Aims. A significant percentage of patients remain dissatisfied after total knee arthroplasty (TKA). The aim of this study was to determine whether the sequential addition of accelerometer-based navigation for femoral component preparation and sensor-guided ligament balancing improved complication rates, radiological alignment, or patient-reported outcomes (PROMs) compared with a historical control group using conventional instrumentation. Methods. This retrospective cohort study included 371 TKAs performed by a single surgeon sequentially. A historical control group, with the use of intramedullary guides for distal femoral resection and surgeon-guided ligament balancing, was compared with a group using accelerometer-based navigation for distal femoral resection and surgeon-guided balancing (group 1), and one using navigated femoral resection and sensor-guided balancing (group 2). Primary outcome measures were Patient-Reported Outcomes Measurement Information System (PROMIS) and Knee injury and Osteoarthritis Outcome (KOOS) scores measured preoperatively and at six weeks and 12 months postoperatively. The position of the components and the mechanical axis of the limb were measured postoperatively. The postoperative range of motion (ROM), haematocrit change, and complications were also recorded. Results. There were 194 patients in the control group, 103 in group 1, and 74 in group 2. There were no significant differences in baseline demographics between the groups. Patients in group 2 had significantly higher baseline mental health subscores than control and group 1 patients (53.2 vs 50.2 vs 50.2, p = 0.041). There were no significant differences in any PROMs at six weeks or 12 months postoperatively (p > 0.05). There was no difference in the rate of manipulation under anaesthesia (MUA), complication rates, postoperative ROM, or blood loss. There were fewer mechanical axis outliers in groups 1 and 2 (25.2%, 14.9% respectively) versus control (28.4%), but this was not statistically significant (p = 0.10). Conclusion. The sequential addition of navigation of the distal femoral cut and sensor-guided ligament balancing did not improve short-term PROMs, radiological outcomes, or complication rates compared with conventional techniques. The costs of these added technologies may not be justified. Cite this article: Bone Joint J 2020;102-B(6 Supple A):24–30

Aims. Due to the complex anatomy of the pelvis, limb-sparing resections of pelvic tumours achieving adequate surgical margins, can often be difficult. The advent of computer navigation has improved the precision of resection of these lesions, though there is little evidence comparing resection with or without the assistance of navigation. Our aim was to evaluate the efficacy of navigation-assisted surgery for the resection of pelvic bone tumours involving the posterior ilium and sacrum. . Patients and Methods. Using our prospectively updated institutional database, we conducted a retrospective case control study of 21 patients who underwent resection of the posterior ilium and sacrum, for the treatment of a primary sarcoma of bone, between 1987 and 2015. The resection was performed with the assistance of navigation in nine patients and without navigation in 12. We assessed the accuracy of navigation-assisted surgery, as defined by the surgical margin and how this affects the rate of local recurrence, the disease-free survival and the effects on peri-and post-operative morbidity. . Results. The mean age of the patients was 36.4 years (15 to 66). The mean size of the tumour was 10.9 cm. In the navigation-assisted group, the margin was wide in two patients (16.7%), marginal in six (66.7%) and wide-contaminated in one (11.1%) with no intralesional margin. In the non-navigated-assisted group; the margin was wide in two patients (16.7%), marginal in five (41.7%), intralesional in three (25.0%) and wide-contaminated in two (16.7%). Local recurrence occurred in two patients in the navigation-assisted group (22.2%) and six in the non-navigation-assisted group (50.0%). The disease-free survival was significantly better when operated with navigation-assistance (p = 0.048). The blood loss and operating time were less in the navigated-assisted group, as was the risk of a foot drop post-operatively. Conclusion . The introduction of navigation-assisted surgery for the resection of tumours of the posterior ilium and sacrum has increased the safety for the patients and allows for a better oncological outcome. . Cite this article: Bone Joint J 2017;99-B:261–6

Aims. Intraoperative 3D navigation (ION) allows high accuracy to be achieved in spinal surgery, but poor workflow has prevented its widespread uptake. The technical demands on ION when used in patients with adolescent idiopathic scoliosis (AIS) are higher than for other more established indications. Lean principles have been applied to industry and to health care with good effects. While ensuring optimal accuracy of instrumentation and safety, the implementation of ION and its associated productivity was evaluated in this study for AIS surgery in order to enhance the workflow of this technique. The aim was to optimize the use of ION by the application of lean principles in AIS surgery. Methods. A total of 20 consecutive patients with AIS were treated with ION corrective spinal surgery. Both qualitative and quantitative analysis was performed with real-time modifications. Operating time, scan time, dose length product (measure of CT radiation exposure), use of fluoroscopy, the influence of the reference frame, blood loss, and neuromonitoring were assessed. Results. The greatest gains in productivity were in avoiding repeat intraoperative scans (a mean of 248 minutes for patients who had two scans, and a mean 180 minutes for those who had a single scan). Optimizing accuracy was the biggest factor influencing this, which was reliant on incremental changes to the operating setup and technique. Conclusion. The application of lean principles to the introduction of ION for AIS surgery helps assimilate this method into the environment of the operating theatre. Data and stakeholder analysis identified a reproducible technique for using ION for AIS surgery, reducing operating time, and radiation exposure. Cite this article: Bone Joint J. 2020;102-B(1):5–10

Aims. We compared the accuracy, operating time and radiation exposure of the introduction of iliosacral screws using O-arm/Stealth Navigation and standard fluoroscopy. Materials and Methods. Iliosacral screws were introduced percutaneously into the first sacral body (S1) of ten human cadavers, four men and six women. The mean age was 77 years (58 to 85). Screws were introduced using a standard technique into the left side of S1 using C-Arm fluoroscopy and then into the right side using O-Arm/Stealth Navigation. The radiation was measured on the surgeon by dosimeters placed under a lead thyroid shield and apron, on a finger, a hat and on the cadavers. Results. There were no neuroforaminal breaches in either group. The set-up time for the O-Arm was significantly longer than for the C-Arm, while total time for placement of the screws was significantly shorter for the O-Arm than for the C-Arm (p = 0.001). The mean absorbed radiation dose during fluoroscopy was 1063 mRad (432.5 mRad to 4150 mRad). No radiation was detected on the surgeon during fluoroscopy, or when he left the room during the use of the O-Arm. The mean radiation detected on the cadavers was significantly higher in the O-Arm group (2710 mRem standard deviation (. sd. ) 1922) than during fluoroscopy (11.9 mRem . sd 14.8). (p < 0.01). Conclusion. O-Arm/Stealth Navigation allows for faster percutaneous placement of iliosacral screws in a radiation-free environment for surgeons, albeit with the same accuracy and significantly more radiation exposure to cadavers, when compared with standard fluoroscopy. Take home message: Placement of iliosacral screws with O-Arm/Stealth Navigation can be performed safely and effectively. Cite this article: Bone Joint J 2016;98-B:696–702

We compared lower limb coronal alignment measurements obtained pre- and post-operatively with long-leg radiographs and computer navigation in patients undergoing primary total knee replacement (TKR). A series of 185 patients had their pre- and post-implant radiological and computer-navigation system measurements of coronal alignment compared using the Bland-Altman method. The study included 81 men and 104 women with a mean age of 68.5 years (32 to 87) and a mean body mass index of 31.7 kg/m. 2. (19 to 49). Pre-implant Bland–Altman limits of agreement were -9.4° to 8.6° with a repeatability coefficient of 9.0°. The Bland–Altman plot showed a tendency for the radiological measurement to indicate a higher level of pre-operative deformity than the corresponding navigation measurement. Post-implant limits of agreement were -5.0° to 5.4° with a repeatability coefficient of 5.2°. The tendency for valgus knees to have greater deformity on the radiograph was still seen, but was weaker for varus knees. . The alignment seen or measured intra-operatively during TKR is not necessarily the same as the deformity seen on a standing long-leg radiograph either pre- or post-operatively. Further investigation into the effect of weight-bearing and surgical exposure of the joint on the mechanical femorotibial angle is required to enable the most appropriate intra-operative alignment to be selected

INTRODUCTION. In gap balancing technique, we decided the femoral component rotation according to the ligament balance in flexion. Component and limb alignment are important considerations during TKA. Three-dimensional positioning of TKA implants and exact mechanical axis has an effect on implant loosening, polyethylene stresses, and gait. According to the recent report, the navigation system made it possible to achieve aligned implants more than conventional TKA. Hybrid Navigation technique which is our procedure is combination of navigation system and modified gap technique. In other words, exact mechanical axis is gained by navigation system, stable stability of knee joint is gained by modified gap technique. PURPOSE. The purpose of this study is to carry out clinical evaluation and image evaluation of the patients who underwent hybrid navigation technique TKA. METHODS. We performed TKA using the hybrid navigation technique in 100 knees from April 2012 to April 2015. We evaluated hybrid navigation TKA which we were able to follow up more than five years. 33 knees were available for follow up. We investigated the mid-term results of TKA after a mean follow up period of 5 years and 8 months. We evaluated range of motion(ROM), Japan Orthopaedic Association (JOA)score, complications, revision rate as clinical evaluations. And we evaluated radiolucent line(RLL), loosening in X-ray, implantation accuracy in computed tomography(CT) as image evaluations. Surgical technique was that the knees were exposed using a medial parapatellar approach without patella turnover, and the anterior and posterior cruciate ligaments were resected. And next osteotomy distal femur and proximal tibia using CT-free Navigation, step-wise medial soft tissue release was performed to make the rectangular extension joint gap using gap tensor space (off set balancer) at 40 pounds of distraction force. Flextion gap was made at the same distraction force, thereby we determined external rotation angle of femur osteotomy in a patella reduction position. CT of the whole leg was taken preoperation and postoperation the first postoperative week in all cases. RESULTS. In CT evaluation, coronal and sagittal alignments of femoral componet were mean 90.92° and mean flex 3.02°. These alignment of tibial componet were 90.54° and mean posterior slope 3.0°. Outliers(>3°)of coronal aligment were 6% (2 knees)in femoral componet, and 6%(2 knees) in tibial componet. In clinical evaluation, mean preoperative ROM(flex) was 105 degrees which improved 122 degrees at final follow up. Mean preoperative JOA score was 46.3 which improved 85.8 at final follow up. In image evaluation, there were no incidence of component loosening(RLL>2mm). We experienced two complications(1 deep infection and 1 intraoperative fracture), but there were no postoperative fracture and DVT/PE. The revision arte was 3%(1 knee) due to deep infection. DISCUSSION AND CONCLUSION. Mid-term postoperative results has shown a good prognosis. We will not understand that we do not observe long-term results in future, neverthless we believe that this technique should be considered as an alternative means of conducting TKA

Background. Variability in component alignment continues to be a major in total knee arthroplasty(TKA). In the long term, coronal plane malalignment has been associated with an increased risk of loosening, insatability, and wear. Recently portable navigation system(PNS) in TKA have been introduced. The goal of PNS are to improve the accuracy of post operative alignment and eliminate outlier cases. The aim of this study is to evaluate clinical results and quantify the coronal plane alignment between a group of patients who underwent TKA using PNS versus CT-free large-console navigation system. Patients and Method. An unselected consecutive series of ninety-four patients undergoing primary TKA using the cruciate retaining cemented total knee system between April 2012 and August 2015 were studied. Patients were included only if they were deemed to be candidates for a Cruciate retaining TKA. Patients were excluded if they had a flexion contracture greater than 40°, or severe valgus or varus deformity. Forty eight knees was operated a TKA with CT-free large-console navigation system(The OrthoPilot system; Aesculap, Tuttlingen, Germany). Subsequently forty six knees was received a TKA using portable navigation system (KneeAlign2. TM. ). Postoperatively standing AP hip-to-ankle radiographs were obtained, from which the lower extremity mechanical axis, component angle were measured. The alignment goals were a neutral mechanical axis defined as a hip-to-ankle angle of 0°with the femoral and tibial components aligned perpendicular to the mechanical axis. The total operating time were quantified utilising an operating room database. The total operating time between TKAs performed with CT-free navigation system and those performed with portable navigation system was compared in each group. All patients postoperatively was evaluated of clinical results the Japan Orthopedics Association(JOA) Knee scores. Results. The mechanical axis angle in PNS group was 0.8°, while the CT-free navigation system group was 1.6°and there was no statistical significance. The number of outliers for mechanical axis angle was PNS group 39.1%, the large-console navigation group 22.9%, between the two groups there was statistical significance. The operative time in PNS was 130.0 minutes and significantly less compared to the time of the large-console group 150.4 minutes. The JOA Knee score of navigation group was 83.9 points, and the score of PNS group was 81.0 points., there was no statistical significance between the two groups on the clinical score. Conclusion. portable navigation system improved operative time in TKA, this study demonstrates portable navigation system to obtain same angle of overall mechanical axis angle as large-console group navigation system

INTRODUCTION. Soft-tissue balancing of the knee is fundamental to the success of total knee arthroplasty(TKA). Preparing rectangular extension and flexion joint gaps in the most important goal in TKA, because it facilitates functional stability of the knee. In gap balancing technique, we decided the femoral component rotation according to the ligament balance in flexion. Component and limb alignment are important considerations during TKA. Three-dimensional positioning of TKA implants and exact mechanical axis has an effect on implant loosening, polyethylene stresses, and gait. According to the recent reports, the navigation system made it possible to achieve aligned implants more than conventional TKA. Hybrid Navigation technique which is our procedure is combination of navigation system and modified gap technique. In other words, exact mechanical axis is gained by navigation system, stable stability of knee joint is gained by modified gap technique. PURPOSE. The purpose of this study is to carry out clinical evaluation and image assenssment using computed tomography (CT) of the patients who underwent hybrid navigation technique TKA. METHODS. We performed TKA using the hybrid navigation technique in 100 knees from April 2012. Surgical technique was that the knees were exposed using a medial parapatellar approach without patella turnover, and the anterior and posterior cruciate ligaments were resected. And next osteotomy distal femur and proximal tibia using CT-free Navigation, step-wise medial soft tissue release was performed to make the rectangular extension joint gap using gap tensor space(off set balancer) at 40 pounds of distraction force. Flextion gap was made at the same distraction force, thereby we determined external rotation angle of femur osteotomy in a patella reduction position. See Figure 1. CT of the whole leg was taken preoperation and postoperation in all cases. RESULTS. Coronal and sagittal alignments of femoral componet angle were mean 91.05° and mean flex anglewere 2.98°. These alignment of tibial componet angle were 91.08° and mean posterior slope angle were 3.38°. Outliers(>3°)of coronal aligment were 9% in femoral componet, and 8% in tibial componet. Mean operation times(skin incision to skin closure) were 108 minutes. We experienced two complications(1 deep infection and 1 peroneal nerve palsy), but there were no intraoperative fracture, postoperative fracture and DVT/PE. DISCUSSION AND CONCLUSION. 100 patients underwent hybrid navigation TKA which has advantage of both navigation and gap technique. CT assessment of components has shown good results. (outlier>3°femoral component: 9%, tibial component 8%) Short-term postoperative results has shown a good prognosis. We will not understand that we do not observe long-term results in future, neverthless we believe that this technique should be considered as an alternative means of conducting TKA

Navigation in total hip arthroplasty has been shown to improve acetabular positioning and can decrease the incidence of mal-positioned acetabular components. The aim of this study was to assess two surgical guidance systems by comparing intra-operative measurements of acetabular component inclination and anteversion with a post-operative CT scan. We prospectively collected intra-operative navigation data from 102 hips receiving conventional THA or hip resurfacing arthroplasty through either a direct anterior or posterior approach. Two guidance systems were used simultaneously: an inertial navigation system (INS) and optical navigation system (ONS). Acetabular component anteversion and inclination was measured on a post-operative CT. The average age of the patients was 64 years (range: 24-92) and average BMI was 27 kg/m. 2. (range 19-38). 52% had hip surgery through an anterior approach. 98% of the INS measurements and 88% of the ONS measurements were within 10° of the CT measurements. The mean (and standard deviation) of the absolute difference between the post-operative CT and the intra-operative measurements for inclination and anteversion were 3.0° (2.8) and 4.5° (3.2) respectively for the ONS, along with 2.1° (2.3) and 2.4° (2.1) respectively for the INS. There was significantly lower mean absolute difference to CT for the INS when compared to ONS in both anteversion (p<0.001) and inclination (p=0.02). Both types of navigation produced reliable and reproducible acetabular cup positioning. It is important that patient-specific planning and navigation are used together to ensure that surgeons are targeting the optimal acetabular cup position. This assistance with cup positioning can provide benefits over free-hand techniques, especially in patients with an altered acetabular structure or extensive acetabular bone loss. In conclusion, both ONS and INS allowed for adequate acetabular positioning as measured on postoperative CT, and thus provide reliable intraoperative feedback for optimal acetabular component placement

Computer aided orthopaedic surgical (CAOS) technology has been around for over 20 years, and while it appears to provide better outcomes compared to conventional jigs, less than 1% of orthopaedic surgeons in USA have adopted it. This study surveyed the arguments against CAOS usage, highlighting those reasons which may continue to prevent CAOS from becoming truly widely accepted. The survey has identified several concerns with navigation systems. For example, the pin tracts from navigation reference frames cause stress risers that increase the risk of bone fracture and soft tissue/muscle damage. Additionally, infrared trackers take footprint space (as they require line of sight access to the tracking camera), increase risk of infection, and present a potential distraction to the surgical team. With current CAOS systems, even more nstrumentation is needed than with non-navigated surgical systems, and it is arguable that navigation makes surgery more complex, requiring a knowledge of anatomic landmarks, an increased number of tasks prior to and during surgery, and an assortment of different and perhaps unfamiliar instruments. These complexities very likely result in a slow learning curve on current CAOS systems, a learning curve that is mostly not started by the majority of surgeons. Other items of concern are the accuracy of morphed/generated bones in imageless systems (and how these models assume non-deformed anatomy), inaccuracies or distortion of the measurements (operating room lighting interfering with infrared trackers or field deformation of electromagnetic systems due to ferromagnetic instruments at the surgical site) and computer reliability. Considering the high cost (or low cost-effectiveness) of integrating CAOS into arthroplasty, and the lack of enough studies documenting truly better long term clinical results or fewer actual complications, it is evident why navigation is not yet a popular option for TKR. As a result of the critical findings from this study, it is our view that any successful new technique/tool in surgery should make the overall procedure easier, faster, cheaper and better (or at least equally as good) as the current techniques. While robotic surgery seems to be re-emerging, we hypothesize that the next real breakthrough will come from newer more utilitarian light weight small foot print technologies actuated by surgeons themselves, with enhanced computer guidance that will allow them to reduce instrumentation, complexity, and surgical time such as navigated free-hand bone cutting. Alternative navigation technologies (e.g. UWB 3D positioning radar) where line of sight becomes less crucial, image based systems (rather than image free), artificial vision, and smart instrumentation are likely to play a major role in achieving widespread future acceptance of CAOS in TKR

Correct alignment of the leg and positioning of the implant has shown to be an important factor in the successful long term outcome of total knee arthroplasty and navigation systems enable an accuracy of corrections and alignment within intervals of 1 mm or 1 degree. This study is to test if there is any discrepancy in accuracy which was sometimes observed in clinical trials between Orthopilot (Aesculap, Tuttlingen, German) and AxiEM (Medtronic Navigation, CoalCreek, Colo., USA). A synthetic bone model (Sawbones, Pacific Laboratories, Vashon, Washington) including pelvis and leg with mobile joint made up of titanium which does not affect the electromagnetic field was constructed. Mechanical axis was checked by ORTHODOC system (Integrated Surgical System, CA, USA) that is a preplanning system for ROBODOC (ISS, CA, USA) assisted total knee arthroplasty (TKA) and total hip arthroplasty (THA). The CT images were scanned with 1.25 mm or less slice interval. The CT images were converted to 3-dimensional (3D) volume-rendered model in ORTHODOC. Two orthopaedic surgeons measured it ten times independently. For the measurement of mechanical axis using navigation, 4 orthopaedic surgeons (two experts having more than 100 navigation experiences and two residents) registered anatomical landmarks and kinematic center of bone model ten times using Orthopilot as well as AxiEM. After that, one surgeon intentionally registered the wrong anatomical landmarks (10 mm medial and lateral to the center of distal femur, proximal tibial and ankle, and both malleoli) in both navigation system and observed the change of mechanical axis. True mechanical axis was varus 1.25° using Orthodoc, Orthopilot displayed varus 1.10±0.64° and AxiEM did varus 1.78±0.79°. The difference of mechanical axis between two navigations was not observed (P=0.12) and there were no intra and inter-observer variation in statistical analysis (Correlation=0.934, P=0.00). In the case of erroneous identification of the anatomical landmarks, Orthipilot showed much less variation compared to AxiEM. AxiEM altered the mechanical axis more in palpating center of the distal femur and ankle center and Orthopilot did in palpating the center of ankle. Both navigation systems provide high accuracy and reproducibility of mechanical axis of lower limb in experimental condition. But both were affected by the wrong identification of the anatomical landmarks. AxiEM had more variations. So surgeon should pay attention to register the precise anatomical landmarks

