Computer-assisted navigation in orthopedic surgery

Rigid point cloud registration based on correspondence cloud for image-to-patient registration in image-guided surgery

BACKGROUND

Image-to-patient registration aligns preoperative images to intra-operative anatomical structures and it is a critical step in image-guided surgery (IGS). The accuracy and speed of this step significantly influence the performance of IGS systems. Rigid registration based on paired points has been widely used in IGS, but studies have shown its limitations in terms of cost, accuracy, and registration time. Therefore, rigid registration of point clouds representing the human anatomical surfaces has become an alternative way for image-to-patient registration in the IGS systems.

PURPOSE

We propose a novel correspondence-based rigid point cloud registration method that can achieve global registration without the need for pose initialization. The proposed method is less sensitive to outliers compared to the widely used RANSAC-based registration methods and it achieves high accuracy at a high speed, which is particularly suitable for the image-to-patient registration in IGS.

METHODS

We use the rotation axis and angle to represent the rigid spatial transformation between two coordinate systems. Given a set of correspondences between two point clouds in two coordinate systems, we first construct a 3D correspondence cloud (CC) from the inlier correspondences and prove that the CC distributes on a plane, whose normal is the rotation axis between the two point clouds. Thus, the rotation axis can be estimated by fitting the CP. Then, we further show that when projecting the normals of a pair of corresponding points onto the CP, the angle between the projected normal pairs is equal to the rotation angle. Therefore, the rotation angle can be estimated from the angle histogram. Besides, this two-stage estimation also produces a high-quality correspondence subset with high inlier rate. With the estimated rotation axis, rotation angle, and the correspondence subset, the spatial transformation can be computed directly, or be estimated using RANSAC in a fast and robust way within only 100 iterations.

RESULTS

To validate the performance of the proposed registration method, we conducted experiments on the CT-Skull dataset. We first conducted a simulation experiment by controlling the initial inlier rate of the correspondence set, and the results showed that the proposed method can effectively obtain a correspondence subset with much higher inlier rate. We then compared our method with traditional approaches such as ICP, Go-ICP, and RANSAC, as well as recently proposed methods like TEASER, SC2-PCR, and MAC. Our method outperformed all traditional methods in terms of registration accuracy and speed. While achieving a registration accuracy comparable to the recently proposed methods, our method demonstrated superior speed, being almost three times faster than TEASER.

CONCLUSIONS

Experiments on the CT-Skull dataset demonstrate that the proposed method can effectively obtain a high-quality correspondence subset with high inlier rate, and a tiny RANSAC with 100 iterations is sufficient to estimate the optimal transformation for point cloud registration. Our method achieves higher registration accuracy and faster speed than existing widely used methods, demonstrating great potential for the image-to-patient registration, where a rigid spatial transformation is needed to align preoperative images to intra-operative patient anatomy.

Optimizing Acetabular Positioning: A Comprehensive Review of Contemporary Strategies in Total Hip Arthroplasty

Total hip arthroplasty (THA) is a widely practiced surgical intervention to alleviate pain and reinstate functionality in individuals afflicted with hip joint pathology. The positioning of the acetabulum assumes paramount significance in determining the efficacy of THA, exerting profound influences on biomechanical dynamics, stability, and the durability of outcomes over time. This comprehensive review meticulously evaluates contemporary methodologies for optimizing acetabular positioning in THA, encompassing advanced technologies such as computer-assisted navigation systems, patient-specific instrumentation, robotic-assisted surgical approaches, image-based planning techniques, and intraoperative fluoroscopy. Crucially, key discoveries underscore the pivotal role of precise acetabular alignment in mitigating complications such as dislocation, component wear, and impingement. Moreover, the implications for clinical practice accentuate the imperative of continuous education and training to ensure effective deployment of sophisticated methodologies. Recommendations for furthering research and enhancing practice development underscore the necessity of scrutinizing long-term prognoses, assessing cost-effectiveness, and embracing technological innovations perpetually refining THA outcomes. Collaborative endeavors among researchers, practitioners, and industry stakeholders emerge as indispensable drivers of advancement in this domain, fostering an environment conducive to elevating the standard of care for individuals undergoing THA.

Clinical evaluation of a fluoroscopic image-based laser guidance system in bone tumor surgery: A technical note

This study presents a laser guidance system developed to enhance surgical accuracy and reduce radiation exposure in orthopedic surgeries. The system can project the actual position corresponding to the appointed position selected by the surgeon on a fluoroscopic image using a line laser and has laser projection ability to mark the corresponding point using a line laser. The surgeon does not have to perform anatomical marker placement for calibration. Three patients with bone tumors underwent surgeries using the laser guidance system, and the projection accuracy was evaluated by measuring the distance error between the appointed and laser-marking positions. The installation time, including calibration, was also assessed for clinical usability. The average projection accuracy in bone tumor surgery was 2.86 mm, and the average installation time was 7 min. These results demonstrate that the laser guidance system, with a projection error of <3 mm, could be useful in bone tumor surgeries.

ArthroNavi framework: stereo endoscope-guided instrument localization for arthroscopic minimally invasive surgeries

Significance

As an example of a minimally invasive arthroscopic surgical procedure, arthroscopic osteochondral autograft transplantation (OAT) is a common option for repairing focal cartilage defects in the knee joints. Arthroscopic OAT offers considerable benefits to patients, such as less post-operative pain and shorter hospital stays. However, performing OAT arthroscopically is an extremely demanding task because the osteochondral graft harvester must remain perpendicular to the cartilage surface to avoid differences in angulation.

Aim

We present a practical ArthroNavi framework for instrument pose localization by combining a self-developed stereo endoscopy with electromagnetic computation, which equips surgeons with surgical navigation assistance that eases the operational constraints of arthroscopic OAT surgery.

Approach

A prototype of a stereo endoscope specifically fit for a texture-less scene is introduced extensively. Then, the proposed framework employs the semi-global matching algorithm integrating the matching cubes method for real-time processing of the 3D point cloud. To address issues regarding initialization and occlusion, a displaying method based on patient tracking coordinates is proposed for intra-operative robust navigation. A geometrical constraint method that utilizes the 3D point cloud is used to compute a pose for the instrument. Finally, a hemisphere tabulation method is presented for pose accuracy evaluation.

Results

Experimental results show that our endoscope achieves 3D shape measurement with an accuracy of < 730    μ m . The mean error of pose localization is 15.4 deg (range of 10.3 deg to 21.3 deg; standard deviation of 3.08 deg) in our ArthroNavi method, which is within the same order of magnitude as that achieved by experienced surgeons using a freehand technique.

Conclusions

The effectiveness of the proposed ArthroNavi has been validated on a phantom femur. The potential contribution of this framework may provide a new computer-aided option for arthroscopic OAT surgery.

