Introduction. The use of technology, such as navigation and robotic systems, may improve the accuracy of component positioning in total hip arthroplasty (THA) but its impact on patient reported outcomes measures (PROMs) remains unclear. This study aims to identify the association between intraoperative use of technology and patient reported outcomes measures (PROMs) in patients who underwent primary total hip arthroplasty (THA). Methods. We retrospectively reviewed patients who underwent primary THA between 2016 and 2020 and answered a post-operative PROM questionnaire. Patients were separated into three groups depending on the technology utilized intraoperatively: navigation, robotics, or no technology (i.e. manual THA. The Forgotten Joint Score (FJS-12) and Hip Disability and Osteoarthritis Outcome Score, Joint Replacement (HOOS, JR) were collected at various time points (FJS: 3m, 1y, and 2y; HOOS, JR: pre-operatively, 3m, and 1y). Demographic differences were assessed with chi-square and ANOVA. Mean scores between all groups were compared using univariate ANCOVA, controlling for observed demographic differences. Results. Of the 1,960 cases included, 896 navigation, 135 robotics, and 929 manual. There was a significant statistical difference in one-year HOOS, JR scores (85.23 vs. 85.95 vs. 86.76; p=0.014) and two-year FJS-12 scores (64.72 vs. 73.35 vs. 74.63; p=0.004) between the three groups. However, they did not exceed the mean clinically important difference (MCID) at any time period. Short and long-term PROMs significantly differed between navigation and manually performed cases (FJS 3m: p=0.047; FJS 2y: p=0.001; HOOS, JR 1y: p=0.004). Two-year FJS-12 scores statistically differed between navigation and robotics (p=0.038). There was no statistical difference in either FJS-12 or HOOS, JR scores between robotics and manual THA groups at all time points (FJS 3m:p=0.076, 1y:p=0.225, 2y:p=0.793; HOOS, JR preop:p=0.872, 3m:p=0.644, 1y:p=0.531). Conclusion. Statistical differences observed between all modalities are not likely to be clinically meaningful with regards to early patient reported outcomes. While intraoperative use of technology may improve the accuracy of implant placement, these modalities have not necessarily translated into improved early reported functional outcomes

Introduction. There is debate regarding whether the use of computer-assisted technology, such as navigation and robotics, has any benefit on clinical or patient reported outcomes following total knee arthroplasty (TKA). This study aims to report on the association between intraoperative use of technology and outcomes in patients who underwent primary TKA. Methods. We retrospectively reviewed 7,096 patients who underwent primary TKA from 2016–2020. Patients were stratified depending on the technology utilized intraoperatively: navigation, robotics, or no technology. Patient demographics, clinical data, Forgotten Joint Score-12 (FJS), and Knee injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR) were collected at various time points up to 1-year follow-up. Demographic differences were assessed with chi-square and ANOVA tests. Clinical data and mean FJS and KOOS, JR scores were compared using univariate ANCOVA, controlling for demographic differences. Results. During the study period, 287 (4%) navigation, 367 (5%) robotics, and 6,442 (91%) manual cases were performed. Surgical time significantly differed between the three groups (113.33 vs. 117.44 vs. 102.11 respectively; p<0.001). Discharge disposition significantly differed between the three groups (p<0.001), with a greater percentage of patients who underwent manual TKA discharged to a skilled nursing facility (12% vs. 8% vs. 15%; p<0.001) than those who had intraoperative technology utilized. FJS scores did not statistically differ at 3-months (p=0.067) and 1-year (p=0.221) postoperatively. There was a significant statistical difference in three-month KOOS, JR scores (59.48 vs. 60.10 vs. 63.64; p=0.001); however, one-year scores did not statistically differ between the three groups (p=0.320). Mean improvement in KOOS, JR scores preoperatively to one-year postoperatively was significantly largest for the navigation group and least for robotics (27.12 vs. 23.78 vs. 25.42; p<0.001). Conclusion. This study demonstrates shorter mean operative time in cases with no utilization of technology and clinically similar patient reported outcome scores associated with TKAs performed between all modalities. While the use of intraoperative technology may aid surgeons, it has not currently translated to better short-term patient outcomes

