This paper presents a novel method for evaluating a user’s feelings in a master–slave robotic surgical operation. By measuring brain activity, an engineer can quantify the user’s feelings during the operation from a cognitive science perspective. In contrast with conventional methods, the engineer can consider the user’s feelings in designing a robot with intuitive operability. The brain activity measurement method is well suited to not only surgical robots but also all master–slave robots. The objective of this paper is to determine the optimal distance between the slave and endoscope using brain activity measurement. We find that brain activity shows a significant peak when the user controls the virtual arm in a position matching the most natural hand-eye coordination.

In this paper, we propose a graphics processing unit-based efficient surgical algorithm for operating on a human liver by a cavitron ultrasonic surgical aspirator (CUSA) scalpel in a virtual environment built with polyhedral objects in Standard Triangulation Language format. First, using z-buffers of a human liver and a CUSA scalpel in a general-purpose graphics processing unit, we rapidly detect their intersections of rectangular parallelepipeds. Then, depending on the plastic, elastic, and viscous material properties of the operated portion of the liver, we determine the rectangular parallelepiped lengths. From that point, based on the correspondence between a vertex and pixel via the XY-image of the z-buffer, the corresponding vertices of the liver polyhedron are moved along the Z-axis of the z-buffer according to its extended or contracted length of rectangular parallelepipeds. By this function, the liver polyhedron can be efficiently and precisely deformed or cut by the CUSA polyhedron.

This work presents an intraoperative method for registration of 3D ultrasound images to surgical navigation systems. Unlike conventional methods that rely on pre-calibration of ultrasound probe in a laboratory environment using a calibration rig, the proposed method is designed to self-register with a tracking system in an operating room. It exploits intraoperative motion of the surgical instrument to compute the registration function instead of using the known geometry of a phantom structure. To reduce estimation errors arising from poor image quality and uncertainty of image-based position estimations, the pivotal constraint associated with minimally invasive surgeries is imposed as a positional correspondence between the imaging and tracking system. We demonstrated the registration of an ultrasound imaging device to an optical tracker and evaluated the accuracy in a water tank setup. This self-registration framework has potential contribution in the unification of ultrasound image-guidance and tracker-based surgical navigation systems. The ultimate goal is to combine ultrasound image-guidance and tracking systems as an integrated surgical navigation system.

Resection of a pelvic tumor is challenging because of its complex three-dimensional (3D) anatomy and deep-seated location with nearby vital structures. The resection is technically demanding if a custom implant is used for reconstruction of the bone defect as the surgeon needs to ensure the resection margin is sufficiently wide and the orientation of intended resection planes must match that of the custom implant. We describe a novel workflow of performing a partial acetabular resection in a patient with pelvic chondrosarcoma and reconstruction with a custom pelvic implant in a one-step operation. A multi-planar bone resection was virtually planned. A computer-aided design implant that both matched the bone defect and biomechanically evaluated was prefabricated with 3D printing technology. The 3D-printed patient-specific instruments (PSIs) were used to reproduce the same planned resection. The histology of the tumor specimen showed a clear resection margin. The errors of the achieved resection and implant position were deviating (1–4 mm) from the planned. The patient could walk unaided with a good hip function. No tumor recurrence and implant loosening were noted at 11 months after surgery. The use of this novel CT-based method for surgical planning, the engineering software for implant design and validation, together with 3D printing technology for implant and PSI fabrication makes it possible to generate a personalized, biomechanically evaluated implant for accurate reconstruction after a pelvic tumor resection in a one-step operation. Further study in a larger population is needed to assess the clinical efficacy of the workflow in complex bone tumor surgery.

The aim of this study was to assess the rate of collateral soft tissue release required in navigated total knee arthroplasty (TKA) to achieve an intra-operative coronal femoral tibial mechanical axis (FTMA) in extension of 0 ± 2°. The primary outcomes assessed were post-operative coronal plane alignment and rate of collateral soft tissue release. The secondary outcomes were range of motion, function, patient satisfaction, and complication rates at one-year follow-up. This is a prospective study of 224 knees. No exclusions were made on the basis of pathology or severity of deformity. Pre-operative FTMA ranged from 27° valgus to 25° varus (mean: −4.5° SD 7.6). Soft tissue release was carried out in 5 of 224 knees (2.2%). Post-operative weight-bearing radiological FTMA ranged from 7° valgus to 8° varus (mean: −0.4° SD 2.5°). Two hundred and ten knees (96%) were within 0 ± 5° of neutral. At one year, median maximum flexion was 100° (IQR 15°) and extension was 0°; mean post-operative Oxford Knee Score had improved from 42 to 23; and 91% of patients were satisfied or very satisfied, with only 2% being dissatisfied. We have found that in the vast majority of cases, including those with large pre-operative coronal deformity in extension, good outcomes in terms of coronal alignment, range of movement, function and patient satisfaction can be achieved.

