There is conflicting evidence about whether avoiding medullary canal reaming of the femur during total knee arthroplasty (TKA) reduces blood loss. This study aimed to test the hypothesis that total blood loss would decrease in TKA without medullary canal reaming.

This propensity score-matched cohort study included 349 patients, of whom 220 underwent TKA using a femoral intramedullary rod, and 129 underwent TKA using a computer-assisted system without a femoral intramedullary alignment system. For the proximal tibia resection, an intramedullary alignment system was not used in any of the patients. These patients were matched using a one-to-one propensity score method. The primary outcome was perioperative blood loss, calculated from patient blood volume and the difference in hemoglobin levels from preoperative to postoperative measurements.

Compared with 118 propensity score-matched patients undergoing TKA with medullary canal reaming of the femur, perioperative blood loss at 1, 3, and 7 days postoperatively was not significantly different in the 118 matched patients undergoing TKA without medullary canal reaming. In addition, no significant differences were observed in the requirement for allogeneic transfusion or the occurrence of deep venous thrombosis.

Postoperative blood loss did not differ between patients who underwent TKA with femoral intramedullary reaming and those without. This study supports the notion that surgeons can use familiar surgical techniques, including conventional intramedullary rods, without the need for specialized instrument, even for patients at high risk of allogeneic transfusion.

Smartphones contain powerful and enabling technology components that can be re-applied toward procedural tasks commonly used in everyday clinical image-guided therapies and minimally invasive procedures that use three-dimensional information and feedback during procedures. Smartphone applications are a relatively young field of research that have potential in interventional radiology (IR) toward improvement of accuracy and standardization for needle-based procedures like biopsy and ablation. This review explores the adaptation of smartphones' built-in sensors for virtual and augmented reality uses in IR. The ergonomic advantages and translational hurdles and limitations are reviewed, outlining the potential future developmental pathway of smartphones in IR.

The purpose of this study was to examine the comparative precision of the augmented reality (AR)-assisted navigation system and the accelerometer-based navigation system in total knee arthroplasty (TKA).

We performed noninferiority analysis in a retrospective cohort. The coronal alignment of femoral prosthesis was compared between 109 TKAs performed using the AR-assisted navigation system and 118 TKAs performed using the accelerometer-based navigation system. All femoral prostheses were planned to be positioned perpendicular to the mechanical axis of the femur. The primary outcome was the success rate of coronal alignment of the femoral prosthesis defined as alignment error relative to neutral alignment <3°. We calculated the noninferiority margin as 7%-points using the 95%-95 % method and also confirmed the validity of the noninferiority margin using the fixed margin method. Noninferiority would be shown if the lower boundary of the 95 % confidence interval (CI) for the between-group difference in percentage of the success rate was not less than 0.93 (i.e., 1.00 - 0.07).

Treatment success was achieved in 104 of 109 patients (95.4 %) in the AR-assisted navigation group and 110 of 118 (93.2 %) in the accelerometer-based navigation group. The risk ratio of success between the AR-assisted navigation group versus accelerometer-based navigation group was 1.02 (95 % CI, 0.96 to 1.09): the CIs did not include the noninferiority margin of 0.93.

The AR-assisted navigation system was noninferior to the accelerometer-based navigation system in terms of coronal alignment of the femoral prosthesis in TKA.

This study was performed to investigate the relationship between the amount of femorotibial alignment correction and the amount of improvement of hindfoot alignment in total knee arthroplasty (TKA).

A total of 159 knees undergoing TKA in 120 patients were assessed preoperatively and at 2 weeks, 1 month, 3 months and 6 months postoperatively. Standing hindfoot alignment was evaluated using the leg-heel angle (LHA). The amount of change in hindfoot alignment was compared between patients with severe varus knee (Group 1) and those with moderate varus, neutral or valgus knee (Group 2).

The mean values of pre- and postoperative hip-knee-ankle (HKA) angle were -14 ± 4° and -1 ± 3° in Group 1 and -7 ± 5° and -1 ± 3° in Group 2, respectively. The differences between pre- and postoperative LHA were significantly larger in Group 1 than in Group 2 at 2 weeks, 1 month and 3 months postoperatively (p = 0.006, 0.001 and 0.03, respectively). At 6 months postoperatively, no differences were observed between the two groups (p = 0.31).

