Accelerometer-based 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.

Femoral prosthesis alignment of augmented reality-assisted versus accelerometer-based navigation in total knee arthroplasty: A noninferiority analysis

IntroductionThe purpose of this study was to examine the comparative precision of the augmented reality (AR)-assisted navigation system and the accelerometer-based navigation system in total knee arthroplasty (TKA). Materials and methodsWe performed noninferiority analysis in a retrospective cohort. The coronal alignment of femoral prosthesis was compared between 109 TKAs performed using the AR-assisted navigation system and 118 TKAs performed using the accelerometer-based navigation system. All femoral prostheses were planned to be positioned perpendicular to the mechanical axis of the femur. The primary outcome was the success rate of coronal alignment of the femoral prosthesis defined as alignment error relative to neutral alignment <3°. We calculated the noninferiority margin as 7%-points using the 95%–95 % method and also confirmed the validity of the noninferiority margin using the fixed margin method. Noninferiority would be shown if the lower boundary of the 95 % confidence interval (CI) for the between-group difference in percentage of the success rate was not less than 0.93 (i.e., 1.00 − 0.07). ResultsTreatment success was achieved in 104 of 109 patients (95.4 %) in the AR-assisted navigation group and 110 of 118 (93.2 %) in the accelerometer-based navigation group. The risk ratio of success between the AR-assisted navigation group versus accelerometer-based navigation group was 1.02 (95 % CI, 0.96 to 1.09): the CIs did not include the noninferiority margin of 0.93. ConclusionThe AR-assisted navigation system was noninferior to the accelerometer-based navigation system in terms of coronal alignment of the femoral prosthesis in TKA.

Combined Anteversion Technique for Total Hip Arthroplasty With Handheld Accelerometer-Based Navigation System.

IV (technical note).

Accuracy comparison of cup positioning during total hip arthroplasty using Hip Align and AR-Hip in the supine position.

The aim of this study is to compare the accuracy of acetabular cup positioning between the accelerometer-based navigation system and the augmented reality-based navigation system during THA in the supine position. This retrospective study included 66 patients (70 hips) who underwent THA using two types of portable navigation system, Hip Align or AR-Hip, in the spine position. The absolute difference between the intraoperative navigation record and postoperative measurement using computed tomography data was evaluated. Preoperative clinical factors that decreased the accuracy of cup positioning by ≥ 3° were analyzed via multiple logistic regression analyses. The average absolute error of inclination was 2.8 ± 2.6° in Hip Align and 2.7 ± 1.8° in AR-Hip, and absolute anteversion error was 2.5 ± 2.0° in Hip Align and 2.6 ± 2.2° in AR-Hip, and there was no significantly different between the two navigation systems. There was a significant association between the absolute measurement error (≥ 3°) of cup inclination and patients' BMI in the Hip Align group [odds ratio (OR) 1.350; 95% confidence interval (CI) 1.035-1.760; p = 0.027], but not in the AR-Hip group. The accuracy of the acetabular cup positioning between the Hip Align and AR-Hip showed no difference during THA in the spine position. The high BMI could have negative influence on the accuracy of cup positioning in THA using Hip Align, thus AR-Hip could be designable for obesity patients.

Does the accelerometer-based navigation system reduce blood loss and transfusion in one-stage sequential bilateral total knee arthroplasty? A randomized double-blind controlled trial

BackgroundTotal knee arthroplasty (TKA) is associated with significant blood loss and postoperative transfusion. The accelerometer-based navigation (ABN) system guides the bone cutting plane without breaching the intramedullary canal, which may reduce bleeding. This study aimed to investigate blood loss and transfusion compared between the ABN system and the conventional procedure in patients undergoing one-stage sequential bilateral TKA (SBTKA).MethodsA total of 66 patients scheduled for SBTKA were randomly allocated to either the ABN or conventional group. Postoperative hematocrit (Hct) level, drainage blood loss, transfusion rate, and amount of packed red cell transfusion were collected. Total red blood cell (RBC) loss was then calculated for the primary outcome.ResultsThe mean calculated total RBC loss in the ABN and conventional group was 669.7 and 630.0 mL, respectively (p = 0.572). There was no significant difference between groups for other evaluated outcome parameters, including postoperative Hct level, drainage blood loss, or packed red cell transfusion volume. All patients in the conventional group required postoperative blood transfusion while 96.8% of patients in the ABN group were transfused.ConclusionsThe total RBC loss and volume of packed red cells transfusion were not significant difference between interventions, which suggest no benefit of the ABN system in reducing blood loss and transfusion in patients undergoing SBTKA.Trial registrationThe protocol of this study was registered in the Thai Clinical Trials Registry database no. TCTR20201126002 on 26/11/2020.

