Abstract】 Objective To explore and evaluate the specific application of computer-assisted surgery (CAS) in orthopedics. Methods Starting from the current application status, system composition, and working mode of CAS, we explored its specific application and development trend in various fields of orthopedics. The results were discussed from shallow to deep, and the advantages and disadvantages of CAS were summarized in a more systematic and comprehensive manner. Conclusion CAS will become an important tool in orthopedic surgery and a good technical method. Wang Weiguo, Department of Orthopaedic Trauma Surgery, Jinan General Hospital of Military Region
【Key words】 Computer-assisted; orthopedic surgery; stereotactic positioning technology
The rapid development of computer technology has promoted the development of medical imaging visualization technology. In order to make surgeons understand the relationship between the position of surgical instruments and patient anatomy at a glance, and make surgery more accurate, safe and convenient, people combine computer technology, virtual reality technology, medical imaging technology, image processing technology and robot technology with surgery, resulting in Computer assisted surgery (CAS) is a new comprehensive technology based on the ability of computers to process and control large amounts of data and information at high speed, and to support surgeons through a virtual surgical environment to make surgery safer and more accurate. Computer technology, spatial positioning technology, and other image 3D reconstruction and fusion enable surgeons to fully assess the patient’s condition before surgery, plan the surgical path and plan in detail, simulate surgery, track surgical instruments during surgery, guide surgery, and determine the scope of surgery, thus making surgery more precise, safe, and minimally invasive.
The specific application of CAS in orthopedic surgery is called computer assisted orthopedic surgery (CAOS), which combines the advanced equipment in today’s medical field: computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), digital vascular angiography (DSA), ultrasound imaging (US), and the use of a variety of other techniques. ), ultrasound imaging (US), and medical robotics (MR). CAOS provides orthopaedic surgeons with powerful tools and methods to improve surgical positioning accuracy, reduce surgical injuries, perform complex orthopaedic surgery, and increase surgical success. CAOS technology has been introduced in Europe and North America since the early 1990s, and although it has been used for a short period of time, it has developed very rapidly and is being used more and more widely. The application of CAOS in orthopedic surgery is described here.
1 CAOS application status
Although the development of medical imaging technologies (such as CT and MRI, which can display the three-dimensional structure of complex parts of the structure) has enabled physicians to make a more adequate and accurate assessment of the patient’s condition than before, these image features are not applicable during surgery, where the surgeon relies mainly on two-dimensional X-ray images and is at risk of exposure to radiation. The development of intraoperative 3D imaging systems is therefore necessary for some orthopaedic procedures. The emergence of surgical navigation provided an important clue to these problems, and its design principle was derived from global satellite positioning technology. Computer-assisted surgery (CAS) first originated as a stereotactic technique in neurosurgery, and spatial positioning techniques have gone through robotic positioning methods, optical positioning methods, and electromagnetic positioning methods that are not obscured by light. Due to the development of spatial positioning technology its equipment has less and less influence on the surgery, and gradually be used in spinal surgery. With the rapid development of medical imaging technology and computer technology, CAOS has undergone an initial period of CAOS systems based on preoperative CT-Based Image Guidance, which requires manual registration, intraoperative CT or X-ray Image Guidance, and intraoperative CT-Based Image Guidance. Guidanceor Fluoroscopy-Based Image Guidance) for automatic registration of CAOS systems, Three Dimen-sional C-Arm Fluoroscopy for navigation, and future CAOS systems will be automatic registration matching based on intraoperative real 3D images.
1.1 Components of the CAOS system
CAOS systems can be divided into hardware and software components. The hardware components of various navigation are roughly the same: including imaging devices, navigation and positioning tools, and computer workstations. The positioning tools of various navigation are also similar: including Dynamic Reference Base (DRB), Calibrationfixture, Transmitter, Receiver, etc. Software mainly refers to the computer operating procedures: including image processing, matching algorithms, tool registration, positioning, angle, distance measurement and other operating systems. The image processing involves 3D reconstruction, image segmentation, image fusion, etc. Software system is the core of CAOS technology. Currently, various CAOS products have incompatible software and different software packages are required for different procedures such as knee replacement, hip replacement and pedicle screw navigation. Therefore, the development of compatible software and hardware may be the future direction of CAOS development.