Tumors in the pelvic region cause deformation and destruction of bony structures. Because the original pelvic anatomy cannot be adequately assessed at the tumor site, reconstruction with patient-specific implants is required. A widely used strategy for the reconstructive planning is mirroring of the contralateral side. We analyzed the statistical shape model (SSM)-based reconstruction method and compared it with the mirroring approach. Our approach used a gender-specific pelvic SSM (n = 50 for each gender) to generate implant geometries. The main objectives of this study were to analyze and evaluate the virtual anatomical reconstruction of eight tumor-damaged pelvic bones using the SSM approach. We achieved an overall mean deviation distance of 0.89 mm and 1.26 mm for the reconstruction of the equivalent defect in the healthy hemipelvis. Quantitative comparison with the mirroring method showed that the SSM-based reconstruction method reconstructs the defect with the same clinically acceptable accuracy as the mirroring method. The study demonstrates that the presented model can be a valuable tool for the planning of pelvic reconstructive surgery and implant design.

Chondrosarcoma of the pelvis is difficult to treat due to the anatomical location and the high incidence of recurrence. Treatment is primarily surgical, and the surgical margins, based on MSTS criteria, have been shown to be predictive of disease recurrence and mortality. However, too-wide margins can decrease post-operative function. In the presented case, computer assisted surgery (CAS) was used to safely enable a joint-salvaging approach in a modified type 2/3 resection of a grade 2 chondrosarcoma of the os ischium and os pubis. The CAS navigation was vital to achieving the desired safe margins. The current follow-up period is 3.5 years, and the patient is disease-free, with no local recurrences or metastases having been detected. Post-operative function is excellent, with good MSTS and SF36 scores. This outcome is a good example of the value of CAS in certain cases.

The purpose of this computational study was to examine the hemodynamic parameters of the velocity fields, shear stress, pressure and drag force field in the complex aorta system, based on a case of type B aortic dissection. The extra-anatomic reconstruction of the complete aorta and bipolar exclusion of the aneurysm was investigated by computational fluid dynamics. Three different cases of the same patient were analyzed: the existing preoperative condition and two alternative surgical treatment options, cases A and B, involving different distal aorto-aortic anastomosis sites. The three-dimensional Navier-Stokes equations and the continuity equation were solved with an unsteady stabilized finite element method. The aorta and large tube graft geometries were reconstructed based on CT angiography images to generate a patient-specific 3D finite element mesh. The computed results showed velocity profiles with smaller intensity in the aorta than in the graft tube in the postoperative case. The shear stress distribution showed low zones around 0.5 Pa in the aneurysm part of the aorta for all three cases. Pressure distribution and, particularly, drag force had much higher values in the preoperative aneurysm zones (7.37 N) than postoperatively (2.45 N), which provides strong evidence of the hemodynamic and biomechanical benefits of this type of intervention in this specific patient. After assessing the outcome obtained with each of the two alternatives A and B, for which we found no significant difference, it was decided to use option A to treat the patient. In summary, computational studies could complement surgical preoperative risk assessment and provide significant insight into the benefits of different treatment alternatives.

Knowledge of consistent anatomical relationships is an important criterion for establishing registration procedures for orthopedic navigation systems. Based on an analysis of 420 CT data sets, we investigated whether a robust registration of the pelvis in a lateral decubitus position could be achieved based on anatomical relationships. For this purpose, we assessed basic statistics and variation in anatomical parameters. It was found that inter-teardrop and inter-fossa distances exhibit a high degree of consistency in pelvises of the same gender. Additionally, stable relationships were found between the anterior pelvic plane (APP) and other reference planes that rely on acetabular points instead of pubic points. Based on these results, a registration procedure for the pelvis was developed which uses only landmarks that are accessible intra-operatively from the ipsilateral side. The deviation between a standard APP registration and this new registration method was assessed. For a standard cup position (40° inclination, 15° anteversion), the resulting deviations were found to be 0.15 ± 2.86° for inclination and 0.27 ± 3.46° for anteversion. Of the registrations, 99% had cup positions within the Lewinnek safe zone. This shows that accurate lateral pelvis registration based on anatomical relationships is achievable.

Total hip arthroplasty restores lost mobility to patients suffering from osteoarthritis and acute trauma. In recent years, navigated surgery has been used to control prosthetic component placement. Furthermore, there has been increasing research on what constitutes correct placement. This has resulted in the definition of a safe-zone for acetabular cup orientation. However, there is less definition with regard to femoral anteversion and how it should be measured. This study assesses the validity of the femoral anteversion measurement method used in imageless navigation, with particular attention to how the neutral rotation of the femur is defined. CT and gait analysis methodologies are used to validate the reference which defines this neutral rotation, i.e., the ankle epicondyle piriformis (AEP) plane. The findings of this study indicate that the posterior condylar axis is a reliable reference for defining the neutral rotation of the femur. In imageless navigation, when these landmarks are not accessible, the AEP plane provides a useful surrogate to the condylar axis, providing a reliable baseline for femoral anteversion measurement.