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.

Accuracy of Accelerometer-Based Navigation System Perseus for the Tibial Cut in Total Knee Arthroplasty: No Superiority Compared to Mechanical Instrumentation in Current Practice

Knee alignment after total knee arthroplasty (TKA) is essential for implant survival. Several studies on accelerometer-based navigation systems have given controversial results, with or without improvement in knee alignment. The aim was to evaluate the accuracy of an accelerometer-based navigation system for tibial resection during total knee arthroplasty. Twenty TKAs performed with an accelerometer-based navigation system were included in this prospective–comparative study. They were matched (on age, body mass index, and preoperative mechanical axis of the lower limb) in a 2:1 ratio with TKA performed with a conventional technique. The objective of this study was to determine the accuracy of the Perseus System for making the tibial cut on TKA. The primary endpoint was the tibial mechanical angle (TMA) measured on radiographic images at two months postoperatively. Secondary endpoints were the tibial slope and the mechanical axis of the lower limb (HKA angle, Hip-Knee-Ankle). The mean TMA in the accelerometer group was 87.6 ± 2.1° versus 89.1 ± 1.6° in the control group (p &lt; 0.01). The tibial slope in the accelerometer group was 90.0 ± 1.9° versus 89.9 ± 1.3° in the control group (not significant). The mean HKA was 177.7 ± 1.8° in the accelerometer group and 177.5 ± 2.2° in the control group (not significant). This accelerometer-based navigation system during TKA did not improve the accuracy of the tibial cut compared to the conventional technique, but it restored the tibial slope.

Comparison of navigation systems for total knee arthroplasty: A systematic review and meta-analysis.

Component alignment is a crucial factor affecting the clinical outcome of total knee arthroplasty (TKA). Accelerometer-based navigation (ABN) systems were developed to improve the accuracy of alignment during surgery. This study aimed to compare differences in component alignment, clinical outcomes, and surgical duration when using conventional instrumentation (CONI), ABN, and computer navigation (CN) systems. A comprehensive literature search was carried out using the Web of Science, Embase, PubMed, and Cochrane databases. Articles that met the eligibility criteria were included in the study. Meta-analyses were performed using the Cochrane Collaboration Review Manager based on Cochrane Review Method. The variables used for the analyses were postoperative clinical outcome (PCO), surgical duration, and component alignment, including the hip-knee-ankle (HKA) angle, coronal femoral angle (CFA), coronal tibial angle (CTA), sagittal femoral angle (SFA), sagittal tibial angle (STA), and the outliers for the mentioned angles. The mean difference (MD) was calculated to determine the difference between the surgical techniques for continuous variables and the odds ratio (OR) was used for the dichotomous outcomes. The meta-analysis of the CONI and ABN system included 18 studies involving 2,070 TKA procedures, while the comparison of the ABN and CN systems included 5 studies involving 478 TKA procedures. The results showed that the ABN system provided more accurate component alignment for HKA, CFA, CTA, and SFA and produced fewer outliers for HKA, CFA, CTA, and STA. However, while the ABN system also required a significantly longer surgical time than the CONI approach, there was no statistical difference in PCO for the two systems. For the ABN and CN systems, there was no statistical difference in all variables except for the ABN system having a significantly shorter surgical duration. There was no significant difference in the accuracy of component alignment between the ABN and CN systems, but the ABN approach had a shorter surgical duration and at lower cost. The ABN system also significantly improved the accuracy of component alignment when compared to the CONI approach, although the surgery was longer. However, there was no significant difference in PCO between the CONI, ABN, and CN systems.

