previous surgery, presence of retained hardware, and age below 65 years were not associated with increase in alignment outliers and far outliers. No complications related to the navigation system were observed. There were 22 complications and 20 reoperations, including 2 revisions for periprosthetic joint infection and 1 revision for flexion instability. Patients that required knee manipulation achieved an ultimate flexion of 110° (SD 14.1). The ABN system proved to be user-friendly and accurate in reducing alignment outliers in both coronal and sagittal planes in all patient populations. It offers a straightforward navigation solution while preserving surgeon autonomy and the use of traditional surgical tools. These findings advocate for the integration of this navigation system as a valuable tool to enhance the precision of TKA surgery in all patient groups.

Trends in navigation-handheld systems

Navigation-assisted surgical procedures in orthopedics and trauma surgery have become increasingly widespread over the last 20years. In addition to applications in spinal surgery, they are primarily available for knee and hip endoprosthetics. On the one hand, computer-assisted procedures have been increasingly expanded with robotic assistance systems in recent years, and on the other hand, so-called handheld navigation systems have been developed, which enable specialized use directly in the operating field at lower acquisition costs. The aim of this overview is to describe current handheld systems and to present the respective technical principles and the available scientific results. Three handheld systems for TKA use, two for THA use and one system to support pedicle screw placement on the spine are presented.

High degree of alignment precision associated with total knee arthroplasty performed using a surgical robot or handheld navigation.

The purpose of this study was to compare the precision of bony resections during total knee arthroplasty (TKA) performed using different computer-assisted technologies. Patients who underwent a primary TKA using an imageless accelerometer-based handheld navigation system (KneeAlign2®, OrthAlign Inc.) or computed tomography-based large-console surgical robot (Mako®, Stryker Corp.) from 2017 to 2020 were retrospectively reviewed. Templated alignment targets and demographic data were collected. Coronal plane alignment of the femoral and tibial components and tibial slope were measured on postoperative radiographs. Patients with excessive flexion or rotation preventing accurate measurement were excluded. A total of 240 patients who underwent TKA using either a handheld (n = 120) or robotic (n = 120) system were included. There were no statistically significant differences in age, sex, and BMI between groups. A small but statistically significant difference in the precision of the distal femoral resection was observed between the handheld and robotic cohorts (1.5° vs. 1.1° difference between templated and measured alignments, p = 0.024), though this is likely clinically insignificant. There were no significant differences in the precision of the tibial resection between the handheld and robotic groups (coronal plane 0.9° vs. 1.0°, n.s.; sagittal plane 1.2° vs. 1.1°, n.s.). There were no significant differences in the rate of overall precision between cohorts (n.s.). A high degree of component alignment precision was observed for both imageless handheld navigation and CT-based robotic cohorts. Surgeons considering options for computer-assisted TKA should take other important factors, including surgical principles, templating software, ligament balancing, intraoperative adjustability, equipment logistics, and cost, into account. III.

Accelerometer-Based Handheld Navigation Instrumentation in Total Knee Arthroplasty Decrease Blood Loss Compared to Conventional Instrumentation: A Prospective Comparative Study.