Augmented Reality Navigation Can Achieve Accurate Coronal Component Alignment During Total Knee Arthroplasty

Background Computer-navigated knee arthroplasty has been shown to improve accuracy over conventional instruments. The next generation of computer assistance is being developed using augmented reality. The accuracy of augmented reality navigation has not been established. Methods From April 2021 to October 2021, a prospective, consecutive series of 20 patients underwent total knee arthroplasty utilising an augmented reality-assisted navigation system (ARAN). The coronal and sagittal alignment of the femoral and tibial bone cuts was measured using the ARAN and the final position of the components was measured on postoperative CT scans. The absolute difference between the measurements was recorded to determine the accuracy of the ARAN. Results Two cases were excluded due to segmentation errors, leaving 18 cases for analysis. The ARAN produced a mean absolute error of 1.4°, 2.0°, 1.1° and 1.6° for the femoral coronal, femoral sagittal, tibial coronal and tibial sagittal alignments, respectively. No outliers (absolute error of >3°) were identified in femoral coronal or tibial coronal alignment measurements. Three outliers were identified in tibial sagittal alignment, with all cases demonstrating less tibial slope (by 3.1°, 3.3° and 4°). Five outliers were identified in femoral sagittal alignment and in all cases, the component was more extended (3.1°, 3.2°, 3.2°, 3.4° and 3.9°). The mean operative time significantly decreased from the first nine augmented reality cases to the final nine cases by 11 minutes (p<0.05). There was no difference in the accuracy between the early and late ARAN cases. Conclusion Augmented reality navigation can achieve accurate alignment of total knee arthroplasty with a low rate of component malposition in the coronal plane. Acceptable and consistent accuracy can be achieved from the initial adoption of this technique, however, some sagittal outliers were identified and there is a clear learning curve with respect to operating time. The level of evidence was IV.

A comparison of utilization and short-term complications of technology-assisted versus conventional total knee arthroplasty

Background

While technology-assisted total knee arthroplasty (TA-TKA) improves implant positioning, whether it confers improved clinical outcomes remains inconclusive. We sought to examine national TA-TKA utilization trends and to compare outcomes between TA-TKA and unassisted TKA (U-TKA).

Methods

Patients who underwent primary, elective TKA from 2010 to 2018 were identified using the American College of Surgeons National Surgical Quality Improvement Program (NSQIP) database. Demographic, perioperative, and 30-day outcomes were collected. Patients were stratified on the basis of whether they underwent TA-TKA, which included computer navigation and robotics, or U-TKA. The proportion of patients undergoing TKA using TA-TKA was calculated. One-to-one propensity-score matching paired patients undergoing TA-TKA or U-TKA. Independent samples t-tests and Mann–Whitney U tests were used to compare continuous variables, and chi-squared tests were used to compare categorical variables.

Results

Of the 402,284 TKA patients, 10,429 (2.6%) cases were performed using TA-TKA. Comparing the unmatched TA-TKA and U-TKA groups, race (p < 0.001), smoking status (p = 0.050), baseline functional status (p < 0.001), and body mass index (BMI) (p < 0.001) significantly differed. Propensity-score matching yielded 8633 TA-TKA and U-TKA pairs. The TA-TKA cohort had shorter hospital length of stay (LOS) (2.7 ± 2.5 versus 2.8 ± 1.9 days, p = 0.017) but similar operative times (92.4 ± 33.4 versus 92.6 ± 39.8 min, p = 0.670). Compared with the U-TKA group, the TA-TKA group had lower major complication (7.6% versus 9.4%, p < 0.001) and transfusion (3.9% versus 5.1%, p < 0.001) rates and higher rates of discharge to home (73.9% versus 70.4%, p < 0.001). Reoperation and readmission rates did not significantly differ between groups.

Conclusions

TA-TKA utilization remains low among orthopedic surgeons. Compared with U-TKA, TA-TKA yielded improved perioperative and 30-day outcomes. Nonetheless, surgeons must consider the benefits and drawbacks of TA-TKA when determining the proper surgical technique and technology for each patient.

Level III evidence

Retrospective cohort study.

Computer-Assisted Navigation for Complex Revision of Unstable Total Hip Replacement in a Patient With Post-traumatic Arthritis

Imageless computer-assisted navigation (CAN) excels in the post-traumatic arthritis and complex revision case setting when altered anatomy and landmarks are inaccurate references for cup positioning. We describe the case of an adult male patient who suffered an acetabular fracture which was treated nonoperatively. He subsequently developed post-traumatic arthritis and underwent an anterior approach total hip arthroplasty 25 years later. Postoperatively, he developed recurrent hip instability due to malpositioned components. We describe the use of imageless CAN during revision total hip arthroplasty to correct malpositioned components, with 3-year follow-up without dislocation. In these complex cases, CAN reduces the risk of component malpositioning and joint instability.

How accurately can surgeons perform angle manipulation? Quantitative assessment of the accuracy of manual angle manipulation of orthopedic surgery: a cadaver study

INTRODUCTION

To date, only few studies have been performed on the accuracy of manual angle manipulation during orthopedic surgery. This cadaver study was aimed at quantitatively assessing the accuracy of manual angle manipulation performed by orthopedic surgeons according to their surgical experience and comparing it with manipulation performed with the assistance of a digital goniometer.

MATERIALS AND METHODS

Six lower-leg specimens of fresh-frozen human cadavers were subjected to angle manipulation performed via Kirschner wire (K-wire) insertion. K-wires were inserted manually and with the assistance of a digital goniometer at target angles of 0°, 30°, and 60° by three operators who had different levels of experience in orthopedic surgery. The accuracy of the insertion angles at the target angles was evaluated using computed tomography.

RESULTS

The mean angle error in the manual angle manipulation was 8.8° (standard deviation [SD] 6.0). When the target angles were set to 0°, 30°, and 60°, the identified angle errors were 6.1° (SD 4.3), 8.8° (SD 6.6), and 11.7° (SD 5.6), respectively, and each value did not show any significant difference among the operators. With the assistance of a digital goniometer, the mean (SD) angle error was significantly improved to 2.1° (1.1°) (p < 0.001). The amount of improvement in accuracy significantly increased as the target angle increased (p = 0.01).

CONCLUSION

This cadaver study quantified the inaccuracy of manual angle manipulation in orthopedic surgery and showed that these inaccuracies ​​can be improved using an assistive device. These results support the need to develop a device that can compensate manual angle manipulation in orthopedic surgery.

Smoothing the Undersampled Carpal Bone Model with Small Volume and Large Curvature: A Feasibility Study

The carpal bones are eight small bones with irregularities and high curvature on their surfaces. The 3D model of the carpal bone serves as the foundation of further clinical applications, e.g., wrist kinematic behavior. However, due to the limitation of the Magnetic Resonance Imaging (MRI) technique, reconstructed carpal bone models are discretely undersampled, which has dramatic stair-step effects and leads to abnormal meshes on edges or surfaces, etc. Our study focuses on determining the viability of various smoothing techniques for a carpal model reconstructed by in vivo gathered MR images. Five algorithms, namely the Laplacian smoothing algorithm, the Laplacian smoothing algorithm with pre-dilation, the scale-dependent Laplacian algorithm, the curvature flow algorithm, and the inverse distance algorithm, were chosen for evaluation. The assessment took into account the Relative Volume Difference and the Hausdorff Distance as well as the surface quality and the preservation of morphological and morphometric properties. For the five algorithms, we analyzed the Relative Volume Difference and the Hausdorff Distance for all eight carpal bones. Among all the algorithms, the scale-dependent Laplacian method processed the best result regarding surface quality and the preservation of morphological and morphometric properties. Based on our extensive examinations, the scale-dependent Laplacian algorithm is suitable for the undersampled carpal bone model with small volume and large curvature.

Comparison of Utilization and Short-term Complications Between Technology-assisted and Conventional Total Hip Arthroplasty

INTRODUCTION

Although technology-assisted total hip arthroplasty (TA-THA) may improve implant positioning, it remains unknown whether TA-THA confers improved clinical outcomes. We sought to examine national TA-THA utilization trends and compare clinical outcomes between TA-THA and unassisted THA (U-THA).