Introduction. Technology in Orthopaedic surgery has become more widespread in the past 20 years, with emerging evidence of its benefits in arthroplasty. Although patients are aware of benefits of conventional joint replacement, little is known on patients' knowledge of the prevalence, benefits or drawbacks of surgery involving navigation or robotic systems. Materials & Methods. In an outpatient arthroplasty clinic, 100 consecutive patients were approached and given questionnaires to assess their knowledge of Navigation and Robotics in Orthopaedic surgery. Participation in the survey was voluntary. Results. 98 patients volunteered to participate in the survey, mean age 56.2 years (range 19–88; 52 female, 46 male). 40% of patients thought more than 30% of NHS Orthopaedic operations involved navigation or robotics; 80% believed this was the same level or less than the private sector. A third believed most of an operation could be performed independently by a robotic/navigation system. Amongst perceived benefits of navigation/robotic surgery was more accurate surgery(47%), quicker surgery (50%) and making the surgeon's job easier (52%). 69% believed navigation/robotics was more expensive and 20% believed it held no benefit against conventional surgery, with only 9% believing it led to longer surgery. Almost 50% would not mind at least some of their operation being performed with use of robotics/navigation, with a significantly greater proportion of these coming from patients aged under 50 years. Conclusions. Although few patients were familiar with this new technology, there appeared to be a strong consensus it was quicker and more accurate than conventional surgery. Many patients appear to believe navigation and robotics in Orthopaedic surgery is largely the preserve of the private sector. This study demonstrates public knowledge of such new technologies is limited and a need to inform patients of the relative merits and drawbacks of such surgery prior to their more widespread implementation

Introduction. Technology in Orthopaedic surgery has become more widespread in the past 20 years, with emerging evidence of its benefits in arthroplasty. Although patients are aware of benefits of conventional joint replacement, little is known on patients' knowledge of the prevalence, benefits or drawbacks of surgery involving navigation or robotic systems. Materials and methods. In an outpatient arthroplasty clinic, 100 consecutive patients were approached and given questionnaires to assess their knowledge of Navigation and Robotics in Orthopaedic surgery. Participation in the survey was voluntary. Results. 98 patients volunteered to participate in the survey, mean age 56.2 years (range 19–88; 52 female, 46 male). 40% of patients believed more than 30% of NHS Orthopaedic operations involved navigation or robotics; 80% believed this was the same level or less than the private sector. A third believed most of an operation could be performed independently by a robotic/navigation system. Amongst perceived benefits of navigation/robotic surgery was more accurate surgery(47%), quicker surgery (50%) and making the surgeon's job easier (52%). 69% believed navigation/robotics was more expensive and 20% believed it held no benefit against conventional surgery, with only 9% believing it led to longer surgery. Almost 50% would not mind at least some of their operation being performed with use of robotics/navigation, with a significantly greater proportion of these coming from patients aged under 50 years. Conclusions. Although few patients were familiar with this new technology, there appeared to be a strong consensus it was quicker and more accurate than conventional surgery. Many patients appear to believe navigation and robotics in Orthopaedic surgery is largely the preserve of the private sector. This study demonstrates public knowledge of such new technologies is limited and a need to inform patients of the relative merits and drawbacks of such surgery prior to their more widespread implementation

Recently, axial radiography has received attention for the assessment of distal femur rotational alignment, and satisfactory results have been as compared with the CT method. The purpose of this study was to assess rotational alignment of the femoral component in knee flexion by axial radiography and to compare flexion stabilities achieved by navigational and robotic total knee arthroplasty (TKA). In addition, the authors also evaluated the effects of flexion stability on functional outcomes in these two groups. Sixty-four patients that underwent TKA for knee osteoarthritis with a minimum of follow-up of 1 year constituted the study cohort. Patients in the navigational group (N = 32) underwent TKA using the gap balancing technique and patients in the robotic group (N = 32) underwent TKA using the measured resection technique. To assess flexion stability using axial radiography a novel technique designed by the authors was used. Rotations of femoral components and mediolateral gaps in the neutral position on flexion radiographs was measured and compared. Valgus and varus stabilities under valgus-varus stress loading, and total flexion stabilities (defined as the sum of valgus and varus stability) were also compared, as were clinical outcomes at final follow up visits. A significant difference was found between the navigation and robotic groups for mean external rotation of the femoral component (2.1° and 0.4°, respectively; p = 0.003). Mean mediolateral gap in neutral at 90° flexion position was 0.17° in the navigation group and 0.07° in the robotic group (p = 0.126), and mean total stability was 7.82° in the robotic group and 8.10° in the navigation group (p = 0.35). Clinically, no significant intergroup difference was found in terms of ranges of motion, HSS scores, KS scores, or WOMAC scores. Both navigational and robotic techniques provide excellent clinical and flexion stability results. Furthermore, axial radiography was found to provide a useful, straightforward means of detecting rotational alignment, flexion gaps, and flexion stability

