Preservation of neural tissue with a formaldehyde-free phenol-based embalming protocol.

The adverse effects formaldehyde fixation has on tissues both gross anatomically and histologically are well documented. Consequently, researchers are seeking alternative embalming techniques that better preserve in vivo characteristics of tissues. Phenol-based embalming is one method that has shown promise in its ability to adequately preserve the in vivo qualities of tissues through preliminary explorations at the gross anatomical level. The literature on phenol-based embalming is currently scarce, especially with regard to its effects on tissues at the microscopic level. For the current study we aimed to document the histologic effects of a formaldehyde-free phenol-based embalming solution on neural tissue, with the hope of providing novel insight into the effects of soft-embalming on tissues at the microscopic level. Cerebral and cerebellar tissue obtained from porcine brains was fixed in phenol- and formaldehyde-based fixatives; the latter served as a control. Fixed samples were processed for histological analysis. The phenol-based embalming solution provided excellent preservation of the cerebral and cerebellar tissue morphology. Of note was the decrease in separation artifact seen in both tissue types relative to the control tissue, as well as anomalous circular artifacts in the white matter. The results of this study indicate that the phenol-based embalming solution preserves neural tissue at the histological level, perhaps superiorly in many aspects when compared to the formaldehyde-fixed samples. Further investigations of both gross anatomy and histology are recommended on the basis of these promising new findings to determine its potential utilities within research and education. Clin. Anat. 32:224-230, 2019. © 2018 Wiley Periodicals, Inc.

Component Position and Metal Ion Levels in Computer-Navigated Hip Resurfacing Arthroplasty.

BACKGROUND: Metal ion levels are used as a surrogate marker for wear in hip resurfacing arthroplasties. Improper component position, particularly on the acetabular side, plays an important role in problems with the bearing surfaces, such as edge loading, impingement on the acetabular component rim, lack of fluid-film lubrication, and acetabular component deformation. There are little data regarding femoral component position and its possible implications on wear and failure rates. The purpose of this investigation was to determine both femoral and acetabular component positions in our cohort of mechanically stable hip resurfacing arthroplasties and to determine if these were related to metal ion levels. METHODS: One hundred fourteen patients who had undergone a computer-assisted metal-on-metal hip resurfacing were prospectively followed. Cobalt and chromium levels, Harris Hip, and UCLA activity scores in addition to measures of the acetabular and femoral component position and angles of the femur and acetabulum were recorded. RESULTS: Significant changes included increases in the position of the acetabular component compared to the native acetabulum; increase in femoral vertical offset; and decreases in global offset, gluteus medius activation angle, and abductor arm angle (P < .05). Multiple regression analysis found no significant predictors of cobalt and chromium metal ion levels. CONCLUSION: Femoral and acetabular components placed in acceptable position failed to predict increased metal ion levels, and increased levels did not adversely impact patient function or satisfaction. Further research is necessary to clarify factors contributing to prosthesis wear.

Comparing conventional and computer-assisted surgery baseplate and screw placement in reverse shoulder arthroplasty.

BACKGROUND: Preoperative planning and intraoperative navigation technologies have each been shown separately to be beneficial for optimizing screw and baseplate positioning in reverse shoulder arthroplasty (RSA) but to date have not been combined. This study describes development of a system for performing computer-assisted RSA glenoid baseplate and screw placement, including preoperative planning, intraoperative navigation, and postoperative evaluation, and compares this system with a conventional approach. MATERIALS AND METHODS: We used a custom-designed system allowing computed tomography (CT)-based preoperative planning, intraoperative navigation, and postoperative evaluation. Five orthopedic surgeons defined common preoperative plans on 3-dimensional CT reconstructed cadaveric shoulders. Each surgeon performed 3 computer-assisted and 3 conventional simulated procedures. The 3-dimensional CT reconstructed postoperative units were digitally matched to the preoperative model for evaluation of entry points, end points, and angulations of screws and baseplate. Values were used to find accuracy and precision of the 2 groups with respect to the defined placement. Statistical analysis was performed by t tests (α = .05). RESULTS: Comparison of the groups revealed no difference in accuracy or precision of screws or baseplate entry points (P > .05). Accuracy and precision were improved with use of navigation for end points and angulations of 3 screws (P < .05). Accuracy of the inferior screw showed a trend of improvement with navigation (P > .05). Navigated baseplate end point precision was improved (P < .05), with a trend toward improved accuracy (P > .05). CONCLUSION: We conclude that CT-based preoperative planning and intraoperative navigation allow improved accuracy and precision for screw placement and precision for baseplate positioning with respect to a predefined placement compared with conventional techniques in RSA.