1.2 How CAOS works
Pre-operative image acquisition, i.e. image information of patient’s preoperative related X-ray, CT, MRI is input into the computer of CAOS system, which is processed by the software package for 3D construction. Based on the patient’s anatomical information the doctor can make pre-operative plan and simulate the surgery, determine the size of endosseous implant, the path of implantation, and the precise location. After entering the operating room a correction device is installed on the image intensifier of the C-arm, the video fiber optic cable of the C-arm is connected to the navigation, the transmitter is fixed on the patient, the transmitter is connected, and the receiver is connected to the navigation system. The distance between the C-arm and the patient’s surgical site is adjusted, the image information is obtained, the image is aligned, the tool is registered, the computer is computationally positioned, the instrument is tracked, the image is displayed, and the surgery is started after confirming that the position indicated by the tool is the same as the position on the navigation image. The specific operation differs from one navigation to another, but the general procedure is similar. The intraoperative navigation system tracks the surgical instruments and displays multidimensional images in real time to guide the procedure. Thanks to the introduction of CAOS, orthopedic surgeons can more perfectly solve surgeries with more obscure, obscure, and complex anatomy.
2 Application of CAOS in spine surgery
CAOS was first applied to pedicle screw technology, from the lumbar spine and lower thoracic spine applying pedicle screw fixation to the upper thoracic spine and cervical spine, and has been widely promoted and applied in scoliosis deformity correction, cervical lateral block screw technology, anterior internal fixation system of the spine and vertebral body resection, etc. The technology is becoming more and more mature. Because of the large anatomical variation and obvious individual differences in spinal deformity correction and spinal fracture surgery, the anatomical sign of pedicle screw implantation is not obvious, CAOS technology can minimize the incidence of improper screw position, so the application of CAOS system is more accurate and safe than the traditional screw implantation technology, the amount of intraoperative exposure to radiation of the surgeon and patient is significantly reduced, and the surgery is more minimally invasive.
2.1 Lumbar spine
The conventional lumbar pedicle screw technique has a high incidence of screw malpositioning, but Foley et al. applied the navigation technique to insert pedicle screws from T11 to S1 in 6 cadavers without a single case of cortical penetration. 150 screws were inserted in 30 patients in the lumbar spine by Kalfas et al.
2.2 Thoracic spine
Due to the presence of thoracic contour, the thoracic pedicle is small and the accuracy of pedicle screw placement is reduced by the influence of thoracic contour in intraoperative X-ray fluoroscopy. laboratory and clinical investigation studies have shown that the perforation rate of the pedicle in the thoracic spine using conventional techniques is 15.9% to 54.7%. merloz et al. reported that only 6.6% of screws were poorly positioned using CAOS in thoracic segmental scoliosis correction surgery.
2.3 Cervical spine
The anatomy of the cervical spine is complex, closely adjacent to the nerve and vertebral artery, and the vertebral artery is highly variable, requiring more precise and difficult surgery. Clinical studies have shown that the lower cervical lateral block screw fixation technique has a misplacement rate of 1 4% and 5% have significant symptoms of nerve root injury, while the application of the C A O S system has significantly improved the safety and accuracy of the procedure. 6% of specimens could not receive screw fixation when the CAOS system was applied by Bloch et al. to perform C1 to C2 lateral block screw fixation on 17 cadavers, and 23% of specimens could not receive screw fixation with conventional radiographic and anatomical markers. Welch et al. used navigation to perform transoral odontoidectomy and tumor resection with satisfactory results, and Kotani et al. reported that the perforation rate of cervical pedicle screw implantation with CAOS was significantly lower than that of the conventional surgical group, and the screw placement was more precise and ideal. With the development of the CAOS system cervical pedicle screw fixation will no longer be a technical challenge, but will be more precise and safe. In addition, the CAOS system has also been used in percutaneous lumbar pedicle screw fixation, spinal endoscopy, anterior cervical, thoracic, and lumbar vertebral body and tumor resection and decompression surgery, using special biting forceps that can be tracked by navigation, making vertebral body and tumor resection safer and reducing the risk of vascular nerve injury. the advantages of CAOS in pedicle screw surgery are obvious after nearly 10 years of clinical application. From the perspective of evidence-based medicine, the application of the CAOS system may become a gold standard for pedicle screw fixation surgery.
3 Application of CAOS technology in joint surgery
3.1 Total hip replacement
In a randomized controlled prospective study reported by Teenders et al, 150 total hip replacement patients were randomly divided into CAOS and conventional surgery groups. In addition, DiGioia et al. reported that the use of navigation for total hip replacement resulted in a 50% reduction in surgical incision and improved postoperative function due to proper placement of the acetabular prosthesis.