Restoring native hip biomechanics is crucial to the success of THA. This is reflected both in terms of complications after surgery such as instability, leg length inequality, pain and limp; and in terms of patient satisfaction. The challenge that remains is that of achieving optimal implant sizing and positioning so as to restore, as closely as possible, the native hip biomechanics specific to the hip joint being replaced. This would optimise function and reduce complications, particularly, instability. (Mirza et al., 2010). Ideally, this skill should also be reproducible irrespective of the surgeon's experience, volume of surgery and learning curve. The general consensus is that the most substantial limiting factor in a THA is the surgeon's performance and as a result, human errors and unintended complications are not completely avoidable (Tarwala and Dorr, 2011). The more challenging aspects include acetabular component version, sizing and femoral component sizing, offset and position in the femoral canal. This variability has led to interest in technologies for planning THA, and technologies that help in the execution of the procedure. Advances in surgical technology have led to the development of computer navigation and robotic systems, which assist in pre-operative planning and optimise intra-operative implant positioning. The evolution of surgical technology in lower limb arthroplasty has led to the development of computer navigation and robotics, which are designed to minimise human error and improve implant positioning compared to pre-operative templating using plain radiographs. It is now possible to use pre-operative computerised tomography (image-based navigation) and/or anatomical landmarks (non-imaged-based navigation) to create three-dimensional images of each patient's unique anatomy. These reconstructions are then used to guide bone resection, implant positioning and lower limb alignment. The second-generation RIO Robotic Arm Interactive Orthopaedic system (MAKO Surgical) uses pre-operative computerised tomography to build a computer-aided design (CAD) model of the patient's hip. The surgeon can then plan and execute optimal sizing and positioning of the prostheses to achieve the required bone coverage, minimise bone resection, restore joint anatomy and restore lower limb biomechanics. The MAKO robotic software processes this information to calculate the volume of bone requiring resection and creates a three-dimensional haptic window for the RIO-robotic arm to resect. The RIO-robotic arm has tactile and audio feedback to resect bone to a high degree of accuracy and preserve as much bone stock as possible. We have used this technology in the hip to accurately reproduce the anteversion, closure and center of rotation that was planned for each hip. Whilst the precise safe target varies from patient to patient, the ability to reproduce native biomechanics, to gain fixation as planned and to get almost perfect length and offset are a great advantage. Complications such as instability and leg length inequality are thus dramatically reduced

This technique is a novel superior based muscle sparing approach. Acetabular reaming in all hip approaches requires femoral retraction. This technique is performed through a hole in the lateral femoral cortex without the need to retract the femur. A 5 mm hole is drilled in the lateral femur using a jig attached to the broach handle, similar to a femoral nail. Specialised instruments have been developed, including a broach with a hole going through it at the angle of the neck of the prosthesis, to allow the rotation of the reaming rod whilst protecting the femur. A special C-arm is used to push on the reaming basket. The angle of the acetabulum is directly related to the position of the broach inside the femoral canal and the position of the leg. A specialised instrument allows changing of offset and length without dislocating the hip during trialling. Some instrumentation has been used in surgery but ongoing cadaver work is being performed for proof of concept. The ability to ream through the femur has been proven during surgery. The potential risk to the bone has been assessed using finite analysis as minimal. The stress levels for any diameter maintained within a safety factor >4 compared to the ultimate tensile strength of cortical bone. The described technique allows for transfemoral acetabular reaming without retraction of the femur. It is minimally invasive and simple, requiring minimal assistance. We are incorporating use with a universal robot system as well as developing an electromagnetic navigation system. Assessment of the accuracy of these significantly cheaper systems is ongoing but promising. This approach is as minimally invasive as is possible, safe, requires minimal assistance and has a number of other potential advantages with addition of other new navigation and simple robotic attachments

Precision planning with correct sizing and placement of components is critical to proper execution of total hip arthroplasty. While the desire to achieve excellent outcomes has always been a surgeon's goal, value-based care programs such as the Comprehensive Joint Replacement (CJR) program apportion real expenditures for the cost of treating complications such as fracture or dislocation to the participants. Such accountability accentuates the importance of optimizing the planning and execution of joint replacement surgery. Acetabular component sizing and placement in particular remains the single greatest challenge to surgeons. This is simply due to the fact that the requisite spatial information is not available to the surgeon during conventional surgery. Basing component placement on local anatomical landmarks without knowing the patient-specific nature of those landmarks ensures poor component placement in many cases. As a result, studies demonstrate that at least ½ of all acetabular components placed using conventional methods are malpositioned. Potential solutions include the using of intra-operative radiographic analysis, traditional navigation and robotics. Unfortunately, measurements of plain radiographs have repeatedly been shown to be inaccurate due to lack of knowledge of and correction for beam center location, magnification, beam divergence, and position of the pelvis itself on the image. As a result, such quantification of unquantifiable images can systematically lead to poor decisions. Intra-operative radiograph measurement methods have been shown to lead to anteversion measurement errors as high as 27 degrees. Similarly, there is a perception that performing total hip arthroplasty through the anterior exposure can result in reliable cup positioning when fluoroscopy is used, but such procedures have also been shown to have a high incidence of cup malposition. Image-free navigation, image-based navigation, and image-based robotics can potentially lead to accurate component placement. Adoption of these technologies, however, has been limited, possibly due to the increase in time of use, complexity, and cost of these systems. Robotic systems have also proven to be potentially hazardous and inaccurate in routine clinical use. A cloud-based, patient-specific hip surgery planning and smart-tool cup navigation system was developed to address the most common technical problems affecting hip arthroplasty (HipXpert System, Surgical Planning Associates, Boston, MA). The methodology provides the surgeon with a full 3D plan of the surgery including cup size, cup orientation, stem size, head length, femoral anteversion, and planned change in leg length and offset. The application controlling the plan allows the surgeon to instantly change the plan and shows the implants in both 3D and on multiplanar cross-sectional views. The associated smart tool is adjusted specifically for that patient and when docked, provides orientation information to the surgeon. The system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases including by an independent study. This compares to a recent study of robotic methods that measured 88% for inclination and 84% for anteversion. Cloud-based 3D planning combined with smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problems of acetabular component malorientation and provides critical pre-operative information including acetabular and femoral component sizes, planned femoral anteversion, and planned changes in leg length and offset of the surgery