Introduction Total Knee Arthroplasty (TKA) can be associated with significant peri- and post-operative blood loss necessitating blood transfusion. The blood loss may be relatively less when the accelerometer-based handheld navigation system (HHNS) is used, as there is neither a need for intramedullary breach nor additional pin insertions. The primary hypothesis was that HHNS instrumentation reduced perioperative blood loss when compared with conventional instrumentation, and to prove this, we compared the perioperative parameters like tourniquet time, hemoglobin loss, and estimated blood loss between patients undergoing total knee arthroplasty using conventional instrumentation with handheld navigation instrumentation. Methods This prospective comparative study involves 40 patients in the HHNS groupand 40 patients in the conventional group based on the instrumentation used, respectively. Tourniquet was used in all the cases. Patient characteristics like age, sex, body mass index (BMI), American Society of Anaesthesiologists (ASA) grade, and Charlson Comorbidity Index (CCI) were recorded. The perioperative parameters like tourniquet time, the estimated blood loss, hemoglobin loss, blood transfusions, and the number of units transfused were recorded and compared between the groups. Results There was no significant difference in age, BMI, ASA grade, or CCI between the two groups. The tourniquet time was 83.7 ± 9.6 in the navigation and 73.9 ± 10.3 in the conventional group. The estimated Hb loss was lower at 2.5 ± 1.6 in the HHNS group compared to 3.0 ± 1.8 in the conventional group (p<0.001). Similarly, estimated blood loss was also lower at 830 ± 285ml for the HHNS group compared to 1088 ± 228 in the conventional group. Two patients in the navigation group had a total of four units transfused, whereas three patients in the conventional group had five units of blood transfusion. Conclusions The primary hypothesis that HHNS reduced perioperative blood loss was confirmed by the results of our study. We demonstrated that HHNS instrumentation significantly decreased the estimated blood loss, drain volume, and hemoglobin loss compared to conventional instrumentation with similar operating times. Though blood transfusions were seen in fewer patients, there was no significant reduction in blood transfusions by HHNS instrumentation.

Comparative Analysis of Radiological Evaluation and Early Functional Outcomes of Total Knee Arthroplasty Using an Accelerometer-Based Handheld Navigation System and Conventional Instrumentation: A Prospective Study.

BackgroundAn accelerometer-based handheld navigation system (HHNS) for total knee arthroplasty (TKA) does not require a large console needed for computer-assisted navigation systems and has been shown to decrease component malalignment in TKA. The study aimed to use HHNS with conventional instrumentation to compare the radiological evaluation and functional outcomes of TKA.Materials and methodsThis was a multi-surgeon, prospective, assessor-blinded comparative study of 122 patients undergoing unilateral TKA. We used a stratified randomized sampling method to select 35/48 patients undergoing TKA using a handheld navigation system and 35/74 patients undergoing TKA using conventional instrumentation and divided them into two groups: the HHNS group and (conventional) CONV group. Postoperative radiographic evaluation was based on the tibial and femoral alignment angle, posterior tibial slope, and tibiofemoral angle measured from full-length lower-limb anteroposterior and lateral views of the knee. The Oxford Knee Score (OKS) and Knee Society Score (KSS) with a two-year serial follow-up were used to evaluate functional outcomes.ResultsThe mean tibial alignment angle and posterior tibial slope were 0.78° ± 1.27° and 4.38° ± 0.86°, respectively, in the HHNS cohort and 2.63° ± 1.54° and 2.12° ± 1.82°, respectively, in the CONV group (p < 0.001). There was no significant difference in the femoral alignment angles. The overall alignment using the mean tibiofemoral angle was 179.21° ± 1.82° in the HHNS group and 177.31° ± 2.18° in the CONV group (p = 0.002). There were no significant differences in the KSS and OKS at the two-year follow-up between the groups.ConclusionsThe use of HHNS in TKA significantly increased accuracy in limb and implant alignment, but there was no significant difference in the two-years functional outcomes.

Outcomes of Total Knee Arthroplasty in Patients with Prior Hardware: A Case-Control Study Using Handheld Navigation.