Image-guided distal radius osteotomy using patient-specific instrument guides.

In this article, we describe a method for computer-assisted distal radius osteotomies in which computer-generated, patient-specific plastic guides are used for intraoperative guidance. Before surgery, the correction and plate location are planned using computed tomography scans for both radii and ulnae, and the planned locations of the distal and proximal drill holes for the plate are saved. A plastic, patient-specific instrument guide is created using a rapid prototyping machine into which a mirror image of intraoperative, accessible bone structure of the distal radius is integrated. This allows for unique positioning of the guide during surgery. For each planned drill location, a guidance hole is incorporated into the guide. During surgery, a conventional incision is made, and the guide is positioned on the radius. The surgeon drills the holes for the plate screws into the intact radius and performs the osteotomy using the conventional technique. Using the predrilled holes, the surgeon affixes the plate to the radius fragments. The guides are easy to integrate into the surgical workflow and minimize the need for intraoperative fluoroscopy for guidance of the procedure.

Volume rendering of three-dimensional fluoroscopic images for percutaneous scaphoid fixation: an in vitro study.

Percutaneous fixation of scaphoid fractures offers potential advantages to cast treatment but can be difficult to perform with conventional two-dimensional imaging. This study aimed to evaluate the use of a novel navigation technique using volume-rendered images derived from intraoperative cone-beam computed tomography imaging, without the need for typical patient-based registration. Randomized in vitro trials in which a guidewire was inserted into a scaphoid model were conducted to compare volumetric navigation to conventional fluoroscopic C-arm (n = 24). Central wire placement, surface breach, procedure time, drilling attempts, and radiation exposure were compared between groups. Compared to conventional percutaneous insertion, navigation achieved equal or significantly better placement of the guidewire with fewer drilling attempts and less radiation exposure. On average, navigation took 74 s longer to perform than the conventional method, which was statistically significant but clinically irrelevant. This evaluation suggests that the technology is promising and may have many clinical benefits including improved fixation placement, fewer complications, and less radiation exposure. The intraoperative workflow is more efficient and eliminates the need for preoperative computed tomography, image segmentation, and patient-based registration typical of traditional navigated procedures.

The aspherical human hip: implication for early osteoarthritis.

One marker for early-onset hip arthritis is femoral acetabular impingement. The current standard way of quantifying impingement is manual calculation of anatomical measures on plain radiographs, including the α-angle. Such measurements are user-dependent and prone to error. We provided a robust computational alternative and proposed using numerical fitting of geometrical shapes. We applied least-squares fitting of an ellipse to the femoral head contour and used the difference between the ellipse axes as a quantification method. The results showed a good correlation between the new measure and previous definitions of the α-angle.

A prospective, randomized assessment of a spatial orientation device in natural orifice transluminal endoscopic surgery.

BACKGROUND: One of the challenges in natural orifice transluminal endoscopic surgery (NOTES) is spatial orientation. The Queen's NOTES group has devised a novel method of orientation by using a magnetic device that passes within an endoscope channel allowing for 3-dimensional imaging of the shape and orientation of the endoscope. OBJECTIVE: To assess the feasibility and utility of a novel orientation device. DESIGN: Randomized, controlled trial. SETTING: Animal research laboratory study on four 25-kg pigs. INTERVENTION: The device was tested by 6 endoscopists and 6 laparoscopic surgeons. Starting at the gastrotomy, the time to identify 4 targets was recorded. Participants were required to identify and touch the gallbladder, the fallopian tube, a clip on the abdominal wall, and the liver edge. Use of the orientation device was randomized for each session. MAIN OUTCOME MEASUREMENTS: Time to identify targets with and without the device. Secondary analysis assessed differences between medical specialties and level of training. RESULTS: The mean time to identify all 4 targets with the device was 75.08 ± 42.68 seconds versus 100.20 ± 60.70 seconds without the device (P <.001). The mean time to identify all 4 targets on the first attempt was 102.29 ± 61.36 seconds versus 72.99 ± 40.19 seconds on the second attempt (P <.001). No differences based on specialty or level of training were identified. LIMITATIONS: Small sample size and simplicity of tasks. CONCLUSION: Regardless of randomization order, both groups were faster with the device. These encouraging results warrant further study using more complex scenarios.

Computed tomography as ground truth for stereo vision measurements of skin.