To introduce a new robot-assisted surgical system for spinal posterior fixation which called TiRobot, based on intraoperative three-dimensional images. TiRobot has three components: the planning and navigation system, optical tracking system and robotic arm system. By combining navigation and robot techniques, TiRobot can guide the screw trajectories for orthopedic surgeries. In this randomised controlled study approved by the Ethics Committee, 40 patients were involved and all has been fully informed and sign the informed consent. 17 patients were treated by free-hand fluoroscopy-guided surgery, and 23 patients were treated by robot-assisted spinal surgery. A total of 190 pedicle screws were implanted. The overall operation times were not different for both groups. None of the screws necessitated re-surgery for revised placement. In the robot-assisted group, assessment of pedicle screw accuracy showed that 102 of 102 screws (100%) were safely placed (<2 mm, category A+B). And mean deviation in entry point was 1.70 +/− 0.83mm, mean deviation in end point was 1.84 +/− 1.04mm. In the conventional freehand group, assessment of pedicle screw accuracy showed that 87 of 88 (98.9%) were safely placed (<2 mm, category A+B), 1 screw fall in category C, mean deviation in entry point was 3.73 +/− 2.28mm, mean deviation in end point was 4.11 +/− 2.31mm. This randomised controlled study verified that robot-assisted pedicle screw placement with real-time navigation is a more accuracy and safer method, and also revealed great clinical potential of robot-assisted surgery in the future

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

Acetabular component malalignment remains the single greatest root cause for revision THA with malposition of at least half of all acetabular components placed using conventional methods. These studies repeatedly document that the concept of using local anatomical landmarks has no scientific basis over a breadth of presenting pathology. Traditional navigation and robotics can potentially lead to improved component placement but these technologies have not gained widespread use due to the increase in time of use, complexity, and cost of these systems. Robotic systems have also proven to be potentially hazardous and inaccurate in routine clinical use. The alternative of placing the cup in the supine position, even with the use of arthroscopy, has been proven to have an incidence of inaccuracy equal or greater than that in the lateral position. A smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment (HipXpert System, Surgical Planning Associates, Boston, MA). The system is based on a low dose, low cost CT study and a customised patient-specific surgery plan. The laterally-based system docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. The anteriorly-based system also docks on a patient-specific basis with one leg on the anterior ischium and one leg on each ASIS, either to skin or to bone. The lateral system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases and an independent study showing accurate cup placement in 98% of cases for both anteversion and inclination. This compares to a recent study of robotic methods that 88% of inclination and 84% for anteversion. Smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problem of acetabular component malorientation

We live in an era where younger, fitter, more active patients are presenting with the symptoms and signs of degenerative joint disease and require total knee and total hip arthroplasty at a young age. At the same time, this population of patients is living longer and longer and is likely to create new and more complex failure modes for their implants. The ideal solution is a biological one, whereby we can either prevent joint degradation or catch it in its early stages and avoid further deterioration. There may also be advances along the way in terms of partial arthroplasty and focal resurfacing that will help us prevent the need for total joint arthroplasty. There are several tensions that need to be considered. Should we resurface / replace early, particularly now that we have access to navigation and robotics and can effectively customise the implants to the patient's anatomy and their gait pattern? This would allow good function at a young age. Or should we wait as long as possible and risk losing some function for the sake of preserving the first arthroplasty for the lifetime of the patient?. There are some key issues that we still do not fully understand. The lack of true follow-up data beyond 20 or 30 years is worrying. The data available tends to be from expert centers, and always has a dramatic loss to follow-up rate. We worry about bearing surfaces and how those materials will behave over time but we really do not know the effect of chronic metal exposure over several decades, nor do we really understand what happens to bone as it becomes more and more osteopenic and fragile around implants. We have largely recorded but ignored stress shielding, whereas this may become a very significant issue as our patients get older, more fragile, more sarcopaenic and more neurologically challenged. All the fixation debates that we have grappled with, may yet come back to the fore. Can ingrowth lead to failure problems later on? Will more flexible surfaces and materials be required to fit in with the elasticity of bone?. We have failed dramatically at translating the in vitro to the in vivo model. It seems that the in vitro model tells us when failure is going to occur but success in vitro does not predict success in vivo. We, therefore, cannot assume that long-term wear data from simulators will necessarily translate to the extreme situations in vivo where the loading is not always idealised, and can create adverse conditions. We must, therefore, consider further how to improve and enhance our interventions. There is no doubt that the avoidance of arthroplasty needs to be at the heart of our thinking but, ultimately, if arthroplasty is to be performed, it needs to be performed expertly and in such a way as to minimise later failure. It also, clearly, needs to be cost-effective. The next stage will no doubt involve close cooperation between surgeons, engineers and industry partners to identify individualised surgical targets, select an appropriate prosthesis to minimise soft-tissue strain and develop a reproducible method of achieving accurate implantation. An ideal outcome can only be achieved by an appropriately trained surgeon selecting the optimal prosthesis to implant in the correct position in the well-selected patient. In the longer term, our choice of implants and the way that they are inserted and fixed must take into account the evolving physiology of our patients, the nature of our devices and how to limit harm from them, and the long-term impact of the materials used which we sometimes still do not understand