Presence of hardware in juxta-articular location poses challenge during total knee arthroplasty (TKA). When present in distal femur, it precludes the use of an intramedullary femoral jig during TKA often necessitating removal of hardware leading to prolonged surgery, higher risk of complications, and inferior results. We conducted a case-control study to assess the outcome of TKA among patients with post-traumatic arthritis using a handheld navigation system to perform bone cuts allowing retention of hardware in situ. In 15 patients with post-traumatic arthritis and hardware around the knee (Group A), none or part(s) of hardware were removed while performing TKA. These patients were matched to 15 patients who underwent TKA with handheld navigation for primary OA knee (Group B). The perioperative outcomes assessed were operative time, intraoperative blood loss, length of hospital stay, complications, and 30 days reoperation rate. Clinical outcomes were assessed by using Knee Society Score (KSS) and radiological outcomes using mechanical axis and coronal and sagittal component angles. Mean age of patients at surgery were 65.67 years (Group A) and 66.73 years (Group B). Mean operative time and blood loss were significantly higher in Group A as compared with Group B. At the mean follow-up of 34 months, KSS significantly improved in both the groups. However, there was no statistically significant difference in the clinical and radiological outcomes between the two groups. One patient in Group A developed wound dehiscence and had to undergo debridement and flap coverage within 30 days. The use of navigation helps surgeons in gaining proper limb alignment and implant positioning without complete removal of hardware.

A study on radiological outcomes of accelerometer based hand held navigation system in total knee arthroplasty

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; The goal of obtaining more accurate component alignment in total knee arthroplasty (TKA) has led to the development of techniques like portable accelerometer-based handheld navigation system, computer assisted system, patient specific instrumentation. Among which hand held navigation has showed promising results for achieving accurate resection and alignment and only few studies were done to assess radiological outcome or the effective component alignment using portable accelerometer-based hand held navigation system in TKA.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; TKA using portable accelerometer-based hand held navigation system (Smith and Nephew- knee align) was done on 25 knees with primary osteoarthritis. Preoperative and post-operative mechanical axis and component alignments were measured using hip-to-ankle radiographs.&lt;strong&gt;&lt;/strong&gt;&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; Among the femoral components, 92.0% were placed within 90°±2° to the femoral mechanical axis in the coronal and 96.0% of the tibial components were placed within 90°±2° to the mechanical axis in the coronal plane, 94.3% of the TKAs had an overall lower extremity alignment within 3° of neutral to the mechanical axis, based on postoperative hip-to-ankle radiographs.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; The degree of accuracy in positioning the femoral and tibial component in TKA using portable accelerometer-based hand held navigation system (knee align) is very much promising and is an effective intraoperative tool for reducing the proportion of outliers for component placement and thus decreasing the chances of instability and early wear and tear of the components in TKA.&lt;/p&gt;

Current Role of Computer Navigation in Total Knee Arthroplasty

BackgroundComputer-assisted surgical (CAS) navigation has been developed with the aim of improving the accuracy and precision of total knee arthroplasty (TKA) component positioning and therefore overall limb alignment. The historical goal of knee arthroplasty has been to restore the mechanical alignment of the lower limb by aligning the femoral and tibial components perpendicular to the mechanical axis of the femur and tibia. Despite over 4 decades of TKA component development and nearly 2 decades of interest in CAS, the fundamental question remains; does the alignment goal and/or the method of achieving that goal affect the outcome of the TKA in terms of patient-reported outcome measures and/or overall survivorship? The quest for reliable and reproducible achievement of the intraoperative alignment goal has been the primary motivator for the introduction, development, and refinement of CAS navigation. Numerous proprietary systems now exist, and rapid technological advancements in computer processing power are stimulating further development of robotic surgical systems. Three categories of CAS can be defined: image-based large-console navigation; imageless large-console navigation, and more recently, accelerometer-based handheld navigation systems have been developed. ConclusionA review of the current literature demonstrates that there are enough well-designed studies to conclude that both large-console CAS and handheld navigation systems improve the accuracy and precision of component alignment in TKA. However, missing from the evidence base, other than the subgroup analysis provided by the Australian Orthopaedic Association National Joint Replacement Registry, are any conclusive demonstrations of a clinical superiority in terms of improved patient-reported outcome measures and/or decreased cumulative revision rates in the long term. Few authors would argue that accuracy of alignment is a goal to ignore; therefore, in the absence of clinical evidence, many of the arguments against the use of large-console CAS navigation center on the prohibitive cost of the systems. The utilization of low-cost, handheld CAS navigation systems may therefore bridge this important gap, and over time, further clinical evidence may emerge.