METHODS

Patients who underwent primary, elective THA from 2010 to 2018 were identified using the American College of Surgeons National Surgical Quality Improvement Program database. Demographic, perioperative, and 30-day outcomes were queried and collected. Patients were stratified based on whether they underwent TA-THA, which included computer navigation or robotics, and U-THA. Propensity score matching paired patients undergoing TA-THA or U-THA on a 1:1 basis.

RESULTS

Of the 238,755 THA patients, 3,149 cases (1.3%) were done using TA-THA. Comparing the unmatched TA-THA and U-THA groups, race distribution (P < 0.001) and baseline functional status (P < 0.001) differed. Propensity score matching yielded 2,335 TA-THA and U-THA pairs. Perioperatively, the TA-THA cohort had longer mean surgical times (101.0 ± 34.0 versus 91.9 ± 38.8 minutes, P < 0.001), but lower transfusion rates (5.7% versus 7.8%, P = 0.005). As compared with the U-THA group, the TA-THA group had a shorter mean hospital length of stay (2.0 ± 1.1 versus 2.5 ± 2.0 days, P < 0.001) and a higher proportion of patients discharged home (85.8% versus 75.7%, P < 0.001). Notably, the TA-THA cohort had higher readmission rates (3.8% versus 2.4%, P < 0.001). Major complication and revision surgery rates did not markedly differ between groups.

DISCUSSION

TA-THA utilization rates remain low among orthopaedic surgeons. As compared with U-THA, TA-THA yield mixed perioperative and 30-day outcomes. Surgeons must consider the clinical benefits and drawbacks of TA-THA when determining the proper surgical technique and technology for each patient. Clinical trials assessing long-term functional and clinical outcomes between U-THA and TA-THA are required to further elucidate the utility of assistive technologies in THA.

LEVEL III EVIDENCE

Retrospective Cohort Study.

Navigated multiplanar osteotomies for spinal primary bone tumors

Background:

Establishing the proper diagnosis and rendering appropriate treatment of spinal primary bone tumors (SPBT) can result in definitive cures. Notably, malignant, or benign SPBT (i.e., with aggressive local behavior) generally require en bloc resection. Osteotomies of the vertebral body in more than 1 plane may avoid critical structures, preserve nerve functions, and reduce the volume of healthy bone resected. Here, our objective was to report how we planned and performed navigated multiplanar osteotomies for en bloc resection of 14 SPBT.

Methods:

We performed a retrospective analysis of 14 patients with malignant or locally aggressive benign SPBT operated on consecutively between 2014 and 2019 utilizing preoperative 3D planning/navigation. Tumors were resected in an en bloc fashion utilizing multiplanar osteotomies. Patients were followed for a minimum of 12 postoperative months.

Results:

Diagnoses included three benign but locally aggressive bone tumors (i.e., all osteoblastomas) and 11 primary sarcomas (i.e., six chordomas and five chondrosarcomas). Eleven tumors involved the sacrum and the other three, the thoracic spine. In 12 patients, the en bloc margins were classified as marginal (<1 cm), and in two patients, as wide (>1 cm). Intraoperative navigation facilitated the performance of 40 osteotomies in 14 patients (median = 2.9, range = 2–6).

Conclusion:

Navigated multiplanar osteotomies increased the precision and safety of en bloc resections for 14 primary spinal bone tumors SPBT that included 11 malignant and three benign/locally aggressive lesions.

The Use of Computer Navigation and Patient Specific Instrumentation in Shoulder Arthroplasty: Everyday Practice, Just for Special Cases or Actually Teaching a Surgeon?

Background:

The use of computer assisted surgery, navigation (NAV) in shoulder arthroplasty is still under discussion, regarding the clinical outcome and prosthesis longevity, especially when combining these factors with cost, time and surgeon’s experience. Beside the NAV, there has been in use patient-specific instrumentation (PSI) as an additional tool for more precise glenoid implant position. Surgical NAV and PSI for glenoid implant positioning in anatomic and reverse total shoulder arthroplasty are in last years under observation and discussion.

Objective:

To critically review and evaluate the current literature regarding the use of computer navigation and PSI in shoulder arthroplasty.

Methods:

Critical review of the existing literature.

Results:

Cost-effectiveness, prosthesis longevity and revision arthroplasty rate have not yet been proven clinically. Moreover, heterogeneity is high in studies that include different positioning systems (NAV, PSI and standard instrumentation). Heterogeneity is due to differences in surgical technique, implants, surgeon’s expertise, radiographic image analysis technique.

Conclusion:

The use of navigation systems and PSI should be clinically proven in the shoulder arthroplasty. Independent experts’ opinion and independent high level studies lack at the moment. There will be still a lot of talk regarding this topic in future.

Surgical navigation for challenging recurrent or pretreated intra-abdominal and pelvic soft tissue sarcomas

BACKGROUND

This study assessed whether electromagnetic navigation can be of added value during resection of recurrent or post-therapy intra-abdominal/pelvic soft tissue sarcomas (STS) in challenging locations.

MATERIALS AND METHODS

Patients were included in a prospective navigation study. A pre-operatively 3D roadmap was made and tracked using electromagnetic reference markers. During the operation, an electromagnetic pointer was used for the localization of the tumor/critical anatomical structures. The primary endpoint was feasibility, secondary outcomes were safety and usability.

RESULTS

Nine patients with a total of 12 tumors were included, 7 patients with locally recurrent sarcoma. Three patients received neoadjuvant radiotherapy and three other patients received neoadjuvant systemic treatment. The median tumor size was 4.6 cm (2.4-10.4). The majority of distances from tumor to critical anatomical structures was <0.5 cm. The tumors were localized using the navigation system without technical or safety issues. Despite the challenging nature of these resections, 89% were R0 resections, with a median blood loss of 100 ml (20-1050) and one incident of vascular damage. Based on the survey, surgeons stated navigation resulted in shorter surgery time and made the resections easier.

CONCLUSION

Electromagnetic navigation facilitates resections of challenging lower intra-abdominal/pelvic STS and might be of added value.

2D-3D reconstruction of distal forearm bone from actual X-ray images of the wrist using convolutional neural networks

The purpose of the study was to develop a deep learning network for estimating and constructing highly accurate 3D bone models directly from actual X-ray images and to verify its accuracy. The data used were 173 computed tomography (CT) images and 105 actual X-ray images of a healthy wrist joint. To compensate for the small size of the dataset, digitally reconstructed radiography (DRR) images generated from CT were used as training data instead of actual X-ray images. The DRR-like images were generated from actual X-ray images in the test and adapted to the network, and high-accuracy estimation of a 3D bone model from a small data set was possible. The 3D shape of the radius and ulna were estimated from actual X-ray images with accuracies of 1.05 ± 0.36 and 1.45 ± 0.41 mm, respectively.

A Projector-Based Augmented Reality Navigation System for Computer-Assisted Surgery

In the medical field, guidance to follow the surgical plan is crucial. Image overlay projection is a solution to link the surgical plan with the patient. It realizes augmented reality (AR) by projecting computer-generated image on the surface of the target through a projector, which can visualize additional information to the scene. By overlaying anatomical information or surgical plans on the surgery area, projection helps to enhance the surgeon's understanding of the anatomical structure, and intuitively visualizes the surgical target and key structures of the operation, and avoid the surgeon's sight diversion between monitor and patient. However, it still remains a challenge to project the surgical navigation information on the target precisely and efficiently. In this study, we propose a projector-based surgical navigation system. Through the gray code-based calibration method, the projector can be calibrated with a camera and then be integrated with an optical spatial locator, so that the navigation information of the operation can be accurately projected onto the target area. We validated the projection accuracy of the system through back projection, with average projection error of 3.37 pixels in x direction and 1.51 pixels in y direction, and model projection with an average position error of 1.03 ± 0.43 mm, and carried out puncture experiments using the system with correct rate of 99%, and qualitatively analyzed the system's performance through the questionnaire. The results demonstrate the efficacy of our proposed AR system.