Acetabular component malalignment remains the single greatest root cause for revision THA with malposition of at least ½ of all acetabular components placed using conventional methods. The use of local anatomical landmarks has repeatedly proven to be unreliable due to individual variation of these structures. As a result, the use of such landmarks without knowledge of their three-dimensional orientation may actually be a major cause of component malpositioning. Traditional navigation and robotics can potentially lead to improved component placement but these technologies have not gained widespread use due to the increase in time of use, complexity, and cost of these systems. The alternative of placing the cup in the supine position, even with the use of arthroscopy, has been proven to have an incidence of inaccuracy equal or greater than that in the lateral position. A smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment (HipXpert System, Surgical Planning Associates, Boston, MA). The system is based on a low dose, low cost CT study and a customised patient-specific surgery plan. The laterally-based system docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. The anteriorly-based system also docks on a patient-specific basis with one leg on the anterior ischium and one leg on each ASIS, either to skin or to bone. The lateral system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases and an independent study showing accurate cup placement in 98% of cases for both anteversion and inclination. This compares to a recent study of robotic methods with 88% for inclination and 84% for anteversion. Smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problem of acetabular component malorientation

Introduction. Navigation of acetabular component orientation is still not commonly performed despite repeated studies that show that more than ½ of acetabular components placed during hip arthroplasty are significantly malpositioned1. The current study uses postoperative CT to assess the accuracy of a smart mechanical navigation instrument system for cup alignment. Patients and Methods. Twenty nine hip replacements performed using the HipXpert Navigation System had post-operative CT studies available for analysis. These post-operative CT studies were performed for pre-operative planning of the contralateral side, one to three years following the prior surgery. The patients included 17 men and 11 women. An application specific software module was developed to measure cup orientation using CT (HXR Application 1.3 Surgical Planning Associates Inc., Boston, Massachusetts). The method involves creation of a 3D surface model from the CT data and then determination of an Anterior Pelvic Plane coordinate system. A multiplaner image viewer module is then used to create an image through the CT dataset that is coincident with the opening plane of the acetabular component. Points on this plane are input and then the orientation of the cup is calculated relative to the AP Plane coordinate space according to Murray's definitions of operative anteversion and operative inclination. The actual cup orientation was then compared to the goal of cup orientation recorded when the surgery was performed using the HipXpert navigation system for acetabular component alignment. Results. Mean operative anteversion error was 1.7 degrees (SD 3.4, range −6.5 to 8.5). Mean operative inclination error was −2.3 degrees (SD 3.1, range −8.9 to 3.9). There were no outliers in either anteversion or inclination. Conclusion. The current study demonstrates that the mechanical navigation system produces accurate cup alignment results as measured by post-operative CT and confirms the prior accuracy study performed using 2D/3D matching. This accuracy, compared to traditional navigation and robotic systems, may be due to the wide-based nature of the docking mechanism and the elimination of the cumulative errors of registration and tracking inherent to more complex systems

Acetabular component malalignment remains the single greatest root cause for revision THA with malposition of at least ½ of all acetabular components placed using conventional methods. The use of local anatomical landmarks has repeatedly proven to be unreliable due to individual variation of these structures. As a result, the use of such landmarks without knowledge of their three-dimensional orientation may actually be a major cause of component malpositioning. Traditional navigation and robotics can potentially lead to improved component placement but these technologies have not gained widespread use due to the increase in time of use, complexity, and cost of these systems. The alternative of placing the cup in the supine position, even with the use of arthroscopy, has been proven to have an incidence of inaccuracy equal or greater than that in the lateral position. A smart mechanical instrument system was developed to quickly and easily achieve accurate cup alignment (HipXpert System, Surgical Planning Associates, Boston, MA). The system is based on a low dose, low cost CT study and a customised patient-specific surgery plan. The laterally-based system docks on a patient-specific basis with 3 legs: one through the incision behind the posterior rim, one percutaneously on the lateral side of the ASIS, and a third percutaneously on the surface of the ilium. A direction indicator on the top of the instrument points in the desired cup orientation. The anteriorly-based system also docks on a patient-specific basis with one leg on the anterior ischium and one leg on each ASIS, either to skin or to bone. The lateral system has been proven to be robust, with repeated studies showing accurate cup placement in 100% of cases and an independent study showing accurate cup placement in 98% of cases. The newer anterior system has the potential for even greater accuracy. Smart mechanical navigation of cup placement offers the optimum combination of accuracy, speed, and simplicity for solving the ubiquitous problem of acetabular component malorientation

