Robotic Hip Replacement
For a straightforward hip, a robot does not make your result better. It places the parts inside the target range more often, but that has not been shown to mean less pain, better walking, or a hip that lasts longer.
The robot decides nothing. It carries out a plan built from your scan and from points the surgeon touches onto your bone, so a wrong input becomes a wrong result delivered very precisely. I use it for hips where the landmarks are missing or hard to read. This page covers what it costs you, when it helps, and what to ask.
What the machine does during a hip replacement
In most systems you have a computed tomography scan beforehand. Software builds a three-dimensional model of your pelvis and femur, and a plan is made on it: shell size, position, angle, stem, neck length.
In the operating room, trackers are pinned to your pelvis and femur so the system knows where they are in space. The surgeon then touches a probe onto a series of specific points on the bone, which is called registration. That step ties the plan on the screen to the patient on the table.
From then on the system tracks the tools, showing the angle in real time as the socket is reamed and reporting leg length and offset once trial components are in.
On the hip, most systems do not cut anything themselves. They guide and they measure.
The six steps of a hip replacement carried out with robotic assistance. Look at how many of the steps are measurement rather than cutting. Illustration prepared for this page.
| Step | What the machine does | What I do |
|---|---|---|
| The plan | Builds a three-dimensional model from your scan and proposes sizes and angles | Review it, change it, and decide what is actually used |
| Registration | Records the points it is given | Choose and touch every point, and judge whether they are right |
| The socket | Shows the angle and depth live, and on most systems holds the reamer inside a set boundary | Ream the bone, and look at the rim and at the surface I have cut |
| The thigh bone | On most systems, measures only | Open the canal and shape it by hand with a rasp |
| Leg length | Reports numbers once the trial parts are in | Compare both legs by hand and decide |
| A disagreement | Reports nothing, because it cannot detect its own error | Decide which to believe, and find out why the screen is wrong |
Who does what during a hip replacement carried out with robotic assistance.
The half of the operation the robot does not do
On the hip, the socket is the part a robot guides. The thigh bone is not in most cases. I open the canal and shape it by hand with a rasp, and I judge by feel and by sound when the rasp has stopped moving in the bone that will hold it.
The rasp used to shape the canal of the thigh bone during hip replacement. Look at the teeth running down its length, because the shape they cut is set by hand and not by a machine. Complete Orthopedics illustration.
The stem that goes in afterwards is a wedge. It does not sit where a screen puts it. It sits where the canal I have shaped allows it to sit, and the surface I have cut is what it grips.
The tapered wedge stem that sits in the canal the rasp has shaped. Look at how the stem narrows towards the bottom, because that taper is what wedges it into bone the surgeon has prepared.
Some systems will measure the femur as well, and report what the trial parts are doing to leg length and offset. Measuring is not the same as preparing. On most hips, worldwide, the stem is still put in by hand.
Registration is where this quietly goes wrong- “Garbage in- Garbage out!”
This is the part that never appears in the advertising and it is the part patients should understand.
Every number the system produces afterwards depends on registration having been accurate. If the probe was placed slightly off, or a tracker pin shifted, or the pelvis moved in its supports after registration, every subsequent reading is wrong by that amount and it does not announce itself. The screen still shows a confident number.
Why registration decides every number the system reports afterwards. Look at the two readouts, which are identical even though only one socket is where it was planned. Illustration prepared for this page.
So I treat the readout as a second opinion rather than the answer. I look at the rim of the socket. I look at the reamed surface, and at whether the reamer has moved from soft grey bone into firm bleeding bone. I look at where the neck cut sits relative to the lesser trochanter. And I compare both legs by hand. If the screen and my eyes disagree, I follow my eyes and find out why the screen is wrong.
What the scan and the pins cost you
A planning computed tomography scan, which is more radiation than the plain films I would otherwise order, and an extra appointment.
Additional time in the operating room for setup and registration, particularly early in a surgeon’s experience. Operative time is not free: longer open time carries a higher infection risk, and that is a documented relationship rather than an opinion.
Two extra small incisions for the tracker pins. Pin sites can become infected and, less commonly, a fracture can occur through a pin site, which is a complication that simply does not exist in a conventional operation.