Rotational acetabular osteotomy (RAO), one of periacetabular osteotomies, is an effective joint-preserving surgical treatment for developmental dysplasia of the hip. Since 2013, we have been using a CT-based navigation for RAO to perform safe and accurate osteotomy. CT-based navigation allows precise osteotomy during surgery but cannot track the bony fragment after osteotomy. Thus, it is an issue to achieve successful reorientation in accordance with preoperative planning. In this presentation, we introduce a new method to achieve reorientation and evaluate its accuracy. Thirty joints in which CT-based navigated RAO was performed were included in this study. For the first 20 joints, reorientation was confirmed by tracing the lateral aspect of rotated fragment with navigation and checked if it matched with the preoperative planning. For the latter 10 joints, a new method was adopted. Four fiducial points were made on lateral side of the acetabulum in the preoperative 3-dimensional model and intraoperatively, rotation of the osteotomized bone was performed so that the 4 fiducial points match the preoperative plan. To assess the accuracy of position of rotated fragment in each group, preoperative planning and postoperative CT were compared. A total of 24 radial reformat images of postoperative CT were obtained at a half-hour interval following the clockface system around the acetabulum. In every radial image, femoral head coverage of actual postop- and planned were measured to evaluate the accuracy of acetabular fragment repositioning. The 4-fiducial method significantly reduced the reorientation error. Especially in the 12:00 to 1:00 position of the acetabulum, there were significantly fewer errors (p<0.01) and fewer cases with under-correction of the lateral acetabular coverage. With the new method with 4 reference fiducials, reorientation of the acetabulum could be obtained as planned with lesser errors

Introduction. Computer assisted surgery (CAS) systems have been shown to improve alignment accuracy in total knee arthroplasty (TKA), yet concerns regarding increased costs, operative times, pin sites, and the learning curve associated with CAS techniques have limited its widespread acceptance. The purpose of this study was to compare the alignment accuracy of an accelerometer-based, portable navigation device (KneeAlignÒ 2) to a large console, imageless CAS system (AchieveCAS). Our hypothesis is that no significant difference in alignment accuracy will be appreciated between the portable, accelerometer-based system, and the large-console, imageless navigation system. Methods. 62 consecutive patients, and a total of 80 knees, received a posterior cruciate substituting TKA using the Achieve CAS computer navigation system. Subsequently, 65 consecutive patients, and a total of 80 knees, received a posterior cruciate substituting TKA using the KneeAlignÒ 2 to perform both the distal femoral and proximal tibial resections (femoral guide seen in Figure 1, and tibial guide seen in Figure 2). Postoperatively, standing AP hip-to-ankle radiographs were obtained for each patient, from which the lower extremity mechanical axis, tibial component varus/valgus mechanical alignment, and femoral component varus/valgus mechanical alignment were digitally measured. Each measurement was performed by two, blinded independent observers, and interclass correlation for each measurement was calculated. All procedures were performed using a thigh pneumatic tourniquet, and the total tourniquet time for each procedure was recorded. Results. In the KneeAlignÒ 2 cohort, 92.5% of patients had an alignment within 3° of a neutral mechanical axis (vs. 86.3% with AchieveCAS, p<0.01), 96.2% had a tibial component alignment within 2° of perpendicular to the tibial mechanical axis (vs. 97.5% with AchieveCAS, p=0.8), and 94.9% had a femoral component alignment within 2° of perpendicular to the femoral mechanical axis (vs. 92.5% with AchieveCAS, p<0.01). The mean tourniquet time in the KneeAlignÒ 2 cohort was 48.1 + 10.2 minutes, versus 54.1 + 10.5 in the AchieveCAS cohort (p<0.01). The interclass correlation coefficient for measurement of the postoperative tibial alignment was 0.92, for femoral alignment was 0.85, and for overall lower extremity alignment was 0.94. Conclusion. Accelerometer-based, portable navigation can provide the same degree of alignment accuracy as large console, imageless CAS system in TKA, while also decreasing operative times. The KneeAlignÒ 2 successfully combines the benefits and accuracy of large-console, CAS systems, while avoiding the use of extra pin sites, decreasing operative times, and providing a level of familiarity with conventional alignment methods

Total hip arthroplasty (THA) is an effective treatment for symptomatic hip osteoarthritis (OA). While computer-navigation technologies in total knee arthroplasty show survivorship advantages and are widely used, comparable applications within THA show far lower utilisation. Using national registry data, this study compared patient reported outcome measures (PROMs) in patients who underwent THA with and without computer navigation. Data from Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) PROMs program included all primary THA procedures performed for OA up to 31 December 2020. Procedures using the Intellijoint HIP® navigation system were identified and compared to procedures using other computer navigation systems or conventional instrumentation only. Changes in PROM scores between pre-operative and 6-month post-operative time points were analysed using multiple regression model, adjusting for pre-operative score, patient age, gender, ASA score, BMI, surgical approach, and hospital type. There were 65 primary THA procedures that used the Intellijoint HIP® system, 90 procedures used other types of computer navigation, and the remaining 5,284 primary THA procedures used conventional instrumentation. The estimated mean changes in the EuroQol visual analogue scale (EQ VAS) score and Oxford Hip score did not differ significantly when Intellijoint® was compared to conventional instruments (estimated differences of 2.4, 95% CI [-1.7, 6.5], p = 0.245, and −0.5, 95% CI [-2.5, 1.4], p = 0.592, respectively). The proportion of patients who were satisfied with their procedure was also similar when Intellijoint® was compared to conventional instruments (rate ratio 1.06, 95% CI [0.97, 1.16], p = 0.227). The preliminary data demonstrate no significant difference in PROMs when comparing the Intellijoint HIP® THA navigation system with both other navigation systems and conventional instrumentation for primary THAs performed for OA. Level of evidence: III (National registry analysis)

Introduction. Re-revision due to instability and dislocation can occur in up to 1 in 4 cases following revision total hip arthroplasty (THA). Optimal placement of components during revision surgery is thus critical in avoiding re-revision. Computer-assisted navigation has been shown to improve the accuracy and precision of component placement in primary THA; however, its role in revision surgery is less well documented. The purpose of our study was to evaluate the effect of computer-assisted navigation on component placement in revision total hip arthroplasty, as compared with conventional surgery. Methods. To examine the effect of navigation on acetabular component placement in revision THA, we retrospectively reviewed data from a multi-centre cohort of 128 patients having undergone revision THA between March 2017 and January 2019. An imageless computer navigation device (Intellijoint HIP®, Intellijoint Surgical, Kitchener, ON, Canada) was utilized in 69 surgeries and conventional methods were used in 59 surgeries. Acetabular component placement (anteversion, inclination) and the proportion of acetabular components placed in a functional safe zone (40° inclination/20° anteversion) were compared between navigation assisted and conventional THA groups. Results. Mean inclination decreased post-operatively versus baseline in both the navigation (44.9°±12.1° vs. 43.0°±6.8°, p=0.65) and control (45.8°±19.4° vs. 42.8°±7.1°, p=0.08) groups. Mean anteversion increased in both study groups, with a significant increase noted in the navigation group (18.6°±8.5° vs. 21.6°±7.8°, p=0.04) but not in the control group (19.4°±9.6° vs. 21.2°±9.8°, p=0.33). Post-operatively, a greater proportion of acetabular components were within ±10° of a functional target (40° inclination, 20° anteversion) in the navigation group (inclination: 59/67 (88%), anteversion: 56/67 (84%)) than in the control group (49/59 (83%) and 41/59, (69%), respectively). Acetabular component precision in both study groups improved post-operatively versus baseline. Variance in inclination improved significantly in both control (50.6° vs. 112.4°, p=0.002) and navigation (46.2° vs. 141.1°, p<0.001) groups. Anteversion variance worsened in the control group (96.3° vs. 87.6°, p=0.36) but the navigation group showed improvement (61.2° vs. 72.7°, p=0.25). Post-operative variance amongst cup orientations in the navigation group (IN: 46.2°; AV: 61.2°) indicated significantly better precision than that observed in the control group (IN: 50.6°, p=0.36; AV: 96.3°, p=0.04). Discussion. Re-revision is required in up to 25% of revision THA cases, of which 36% are caused by instability. This places a significant burden on the health care system and highlights the importance of accurate component placement. Our data indicate that the use of imageless navigation in revision THA – by minimizing the likelihood of outliers – may contribute to lower rates of re-revision by improving component orientation in revision THA. Conclusion. Utilizing imageless navigation in revision THAs results in more consistent placement of the acetabular component as compared to non-navigated revision surgeries

INTRODUCTION. The restoration of physiological kinematics is one of the goals of a total knee arthroplasty (TKA). Navigation systems have been developed to allow an accurate and precise placement of the implants. But its application to the intraoperative measurement of knee kinematics has not been validated. The hypothesis of this study was that the measurement of the knee axis, femoral rotation, femoral translation with respect to the tibia, and medial and lateral femorotibial gaps during continuous passive knee flexion by the navigation system would be different from that by fluoroscopy taken as reference. MATERIAL – METHODS. Five pairs of knees of preserved specimens were used. The e.Motion FP ® TKA (B-Braun Aesculap, Tuttlingen, Germany) was implanted using the OrthoPilot TKA 4.3 version and Kobe version navigation system (B-Braun Aesculap, Tuttlingen, Germany). Kinematic recording by the navigation system was performed simultaneously with fluoroscopic recording during a continuous passive flexion-extension movement of the prosthetic knee. Kinematic parameters were extracted from the fluoroscopic recordings by image processing using JointTrack Auto ® software (University of Florida, Gainesville, USA). The main criteria were the axis of the knee measured by the angle between the center of the femoral head, the center of the knee and the center of the ankle (HKA), femoral rotation, femoral translation with respect to the tibia, and medial and lateral femorotibial gaps. The data analysis was performed by a Kappa correlation test. The agreement of the measurements was assessed using the intraclass correlation coefficient (ICC) and its 95% confidence interval. RESULTS. The respective CCIs were as follows: HKA angle 0.839 [0.820; 0.856]; femoral translation 0.560 [0.517; 0.600]; femoral rotation 0.652 [0.616; 0.686]; medial femorotibial gap 0.905 [0.894; 0.916]; lateral femorotibial gap 0.767 [0.740; 0.791]. DISCUSSION. Measurements of TKA kinematics by the navigation system and by fluoroscopy were consistent for HKA angle and medial and lateral femorotibial gaps, but not for femoral translation and femoral rotation. These differences can be explained by a methodological bias. At the end of this work, the specific navigation system cannot be considered as a reliable instrument for measuring the kinematics of a TKA

Aims. Navigation devices are designed to improve a surgeon’s accuracy in positioning the acetabular and femoral components in total hip arthroplasty (THA). The purpose of this study was to both evaluate the accuracy of an optical computer-assisted surgery (CAS) navigation system and determine whether preoperative spinopelvic mobility (categorized as hypermobile, normal, or stiff) increased the risk of acetabular component placement error. Methods. A total of 356 patients undergoing primary THA were prospectively enrolled from November 2016 to March 2018. Clinically relevant error using the CAS system was defined as a difference of > 5° between CAS and 3D radiological reconstruction measurements for acetabular component inclination and anteversion. Univariate and multiple logistic regression analyses were conducted to determine whether hypermobile (. Δ. sacral slope(SS). stand-sit. > 30°), or stiff (. ∆. SS. stand-sit. < 10°) spinopelvic mobility contributed to increased error rates. Results. The paired absolute difference between CAS and postoperative imaging measurements was 2.3° (standard deviation (SD) 2.6°) for inclination and 3.1° (SD 4.2°) for anteversion. Using a target zone of 40° (± 10°) (inclination) and 20° (± 10°) (anteversion), postoperative standing radiographs measured 96% of acetabular components within the target zone for both inclination and anteversion. Multiple logistic regression analysis controlling for BMI and sex revealed that hypermobile spinopelvic mobility significantly increased error rates for anteversion (odds ratio (OR) 2.48, p = 0.009) and inclination (OR 2.44, p = 0.016), whereas stiff spinopelvic mobility increased error rates for anteversion (OR 1.97, p = 0.028). There were no dislocations at a minimum three-year follow-up. Conclusion. Despite high reliability in acetabular positioning for inclination in a large patient cohort using an optical CAS system, hypermobile and stiff spinopelvic mobility significantly increased the risk of clinically relevant errors. In patients with abnormal spinopelvic mobility, CAS systems should be adjusted for use to avoid acetabular component misalignment and subsequent risk for long-term dislocation. Cite this article: Bone Jt Open 2022;3(6):475–484

The use of intraoperative navigation and robotic surgery for minimally invasive lumbar fusion has been increasing over the past decade. The aim of this study is to evaluate postoperative clinical outcomes, intraoperative parameters, and accuracy of pedicle screw insertion guided by intraoperative navigation in patients undergoing lumbar interbody fusion for spondylolisthesis. Patients who underwent posterior lumbar fusion interbody using intraoperative 3D navigation since December 2021 were included. Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and Short Form Health Survey-36 (SF-36) were assessed preoperatively and postoperatively at 1, 3, and 6 months. Screw placement accuracy, measured by Gertzbein and Robbins classification, and facet joint infringement, measured by Yson classification, were assessed by intraoperative Cone Beam CT scans performed at the end of instrumentation. Finally, operation time, intraoperative blood loss, hospital stay, and screw insertion time were evaluated. This study involved 50 patients with a mean age of 63.7 years. VAS decreased from 65.8±23 to 20±22 (p<.01). ODI decreased from 35.4%±15 to 11.8%±14 (p<.01). An increase of SF-36 from 51.5±14 to 76±13 (p<.01) was demonstrated. The accuracy of “perfect” and “clinically acceptable” pedicle screw fixation was 89.5% and 98.4%, respectively. Regarding facet violation, 96.8% of the screws were at grade 0. Finally, the average screw insertion time was 4.3±2 min, hospital stay was 4.2±0.8 days, operation time was 205±53 min, and blood loss was 169±107 ml. Finally, a statistically significant correlation of operation time with hospital stay, blood loss and placement time per screw was found. We demonstrated excellent results for accuracy of pedicle screw fixation and violation of facet joints. VAS, ODI and SF-36 showed statistically significant improvements from the control at one month after surgery. Navigation with intraoperative 3D images represents an effective system to improve operative performance in the surgical treatment of spondylolisthesis

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

Problem. Total hip replacement (THA) is among the most common and highest total spend elective operations in the United States. However, up to 7% of patients have 90-day complications after surgery, most frequently joint dislocation that is related to poor acetabular component positioning. These complications lead to patient morbidity and mortality, as well as significant cost to the health system. As such, surgeons and hospitals value navigation technology, but existing solutions including robotics and optical navigation are costly, time-consuming, and complex to learn, resulting in limited uptake globally. Solution. Augmented reality represents a navigation solution that is rapid, accurate, intuitive, easy to learn, and does not require large and costly equipment in the operating room. In addition to providing cutting edge technology to specialty orthopedic centers, augmented reality is a very attractive solution for lower volume and smaller operative settings such as ambulatory surgery centers that cannot justify purchases of large capital equipment navigation systems. Product. HipInsight™ is an augmented reality solution for navigation of the acetabular component in THA. HipInsight is a navigation solution that includes preoperative, cloud based surgical planning based on patient imaging and surgeon preference of implants as well as intraoperative guidance for placement of the acetabular component. Once the patient specific surgical plan is generated on the cloud-based planning system, holograms showing the optimal planned position of the acetabular component are exported in holographic format to a Microsoft HoloLens 2™, which the surgeon wears during placement of the acetabular component in total hip arthroplasty. The pelvis is registered using the HipXpert™ mechanical registration device, which takes 2–3 minutes to dock in the operating room. The surgeon then is able to view the patient's anatomy and optimal placement of the acetabular component under the skin in augmented reality. The surgeon then aligns the real cup impactor with the augmented reality projection of the cup impactor resulting in precise placement of the cup. Timescales. HipInsight was FDA cleared on January 28, 2021 for intraoperative use for placement of the acetabular component in total hip arthroplasty. The first case was performed in February 2021, and the product was launched to a select group of orthopedic surgeons in March 2021. Funding. HipInsight has been self-funded to date, and is beginning to engage in discussions to raise capital for a rapidly scaling commercial launch

Objectives. We evaluated the accuracy of augmented reality (AR)-based navigation assistance through simulation of bone tumours in a pig femur model. Methods. We developed an AR-based navigation system for bone tumour resection, which could be used on a tablet PC. To simulate a bone tumour in the pig femur, a cortical window was made in the diaphysis and bone cement was inserted. A total of 133 pig femurs were used and tumour resection was simulated with AR-assisted resection (164 resection in 82 femurs, half by an orthropaedic oncology expert and half by an orthopaedic resident) and resection with the conventional method (82 resection in 41 femurs). In the conventional group, resection was performed after measuring the distance from the edge of the condyle to the expected resection margin with a ruler as per routine clinical practice. Results. The mean error of 164 resections in 82 femurs in the AR group was 1.71 mm (0 to 6). The mean error of 82 resections in 41 femurs in the conventional resection group was 2.64 mm (0 to 11) (p < 0.05, one-way analysis of variance). The probabilities of a surgeon obtaining a 10 mm surgical margin with a 3 mm tolerance were 90.2% in AR-assisted resections, and 70.7% in conventional resections. Conclusion. We demonstrated that the accuracy of tumour resection was satisfactory with the help of the AR navigation system, with the tumour shown as a virtual template. In addition, this concept made the navigation system simple and available without additional cost or time. Cite this article: H. S. Cho, Y. K. Park, S. Gupta, C. Yoon, I. Han, H-S. Kim, H. Choi, J. Hong. Augmented reality in bone tumour resection: An experimental study. Bone Joint Res 2017;6:137–143

Cup orientation of total hip arthroplasty (THA) is critical for dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. But, substantial error under manual technique has been reported. Therefore, various navigation systems were introduced to reduce outliers. CT based navigation (CTN) was reported to reduce outliers in cup orientation. Recently, a noble technique, fluoroscopy-CT-based navigation (FCTN), has recently been developed using 2D-3D matching technique. Because of much less registration points, FCTN might be friendly to MIS THA and cases with sever bone deformity. Between October 2006 and April 2008, 33 THAs were performed through MIS approach with navigations. We prospectively randomized those into two groups, CTN and FCTN groups. We implanted cementless hemispherical cups in 18 hips using CTN (VectorVision CT Hip 3.1) and in 15 hips using FCTN (VectorVision CT Hip 3.5). For all the patients, volumetric post-operative CT scan was performed to measure 3D cup orientation. using 3D image-processing software (JMM, Japan). The difference from target angles of anteversion was 2.7 ± 2.4 degrees in FCTN group, and 12.1 ± 5.7 degrees in CTN group (p < 0.001). The absolute value of difference from target angles of inclination was 2.7 ± 2.4 degrees in FCTN group, and 6.5 ± 4.5 degrees in CTN group (p = 0.006). FCTN does not need surface registration around acetabulum, which is great advantage to MIS THA. Our study clearly showed that FCTN significantly improved a cup orientation to CTN

Total hip arthroplasty (THA) is an effective treatment for symptomatic hip osteoarthritis (OA). Computer-navigation technologies in total knee arthroplasty show evidence-supported survivorship advantages and are used widely. The aim of this study was to determine the revision outcome of hip commercially available navigation technologies. Data from the Australian Orthopaedic Association National Joint Replacement Registry from January 2016 to December 2020 included all primary THA procedures performed for osteoarthritis (OA). Procedures using the Intellijoint HIP® navigation were identified and compared to procedures inserted using ‘other’ computer navigation systems and to all non-navigated procedures. The cumulative percent revision (CPR) was compared between the three groups using Kaplan-Meier estimates of survivorship and hazard ratios (HR) from Cox proportional hazards models, adjusted for age and gender. A prosthesis specific analysis was also performed. There were 1911 procedures that used the Intellijoint® system, 4081 used ‘other’ computer navigation, and 160,661 were non-navigated. The all-cause 2-year CPR rate for the Intellijoint HIP® system was 1.8% (95% CI 1.2, 2.6), compared to 2.2% (95% CI 1.8, 2.8) for other navigated and 2.2% (95% CI 2.1, 2.3) for non-navigated cases. A prosthesis specific analysis identified the Paragon/Acetabular Shell THAs combined with the Intellijoint HIP® system as having a higher (3.4%) rate of revision than non-navigated THAs (HR = 2.00 (1.01, 4.00), p=0.048). When this outlier combination was excluded, the Intellijoint® system group demonstrated a two-year CPR of 1.3%. There was no statistical difference in the CPR between the three groups before or after excluding Paragon/Acetabular Shell system. The preliminary data presented demonstrate no statistical difference in all cause revision rates when comparing the Intellijoint HIP® THA navigation system with ‘other’ navigation systems and ‘non-navigated’ approaches for primary THAs performed for OA. The current sample size remains too small to permit meaningful subgroup statistical comparisons

Introduction: Femoral neck fractures are common and percutaneous insertion of three cannulated screws is an accepted method of surgical treatment. The accuracy of surgical performance is highly correlated with the cut-out percentages of the screws. The conventional technique relies heavily on fiuoroscopy and could lead to inappropriate implant placement. Further, multiple guidewire passes might prolong the operation time and weaken the cancellous bone. A computer-assisted planning and navigation system based on 2D-fiuoroscopy has been developed for guidewire insertion in order to perform insertion of a guidewire to perform screw insertion. The image acquisition process was supported by a radiation-saving procedure called “Zero-dose C-arm navigation”. The purpose of this experimental study was to compare this technique with conventional C-arm fiuoroscopy with respect to the number of fiuoroscopic images, the number of drilling attempts and operation time. We used two operative settings, with sawbones and with cadavers. For the sawbone study, we also compared the femoral neck and head perforation and the neck-width coverage (the relative area of the femoral neck held by screws). Methods: Three cannulated hip screws were inserted into 12 femoral sawbones simulating femoral neck fractures and into 6 cadaveric femurs guided by the computer-based navigation. We compared them to the conventional fiuoroscopic technique also using 12 femoral sawbones and 6 cadaveric femurs. Results: The computer-assisted technique significantly reduced the amount of intraoperative fiuoroscopy (sawbone study: P< 0.001; cadaver study: P< 0.001) and the number of guidewire passes (sawbone study: P< 0.05; cadaver study: P< 0.05) in the sawbone and the cadaver setting. Operation time was significantly longer (sawbone study: P< 0.001; cadaver study: P< 0.05) in the navigation assisted group also in both settings. In the sawbone study, there was no significant difference in the femoral neck and head perforation, whereas the relative neck area held by the screws was significantly (P< 0.05) larger than that in the conventional group. Discussion: The addition of computer-assisted planning and surgical guidance supported by “Zero-dose C-arm navigation” may be useful for the fixation of femoral neck fractures by cannulated screws as it reduces the amount of intraoperative fiuoroscopy, requires fewer drill tracks and achieves a better neck coverage. Further studies with the goal of reducing the operation time by improving the learning curve are indispensable before integrating this navigation system into the clinical workfiow