Since its inception, knee arthroplasty has struggled to balance the requirements of relieving pain and restoring function in a durable way. Although highly successful in improving symptoms as measured by traditional outcome measures and achieving longevity, numerous studies have shown the problems that exist, even with well-implanted components of modern design. Some patients complain of ongoing functional limitation, discomfort, and pain. There are still many challenges in knee arthroplasty. We have a young population that is increasingly active that requires these procedures and yet they are living to a ripe old age and remaining ambulant into their 80s and 90s. We have focussed for the last decade on improving function and satisfaction in knee arthroplasty but we should not forget the fact that the highest failure rate is seen in our young patients and that we really do need a durable solution that will last several decades. There are several tensions that need to be considered. Should we resurface the knee early, particularly now that we have access to navigation and robotics and can effectively customise the implants to the patient's anatomy and their gait pattern? This would allow good function at a young age. Or should we wait as long as possible and risk losing some function for the sake of preserving the first arthroplasty for the lifetime of the patient?. Should we for example accept alignment paradigms that we know give us longevity or should we go with alternative kinematic or anatomical alignment techniques that may well give us better function but could compromise long-term fixation? Both registries and the long-term studies available suggest that we can expect good survivorship into the second decade for older patients and for some into the third decade, but data beyond that is sparse and is not available with contemporaneous implants. Changing the polyethylene in the knee may prove to be successful but may yet be nowhere near as beneficial as it has been in the hip. There has also been all too little work to consider the changing physiology of the bone. Will the increasing trend for cementless implants lead to longer lasting osseointegration or will it lead to periprosthetic fractures through areas of stress shielding? We have been spared somewhat thus far in the knee the issue of local metal ion effects and systemic issues that we have seen in the hip. If our implants last longer and are treated more brutally by an active patient population, we may yet see more problems. At the same time, we have to continue evolving our technologies and yet be cost effective and affordable. Our focus on operative efficiency, early discharge, rapid recovery and a return to full function must not compromise our goals and plans for implant longevity. The next stage will no doubt involve close co-operation between surgeons, engineers and industry partners to identify individual surgical targets, select an appropriate prosthesis to minimise soft-tissue strain and develop a reproducible method of achieving accurate implantation. However, in seeking to solve the problems seen in a proportion of arthroplasty patients, the achievements of ‘traditional’ total knee arthroplasty should not be overlooked. The results achieved by such methods in all three domains: pain relief, functional restoration and longevity, should act as baseline measures for newer techniques and designs. Improvements in any one domain should not be at the expense of another. An ideal outcome can only be achieved by an appropriately trained surgeon selecting the optimal prosthesis to implant in the correct position in the well-selected patient

INTRODUCTION. Acetabular cup malpositioning has been implicated in instability and wear-related complications after total hip arthroplasty. Although computer navigation and robotic assistance have been shown to improve the precision of implant placement, most surgeons use mechanical and visual guides to place acetabular components. Authors have shown that, when using a bean bag positioner, mechanical guides are misleading as they are unable to account for the variability in pelvic orientation during positioning and surgery. However, more rigid patient positioning devices may allow for more accurate free hand cup placement. To our knowledge, no study has assessed the ability of rigid devices to afford surgeons with ideal pelvic positioning throughout surgery. The purpose of this study is to utilize robotic-arm assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. METHODS. 100 hips (94 patients) prospectively underwent total hip Makoplasty in the lateral decubitus position from the posterior approach; 77 stabilized by universal lateral positioner, and 23 by peg board. After dislocation but prior to reaming, one fellowship trained arthroplasty surgeon manually placed the robotic arm parallel to both the longitudinal axis of the patient and the horizontal surface of the operating table, which, if the pelvis were oriented perfectly, would represent 0 degrees of anteversion and 0 degrees of inclination. The CT-templated computer software then generated true values of this perceived zero degrees of anteversion and inclination based on the position of the robot arm registered to a preoperative pelvic CT. Therefore, variations in pelvic positioning are represented by these robotic navigation generated values. To assure the accuracy of robotic measurements, cup anteversion and inclination at times of impaction were recorded and compared to those calculated via the trigonometric ellipse method of Lewinnek on standardized 3 months postoperative X-rays. RESULTS. Mean alteration in anteversion and inclination values were 1.7 degrees (absolute value 5.3 degrees, range −20 – 20 degrees) and 1.6 degrees (absolute value 2.6 degrees, range −8 – 10 degrees) respectively. 22% of anteversion values were altered by >10 degrees; 41% by > 5 degrees. There was no difference between positioners (p=0.36) and regression analysis revealed that anteversion differences were correlated with BMI (p=0.02). Robotic navigation acetabular cup anteversion (mean 21.8 degrees) was not different from postoperative X-ray anteversion (mean 21.9 degrees)(p=0.50), nor was robotic navigation acetabular cup inclination (mean 40.6 degrees) different from postoperative X-ray inclination (mean 40.5 degrees)(p=0.34). DISCUSSION AND CONCLUSION. Rigid pelvic positioning devices present 5 to 20 degrees of variability in acetabular cup orientation, particularly with regards to anteversion. Compounding this with 20 degree safe zones and prior author demonstrations that human error is prone to 10 degrees of anteversion inaccuracy in a fixed pelvis model, there is a clear need to pay particular attention to anatomic landmarks or computer assisted techniques to assure accurate acetabular cup positioning. Patient positioning by itself should not be trusted