Accuracy of a novel accelerometer-based navigation (Naviswiss) for total hip arthroplasty in the supine position

BackgroundThis study aimed to determine the accuracy of acetabular cup insertion using a novel accelerometer-based navigation system in total hip arthroplasty (THA).MethodsA single-surgeon study was conducted in which 62 prospective patients with navigation and 42 retrospective patients without navigation in a supine position were compared. Absolute values for errors of radiographic inclination and anteversion were calculated. Navigation error was also calculated. Factors that affected absolute value of navigation error in cup alignment were determined.ResultsIn the navigation group, mean absolute errors for radiographic inclination and anteversion were 4.1° and 4.3°, respectively. In the control group, mean absolute errors were 6.6° in inclination (p < 0.01) and 5.9° in anteversion (p = 0.04). Mean absolute values of navigation error were 2.8° in inclination and 2.8°in anteversion. Factors affecting navigation errors were not found.ConclusionThis novel accelerometer-based navigation system significantly increased the accuracy of cup placement during THA in the supine position.

Accelerometer-Based Navigation versus Conventional Total Knee Arthroplasty for Posttraumatic Knee Osteoarthritis.

Posttraumatic osteoarthritis (PTOA) frequently comprises femoral or tibial deformity, which makes it difficult to perform total knee arthroplasty (TKA). Accelerometer-based navigation (ABN) could be effective in restoring a neutral mechanical axis (MA) in TKA, but a limited number of studies have been reported in association with PTOA. Therefore, we aimed to compare the lower limb MA between ABN-assisted TKA (ABN-TKA) and conventional TKA in patients with PTOA. We conducted a retrospective analysis of 28 PTOA patients who underwent TKA using a conventional system (cTKA group, n = 16) and the ABN system (iTKA group, n = 12). Standing long-leg radiographs were assessed for MA and prosthesis alignment as primary outcomes. A postoperative MA deviating beyond ± 3° was defined as an outlier. Perioperative outcomes, Oxford Knee Score (OKS) at 2-year follow-up, and complications were also assessed. The cTKA group and the iTKA group had a mean age of 63.07 years and 65.25 years, respectively. The iTKA group had significantly better MA accuracy when compared to the cTKA group (1.60° ± 2.09° vs. 3.59° ± 1.34°, p = 0.01). The iTKA group showed significantly less MA outlier than the cTKA group (78.6% vs. 25.0%, p = 0.02). The prosthesis alignment and OKS were comparable between the groups. There were 2 periprosthetic joint infections in the cTKA group and 1 periprosthetic fracture of the distal femur in the iTKA group. For PTOA of the knee, both conventional TKA and ABN-TKA significantly improved the postoperative mechanical alignment and functional outcomes. The ABN-TKA seemed to offer higher accuracy and less MA outlier when compared to conventional TKA, and thus ABN could be a good alternative option.

Can accuracy with the iASSIST navigation be confirmed by assessment? A multi-center prospective randomized controlled trial with independent three-dimensional image assessment

BackgroundiASSIST is one of the novel accelerometer-based navigation systems for total knee arthroplasty (TKA). Although the accuracy of iASSIST compared with conventional instruments has been reported, such evaluations were performed on two-dimensional (2D) images (X-rays). This multi-center prospective randomized controlled trial aimed to assess component positioning between TKA with and without iASSIST by 3D image assessment, and to clarify whether the iASSIST provides any benefit with regard to alignment accuracy. MethodsEighty-three knees with primary knee osteoarthritis were enrolled in this study. iASSIST was used for distal femoral and proximal tibial resection in 42 knees (iA group) and a conventional guide was used in 41 knees (CONV group). At 6 months postoperatively, component alignment was evaluated with 3D images by the independent orthopaedic surgeons, and surgical parameters, range of motion and clinical outcomes were examined. ResultsThe rate of knees who have the alignment within 3° of neutral compared with the iA group and CONV group were 92.9% (39/42) vs. 87.8% (36/41) for femur and 76.2% (32/42) vs. 56.1% (23/41) for tibia in the coronal plane, respectively, whereas in the sagittal plane, the rate was 85.7% (36/42) vs. 58.5% (24/41) for femur and 83.3% (35/42) vs. 78.0% (32/41) for tibia, respectively. Compared with the CONV group, the iA group had a significantly improved femoral alignment in the sagittal plane (P = 0.006). There were no clinical or patient-reported differences at 6 months postoperatively. ConclusionsThe iASSIST provides technically high accuracy in femoral resection at TKA compared with a conventional procedure.