.And cost, which lands mostly on the hospital and the health system, and is a large part of why it is marketed so hard. I am also conscious that a machine represents a large purchase for a hospital, and that hospitals which have bought one have an interest in it being used.
| What is added to your operation | What that means for you |
|---|---|
| A planning computed tomography scan | An extra appointment, and more radiation than the plain films I would otherwise order |
| Setup and registration time | Longer with the wound open, and longer open time carries a higher infection risk |
| Two extra small incisions for tracker pins | Pin sites can become infected, and rarely a bone can crack through one |
| Cost | Falls mostly on the hospital and the health system, which is a large part of why it is marketed so hard |
What robotic assistance adds to a hip replacement.
The hips where I do reach for it
Hips where the normal landmarks are missing or misleading. I do it for patients who ask for it!
Preoperative x-ray of the pelvis showing an anteroposterior view of both hips, from the case published as Robotic Left Hip Total Replacement in sequel of Developmental Dysplasia of the Hip. Look at the shape of the socket before surgery, because that is why the landmarks are unreliable in this hip.
Postoperative x-ray of the left hip showing the shell, the head and the stem in place, from the case published as Robotic Left Hip Total Replacement Sequel Developmental Dysplasia Hip. Look at how the stem is seated in the canal, because that part was shaped by hand. One of my own films, anonymised, with hidden file information stripped out.
Preoperative x-ray showing an anteroposterior view of the left hip, from the case published as Robotic Total Hip Replacement in a 48-year-old male with sequel of Developmental Dysplasia of the Hip.
Preoperative x-ray of the pelvis showing an anteroposterior view of both hips, from the case published as Management of Right Hip Arthritis with Robotic Total Hip Replacement.
Preoperative x-ray showing an anteroposterior view of the left hip, from the case published as Robotic Left Total Hip Replacement in a 71-year-old Female.
Preoperative x-ray of the left hip, from the case published as Robotic Left Hip Total Replacement for Arthritis secondary to Avascular Necrosis of the Hip.
My robotic hip cases, written up individually
Every robotic hip I have published is listed here with its own films, so the indications can be read rather than taken on trust.
- Management of Right Hip Arthritis with Robotic Total Hip Replacement
- Robotic Left Hip Total Replacement for Arthritis secondary to Avascular Necrosis of the Hip
- Robotic Left Hip Total Replacement in sequel of Developmental Dysplasia of the Hip
- Robotic Left Total Hip Replacement in a 71-year-old Female
- Robotic Right Hip Total Replacement in a 75-year-old male
- Robotic Total Hip Replacement in a 48-year-old male with sequel of Developmental Dysplasia of the Hip
What robotic hip replacement has not been shown to change
I want to give the honest position rather than a convenient one.
Robotic assistance does place components inside a target range more consistently. That finding is real and repeatable and I am not disputing it.
What has not been demonstrated is that the average patient having a routine hip replacement walks better, hurts less at a year, or keeps the implant longer because a robot was used.
Literature tells patients that this technology can improve the x-ray after surgery, but that it has not translated into better joint function or a longer lasting implant, and that a great deal of it is marketed directly to patients. That matches what I see.
| The question a patient actually asks | Where the evidence stands |
|---|---|
| Does it put the socket in the target range more often? | Yes. Shown repeatedly, and I do not dispute it. |
| Does it restore the centre of the hip closer to the plan? | Yes, by a small amount. |
| Does it reduce pain or improve walking at a year? | Not shown. The scores come out the same. |
| Does it make dislocation less likely? | Not shown. |
| Does it make the implant last longer? | Not shown. |
| Does the operation take longer? | Yes. |
| Is it better in a socket deformed by childhood hip disease? | Placement is closer to the plan. The measured gain in hip score is far below what a patient can feel. |
Table 3. What robotic hip replacement has and has not been shown to do.
Even in the hips I do use it for, the honest number is small. When robotic hip replacement has been compared with the conventional operation in sockets deformed by childhood hip disease, the centre of the hip was restored closer to plan, and the hip score at follow up was higher. The gain is real. It is not something you would notice.
A hip replacement planned properly off the films, reamed under direct vision, referenced to the patient’s own transverse acetabular ligament rather than an average angle, and tested through a full range of movement before anything is committed is already a very accurate operation. The room for a machine to improve on that in a straightforward case is smaller than the advertising implies.