Introduction. Knee osteoarthritis is a leading cause of disability around the world. Traditionally, total knee arthroplasty (TKA) is the gold standard treatment; however, unicompartmental knee arthroplasty (UKA) has emerged as a less-invasive alternative to TKA. Patients with UKAs participate earlier with physical therapy (PT), have decreased complications, and faster discharges (1, 2). As UKA has evolved, so has computer navigation and robotic technology. The Robotic Assisted UKA combines the less invasive approach of the UKA with accurate and reproducible alignment offered by a robotic interface (3)(Figure1). A key part of a patient's satisfaction is perioperative pain control. Femoral nerve blocks (FNB) are commonly performed to provide analgesia, though they cause quadriceps weakness which limits PT (4). An alternative is the adductor canal block (ACB) which provides analgesia while limiting quadriceps weakness (4). The adductor canal is an aponeurotic structure in the middle third of the thigh containing the femoral artery and vein, and several nerves innervating the knee joint including the saphenous nerve, nerve to the vastus medialis, medial femoral cutaneous nerve, posterior branch and occasionally the anterior branch of the obturator nerve (5). In a multi-modal approach with Orthopedic Surgery, Regional Anesthesia, and PT departments, an early goal directed plan of care was developed to study ACB in UKA with a focus on analgesia effectiveness and PT compliance rates. Methods. Following IRB approval, we performed a case series including 29 patients who received a single shot ACB. Primary outcomes were distance walked with PT on postoperative day (POD) 0 and 1 and discharge day. Our secondary outcomes included Visual Analog Scale (VAS) scores in the post-anesthesia care unit (PACU), 8 and 24 hours postoperatively and oral morphine equivalents required for breakthrough pain. Results. All patients received PT prior to discharge. With respect to distance walked, the median distance on POD 0 was 26 feet (IQR 9–66), and on POD 1 was 128 feet (IQR of 80–200), and the median day of discharge was POD 1 (IQR 0–2). In this study, the patients’ median age was 64 (IQR 59–69) and the median BMI was 31 kg/m2 (IQR 22–41). The median VAS score in the PACU was 1 (IQR 0–7). The VAS scores for 8 and 24 hours were 5 (IQR 2–7) and 5 (IQR 2.7–7). Median oral morphine equivalents required for breakthrough pain were 99.5 mg (IQR 67.5–150.5 mg) (Figure 3). Conclusion. This case series supports that a single shot ACB facilitates early PT and hospital discharge in patients post UKA

Introduction. Recent advances in 3D printing enable the use of custom patient-specific instruments to place drill guides and cutting slots for knee replacement surgery. However, such techniques limit the ability to intra-operatively adjust an implant plan based on soft-tissue tension and/or joint pathology observed in the operating room, e.g. cruciate ligament integrity. It is hypothesized that given the opportunity, a skilled surgeon will make intra-operative adjustments based on intra-operative information not captured by the hard tissue anatomy reconstructed from a pre-operative CT scan or standing x-ray. For example, tibiofemoral implant gaps measured intra-operatively are an indication of soft-tissue tension in the patient's knee, and may influence a surgeon to adjust implant position, orientation or size. This study investigates the frequency and magnitude of intra-operative adjustments from a single orthopedic surgeon during 38 unicondylar knee arthroplasty (UKA) cases. Methods. For each patient, a pre-operative plan was created based on the bony anatomy reconstructed from the pre-operative CT. This plan is analogous to a plan created with patient-specific cutting blocks or customized implants. With robotic technology that utilizes pre-operative imaging, intra-operative navigation and robotic execution, this “anatomic” plan can be fine-tuned and adjusted based on the soft tissue envelop measured intra-operatively. The relative positions of the femur and the tibia are measured intra-operatively under a valgus load (for medial UKA, varus load for lateral UKA) for each patient from extension to deep knee flexion and used to compute the predicted space between the implants (gaps) throughout flexion. The planned position, orientation and size of the components can then be adjusted to achieve an optimal dynamic ligament balance prior to any bony cuts. This is the plan that is then executed under robotic guidance. Intra-operative adjustments are defined as any size, position or orientation changes occurring intra-operatively to the pre-operative anatomic plan. Results. The surgeon adjusted the pre-operative implant plan in 86.8% of cases, leading to combined RMS changes of 2.0 mm and 2.1 degrees to the femoral implant, and 0.9 mm and 1.4 degrees to the tibial implant. The RMS femoral implant translations and rotations were 1.0, 1.5, 0.9 mm and 1.0, 1.0, 1.7 degrees in the medial, anterior, and superior directions, respectively. The RMS tibial implant translations and rotations were 0.2, 0.4, 0.8 mm and 1.3, 0.4, 0.6 degrees in the medial, anterior, and superior directions, respectively. Implant sizes were adjusted in 36.8% of cases, with all changes occuring to the femoral implant, and 13 out of those 14 cases showing a reduction in the femoral implant size. Conclusions. These data support the hypothesis that surgical planning of UKA components based on accurate 3D dimensional reconstructions of anatomy alone is not adequate to create optimal implant gap spacing throughout flexion. Measurement and knowledge of the patient's soft tissue envelope allows for signficiant changes to the implant plan prior to any bony cuts