The amount of change in hindfoot alignment was larger in Group 1 than in Group 2 at 2 weeks, 1 month and 3 months after TKA, but there was no significant difference between the two groups at 6 months after TKA.

Prognostic Level II.

Total knee arthroplasty (TKA) is a commonly performed procedure that has traditionally utilized reproducible steps using a set of mechanical instruments. The number of TKAs performed using robotic assistance is increasing, and augmented reality (AR) navigation systems are being developed. Hierarchical task analysis (HTA) aims to describe the steps of a specific task in detail to reduce errors and ensure reproducibility. The objective of this study was to develop and validate HTAs for conventional, robotic-assisted, and AR-navigated TKA.

The development of HTAs for conventional TKA involved an iterative review process that incorporated the input of 4 experienced arthroplasty surgeons. The HTAs were then adapted for robotic-assisted and AR-navigated TKA by incorporating specific steps associated with the use of these systems. The accuracy and completeness of the HTAs were validated by observing 10 conventional and 10 robotic-assisted TKA procedures.

HTAs for conventional, robotic-assisted, and AR-navigated TKA were developed and validated. The resulting HTAs provide a comprehensive and standardized plan for each procedure and can aid in the identification of potential areas of inefficiency and risk. Robotic-assisted and AR-navigated approaches require additional steps, and there are an increased number of instances where complications may occur.

The HTAs developed in this study can provide valuable insights into the potential pitfalls of robotic-assisted and AR-navigated TKA procedures. As AR-navigation systems are developed, they should be optimized by critical analysis using the developed HTAs to ensure maximum efficiency, reliability, accessibility, reduction of human error, and costs.

 Augmented reality (AR) and virtual reality (VR)-termed mixed reality-have shown promise in the care of operative patients. Currently, AR and VR have well-known applications for craniofacial surgery, specifically in preoperative planning. However, the application of AR/VR technology to other reconstructive challenges has not been widely adopted. Thus, the purpose of this investigation is to outline the current applications of AR and VR in the operative setting.

 The literature pertaining to the use of AR/VR technology in the operative setting was examined. Emphasis was placed on the use of mixed reality technology in surgical subspecialities, including plastic surgery, oral and maxillofacial surgery, colorectal surgery, neurosurgery, otolaryngology, neurosurgery, and orthopaedic surgery.

 Presently, mixed reality is widely used in the care of patients requiring complex reconstruction of the craniomaxillofacial skeleton for pre- and intraoperative planning. For upper extremity amputees, there is evidence that VR may be efficacious in the treatment of phantom limb pain. Furthermore, VR has untapped potential as a cost-effective tool for microsurgical education and for training residents on techniques in surgical and nonsurgical aesthetic treatment. There is utility for mixed reality in breast reconstruction for preoperative planning, mapping perforators, and decreasing operative time. VR has well- documented applications in the planning of deep inferior epigastric perforator flaps by creating three-dimensional immersive simulations based on a patient's preoperative computed tomography angiogram.

 The benefits of AR and VR are numerous for both patients and surgeons. VR has been shown to increase surgical precision and decrease operative time. Furthermore, it is effective for patient-specific rehearsal which uses the patient's exact anatomical data to rehearse the procedure before performing it on the actual patient. Taken together, AR/VR technology can improve patient outcomes, decrease operative times, and lower the burden of care on both patients and health care institutions.

Total knee arthroplasty (TKA) is a gold standard surgical procedure to improve pain and restore function in patients affected by moderate-to-severe severe gonarthrosis refractory to conservative treatments. Indeed, millions of these procedures are conducted yearly worldwide, with their number expected to increase in an ageing and more demanding population. Despite the progress that has been made in optimizing surgical techniques, prosthetic designs, and durability, up to 20% of patients are dissatisfied by the procedure or still report knee pain. From this perspective, the introduction of robotic TKA (R-TKA) in the late 1990s represented a valuable instrument in performing more accurate bone cuts and improving clinical outcomes. On the other hand, prolonged operative time, increased complications, and high costs of the devices slow down the diffusion of R-TKA. The advent of newer technological devices, including those using navigation systems, has made robotic surgery in the operatory room more common since the last decade. At present, many different robots are available, representing promising solutions to avoid persistent knee pain after TKA. We hereby describe their functionality, analyze potential benefits, and hint at future perspectives in this promising field.