Postoperative x-ray of the pelvis after a right hip replacement carried out with robotic assistance, with the parts labelled. Look at the position of the shell and the seating of the stem, because the film cannot show you whether that came from a machine or from a surgeon looking carefully.
What to ask if a robot is offered to you
These are the four questions I would ask if I were sitting on the other side of the desk.
| Ask this | A good answer sounds like this |
|---|---|
| Do you use it in every case, and if so what does it add in the simple ones? | Here is where it adds something, and here is where it does not |
| What were your own results before you had it? | A number, from their own practice. If a surgeon cannot tell you, the comparison being implied is with nobody in particular |
| What happens if the system fails partway through my operation? | We finish conventionally, without hesitation |
| Am I being charged more for this? | A direct answer, either way. You are entitled to know |
Four questions worth asking before you agree to a robotic hip replacement.
The rule I apply to every new machine
I do not put a new device into a patient because it is new. I wait for the noise to subside and for reports from people who had no hand in developing it.
That has occasionally made me late. It has also meant my patients were not the ones being learned on. Every hip surgeon of my generation has watched a technology arrive with confident claims and leave embarrassed.
None of that is an argument against robotics. It is an argument for using it where it does something I cannot do as well by hand, and not using it as a reason for you to choose me.
Common questions about robotic hip replacement
Does the robot perform my hip replacement?
No. The surgeon performs it. On the hip, most systems do not cut anything on their own. They hold a plan, guide the tool that shapes the socket, and report numbers. Every decision, and the whole of the thigh bone side, is done by the surgeon.
Is a robotic hip replacement more accurate?
The socket lands inside the target range more often. That has been shown many times and I do not dispute it. How accurately the parts were placed and how you feel a year later are two different questions, and the second one has not been answered in favour of the robot.
Will I recover faster after a robotic hip replacement?
There is no good evidence that you will. Studies that measure pain, walking and hip scores at six months and a year find the same results with and without it.
Does a robot make dislocation less likely?
Not that has been shown. Pooled studies comparing robotic and conventional hip replacement have found no difference in dislocation.
Does a robotic hip replacement take longer?
Usually yes, by a modest amount, mostly for setup and registration. That matters, because longer time with the wound open carries a higher infection risk.
Do I need a scan before a robotic hip replacement?
For most systems, yes: a planning computed tomography scan. That is an extra appointment and more radiation than the plain x-rays I would otherwise order. Some newer systems work instead from a single x-ray taken during the operation, or from no scan at all.
What risks exist only because a robot was used?
Small pins hold markers on your bone, through their own small cuts. Those pin sites can become infected, and rarely a bone can crack through one. Neither risk exists in a hip replacement done without a robot.
Will I be charged more for a robotic hip replacement?
Most of the cost falls on the hospital rather than on you. You are still entitled to ask, and you should ask before the day of surgery rather than after it.
Should I choose a surgeon because they use a robot?
No. Ask what their own results are and how many hips they do. A machine in the room tells you what the hospital bought. It does not tell you who is holding the instruments.
What happens if the system fails during my operation?
The operation is finished conventionally. Any surgeon offering this to you should be able to say that without hesitating.
Which hips is it genuinely useful for?
Hips where measurement is genuinely hard. A socket deformed by childhood hip disease. A hip that has been operated on before. A case where I am concerned about how much bone there is to work with. A leg length that will be difficult to judge until late in the operation.
Who pays for robotic surgery, and who pays me
I receive nothing from the manufacturer of any robotic platform, and I hold no interest in any of them. Robotic surgery is marketed to patients directly, so a plain statement about who pays me belongs on this page.
Case Studies:
- Coming Soon
Robotic Hip Replacement FAQ’s
- Can you use any implant with the robot?
- Why do all hospitals not have the robotic system?
- Is the surgery faster with a robot?
Are you a good candidate for Robotic Hip Replacement?
Robotic hip replacements can be a good option for many men and women, but they’re not for everyone. If you have been experiencing hip pain, or have had a prior hip surgery, you may need a complete hip replacement.
To schedule your evaluation, call (516) 735-4032 or use our online contact form to learn more.