Real-time acoustic sensing and artificial intelligence for error prevention in orthopedic surgery

In this work, we developed and validated a computer method capable of robustly detecting drill breakthrough events and show the potential of deep learning-based acoustic sensing for surgical error prevention. Bone drilling is an essential part of orthopedic surgery and has a high risk of injuring vital structures when over-drilling into adjacent soft tissue. We acquired a dataset consisting of structure-borne audio recordings of drill breakthrough sequences with custom piezo contact microphones in an experimental setup using six human cadaveric hip specimens. In the following step, we developed a deep learning-based method for the automated detection of drill breakthrough events in a fast and accurate fashion. We evaluated the proposed network regarding breakthrough detection sensitivity and latency. The best performing variant yields a sensitivity of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$93.64 \pm 2.42$$\end{document}93.64±2.42% for drill breakthrough detection in a total execution time of 139.29\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\hbox { ms}}$$\end{document}ms. The validation and performance evaluation of our solution demonstrates promising results for surgical error prevention by automated acoustic-based drill breakthrough detection in a realistic experiment while being multiple times faster than a surgeon’s reaction time. Furthermore, our proposed method represents an important step for the translation of acoustic-based breakthrough detection towards surgical use.

Computer-assisted surgery (CAS) in orthopedic oncology. Which were the indications, problems and results in our first consecutive 203 patients?

AIMS

to review a group of patients with primary bone tumors treated with intraoperative navigation and analyze: (1) The technical problems; (2) Indications for Computer Assisted Surgery (CAS); (3) Oncological results; (4) Non oncological complications.

MATERIALS AND METHODS

All patients from a single institution who had preoperative virtual planned for an oncological primary bone resection assisted with navigation between May 2010 and July 2017 were enrolled in the study (203 patients). The use of computer-assisted surgery (CAS) was classified according to the oncologic procedure performed: (1) intralesional resections, (2) en-block resections, and (3) en-block resections + navigated allograft reconstructions.

RESULTS

Four patients (4/203, 2%) of the series presented technical problems which came from 2 software and 2 hardware crashes. Eight (4%) procedures were intralesional resections and no local recurrences or complications were reported in this group. Ninety-eight surgeries (49%) were pure en block resection. The pelvis and sacrum were the main location in this group (57%). All bone margins were defined negative but 2 patients presented a positive resection in the soft tissues. Infection was the most prevalent complication (16/23). Ninety-three procedures were done for en block resections + allograft reconstruction (all extremities tumor). All margins were free of tumor and non oncological rate for this group was 28%.

CONCLUSION

The main indications for CAS were malignant bone tumors resection. The technical failures precluded navigation use in 2%. CAS for pure en-block resections were mainly indicated in pelvic and sacrum tumors while en-block resection + allograft reconstruction assisted with navigation were only indicated in extremities tumors.

LEVEL OF EVIDENCE

IV.

Influence of a purpose-built frame on the accuracy of computer-assisted orthopedic surgery of equine extremities

OBJECTIVE

To determine the influence of a purpose-built frame on the accuracy of screw placement during computer-assisted orthopedic surgery (CAOS) of the equine extremity.

STUDY DESIGN

Experimental cadaveric study.

SAMPLE POPULATION

Twenty-four paired equine cadaveric limbs obtained from seven horses.

METHODS

Three 4.5-mm cortex screws were inserted in lag technique in three different planes of orientation in the proximal phalanx (P1) by means of CAOS. In the study group (n = 12 limbs), the tracker was anchored on a purpose-built frame designed to stabilize the extremity. In the control group (n = 12 limbs), a conventional tracker array was used that was anchored directly on P1. The stability of both tracker arrays was assessed during the procedure by using fiducial markers. After screw placement, preoperative and postoperative computed tomographic images were assessed to measure surgical accuracy aberrations (SAA) between the planned and achieved screw position. Descriptive statistics and repeated-measures analysis of variance were performed to compare SAA measurements between the study and control group.

RESULTS

Both tracker arrays remained consistently stable in all specimens. Mean overall SAA of screw insertion were lower in the study group (0.7 mm; median, 0.5; range 0-3.4) than in the control group (1.2 mm; median, 0.9; range, 0-4.2 mm).

CONCLUSION

The mean SAA achieved in cortex screw placement using CAOS lies within the range of approximately 1 mm. The use of a purpose-built frame avoided additional drilling of the target bone and improved surgical accuracy compared with the conventional tracker array.

CLINICAL SIGNIFICANCE

The purpose-built frame described in this report can be used to facilitate CAOS in equine orthopedics without compromising surgical accuracy.

A review of computer-assisted orthopaedic surgery systems

BACKGROUND

Computer-assisted orthopaedic surgery systems have great potential, but no review has focused on computer-assisted surgery systems for the spine, hip, and knee.

METHODS

A systematic search was performed in Web of Science and PubMed. We searched the literature on computer-assisted orthopaedic surgery systems from 2008 to the present and focused on three aspects of systems: training, planning, and intraoperative navigation.

RESULTS AND DISCUSSION

In this review study, we reviewed 34 surgical training systems, 31 surgical planning systems, and 41 surgical navigation systems. The functions and characteristics of the surgical systems were compared and analysed, and the current concerns about and the impact of the surgical systems on doctors and surgery were clarified.

CONCLUSION

Computer-assisted orthopaedic surgery systems are still in the development stage. Future surgical training systems should include synthetic models with patient anatomy. Surgical planning systems with automatic planning should be developed, and surgical navigation systems with multimodal fusion, robotic assistance and imaging should be developed.

Validation of an optical, computer-assisted technique for intraoperative tracking of 3-dimensional canine stifle joint motion

Background:

Cranial cruciate ligament (CCL) rupture is the most common orthopedic pathology in dog and in men. In human, optical computer-assisted technique is considered as a repeatable and reliable method for the biomechanical assessment of joint kinematics and laxity in case of CCL surgery.

Aim:

To evaluate the repeatability and reliability afforded by clinical tests in terms of laxity measured by means of a computer-assisted tracking system in two canine CCL conditions: CCL-Intact, CCL-Deficient.

Methods:

Fourteen fresh frozen canine stifles were passively subjected to Internal/External (IE) rotation at 120° of flexion and Cranial drawer test (CC). To quantify the repeatability and the reliability, intra-class correlation coefficient (ICC) and the mean percent error were evaluated (Δ r %).

Results:

The study showed a very good intra-class correlation, before and after CCL resection for kinematics tests. It was found a minimum ICC = 0.73 during the IE rotation in CCL-Intact and a maximum value of ICC = 0.97 for the CC displacement in CC-Deficient. IE rotation with CCL-Intact is the condition with the greatest Δ r % = 14%, while the lowest Δ r % = 6% was obtained for CC displacement in CCL-Deficient.

Conclusion:

The presented work underlined the possibility of using a computer-assisted method also for biomechanical studies concerning stifle kinematics and laxity.