Image guided surgery (IGS), or “Navigation,” is now widely used in many areas of surgery including arthroplasty. However, the options for establishing, in real time, the veracity of the navigation information are limited. Manufacturers recommend registering with a “prominent anatomical feature” to confirm accurate navigation is being presented. In their fine print, they warrant the accuracy proximate to the navigation array attached to the body. In multi-level spine surgery where it is most sorely needed, this limits the warrants to the vertebra of reference array attachment. In arthroplasty surgery, the accuracy of the system can be erroneous through technical errors and a delay may occur prior to verification of such innacuracy. In response to this situation surgeons have taken to using K-wires, FaxMax screws and a variety of other “Fiducial Markers”, but these were not specifically designed for this purpose and in many ways are inadequate for the task of verification of navigation accuracy. We have developed a fiducial marker that is designed to address these unmet needs. The Precision Screw is clearly visible on imaging modalities and the central registration point is identifiable at any angle of viewing, with accuracy of fractions of a millimeter. It does not interfere with surgery, being low profile and securely fixed to bone. Finally, in use, it is secure in capturing the navigation probe so that the surgeon does not need to focus on keeping the probe located while reviewing the navigation data. We believe these features make this a useful and worthwhile addition to IGS

We report our experience of using a computer navigation system to aid resection of malignant musculoskeletal tumours of the pelvis and limbs and, where appropriate, their subsequent reconstruction. We also highlight circumstances in which navigation should be used with caution. We resected a musculoskeletal tumour from 18 patients (15 male, three female, mean age of 30 years (13 to 75) using commercially available computer navigation software (Orthomap 3D) and assessed its impact on the accuracy of our surgery. Of nine pelvic tumours, three had a biological reconstruction with extracorporeal irradiation, four underwent endoprosthetic replacement (EPR) and two required no bony reconstruction. There were eight tumours of the bones of the limbs. Four diaphyseal tumours underwent biological reconstruction. Two patients with a sarcoma of the proximal femur and two with a sarcoma of the proximal humerus underwent extra-articular resection and, where appropriate, EPR. One soft-tissue sarcoma of the adductor compartment which involved the femur was resected and reconstructed using an EPR. Computer navigation was used to aid reconstruction in eight patients. Histological examination of the resected specimens revealed tumour-free margins in all patients. Post-operative radiographs and CT showed that the resection and reconstruction had been carried out as planned in all patients where navigation was used. In two patients, computer navigation had to be abandoned and the operation was completed under CT and radiological control. The use of computer navigation in musculoskeletal oncology allows accurate identification of the local anatomy and can define the extent of the tumour and proposed resection margins. Furthermore, it helps in reconstruction of limb length, rotation and overall alignment after resection of an appendicular tumour. . Cite this article: Bone Joint J 2015;97-B:258–64

Acetabular implant position is important for the stability, function, and long-term wear properties of a total hip arthroplasty (THA). Prior studies of acetabular implant positioning have demonstrated a high percentage of outliers, even in experienced hip surgeons, when conventional instruments are used. Computer navigation is an attractive tool for use in (THA, as it has been shown to improve the precision of acetabular component placement and reduce the incidence of outliers. However, computer navigation with imageless, large-console systems is costly and often interrupts the surgeon's workflow, and thus, has not been widely adopted. Another method to improve acetabular component positioning during THA is the use of fluoroscopy with the direct anterior approach. Studies have demonstrated that the supine position of the patient during surgery facilitates the use of fluoroscopic guidance, thus improving acetabular component position. A handheld, accelerometer based navigation unit for use in total hip replacement has recently become available to assist the surgeon in positioning the acetabular component during anterior approach THA, potentially reducing the need for intraoperative fluoroscopic studies. We sought to compare the radiographic results of direct anterior THA performed with conventional instrumentation vs. handheld navigation to determine the accuracy of the navigation unit, and to see whether or not there was a reduction in the fluoroscopic time used during surgery. Furthermore, we timed the use of the navigation unit to see whether or not it required a substantial addition to surgical time. Our results demonstrate that a handheld navigation unit used during anterior approach THA had no difference with regard to acetabular cup positioning when compared to fluoroscopically assisted THA, but led to a reduction in the use of intraoperative fluoroscopy time

Imageless computer navigation systems in total hip arthroplasty (THA) improve acetabular cup position, thereby reducing the risk of revision surgery for all causes as well as dislocation. We aimed to evaluate the registration accuracy of 3 alternate registration planes. A prospective, observational study was conducted with 45 THA in the supine position using two imageless navigation systems and 3 registration planes. Patient position was registered sequentially using an optical system (Stryker OrthoMap) and an inertial sensor-based system (Navbit Sprint) with 3 planes of reference: (Plane 1) an anatomical plane using the anterior superior iliac spines (ASISs) and the pubic symphysis; (Plane 2) a functional plane parallel to the line between the ASISs and the table plane; and, (Plane 3) a functional plane that was perpendicular to the gravity vector and aligned with the longitudinal axis of the patient. The 3 measurements of acetabular cup inclination and anteversion were compared with the measurements from postoperative computed tomography (CT) scans. For inclination, the mean absolute error was significantly lower for Plane 3 (1.80°) than for Plane 2 (2.74°), p = .038 and was lower for both functional planes than for the anatomical plane (3.75°), p < .001. For anteversion, the mean absolute error was significantly lower for Plane 3 (2.00°) than for Plane 2 (3.69°), p = .004 and was lower for both functional planes than for the anatomical plane (8.58°), p < .001. Patient registration using functional planes more accurately measured the acetabular cup position than registration using anatomic planes

Acetabular implant position is important for the stability, function, and long-term wear properties of a total hip arthroplasty (THA). Prior studies of acetabular implant positioning have demonstrated a high percentage of outliers, even in experienced hip surgeons, when conventional instruments are used. Computer navigation is an attractive tool for use in THA, as it has been shown to improve the precision of acetabular component placement and reduce the incidence of outliers. However, computer navigation with imageless, large-console systems is costly and often interrupts the surgeon's workflow, and thus, has not been widely adopted. Another method to improve acetabular component positioning during THA is the use of fluoroscopy with the direct anterior approach. Studies have demonstrated that the supine position of the patient during surgery facilitates the use of fluoroscopic guidance, thus improving acetabular component position. A handheld, accelerometer-based navigation unit for use in total hip replacement has recently become available to assist the surgeon in positioning the acetabular component during anterior approach THA, potentially reducing the need for intra-operative fluoroscopic studies. We sought to compare the radiographic results of direct anterior THA performed with conventional instrumentation vs. handheld navigation to determine the accuracy of the navigation unit, and to see whether or not there was a reduction in the fluoroscopic time used during surgery. Furthermore, we timed the use of the navigation unit to see whether or not it required a substantial addition to surgical time. Our results demonstrate that a handheld navigation unit used during anterior approach THA had no difference with regard to acetabular cup positioning when compared to fluoroscopically assisted THA, but led to a reduction in the use of intra-operative fluoroscopy time

Intra-operative 3-D fluoroscopy has limitations, including low resolution images, little soft tissue information and small working volume. Fusion of 3D data sets (MRI/ CT) had been developed in pre-operative planners. We employed the same principle and developed a new technique of navigation with fused images of pre-operative MRI/CT and intra-operative 3D fluoroscopy. Pre-op CT/MRI in DICOM was imported to the Stryker Leibinger Spine 3-D and segmentation of the intended bone performed. Patient tracker was mounted and 3-D fluoroscopy performed using Siemens ISO-C 3D. Fusion of CT/MRI with 3D fluoroscopy was performed using “surface matching image correlation” and this automatically registered the bone with MRI/CT. The fused images were then ready for 3D navigation procedures. Nine patients were included in the series. There were eight fracture cases and seven performed with fused CT and 3-D fluoroscopy (two PCL avulsion fractures, two tibial plateau fractures, one femoral condyle fracture and three pelvic-acetabular fractures). Total of twenty-three screws had been inserted without complication. One tibial plateau fracture fixation and one core decompression for avascular necrosis of femoral head were performed with fused MRI to 3D fluoroscopy. In conclusion, intra-operative 3-D navigated procedures with fused pre-operative MRI/CT and intra-operative 3-D fluoroscopy were all successful with (1) extended working volume (2) higher resolution images (3) more soft tissue information. We foresee more applications of this new technique in other areas of computer aided surgery

Introduction. Computer-assisted hip navigation offers the potential for more accurate placement of hip components, which is important in avoiding dislocation, impingement, and edge-loading. The purpose of this study was to determine if the use of computer-assisted hip navigation reduced the rate of dislocation in patients undergoing revision THA. Methods and Materials. We retrospectively reviewed 72 patients who underwent computer-navigated revision THA [Fig. 1] between January 2015 and December 2016. Demographic variables, indication for revision, type of procedure, and postoperative complications were collected for all patients. Clinical follow-up was performed at 3 months, 1 year, and 2 years. Dislocations were defined as any episode that required closed or open reduction or a revision arthroplasty. Data are presented as percentages and was analyzed using appropriate comparative statistical tests (z-tests and independent samples t- tests). Results. All 72 patients (48% female; 52% male) were included in the final analysis [Fig. 2]. Mean age of patients undergoing revision THA was 70.4 ± 11.2 years. Mean BMI was 26.4 ± 5.2 kg/m. 2. The most common indications for revision THA were instability (31%), aseptic loosening (29%), osteolysis/eccentric wear (18%), infection (11%), and miscellaneous (11%). During revision procedure, polyethylene component was most commonly changed (46%), followed by femoral head (39%), and acetabular component (15%). At 3 months, 1 year, and final follow-up, there were no dislocations among all study patients (0%). Compared to preoperative dislocation values, there was a significant reduction in the rate of dislocation with the use of computer-assisted hip navigation (31% vs. 0%; p<0.05). Discussion. Our study demonstrates a significant reduction in the rate of dislocation following revision THA with the use of computer navigation. Although the cause of postoperative dislocation is often multifactorial, the use of computer-assisted surgery may help to curtail femoral and acetabular malalignment in revision THA

There are several methods for evaluating stability of the joint during total knee replacement (TKR). Activities of daily living demand mechanical loading to the knee joint, not only in full extension, but also in mid-flexion. The purpose of this study was to compare the varus-valgus stability throughout flexion in knees treated with either cruciate-retaining or posterior-stabilised TKR, using an intra-operative navigation technique. A total of 34 knees underwent TKR with computer navigation, during which the investigator applied a maximum varus-valgus stress to the knee while steadily moving the leg from full extension to flexion both before and after prosthetic implantation. The femorotibial angle was measured simultaneously by the navigation system at every 10° throughout the range of movement. It was found that posterior-stabilised knees had more varus-valgus laxity than cruciate-retaining knees at all angles examined, and the differences were statistically significant at 10° (p = 0.0093), 20° (p = 0.0098) and 30° of flexion (p = 0.0252). Cite this article: Bone Joint J 2013;95-B:493–7

Total hip replacement procedures are among the most frequent surgical interventions in all industrialized countries. Although it is a routine operationliterature reports that important parameters regarding for example cup orientation and leg length discrepancy often turn out to be not satisfying after surgery. This paper presents a novel concept to improve the reproducibility and accuracy for implantation of cup and stem prosthesis at exactly the desired locations. Existing computer- based commercial products either offer software solutions for just pre-operative planning, or imageless navigation systems that are only used during surgery in the operating theatre. The innovation of our approach is based on an integrated computer-assisted solution that combines pre-operative planning and intra-operative navigation to support THR procedures. The software for pre-operative planning can process both, 3D CT images and standard 2D x-ray images. A custom-built navigation system using optical 3D localizing technology has been developed to transfer planning results to the OR. The main objective of our approach is to implant the artificial joint in a way to restore the natural anatomy of the joint before surgery as close as possible, or with exactly planned modifications. In particular, cup inclination, cumulative anteversion of cup and stem, CCD angle and lateral offset, centre of rotation, leg length discrepancy, and joint range of motion are considered. It is not necessary to determine numerical values for all of these parameters because our approach uses a unique procedure to record the natural anatomical situation by combining pre-operative planning and intra-operative navigation, and subsequently supports implantation of the prosthesis components by surgical navigation in order to restore this situation. In case planar 2D x-ray images are used for pre-operative planning accurate scaling of these images is a prerequisite for exact determination of relevant parameters. The patient-specific scaling factor depends on the distance of the hip joint rotation centre from the x-ray detector or film. We have designed a low-cost localization system to be mounted close to the x-ray apparatus. It localizes the 3D position of the rotation centre by small motions of the leg and eliminates uncertainties of conventional methods that are caused by improper positioning of a calibration body. Easy and robust setup and application have been key objectives for the development of our custom-built navigation system. Acquisition of intraoperative parameters for example includes the determination of the acetabular centre axis by localizing selected landmarks at the acetabular rim. Intra-operative parameters are combined with pre-operative parameters without needing sophisticated matching procedures with the pre-operative images. A preliminary surgical workflow that will be detailed in the conference presentation has been designed for evaluation of the concept using sawbones models. Based on the promising results of our laboratory tests we have started to prepare first clinical experiments in close cooperation with surgeons

Introduction. Total shoulder replacement is a successful treatment for gleno-humeral osteoarthritis. However, components loosening and painful prostheses, related to components wrong positioning, are still a problem for those patients who underwent this kind of surgery. CT-based intraoperative navigation system is a suitable option to improve accuracy and precision of the implants as previously described in literature for others district. Method. Eleven reverse shoulder prostheses were performed at Modena Polyclinic from October 2018 to April 2019 using GPS CT-based intraoperative navigation system (Exactech, Gainsville, Florida). In the preoperative planning, Walch classification was used to assess glenoid type. The choice of inclination of the glenoid component, the screw length, as well as the inclination of the reamer was study and recorded using specific software using the CT scan of shoulder of each patient (Fig.1, Fig.2). Intraoperative and perioperative complications were recorded. Three patients were male, eight were female. Mean age was 72 years old (range 58=84). Three glenoid were type B2, six cases were B1, two case were type C1. Results. In all cases treated by reverse shoulder prostheses we had obtain good functional results at preliminary follow up. Eight degree posterior augment was used in seven case. Planned version was 0° in eight case, an anti-version of 3° was planned in the other three cases. Final reaming was as preoperatively planned in all cases except one. Mean surgical time was 71 minutes (range 51–82). One case of coracoid rupture has been reported. In all cases the system worked in proper manner without failures, no case of infection was reported. Discussion. It is well known as the more accurate placement of the glenoid led to enhanced long-term survivorship of the implant and decrease complication rates in RSTA. Our first experience with GPS navigation system has been satisfied. Good components’ positioning has been reached in all cases, without deviation from the preoperative planning. Pre-operative preparation using software has been always respected except in one case in which we decided to ream 1mm less to avoid excessive bone loss. In 3 case we decide to increase glenoid anti-version to allow a good cage containment in the scapula. No failure of the system has been recorded, with a little increase in the surgical time respect to traditional surgeries performed in our institute. The first case performed reported coracoid fracture, probably due to lack of experience in coracoid tracker positioning. It is very important to set the surgical theatre and the position of the patient in order to make the coracoid tracker visible for the computer. Screw positioning and length is decisively improved with GPS system compared with traditional implant. The most important advantage is to avoid the malposition of the glenoid component, solving problems like loosening or restriction in shoulder range of motion. We believe that a final cross check between preoperative planning and final control of the prostheses implanted, should be used in the future, but by now the GPS navigation system is a useful way to improve our surgery, especially in difficult cases. For any figures or tables, please contact the authors directly

In a prospective randomised clinical study acetabular components were implanted either freehand (n = 30) or using CT-based (n = 30) or imageless navigation (n = 30). The position of the component was determined post-operatively on CT scans of the pelvis. Following conventional freehand placement of the acetabular component, only 14 of the 30 were within the safe zone as defined by Lewinnek et al (40° inclination . sd. 10°; 15° anteversion . sd. 10°). After computer-assisted navigation 25 of 30 acetabular components (CT-based) and 28 of 30 components (imageless) were positioned within this limit (overall p < 0.001). No significant differences were observed between CT-based and imageless navigation (p = 0.23); both showed a significant reduction in variation of the position of the acetabular component compared with conventional freehand arthroplasty (p < 0.001). The duration of the operation was increased by eight minutes with imageless and by 17 minutes with CT-based navigation. Imageless navigation proved as reliable as that using CT in positioning the acetabular component

Acetabular implant position is important for the stability, function, and long-term wear properties of a total hip arthroplasty (THA). Prior studies of acetabular implant positioning have demonstrated a high percentage of outliers, even for experienced hip surgeons, when conventional instruments are used. Computer navigation is an attractive tool for use in THA, as it has been shown to improve the precision of acetabular component placement and reduce the incidence of outliers. However, computer navigation with imageless, large-console systems is costly and often interrupts the surgeon's workflow, and thus has not been widely adopted. Another method to improve acetabular component positioning during THA is the use of fluoroscopy with the direct anterior approach. Studies have demonstrated that the supine position of the patient during surgery facilitates the use of fluoroscopic guidance, thus improving acetabular component position. A handheld, accelerometer based navigation unit for use in total hip replacement has recently become available to assist the surgeon in positioning the acetabular component during anterior approach THA, potentially reducing the need for intra-operative fluoroscopic studies. We sought to compare the radiographic results of direct anterior THA performed with conventional instrumentation vs. handheld navigation to determine the accuracy of the navigation unit, and to see whether or not there was a reduction in the fluoroscopic time used during surgery. Furthermore, we timed the use of the navigation unit to see whether or not it required a substantial addition to surgical time. Our results demonstrate that a handheld navigation unit used during anterior approach THA had no difference with regard to acetabular cup positioning when compared to fluoroscopically assisted THA, but led to a reduction in the use of intra-operative fluoroscopy time

The object of this study was to develop a method to assess the accuracy of an image-free total knee replacement navigation system in legs with normal or abnormal mechanical axes. A phantom leg was constructed with simulated hip and knee joints and provided a means to locate the centre of the ankle joint. Additional joints located at the midshaft of the tibia and femur allowed deformation in the flexion/extension, varus/valgus and rotational planes. Using a digital caliper unit to measure the coordinates precisely, a software program was developed to convert these local coordinates into a determination of actual leg alignment. At specific points in the procedure, information was compared between the digital caliper measurements and the image-free navigation system. Repeated serial measurements were undertaken. In the setting of normal alignment the mean error of the system was within 0.5°. In the setting of abnormal plane alignment in both the femur and the tibia, the error was within 1°. This is the first study designed to assess the accuracy of a clinically-validated navigation system. It demonstrates in vitro accuracy of the image-free navigation system in both normal and abnormal leg alignment settings

Introduction. Reverse shoulder Arthroplasty is a successful treatment for gleno-humeral osteoarthritis. However, components loosening and painful prostheses, related to components wrong positioning, are still a problem for those patients who underwent this kind of surgery. Several new technology has been developed the improve the implant positioning. CT-based intraoperative navigation system is a suitable technology that allow the surgeon to prepare the implant site exactly as planned with preoperative software. Method. Thirty reverse shoulder prostheses were performed at Modena Polyclinic using GPS CT-based intraoperative navigation system (Exactech, Gainsville, Florida). Walch classification was used to assess glenoid type. Planned version and inclination of the glenoid component, planned seating, final version and inclination of the reamer were recorded. Intraoperative and perioperative complication were recorded. Planned positioning was conducted aiming to the maximum seating, avoiding retroversion >10° and superior inclination. Results. Eight patients were male, 22 were female. Mean age was 75 years old (range 58–87). 4 glenoid were type B3, four were B2, 10 cases were B1, 12 case were A1/A2. Posterior or superior augment was used in 15 cases. Mean planned seating was 93%. Mean preoperative version was -7.5±6.9°; Mean planned version was -2±2.8°; Mean intraoperative measured version was -1.9±2.8°; no statistical difference was found between planned and intraoperative version (p=0.16). Mean preoperative inclination was 1.8±6.°; Mean planned inclination was -2.2±2.4°; Mean intraoperative measured inclination was -2.1.9±2.3°; no statistical difference was found between planned and intraoperative version or inclination (respectively p=0.16 and p=0.32). Mean surgical time was 71 minute (range 51–82). Three cases of coracoid ruptures were reported, 1 failure of the system occurred. Discussion. GPS navigation system allows the surgeon to prepare the implant site as planned on Preoperative software in Reverse shoulder arthroplasty, with no statistical difference between planned orientation and intraoperative measured orientation. That means that even in the most difficult cases the surgeon is able to find a good positioning (93% seating)and to replicate it in the operative room. Only one failure of the system occurred, because too much time was passed between CT scan and surgery (9 months). Three coracoid fractures occurred in the first 10 cases: these could be addressed to a lack of confidence with the double lateralization of this prosthesis which increase tensioning on the coracoid and a lack of confidence in tracker positioning, which should be made as proximal as it is possible. Finally, the system needs several improvements to be considered a breakthrough technology, such as humeral component positioning and final control of the implant, but by now is a useful way to improve our surgery, especially in difficult cases

