A Hybrid 3D-2D Image Registration Framework for Pedicle Screw Trajectory Registration between Intraoperative X-ray Image and Preoperative CT Image.

Pedicle screw insertion is considered a complex surgery among Orthopaedics surgeons. Exclusively to prevent postoperative complications associated with pedicle screw insertion, various types of image intensity registration-based navigation systems have been developed. These systems are computation-intensive, have a small capture range and have local maxima issues. On the other hand, deep learning-based techniques lack registration generalizability and have data dependency. To overcome these limitations, a patient-specific hybrid 3D-2D registration principled framework was designed to map a pedicle screw trajectory between intraoperative X-ray image and preoperative CT image. An anatomical landmark-based 3D-2D Iterative Control Point (ICP) registration was performed to register a pedicular marker pose between the X-ray images and axial preoperative CT images. The registration framework was clinically validated by generating projection images possessing an optimal match with intraoperative X-ray images at the corresponding control point registration. The effectiveness of the registered trajectory was evaluated in terms of displacement and directional errors after reprojecting its position on 2D radiographic planes. The mean Euclidean distances for the Head and Tail end of the reprojected trajectory from the actual trajectory in the AP and lateral planes were shown to be 0.6-0.8 mm and 0.5-1.6 mm, respectively. Similarly, the corresponding mean directional errors were found to be 4.90 and 20. The mean trajectory length difference between the actual and registered trajectory was shown to be 2.67 mm. The approximate time required in the intraoperative environment to axially map the marker position for a single vertebra was found to be 3 min. Utilizing the markerless registration techniques, the designed framework functions like a screw navigation tool, and assures the quality of surgery being performed by limiting the need of postoperative CT.

Realistic C-arm to pCT registration for vertebral localization in spine surgery : A hybrid 3D-2D registration framework for intraoperative vertebral pose estimation.

Spine surgeries are vulnerable to wrong-level surgeries and postoperative complications because of their complex structure. Unavailability of the 3D intraoperative imaging device, low-contrast intraoperative X-ray images, variable clinical and patient conditions, manual analyses, lack of skilled technicians, and human errors increase the chances of wrong-site or wrong-level surgeries. State of the art work refers 3D-2D image registration systems and other medical image processing techniques to address the complications associated with spine surgeries. Intensity-based 3D-2D image registration systems had been widely practiced across various clinical applications. However, these frameworks are limited to specific clinical conditions such as anatomy, dimension of image correspondence, and imaging modalities. Moreover, there are certain prerequisites for these frameworks to function in clinical application, such as dataset requirement, speed of computation, requirement of high-end system configuration, limited capture range, and multiple local maxima. A simple and effective registration framework was designed with a study objective of vertebral level identification and its pose estimation from intraoperative fluoroscopic images by combining intensity-based and iterative control point (ICP)-based 3D-2D registration. A hierarchical multi-stage registration framework was designed that comprises coarse and finer registration. The coarse registration was performed in two stages, i.e., intensity similarity-based spatial localization and source-to-detector localization based on the intervertebral distance correspondence between vertebral centroids in projected and intraoperative X-ray images. Finally, to speed up target localization in the intraoperative application, based on 3D-2D vertebral centroid correspondence, a rigid ICP-based finer registration was performed. The mean projection distance error (mPDE) measurement and visual similarity between projection image at finer registration point and intraoperative X-ray image and surgeons' feedback were held accountable for the quality assurance of the designed registration framework. The average mPDE after peak signal to noise ratio (PSNR)-based coarse registration was 20.41mm. After the coarse registration in spatial region and source to detector direction, the average mPDE reduced to 12.18mm. On finer ICP-based registration, the mean mPDE was finally reduced to 0.36 mm. The approximate mean time required for the coarse registration, finer registration, and DRR image generation at the final registration point were 10 s, 15 s, and 1.5 min, respectively. The designed registration framework can act as a supporting tool for vertebral level localization and its pose estimation in an intraoperative environment. The framework was designed with the future perspective of intraoperative target localization and its pose estimation irrespective of the target anatomy.

Cryptococcal spondylodiscitis in a non-HIV patient with CD4 lymphocytopenia.