Validation of the registration accuracy of navigation-assisted arthroscopic débridement for elbow osteoarthritis

BACKGROUND

The identification and precise removal of bony impingement lesions during arthroscopic débridement arthroplasty for elbow osteoarthritis is technically difficult. Surgical navigation systems, combined with preoperative 3-dimensional (3D) assessment of bony impingements, can provide real-time tracking of the surgical instruments and impingement lesions. This study aims to determine the registration accuracy of the navigation system for the humerus and ulna during elbow arthroscopy.

METHODS

We tested the registration procedure using resin bone models of 3 actual patients with elbow osteoarthritis. We digitized bone surface points using navigation pointers under arthroscopy. We initially performed paired-point registration, digitizing 6 preset anatomical landmarks, and then refined the initial alignment with surface matching registration, digitizing 30 points. The registration accuracy for each trial was evaluated as the mean target registration error in each reference marker. Three observers repeated the registration procedure 5 times each with the 3 specimens (total, 45 trials). The median of the registration accuracy was evaluated in total (45 trials) as the accuracy of the registration procedure. The differences in the registration accuracy among the 3 observers (median of 15 trials) were also examined.

RESULTS

The total registration accuracies were 0.96 mm for the humerus and 0.85 mm for the ulna. No significant differences were found in the registration accuracy for the humerus and ulna among the 3 observers.

CONCLUSIONS

This arthroscopic-assisted registration procedure is sufficiently feasible and accurate for application of the navigation system to arthroscopic débridement arthroplasty in clinical settings.

Optical and Electromagnetic Tracking Systems for Biomedical Applications: A Critical Review on Potentialities and Limitations

Optical and electromagnetic tracking systems represent the two main technologies integrated into commercially-available surgical navigators for computer-assisted image-guided surgery so far. Optical Tracking Systems (OTSs) work within the optical spectrum to track the position and orientation, i.e., pose of target surgical instruments. OTSs are characterized by high accuracy and robustness to environmental conditions. The main limitation of OTSs is the need of a direct line-of-sight between the optical markers and the camera sensor, rigidly fixed into the operating theatre. Electromagnetic Tracking Systems (EMTSs) use electromagnetic field generator to detect the pose of electromagnetic sensors. EMTSs do not require such a direct line-of-sight, however the presence of metal or ferromagnetic sources in the operating workspace can significantly affect the measurement accuracy. The aim of the proposed review is to provide a complete and detailed overview of optical and electromagnetic tracking systems, including working principles, source of error and validation protocols. Moreover, commercial and research-oriented solutions, as well as clinical applications, are described for both technologies. Finally, a critical comparative analysis of the state of the art which highlights the potentialities and the limitations of each tracking system for a medical use is provided.

[Value of virtual reality technology in preoperative planning of transtrochanteric curved varus osteotomy for avascular necrosis of femoral head in adults]

OBJECTIVE

To research the value of virtual reality (VR) technology in the preoperative planning of transtrochanteric curved varus osteotomy for avascular necrosis of the femoral head (ANFH) in adults.

METHODS

Between June 2018 and November 2018, 7 patients (11 hips) with ANFH, who were treated with transtrochanteric curved varus osteotomy, were enrolled in the study. There were 4 males (7 hips) and 3 females (4 hips) with an average age of 31.9 years (range, 14-46 years). Among them, 3 patients were unilateral ANFH and 4 patients were bilateral ANFH. There was 1 patient (1 hip) of traumatic ANFH, 2 patients (4 hips) of alcohol-induced ANFH, 2 patients (3 hips) of hormonal ANFH, and 2 patients (3 hips) of idiopathic ANFH. All hips were Association Research Circulation Osseous (ARCO) stage Ⅲ. There were 5 hips for Japanese Investigation Committee (JIC) type C1 and 6 hips for type C2. There were 5 hips for China-Japan Friendship Hospital (CJFH) type L1,1 for type L2, and 5 for type L3. The disease duration ranged from 5 to 12 months (mean, 8 months). Preoperative Harris score was 53.91±7.66. The neck-shaft angle ranged from 128 to 143° (mean, 133.9°). VR technology was adopted for the preoperative planning. CT data were imported into the software to construct the morphology of necrotic area, and the transrtrochanteric varus osteotomy was simulated. The varus angle was designed according to the integrity rate of femoral head. The planned varus angle was 6 to 16° (mean, 9.7°). The transtrochanteric curved varus osteotomy was performed according to the preoperative planning, and the varus angle and loading area were confirmed under fluoroscopy. If the planned varus angle was too small, it would continue to increase under the fluoroscopy until a satisfactory varus angle. Postoperative changes of the neck-shaft angle were calculated and compared with the preoperative planned varus angle (error). The hip function was assessed by using the Harris score.

RESULTS

All incisions healed by first intention. All patients were followed up 6-11 months with an average of 8 months. The X-ray film at 2 days after operation showed that the neck-shaft angle was 112-135° (mean, 123.4°). The difference of the neck-shaft angle between pre- and post-operation was 6-16° (mean, 11.0°). Among them, the difference of the neck-shaft angle was consistent with planned varus angle in 5 hips, while the error of the remaining 6 hips was 1-4°. There was 1 patient (1 hip) of osteotomy nonunion at 4 months after operation, 1 patient (1 hip) of proximal femur fracture at 2 months after operation. The rest 5 patients (9 hips) obtained union at the osteotomy. At last follow-up, the Harris score was 82.18±16.35, showing significant difference when compared with preoperative score ( t=-5.195, P=0.000).

CONCLUSION

VR technology is a brand-new preoperative planning method for transtrochanteric curved varus osteotomy in treating ANFH.

Multiple instruments motion trajectory tracking in optical surgical navigation

Optical surgical navigation system has been a hot research topic because of its high accuracy. This paper focuses on identifying and tracking multiple surgical instruments to meet the requirements of applying multiple surgical instruments in clinical medicine. The methods of instrument identification based on the marker's geometrical arrangement and instrument tracking based on markers' motion vector were applied in the proposed algorithm. The experiments of multiple instruments' identification and tracking, the instruments' stability, the space distance and rotation of a pair of instruments at the same tracking time were performed to verify the proposed algorithm. The stereoscopic camera is applied to capture images, and two 850 nm filters are added in front of the binocular camera. The tracking experiment shows that ten instruments can be fully and accurately identified, and then all of them can be quickly and accurately tracked at the same time. A pair of instruments is simultaneously measured in the stability test, such as the typical surgical instrument (TSI) and the miniature surgical instrument (MSI). The ranges of standard deviations (SD) of the stability test for the TSI in the X-, Y-, and Z- axes are from 0.016 mm to 0.127 mm, from 0.011 mm to 0.090 mm, and from 0.124 mm to 0.901 mm, respectively. And the ranges of SDs for the MSI's stability test are from 0.011 mm to 0.133 mm in the X-axis, from 0.010 mm to 0.106 mm in the Y-axis, and from 0.093 mm to 0.932 mm in the Z-axis. The sub-millimeter SDs show that the proposed algorithm has a high stability. Moreover, the space distance test and the rotation test were performed for simultaneously tracking TSI and MSI. All experimental results indicate the proposed algorithm is able to meet the clinical accuracy requirements.

Mini-open excision of osteoid osteoma using intraoperative O-arm/Stealth navigation

BACKGROUND

Although osteoid osteomas have traditionally been treated by surgical excision, radiofrequency ablation (RFA) has gained favor as a less invasive procedure. However, RFA is contraindicated for osteoid osteomas close to the skin or crucial neurovascular structures, and is not covered by national health insurance in Japan. The aim of the present study was to evaluate the efficacy of surgical excision of osteoid osteomas using intraoperative navigation.