Accurate cup placement in total hip arthroplasty (THA) for the patients with developmental dysplasia of the hip (DDH) is one of the challenges due to distinctive bone deformity. Robotic-arm assisted system have been developed to improve the accuracy of implant placement. This study aimed to compare the accuracy of robotic-arm assisted (Robo-THA), CT-based navigated (Navi-THA), and manual (M-THA) cup position and orientation in THA for DDH. A total of 285 patients (335 hips) including 202 M-THAs, 45 Navi-THAs, and 88 Robo-THA were analyzed. The choice of procedure followed the patient's preferences. Horizontal and vertical center of rotation (HCOR and VCOR) were measured for cup position, and radiographic inclination (RI) and anteversion (RA) were measured for cup orientation. The propensity score-matching was performed among three groups to compare the absolute error from the preoperative target position and angle. Navi-THA showed significantly smaller absolute errors than M-THA in RI (3.6° and 5.4°) and RA (3.8° and 6.0°), however, there were no significant differences between them in HCOR (2.5 mm and 3.0 mm) or VCOR (2.2 mm and 2.6 mm). In contrast, Robo-THA showed significantly smaller absolute errors of cup position than both M-THA and Navi-THA (HCOR: 1.7 mm and 2.9 mm, vs. M-THA, 1.6 mm and 2.5 mm vs. Navi-THA, VCOR:1.7 mm and 2.4 mm, vs. M-THA, 1.4 mm and 2.2 mm vs. Navi-THA). Robo-THA also showed significantly smaller absolute errors of cup orientation than both M-THA and Navi-THA (RI: 1.4° and 5.7°, vs. M-THA, 1.5° and 3.6°, vs. Navi-THA, RA: 1.9° and 5.8° vs. M-THA, 2.1° and 3.8° vs. Navi-THA). Robotic-arm assisted system showed more accurate cup position and orientation compared to manual and CT-based navigation in THA for DDH. CT-based navigation increased the accuracy of cup orientation compared to manual procedures, but not cup position

Acetabular cup positioning remains a real challenge and component malpositioning after total hip arthroplasty (THA) can lead to increased rates of dislocation and wear. It is a common cause for revision THA. A novel 3D imageless mini-optical navigation system was used during THA to provide accurate, intraoperative, real-time, and non-fluoroscopic data including component positioning to the surgeon. This retrospective comparative single surgeon and single approach study examined acetabular component positioning between traditional mini-posterolateral THA and mini-posterolateral THA using the 3D mini-optical navigation system. A retrospective chart review was conducted of 157 consecutive (78 3D mini-optical navigation and 79 traditional non-navigation methods) THAs performed by the senior author using a mini-posterolateral approach at an ambulatory surgery center and hospital setting. Two independent reviewers analyzed postoperative radiographs in a standardized fashion to measure acetabular component positioning. Demographic, clinical, surgical, and radiographic data were analyzed. These groups were found to have no statistical difference in age, gender, and BMI (Table I). There was no difference between groups in acetabular components in the Lewinnek safe zone, 31.2% vs 26.6% (p = 0.53). Cup anteversion within the safe zone did not differ, 35.1% vs 40.5% (p = 0.48); while cup inclination within the safe zone differed, with more in the navigation group, 77.9% vs 51.9% (p < 0.01). Change in leg length was significantly different with the navigation group's leg length at 1.9 ± 6.3, less than the traditional at 5.4 ± 7.0 (p < 0.01). There was no difference in mean change in offset between groups (4.5 ± 5.9 vs 6.2 ± 7.9, p = 0.12); navigation, traditional) (Table II). The 3D mini-optical navigation group did have significantly longer operative time (98.4 ± 17.5 vs 89.3 ± 15.5 p < 0.01). Use of the novel 3D Mini-optical Navigation System significantly improved cup inclination compared to traditional methods while increasing operative time. For any figures or tables, please contact the authors directly

Aims. The purpose of this study was to compare the radiological outcomes of manual versus robotic-assisted medial unicompartmental knee arthroplasty (UKA). Methods. Postoperative radiological outcomes from 86 consecutive robotic-assisted UKAs (RAUKA group) from a single academic centre were retrospectively reviewed and compared to 253 manual UKAs (MUKA group) drawn from a prior study at our institution. Femoral coronal and sagittal angles (FCA, FSA), tibial coronal and sagittal angles (TCA, TSA), and implant overhang were radiologically measured to identify outliers. Results. When assessing the accuracy of RAUKAs, 91.6% of all alignment measurements and 99.2% of all overhang measurements were within the target range. All alignment and overhang targets were simultaneously met in 68.6% of RAUKAs. When comparing radiological outcomes between the RAUKA and MUKA groups, statistically significant differences were identified for combined outliers in FCA (2.3% vs 12.6%; p = 0.006), FSA (17.4% vs 50.2%; p < 0.001), TCA (5.8% vs 41.5%; p < 0.001), and TSA (8.1% vs 18.6%; p = 0.023), as well as anterior (0.0% vs 4.7%; p = 0.042), posterior (1.2% vs 13.4%; p = 0.001), and medial (1.2% vs 14.2%; p < 0.001) overhang outliers. Conclusion. Robotic system navigation decreases alignment and overhang outliers compared to manual UKA. Given the association between component placement errors and revision in UKA, this strong significant improvement in accuracy may improve implant survival. Level of Evidence: III. Cite this article: Bone Jt Open 2021;2-3:191–197

Imageless navigation is useful in acetabular cup orientation during total hip arthroplasty (THA). There is a limitation of accuracy in the imageless navigation system because of the registration method, that is, to palpate bony landmarks over the skin. To improve this limitation, ultrasound-based navigation was introduced for more precise registration of bony landmarks. We evaluated the accuracy of placement of the implant, which was measured by CT in 66 patients. 22 patients underwent THA with imageless navigation, and 44 patients underwent THA with ultrasound-based navigation. The accuracy was evaluated by comparison of the navigation values obtained during surgery with the CT measured values. For the 44 patients with ultrasound-based navigation system, the mean CIA was 39.6+4.1 degrees (mean+SD) and the CAA was 18.5+6.1 degrees with CT evaluation. Ultrasound-based navigation showed 39.0+3.2 degrees in CIA and 18.8+5.9 degrees in CAA during surgery. The mean absolute difference in cup inclination angle (CIA) between ultrasound-based navigation and CT was 2.4+2.1 degrees (range 0.1–9.2 degrees). The mean absolute difference in cup anteversion angle (CAA) between navigation and CT was 2.2+2.7 degrees (0.04–12.2 degrees). The rasp ante-torsion angle was 28.6+10.0 degrees in the ultrasound-based navigation system. The mean SAA was 28.8+9.3 degrees in CT. Strong correlation was found between the rasp ante-torsion angle and SAA (r=0.858). The mean absolute difference between the rasp ante-torsion angle and SAA was 4.3+3.6 degrees (0.2-17.2 degrees). For the 22 patients with imageless navigation system, the mean absolute difference between imageless navigation and CT in CIA, CAA, and SAA were 2.5+1.8 degrees (0.1–5.8 degrees), 5.4+3.8 degrees (0.1–17.2 degrees), and 5.2+3.0 degrees (1.1-12 degrees) respectively. The thickness of subcutaneous tissue at the pubic symphysis was correlated to the difference in CAA between the imageless navigation and CT (r=0.456). Ultrasound-based navigation showed higher accuracy in CAA compare to imageless navigation. Moreover, ultrasound-based navigation showed almost the same accuracy of placement of the implant compare to the reported accuracy with CT-based navigation. Ultrasound-based navigation system improved the limitation of accuracy in the imageless navigation system

We investigated whether a novel, real-time fluoroscopy based navigation system optimized component positioning and leg length in fluoroscopically aided Direct Anterior Approach Total Hip Arthroplasty (DAA-THA). We retrospectively reviewed 75 fluoroscopically assisted DAA-THA performed by a single surgeon: 37 procedures used the software intraoperatively to overlay anteversion, inclination, and leg length information over the existing fluoroscopic radiograph with the aim of enhancing component positioning. The control group consisted of 38 procedures from the single surgeon's patient pool who had undergone non-navigated fluoroscopic assisted DAA-THA one month prior to the system's trial. We used the software to compute each data point on an immediate post operative AP radiograph to replicate the intra operative measurement process. Our results demonstrate that the navigation group measurements were significantly closer to the target numbers with less variation. The mean values were significantly closer to target values anteversion (control: 14°, navigated: 19.1°), inclination (control: 37.7°, navigated: 40.8°) and leg length discrepancy (control: 4.7mm, navigated: 0.1mm). The mean difference from target value were also statistically significant: for anteversion (control: −6.0°, navigated: −0.9°), inclination (control: −2.3°, navigated: 0.8°) and leg length discrepancy (control: 2.7°, navigated: −1.9°). In addition, surgical time was shorter in the navigation group (75.7 vs. 74 minutes; p=0.001). The p values were all statistically significant (anteversion 0.0001, inclination 0.0019, LLD < 0.001 and surgical time 0.001). The real-time feedback and calculations provided by the navigation software provided a reproducible precision for component positioning and leg length measurement during DAA-THA. For any figures or tables, please contact authors directly

INTRODUCTION. Traditionally, acetabular component insertion in direct anterior approach (DAA) total hip arthroplasty (THA) has been performed using fluoroscopic guidance. Handheld navigation systems can be used to address issues of alignment, cup placement and accuracy of measurements. Previous navigation systems have been used successfully in total knee arthroplasty (TKA) and has now been introduced in THA. We investigated the use of a new accelerometer-based, handheld navigation system during DAA THA to compare it to traditional means. This study aims to determine accuracy of acetabular cup placement as well as fluoroscopy times between two groups of patients. METHODS. Data was prospectively collected for a group of consecutive DAA THA procedures using a handheld navigation system (n=45) by a single surgeon. This was compared to data retrospectively collected for a group that underwent the same procedure without use of the navigation system(n=50). The time for use of the navigation system, including insertion of pins/registration, guiding cup position, and removal of pins, was recorded intraoperatively. Postoperative anteroposterior and cross-table lateral radiographs were used to measure acetabular inclination and anteversion angles. Targeted angles for all cases were 40° ±5 for inclination and 20° ±5 for anteversion. Intraoperative fluoroscopy exposure times were obtained from post-anesthesia care unit radiographs. RESULTS. Mean time of pin insertion/registration, cup positioning and removal was 180.5 seconds, 127.7 seconds and 26 seconds, giving a mean total time of 5.6 minutes. There were no significant differences in mean postoperative acetabular inclination angles between the navigation group as compared to the non-navigation group (39.8° vs 40.6°) (p = .2). There were no significant differences in mean postoperative acetabular anteversion angles between the navigation group as compared to the non-navigation group (24.3° vs 23.7°) (p=.5). Mean intraoperative fluoroscopy exposure times were significantly lower in the navigation group as compared to the non-navigation group (12.6 vs 22.2 seconds) (p<.0001). CONCLUSION. The findings demonstrated that a new handheld navigation system required minimal increase in operative time and was as accurate for cup positioning as fluoroscopically assisted DAA THA. Furthermore, there was a 45% reduction in fluoroscopy exposure time. Reduction in fluoroscopy time will lower radiation exposure for the surgeon and patients

We have developed a CT-based navigation system using infrared light-emitting diode markers and an optical camera. We used this system to perform cementless total hip replacement using a ceramic-on-ceramic bearing couple in 53 patients (60 hips) between 1998 and 2001. We reviewed 52 patients (59 hips) at a mean of six years (5 to 8) postoperatively. The mid-term results of total hip replacement using navigation were compared with those of 91 patients (111 hips) who underwent this procedure using the same implants, during the same period, without navigation. There were no significant differences in age, gender, diagnosis, height, weight, body mass index, or pre-operative clinical score between the two groups. The operation time was significantly longer where navigation was used, but there was no significant difference in blood loss or navigation-related complications. With navigation, the acetabular components were placed within the safe zone defined by Lewinnek, while without, 31 of the 111 components were placed outside this zone. There was no significant difference in the Merle d’Aubigne and Postel hip score at the final follow-up. However, hips treated without navigation had a higher rate of dislocation. Revision was performed in two cases undertaken without navigation, one for aseptic acetabular loosening and one for fracture of a ceramic liner, both of which showed evidence of neck impingement on the liner. A further five cases undertaken without navigation showed erosion of the posterior aspect of the neck of the femoral component on the lateral radiographs. These seven impingement-related mechanical problems correlated with malorientation of the acetabular component. There were no such mechanical problems in the navigated group. We conclude that CT-based navigation increased the precision of orientation of the acetabular component and control of limb length in total hip replacement, without navigation-related complications. It also reduced the rate of dislocation and mechanical problems related to impingement

Introduction and Objective. The aim of this study was to evaluate whether CT-based pre-operative planning, integrated with intra-operative navigation could improve glenoid baseplate fixation and positioning by increasing screw length, reducing number of screws required to obtain fixation and increasing the use of augmented baseplate to gain the desired positioning. Reverse total shoulder arthroplasty (RSA) successfully restores shoulder function in different conditions. Glenoid baseplate fixation and positioning seem to be the most important factors influencing RSA survival. When scapular anatomy is distorted (primitive or secondary), optimal baseplate positioning and secure screw purchase can be challenging. Materials and Methods. Twenty patients who underwent navigated RSA (oct 2018 and feb 2019) were compared retrospectively with twenty patients operated on with a conventional technique. All the procedures were performed by the same surgeon, using the same implant in cases of eccentric osteoarthritis or complete cuff tear. Exclusion criteria were: other diagnosis as proximal humeral fractures, post-traumatic OA previously treated operatively with hardware retention, revision shoulder arthroplasty. Results. The NAV procedure required mean 11 (range 7–16) minutes more to performed than the conventional procedure. Mean screw length was significantly longer in the navigation group (35.5+4.4 mm vs 29.9+3.6 mm; p . .001). Significant higher rate of optimal fixation using 2 screws only (17 vs 3 cases, p . .019) and higher rate of augmented baseplate usage (13 vs 4 cases, p . .009) was also present in the navigation group. Signficant difference there is all in function outcomes, DASH score is 15.7 vs 29.4 and constant scale 78.1 vs 69.8. Conclusions. The glenoid component positioning in RSA is crucial to prevent failure, loosening and biomechanical mismatch, coverage by the baseplate of the glenoid surface, version, inclination and offset are all essential for implant survival. This study showed how useful 3D CT-based planning helps in identifying the best position of the metaglena and the usefulness of receiving directly in the operation theater real-time feedback on the change in position. This study shows promising results, suggesting that improved baseplate and screw positioning and fixation is possible when computer-assisted implantation is used in RSA comparing to a conventional procedure

Surgical navigation in joint replacement has been developed for more than 10 years. After the initial enthusiastic period, it appears that few surgeons have included this technology into their routine practice. The reasons for this backflow are lack of evidence of any clinical superiority for navigation implanted prostheses, higher costs and longer operative time. However, navigation systems have evolved, and might still belong to the future of joint replacement. Although most studies did not observe clinically relevant differences between navigated and conventional joint replacement, some registry studies identified significant advantages in favor of navigation: less blood loss, less early revision, subtle but relevant functional improvement… If TKR may be more forgiving, there is a trend to use less invasive implants (UKR), which are technically more demanding and may benefit from navigation. Ligamentous balancing may be more accurate and more reproducible with the help of navigation, and in that way patient specific templates may benefit from navigation. New techniques (short stem hip implants, hip resurfacing) have a relevant learning curve which may be fastened with navigation support. Another key point may be the individual joint reconstruction: anatomy is different from one patient to the other, and navigation may help detecting these subtle differences to adapt a more physiological joint reconstruction, instead reconstructing all joints on the same model. New navigation systems now available are designed in a more user-friendly style, with more straightforward workflow, and may be adapted to every surgeon's need. Finally, navigation system may act as documentation and quality control system for health care providers, as well as a very powerful research tool for scientists and manufacturers

We evaluated the oncological and functional outcome of 18 patients, whose malignant bone tumours were excised with the assistance of navigation, and who were followed up for more than three years. There were 11 men and seven women, with a mean age of 31.8 years (10 to 57). There were ten operations on the pelvic ring and eight joint-preserving limb salvage procedures. The resection margins were free of tumour in all specimens. The tumours, which were stage IIB in all patients, included osteosarcoma, high-grade chondrosarcoma, Ewing’s sarcoma, malignant fibrous histiocytoma of bone, and adamantinoma. The overall three-year survival rate of the 18 patients was 88.9% (95% confidence interval (CI) 75.4 to 100). The three-year survival rate of the patients with pelvic malignancy was 80.0% (95% CI 55.3 to 100), and of the patients with metaphyseal malignancy was 100%. The event-free survival was 66.7% (95% CI 44.9 to 88.5). Local recurrence occurred in two patients, both of whom had a pelvic malignancy. The mean Musculoskeletal Tumor Society functional score was 26.9 points at a mean follow-up of 48.2 months (22 to 79). We suggest that navigation can be helpful during surgery for musculoskeletal tumours; it can maximise the accuracy of resection and minimise the unnecessary sacrifice of normal tissue by providing precise intra-operative three-dimensional radiological information

Introduction:. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods:. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Sensitivity, specificity, accuracy and PPV were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. Results:. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76°(SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high PPV and specificity for determining cup abduction and anteversion (PPV >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46 mm (SD, 5.68) and −1.07 mm (SD, 5.75) on radiograph evaluation and 5.41 mm (SD, 5.11) and −2.24 mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value >0.2). Radiograph and navigation had a mean difference of 1.01 mm (SD, 2.83) for offset measurements and a mean difference of 1.05 mm (SD, 4.37) for postop limb length assessment. Discussion:. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

INTRODUCTION. Computer navigation has been shown to decrease the variance of component positioning in primary THR. The cost of a navigation system in the U.S. however can exceed $200,000 in capital costs and $300–850 a case for disposables. Our objective was to assess the cost-utility of a hip navigation system. METHODS. A review of the literature on costs and times for primary THR was done. Consecutive THR were done with an infrared navigation system. Total surgical time from incision to final skin closure and intra-operative time associated with the navigation process were recorded. Professional fees and the costs of revision surgery were estimated. RESULTS. The average total surgical time for THR was 96.6 minutes ± 8.4 SE for the navigated cohort and 77 minutes ± 1.3 SE for the THR without navigation. Setup of patient trackers and surgical landmarks registration averaged 14.4 minutes for the navigated surgery. The total additional costs (increase in OR time, anesthesia professional fees and the disposable expenses) were $813 for a primary THR using navigation. Reduction by 50% in dislocation and revision rates will yield savings where the system will pay for itself in 5 years doing only 30 cases per year. DISCUSSION AND CONCLUSION. Assuming 30% of all primary cases are performed with navigation, the incremental cost to the health care system would exceed $300 million a year. Depending on the model and assumptions used to calculate reduction in revisions and dislocations this system could be cost-effective for society if used in high-volume centers

BACKGROUNDS. Total knee arthroplasty (TKA) using an imageless navigation is widely used in these days. Despite the usefulness of navigation-assisted TKA, there are still limitations of accuracy. From previous studies, many factors have been suggested as causes of the discordance between pre-op planning and post-op results. In Addition, Registration of reliable landmark is very important factor in navigation-assisted TKA, fundamentally. Nevertheless, current method of registration process is substantially affected by subjective preference of operators. Until now, However, there is no consensus about the optimal range of reference point. Moreover, the tolerance of imageless navigation system is still questionable. We investigated the effect of variation during the manual registration in this study. We compared the measured alignment and calculated plan of navigation system which were collected from repeated independent registration processes. METHODS. From 7 March 2016 to 13 May 2016, 44 patients (49 knees) underwent navigation assisted TKA with Orthopilot® Aesculap system. The subject group were severe osteoarthritis patients, they have evaluated radiographically and clinically before the operation. we excluded candidates who have shown very severe mal-alignment (>20 °) and metaphyseal bowing in Pre-op radiographic evaluation. All patients were followed for postoperative long axis film that could measure the correction angle, and followed clinically for functional score. Authors executed multiple registration trials in a single case, each trial was implemented by different surgeons (Senior surgeon JHJ and trainee LJH1, LJH2). At first, Senior surgeon (JHJ) start the operation from initial approach. Standard sub-vastus approach was applied to all-patients. After the procedure of joint exposure, each participating surgeon did the examination of knee anatomy and registered optimal point of his own. It was repeated three times (J,L1,L2) via imageless navigation system. Then, we collected the information of measured limb alignments and calculated plans of tibia cutting from navigation system. RESULTS. 33 knees were evaluated as Gr. 4 in Kellgren-Lawrence classification. The other 16 knees were Gr. 3. In repeated registration processes, patients who were scored Gr. 3 have shown no significant differences in mechanical limb alignments, both coronal and sagittal. There were also no significant differences in Gr. 4 patients, too. Initial tibia planning has shown the largest variance between medial and lateral cutting level (0.4 ± 1.3 mm, in neutral alignment). But, no statistical significance was observed. There is a tendency that the deviation of tibia planning has diminished gradually with the progression of this study. In radiographic evaluation, all cases have satisfactory limb alignments postoperatively. CONCLUSION. Our experiment suggest that variation of landmark registration alone couldn't have a significant effect on the calculated alignment of navigation system. In this study, we concluded that tolerable range of registration process for alignment calculation is relatively wide. Additionally, we think that the cutting depth is more vulnerable than alignment calculation, and it may need further study with more cases. Measured limb alignment is almost reliable in imageless navigation. Even though operators were not so experienced for the registration process