We developed a 3D camera system to track motion in a surgical field. This system has the potential to introduce augmented reality (AR) systems non-invasively, eliminating the need for the invasive AR markers conventionally required. The present study was performed to verify the real-time tracking accuracy of this system, assess the feasibility of integrating this system into the surgical workflow, and establish its potential to enhance the accuracy and efficiency of orthopedic procedures.

To evaluate the accuracy of AR technology using a 3D camera, a forearm bone model was created. The forearm model was depicted using a 3D camera, and its accuracy was verified in terms of the positional relationship with a 3D bone model created from previously imaged CT data. Images of the surgical field (capturing the actual forearm) were taken and saved in nine poses by rotating the forearm from pronation to supination. The alignment of the reference points was computed at the three points of CT versus the three points of the 3D camera, yielding a 3D rotation matrix representing the positional relationship. In the original system, a stereo vision-based 3D camera, with a depth image resolution of 1280×720 pixels, 30 frames per second, and a lens field of view of 64 specifications, with a baseline of 3 cm, capable of optimally acquiring real-time 3D data at a distance of 40-60 cm from the subject was used. In the modified system, the following modifications were made to improve tracking performance: (1) color filter processing was changed from HSV to RGB, (2) positional detection accuracy was modified with supporting marker sizes of 8 mm in diameter, and (3) the detection of marker positions was stabilized by calculating the marker position for each frame. Tracking accuracy was examined with the original system and modified system for the following parameters: differences in the rotation matrix, maximum and minimum inter-reference point errors between CT-based and camera-based 3D data, and the average error for the three reference points.

In the original system, the average difference in rotation matrices was 5.51±2.68 mm. Average minimum and maximum errors were 1.10±0.61 and 15.53±12.51 mm, respectively. The average error of reference points was 6.26±4.49 mm. In the modified system, the average difference in rotation matrices was 4.22±1.73 mm. Average minimum and maximum errors were 0.79±0.49 and 1.94±0.87 mm, respectively. The average error of reference points was 1.41±0.58 mm. In the original system, once tracking failed, it was difficult to recover tracking accuracy. This resulted in a large maximum error in supination positions. These issues were resolved by the modified system. Significant improvements were achieved in maximum errors and average errors using the modified system (P<0.05).

AR technology using a 3D camera was developed. This system allows direct comparisons of 3D data from preoperative CT scans with 3D data acquired from the surgical field using a 3D camera. This method has the advantage of introducing AR into the surgical field without invasive markers.

Augmented reality (AR) has gained popularity in various sectors, including gaming, entertainment, and healthcare. The desire for improved surgical navigation within orthopaedic surgery has led to the evaluation of the feasibility and usability of AR in the operating room (OR). However, the safe and effective use of AR technology in the OR necessitates a proper understanding of its capabilities and limitations. This review aims to describe the fundamental elements of AR, highlight limitations for use within the field of orthopaedic surgery, and discuss potential areas for development.

To date, studies have demonstrated evidence that AR technology can be used to enhance navigation and performance in orthopaedic procedures. General hardware and software limitations of the technology include the registration process, ergonomics, and battery life. Other limitations are related to the human response factors such as inattentional blindness, which may lead to the inability to see complications within the surgical field. Furthermore, the prolonged use of AR can cause eye strain and headache due to phenomena such as the vergence-convergence conflict. AR technology may prove to be a better alternative to current orthopaedic surgery navigation systems. However, the current limitations should be mitigated to further improve the feasibility and usability of AR in the OR setting. It is important for both non-clinicians and clinicians to work in conjunction to guide the development of future iterations of AR technology and its implementation into the OR workflow.