The accelerometer-based navigation system demonstrated superior radiological outcomes in restoring mechanical alignment and component sagittal positioning in total knee arthroplasty

BackgroundThis study aimed to determine whether the accelerometer-based navigation (ABN) could improve the accuracy of restoring mechanical axis (MA), component positioning, and clinical outcomes compared to conventional (CON) total knee arthroplasty (TKA).MethodsA total of 301 consecutive patients (ABN: 27, CON: 274) were included. A 1:4 propensity score matching (PSM) was performed between the two groups according to preoperative demographic and clinical parameters. The postoperative MA, femoral coronal angle (FCA), femoral sagittal angle (FSA), tibial coronal angle (TCA) and tibial sagittal angle (TSA) were compared. Absolute deviations of aforementioned angles were calculated as the absolute value of difference between the exact and ideal value and defined as norms if within 3°, otherwise regarded as outliers. Additional clinical parameters, including the Knee Society knee and function scores (KSKS and KSFS) and range of motion (ROM), were assessed at final follow-up (FU) (mean FU was 21.88 and 21.56 months respectively for ABN and CON group). A secondary subgroup analysis and comparison on clinical outcomes were conducted between norms and outliers in different radiological parameters.ResultsA total of 98 patients/102 knees were analyzed after the PSM (ABN: 21 patients/24 knees, CON: 77 patients/78 knees). In the ABN group, the mean MA, FCA and TSA were significantly improved (p = 0.019, 0.006, < 0.001, respectively). Proportions of TKAs within a ± 3°deviation were significantly improved in all the postoperative radiological variables except for TCA (p = 0.003, 0.021, 0.042, 0.013, respectively for MA, FCA, FSA, and TSA). The absolute deviations of FSA and TSA were also significantly lower in the ABN group (p = 0.020, 0.048, respectively). No significant differences were found in either mean value, absolute deviation or outlier ratio of TCA between two groups. On clinical outcomes, there were no significant differences between two groups, although KSKS, KSFS and ROM (p < 0.01, respectively) dramatically improved compared to baseline. The subgroup analysis also demonstrated no statistical difference on clinical outcomes between the outliers and norms in varied radiological parameters.ConclusionsThe ABN could improve the accuracy and precision of mechanical alignment and component positioning without significant improvement of clinical outcomes. Further high quality studies with long term FU are warranted to comprehensively evaluate the value of the ABN.

Accuracy of a portable accelerometer-based navigation system for cup placement and intraoperative leg length measurement in total hip arthroplasty: a cross-sectional study

BackgroundComplications after total hip arthroplasty (THA) are frequently the consequence of malpositioned components or leg length discrepancy after surgery. Recently, a new version of a portable, accelerometer-based hip navigation system (New HipAlign) was made available with a change in the method of measuring cup abduction and the addition of a leg length measurement function. The purposes of this study were to investigate cup positioning and to examine the accuracy of leg length measurement with New HipAlign.MethodsCups were implanted and intraoperative leg length change was measured using New HipAlign in 60 THAs through a posterior approach in the lateral decubitus position. The cup position and radiographic leg length change were determined postoperatively on pelvic radiograph and computed tomography scans. We previously compared cup positioning with a previous version of a portable, accelerometer-based hip navigation system (Previous HipAlign) and conventional surgical techniques. Cup positioning in this study was compared with the results of out previous study using Previous HipAlign.ResultsThe mean cup abduction of 40.3° ± 4.9° (range, 26° to 53°) and the mean cup anteversion of 15.8° ± 5.6° (range, 6.7° to 29.5°) were found. The deviation of the postoperative measured angles from the target cup position was 3.7° ± 3.3° for cup abduction and 5.9° ± 3.6° for cup anteversion. 56/60 of the cups were inside the Lewinnek safe zone. Compared with our previous study using Previous HipAlign, there were no significant differences with regard to cup abduction, cup anteversion, the deviation from the target cup position for cup abduction, the value of deviation for cup anteversion, and the number of cups inside the Lewinnek safe zone (P = 0.218, 0.334, 0.651, 0.797, 0.592). The mean difference between the intraoperative and radiographic leg length changes was + 0.8 ± 3.4 mm. There was significant correlation between the intraoperative and radiographic leg length changes (r = 0.804, P = 0.000).ConclusionsUse of New HipAlign allowed for accurate cup placement and reliable leg length measurement during THA.Trial registrationClinical trial is defined as ‘any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcome’ by the World Health Organization (WHO). Because this study is not a clinical trial, trial registration is not needed.