METHODS

We performed a retrospective review of five patients with osteoid osteoma who underwent a mini-open excision using O-arm/Stealth navigation at our institution. The osteoid osteomas were excised using a cannulated cutter or curetted out with the assistance of navigation.

RESULTS

Complete excision was achieved in all patients, which was confirmed by pathological examination. The mean skin incision was 2.1 cm (range, 1.5 to 3.0 cm) and the mean duration required for setup three-dimensional image was 15 min (range, 12 to 20 min). Although the mean visual analog scale score was 7 (range, 4 to 8) before surgery, all patients experienced relief from their characteristic pain immediately after surgery, with the mean scores of 2.2 (range, 1 to 3) and 0 at 2 days and 4 weeks after surgery, respectively. There was no intra-operative complication related to the navigation and no recurrence was observed during the mean follow-up period of 25 months (range, 13 to 33 months).

CONCLUSIONS

Mini-open excision using intraoperative O-arm/Stealth navigation is a safe and accurate procedure for patients with osteoid osteoma, which could cover the limitation of RFA.

Up-to-date intraoperative computer assisted solutions for liver surgery

Computer assisted surgical planning allowed for a better selection of patients, evaluation of operative strategy, appropriate volumetric measurements, identification of anatomical risks, definition of tumour resection margins and choice of surgical approach in liver oncologic resections and living donor liver transplantations. Although preoperative computer surgical analysis has been widely used in daily clinical practice, intraoperative computer assisted solutions for risk analysis and navigation in liver surgery are not widely available or still under clinical evaluation. Computer science technology can efficiently assist modern surgeons during complex liver operations, mainly by providing image guidance with individualized 2D images and 3D models of the various anatomical and pathological structures of interest. Intraoperative computer assisted liver surgery is particularly useful in complex parenchyma-sparing hepatectomies, for intraoperative risk analysis and for the effective treatment of colorectal metastases after neoadjuvant therapy or when they are multiple. In laparoscopic liver surgery, intraoperative computer aid is definitively more important as, apart from a restricted field of view, there is also loss of the fine haptic feedback. Intraoperative computer assisted developments face challenges that prevent their application in daily clinical practice. There is a vast variety of studies regarding intraoperative computer assisted liver surgery but there are no clear objective measurements in order to compare them and select the most effective solutions. An overview of up-to-date intraoperative computer assisted solutions for liver surgery will be discussed.

Intraoperative O-arm-navigated resection in musculoskeletal tumors

BACKGROUND

Although emerging evidence has suggested that computer-assisted navigation allows surgeons to plan the optimal level of resection without compromising the surgical margins, the precise accuracy of the procedures has been unclear. The aim of this study was to investigate the accuracy and safety of the musculoskeletal tumor resection using O-arm/Stealth intraoperative navigation assistance.

METHODS

A retrospective study of six patients with bone and soft tissue tumors who underwent surgical resection using O-arm/Stealth navigation system was performed. The histological diagnosis was osteosarcoma, metastatic bone tumor, leiomyosarcoma, undifferentiated sarcoma, and synovial sarcoma, respectively. Tumor resection was performed according to planned osteotomy planes determined on O-arm/Stealth three-dimensional intraoperative images. The resection accuracy, length of time for the procedures, surgical margins, and perioperative complications were evaluated.

RESULTS

The distances between the entry and exit points for the planned and actual cuts were 1.5 ± 0.3 mm and 2.3 ± 0.3 mm, respectively, and the mean discrepancy of the osteotomy angle was 2.8 ± 1.2°. The mean length of time required for navigation was 14 min. A histological examination revealed clear margins in all patients. There were no complications related to navigation, and no patients developed local recurrence during a mean follow-up of 30.6 months.

CONCLUSIONS

The O-arm/Stealth intraoperative CT navigation system provides safe and accurate osteotomy in musculoskeletal tumor resections. However, surgeons should keep in mind and be careful of minimal errors during osteotomy, which are around 2 mm from the planned line.

Feasibility of A-mode ultrasound based intraoperative registration in computer-aided orthopedic surgery: A simulation and experimental study

PURPOSE

A fast and accurate intraoperative registration method is important for Computer-Aided Orthopedic Surgery (CAOS). A-mode ultrasound (US) is able to acquire bone surface data in a non-invasive manner. To utilize A-mode US in CAOS, a suitable registration algorithm is necessary with a small number of registration points and the presence of measurement errors. Therefore, we investigated the effects of (1) the number of registration points and (2) the Ultrasound Point Localization Error (UPLE) on the overall registration accuracy.

METHODS

We proposed a new registration method (ICP-PS), including the Iterative Closest Points (ICP) algorithm and a Perturbation Search algorithm. This method enables to avoid getting stuck in the local minimum of ICP iterations and to find the adjacent global minimum. This registration method was subsequently validated in a numerical simulation and a cadaveric experiment using a 3D-tracked A-mode US system.

RESULTS

The results showed that ICP-PS outperformed the standard ICP algorithm. The registration accuracy improved with the addition of ultrasound registration points. In the numerical simulation, for 25 sample points with zero UPLE, the averaged registration error of ICP-PS reached 0.25 mm, while 1.71 mm for ICP, decreasing by 85.38%. In the cadaver experiment, using 25 registration points, ICP-PS achieved an RMSE of 2.81 mm relative to 5.84 mm for the ICP, decreasing by 51.88%.

CONCLUSIONS

The simulation approach provided a well-defined framework for estimating the necessary number of ultrasound registration points and acceptable level of UPLE for a given required level of accuracy for intraoperative registration in CAOS. ICP-PS method is suitable for A-mode US based intraoperative registration. This study would facilitate the application of A-mode US probe in registering the point cloud to a known shape model, which also has the potential for accurately estimating bone position and orientation for skeletal motion tracking and surgical navigation.

A Novel Ultrasound-Based Lower Extremity Motion Tracking System

Tracking joint motion of the lower extremity is important for human motion analysis. In this study, we present a novel ultrasound-based motion tracking system for measuring three-dimensional (3D) position and orientation of the femur and tibia in 3D space and quantifying tibiofemoral kinematics under dynamic conditions. As ultrasound is capable of detecting underlying bone surface noninvasively through multiple layers of soft tissues, an integration of multiple A-mode ultrasound transducers with a conventional motion tracking system provides a new approach to track the motion of bone segments during dynamic conditions. To demonstrate the technical and clinical feasibilities of this concept, an in vivo experiment was conducted. For this purpose the kinematics of healthy individuals were determined in treadmill walking conditions and stair descending tasks. The results clearly demonstrated the potential of tracking skeletal motion of the lower extremity and measuring six-degrees-of-freedom (6-DOF) tibiofemoral kinematics and related kinematic alterations caused by a variety of gait parameters. It was concluded that this prototyping system has great potential to measure human kinematics in an ambulant, non-radiative, and noninvasive manner.

[Clinical application of computer-assisted cannulated screw internal fixation system based on error correction method for femoral neck fractures]

Objective

To investigate the clinical efficacy of computer-assisted cannulated screw internal fixation system based on error correction method for femoral neck fractures.

Methods

A retrospective analysis was made on the clinical data of 20 femoral neck fracture patients treated by computer-assisted cannulated screw internal fixation system based on error correction method between January 2014 and October 2015 (trial group), and 36 femoral neck fracture patients undergoing traditional manual surgery with closed reduction by cannulated screw fixation in the same period (the control group). There was no significant difference in gender, age, injury cause, side of fracture, types of fracture, and time from injury to operation between 2 groups ( P>0.05). The operation time, intraoperative blood loss, intraoperative frequency of fluoroscopy and guide pin insertion, fracture healing time, fracture healing rate, and Harris hip score were compared between 2 groups.