Background and objective With the steady advancement of computer-assisted surgical techniques, the importance of assessing and researching technology related to total knee arthroplasty (TKA) procedures has increased. Augmented reality (AR), a recently proposed next-generation technology, is expected to enhance the precision of orthopedic surgery by providing a more efficient and cost-effective approach. However, the accuracy of image-based AR in TKA surgery has not been established. Therefore, this study aimed to determine whether accurate bone resection can be achieved in TKA surgery using image-based AR. Methods In this study, we replaced traditional CT imaging and reconstructions for creating a bone 3D model by direct 3D scanning of the femur and tibia. The preoperative planning involved identifying anatomical landmarks and determining the surgical details. During surgery, markers were employed to create a local coordinate system for an AR-assisted surgical system using a Polaris camera. This approach helped minimize discrepancies between the 3D model and actual positioning, ensuring accurate alignment. Results The AR-assisted surgery using the image method resulted in fewer errors [average error: 0.32 mm; standard deviation (SD): 0.143] between the bone resection depth of the preoperative surgical plan and the bone model test results. Conclusions Our findings demonstrated the accuracy of bone resectioning by using image-based AR-assisted navigation for TKA surgery. Image-based AR-assisted navigation in TKA surgery is a valuable tool not only for enhancing accuracy by using smart glasses and sensors but also for improving the efficiency of the procedure. Therefore, we anticipate that image-based AR-assisted navigation in TKA surgery will gain wide acceptance in practice.

Computer-assisted systems obtained an increased interest in orthopaedic surgery over the last years, as they enhance precision compared to conventional hardware. The expansion of computer assistance is evolving with the employment of augmented reality. Yet, the accuracy of augmented reality navigation systems has not been determined.

To examine the accuracy of component alignment and restoration of the affected limb's mechanical axis in primary total knee arthroplasty (TKA), utilizing an augmented reality navigation system and to assess whether such systems are conspicuously fruitful for an accomplished knee surgeon.

From May 2021 to December 2021, 30 patients, 25 women and five men, underwent a primary unilateral TKA. Revision cases were excluded. A preoperative radiographic procedure was performed to evaluate the limb's axial alignment. All patients were operated on by the same team, without a tourniquet, utilizing three distinct prostheses with the assistance of the Knee+™ augmented reality navigation system in every operation. Postoperatively, the same radiographic exam protocol was executed to evaluate the implants' position, orientation and coronal plane alignment. We recorded measurements in 3 stages regarding femoral varus and flexion, tibial varus and posterior slope. Firstly, the expected values from the Augmented Reality system were documented. Then we calculated the same values after each cut and finally, the same measurements were recorded radiologically after the operations. Concerning statistical analysis, Lin's concordance correlation coefficient was estimated, while Wilcoxon Signed Rank Test was performed when needed.

A statistically significant difference was observed regarding mean expected values and radiographic measurements for femoral flexion measurements only (Z score = 2.67, P value = 0.01). Nonetheless, this difference was statistically significantly lower than 1 degree (Z score = -4.21, P value < 0.01). In terms of discrepancies in the calculations of expected values and controlled measurements, a statistically significant difference between tibial varus values was detected (Z score = -2.33, P value = 0.02), which was also statistically significantly lower than 1 degree (Z score = -4.99, P value < 0.01).

The results indicate satisfactory postoperative coronal alignment without outliers across all three different implants utilized. Augmented reality navigation systems can bolster orthopaedic surgeons' accuracy in achieving precise axial alignment. However, further research is required to further evaluate their efficacy and potential.

Augmented reality (AR) is a powerful multipurpose tool. With a dedicated visor, AR allows the visualization of a series of information and/or images superimposed on the user's field of vision. For this reason, it was recently introduced as a surgical assistant tool. This single-center study aimed to evaluate the intraoperative outcomes of total knee arthroplasties performed with AR assistance in terms of time required and the difference between preplanned and achieved implant positioning (in terms of tibial cut varus and slope angles).

A total of 76 consecutive patients was selected. Preplanning was performed according to the AR protocol, and the target varus and slope angles were defined to instruct the device, which subsequently guided the tibial cuts intraoperatively. Surgeries were performed starting from the tibial cut, and the time required to perform the calibration, registration, and fixation of the resection block was recorded. The varus and slope angles achieved were recorded to compare with the preplanned ones to determine the means and SDs of the differences.