Effects of body mass index and range of motion on intraoperative change in pelvic tilt during total hip arthroplasty using the direct anterior approach

BackgroundIntraoperative pelvic tilt changes that occurs during total hip arthroplasty (THA) in the supine position affects cup placement and sometimes causes malalignment. The relationship between body mass index (BMI) and pelvic movement has been reported for some procedures, but not the direct anterior approach (DAA). The purpose of this study was to investigate intraoperative pelvic tilt changes that occurs during DAA.MethodsIn this single-center, retrospective study, we reviewed 200 hips that underwent primary THA via DAA in the supine position using an accelerometer-based navigation system. Intraoperative changes in pelvic tilt and axial rotation from the start of surgery to cup placement were assessed using the navigation system. Preoperative clinical factors that increased pelvic tilt and axial rotation toward the surgical side by > 10° were analyzed via univariate and multiple logistic regression analyses.ResultsThe mean pelvic tilt value increased by 7.6° ± 3.8° (95% confidence interval [CI], 7.1–8.2; range, − 5.0–19.0) intraoperatively, and the axial rotation increased by 3.2° ± 2.7° (95% CI, 2.7–3.7; range, − 13.0–12.0). Univariate analysis revealed that the group with increased pelvic tilt showed significantly greater range of abduction and internal rotation, and significantly lower BMI than the group with no increased tilt. Pre-incisional pelvic tilt was significantly greater in the group with increased axial rotation than in the group with no increased rotation. On logistic regression analysis, BMI (odds ratio [OR], 0.889; 95% CI, 0.809–0.977; p = 0.014) and the range of internal rotation (OR, 1.310; 95% CI, 1.002–1.061; p = 0.038) were predictors of large increases in pelvic tilt. No predictors of large increases in axial rotation were identified.ConclusionSignificant forward pelvic tilt was observed in patients with a low BMI values and high ranges of internal rotation via THA using the DAA. Findings indicated that surgeons should pay attention to intraoperative pelvic movements, which may help identify patients with significant pelvic tilt changes.

Usefulness of an accelerometer-based navigation system in bilateral one-stage total knee arthroplasty

BackgroundBilateral one-stage total knee arthroplasty (BTKA) have increased because it provides a number of advantages. Recently, Accelerometer-based navigation (ABN) system which guide the cutting plane without intramedullary disturbance might result in less endothelial and microvascular damage. Therefore, we hypothesized that the ABN may reduce blood loss, reduce postoperative pain, and better restore BTKA alignment compared to conventional instruments.MethodsWe retrospectively compared 44 consecutive patients receiving ABN assisted BTKA (iBTKA) to 57 patients with conventional instruments (cBTKA). Identical pre- and post-operative care was utilized to all patients. The outcome measures assessed were hemoglobin (Hb), calculated blood loss (CBL), blood transfusion, VAS score for pain, morphine consumption, knee flexion angle, and length of stay (LOS). Radiographic assessment included mechanical axis (MA) and component positioning at 3–6 months of follow up.ResultsBoth iBTKA and cTKA groups had equivalent demographic data. Postoperative Hb of the cBTKA group was significantly lower than those in the iBTKA group at 24 h (p = 0.02), but there was no significant difference in drain volume, CBL, and blood transfusion rate. For radiographic measures, the iBTKA group had more accurate MA and component orientation, and had a lower number of outliers than those in the cBTKA group (p ≤ 0.01), except for the sagittal femoral component angle.ConclusionThe ABN assisted BTKA could not reduce blood loss or postoperative pain more than cBTKA, nor improve functional recovery. However, the ABN significantly improved the accuracy of MA and prostheses positioning.Trial registrationThe protocol of this study was registered in the Thai Clinical Trials Registry database No. TCTR20180731001# on 25 July 2018.