Results

All incisions healed by first intention after operation, and no complication of blood vessel and nerve injury occurred. The operation time of trial group was significantly longer than that of control group ( t=2.290, P=0.026), however, the intraoperative blood loss, intraoperative frequency of fluoroscopy and guide pin insertion of trial group were significantly less than those of control group ( t=-10.650, P=0.000; t=18.320, P=0.000; t=-16.625, P=0.000). All patients were followed up 12-18 months (mean, 14.7 months). X-ray films showed that fracture healing was obtained in 2 groups, showing no significant difference in fracture healing time between 2 groups ( t=0.208, P=0.836). No complication of ischemic necrosis of femoral head occurred during follow-up period. At last follow-up, the Harris hip score was 87.05±3.12 in trial group and was 86.78±2.83 in control group, showing no significant difference ( t=0.333, P=0.741).

Conclusion

Computer-assisted cannulated screw internal fixation surgery based on error correction method for femoral neck fractures is better than traditional manual surgery in decreasing intraoperative radiation and surgical trauma during operation.

Biocompatible Near-Infrared Three-Dimensional Tracking System

A fundamental challenge in soft-tissue surgery is that target tissue moves and deforms, becomes occluded by blood or other tissue, and is difficult to differentiate from surrounding tissue. We developed small biocompatible near-infrared fluorescent (NIRF) markers with a novel fused plenoptic and NIR camera tracking system, enabling three-dimensional tracking of tools and target tissue while overcoming blood and tissue occlusion in the uncontrolled, rapidly changing surgical environment. In this work, we present the tracking system and marker design and compare tracking accuracies to standard optical tracking methods using robotic experiments. At speeds of 1 mm/s, we observe tracking accuracies of 1.61 mm, degrading only to 1.71 mm when the markers are covered in blood and tissue.

What Is the Expected Learning Curve in Computer-assisted Navigation for Bone Tumor Resection?

BACKGROUND

Computer navigation during surgery can help oncologic surgeons perform more accurate resections. However, some navigation studies suggest that this tool may result in unique intraoperative problems and increased surgical time. The degree to which these problems might diminish with experience-the learning curve-has not, to our knowledge, been evaluated for navigation-assisted tumor resections.

QUESTIONS/PURPOSES

(1) What intraoperative technical problems were observed during the first 2 years using navigation? (2) What was the mean time for navigation procedures and the time improvement during the learning curve? (3) Have there been any differences in the accuracy of the registration technique that occurred over time? (4) Did navigation achieve the goal of achieving a wide bone margin?

METHODS

All patients who underwent preoperative virtual planning for tumor bone resections and operated on with navigation assistance from 2010 to 2012 were prospectively collected. Two surgeons (GLF, LAA-T) performed the intraoperative navigation assistance. Both surgeons had more than 5 years of experience in orthopaedic oncology with more than 60 oncology cases per year per surgeon. This study includes from the very first patients performed with navigation. Although they did not take any formal training in orthopaedic oncology navigation, both surgeons were trained in navigation for knee prostheses. Between 2010 and 2012, we performed 124 bone tumor resections; of these, 78 (63%) cases were resected using intraoperative navigation assistance. During this period, our general indications for use of navigation included pelvic and sacral tumors and those tumors that were reconstructed with massive bone allografts to obtain precise matching of the host and allograft osteotomies. Seventy-eight patients treated with this technology were included in the study. Technical problems (crashes) and time for the navigation procedure were reported after surgery. Accuracy of the registration technique was defined and the surgical margins of the removed specimen were determined by an experienced bone pathologist after the surgical procedure as intralesional, marginal, or wide margins. To obtain these data, we performed a chart review and review of operative notes.

RESULTS

In four patients (of 78 [5%]), the navigation was not completed as a result of technical problems; all occurred during the first 20 cases of the utilization of this technology. The mean time for navigation procedures during the operation was 31 minutes (range, 11-61 minutes), and the early navigations took more time (the regression analysis shielded R² = 0.35 with p < 0.001). The median registration error was 0.6 mm (range, 0.3-1.1 mm). Registration did not improve over time (the regression analysis slope estimate is -0.014, with R² = 0.026 and p = 0.15). Histological examinations of all specimens showed a wide bone tumor margin in all patients. However, soft tissue margins were wide in 58 cases and marginal in 20.

CONCLUSIONS

We conclude that navigation may be useful in achieving negative bony margins, but we cannot state that it is more effective than other means for achieving this goal. Technical difficulty precluded the use of navigation in 5% of cases in this series. Navigation time decreased with more experience in the procedure but with the numbers available, we did not improve the registration error over time. Given these observations and the increased time and expense of using navigation, larger studies are needed to substantiate the value of this technology for routine use.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

INTRAOPERATIVE IMAGE NAVIGATION: EXPERIMENTAL STUDY OF THE FEASIBILITY AND SURGEON PREFERENCE BETWEEN A STERILE ENCASED NINTENDO WIITM REMOTE AND STANDARD WIRELESS COMPUTER MOUSE

Diagnostic imaging plays an important role in the operating room, providing surgeons with a reference and surgical plan. Surgeon autonomy in the operating room has been suggested to decrease errors that stem from communication mistakes. A standard computer mouse was compared to a wireless remote-control style controller for computer game consoles (Wiimote) for the navigation of diagnostic imaging studies by sterile personnel in this prospective survey study. Participants were recruited from a cohort of residents and faculty that use the surgical suites at our institution. Outcome assessments were based on survey data completed by study participants following each use of either the mouse or Wiimote, and compared using an analysis of variance. The mouse was significantly preferred by the study participants in the categories of handling, accuracy and efficiency, and overall satisfaction (P <0.05). The mouse was preferred to both the Wiimote and to no device, when participants were asked to rank options for image navigation. This indicates the need for the implementation of intraoperative image navigation devices, to increase surgeon autonomy in the operating room.

A Smart Tool for Intraoperative Leg Length Targeting in Total Hip Arthroplasty: A Retrospective Cohort Study

BACKGROUND

Leg length discrepancies following total hip arthroplasty (THA) may necessitate subsequent interventions, from heel lifts to revision surgery. Current intraoperative methods of determining leg length are either inaccurate or expensive and invasive.

OBJECTIVE

The objective of the current study was to investigate the ability of a novel, intraoperative smart tool (Intellijoint HIP^®, Intellijoint Surgical^®, Inc., Waterloo, ON) to provide accurate, real-time leg length measurements during THA.

METHODS

We retrospectively reviewed the medical records of 25 patients who underwent THA utilizing the Intellijoint HIP smart tool between February and August 2014. Intraoperative leg length data was compared with radiographic leg length calculations. Two observers blinded to the Intellijoint HIP findings independently assessed all post-procedure radiographs.

RESULTS

The mean difference between smart tool and radiographic measurements was 1.3 mm [CI: -0.1, 2.7]. 88% (22/25) of intraoperative measurements were within 5 mm of radiographic measurements; 100% (25/25) were within 10 mm. A Bland-Altman analysis showed excellent agreement, with 96% (24/25) of measurements within the statistical limit for acceptable agreement, and 84% (21/25) within the clinically acceptable range (± 5 mm). Removal of the first 13 procedures (surgeon training) decreased the mean difference between methods to 0.6 mm [-0.6, 1.9]. All post-training procedures were associated with a difference of <5 mm. There were no reported adverse events related to the use of the smart tool.