3.2 Knee replacement
It is important to restore the negative force line of the lower extremity in knee replacement surgery, and a postoperative joint inversion angle of less than ±3° has a significant impact on the long-term outcome of knee replacement. The accuracy of the lower extremity force line of knee replacement under CAOS system is higher than that of conventional surgery, which is important for the long-term knee function. The CAOS technique allows for standardization and consistency of surgery, thus making it possible to separate the various complex causes affecting the postoperative outcome of arthroplasty from the surgical causes, which is important for assessing the efficacy of arthroplasty surgery.
3.3 Arthroscopy and other aspects
Picard et al. performed a randomized controlled experimental analysis of the application of a navigation system (KneeNav-ACL system) in an in vitro simulation versus conventional arthroscopic reconstruction of the anterior cruciate ligament of the knee, and showed by measuring the distance between the ideal position point set preoperatively and the actual surgical bone hole that the navigation system was more accurate than conventional arthroscopic surgery, with a statistical difference between the two groups. In addition, Langlotz et al. applied CAOS to perform peri-acetabular osteotomy in the pelvis, which could make the surgery accurate to about 0.5 mm in an experimental study, and the clinical accuracy of surgical osteotomy could reach about 2 mm. CAOS helps doctors simulate osteotomy before surgery, calculate the amount of osteotomy and acetabular angle precisely, and display images instantly with tracking instruments during surgery, so that doctors can operate more precisely and avoid medical source injury It also helps to train doctors with less experience in peri-acetabular osteotomy.
4 Application of CAOS technology in traumatic orthopedics
The main problem facing the application of CAOS in traumatic orthopedics is to develop software about fracture repositioning and to monitor the fracture repositioning during surgery, because CAOS system is based on preoperative or intraoperative virtual image technology, intraoperative fracture repositioning, fracture block displacement, displacement of reference base, etc. can cause large errors in CAOS system, and the accuracy of guiding surgery is greatly reduced. Hufner et al. developed a new CAOS software system for internal fixation of pelvic ring fracture repositioning, and the differences between the two groups in the degree of residual misalignment and rotation angle were not statistically significant (averaging about 1 mm and 0.7°) when compared with fracture block repositioning under direct vision. Jacob et al. reported the clinical application of CAOS technique to assist sacroiliac screw implantation with satisfactory results; Slomczykowaki et al. reported the application of CAOS system for internal fixation of femur fracture with locking intramedullary nail, and all locking nails were locked in one time, and the operation time was shortened and the intraoperative exposure of radiation was significantly reduced. At present, CAOS system is a key development focus in fracture reduction and internal fixation surgery, and there is a great market demand, if there is a big breakthrough in fracture reduction software development, the application prospect is very attractive.
5 Problems and development trend of CAOS
The continuous improvement of CAOS system has strongly promoted the development of orthopedics: it has improved the accuracy of surgery and the credibility of instruments by tracking and displaying surgical instruments; it has prompted the development of surgical instruments in the direction of more precision; it can tailor the surgical plan for each specific patient; it has enabled the development of endoprosthesis in the direction of more precision and perfection; it has reduced the exposure of surgery and made the surgery more precise, safe and minimally invasive; CAOS The emergence of CAOS has also brought a whole new field to orthopedics, making the development of orthopedics more intelligent, minimally invasive and standardized. However, CAOS technology is still in its developmental stage, with high cost; tools are still quite primitive; bulky equipment; cumbersome operation; a learning period is required to master CAOS technology; preoperative image alignment may produce errors, intraoperative registration process may produce errors, dynamic reference ring may be displaced intraoperatively, navigation itself has its own accuracy, and operator’s own errors may occur, affecting its accuracy. Its cost and benefits need to be further evaluated; however, with the progress of science and technology, the CAOS system will be continuously improved and perfected, and its application in orthopedics will become more and more widespread.
In conclusion, CAS technology is a brand new field that will benefit the development of surgical techniques and make the surgical procedure more convenient and intuitive, but it is only an aid to diagnose and treat diseases and must work under strict and specialized monitoring by surgeons to correct errors, if any, in time without unnecessary results. The assisted surgery system not only replaces conventional complex surgery, reduces the amount of X-ray radiation for patients and medical personnel in conventional surgery, but also simplifies surgical operations, shortens surgery and anesthesia time, greatly reduces patients’ physical pain, shortens patients’ hospitalization time, reduces medical costs, and enables patients to return to society as soon as possible. Thus, it is more economical, safe, accurate and convenient than traditional surgery.
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