Although dysesthesia is a common surgical complication, there is no accepted method for quantitatively tracking its progression. To address this, two types of computer vision technologies were tested in a total of four configurations. Surface regions on plastic models of limbs were delineated with colored tape, imaged, and compared with computed tomography scans. The most accurate system used visually projected texture captured by a binocular stereo camera, capable of measuring areas to within 3.4% of the ground-truth areas. This simple, inexpensive technology shows promise for postoperative monitoring of dysesthesia surrounding surgical scars.

On the use of laser scans to validate reverse engineering of bony anatomy.

There is a growing body of evidence to suggest the arthritic hip is an irregularly-shaped, aspherical joint, especially in severely pathological cases. Current methods used to study the shape and motion of the hip in-vivo, are invasive and impractical. This study aimed to assess whether a plastic model of the hip joint can be accurately made from a pelvic CT scan. A cadaver hemi-pelvis was CT imaged and segmented from which a 3D plastic model of the proximal femur and hemi-pelvis were fabricated using rapid-prototyping. Both the plastic model and the cadaver were then imaged using a high-resolution laser scanner. A three-way shape analysis was performed to compare the goodness-of-fit between the cadaver, image segmentation, and the plastic model. Overall, we obtained sub-millimeter fit accuracy between all three hip representations. Shape fit was least favorable in areas where the boundary between cartilage and bone is difficult to distinguish. We submit that rapid-prototyping is an accurate and efficient mechanism for obtaining 3D specimens as a means to further study the irregular geometry of the hip.

Registration stability of physical templates in hip surgery.

We tested the registration stability of individualized templates in a consecutive study with 80 patients undergoing hip-resurfacing surgery. These templates physically encode registration and navigation parameters but do not require a computer during the actual surgery. The surgical target was the placement of the femoral guidance pin during hip resurfacing, which is a difficult and highly variable task using conventional instruments. The drill trajectory for the guidance pin of the femoral component was planned on a 3D computer model of the femur derived from a preoperative computed tomography (CT) scan. A surface-matched drilling template was designed to perform mechanical registration on the bone surface and had a hole for the drill guide; the template was created using a rapid prototyping machine. Intraoperatively, the individualized template was positioned on the patient anatomy and the pin was drilled into the femoral neck. The final achieved pin orientation and position were measured using an optoelectronic CT-based navigation system. The measured mean deviation between planned and actual central pin alignment of 0.05° in valgus and 2.8° in anteversion shows that the proposed individualized templates for hip resurfacing have reliable registration.

Metabolomics patterns of breast cancer tumors using mass spectrometry imaging.

PURPOSE: Intraoperative assessment of surgical margins is important for reducing the rate of revisions in breast conserving surgery for palpable malignant tumors. The hypothesis was that metabolomics methods, based on mass spectrometry, could find patterns of relative abundances of molecules that distinguish clusters of benign tissue and cancer in surgical resections. METHODS: Excisions from 8 patients were used to acquire 112,317 mass spectrometry signals by desorption electrospray ionization. A process of nonnegative matrix factorization and graph decomposition produced clusters that were approximated as affine spaces. Each signal's distance to the affine space of a cluster was used to visualize the clustering. RESULTS: The distance maps were superior to binary clustering in identifying cancer regions. They were particularly effective at finding cancer regions that were discontinuously distributed within benign tissue. CONCLUSIONS: Desorption electrospray ionization mass spectrometry, which has been shown to be useful intraoperatively, can acquire signals that distinguish malignant from benign breast tissue in surgically excised tumors. The method may be suitable for real-time surgical decisions based on cancer margins.

Computer-assisted hip resurfacing using individualized drill templates.

The goal of this study was to investigate whether individualized templates can provide an accurate and reliable computer-assisted system for femoral component placement during hip resurfacing. A consecutive series of 45 patients were examined. Using a 3-dimensional computer model of the femur, the drill trajectory for the central pin of the stem was planned. A surface-matched plastic drilling template was created using a rapid prototyping machine. This patient-specific drill guide was intraoperatively positioned on the patient anatomy, the central pin was drilled into the femoral neck, and the accuracy of the placement with respect to the planned central pin alignment was measured. With mean deviation between planned and actual central pin alignment of 1.14 degrees in varus and 4.49 degrees in retroversion, individualized templates were as accurate as conventional computer-assisted hip resurfacing.

Misjudgments at the mandibular angle: freehand versus computer-assisted screw positioning.