Objectives. Few reports were shown about the position of the cup in total hip arthroplasty (THA) with CT-based navigation system. We use minimally invasive surgery (MIS) technique when we perform cementless THA and the correct settings of cups are sometimes difficult in MIS. So we use CT-based navigation system for put implants with correct angles and positions. We evaluated the depth of cup which was shown on intra-operative navigation system. Materials and Methods. We treated 30 hips in 29 patients (1 male and 28 females) by navigated THA. 21 osteoarthritis hips, 6 rheumatoid arthritis hips and 3 idiopathic osteonecrosis hips were performed THA with VectorVision Hip navigation system (BrainLAB). Implants were AMS HA cups and PerFix stems (Japan Medical Materials, Osaka). Appropriate angles and positions of cups were decided on the 3D model of pelvis before operation. According to the preoperative planning, we put the implants with navigation system. We correct the pelvic inclination angle and measured the depth of cups with 3D template software. Results. The average distance from the surface of the cup to the edge of medial wall of pelvis was 3.4mm (0.0–8.0mm) on the axial plane which include the center of femoral head on postoperative CT. The average distance from the surface of the cup to the edge of medial wall of pelvis was 6.4mm (1.5–15.0mm) on intraoperative navigation. The average error was 2.9mm (0.0–9.0mm). The cup positions of post operative CT were deeper than that of intraoperative navigation in twenty six hips (86%). Conclusions. The shallow setting of cups caused the instability of cups. Deep setting caused damage of acetabular fossa. The positions of cups on the navigation system tend to be shown shallower than actual positions, so we should take care of deeper setting

Minimally invasive total knee replacement (MIS-TKR) has been reported to have better early recovery than conventional TKR. Quadriceps-sparing (QS) TKR is the least invasive MIS procedure, but it is technically demanding with higher reported rates of complications and outliers. This study was designed to compare the early clinical and radiological outcomes of TKR performed by an experienced surgeon using the QS approach with or without navigational assistance (NA), or using a mini-medial parapatellar (MP) approach. In all, 100 patients completed a minimum two-year follow-up: 30 in the NA-QS group, 35 in the QS group, and 35 in the MP group. There were no significant differences in clinical outcome in terms of ability to perform a straight-leg raise at 24 hours (p = 0.700), knee score (p = 0.952), functional score (p = 0.229) and range of movement (p = 0.732) among the groups. The number of outliers for all three radiological parameters of mechanical axis, frontal femoral component alignment and frontal tibial component alignment was significantly lower in the NA-QS group than in the QS group (p = 0.008), but no outlier was found in the MP group. . In conclusion, even after the surgeon completed a substantial number of cases before the commencement of this study, the supplementary intra-operative use of computer-assisted navigation with QS-TKR still gave inferior radiological results and longer operating time, with a similar outcome at two years when compared with a MP approach. Cite this article: Bone Joint J 2013;95-B:906–10

The purpose of this study is to evaluate accuracy of tibia cutting and tibia implantation in UKA which used navigation system for tibia cutting and tibia component implantation, and to evaluate clinical results. We performed 72 UKAs using navigation system from November, 2012. This study of 72 knees included 56 females and 16 males with an average operation age of 74.2 years and an average body mass index (BMI) of 24.8 kg/m2. The diagnosis was osteoarthritis (OA) in 67 knees and osteonecrosis (ON) in 5 knees. The UKA (Oxford partial knee microplasty, Biomet, Warsaw, IN) was used all cases. We evaluated patients clinically using the Japanese orthopaedic association (JOA) score, range of motion (ROM), operation time, the amount of bleeding and complications. Patients were evaluated clinically at preoperation and final follow up in JOA score and ROM. As an radiologic examination, we evaluated preoperative and postoperative lower limb alignment in FTA (femoro-tibial angle) by weightbearing long leg antero-posterior alignment view X-rays. Also we evaluated a tibial component implantation angle by postoperative CT, and tibia cutting angle by intraoperative navigation system. We defined the tibial angle which a tibia functional axis and the tibia component made in coronal plane, also tibial posterior slope angle which a tibia axis and tibia component made in sagittal plane by CT. We measured tibial angle and tibial posterior slope angle by 3D template system. We performed UKA in all cases mini-midvastus approach. At first we performed osteotomy of the proximal medial tibia using CT-Free navigation. At this procedure we performed osteotomy to do re-cut if check did cutting surface in navigation, and there was cutting error (>3°), and then to do check again in navigation. Next we did not use navigation and went the osteotomy of the distal femur with an IM rod and drill guide of microplasty system. And then we performed a trial and decided bearing gap and moved to cementing. At first we went cementing of the tibia component. At this procedure we went to drive implant again if check did implant surface in navigation, and there was implantation error(>3°), and to do check. We checked did tibia cutting, tibia implantation carefully in navigation. In addition, We sterilize a clips and use it came to be in this way possible for the check of the first osteotomy side exactly. ROM was an average of 122.7° of preoperation became an average of 128.2° at final follow up, and JOA score was an average of 50.5 points of preoperation improved an average of 86.6 points at final follow up after UKA. An average of the operation time was 94 minutes, an average of the amount of bleeding was 137.7ml, and complications were one proximal type deep venous thrombosis (DVT) and one pin splinter joining pain by navigation, .Asetic loosening(tibial component) was one case, and this conversed the TKA. In the radiologic evaluation, FTA was an average of 182.1° of preoperation corrected an average of 175.9°after UKA. In other words, an average of 6.2° were corrected by UKA. The tibia component implantation angle was an average of 90.18° in a measurement by the CT after UKA, intoraoperative tibia component implantation angle was an average of 90.32° in a measurement by the navigation system. These two differences did not accept the significant difference at an average of 1.33°.(P=0.5581). Similarly, the posterior slope angle were as follow; average of 5.65°by CT and average of 5.75°by navigation. These two differences did not accept the significant difference at an average of 1.33°. (P=0.6475). Discussion: We performed UKA using navigation and evaluated the implantation accuracy for tibia osteotomy, tibia implantation. They were good alignment with an average of 90.18°, and outliers more than 3° were two cases(2.8%). It will be necessary to examine long-term progress including clinical results complications in future. We are performed UKA now in femur side using PSI(patient specific instruments) and tbia side using Navigation

Introduction. CT-based navigation system in total hip arthroplasty (THA) is widely used to achieve accurate implant placement. Now, we developed our own CT-based navigation system originally, and since then we have been conducting various analysis in order to use the system more effectively. We compared the accuracy of registration with this navigation system and land mark matching type navigation system. In this study, we evaluated the influence of the surgical approach to the accuracy of registration. Methods. Between June 2015 and February 2016, 28 consecutive uncemented THAs were performed in 26 patients. The preoperative diagnosis was osteoarthritis in 20 hips, osteonecrosis of the femoral hips in 5, and rheumatoid arthritis in 3. The newly developed navigation system was a CT based, surface matching type navigation system. We used newly developed navigation system and commercially available land-mark type CT-based navigation system in the setting of acetabular sockets under the same condition. After we fixed the cementless cup, we measured the cup setting angle of inclination and anteversion on each navigation system. Postoperative assessment was performed using CT one week after the operation, and measured the actual angle of the cup. Approach of operations were performed via posterolateral approach in 14 hips, and Hardinge approach in 14 hips. We calculated the absolute value of the cup angle difference between intra-operative value and post-operative value with each navigation system and compared the accuracy between each navigation system and surgical approach. Results. The mean inclination using the Land-mark type navigation(group L) was 38.3±3.8°, using our navigation system (group S) was 38.7±5.7 °, the mean anteverion on group L was 25.8±5.6°, and group S was 27.3±10.2°. The mean of actual inclination of the implants calculated by postoperative CT was 38.4±7.1°, the mean of actual anteversion was 25.8±8.3°. In comparison with the absolute value of the difference between intra-operative and post-operative date, the mean difference of inclination on group L was 6.5±5.7°, and group L was 3.7±3.1 °, the difference was significant (p<0.05). The mean difference of anteversion of group L was 4.7±4.6 °, group S was 4.0±3.3°. In group L, the mean of absolute value of the difference between intra-operative and post-operative date of inclination via Hardinge approach was 6.0±6.8°, and posterior approach was 7.9±4.5°. In group S, The mean difference of inclination via Hardinge approach was 3.0±1.8°, and posterior approach was 4.5±4.1°. In group L, The mean difference of anteversion of Hardinge approach was 4.2±4.1°, and posterior approach was 5.3±5.3°. In group S, The mean difference of anteversion of Hardinge approach was 3.8±3.5°, and posterior approach was 4.2±3.3°. Discussion. N-navi was superior on inclination of the acetabular socket setting. Considering surgical approach, the accuracy was not good via posterior approach. We should take surface matching points widely around the acetabulum, however, to take points of anterior the acetabulum via posterior approach was difficult because of the femur. It was the reason of decrease the accuracy via posterior approach. We should choose the area of surface matching points according to surgical approach to make the registration more accurate

Introduction. While component malposition remains a major short and long term problem associated with total hip arthroplasty, enhanced technologies such as navigation and robotics have not yet been widely adopted. Both expense and increased OR time can be obstacles to adoption. The current study assesses the effect of the use of a smart mechanical navigation system on surgery time in total hip arthroplasty. Patients and Methods. 514 consecutive primary total hip arthroplasties were performed by a single surgeon from January 1, 2015 through March 31, 2016. Of these, 40 were performed using a smart mechanical navigation system (the HipXpert System, Surgical Planning Associates Inc., Boston, Massachusetts) and 474 were performed without navigation. The patients were not randomized. Incision to closure time (surgery time) was recorded for each procedure. A two tailed t-test was performed to assess statistical significance. Results. Mean surgery time for the non-navigated cases was 66 minutes. Mean surgery time for the navigated cases was 70 minutes. The difference in surgery time between the two groups was statistically significant (p=0.003). Conclusion. Adoption and use of a smart mechanical navigation system has a measurable increase in OR time of 4 minutes. This increase in OR time is quite small and with experience, is likely to further decrease. The amount of surgery time necessary for the use of the system is small compared to traditional navigation systems and especially to robotic systems. The study demonstrates that the adoption of a new smart mechanical navigation system increased surgery time very little. We anticipate that increased experience with the system will allow for the reduction in the need for intraoperative radiographs, which will further decrease surgery time and associated cost while simultaneously improving accuracy

Pre-operative knowledge. Knowledge-based total hip arthroplasty is becoming increasingly recognised for improved safety, efficiency, and accuracy. Pre-operative knowledge of native and planned femoral anteversion, the exact size of implants, neck length and offset, and head lengths can serve to safely accelerate surgery and reduce the need for intra-operative imaging. Pre-operative knowledge of the effect on change in leg length and offset effected by specific implant combinations can serve to minimise undesired changes. The use of a smart mechanical navigation tool superimposed on this knowledge, can serve to easily and swiftly achieve optimal component position. Cost savings. Economic data from Q1 2013 to Q2 2016 demonstrate that CMS-insured patients treated by knowledge-based surgery using the HipXpert mechanical navigation system combined with the superior hip approach have the lowest cost of all patients treated in Massachusetts by an average of more than $7,000 over 90 days for Medicare Part A expenditure (HipXpert System, Surgical Planning Associates, Boston, MA). The data show that these combined techniques outpace all other technology/technique combinations including robotics. Accuracy. The system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases including an independent study. This compares to a recent study of robotic methods that showed only 88% accuracy in inclination and 84% for anteversion. Summary. Knowledge-based surgery with smart mechanical navigation has shown the potential to accelerate surgery, improve safety, lower cost and facilitate recovery

Background. Total hip arthroplasty (THA) is one of the most successful surgical procedures ever performed. Nevertheless if procedure is performed by high or low volume surgeons; more than 50% of cups are still placed out of the safe zone, which is connected to lower survival rate of the prosthesis. The idea was to develop an imageless navigation system for safe and accurate positioning of the cup in THA procedures, without a need of any preoperative computer tomography (CT) or magnetic resonance imagining (MRI). Methods. The validation of the system was approved by National Ethics Committee. The committee allowed the validation on 10 patients who all signed the agreement for participation in the study. Unselected patients undergoing THA were included. All patients had had performed preoperative x-rays of pelvis and hips for standard preoperative planning. Immediately before skin incision, anterior pelvic plane (APP) was defined with help of specially developed electromagnetic navigation system (Guiding Star, E-Hip module, Ekliptik d.o.o., Ljubljana, Slovenia) and specificaly designed hardware tool which is essential for accurate APP determination [Fig.1]. In all patients THAs were performed through direct lateral approach and all implanted components (Allofit S cup and Alloclassic stem, Zimmer Inc., Warsaw, Indiana, USA) were implanted with freehand technique according to preoperative plan. After placement of the cups their inclination and anteversion angles were determined with aforementioned navigation system [Fig. 2]. The day after surgery, low dose CT scans of pelvises of operated patients were performed and DICOM format files were up-loaded into EBS software (Ekliptik d.o.o., Ljubljana, Slovenia), a multipurpose application for perioperative planning, measuring and constructing where virtual copies of pelvises were generated. On virtual pelvises the position of the cups was measured by independent person [Fig.3]. Measurements were compared, statistically analysed and the deviation calculated with root mean square error (RMSE) method. Afterwards the average error (eaver) and standard deviation (σ) between intraoperatively determined and postoperatively measured angles were calculated. Results. We included 10 patients in the study, with 6 left and 4 right hips. The maximal and minimal differences between navigation and CT measurements for inclination angles were 5.3° and 0.3° respectively, with calculated eaver of 0.7°, σ of 2.6° and RMSE of 2.6°. The maximal and minimal differences between navigation and CT measurements for anteversion angles were 4.6° and 0.7° respectively, with calculated eaver of −1.9°, σ of 1.8° and RMSE of 2.6°. Conclusion. We determined that the imageless navigation system we validated is a very accurate tool for cup placement in THA. The accuracy of the system is within 2° which by far exceeds the abilities of the best freehand techniques. In line to the trends, supporting more precise and less invasive surgery, the THA with help of imageless navigation should in our opinion become a golden standard, especially in minimally invasive procedures

Introduction. Robotic-assisted hip arthroplasty helps acetabular preparation and implantation with the assistance of a robotic arm. A computed tomography (CT)-based navigation system is also helpful for acetabular preparation and implantation, however, there is no report to compare these methods. The purpose of this study is to compare the acetabular cup position between the assistance of the robotic arm and the CT-based navigation system in total hip arthroplasty for patients with osteoarthritis secondary to developmental dysplasia of the hip. Methods. We studied 31 hips of 28 patients who underwent the robotic-assisted hip arthroplasty (MAKO group) between August 2018 and March 2019 and 119 hips of 112 patients who received THA under CT-based navigation (CT-navi group) between September 2015 and November 2018. The preoperative diagnosis of all patients was osteoarthritis secondary to developmental dysplasia of the hip. They received the same cementless cup (Trident, Stryker). Robotic-assisted hip arthroplasty were performed by four surgeons while THA under CT-based navigation were performed by single senior surgeon. Target angle was 40 degree of radiological cup inclination (RI) and 15 degree of radiological cup anteversion (RA) in all patients. Propensity score matching was used to match the patients by gender, age, weight, height, BMI, and surgical approach in the two groups and 30 patients in each group were included in this study. Postoperative cup position was assessed using postoperative anterior-posterior pelvic radiograph by the Lewinnek's methods. The differences between target and postoperative cup position were investigated. Results. The acetabular cup position of all cases in both Mako and CT-navi group within Lewinnek's safe zone (RI: 40±10 degree; RA: 15±10 degree) in group were within this zone. Three was no significant difference of RI between Mako and CT-navi group (40.0 ± 2.1 degree vs 39.7± 3.6 degree). RA was 15.0 ± 1.2 degree and 17.0 ± 1.9 degree in MAKO group and in CT-navi group, respectively, with significant difference (p<0.001). The differences of RA between target and postoperative angle were smaller in MAKO group than CT-navi group (0.60± 1.05 degree vs 2.34± 1.40 degree, p<0.001). The difference or RI in MAKO group was smaller than in CT-navi, however, there was no significance between them (1.67± 1.27 degree vs 2.39± 2.68 degree, p=0.197). Conclusions. Both the assistance of the robotic arm and the CT-based navigation system were helpful to achieve the acetabular cup implantation, however, MAKO system achieved more accurate acetabular cup implantation than CT-based navigation system in total hip arthroplasty for the patients with OA secondary to DDH. Longer follow-up is necessary to investigate the clinical outcome

Utilization of C-arm fluoroscopy during direct anterior total hip arthroplasty (THA) is disruptive and potentially increases the risks of patient infection and cumulative surgeon radiation exposure. This pilot study evaluated changes in surgeon C-arm utilization during an initial 10 cases of direct anterior THA in which an imageless computer-assisted navigation device was introduced. This retrospective study includes data from 20 direct anterior THA cases performed by two orthopaedic surgeons (BC; SRE) in which an imageless computer-assisted navigation device was utilized (Intellijoint HIP®; Intellijoint Surgical, Waterloo, ON, Canada). Total C-arm image count was recorded in each case, and cases were grouped in sets of 5 for each surgeon. The mean C-arm image count was calculated for each surgeon, and combined C-arm image counts were calculated for the study cohort. Student's t-tests were used to assess differences. The use of intraoperative C-arm fluoroscopy decreased from a mean of 9.4 images (standard deviation [SD]: 8.6; Range: 3 – 23) to a mean of 2 images (SD: 2.9; Range: 0 – 7) for surgeon BC (P=0.10) and decreased from a mean of 10.75 images (SD: 1.2; range 9 – 12) to a mean of 6.7 images (SD: 8.3; range: 0 – 16) for surgeon SRE (P=0.36). Combined, an overall decrease in intraoperative C-arm image count from a mean of 11.3 images (SD: 6.9; range: 6 – 23) to a mean of 3.7 images (SD: 3.9; range: 0 – 8.5) was observed in the study cohort (P=0.06). The adoption of imageless computer-assisted navigation in direct anterior THA may reduce the magnitude of intraoperative C-arm fluoroscopy utilization; however further analysis is required

There is enough evidence to show that navigation improves precision of component placement and consistent and accurate restoration of limb alignment, allowing the surgeon to achieve the desired neutral or kinematic alignment. Computer-assisted TKA provides excellent information regarding gap equality and symmetry throughout the knee range of motion. Accurate soft-tissue balancing is facilitated by CAS. It allows precise, quantitative soft tissue release for deformities, especially in knees with severe flexion contractures and severe rigid varus and valgus deformities. It allows accurate restoration of joint line, and posterior femoral offset. Knee arthritis with complex extra-articular deformities and in-situ hardware can be tackled appropriately using computer navigation where conventional techniques may be inadequate. It also allows intra-articular correction for extra-articular deformities due to malunions and facilitates extra-articular correction in cases with severe extra-articular tibial deformities. In obese patients, where the alignment of the limb is difficult to assess, computer navigation improves accuracy and reduces the number of outliers. The ability to quantify the precise amount of bone cuts and soft tissue releases needed to equalise gaps and restore alignment, reduced blood loss, and reduced incidence of systemic emboli improves the safety of the procedure and hastens functional recovery of the patient. Recent evidence shows that the rate of revision especially in younger patients is reduced with navigation

Navigation has been felt to play a role in a number of THA issues. These issues include: 1) Instability-Dislocation; 2) Leg Length discrepancy; 3) Impingement and its impact on range of motion and wear; 3) gait mechanics; and 4) less invasive surgery. Navigation requires that anatomic landmarks be accurately identified. This can be done using images obtained either pre-operatively or intra-operatively (image-based navigation) or using intra-operative techniques for registering the relevant bony anatomy (image-free). The suggested advantages of imaged-based navigation are that is potentially very accurate, makes registering bone landmarks relatively easy and provides information about relevant anatomic landmarks that are not visible during surgery. The disadvantages of image-based navigation are that the acquisition of pre-operative imaging may be inconvenient or cumbersome, the imaging may be associated with increased radiation exposure, the imaging may be associated with additional costs and the pre-operative planning carried out on the imaging may be elaborate and time consuming. The advantages of image-free navigation are that no special pre-operative planning is required, no special imaging is necessary and the intra-operative workflow is consistent with the routine performance of a THA. However, image free registration techniques may be unreliable or inaccurate and the information obtained with image-free registration techniques is limited. When surgeons proficient in the technique perform image free navigation, positioning of the acetabular component is more accurate and consistent than that achieved using manual techniques. However, this increased accuracy has not been associated with a reduction in hip dislocations and has not had a measurable impact on short-term clinical outcomes. However, navigation is an accurate measurement tool that can be used to validate other computer-based technologies (e.g. patient specific guides). Navigation is also essential to the performance of robotic hip surgery. It is in this latter capacity that navigation may prove most useful to the hip surgeon