Introduction. Interactions between hip, pelvis and spine, as abnormal spinopelvic movements, have been associated with inferior outcomes following total hip arthroplasty (THA). Changes in pelvis position lead to a mutual change in functional cup orientation, with both pelvic tilt and rotation having a significant effect on version. Hip osteoarthritis (OA) patients have shown reduced hip kinematics which may place increased demands on the pelvis and the spine. Sagittal and coronal planes assessments are commonly done as these can be adequately studied with anteroposterior and lateral radiographs. However, abnormal pelvis rotation is likely to compromise the outcome as they have a detrimental effect on cup orientation and increased impingement risk. This study aims to determine the association between dynamic motion and radiographic sagittal assessments; and examine the association between axial and sagittal spinal and pelvic kinematics between hip OA patients and healthy controls (CTRL). Methods. This is a prospective study, IRB approved. Twenty hip OA pre-THA patients (11F/9M, 67±9 years) and six CTRL (3F/3M, 46±18 years) underwent lateral spinopelvic radiographs in standing and seated bend-and-reach (SBR) positions. Pelvic tilt (PT), pelvic-femoral-angle (PFA) and lumbar lordosis (LL) angles were measured in both positions and the differences (Δ) between standing and SBR were calculated. Dynamic SBR and seated maximal-trunk-rotation (STR) were recorded in the biomechanics laboratory using a 10-infrared camera and processed on a motion capture system (Vicon, UK). Direct kinematics extracted maximal pelvic tilt (PT. max. ), hip flexion (HF. max. ) and (mid-thoracic to lumbar) spinal flexion (SF. max. ). The SBR pelvic movement contribution (ΔPT. rel. ) was calculated as ΔPT/(ΔPT+ΔPFA)∗100 for the radiographic analysis and as PT. max. /(PT. max. +HF. max. ) for the motion analyses. Axial and sagittal, pelvic and spinal range of motion (ROM) were calculated for STR and SBR, respectively. Spearman's rank-order determined correlations between the spinopelvic radiographs and sagittal kinematics, and the sagittal/axial kinematics. Mann-Whitney U-tests compared measures between groups. Results. Radiograph readings correlated with sagittal kinematics during SBR for ΔPT and PT. max. (ρ=0.64, p<0.001), ΔPFA and HF. max. (ρ=0.44, p<0.0002), and ΔLL and SF. max. (ρ=0.34, p=0.002). Relative pelvic movements (ΔPT. rel. ) were not different between radiographic (11%±21) and biomechanical (15%±29) readings (p=0.9). Sagittal SRB spinal flexion correlated with the axial STR rotation (ρ=0.43, p<0.0001). Although not seen in CTRL, sagittal SRB pelvic flexion strongly correlated with STR pelvic rotation in OA patients (ρ=0.40, p=0.002). All spinopelvic parameters were different between the patients with OA and CTRL. CTRLs exhibited significantly greater mobility and less variability in all 3 segments (spine, pelvis, hip) and both planes (axial and sagittal) (Table 1). Conclusion. Correlation between sagittal kinematics and radiographical measurements during SBR validates the spinopelvic mobility assessments in the biomechanics laboratory. Axial kinematics of both pelvis and spine correlated significantly in OA patients, suggesting that patients with abnormal sagittal mobility are likely to also exhibit abnormal axial mobility, which can further potentiate any at-risk kinematics. Significantly lower OA ROM must be investigated post-THA. Pre-THA variability of both sagittal and axial movements indicates that both planes must be considered ahead of surgical planning with navigation and/or robotics. For any figures or tables, please contact the authors directly