BACKGROUND: Distraction osteogenesis is a well known and frequently described technique in mandibular deformities. Buried intraoral devices have numerous advantages, but success hinges on precise positioning of the implants. Although computer navigation has repeatedly been described for craniofacial applications, research on navigating the mandibular region is scarce. Navigating the device placement for a mandibular distractor could become a viable method for distraction osteogenesis because of the possibility of certainty in achieving a defined device position. MATERIALS AND METHODS: A clinical situation was simulated by a mandible model mounted inside a phantom head. The screws were positioned according to a virtual plan through transoral and transbuccal approaches, with and without navigation. RESULTS: Without navigation, the mean deviation from the planned position was 4.9 mm (range, 0.9-10.7 mm), with a clear tendency to position the screws in the easy-to-access regions. With navigation, the mean deviation was significantly lower at 1.5 mm (range, 0.1-3.4 mm). CONCLUSIONS: Computer-assisted surgery can provide a high level of accuracy in the region of the mandibular angle, where precision is crucial for buried intraoral distraction devices.

Technical report: Rapid intraoperative reconstruction of cranial implants using additively manufactured moulds.

During craniotomies, a portion of the calvarium or skull is removed to gain access to the intracranial space. When it is not possible to re-implant the flap, surgeons may repair the defect intraoperatively or at a later date. With larger defects being more difficult to repair intraoperatively, we investigated a method for the creation of patient-specific moulds for ad hoc bone flap reconstruction using rapid prototyping. Patient-specific moulds were created based on light scanned models of the defect, using custom software and rapid prototyping. Polymethylmethacrylate bone implants were created for three retrospective craniotomy cases and evaluated based on original flap and skull reconstruction accuracy. Bone implants created using our moulding method reconstruct the original flap and skull with an average reconstruction accuracy of 0.82 and 1.3 mm, respectively. Average skull reconstruction accuracy obtained by surgeons performing freehand implant reconstruction was 1.49 mm. Time needed to generate moulds was between 2 h and 45 min and 6 h and 20 min. Improvements to current printing technology will make this procedure technically feasible for future cranial procedures.

Reliability of a novel 3-dimensional computed tomography method for reverse shoulder arthroplasty postoperative evaluation.

BACKGROUND: Long-term function and survival of reverse shoulder arthroplasties (RSAs) are reliant on component positioning and fixation. Conventional postoperative analysis is performed using plain radiographs or 2-dimensional (2D) computed tomography (CT) images. Although 3-dimensional (3D) CT would be preferred, its use is limited by metal artifacts. This study proposes a new 3D CT method for postoperative RSA evaluation and compares its interobserver reliability with conventional methods. MATERIALS AND METHODS: Preoperative and postoperative CT scans, as well as postoperative radiographs, were obtained from 18 patients who underwent RSA implantation; the scapula, implant, and screws were reconstructed as 3D CT models. The postoperative 3D scapula and implant were imported into preoperative coordinates and matched to the preoperative scapula. Standardized scapula coordinates were defined, in which the glenoid baseplate version and inclination angle were measured. The percentage of screw volume in bone was measured from a Boolean intersection operation between the preoperative scapula and screw models. Four independent reviewers performed the measurements using 3D CT and conventional 2D methods. Intraclass correlation coefficients (ICCs) were used to compare the reliability of the methods. RESULTS: The 3D CT method showed excellent reliability (ICC > 0.75) in baseplate inclination (ICC = 0.92), version (ICC = 0.97), and screw volume in bone (ICC = 0.99). Conventional 2D methods demonstrated poor reliability (ICC < 0.4). For radiographs, inclination showed poor reliability (ICC = 0.09) and the screw percentage in bone showed fair reliability (ICC = 0.54). Version was not measured with plain radiographs. For 2D CT slice measurements, inclination showed poor reliability (ICC = 0.02), version showed excellent reliability (ICC = 0.81), and the screw percentage in bone showed poor reliability (ICC = 0.28). CONCLUSION: The new 3D CT-based method for evaluating RSA glenoid implant positioning and screw volume in bone showed excellent reliability and overcame the metal-artifact limitation of postoperative CT and 3D CT reconstruction.

Deformable multimodal registration for navigation in beating-heart cardiac surgery.

PURPOSE: Minimally invasive beating-heart surgery is currently performed using endoscopes and without navigation. Registration of intraoperative ultrasound to a preoperative cardiac CT scan is a valuable step toward image-guided navigation. METHODS: The registration was achieved by first extracting a representative point set from each ultrasound image in the sequence using a deformable registration. A template shape representing the cardiac chambers was deformed through a hierarchy of affine transformations to match each ultrasound image using a generalized expectation maximization algorithm. These extracted point sets were matched to the CT by exhaustively searching over a large number of precomputed slices of 3D geometry. The result is a similarity transformation mapping the intraoperative ultrasound to preoperative CT. RESULTS: Complete data sets were acquired for four patients. Transesophageal echocardiography ultrasound sequences were deformably registered to a model of oriented points with a mean error of 2.3 mm. Ultrasound and CT scans were registered to a mean of 3 mm, which is comparable to the error of 2.8 mm expected by merging ultrasound registration with uncertainty of cardiac CT. CONCLUSION: The proposed algorithm registered 3D CT with dynamic 2D intraoperative imaging. The algorithm aligned the images in both space and time, needing neither dynamic CT imaging nor intraoperative electrocardiograms. The accuracy was sufficient for navigation in thoracoscopically guided beating-heart surgery.

