Three words that get used interchangeably and should not be.
Joint replacement planning technology is marketed under several names, and patients arrive having been told their surgery will be "robotic" without anyone explaining what that means. The distinctions are worth ten minutes.
- Navigation. Tracking markers let a computer show the surgeon, in real time, exactly where the instruments and the bone are in space. It measures; it does not hold anything.
- Patient-matched instrumentation. A CT or MRI of your own joint is used to manufacture cutting guides that fit your bone and no one else's. The plan is built into the physical instrument before you are in theatre. Medacta's MyKnee works this way, and Professor Rodda's practice is an international reference centre for it.
- Robotic assistance. The plan is built digitally, and a robotic arm then constrains the instruments to that plan during the operation, stopping them from going outside it.
All three answer one question: how do you execute a plan built from this patient's anatomy, rather than an average one? They differ in where the plan lives, not in what it is for. Kinematic alignment is the philosophy behind what the plan should say; these are the means of delivering it.
In the knee.
The knee is where this technology has had the most attention, because the knee is less forgiving than the hip. A knee replacement has to be aligned and the soft tissues balanced through a full range of movement, and small errors in either are felt by the patient.
Planning from your own imaging allows the position of each implant to be decided against your anatomy before any bone is cut, and the knee to be taken through its range virtually to check the balance. See robotic knee replacement for the knee in detail and what the robotic evidence actually shows for the honest position on outcomes.
In the hip.
Less discussed and, for some patients, more useful. The questions in a hip replacement are different: where the cup sits, how the leg length ends up, and how the components are oriented relative to your pelvis, which is not in the same position when you stand as when you lie on the table.
Getting cup position right matters because it influences stability and bearing wear, and getting leg length right matters because a difference the patient can feel is one of the more common causes of dissatisfaction after an otherwise technically sound hip replacement. See leg length difference.
The direct anterior approach also allows intra-operative imaging with the patient positioned as they would stand, which is a different route to the same accuracy.
What the evidence supports, and where it stops.
Computer-assisted techniques are consistently more accurate at putting an implant where the surgeon intended. That much is well established and not seriously disputed.
What has not been established is that the accuracy translates into patients feeling better or implants lasting longer. Those are different claims and they need long-term registry follow-up that does not yet exist in sufficient volume.1 The technology is a reasonable, evidence-supported way to execute a plan. It is not a different operation and it does not make an unsuitable candidate suitable.
What it does not do.
- It does not perform the operation. The surgeon does.
- It does not decide what the plan should be. That is judgement, and it is where the difference between surgeons actually lies.
- It does not fix a bad indication. An operation that should not have been done is not improved by being executed precisely.
- It does not remove the risks, which are set out for the hip and the knee.
Questions worth asking at your consultation.
- Which planning technology are you using for my operation, and why that one?
- What does it change about how my operation is performed?
- Does it add cost for me, and is that in my written estimate?
- What does it not do?
Frequently asked questions.
Does a robot perform the surgery?
No, and the name is the most misleading thing about it. The surgeon plans the operation, makes every decision and performs the operation. The system holds the instruments to the plan and stops them going outside it. Nothing operates on its own and nothing happens without the surgeon.
What is the difference between robotic surgery and patient-matched instruments?
They solve the same problem two ways. Patient-matched instrumentation uses a CT or MRI of your own joint to manufacture guides that fit only your bone, so the plan is built into the physical instruments before theatre. A robotic or navigated system builds the plan digitally and holds the surgeon to it during the operation. Both aim at executing a plan made from your anatomy rather than an average one.
Is computer-assisted surgery better?
It is measurably more accurate at putting the implant where the surgeon intended. Whether that accuracy translates into you feeling better, or into the implant lasting longer, is the honest open question: registry follow-up is not yet long enough to answer it. Anyone claiming it is settled has gone past the evidence.
Is it available for both hip and knee?
Yes. The technology and the terminology differ between the two joints, and the planning question is different: in the hip it is mostly about component position and leg length, and in the knee it is mostly about alignment and soft tissue balance.
Does it cost more?
The technology has a cost, and where that falls depends on the hospital and your health fund rather than on this practice. Your written estimate covers your actual position before anything is booked.
Does it take longer?
Setup adds time at the start. In experienced hands the total theatre time is broadly comparable, and time under anaesthetic is one of the things a surgeon is actively managing rather than trading away.
References.
- Australian Orthopaedic Association National Joint Replacement Registry. Hip, Knee & Shoulder Arthroplasty Annual Report. Adelaide: AOA.
This page provides general information about a medical condition and a surgical procedure. It is not individual medical advice and does not replace consultation with a qualified practitioner. Outcomes vary between individuals and all surgery carries risk. A referral is needed for a consultation with Professor Daevyd Rodda; without one, you can start with the practice nurse practitioner, who can provide it.