Patient Specific Instrument Knee Replacement:

Patient specific instrument Knee Replacement (PSI) is a new technology tool in knee replacement surgery used to ensure accurate positioning of the knee implant. Using advanced 3D image scanning and high grade medical 3D printing,  individualised “patient-specific instruments” are designed and custom printed for each patient’s knee surgery. These bespoke personalised instruments fit precisely to an individual knee.


Accurate alignment and positioning of the prosthesis in knee replacement surgery is important for the success of the operation. Traditionally, surgeon use a variety of mechanical tools to align the knee joint and to prepare the bone surfaces of the knee for the prosthesis. However, subtle malalignment of the prosthesis may result which could potentially compromise the results of the surgery. 

More recently,  new technologies have been developed with the aim to improve the accuracy and reproducibility of total knee replacement and partial knee replacement surgery.  These include use of 3D virtual modelling, utilisation of patient specific instruments (PSI) to assist with accurate and reproducible implant positioning and the use of robotic assisted surgical techniques.


How does the technology work?

A 3D CT scan is performed to map the anatomy of your knee joint. These CT images are then uploaded to orthopaedic biomedical engineers in Switzerland, where sophisticated computer modelling software is used to produce a virtual 3D model of your knee.  The knee replacement surgery can then be virtually simulated to calculate the best size and fit of the implant to achieve good range of motion, stability and function of the prosthesis. 

A 3D model of your knee is then 3D printed on a state-of-the-art high quality 3D printer.  Mr Freedman carefully analyses these models and in collaboration with the engineers is able to effectively pre plan your surgery.  Single-use patient specific surgical instruments specific for your knee are then 3D printed, sterilised and and couriered to Australia.  These custom-fit instruments fit precisely to your knee and facilitate reliable and accurate positioning of the knee replacement implants in your surgery.  This allows for efficient, accurate, reproducible and less invasive surgery.


Utilisation of this sophisticated technology does not add any cost to you knee replacement operation in Australia as the implant manufacturer covers the cost of producing the customised instruments for your surgery. This is fantastic for Australian patients as the technology is otherwise expensive overseas, where patients in many other countries are required to cover the cost of the scans and patient-specific instruments. 

Frequently Asked Questions (FAQ) regarding Patient Specific (PSI) Knee Replacement:

1.   Where is the implant made?

The implants that Mr Freedman choses to use for all his knee replacement procedures is Swiss made. The 3D-printed patient-specific instruments are also made in Switzerland.   There are other implant companies who manufacture implants in the USA and some in China however Mr Freedman does not use those

2.  Is there any added cost in having this technology used for my knee replacement?
No, not in Australia.
Overseas 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.

3. How much does it cost to have knee replacement surgery?

Mr Freedman sets his fees well below the recommended fee schedule (i.e below AMA recommended fees) to try to improve accessibility for patients.  Your fees will depend on the level of your insurance policy and the complexity of your surgery. A written quote will be provided after your consultation.

4. Is patient specific (PSI) knee replacement and robotic knee replacement the same thing?

No. PSI and robotics are both new technologies in knee replacement but work in different ways. In robotic knee replacement a large intraoperative robot is used in the surgery to assist with implant positioning.  In PSI knee replacement the surgery has been pre-planned with virtual simulation and then executed with 3D printed custom instruments,

5.  Do you see any disadvantages with patient specific knee replacement technology?
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.

6.  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.

7. I have read of both CT and MRI PSI systems? Which does Mr Freedman prefer?
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 as 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).

8. Will a torniquet be required during patient specific knee replacement surgery?
No. An uninflated, 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. The torniquet may be inflated for a few minutes just at the time when the prosthesis is being secured onto the bone 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.

9. Which hospital is this surgery available at?

This technology is available at all of the hospitals where Mr Freedman operates.

10. How is patient specific knee less invasive than other techniques?

In traditional knee replacement, large rods are passed up inside the bones (intramedullary rods) to calculate the angles of the joint. In computer navigated and robotic knee replacement, pins are drilled into the bones to communicate leg position to the computer or robot.  In contrast, in  PSI knee replacement there is no rod and no pins as the custom printed guide is individually produced for each surgery and fits precisely to each individual knee.


Disclaimer: Any surgical or invasive procedure carries risks. Before proceeding, you should consider seeking a second opinion from an appropriately qualified health practitioner.