Introduction. Computer navigation is a highly sophisticated tool in orthopedic surgery for component placement in total hip arthroplasty (THA). A number of recommendations have been published. Although Lewinnek's safe-zone is the best-known among these its significance is questioned in recent years since it addresses the acetabular socket only ignoring the femoral stem. Modern target definitions consider both socket and stem and provide well-defined recommendations for complementary component positioning. We present a new small-sized hand-held imageless navigation system that implies these targets and supports the surgeon in realizing the concept of combined anteversion and combined Target-Zone (cTarget- Zone) in THA and to control leg length and offset without altering the standard surgical work-flow and we report initial results. Methods. The targets for positioning the components of a total hip as expressed by radiographic cup inclination (cRI) and anteversion (cRA), stem antetorsion (sAT) and neck-to-shaft angle (sNSA) are determined for a specific prosthesis system using a computerized 3D-model. The optimizing goal is maximizing the size of the cSafe-Zone providing the largest target zone for an impingement-free prosthetic range of motion (pROM) in order to minimize the risk for dislocation in physiologic and combined movements. Independent parameters like head size, head-to-neck ration and also component orientations like cRI, cRA, sAT and sNSA were varied systematically and the optimal cSafe-Zone was computed in semi-automated batch runs. These optimized prosthesis-specific results were introduced into the software of the hand-held navigation system. This system measures leg length, offset, acetabular and femoral head centers intraoperatively. Results. In contrast to Lewinnek the outline of our cSafe-Zone is not rectangular but polygonal. Its size shows prosthesis-specific maxima. The largest zones are found for optimal sNSA values at 126° +/−4°, optimal ranges for cRI depend on head size and range from 44° to 36°, best sAT range from 10° to 18°, cRA from 18° to 25°. There is a prosthesis- specific linear correlation between sAT and cRA that denotes the combined anteversion. The target value for combined anteversion is not dependent on pelvic tilt but on sNSA. The hand-held navigation system displays all these orienting parameters as well as leg-length and offsets. Furthermore, it supports a virtual reduction work-flow thus accelerating surgery. All these information provide important decision-making details for the surgeon intraoperatively in real-time for augmented quality. Conclusion. The combined Target-Zone provides the basis for patient- and implant-specific control of prosthesis implantation. It includes all important positioning parameters of both total hip components and such gives well-defined individual recommendations for the targets. The new hand-held navigation system (Naviswiss) provides a smart way to direct and control the total hip implantation according to the best combined orientation considering also the concept of combined Safe-Zone. Such it prevents outliers, provides better safety and documents the surgical workflow and the final result of the surgery

INTRODUCTION. Several papers have reported the efficacy of an imageless navigation system in acetabular cup orientation during total hip arthroplasty (THA). Also, an imageless navigation system is useful for recovering leg length discrepancy. However, no study has evaluated the accuracy of the stem antetorsion angle (SAA) with an imageless navigation system in THA. The purpose of this study was to evaluate the accuracy of the stem antetorsion angles, which were measured by CT with the CT-free navigation system. Also, we evaluate the factors that affect the inaccuracy. MATERIALS AND METHODS. CT evaluation was performed in 60 patients (60 joints) who underwent primary THA from December 2011 to March 2014. Fifty-nine patients were female. The mean age at surgery was 67 years. The mean BMI at surgery was 24.0 kg/m2. Fifty-four patients had osteoarthrosis, 5 patients had osteonecrosis, and 1 patient had femoral neck fracture. All surgeries were performed in the supine position with the direct anterior approach. The OrthoPilot imageless navigation system was used during surgery. An Excia stem was used in 47 patients and a Bicontact stem was used in the other 13. Evaluation of SAA was carried out. Instead of SAA, the navigation indicates the rasp antetorsion angle based on the hip-knee-ankle plane during surgery. SAA based on the posterior condylar plane was measured with CT by using 3D THA plannning software. The accuracy of the imageless navigation system was evaluated by comparison of the navigation values obtained during surgery with the CT measured values. Correlations were analyzed with Pearson correlation analysis. RESULTS. The rasp antetorsion angle was 28.1±9.6 degrees [range 7.7–49.2 degrees]. The mean SAA was 29.9±8.9 degrees [10.7–49.7 degrees] in CT. Strong correlation was found between the rasp antetorsion angle and SAA (p<0.001, r=0.858, Figure). The difference between SAA and the rasp antetorsion angle (SAA – rasp antetorsion angle) was 1.8±4.7 degrees [-6.7–11.9 degrees]. The mean absolute difference between the rasp antetorsion angle and SAA was 4.0±3.1 degrees [0.2–11.9 degrees]. Forty-five cases (75%) showed less than 5 degrees of difference between SAA and the rasp antetorsion angle. Five cases (8.3%) showed more than 10 degrees of difference. In these five cases, SAAs were greater than the rasp antetorsion angles. Patients’ age, height, weight, and BMI did not affect the difference. Deformity of the femoral head, osteoarthrosis of the hip with subluxation, and osteoarthrosis of the knee were found in the patients who showed more than 5 degrees of difference between SAA and the rasp antetorsion angle. DISCUSSION. This study demonstrated that imageless navigation showed good accuracy for determining SAA during operation. This helps surgeons to recognize combined anteversion during surgery, and to avoid impingement after THA. This navigation system determines rasp antetorsion angle based on the hip-knee-ankle plane. The hip center is defined by setting the trial cup on the acetabulum. The knee center and the ankle center are defined by pointing over the skin. Therefore, deformity of the acetabulum or femoral head may affect the accuracy of the rasp antetorsion angle

Introduction. Two aspects are very important for knee joint replacement – restoration of biomechanical limb axis and achieving ligaments balance. Computer navigation allows us to do all this. Material and methods. We analysed 94 knee joint replacement surgeries using computer navigation by “STRYKER”. Results. There is no substantial difference between results of correction of biomechanical axis with computer navigation and without it in case of uncomplicated joint replacement. So, completer correction of axis (varus/valgus zero degrees) with computer navigation was achieved in 84% of cases versus 79% without navigation. There was varus or valgus deformity up to two degrees in 12% after surgery (without navigation −17% of cases). Error in deformity correction without application of navigation was three-five degrees in 4% of cases (all were challenging joint replacement). Advantages of navigation are obvious in case of large deformities, and also when insertion of intramedullary guide is undesirable or impossible. Use of navigation requires good skills of joint replacement, because landmarks should be chosen precisely and possibility of error during determining the center of rotation for the femoral head should be taken into consideration. Duration of surgery without navigation is 82.6±16.4 minutes and is much longer in the beginning of the learning curve (one hour longer or more). After acquiring skills the surgery takes 118±15.6 minutes. Conclusion. We evaluate use of navigation system as a modern and in-demand trend. Use of navigation should be started after getting good skills of joint replacement. Violation of the technology of determining landmarks leads to wrong virtual modeling and serious errors in positioning components. Advantages of navigation are obvious in evident bone deformity, when it is impossible or undesirable to open a medullary canal

A cadaver study using six pairs of lower limbs was conducted to investigate the accuracy of computer navigation and standard instrumentation for the placement of the Birmingham Hip Resurfacing femoral component. The aim was to place all the femoral components with a stem-shaft angle of 135°. The mean stem-shaft angle obtained in the standard instrumentation group was 127.7° (120° to 132°), compared with 133.3° (131° to 139°) in the computer navigation group (p = 0.03). The scatter obtained with computer-assisted navigation was approximately half that found using the conventional jig. Computer navigation was more accurate and more consistent in its placement of the femoral component than standard instrumentation. We suggest that image-free computer-assisted navigation may have an application in aligning the femoral component during hip resurfacing

Introduction. Total knee arthroplasty (TKA) reliably improves pain and function in patients with knee osteoarthritis (OA), though a substantial percentage of patients remain unsatisfied. Reasons include the presence of complications, persistent pain, and unmet expectations. The aim of this study was to determine whether the sequential addition of accelerometer-based navigation of the distal femoral cut and sensor-assisted soft tissue balancing changed complication rates, radiographic alignment, or patient-reported outcomes (PROs) compared to TKA performed with conventional instrumentation. Methods. This retrospective cohort study included 371 TKAs in 319 patients. All surgeries were performed by a single surgeon in sequential fashion using a measured resection technique with a goal of mechanical alignment. The historical control group, utilizing intramedullary guides for distal femoral resection and surgeon-guided soft tissue balancing, was compared to group 1 (accelerometer-based navigation for distal femoral resection, surgeon-guided balancing) and group 2 (navigated femoral resection, sensor-guided balancing). Primary outcome measures were PROMIS scores including physical function computerized adaptive test (PF CAT), and the Global 10 health assessment (including physical, mental, and pain scores), and Knee Injury Osteoarthritis and Outcome Score (KOOS), measured preoperatively and at 6 weeks and 12 months postoperatively. Radiographic measurements included component position and overall mechanical alignment of the limb and were made at 6 weeks by a single examiner from hip to ankle standing films. Charts were reviewed for pre- and postoperative ROM at 6 weeks, polyethylene insert morphology, and postoperative hematocrit change. Complications were recorded, including manipulation under anesthesia and reoperation. Our study was powered to detect a difference of 1 standard deviation in PF CAT score with 100 patients. Statistical analysis was performed by a statistician including t-tests, multivariate regression, and time series plot analyses. Results. There were 194 patients in the control group, 103 in group 1, and 74 in group 2. There was no difference in baseline patient demographics. Patients in group 2 had higher baseline mental health subscores than control and group 1 patients (53.2 vs 50.2 vs 50.2, p=0.04). There were no differences in 6-week and one-year postop PF CAT, physical or mental subscores, pain scores, or KOOS scores (all p>0.05). There were 8 total complications in the control group (4.1%), 4 in group 1 (3.8%), and 1 in group 2 (1.4%) (p>0.4). The postoperative mechanical axis of the limb was within 3 degrees of neutral in 71.6% of control patients, 74.8% in group 1, and 85.1% in group 2 (p=0.1). There was no difference in femoral component coronal alignment between groups (p=0.91), though controls had a small but significantly higher degree of flexion in the sagittal plane (6.5 degrees) than groups 1 and 2 (5.4 degrees in both, p=0.003). There was no difference in postoperative ROM or blood loss. Conclusions. The sequential addition of imageless navigation of the distal femoral cut and sensor-guided ligament balancing did not confer any benefit to short term PROs, radiographic outcomes, or complication rates over conventional techniques. While overall mechanical alignment of the limb was improved in groups 1 and 2 compared to controls, this did not reach statistical significance. The additive costs of navigation and soft-tissue balancing technologies may not be justified. For figures, tables, or references, please contact authors directly

Accurate evaluation of lower limb coronal alignment is essential for effective pre-operative planning of knee arthroplasty. Weightbearing hip-knee-ankle (HKA) radiographs are considered the gold standard. Mako SmartRobotics uses CT-based navigation to provide intra-operative data on lower limb coronal alignment during robotic assisted knee arthroplasty. This study aimed to compare the correlation between the two methods in assessing coronal plane alignment. Patients undergoing Mako partial (PKA) or total knee arthroplasty (TKA) were identified from our hospital database. The hospital PACS system was used to measure pre-operative coronal plane alignment on HKA radiographs. This data was correlated to the intraoperative deformity assessment during Mako PKA and TKA surgery. 443 consecutive Mako knee arthroplasties were performed between November 2019 and December 2021. Weightbearing HKA radiographs were done in 56% of cases. Data for intraoperative coronal plane alignment was available for 414 patients. 378 knees were aligned in varus, and 36 in valgus. Mean varus deformity was 7.46° (SD 3.89) on HKA vs 7.13° (SD 3.56) on Mako intraoperative assessment, with a moderate correlation (R= 0.50, p<0.0001). Intraoperative varus deformity of 0-4° correlated to HKA measured varus (within 3°) in 60% of cases, compared to 28% for 5-9°, 17% for 10-14°, and in no cases with >15° deformity. Mean valgus deformity was 6.44° (SD 4.68) on HKA vs 4.75° (SD 3.79) for Mako, with poor correlation (R=0.18, p=0.38). In this series, the correlation between weightbearing HKA radiographs and intraoperative alignment assessment using Mako SmartRobotics appears to be poor, with greater deformities having poorer correlation

Purpose. This study aims to evaluate the two-year post-operative clinical outcomes of patients undergoing total knee arthroplasty (TKA) with computer-assisted surgery (CAS) using a pinless navigation system (BrainLAB® VectorVision® Knee 2.5 Navigation System) versus standard CAS. Methods. We analysed prospectively collected data from patients who underwent TKA with CAS from November 2008 to October 2012 over a two year follow-up period by a single senior surgeon. Primary outcome measures include Short-Form 36 (SF-36), Oxford Knee (OKS) as well as Knee Society Scores (KSS). Results. 100 patients were recruited in both arms of the study. Patients in the pinless navigation arm underwent a shorter duration of surgery compared to those in the standard CAS arm with 72±13 min and 83±11 min respectively (p<0.001). There was improvement in OKS for both in pinless navigation arm and standard CAS arm from 34±8 to 18±5 (p<0.001) and 34±9 to 18±5 respectively. This improvement was reflected in the SF-36 as well as KSS. The study did not detect any statistically significant differences in clinical outcomes between the two arms at two-year follow-up. Conclusion. Pinless navigation in TKA with CAS provides improvement in clinical outcomes that are similar to patients who underwent standard CAS with a shorter duration of surgery

INTRODUCTION. Cup orientation of total hip arthroplasty (THA) is critical for dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. But, substantial error under manual technique has been reported specially in revision THA due to a bone loss and poor anatomical landmark. We have used three kinds of navigation systems for cup positioning in primary and revision THA. OBJECTIVES. The purpose of this study is to evaluate the accuracy of navigation in revision THAs. METHODS. Since 2005, consecutive 24 revision THAs were performed with volumetric post-operative CT scan images to measure three dimensional positionings of cups. We implanted cementless hemispherical cups in 14 hips using fluoro-based navigation (FN) system (Stealth Station Tria), in 5 hips using a CT-based navigation (CTN) system (VectorVision CT Hip 3.1) and in 5 hips using fluoro-CT-based navigation (FCTN) system (VectorVision CT Hip 3.5). For all the patients, volumetric post-operative CT scan was performed to measure 3D cup orientation. Using 3D image-processing software (JMM, Japan) we converted all data to radiographic angles to compare different navigation system. RESULTS. The difference from target angles of anteversion was 5.6 ± 4.9 degrees. The absolute value of difference from target angles of inclination was 6.5 ± 3.8 degrees. The system accuracy was 4.2±2.9 in inclination and 4.7 ± 4.1. Accuracy of three navigation system was not significantly different. No postoperative dislocation was observed in this series. No complication related to navigation system was observed, either. CONCLUSION. Cup malpositioning can easily occur with a conventional aligment guide especially in MIS THA due to complexity of a operation. In revision THAs, high incidence of malpositioning of cups and post operative dislocation were reported. We previously reported that navigation system improved the accuracy of acetabular component orientation in MIS THA comparing to manual technique. Conventional CT-based navigation system in revision THAs had two problems. First, it was difficult to get accurate surface registration because a presence of a bone loss prevented surface registration. Secondly, an artifact of CT images due to previous implants during a preoperative planning. For surgical approach (removal of implants), damages of bone easily occurred before surface registration. Damages of bone changed the landmarks for surface registration. These problems might lead the error of CT-based navigation system. On the other hand, FN and FCTN system does not need surface registration around acetabulum. This feature is great advantage to revision THA. Therefore, FN and FCTN system have theoritically would be friendlier for revision THA than CTN system. We also reported FCTN system showed superior accuracy than CTN system [2]. In the present study, there were no significant differences between three kinds of navigation systems. But, our volume of patients was too small to draw differences between systems. We need to continue this study to get more cases. However, in conclusion, an application of navigation system in revision THAs was effective and safe procedure to eliminates postoperative complications such as a malpositioning and post-operative dislocation,

Bilateral sequential total knee replacement was carried out under one anaesthetic in 100 patients. One knee was replaced using a CT-free computer-assisted navigation system and the other conventionally without navigation. The two methods were compared for accuracy of orientation and alignment of the components. There were 85 women and 15 men with a mean age of 67.6 years (54 to 83). Radiological and CT imaging was carried out to determine the alignment of the components. The mean follow-up was 2.3 years (2 to 3). The operating and tourniquet times were significantly longer in the navigation group (p < 0.001). There were no significant pre- or post-operative differences between the knee scores of the two groups (p = 0.288 and p = 0.429, respectively). The results of imaging and the number of outliers for all radiological parameters were not statistically different (p = 0.109 to p = 0.920). In this series computer-assisted navigated total knee replacement did not result in more accurate orientation and alignment of the components than that achieved by conventional total knee replacement

Proper positioning of the acetabular cup deters dislocation after total hip arthroplasty (THA) and is therefore a key focus for orthopedic surgeons. The concept of a safe zone for acetabular component placement was first characterized by Lewinnek et al. and furthered by Callanan et al. The safe zone concept remains widely utilized and accepted in contemporary THA practice; however, components positioned in this safe zone still dislocate. This study sought to characterize current mass trends in cup position identified across a large study sample of THA procedures completed by multiple surgeons. This retrospective, observational study reviewed acetabular cup position in 1,236 patients who underwent THA using computer-assisted navigation (CAS) between July 2015 and November 2017. Outcomes included acetabular cup position (inclination and anteversion) measurements derived from the surgical navigation device and surgical approach. The overall mean cup position of all recorded cases was 21.8° (±7.7°, 95% CI = 6.7°, 36.9°) of anteversion and 40.9° (±6.5°, 95% CI = 28.1°, 53.7°) of inclination (Table 1). For both anteversion and inclination, 65.5% (809/1236) of acetabular cup components were within the Lewinnek safe zone and 58.4% (722/1236) were within the Callanan safe zone. Acetabular cups were placed a mean of 6.8° of anteversion (posterior/lateral approach: 7.0°, anterior approach: 5.6°) higher than the Lewinnek and Callanan safe zones whereas inclination was positioned 0.9° higher than the reported Lewinnek safe zone and 3.4° higher than the Callanan safe zone (Figure 1,2). Our data shows that while the majority of acetabular cups were placed within the traditional safe zones, the mean anteversion orientation is considerably higher than those suggested by the Lewinnek and Callanan safe zones. The implications of this observation warrant further investigation. For any figures or tables, please contact the authors directly

Navigation has shown to improve limb and component alignment during total knee arthroplasty (TKA). However, most navigation systems involve bulky and expensive hardware, increased operative time and cost. A novel hand-held image-free navigation device has been recently approved with the aim to reduce inventory, cost and surgical time with its small size and quick registration features. We aimed to determine limb and component alignment and validate the accuracy of the iPod based navigation system. Intraoperative navigation data for proximal tibia and distal femur cuts, femoral component rotation, limb alignment and component alignment in routine imageless navigation system (Ci Navigation, Brainlab) was compared with the novel iPod-based hand-held navigation system (DASH, Smith & Nephew) in 20 TKAs. Postoperative full-length hip-to-ankle and lateral radiographs were evaluated to measure the hip-knee-ankle (HKA) angle and coronal and sagittal alignment of the femoral and tibial component. The iPod-based navigation system showed good agreement with the Ci Navigation system for limb alignment, tibial and distal femoral cuts in the majority of the limbs despite its quick registration feature. The iPod-based system is hence a positive step towards making navigation systems for TKA more compact, user-friendly, time and cost-effective

Introduction. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the precision and accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. All surgeries were done by single surgeon (KD) using similar technique. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Precision, accuracy, sensitivity and specificity were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. A p value of <0.05 was considered significant for evaluation. Results. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76° (SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high precision and specificity for determining cup abduction and anteversion (precision >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46mm (SD, 5.68) and −1.07mm (SD, 5.75) on radiograph evaluation and 5.41mm (SD, 5.11) and −2.24mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value > 0.2). Radiograph and navigation had a mean difference of 1.01mm (SD, 2.83) for offset measurements and a mean difference of 1.05mm (SD, 4.37) for postop limb length assessment. Discussion. To the best of our knowledge this is the largest single surgeon study of navigated THA. We found that computer navigation assessment of acetabular cup abduction and anteversion and limb length and offset restoration has high probability of predicting correct placement of implants. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

Introduction. Stryker computer navigation system has been used for total knee arthroplasty (TKA) procedures since October 2008 at the Russian Ilizarov Scientific Centre for Restorative Traumatology and Orthopaedics. Material and methods. There have been 126 computer assisted TKA that accounted for 11.5 % of primary TKA within this period (1096 procedures). Arthritis of the knee joints with evident pain syndrome was an indication to TKA surgery. Arthritis of the knee joint of 27 patients (21.4 %) was accompanied by femoral deformity of various etiology with debris found in the medullary canal in several cases. The rest 99 patients (78.6 %) were regular cases of primary TKA. Results. We compared the results of correction of lower limb biomechanical axis with TKA employing navigation and without computer assistance. Regular TKA procedures showed no substantial difference in the correction of biomechanical axis. Complete correction using computer navigation was achieved in 85 % of the cases versus 79 % of the patients without navigation. The deformity up to 3° developed in 14 % of navigated cases and in 17 % of the cases without computer assistance. An error of deformity correction was 3–5° in 4 % of the cases without computer navigation. Those were cases of challenging primary TKA. So the advantages of computer navigation have become evident with greater deformities, and in the cases when intramedullary guide can hardly be used due to severe deformities in the femoral metaphysis and diaphysis, after several operative procedures of osteosynthesis with deformed, obliterating bone marrow canal or presence of debris. Complete correction using computer navigation was achieved in 85.2 % cases versus 42.8 % patients without navigation. Postoperative varus of 2° was observed in 14.8 % cases (valgus or varus deformity of 3° developed in 28.6 % of the cases without computer assistance). Conclusion. What is better: special instrumentation or navigation?. Current instrumentation can provide regular mechanical control of the limb axis and is based on the principles of intramedullary, extramedullary and even double guide placement. Image-free navigation and standard surgical techniques can equally be used for simple cases of primary TKA. Same landmarks are used. These landmarks are determined by a surgeon quite subjectively and can lead to inadequate usage of special instrumentation and computer navigation. However, computer navigation should be used in the cases when intramedullary guide can hardly be used, not desirable or possible. Special instrumentation can fail in setting a valgus angle needed with extraarticular femoral deformity. Navigation allows determining rotation more precisely in the cases when posterior femoral condyles contour (posttraumatic condition, hypoplastic condyles) is distorted. Assessment of ligament balance can be rather subjective when special instrumentation is used. Application of computer navigation is helpful for measurements of flexion and extension gaps sixe and regularity. Computer navigation is contraindicated for contractures and ankyloses of the hip joint. For the rest of the cases the choice of instrumentation is a surgeon's decision