CONCLUSION

The Intellijoint HIP smart tool is a safe and accurate tool for providing intraoperative measurements of leg length in real-time.

Intraoperative 3-Dimensional Computed Tomography and Navigation in Foot and Ankle Surgery

Computer-assisted orthopedic surgery has developed dramatically during the past 2 decades. This article describes the use of intraoperative 3-dimensional computed tomography and navigation in foot and ankle surgery. Traditional imaging based on serial radiography or C-arm-based fluoroscopy does not provide simultaneous real-time 3-dimensional imaging, and thus leads to suboptimal visualization and guidance. Three-dimensional computed tomography allows for accurate intraoperative visualization of the position of bones and/or navigation implants. Such imaging and navigation helps to further reduce intraoperative complications, leads to improved surgical outcomes, and may become the gold standard in foot and ankle surgery. [Orthopedics.2016; 39(5):e1005-e1010.].

The current status and future prospects of computer-assisted hip surgery

The advances in computer assistance technology have allowed detailed three-dimensional preoperative planning and simulation of preoperative plans. The use of a navigation system as an intraoperative assistance tool allows more accurate execution of the preoperative plan, compared to manual operation without assistance of the navigation system. In total hip arthroplasty using CT-based navigation, three-dimensional preoperative planning with computer software allows the surgeon to determine the optimal angle of implant placement at which implant impingement is unlikely to occur in the range of hip joint motion necessary for daily activities of living, and to determine the amount of three-dimensional correction for leg length and offset. With the use of computer navigation for intraoperative assistance, the preoperative plan can be precisely executed. In hip osteotomy using CT-based navigation, the navigation allows three-dimensional preoperative planning, intraoperative confirmation of osteotomy sites, safe performance of osteotomy even under poor visual conditions, and a reduction in exposure doses from intraoperative fluoroscopy. Positions of the tips of chisels can be displayed on the computer monitor during surgery in real time, and staff other than the operator can also be aware of the progress of surgery. Thus, computer navigation also has an educational value. On the other hand, its limitations include the need for placement of trackers, increased radiation exposure from preoperative CT scans, and prolonged operative time. Moreover, because the position of a bone fragment cannot be traced after osteotomy, methods to find its precise position after its movement need to be developed. Despite the need to develop methods for the postoperative evaluation of accuracy for osteotomy, further application and development of these systems are expected in the future.

Computer algorithms for three-dimensional measurement of humeral anatomy: analysis of 140 paired humeri

BACKGROUND

In the presence of severe osteoarthritis, osteonecrosis, or proximal humeral fracture, the contralateral humerus may serve as a template for the 3-dimensional (3D) preoperative planning of reconstructive surgery. The purpose of this study was to develop algorithms for performing 3D measurements of the humeral anatomy and further to assess side-to-side (bilateral) differences in humeral head retrotorsion, humeral head inclination, humeral length, and humeral head radius and height.

METHODS

The 3D models of 140 paired humeri (70 cadavers) were extracted from computed tomographic data. Geometric characteristics quantifying the humeral anatomy in 3D were determined in a semiautomatic fashion using the developed computer algorithms. The results between the sides were compared for evaluating bilateral differences.

RESULTS

The mean bilateral difference of the humeral retrotorsion angle was 6.7° (standard deviation [SD], 5.7°; range, -15.1° to 24.0°; P = .063); the mean side difference of the humeral head inclination angle was 2.3° (SD, 1.8°; range, -5.1° to 8.4°; P = .12). The side difference in humeral length (mean, 2.9 mm; SD, 2.5 mm; range, -8.7 mm to 10.1 mm; P = .04) was significant. The mean side difference in the head sphere radius was 0.5 mm (SD, 0.6 mm; range, -3.2 mm to 2.2 mm; P = .76), and the mean side difference in humeral head height was 0.8 mm (SD, 0.6 mm; range, -2.4 mm to 2.4 mm; P = .44).

CONCLUSIONS

The contralateral anatomy may serve as a reliable reconstruction template for humeral length, humeral head radius, and humeral head height if it is analyzed with 3D algorithms. In contrast, determining humeral head retrotorsion and humeral head inclination from the contralateral anatomy may be more prone to error.

Augmented Reality for Assistance of Total Knee Replacement

The aim of this work was the development of a surgical assistance system based on augmented reality to support joint replacement procedures and implantation of prosthetic knee. Images of the scene were captured in order to detect the visual markers located on the lateral surface of the patient’s leg for overlapping the 3D models of the prosthesis and the joint, as well as the tool used by the medical specialist. With the marker identification, it was possible to compute its position and orientation for locating the virtual models, obtaining a monitoring system for giving accurate information about the procedure. Also it can be used as training platform for surgeons, without having volunteers or patients for performing real surgeries; instead they can train in a virtual environment. The results have shown an efficient system in terms of cost-benefit relation, taking into account the materials used for developing the system; nevertheless, the accuracy of the algorithm decreases according to the distance between the markers.

Does intraoperative navigation assistance improve bone tumor resection and allograft reconstruction results?

BACKGROUND

Bone tumor resections for limb salvage have become standard treatment. Recently, computer-assisted navigation has been introduced to improve the accuracy of joint arthroplasty and possible tumor resection surgery; however, like with any new technology, its benefits and limitations need to be characterized for surgeons to make informed decisions about whether to use it.

QUESTIONS/PURPOSES

We wanted to (1) assess the technical problems associated with computer-assisted navigation; (2) assess the accuracy of the registration technique; (3) define the time required to perform a navigated resection in orthopedic oncology; and (4) the frequency of complications such as local recurrence, infection, nonunion, fracture, and articular collapse after tumor resection and bone reconstruction with allografts using intraoperative navigation assistance.

METHODS

We analyzed 69 consecutive patients with bone tumors of the extremities that were reconstructed with massive bone allografts using intraoperative navigation assistance with a minimum followup of 12 months (mean, 29 months; range, 12-43 months). All patients had their tumors reconstructed in three-dimensional format in a virtual platform and planning was performed to determine the osteotomy position according to oncology margins in a CT-MRI image fusion. Tumor resections and allograft reconstructions were performed using a computer navigation system according to the previously planned cuts. We analyzed intraoperative data such as technical problems related to the navigation procedure, registration technique error, length of time for the navigation procedure, and postoperative complications such as local recurrence, infection, nonunion, fracture, and articular collapse.

RESULTS

In three patients (4%), the navigation was not carried out as a result of technical problems. Of the 66 cases in which navigation was performed, the mean registration error was 0.65 mm (range, 0.3-1.2 mm). The mean required time for navigation procedures, including bone resection and allograft reconstruction during surgery, was 35 minutes (range, 18-65 minutes). Complications that required a second surgical procedure were recorded for nine patients including one local recurrence, one infection, two fractures, one articular collapse, and four nonunions. In two of these nine patients, the allograft needed to be removed. At latest followup, three patients died of their original disease.

CONCLUSIONS

The navigation procedure could not be performed for technical reasons in 4% of the series. The mean registration error was 0.65 mm in this series and the navigation procedure itself adds a mean of 35 minutes during surgery. The complications rate for this series was 14%. We found a nonunion rate of 6% in allograft reconstructions when we used a navigation system for the cuts.

LEVEL OF EVIDENCE

Level IV, case series. See the Guidelines for Authors for a complete description of levels of evidence.