Comparison of early results of total knee replacement performed with Zimmer iASSIST versus conventional technique

Background: Zimmer iASSIST knee is an accelerometer-based navigation system with the aim of achieving better alignment in total knee arthroplasty (TKA). We have started using this system since early 2016. This is a retrospective case–control study, which aims to compare the radiological alignment, operation time, and blood loss of TKAs performed using the iASSIST system and those using conventional techniques. Materials and Methods: 42 TKAs using Zimmer iASSIST and 44 TKAs using conventional instrumentation were recruited. The overall coronal alignment and the coronal and sagittal alignment of the femoral and tibial component were compared. For coronal alignment, additional analysis of the absolute deviation from neutral mechanical axis was performed to avoid canceling out of varus/valgus deviation. The number of outliers, operation time, and blood loss in terms of maximal hemoglobin drop were also compared. Results: When comparing the alignment of the iASSIST group with the conventional group, there were no significant differences ( p &gt; 0.05) in the number of outliers, mean coronal alignments, mean deviation from neutral coronal mechanical axis (2.9° vs. 2.9°), and femoral component flexion angle (4.9° vs. 4.7°). The difference in the mean tibial component posterior slope was significant (5.7° vs. 7.1°, p &lt; 0.05). The mean operation time was significantly longer by 13 min ( p &lt; 0.05) in the iASSIST group. There were no significant differences in the mean hemoglobin drop between the two groups. Conclusion: The results demonstrated no significant differences in terms of coronal radiological alignment, femoral flexion angle, outliers, and blood loss between iASSIST and conventional technique. There was a small but statistically significant difference in tibial posterior slope. The iASSIST group needed a longer operation time.

An accelerometer-based navigation system provides acetabular cup orientation accuracy comparable to that of computed tomography-based navigation during total hip arthroplasty in the supine position

BackgroundInadequate acetabular component orientation is associated with postoperative impingement, dislocation, and accelerated polyethylene wear. Computed tomography (CT)-based navigation systems provide accuracy for total hip arthroplasty (THA) but are not available in all facilities. Accelerometer-based navigation systems are inexpensive, but their accuracy remains undetermined. This study compares the accuracy of cup orientation in THA using CT-based and accelerometer-based navigation systems.MethodsThis retrospective study included 35 consecutive patients (11 males, 24 females; mean age, 65 years) who underwent primary cementless THA via an anterolateral approach in the supine position. Both CT-based and accelerometer-based navigation systems were used simultaneously. The accuracy of cup orientation was compared between the two systems using postoperative CT.ResultsThe accuracy of cup inclination was 2.7° ± 2.0° in the CT-based group and 3.3° ± 2.4° in the accelerometer-based group. The accuracy of cup anteversion was 2.8° ± 2.6° in the CT-based group and 3.4° ± 2.2° in the accelerometer-based group. No significant difference was observed in cup inclination (p = 0.29) or cup anteversion (p = 0.34) between CT-based and accelerometer-based navigation.ConclusionsThe accuracy of cup positioning did not differ significantly between CT-based and accelerometer-based navigation systems.

Comparison of the accuracy of CT- and accelerometer-based navigation systems for cup orientation in total hip arthroplasty.

The accuracies of various navigation systems in total hip arthroplasty (THA) have been described; however, the accuracy of cup orientation with an accelerometer-based navigation system has not been reported. The purpose of this study was to compare the accuracies of computed tomography (CT)- and accelerometer-based navigation systems for cup orientation in THA. In this prospective study, 30 patients who underwent cementless THA via anterolateral approach in the lateral decubitus position were analysed. A CT-based navigation system (30 hips) and an accelerometer-based navigation system (30 hips) were used simultaneously. The accuracy of cup orientation (absolute difference between intraoperative vs. postoperative measurements) was compared between the navigation systems using postoperative CT. The accuracy of cup inclination was 3.2 ± 2.4° in the CT-based navigation group and 4.1 ± 3.7° in the accelerometer-based navigation group (p = 0.3035). The accuracy of cup anteversion was 3.0° ± 2.5° in the CT-based navigation group and 6.8° ± 4.8° in the accelerometer-based navigation group. Cup anteversion was significantly more accurate with the CT-based navigation system than with accelerometer-based navigation (p = 0.0009). Multiple regression analysis demonstrated that the malposition in cup anteversion was positively correlated with the change in pelvic tilt and loosening of the reference antenna. Although, these results are only true for this specific accelerometer system, cup positioning was significantly more accurate with the CT-based navigation system than an accelerometer-based navigation in the lateral decubitus position. This is because of considerable discrepancies in the sagittal pelvic tilt, resulting in variability in cup anteversion angle with the use of an accelerometer-based navigation system.