The efficacy of an imageless navigation system in acetabular cup orientation during total hip arthroplasty (THA) is well known. We evaluated the accuracy of placement of the cup and stem and leg extension length with the imageless navigation system. Radiographic evaluation was performed in 69 consecutive patients (75 joints) who underwent primary THA from January 2009 to December 2010. Evaluation of the cup inclination angle (CI), cup anteversion angle (CA), leg extension length (L) and stem anteversion angle (SA) was carried out. SA was evaluated in 21 patients who underwent CT scan after surgery. The accuracy of imageless navigation system was evaluated by comparison of the navigation values obtained during surgery with the radiographic or CT measured values. Good correlation was found between the navigation values and the radiographic or CT measured values in CI (P<0.001, r. 2. = 0.579), CA (P<0.001, r. 2. = 0.607), L (P<0.001, r. 2. = 0.775), and SA (P<0.001, r. 2. = 0.834). The mean absolute difference between navigation and radiograph or CT was 3.3 degrees (range 0.1 to 9.9 degrees) in CI, 4.6 degrees (0.1 to 11.4 degrees) in CA, 3.2mm (0.7 to 8.3) in L, and 3.6 degrees (0.1 to 10 degrees) in SA. The results of this study demonstrated that imageless navigation shows good accuracy not only in cup implantation angle but also in leg extension length and in stem anteversion angle according to radiographic and CT evaluation. We conclude that imageless navigation is a useful tool for performing accurate surgery for THA

Introduction. Proper acetabular cup placement is very important factor for successful clinical results in total hip arthroplasty (THA). Malposition of acetabular cup has been linked to increased rates of dislocation, impingement, pelvic osteolysis, cup migration, leg length discrepancy and polyethylene wear. Recently, some authors reported usefulness of navigation systems to set the acetabular cups with correct position. The purpose of this study is to evaluate the accuracy of acetabular cup placement in THA using computed tomography (CT)-based navigation system. Material and Methods. Subjects were 235 hip joints we performed primary THA using CT based navigation system (Stryker® Navigation System, Stryker Corporation, Kalamazoo, MI, USA) from 2008 to 2014 and could assess the implant position by postoperative CT images. Their average age was 65.1 years (range 35–88). In all cases, non-cemented acetabular cups were implanted. TriAD cups (Stryker®) were used in 31 hips, and Tritanium cups (Stryker®) were used in 15 hips, and Trident cups (Stryker®) were used in 189 hips. Registration in this navigation system used surface matching system. We designed cup implantation using preoperative CT images and 3-dimensional (3-D) templates. The planned position of acetabular cup was in principle 40 degrees of inclination and 20 degrees of anteversion. However, we adjusted the better position of the cups according to pelvic tilt and femoral neck anteversion. When we placed acetabular cups, the position, inclination and anteversion, were measured by navigation system. After surgery, the positions of the cups were measured using postoperative CT images, navigation software and 3-D templates. Postoperative position using CT images were adjusted according to preoperative pelvic plane. The discrepancies between intraoperative navigation data and postoperative CT images data were analyzed as accuracy of navigation system in cup placement. Results. No complications related to navigation procedures were encountered. There was no case with acetabular cup displacement obviously. The discrepancies between intraoperative data and postoperative data were an average difference of 1.6 degrees (SD, 1.4 degrees) for inclination and 2.1 degrees (SD, 1.7 degrees) for anteversion. Discussion and Conclusions. In THA, cup position is very important factor of postoperative long-term success. However, it is not easy to place the acetabular cup with proper position using conventional devices. CT-based navigation system was reported that it had many advantages than previous techniques in preoperative planning, setting the implants and analysis of postoperative data. But in registration with surface matching, learning-curve was pointed out and might be a problem for proper placement of implants. Therefore, we performed this study after some navigation THA cases. In the results of this study, the discrepancies between intraoperative and postoperative data were average 1.6 degrees for inclination and 2.1 degrees for anteversion. The accuracy of navigation system was good in inclination and anteversion of the cups, and there was no complication related it. CT-based navigation system is very useful device

Introduction. Acetabular revision surgery is challenging due to severe bone defects. Burch-Schneider anti-protrusion cages (BS cage: Zimmer-Biomet) is one of the options for acetabular revision, however higher dislocation rate was reported. A computed tomography (CT)-based navigation system indicates us the planned direction for implantation of a cemented acetabular cup during surgery. A large diameter femoral head is also expected to reduce the dislocation rate. The purpose of this study is to investigate short-term results of BS cage in acetabular revision surgery combined with the CT-based navigation system and the use of large diameter femoral head. Methods. Sixteen hips of fifteen patients who underwent revision THA using allografts and BS cage between September 2013 and December 2017 were included in this study with the follow-up of 2.7 (0.1–5.0) years. There were 12 women and three men with a mean age of 78.6 years (range, 59–61 years). The cause of acetabular revision was aseptic loosening in all hips. The failed acetabular cup was carefully removed, and acetabular bone defect was graded using the Paprosky classification. Structural allografts were morselized and packed for all medial or contained defects. In some cases, solid allograft was implanted for segmental defects. BS cage was molded to optimize stability and congruity to the acetabulum and fixed with 6.5 mm titanium screws to the iliac bone. The inferior flange was slotted into the ischium. The upside-down trial cup was attached to a straight handle cup positioner with instrumental tracker (Figure 1) and placed on the rim of the BS cage to confirm the direction of the target angle for cement cup implantation under the CT-based navigation system (Stryker). After removing the cement spacer around the X3 RimFit cup (Stryker) onto the BS cage for available maximum large femoral head, the cement cup was implanted with confirming the direction of targeting angle. Japanese Orthopedic Association score (JOA score) of the hip was used for clinical assessment. Implant position, loosening, and consolidation of allograft were assessed using anterior and lateral radiographies of the pelvis. Results. Fifteen hips had a Paprosky IIIB defect, and one hip had a pelvic discontinuity. JOA score significantly improved postoperatively. No radiolucent lines and no displacement of BS cage could be found in 9 of 15 hips. Consolidation of allografts above the protrusion cage was observed in these patients. Displacement of BS cage (>5mm) was observed in 6 hips and displacement was stopped with allograft consolidation in 5 of 6 hips. The other patient showed lateral displacement of BS cage and underwent revision surgery. Average cup inclination and anteversion angles were 37.7±5.0 degree and 24.6±7.2 degree, respectively. 12 of 16 patients were included in Lewinnek's safe zone. One patient with 32 mm diameter of the femoral head had dislocation at 17 days postoperatively. All patients who received ≥36mm diameter of femoral head showed no dislocation. Conclusions. CT-based navigation system and the use of large femoral head may influence the prevention of dislocation in the acetabular revision surgery with BS cage for severe acetabular bone defects

Background:. While more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned, traditional surgical navigation and robotoics have not been widely adopted. This may be due to the additional time, expense, and complexity associated with this technology. As an alternative, smart mechanical navigation instruments, adjusted on a patient-specific basis, have been introduced to address the problem of cup malorientation. The current study assesses the accuracy of acetabular component alignment using a mechanical navigation instrument. Patients and Methods:. The acetabular component was aligned in 58 consecutive hips in 58 patients using the HipSextant Mechanical Navigation System (Surgical Planning Associates, Inc. Boston, MA). The technique involves using a patient-specific plan and associated software. In planning for surgery, CT data are used to create a 3D model and to define the anterior pelvic plane (APP). A patient-specific HipSextant docking coordinate system is then determined by three points: one just behind the posterior acetabular rim, a second on the lateral side of the ASIS, and a third on the surface of the ilium (Figure 1). The HipSextant itself has two adjustable orthogonal protractors (in-plane and off-plane angle) and two adjustable arms so that the instrument is adjusted for each patient based on their specific anatomy. The instrument docks directly to the pelvis so the recommended orientation of the acetabular component is based on the actual position of the pelvis at the time of component implantation. A direction indicator points in the direction of the planned cup orientation (Figure 2). Cup alignment was further enhanced with the use of a parallel guide to improve parallel visualization (Figure 3). Postoperative cup orientation was measured using a validated two-dimensional/three-dimensional matching method [3,5]. Results:. Cup orientation measurements of the series of 58 THA's performed in the current study using the mechanical navigation instrument showed an error of inclination of 0.63° ± 2.3° [range, −5.3° to 6.0°] and an error of anteversion of 1.0° ± 2.7° [range, −5.3° to 7.0°]. There were no outliers in either anteversion or inclination. Conclusion:. The current study demonstrates that the mechanical navigation instrument shows excellent cup alignment accuracy in a consecutive series of patients. This accuracy, compared to traditional navigation and robotic systems, may be due to the wide-based nature of the docking mechanism and the eliminate of the cumulative errors of registration and tracking inherent to more complex systems

Introduction. Failures in total knee arthroplasty (TKA) have been associated with overall lower limb malalignment and component malposition. Although traditional computer navigation systems improve component placement, they require fixation of the femoral and tibial reference arrays for software recognition using anchoring pins. This increases the risk of bony fracture, pin sites infection and osteomyelitis. Aim. This study aims to evaluate the accuracy of a new hand held navigation system (BrainLAB® Dash® Navigation system) that will avoid these complications. Materials and Methods. Power analysis was done prior to the conduct of this study. Two hundred patients diagnosed with tricompartmental osteoarthritis and underwent total knee arthroplasty by a senior surgeon were included in this study. 100 patients underwent TKA using the hand held navigation system while the other 100 patients underwent TKA using 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 degrees for the HKA and 90 ± 3 degrees for both the CFA and CTA. Results. There was no difference in the mean HKA, CFA and CTA between the hand held navigation group and the conventional group. 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 ± 9 minutes and 87 ± 15 minutes in the hand held navigation and conventional group respectively (p0.001). Conclusion. Dash® is an effective intraoperative tool to reduce the duration of surgery while concurrently reducing the proportion of outliers. The authors recommend its routine use in TKA

Background. Bone preservation is desired for future revision in any knee arthroplasty. There is no study comparing the difference in the amount of bone resection when soft tissue balance is performed with or without computer navigation. To determine the effect on bony cuts when soft tissue balance is performed with or without use of computer software by standard manual technique in total knee arthroplasty. One hundred patients aged 50 to 88 years underwent navigated TKR for primary osteoarthritis. In group A, 50 patients had both soft tissue release and bone cuts done using computer-assisted navigation. In group B, 50 patients had soft tissue release by standard manual technique first and then bone cuts were guided by computer-assisted navigation. In group A the mean medial tibial resection was 5 ± 2.3 mm and lateral was 8 ± 1 mm compared to 5 ± 2 mm (P = 0.100) and 8 ± 1 mm respectively in group B (P = 0.860). In group A the mean medial femoral bone cut was 9 ± 2.9 mm and lateral was 8 ± 2 mm as compared to 9.5 ± 2.9 mm (P = 0.316) and 10 ± 2.2 mm respectively in group B (P = 0.001). Average prosthesis size was 6 (range 3 to 8) in group A as compared to size 5 (range 2 to 7) in group B. Average navigation time in group A was 102 minutes (range 45 to 172) and in group B was 83 minutes (range 42 to 165, P = 0.031). Our results show that performing soft tissue release and bone cuts using computer- assisted navigation is more bone conserving as compared to manual soft tissue release and bone cuts using computer navigation for TKR, thus preserving bone for possible future revision surgery

Introduction. Computer-assisted navigation is an established tool in hip and knee arthroplasty. This technology was introduced with the goals of greater precision in bone preparation and implant placement, potentially leading to improved clinical outcomes. Various navigation protocols exist, many of which require placement of temporary percutaneous pins in the operative field. Risks of pin placement have not been described. Methods. We conducted a retrospective review of 352 consecutive patients undergoing elective hip and knee surgery using computer-assisted navigation between January 2013 and December 2015, all with a minimum follow-up of 90 days. Navigation pins were placed using a standardized protocol into the iliac crest for hip arthroplasty or into the femoral and tibial diaphysis for knee arthroplasty. Postoperatively, all patients were allowed to weight bear as tolerated. Patient records were reviewed for operative details and clinical outcomes. Outcome measures included any pin site complications including direct neurovascular damage, fracture through a pin site, and pin site infection. Results. A total of 968 pin sites were included in the study. Two pin site complications were reported (0.21%). No neurovascular injuries were reported from pin placement (0.0%). No periprosthetic fractures through a pin site were reported (0.0%). Two patients developed a pin-site infection with purulent drainage (0.21%), both of which resolved with oral antibiotics and local wound care. Conclusion. Potential benefits of navigation in hip and knee arthroplasty are still being investigated, however the placement of pins required for this technology are associated with minimal patient morbidity and should be considered a safe intervention with minimal added risk

Over the past decades, computer-aided navigation system has experienced tremendous development for minimising the risks and improving the precision of the surgery. Nowadays, some commercially-available and self-developed surgical navigation systems have already been tested and proved successfully for clinical applications. However, all of these systems use computer screen to render the navigation information such as the real-time position and orientation of the surgical instrument, virtual path of preoperative surgical planning, so that the surgeons have to switch between the actual operation site and computer screen which is inconvenient and impact the continuity of surgery. In recent years, Augmented Reality (AR)- based surgical navigation is a promising technology for clinical applications. In the AR system, virtual and actual reality are mixed, offering real-time, high-quality visualisation of an extensive variety of information to the users. Therefore, in this study, a pilot study of a surgical navigation system for orthopaedics based on optical see-through augmented reality (AR-SNS) is presented, which encompasses the preoperative surgical planning, calibration, registration, and intra-operative tracking. With the aid of AR-SNS, the surgeon wearing the optical see-through head-mounted display can obtain a fused image that the 3D virtual critical anatomical structures are aligned with the actual structures of patient in intra-operative real-world scenario, so that some disadvantages of the traditional surgical navigation are overcome (For example, surgeon is no longer obliged to switch between the real operation scenario and computer screen), and the safety, accuracy, and reliability of the surgery may be improved

Purpose of the study: Revision total knee arthroplasty (rTKA) is becoming a routine procedure. The technical problems are greater than with a first-intention implantation because of the potential malposition of the initial implants, loss of bone stock, and prior ligament injury. It could be hypothesised that as for implantation of a primary TKA, navigation might improve the quality of the implantation. Material and methods: We used the Orthopilot™ (Aesculap, RFA) navigation system for first-intention TKA. The standard software was used for revisions. The acquisition of the anatomic and kinematic data was performed while the initial implants in situ. The implants were then removed. Any bone recuts required were done under navigation control. The size of the implants and their thickness were determined after digital simulation of residual laxity; ligament balance was adapted from this data. The system does not allow navigation for centromedullary stem extensions nor for filling potential bone defects. Sixty patients underwent the procedure. There was a comparative series of 30 patients who underwent manual conventional revision using an instrumentation guided by the centromedullary femoral and tibial stems. The quality of the implantation was determined by measuring the alignment of the limb and the orientation of the implants on the postoperative x-rays. Outcome was analysed with Student’s t test and the chi-square test with p< 0.05 taken as significant. Results: There was a significant improvement in quality of the implantation for all radiographic criteria in the navigation group. Limb alignment was restored in 88% of the navigated cases and 73% of the conventional cases. Similar differences were observed for femoral and tibial implant position on the lateral and AP views. Discussion: The objectives set for implant orientation and ligament balance can be met with the navigation system for the majority of knees, with a rate similar to that achieved with primary implantation. The navigation system is an appreciable aid for these often difficult procedures where visual information can be misleading. Conclusion: The navigation system used here facilitated revision TKA

Introduction. The KneeAlign2 (OrthAlign, Inc., Aliso Viejo, CA) is a portable accelerometer-based navigation device for use in performing the distal femoral resection in total knee arthroplasty (TKA). This device works as a computer-assisted surgical system. It does not require the use of a large console for registration and alignment feedback.(image1,2). Purpose. The aim of this study was to investigate the accuracy in positioning the femoral component and the presense of a learning curve in conducting TKA using this device. Materials and methods. From May 2015 to March 2016, 60 knees underwent a primary TKA using a portable accelerometer-based navigation device for performing the distal femoral resection. These TKAs were devided in two groups. Group1: operated by surgeon of experience using the KneeAlign2 more than 30 cases. Group2: operated by surgeons of experience using the KneeAlign2 less than 30 cases. Standing AP hip-to-ankle radiographs were obtained postoperatively. Positioning of the femoral component was measured by the radiographs. Outlier in coronal alignment were defined as >3°. The radiographic results and operation time were compared between the groups. Students t-test was performed to assess the statistical analysis (p<0.05). Result. There was no outlier and all patients had an alignment within 90±3°to the femoral mechanical axis in the coronal plane in both groups. The mean deviation(absolute values) from the neutral alignment of the femoral component were 1.5±0.5 in group1 and1.2±0.7 in group2. There was no statistical significance between the groups. Average operation time was 106.2 minutes in group1 and 108.5 minutes in group2. There was no statistical significance between the groups. There were no complications during the surgery associated with the navigation device. Conclusion. This portable navigation device is highly accurate in positioning the femoral component in TKA. And as the learning curve for using this device does not be observed, this portable navigation is easy to handle even for beginner users. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Background. The literature quotes up to 20% dissatisfaction rates for total knee replacements (TKR). Swedish registry and national joint registry of England and Wales confirm this with high volumes of patients included. This dissatisfaction rate is used as a basis for improving/changing/modernising knee implant designs by major companies across the world. Aim. We aimed to compare post TKR satisfaction rates for navigated and non navigated knees. Methods. This was a retrospective analysis of prospectively collected data. All patients undergo comprehensive preoperative evaluation and comprehensive consent process and same rehabilitation protocols are followed as standard practice. Two groups were established depending on whether surgery was performed with or without computer navigation. We included 229 patients in each group. There were nine bilateral cases in the navigated group giving a total of 238 knees. Both groups were similar at the time of surgery (navigated: 68 years (sd9);; BMI 32.46;; (sd5.19);; OKS: 42.2 (sd7.5);; non-navigated: 70 years (sd9);; BMI 32.36;; (sd5.26);; OKS: 42.4 (sd7.3)). The satisfaction rates are recorded as very satisfied, satisfied, unsure or dissatisfied. Results. Of the 238 navigated knees 227 (95.4%) were very satisfied or satisfied;; while of the 229 non-navigated knees 205 (89.5%) were very satisfied or satisfied. Only 3 (1.3%) navigated knees and 9 (3.9%) non-navigated knees were dissatisfied. Seven (2.9%) navigated knees and fifteen (6.6%) non-navigated knees were unsure. The navigated group showed better satisfaction (p=0.049) compared to the non-navigated group and better satisfaction than previously published satisfaction rates [3]. When combining dissatisfaction and unsure responses the navigated group again performed significantly better than the non-navigated group (p=0.021). Satisfaction rates were also compared with published literature, which suggest that 82–89% of TKA patients are satisfied and that navigation has no effect on satisfaction [3]. Our data for the non-navigated knees are similar to high end of the published data. This goes to show that comprehensive education of patients, high volume surgeons and elective arthroplasty unit along with comprehensive consent process can achieve best results. We have also shown that navigation influences satisfaction rates. There were no differences in 6 week OKS data with scores of 28.1 (sd= 8.0) and 28.8 (sd=7.8) for navigated and non-navigated groups(p=0.623), The same was also true for range of flexion/extension (92.1° [sd=13.4°& 91.3° [sd=14.1°, p=0.360) and length of hospital stay in days (median=5 [min=2, max=37], median=5 [min=2, max=19], p=0.959);; for navigated and non-navigated groups respectively. Of those navigated knees reported as ‘dissatisfied’ and ‘unsure’, 50.0% (5 knees) were due to pain in the knee. For non-navigated knees, 66.7% (16 knees) stated knee pain as the reason for being ‘dissatisfied’ or ‘unsure’. Conclusion. A modern elective arthroplasty service can deliver high satisfaction rates. Use of computer navigation further improves even the best conventional satisfaction rates. Industry should promote better surgical techniques rather than bringing out new implants to improve satisfaction rates in total knee replacements

Introduction. Component positioning is of great importance in total hip arthroplasty (THA) and navigation systems can help guide surgeons in the optimal placement of the implants. We report on a newly developed navigation system which employs an inertial measurement unit (IMU) to measure acetabular cup inclination and anteversion. Aims. To assess the accuracy of the IMU when used for acetabular cup placement and compare this with an established optical navigation system (ONS). Methods. At the time of acetabular cup impaction, the IMU and ONS were separately mounted on the impactor handle. Cup inclination and anteversion as measured by each device were recorded. Post-operative CTs were acquired for all patients and used to determine the final cup position. Results. Data were recorded for a total of 100 patients undergoing THA; 51 had a direct anterior approach (DAA) and 49 had a posterior approach (PA). In the DAA group, the mean difference in IMU versus CT measured cup inclination was −0.7°(range −6 to 8º) compared with mean difference of ONS versus CT of −2° (range −8 to 5º). Mean difference in IMU versus CT measured anteversion was − 1.3° (range −10 to 10º) compared with a mean difference of −1.1° (range −23 to 20º) between ONS and CT. In the PA group, mean difference in IMU versus CT inclination was 1.3º (range −8 to 6º) compared with mean difference between ONS versus CT of 1.6° (range −5 to 7º). Mean difference in anteversion was 3.7° (range −7 to 16º) between IMU and CT and 7.3° (range −3 to 19º) between ONS and CT. Conclusion. The novel IMU can be used to accurately determine the position of the acetabular cup at the point of impaction, demonstrating comparable accuracy with an established navigation system in the direct anterior approach, and even greater accuracy in the posterior approach