Computer-assisted localization of osteoid osteoma: an initial experience.

This article evaluates our initial experience with computer-assisted localization of osteoid osteoma. Nine patients with osteoid osteoma underwent minimally invasive computer-assisted surgery. Patients were followed prospectively for symptomatic relief and complications for an average of 31 months. Successful localization of osteoid osteoma occurred in 7 of 9 patients. Mean operative time was 88 minutes, and mean time to discharge was 1 day (range: same day to 2 days). No fractures, infections, or neurovascular complications occurred. Minimally invasive computer-assisted surgical excision of osteoid osteoma is a safe and feasible option for the surgical localization of osteoid osteoma. It is especially attractive for lesions located in poorly accessible anatomic sites.

Translatory hip kinematics measured with optoelectronic surgical navigation.

PURPOSE: An optoelectronic surgical navigation system was used to detect small but measurable translational motion of human hip cadavers in high-range passive motions. Kinematic data were also examined to demonstrate the role of soft tissues in constraining hip translation. METHODS: Twelve cadaver hips were scanned using CT, instrumented for navigation, and passively taken through motion assessment. Center of the femoral head was tracked in the acetabular coordinates. Maximum non-impinging translation of the femoral head for each specimen hip was reported. This was repeated for 5 tissue states: whole, exposed to the capsule, partially or fully incised capsule, resection of the ligamentum teres and labrectomy. Femoral motions were compared to the reported value for ideal ball and socket model. RESULTS: Whole and exposed hips underwent maximal translations of [Formula: see text] and [Formula: see text] mm, respectively. These translational motions were statistically significantly different from reported value for a purely spherical joint, [Formula: see text]. Further tissue removal almost always significantly increased maximum non-impingement translational motion with [Formula: see text]. CONCLUSION: We found subtle but definite translations in every cadaver hip. There was no consistent pattern of translation. It is possible to use the surgical navigation systems for the assessment of human hip kinematics intra-operatively and improve the treatment of total hip arthroplasty patients by the knowledge of the fact that their hips translate. Better procedure selection and implantation optimization may arise from improved understanding of the motion of this critically important human joint.

Rectus Capitis Posterior Minor: Histological and Biomechanical Links to the Spinal Dura Mater.

STUDY DESIGN: Serial histological investigation was performed on 10 cadaveric specimens and biomechanical tests were performed on five specimens, both focused on the tissue connexion between the rectus capitis posterior minor (RCPMi) and the spinal dura. OBJECTIVE: This study had two components: to clarify the microscopic structure of the tissue link between RCPMi and the dura mater, and to evaluate the mechanical role of this tissue complex. SUMMARY OF BACKGROUND DATA: Dissection-based and imaging-based reports have suggested a connective tissue link between the RCPMi and the dura mater at the posterior-atlanto-occipital (PAO) level. Existence of this link, and properties, remain unclear. METHODS: Histological investigation: RCPMi muscles, their bony attachments, PAO space, and adjacent spinal dura mater were resected from 10 cadavers. Tissues were subdivided into medial and lateral parts. Serial histological sections were prepared to cover maximum surface area; Masson trichrome stain was used to evaluate the tissue connection. Biomechanical investigation: individualized RCPMi muscles from five cadavers were detached from their origin. Each muscle was loaded incrementally up to 2 kg, with the cervical spine hyperextended. Using a structured light scanner, the dura mater was scanned for each loaded state. Comparison between unloaded and each loaded scanned surface quantified the displacement of the dura mater. RESULTS: Histological investigation confirmed the existence of a connective tissue link between the RCPMi and the dura mater. The biomechanical testing suggests that this tissue link complex can reduce the bulging of the dura mater into the spinal canal, caused during hyperextension, by 53.4% ±â€Š6.9% under RCPMi loading. CONCLUSION: This histological investigation clarified the structure of the tissue link between the RCPMi and the dura mater. The biomechanical testing indicated a potential mechanical function of the RCPMi in regards to the spinal dura mater, which may include a stabilizing role of the dura mater during neck extension. LEVEL OF EVIDENCE: N/A.