Infections that affect the intervertebral discs and vertebrae are known as spondylodiscitis. Such infections are commonly caused by pyogenic organisms, particularly Staphylococcus aureus, and hematogenous spread is the most common route. Non-pyogenic infections include Mycobacterium tuberculosis and Brucellosis. Mycotic infections are becoming more common, in line with the growing number of immunodeficiency disorders. Cryptococcus is included among these mycotic infections. We present a case of such an infection in a non-immunocompromised patient with a known history of treatment with antitubercular therapy. A 52-year-old man came to our hospital with a backache of one-month duration and progressive neurological deficits of the lower limbs of one-week duration. His imaging studies were suggestive of spondylodiscitis at the D10-11 and D11-12 levels with a left paraspinal abscess. The patient underwent anterolateral decompression, biopsy, and instrumented posterior spinal fusion. The pus grew Cryptococcus, and histopathology confirmed Cryptococcal spondylodiscitis. The patient was treated with parenteral amphotericin B and fluconazole. A mycotic infection must be considered in the differential diagnosis of infectious spondylodiscitis.

Operation theatre protocol for COVID-19 cases requiring orthopaedic surgery: A workflow without altering the existing infrastructure.

INTRODUCTION: The surge in the number of trauma cases following relaxation of lockdowns in the backdrop of COVID-19 pandemic, has strained the existing infrastructure to cater to these patients and also prevent the spread of infection. Moreover, with the rise of newer strains, the period ahead has to be tread carefully to prevent resurgence of infections. There have been recommendations regarding the ideal setup to operate orthopaedic cases in this pandemic scenario. However, many of the hospitals in India with financial and logistic constraints are unable to implement these structural changes into their existing setup. We propose a model which can be used in an existing operation theatre which has a single entry and exit corridor, which is the layout in many hospitals. METHODOLOGY: A protocol with the consultation of a panel of health care professionals was designed on the basis of WHO guidelines in a way so as to remain dynamic. Prior to its implementation, online classes were conducted and a dry run of the protocol was done with the whole team involved. The theatre layout is one with a single entry and exit and had predesignated rooms. The personnel were divided into 3 teams, each with a fixed set of people and preset workflow, to be followed during entry and exit. Five COVID positive cases have been operated since then using the protocol and has been used as a pilot study to further amend the protocol. CONCLUSION: This model can be used as a guideline by hospitals having a limited infrastructure, to develop their own protocol to operate on COVID positive cases, in the present situation of increasing trauma cases post the relaxation of lockdown and also in any subsequent waves of infection with newer strains. Simulation and periodic stringent audits with the entire team would prove successful in rectifying errors and avoiding any possible contamination.

Accuracy and reliability of spinal navigation: An analysis of over 1000 pedicle screws.

PURPOSE: To estimate the rate of pedicle screw malpositioning associated with placing pedicle screws using intraoperative computed tomography (CT)-guided spinal navigation. METHODS: We analysed the records of 219 patients who underwent pedicle screw fixation using O-arm-based navigation. Screw placement accuracy was evaluated on intraoperative CT scans acquired after pedicle screw insertion. Breaches were graded according to the Gertzbein classification (grade 0-III). RESULTS: Of 1152 pedicle screws included, 47 had pedicle violations noted on intraoperative CT. Pedicle screw violation was noted for 17 of 241 screws placed in the cervical spine (overall breach rate, 7.05%; 3.73% and 3.3% with grade I and II, respectively), for 11 of 300 screws placed in the thoracic spine (overall breach rate, 3.67%; 2%, 1%, and 0.67% with grade I, II, and III, respectively), and for 22 of 611 screws placed in the lumbar spine (overall breach rate, 3.6%; 2.29% and 0.82% with grade I and II, respectively). The rate of accuracy of pedicle screw fixation was 93%, 96.33%, and 96.4% for the cervical, thoracic, and lumbar spine, respectively. CONCLUSIONS: Using O-arm-based intra-operative three-dimensional scans for navigation can improve the reliability, accuracy, and safety of pedicle screw placement, reducing the risk for reoperation and hospitalization due to implant-related complications. Further improvement may be achieved by adequate consideration of potential sources of errors.