The mean usage time of the AR tool was 5 ± 1 minutes. Results showed a mean difference of 0.59 ± 0.55° for varus angles and 0.70 ± 0.75° for the slope. For varus angles, the differences were <1° for 96% of the cases. Concerning the slope, 89% of the cases were <1°.

The results showed excellent accuracy of the surgical cuts and a limited increase in surgery duration. Therefore, these outcomes highlighted the potential of this new technology as a valid option for surgical assistance.

Recent advances allow the use of Augmented Reality (AR) for many medical procedures. AR via optical navigators to aid various knee surgery techniques (e.g., femoral and tibial osteotomies, ligament reconstructions or menisci transplants) is becoming increasingly frequent. Accuracy in these procedures is essential, but evaluations of this technology still need to be made. Our study aimed to evaluate the system's accuracy using an in vitro protocol. We hypothesised that the system's accuracy was equal to or less than 1 mm and 1° for distance and angular measurements, respectively. Our research was an in vitro laboratory with a 316 L steel model. Absolute reliability was assessed according to the Hopkins criteria by seven independent evaluators. Each observer measured the thirty palpation points and the trademarks to acquire direct angular measurements on three occasions separated by at least two weeks. The system's accuracy in assessing distances had a mean error of 1.203 mm and an uncertainty of 2.062, and for the angular values, a mean error of 0.778° and an uncertainty of 1.438. The intraclass correlation coefficient was for all intra-observer and inter-observers, almost perfect or perfect. The mean error for the distance's determination was statistically larger than 1 mm (1.203 mm) but with a trivial effect size. The mean error assessing angular values was statistically less than 1°. Our results are similar to those published by other authors in accuracy analyses of AR systems.

For the preparation of surgical procedures in orthopedics and trauma surgery, precise knowledge of imaging and the three-dimensional imagination of the surgeon are of outstanding importance. Image-based, preoperative two-dimensional planning is the gold standard in arthroplasty today. In complex cases, further imaging such as computed tomography (CT) or magnetic resonance imaging is also performed, generating a three-dimensional model of the body region and helping the surgeon in the planning of the surgical treatment. Four-dimensional, dynamic CT studies have also been reported and are available as a complementary tool.

Furthermore, digital aids should generate an improved representation of the pathology to be treated and optimize the surgeon's imagination. The finite element method allows patient-specific and implant-specific parameters to be taken into account in preoperative surgical planning. Intraoperatively, relevant information can be provided by augmented reality without significantly influencing the surgical workflow.

The development of augmented reality (AR) technology allows orthopaedic surgeons to incorporate and visualize surgical data, assisting the execution of both routine and complex surgical operations. Uniquely, AR technology allows a surgeon to view the surgical field and superimpose peri-operative imaging, anatomical landmarks, navigation guidance, and more, all in one view without the need for conjugate gaze between multiple screens. The aim of this literature review was to introduce the fundamental requirements for an augmented reality system and to assess the current applications, outcomes, and potential limitations to this technology.

A literature search was performed using MEDLINE and Embase databases, by two independent reviewers, who then collaboratively synthesized and collated the results of the literature search into a narrative review focused on the applications of augmented reality in major orthopaedic sub-specialties.

Current technology requires that pre-operative patient data be acquired, and AR-compatible models constructed. Intra-operatively, to produce manipulatable virtual images into the user's view in real time, four major components are required including a camera, computer image processing technology, tracking tools, and an output screen. The user is provided with a heads-up display, which is a transparent display, enabling the user to look at both their natural view and the computer-generated images. Currently, high-quality evidence for clinical implementation of AR technology in the orthopaedic surgery operating room is lacking; however, growing in vitro literature highlights a multitude of potential applications, including increasing operative accuracy, improved biomechanical angular and alignment parameters, and potentially reduced operative time.

While the application of AR systems in surgery is currently in its infancy, we anticipate rapid and widespread implementation of this technology in various orthopaedic sub-specialties.