The accuracy of a hand-held navigation system in total knee arthroplasty.

This study aims to evaluate the effectiveness of a new hand-held navigation system. The authors of this study hypothesize that this navigation system will improve overall lower limb alignment and implant placement without causing a delay in surgery. Two hundred consecutive patients diagnosed with tricompartmental osteoarthritis and underwent total knee arthroplasty by a senior surgeon were included in this study. One hundred patients underwent TKA using the hand-held navigation system, while the other 100 patients underwent TKA using the conventional technique. The primary outcomes of this study were the overall alignment of the lower limb and the position of the components. This was determined radiologically using the: (1) Hip-Knee-Ankle angle (HKA) for lower limb alignment; (2) Coronal Femoral-Component angle (CFA); and (3) Coronal Tibia-Component angle (CTA) for component position. Normal alignment was taken as 180°±3° for the HKA and 90°±3° for both the CFA and CTA. For the CFA, the proportion of outliers was 7 and 17% in the hand-held navigation and conventional group, respectively (p=0.030). For the HKA and CTA, there was no difference in the proportion of outliers between the two groups. The duration of surgery was 73±9min and 87±15min in the hand-held navigation and conventional group, respectively (p<0.001). This hand-held navigation system is an effective intraoperative tool for reducing the proportion of outliers for femoral implant placement as well as the duration of surgery. The authors conclude that it can be considered for use to check femoral implant placement intra-operatively. III.

Accuracy of a hand-held surgical navigation system for tibial resection in total knee arthroplasty.

Accuracy of total knee arthroplasty (TKA) implant placement and overall limb are important goals of TKA technique. The accuracy and ease of use of an accelerometer-based hand-held navigation system for tibial resection during TKA was examined in 90 patients. Preoperative goals for sagittal alignment, navigation system assembly time, resection time, and tourniquet time were evaluated. Coronal and sagittal alignment was measured postoperatively. The average coronal tibial component alignment was 0.43° valgus; 6.7% of patients had tibial coronal alignment outside of ±3° varus/valgus. The difference between the intraoperative goal and radiographically measured posterior tibial slope was 0.5°. The average time to completion of the tibial cut was 4.6 minutes. The accelerometer-based hand-held navigation system was accurate for tibial coronal and sagittal alignment during TKA, with no additional surgical time compared with conventional instrumentation.

Two-Step Calibration Methods for Miniature Inertial and Magnetic Sensor Units

Low-cost inertial/magnetic sensor units have been extensively used to determine sensor attitude information for a wide variety of applications, ranging from virtual reality, underwater vehicles, handheld navigation systems, to biomotion analysis and biomedical applications. In order to achieve precise attitude reconstruction, appropriate sensor calibration procedures must be performed in advance to process sensor readings properly. In this paper, we are aiming to calibrate different error parameters, such as sensor sensitivity/scale factor error, offset/bias error, nonorthogonality error, mounting error, and also soft iron and hard iron errors for magnetometers. Instead of estimating all of these parameters individually, these errors are combined together as the combined bias and transformation matrix. Two-step approaches are proposed to determine the combined bias and transformation matrix separately. For the accelerometer and magnetometer, the combined bias is determined by finding an optimal ellipsoid that can best fit the sensor readings, and the transformation matrix is then derived through a two-step iterative algorithm by exploring the intrinsic relationship among sensor readings. For the gyroscope, the combined bias can be easily determined by placing the sensor node stationary. For the transformation matrix estimation, the intrinsic relationship among gyroscope readings is explored again, and an unscented Kalman filter is employed to determine such matrix. The calibration methods are then applied to our sensor nodes, and the good performance of the orientation estimation has illustrated the effectiveness of the proposed sensor calibration methods.