Comparison of iASSIST Navigation System with Conventional Techniques in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis of Radiographic and Clinical Outcomes.

The iASSIST navigation system is a handheld accelerometer‐based navigation system that has been applied in clinical practice in recent five years. This meta‐analysis aimed to compare the radiographic and clinical outcomes of iASSIST navigation with conventional surgical techniques for patients undergoing total knee arthroplasty (TKA) and to compare the surgery time between an iASSIST group and a conventional treatment group. This systematic review and meta‐analysis included all comparative prospective and retrospective studies published in Pubmed, Embase, the Cochrane Central Register of Controlled Trials, the Web of Science and the CNKI databases over the past 20 years. Inclusion criteria were studies that compared the iASSIST navigation system with conventional TKA. The primary outcomes were mechanical axis (MA) and outliers, which means postoperative MA varus or valgus of more than 3°. Secondary outcomes were coronal femoral angle (CFA) and coronal tibial angle (CTA). Knee Society Score (KSS) was used to evaluate functional outcome. The Newcastle–Ottawa Scale (NOS) was used to assess the methodological quality of included studies. Eight studies involving 558 knees were included in this meta‐analysis. Of these, 275 patients used the iASSIST navigation system and 283 used conventional surgical techniques. A total of 5 studies were considered high quality and the other 3 were considered to be of moderate quality. The occurrence of malalignment of >3° in the iASSIST group was 13.3%, compared with 29.04% in the conventional group. Postoperative MA of the iASSIST group was significantly better than that of the conventional group (I 2 = 19%, OR = −0.92, 95% CI = −1.09 to −0.75, P < 0.00001). The iASSIST navigation system provided significantly increased accuracy in the coronal femoral angle (I 2 = 79%, OR = −0.88, 95% CI = −1.21 to −0.54, P < 0.00001) and the coronal tibial angle (I 2 = 34%, OR = 0.39, 95% CI = −0.48 to −0.30, P < 0.00001) compared with conventional techniques. However, the duration of surgery using the iASSIST procedure was longer and there was no significant difference in the short‐term KSS in the iASSIST group compared with the conventional group. We found that when pooling the data of included studies, the number of outliers was fewer in the iASSIST group, and compared with conventional TKA techniques, the iASSIST system significantly improved the accuracy of lower limb alignment but the duration of surgery was prolonged in addition to there being no apparent advantage in terms of short‐term functional score.

Comparison of a novel handheld accelerometer-based navigation system and conventional instrument for performing distal femoral resection in total knee arthroplasty: a randomized controlled trial.

This prospective study aimed to compare the efficacy of a novel, hand-held, accelerometer-based navigation system (i-JOIN knee navigation system) for distal femoral resection in total knee arthroplasty (TKA) with conventional instrument. A multi-center, double-blinded, randomized controlled trial (RCT) was conducted. A total of 79 consecutive patients scheduled for primary TKA were enrolled and divided into navigation group (39 patients) and conventional group (40 patients). Post-operative mechanical and component position were evaluated through full-leg weight bearing X-ray. Pre-operatively and 1 week post-operatively, adverse events were recorded. Intraoperative surgical time and blood loss were also recorded. The mean outlier of 180° neutral mechanical axis was 1.60° (SD 1.11°) in navigation group and 2.30° (SD 2.06°) in conventional group (P=0.0917). Thirty-eight patients (97.4%) in navigation group and 35 patients (87.5%) in conventional group had an alignment which was ≤3°away from the neutral mechanical axis (P=0.2007). α angle between the navigation group and conventional group was not statistically different (89.81° vs. 89.76°, P>0.05), as well as adverse events rate post-operatively. The operative time of navigation group was significantly longer than that of control group (114.54±35.34 vs. 100.33±28.38 min, P=0.0493), whereas the intraoperative blood loss was not significantly different. i-JOIN knee navigation system had equivalent results for distal femoral resection in TKA compared with the conventional technique.