When patients hear that FT3D knee resurfacing does not require a CT scan, the first question is almost always the same: how does the robot know what to do?
It is a reasonable question. Most people have seen or heard of robotic knee surgery that begins with a CT scan — a detailed pre-operative image of the joint that the robot uses as its map. The idea of a robotic procedure without that pre-built map seems counterintuitive.
This article explains exactly how FT3D works without a CT scan, why that is actually an advantage rather than a limitation, and what the patient experience looks like when there is no pre-operative imaging step.
What a CT Scan Is Actually Used For in Conventional Robotic Surgery
In CT-based robotic systems like MAKO (Stryker), the CT scan serves one purpose: to build a three-dimensional model of the patient’s knee before surgery. That model is then loaded into the robot’s planning software, and on the day of surgery, the robotic arm uses the pre-built model as its reference for guiding bone cuts and implant positioning.
The assumption is that the model from the CT scan accurately represents the knee that will be operated on. In most cases, this is roughly true. But there is an important gap: the CT is taken weeks before surgery, usually with the patient standing or positioned in a scanner. The surgery happens with the patient lying flat, under general anaesthesia, with muscles fully relaxed. These are meaningfully different states for the same joint.
How FT3D Maps the Knee Without a CT
FT3D takes a completely different approach. Instead of building a model before the operation, it builds the model during the operation.
Here is how the intraoperative mapping works, step by step:
- The patient is positioned on the operating table and the knee is exposed through a standard surgical approach.
- The surgeon uses a calibrated probe to touch specific anatomical landmarks on the bone surfaces — the femur and tibia. This takes approximately 5 to 8 minutes.
- The system builds a live 3D model from these probe readings, combined with real-time positional tracking sensors attached to the bones. The result is a three-dimensional map of the knee exactly as it exists at that moment — with the actual soft tissue tension, bone geometry, and joint mechanics captured under surgical conditions.
- The surgeon plans the resurfacing on screen in real time, using the intraoperative model to determine the precise position, size, and orientation of the implant.
- The robotic system guides bone removal to sub-millimetre accuracy based on the intraoperative plan.
The entire mapping process adds a small amount of time to the procedure — but it is time spent capturing data that is more accurate and more current than any pre-operative CT scan could provide.
Why Intraoperative Mapping Is More Accurate Than a Pre-Operative CT
There are three reasons why the FT3D approach produces a more accurate picture of the knee than CT-based planning:
1. It Captures the Knee in Its Surgical State
When a patient is under general anaesthesia and lying on an operating table, their muscles are fully relaxed. The soft tissue tension around the knee is different from what it was when the CT scan was taken. The joint position changes. The natural sag of a relaxed limb alters the geometry slightly. FT3D captures the knee exactly as the surgeon is working on it — not as it appeared in a scanner weeks earlier.
2. It Eliminates the Time Gap Problem
Between a pre-operative CT and the surgery date, joints change. Inflammation fluctuates. Fluid levels in the joint vary. For patients with significant arthritis, the joint space on surgery day may look meaningfully different from the joint space on scan day. FT3D has no time gap — the map and the surgery happen simultaneously.
3. It Directly Measures Soft Tissue Tension
One of the most important variables in knee surgery is how the soft tissues behave under load. CT scans image bone well but provide limited information about soft tissue mechanics. FT3D incorporates real-time soft tissue tension readings into its model, allowing the surgeon to account for ligament behaviour and natural knee mechanics directly in the surgical plan.
What This Means for Patients: No CT, No Radiation, Less Hassle
For patients, the practical implication of FT3D’s approach is straightforward: the pre-surgery process is simpler, faster, and completely radiation-free.
With CT-based robotic systems, the typical pathway is:
- CT scan appointment (separate visit)
- Pre-operative planning session (review CT model with surgeon)
- Surgery
With FT3D, the pathway is:
- Consultation with X-ray and clinical examination
- Surgery
No CT appointment. No radiation exposure. No additional visit. The assessment needed to determine if you are a candidate for FT3D resurfacing can be completed with a standard X-ray and a clinical examination of the knee — both done in a single consultation.
Is FT3D Safe Without a CT Scan?
Yes. The FT3D system’s intraoperative mapping has been validated across thousands of procedures. The real-time bone registration achieves sub-millimetre accuracy — equal to or better than CT-based planning systems in clinical use.
Dr TS Gill, the only surgeon performing FT3D in North India, was involved in the clinical development of the technique. The absence of a CT scan is not a simplification — it is the result of a deliberate design decision to achieve better accuracy through intraoperative data rather than pre-operative approximation.
Who Is a Candidate for FT3D Knee Resurfacing?
FT3D resurfacing is most appropriate for patients with:
- Knee arthritis limited to one or two compartments (medial, lateral, or patellofemoral)
- Significant knee pain that has not responded adequately to non-surgical treatment
- Intact ligaments and reasonable bone quality
- A desire to preserve as much of the natural knee as possible
It is also a strong option for younger and more active patients who may face the prospect of implant revision if total replacement is done too early in life.
Suitability is determined through a single consultation with Dr TS Gill, including an X-ray and clinical examination. If FT3D resurfacing is appropriate for your knee, you can typically proceed to scheduling surgery from that first visit.
→ Complete guide to RoboLens FT3D Knee Resurfacing
→ Book a Consultation with Dr TS Gill
Frequently Asked Questions
Why doesn’t FT3D need a CT scan?
FT3D uses intraoperative mapping — it builds its 3D model of the knee during surgery using a probe-based registration system. This real-time mapping is more accurate than a pre-operative CT scan because it captures the knee in its actual surgical state, not a pre-operative approximation.
Is a robotic knee procedure without CT safe?
Yes. The FT3D intraoperative mapping system achieves sub-millimetre accuracy and has been validated across clinical practice. The absence of CT is a feature, not a limitation — it eliminates radiation and produces more accurate data about the knee under surgical conditions.
What imaging is needed for FT3D?
A standard X-ray is sufficient for the pre-operative assessment. No CT scan is required at any stage. The detailed 3D map is created by the FT3D system itself during the operation.
How long does the intraoperative mapping take?
The probe-based registration process typically takes 5 to 8 minutes at the start of the surgical procedure. This is the only additional step compared to conventional knee surgery — and the accuracy it produces is significantly greater than relying on a pre-operative CT model.