The optimal overall lower extremity and component alignment in total knee arthroplasty (TKA) has recently been questioned, yet the majority of studies demonstrate TKA positioning to effect the rate of implant loosening, polyethylene stresses, knee kinematics, and gait. Most commonly, extramedullary tibial and intramedullary femoral alignment guides are used to set coronal alignment in TKA, but these “conventional” methods have a limited degree of accuracy. The goal of obtaining more precise and accurate component positioning has led to the development of computer-assisted surgical (CAS) techniques. Although numerous comparative studies have shown significant improvements with the use of CAS techniques, concerns over increased operative times, large capital costs, and the learning curve associated with their use have limited their widespread acceptance. Recently, handheld navigation devices have been introduced with the goal of providing the accuracy of large-console CAS systems in an easy-to-use manner. These devices rely on accelerometer-based navigation to set cutting guide alignment relative to the mechanical axes of the femur and tibia. Unlike most CAS systems, handheld navigation systems avoid the use of additional pin sites and reference arrays in the femur and tibia, do not require a large computer with an infrared camera, and thus eliminate intraoperative line of site issues between the camera and tracking arrays. Several investigations have demonstrated handheld navigation devices to provide the same degree of alignment accuracy as large-console CAS systems, thus improving the ability of a surgeon to achieve their intraoperative targets for coronal alignment during TKA

The purpose of this study was to evaluate in vivo fit and fill analysis of tapered wedge-type stem in total hip arthroplasty (THA) with computed tomography (CT)-based navigation system. 100 THAs were all performed through the posterolateral approach, with patients in the lateral decubitus position. Each cohort of 50 consecutive primary cementless THAs with was compared with and without CT-based navigation system. The post-operative antero-posterior (AP) hip radiographs were obtained two weeks after the operation. All radiographic fit and fill measurements in the proximal and distal areas were analyzed by two of the authors who were both blinded to the use of CT-based navigation system. The type of the fit in the cementless stem was divided into three types. The fit of the stem was classified as Type I, if there was both proximal and distal engagement (maximum proximal to distal engagement difference of 2 mm or greater), Type II when there was proximal engagement only, and Type III when there was distal engagement only. The fill parameters such as mean stem-to-canal ratios and mean minimum and maximum gaps between the stems to the cortical bone in proximal and distal sections were compared. There was a significantly better overall canal fit obtained by THA with CT-based navigation system compared to without the navigation system (p<0.01). With CT-based navigation system, 42 of 50 stems (84%) were categorized as Type I fit compared to 31 of 50 stems (62%) without the navigation system. As to Type II fit, There are significantly more stems without the navigation system (26%) compared to with it (12%). There were better canal fills of the stems obtained by THA with CT-based navigation system both in proximal (94%) and distal sections (88%) of the femur compared to without the navigation system (proximal 88%/distal 82%) (p<0.05). Excellent radiographic fit and fill has been previously reported to potentially correlate with improved clinical outcomes. The stems obtained by THA with CT-based navigation system had a significantly better canal fit demonstrated by higher proportion of Type I and lower proportion of Type II fits, compared to without the navigation system. The stems with the navigation system had also significantly better proximal and distal canal fill

Computer navigation is an attractive tool for use in total knee arthroplasty (TKA), as it is well known that alignment is important for the proper function of a total knee replacement. Malalignment of the prosthetic joint can lead to abnormal kinematics, unbalanced soft-tissues, and early loosening. Although there are no long term studies proving the clinical benefits of computer navigation in TKA, studies have shown that varus alignment of the tibial component is a risk factor for early loosening. A handheld, accelerometer based navigation unit for use in total knee replacement has recently become available to assist the surgeon in making the proximal tibial and distal femoral cuts. Studies have shown the accuracy to be comparable to large, console-based navigation units. Additionally, accuracy of cuts is superior to the use of traditional alignment guides, improving the percentage of cuts within 2 degrees of the desired alignment. Because the registration is based on the mechanical axis of the knee, anatomic variables such as femoral neck-shaft angle, femoral length, and presence of a tibial bow do not affect the results. The handheld aspect of this navigation unit allows its use without additional incisions or array attachment. Furthermore, the learning curve and usage time is minimal, supporting its use in primary TKA

We have investigated the accuracy of placement of the femoral component using imageless navigation in 100 consecutive Birmingham Hip Resurfacings. Pre-operative templating determined the native neck-shaft angle and planned stem-shaft angle of the implant. The latter were verified post-operatively using digital anteroposterior unilateral radiographs of the hip. The mean neck-shaft angle determined before operation was 132.7° (118° to 160°). The mean planned stem-shaft angle was a relative valgus alignment of 9.7° (. sd. 2.6). The stem-shaft angle after operation differed from that planned by a mean of 2.8° (. sd. 2.0) and in 86% of cases the final angle measured within ± 5° of that planned. We had no instances of notching of the neck or varus alignment of the implant in our series. A learning curve was observed in the time taken for navigation, but not for accurate placement of the implant. Navigation in hip resurfacing may afford the surgeon a reliable and accurate method of placement of the femoral component

Introduction:. Since2007, we have used CT-based fluoroscopy-matching navigation system (Vector Vision Hip Ver.3.5.2, BrainLAB, Germany) in revision total hip arthroplasty. This system completes the registration procedure semi-automatically by matching the contours of fluoroscopic images and touching 3 adequate points to the contours of 3D bone model created in the computer. Registration procedure using fluoroscopic figures has finished before making surgical incision. It needs no elongation time during the operation. The objective of this study was to evaluate the accuracy of CT-based fluoroscopy-matching navigation system in revision THA. Material and method:. We analysed the acetabular cup in consecutive 33 hips with both intra-operative and post-operative alignment data (based on navigation system and CT evaluation) We further compared these measurements with results from primary THA. Data for primary THA were therefore obtained from 40 consecutive patients who underwent primary THA between August 2007 and May 2013 using the same navigation system by postero-lateral approach. We aimed the cup angle for Revision THA as following, the inclination: 40 degrees, the anteversion: 20 degrees Anteversion on the navigation system must be adjusted by the pelvic tilt. Results:. There was one dislocation in 33 Revision THAs. There was no other obvious complication (nerve palsy, VTE and Infection). The all cup alignments were within 7 degrees from the preoperative orientation. In the Revision THA group the differences between the intra- and post-operative measurement of cup inclination were 2.3 ± 1.9 degrees. The differences of cup anteversion were 2.7 ± 2.5 degrees. In the primary THA group, the differences between the intra- and post-operative measurement of cup inclination were 1.9 ± 2.1 degrees. The differences of cup anteversion were 2.1 ± 2.5 degrees. There was no significant difference with two groups. Discussion:. CT-based navigation THA is very useful for severe deformity of hip osteoarthritis. We had used CT-based navigation system (landmark matching) since 2003. It needs some technical skills to improve the accuracy of landmark matching. The registration with CT-based fluoroscopy-matching navigation system is much easier and more simple than with landmark matching navigation system. CT images of revision patients included metal artifacts caused by implants. However this system is not so affected by metal artifacts. And we found this system provided high accuracy even in revision THA

Malalignment of more than three degrees in coronal plane was associated with poor outcome. Most of the alignment occurred in the tibial coronal plane alignment. Computer assisted surgery (CAS) in total knee arthroplasty (TKA) aimed to minimize malalignment. Most of the CAS-TKA results were using infrared tracking system. Electromagnetic navigation in total knee arthroplasty was developed in recent years. It aimed at high accuracy and easy signal detection. However, there was limited result being published. From August, 2006 to March, 2008, 50 patients had TKA performed with Medtronic electromagnetic navigation (EM CAS-TKA). The results were compared with 50 matched patients who had TKA performed with conventional technique. The post-operative limb alignments were compared. More than three degrees deviation from neutral alignment was defined as outliers. There was no significant difference in the age, sex distribution, pre-operative range of motion and pre-operative deformity between the two groups. EM-CAS TKA group had significantly less deviation from neutral in the tibial coronal plane (p < 0.001) and femoral sagittal plane (p = 0.006) plane than conventional group. There was no significant difference in femoral coronal plane and tibial sagittal plane alignment between the two groups (p = 0.069 and 0.185 respectively). There were significantly more outliers (> 3 malalignment) in tibial coronal plane (p = 0.004) and femoral sagittal plane (p = 0.049) in conventional group than EM-CAS TKA group. There was no significant difference in the outliers in femoral coronal plane, and tibial sagittal plane (p = 1 and 0.1 respectively). The mean tourniquet time of the EM-CAS TKA group, 95.7 minutes (range, 65 to 126 minutes), was significantly higher than the conventional group, mean 72.1 minutes (range, 45 to 120 minutes), p value < 0.001. There was no pin tract complication and infection in the electromagnetic navigation group. Electromagnetic navigation had improved the tibial coronal plane and femoral sagittal plane alignment in total knee arthroplasty with less outlier. Better alignment may improve the survival of the prosthesis. The learning curve is short and it is easy to handle. Electromagnetic navigation has the potential application in minimally invasive total knee arthroplasty

Aims

Nearly 99,000 total knee arthroplasties (TKAs) are performed in UK annually. Despite plenty of research, the satisfaction rate of this surgery is around 80%. One of the important intraoperative factors affecting the outcome is alignment. The relationship between joint obliquity and functional outcomes is not well understood. Therefore, a study is required to investigate and compare the effects of two types of alignment (mechanical and kinematic) on functional outcomes and range of motion.

Computer navigation was introduced in Australia in 2000, initially with the use of pre-operative computer scans and then later with image free systems. In 2003 the AOA – NJRR began collecting data for knee replacement performed with computer navigation. Meta analysis of the literature has shown better coronal and sagittal plane alignment in total knee arthroplasty performed with computer navigation as opposed to standard instrumented knee replacement. At present, however, there is no data on improved outcomes or reduced revision rates. Information was requested from the AOA – NJRR on the use of computer navigation for both uni-compartmental and total knee replacements. This included numbers of navigated knees done per year as well as revision rates and reasons for revisions of knees performed by computer navigation surgery. Since data collection began there has been 2,651 computer assisted total knee replacements performed which is 4.1% of the total number of knee replacements in this time period. There has been a steady increase in the last three years in the use of computer navigation. There has been an increased number of computer navigated knees performed in the private hospital sector as opposed to the public hospitals and there is a state by state variation in the uptake of navigation. The revision rate per 100 observed ‘component’ years at three years is 2.8 for non computer assisted and 2.5 computer assisted surgery. This is not statistically significant. There is no difference in the early complication rate leading to revision. The use of computer navigation could be expected to reduce the long term revision rates of knee arthroplasty due to better alignment and potentially less wear. In the short term there is no significant revision rate between the two methods of performing TKR particularly with regard to infection or fracture

Introduction: Computerised navigation has been a recent addition to the armamentarium of both total hip and knee arthroplasty, following earlier experiences in neurosurgery and trauma. The first navigation devices available for total hip arthroplasty (THA) provided the surgeon with information on acetabular component placement. The current generation of hip navigation packages provide guidance with both acetabular and femoral component placement, as well as information on restoration of leg length and offset. Method: We used the Stryker hip navigation system. Results: We have performed in excess of 60 total hip replacements using imageless computerised hip navigation through a number of approaches including: standard posterior, mini-posterior and double-incision approaches. Our results show an increase in accuracy of component placement using computerised navigation as compared with conventional alignment guides, which is in keeping with previous cadaver and clinical studies. The accuracy of the navigation unit appears independent of incision type or size. The limiting factor with all current forms of navigation is the requirement for rigid tracker fixation to both the pelvis and the femur. Until recently, this required insertion of threaded pins and soft-tissue dissection. Loosening of pins or inadvertent pressure on a tracker may lead to false readings and the potential for inaccurate readings. The introduction of percutaneous tracker fixation has decreased problems associated with this. The streamlining of the software program, as well as the introduction of smart tools has decreased the extra time taken to 10 minutes per case. Conclusion: The first generation of hip navigation units have been able to provide the surgeon with additional information with regard to the normal patient anatomy and allow the surgeon to more accurately place both the femoral and acetabular components. In this introductory period we have seen massive advancements with hardware (trackers and cameras have doubled in accuracy and halved in size) and the software has become more intuitive and less intrusive in the surgical process. We now await clinical studies that confirm that the use of navigation devices in total hip arthroplasty provide clinical advantages to the patient in the form of decreased dislocation rates, more accurate leg length and offset correction and better functional outcome. Navigation is being increasingly used as an adjunct to minimally invasive surgery, ensuring more accurate component position in the face of limited visibility

Total knee arthroplasty (TKA) has become one of the most successful procedures in orthopedics, and its survival rates are reportedly greater than 90% after 15 years. Malpositioning of the component, however, can lead to various failures, such as aseptic loosening, instability, polyethylene wear, and patellar dislocation. Navigation systems for TKA have been developed to improve postoperative alignment. Many clinical and experimental studies of these navigation systems have shown that the accuracy of implanted components has improved. We have compared the alignment of 150 total knee replacements implanted using a computed tomography-based navigation system and using the conventional alignment guide system when performed by a single surgeon. The knees were evaluated using full-length weight-bearing anteroposterior radiographs and computed tomography scans. For the navigated group, the average hip-knee-ankle angle, the femoral component angle to the femoral mechanical axis, and the tibial component angle to the mechanical tibial axis were 179.5, 89.4 and 89.7 degrees. The rotational femoral and tibial component angles to the planning axis were 0.6 and 0.3 degrees. The ideal angles of all alignments in the navigated group were obtained at significantly higher rates than in the conventional group. Our results demonstrated significant improvements in component positioning with CT-based navigation system, especially with respect to rotational alignment. Recently, we established a new method for 3D reconstruction from postoperative CT images in order to accurately measure the alignment of the component relative to any designed plane. The results showed that the discrepancy between the two-dimensional and three-dimensional evaluations was 0.3 ± 1.8 (−2.7–3.4) degrees. The coronal femoral angle for 36 knees (97.3%) and the coronal tibial angle for all the 37 knees (100%) were obtained within 3 degrees from the optimal angle. It is possible to measure the postoperative alignment for TKA more accurately on the basis of the defining plane. Three-dimensional analysis is necessary to evaluate the accuracy of the navigation system. We conclude that navigation system is a very useful tool for achieving proper postoperative alignment. Controversy still exists regarding accuracy in rotational alignment with image-free navigation, but our results showed that CT-based system significantly improved accuracy of rotational alignment. We should keep using and improving the systems to establish more simplified and accurate systems

Introduction. Orientation of the acetabular component in total hip arthroplasty has been shown to influence component wear, stability, and impingement. Freehand placement of the component can lead to widely variable radiographic outcomes. Accurate abduction, in particular, can be difficult in the lateral decubitus position due to limited ability to appreciate and control positional obliquity of the pelvis. A CT-based mechanical navigation device has been shown to decrease cup placement error. This is an independent report of a single-surgeon's radiographic results using the device to control cup abduction. Patients and Methods. Sixty-four (64) consecutive elective THRs in 58 patients were performed via a supercapsular percutaneously-assisted (SuperPATH) surgical approach. Intraoperatively, the acetabular components were aligned with the aid of the CT-based mechanical navigation device (HipXpert; Surgical Planning Associates, Medford, MA). The cup orientation was then further adjusted to ensure that the anterior rim of the acetabular component was not prominent to avoid psoas impingement. Postoperatively, radiographic abduction was measured on standing postoperative radiographs. Results. Measured on standing postoperative radiographs, the cup radiographic abduction angle averaged 42.7° with a standard deviation of ± 3.9° and a range of 35° to 51°. Conclusions. Total hip arthroplasty using a CT-based navigation device as a guide for abduction led to cup implantation within a very narrow abduction range. This navigation device deserves more widespread interest and study, as acetabular component malposition remains a major concern in THR

Introduction: Modern navigation technology appears to be acquiring an established place in the fields of total knee arthroplasty. This technology helps the surgeon to apply his manual skills with greater precision and thus more effectively, and its positive impact on the quality of surgical treatment has already been demonstrated. The Surgetics navigation system described in this paper shows that the Technology can be adapted to the requirements of daily surgical practice, without compromising its utility to the surgeon. The Surgetics navigation system: The Surgetics navigation system represents a multifunctional tool, that can be used in a lot of fields in orthopedic surgery. For every special use as prosthesis, osteotomies ore ACL-replacement, the hard- and software is adapted thus not any compromise should be accepted for the surgical procedure. In total knee prostheses navigation no ct- scan is needed preoperatively, the patented bone morphing procedure is entering all the anatomic datas to the computer for an absolutely correct positioning of the implant. Consequently the pre- and intraoperative inputs are reduced to a minimum. Material: To evaluate the advantage of the Surgetics navigation system in total knee prosthesis, the technical datas of a non constrained knee prostheses with rotational platform (ESKA) had been entered in the system. The patient datas, concerning size of the knee joint, leg axes, center of rotation of the hip joint and ligament balance are transmitted by rigid bodies and a pointer with 6 reflecting markers each and a stereo infrared camera. The rigid bodies are fixed by two thin Steinmann-nails each in the tibial and femoral bone. On a monitor each step of the bone morphing and the surgical procedure is shown. Thus the bonecutting guides are placed in an absolutely correct position. The extension – and the flexion gap is presented as well for a precise ligament balancing. The additional time for using this system is not extending 15 minutes. Methods: 50 ESKA total knee prosthesis with rotational platform have been implanted with standard instrumentation and another 50 with the use of the Surgetics navigation system. In both groups the reason fore surgery has been nearly identic. In 92% the patients suffered from arthritis. More varus than valgus deformities have been seen. The range of deformity went up to 25 degrees.In 8% posttraumatic deformities with consecutive arthritis leaded to surgery. Preoperative X rays of the whole leg in a standing position have been taken, the shifting of the bearing axes in comparison to the center of the knee joint has been determined. The maximum of this shifting was 6.3 cm. The HSS score has been used to describe the clinical findings pre- and postoperativly. In 38 cases of the S- group and in 39 of the N- group the joint was inserted cementless. 2 in the s-group and 1 in the n-group in a hybrid technic, the rest cemented. Results: The follow up time in both groups ranged from 6 month to one year.Because it has not been the purpose of this paper to report on long time clinical results or survivership, this short follow up time seems to be acceptable for the evidence upon the value of a navigation system.The postoperative x- rays showed a correction of the bearing axes of the leg in relation to the center of the knee joint in a 4 degree corridor in 94,6% for the N – group and in 69,9% in the S- group. Two failures in the N-group came from a change of position of the rigid bodies during surgery due to pushing them by lack of caution. Conclusion: The surgetics navigation system is a technical help for the orthopedic surgeon, improving the radiological and clinical results in knee arthroplasty. The correction of the bearing axes in the 4 degree corridor is significantly higher in the N-group then in S-group. This has as well an important influence on the clinical outcome. The HSS score by first impression differs by 6 points. The use of the system is economically reasonable,because preoperative ct- scan is not needed and the time of surgery is not extended more than 15 minutes.The Surgetics navigation system with its sophisticated software is leading the surgeon visually through the bone morphing procedure, the bone cutting process and the ligament balancing step by step

Glenoid replacement is a manual bone removal procedure that can be difficult for surgeons to perform. Surgical robotics have been utilized successfully in hip and knee orthopaedic procedures but there are no systems currently available in the shoulder. These robots tend to have low adoption rates by surgeons due to high costs, disruption of surgical workflow and added complexity. As well, these systems typically use optical tracking which needs a constant line-of-sight which is not conducive to a crowded operating room. The purpose of this work was developing and testing a surgical robotic system for glenoid replacement. The new surgical system utilizes flexible components that tether a Stewart Platform robot to the patient through a patient specific 3D printed mount. As the robot moves relative to the bone, reaction loads from the flexible components bending are measured by a load cell allowing the robot to “feel” its way around. As well, a small bone burring tool was attached to the robot to facilitate the necessary bone removal. The surgical system was tested against a fellowship-trained surgeon performing standard surgical techniques. Both the robot and the surgeon performed glenoid replacement on two different scapula analogs: standard anatomy and posterior glenoid edge wear referred to as a Walch B2. Six of each scapula model was tested by the robot and the surgeon. The surgeon created a pre-operative plan for both scapula analogs as a target for both methodologies. CT scans of the post-operative cemented implants were compared to the pre-operative target and implant position and orientation errors were measured. For the standard shoulder analogs the net implant position and orientation errors were 1.47 ± 0.48 mm and 2.57 ± 2.30° for the robot and 1.61 ± 0.29 mm and 5.04 ± 1.92° for the surgeon respectively. For the B2 shoulders, the net implant position and orientation errors were 2.16 ± 0.36 mm and 2.89 ± 0.88° for the robot and 3.01 ± 0.42 mm and 4.54 ± 1.49° for the surgeon respectively. The new tracking system was shown to be able to match or outperform the surgeon in most metrics. The surgeon tended to have difficulty gauging the depth needed as well as the face rotation of the implant. This was not surprising as the reaming tool used by the surgeon obscures the view of the anatomy and the spherical cutter hinders the ability to index the tool. The robot utilized only one surgical tool, the bone burr, precluding the need for multiple instruments used by the surgeon to prepare the glenoid bone bed. The force-space navigation method can be generalized to other joints, however, further work is needed to validate the system using cadaveric specimens