Patient Specific Instrument (PSI) Knee Replacement:
Patient specific instrument (PSI) Knee Replacement is an exciting new technology in orthopaedic and knee replacement surgery. This technology utilises advanced 3-D scanning and 3-D printing to produce a mould of the patient’s knee and then uses 3-D printing to create personalised “patient-specific instruments” to guide the surgery.
This technology thereby assists the orthopaedic surgeon in trying to achieve accurate preparation of the patient’s anatomy and accurate positioning of the knee implant.
The PSI technology works as follows:
Prior to the surgery date, a CT scan is performed to map the anatomy of your knee joint. These CT images are then transmitted electronically to a team of orthopaedic biomedical engineers in Switzerland. In Switzerland, sophisticated computer remodelling software is used to first produce a virtual 3D model of your knee.
Then, state-of-the-art 3D printing technology is used to print a 3-D model of your knee. Mr Freedman carefully analyses these models and then, in discussion with the engineers, is able to pre plan your surgery. The 3D imaging an modelling allow accurate calculation of the bone preparation required for your knee replacement.
Single-use patient specific surgical instruments specific for your knee are then 3-D printed, sterilised and and couriered to Mr Freedman in Australia. The customised instruments facilitate reliable and accurate positioning of the knee replacement implants in your surgery.
Your surgery is then performed using these custom-built instruments rather than generic manual alignment tools as traditionally used.
In Mr Freedman’s experience, this allows for efficient, accurate, reproducible and less invasive surgery (no rods need to be placed up inside the bone as is used for traditional surgery and no extra pins are placed into the bones as would be required for computer navigated surgery).
Utilisation of this sophisticated technology does not add any cost to you knee replacement operation in Australia as the CT scan is bulk-billed and the implant manufacturer covers the cost of producing the customised instruments for use in your surgery.
This is fantastic for Australian patients as the technology is otherwise expensive and patients in many other countries need to cover the cost of the scans and patient-specific instruments.
Mr Freedman has extensive experience with the patient-specific knee platform and now utilises it for the majority of his knee replacement procedures.
In the past, the orthopaedic literature reported that a subset of patients were not completely satisfied with the result of knee replacement surgery.
It is now thought by many surgeons that subtle malalignment of the prosthesis may account for this. Mr Freedman is consequently an advocate for technologies that may improve the accuracy and reproducibility of knee replacement surgery.
In Mr Freedman’s experience, CT-based 3-D printed patient-specific instruments are a useful tool to try to achieve accurate and reproducible implant positioning.
Frequently Asked Questions (FAQ) regarding Patient Specific (PSI) Knee Replacement:
1 Q: Is there any cost in having this technology used for my knee replacement?
A: In Australia, No.
The technology itself is expensive overseas – a high definition scan is performed, sent to expert engineers overseas who need to spend considerable time analysing the images, single use instruments need to be be made via 3D printing, sterilised and then couriered back to Australia but all this is FREE for Australian patients.
Fortunately, the implants are sufficiently reimbursed by the private health funds in Australia that the implant manufacturer is able to include this technology without additional cost to the patient. Overseas, patients have to pay to have access to this new technology.
2. Q: Do you see any disadvantages with patient specific knee replacement technology?
A: A minor inconvenience is that it does take approximately 3-4 weeks for the patient-specific instruments to be manufactured in Switzerland and then delivered to Australia. Patients therefore need to wait a few weeks from their consultation until surgery.
This is usually not much of an issue as patients usually need some time to get themselves ready for surgery anyway, but this technology is therefore generally not used for urgent cases such as fracture care. If you require surgery urgently Mr Freedman will perform your surgery through a more traditional (but still very reliable) technique.
3. Why don’t all surgeons utilise this patient specific knee replacement technology?
There are several very accepted methods available to perform knee replacement surgery and surgeons will generally use whatever method or system they are most familiar with, how they were trained, and where are able to achieve good results.
The traditional methods for knee replacement involve using either manual instruments or computer navigation. PSI instrumentation is relatively new and is not offered by all orthopaedic implant manufacturers and many surgeons are not familiar with the technology or do not feel that they need to use it. In Mr Freedman’s experience, PSI technology is not a substitute for good surgical technique and but rather is simply a useful intraoperative tool which he finds allows him to achieve the most reliable results for his patients.
4. I have read of both CT and MRI PSI systems? Which does Mr Freedman prefer?
A: Mr Freedman prefers the CT-bases system. In his experience, the quality and and nature of a patient’s cartilage can change in a short period of time and therefore MRI systems which rely on cartilage and soft tissue mapping may not be accurate. CT-based systems which rely on bone mapping are more consistent. As a secondary bonus, CT scans are much less expensive (and in fact bulk-billed for Mr Freedman’s patients).
5. Q: Will a torniquet be required during patient specific knee replacement surgery?
A: A loose fitting tourniquet is placed on the upper thigh prior to surgery but it not utilised for most of the operation. By leaving the tourniquet uninflated, a major cause of knee discomfort after knee replacement is avoided. For a brief period during surgery when the prosthesis is secured the torniquet may be inflated for a few minutes but then is quickly let down again. Mr Freedman’s technique is different to many surgeons who leave the torniquet inflated for the entire length of the procedure.