State-of-the-art navigation technology for stronger and longer-lasting replacement joints
Whether because of accident, ageing or natural deformity, there comes a time in a lot of people's lives when they start to experience impaired mobility in one or other of their key joints, such as the knees or hips, or perhaps their back or pelvis.
Fortunately, modern medical science offers the possibility of correcting such faults with orthopaedic surgery. Replacement hips and knees effectively restore ease of movement and alleviate pain. Spinal implants do a similar job for the back.
But up until relatively recently there has still been an element of hit and miss in these critical procedures. Working in such small spaces with restricted visibility challenges the expertise and experience of even the most highly-trained surgeons. Fine tuning the prosthetic knees and hips and corrective implants into precise position and alignment is no easy task. In practice, an alignment of 90%-95% accuracy for manual orthopaedic operations is accepted as being good A skewing of 3-5 degrees is taken as acceptable. However, in at least 10% of cases the skewing is greater and is classified as a malalignment.
The long-term impact of this is that the prosthetics wear more quickly. About 10 years is accepted as the typical lifespan for a successful orthopaedic surgery. After that, the problems that prompted the surgery in the first place start to once again regain full mobility and ease of life.
A near-perfect fit with CAOS
Now, thanks to state-of-the-art, computer-guided navigation technology, the clinical outcomes of total knee replacement, total hip replacement and spinal surgery and abnormality correction procedures are achieving new levels of performance.
The key advancement is Computer Assisted Orthopaedic Surgery (CAOS) which has two main themes of development, robotic systems and navigation systems. Navigation was originally developed for brain surgery. CAOS enables the surgeon to achieve virtually 100% alignment. As a result, prosthetics and implants can last as long as your original bones and joints. Perhaps longer.
This most advanced available joint replacement system, CAOS uniquely provides surgeons with high-precision preoperative, intraoperative and postoperative assessments of the patient's joint kinematics or movement.
CAOS enables the surgeon to perform more accurate and less invasive surgical techniques, resulting in less pain and faster rehabilitation. The technology is primarily used for operations on the spine, knees, hips and trauma areas, for example fractures. It is especially useful in pelvic surgery that may be necessary after car or motorcycle accidents as the area is difficult to see into otherwise.
"Utilization of the navigation system allows more accurate positioning of the components," summarised Assist. Prof. Dr. Sombat Rojviroj , a Medical Director of the Orthopedics Center at Bangkok Hospital Medical Center, one of the hospitals at the forefront of practicing computer-assisted orthopaedic surgery in Asia, "and that results in better functioning and longer lasting joint replacements."
The fundamental paradigm of the system is as follows:
• Patient-specific preoperative registration and planning through creation of three-dimensional (3D) virtual environments using medical imagery
• Intraoperative registration of the virtual environment (which includes the surgical model and the surgical plan) to the actual patient and the interventional system
• Computer-assisted execution of the plan
The main components of the system include an infrared camera, a computer and special instruments with reference array.
The first stage of the procedure is registration not hospital registration but computer registration. Essentially, the computer constructs a model of the operative area on the basis of two x-rays, so minimising the patient's exposure to radiation. The registration can be done using an imageless technique by using reference anatomical bony landmarks, its deformities and its axis.
"Registration is the most important step of the operation because the whole outcome of the surgery depends on its clarity and accuracy," says Dr.Sombat. "It is a precise and accurate tool which provides us with a comprehensive understanding of the patient's anatomy before any bone cuts are made," he added.
During the actual operation, the computerised navigation system creates a 3D image of the operating area of the patient which is viewed throughout the procedure, eliminating educated guess work.
"It acts like a brain that gives you 3D pictures," says Dr.Sombat.
Once all the correct information in available, the orthopaedic surgeon can start to make highly precise bone cuts so that the prosthetic can slot in near perfectly.
The robotic system assists the surgeon to do the surgery. It holds the instruments as the surgeon manipulates them robotically. But the navigation system stands by the surgon, connecting to the reference array and a special probe keeps the computer abreast of changes during the operation.
"We can say suppose we cut the bone this way or insert the prosthesis here, the navigation system will tell us whether it is appropriate or not."
Precision where it counts
"Say we are placing a screw into an area of the spine to correct a fracture or deformity, the navigation system tells us the precise position and angle of insertion that is optimal. For the sake of strength and durability, obviously the larger the screw the better. The navigator tells us precisely how large we can go. If it is too short or too thin, the screw won't be as strong as it could be. If it is too long or wide, it might damage a neighbourting organ or nerves. And if it goes in at even a slightly incorrect incorrect angle, it will not only be weaker but may cause damage."
When you are correcting spinal fractures or degenerative conditions such as spondylosis, you need the optimum point of entry and this technology enables you to do that. The proper placement of spinal instrument fixations reduces surgical risk and complications and increases stability. The longevity of prosthesis or spinal fixation depends on accuracy of the surgical technique and this technique has by far the best outcome.
"With the navigator's assistance we can do operations with far greater confidence," said Dr.Sombat " Alignment is close to 100% every time and that means the prosthetic works better and lasts longer."
The system is also safer. In fact, Orthopaedic surgeons are used to creating 3D images from 2D images such as plain x-rays films, CD scans or MI images, for surgical planning. 2D and 3D images from real-time fluoroscopy are also available intre-operatively but carry an increased risk of rediation exposure. By contrast, the navigation hazards. It is also precise and reproducible so you can make copies for subsequent use without having to x-ray again.
"Think of it like a global positioning device that lets the surgeon know exactly where he is and how to proceed at every stage of the operation," Dr.Sombat concludes. "When you go through a big operation like this, you don't want to have to come back a few years later and do it again. CAOS means you don't have to."
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