November 21, 2025 • 12 mins
Great Debate: Does the Hip-Spine Relationship Matter for Anterior Approach?
🎙️ Join Joe Schwab in this intriguing episode of the AHF Podcast, where Dr. Nathaniel Nelms and Dr. Edwin Su debate a hot topic in orthopedics: 'Does the hip-spine relationship really matter for the anterior approach?' With thoughtful arguments from both sides, this episode delves into the importance of biomechanics and surgical techniques to achieve stable, durable, and predictable hip replacements. Whether you're a surgeon or simply interested in the nuances of anterior hip surgery, this discussion will sharpen your thinking! 💬 📌 Tags: #AHFPodcast #GreatDebates #AnteriorHipFoundation
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Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Joseph M. Schwab (00:00):
Hi, this is Joe Schwab and if you recognize
my voice, it's probably becauseyou've heard another episode of
the AHF podcast, which meansyou're listening again, and I
can't tell you how much Iappreciate that.
And because you're listening,again, I want to ask you a
favor, if you could share thispodcast with a colleague or a
(00:24):
friend or somebody you thinkmight be interested in this type
of content.
Or better yet, leave us a reviewon your podcast platform or give
us five stars, or you could doall of those things.
We really appreciate it and ithelps us grow.
Anyway, thank you so much forbeing a listener and a
(00:44):
subscriber to the AHF podcast.
Now let's get on with the show.
(01:04):
Welcome to the AHF podcast.
I'm your host, Joe Schwab.
One of the reasons we host thesegreat debates is pretty simple.
Orthopedics moves forward whenthoughtful surgeons disagree
respectfully.
So much of what we do in theoperating room comes down to
judgment, often more judgmentthan maybe we'd like to admit,
(01:27):
and when the evidence isn'tdefinitive.
When two smart people can lookat the same set of data and
reach different conclusions,that's exactly the moment when
debate becomes valuable.
Today's topic is one that everyanterior hip surgeon has
wrestled with in one way oranother.
Does the hip spine relationshipreally matter for the anterior
(01:51):
approach?
Taking the pro position, we haveDr.
Nathaniel Nelms taking the conposition.
Dr.
Edwin Su.
What you're about to hear isn'tjust a clash of viewpoints.
It's a glimpse into howexperienced surgeons think, how
they weigh risk, and how theydecide what matters in the
pursuit of safer, more reliableoutcomes.
(02:14):
Let's get into it.
The next debate topic is:"Thehip spine relationship does not
matter for anterior approach".
Taking the pro position, Dr.
Nathaniel Nelms, taking the conposition, Dr.
Edwin Su.
Four minutes to you.
Dr.
Nelms.
Nathaniel Nelms (02:33):
Thank you very much.
I posit to you that this is themost important debate that you
guys are going to face.
In your practice at all?
I think that in everything wehear, we need to do more, more,
more.
You need technology, you needthe robot, but have you guys all
been made to feel guilty ifyou're not getting five extra
hip and then spine x-rays andthen all this extra technology?
(02:56):
But I ask, where is theevidence?
There is not one study that'spublished when it comes to
anterior total hip thatdemonstrates any advantage to
using the hip spine relationshipperiod.
End of debate right there.
So you do not need to havefunctional spine x-rays, a full
body EOS CT, save that for theposterior robotic total hip
(03:19):
patients.
First, let's come back to what'sthe problem.
All that the hip spinerelationship was ever designed
to deal with was dislocation.
And the problem came becausesurgeons that were doing their
patients in a lateral position.
And, um, we're havingdislocations despite using
navigation in robotics.
Why was that?
It was because they were puttingthe cup in a position relative
to the pelvis, but not thinkingabout the functional position,
(03:41):
which we can get just by layingthe patient's supine and doing
an anterior hip.
The pelvic tilt is alreadyaccounted for when you use
fluoroscopy and put the cup inan appropriate position.
You're already taking intoaccount those differences in
pelvic position.
So when it comes to evidence, isthere, uh, any evidence?
The hip spine relationship isimportant.
Absolutely it works in theposterior approach.
(04:02):
For the anterior hip, there iszero.
Vigdorchik one of the foundersof this principle.
He applied this to a large groupof patients.
He found he was able to bringhis dislocation rate down to
0.8%.
That's still higher than mostseries with the anterior
approach.
And to do that, he had to useeight dual mobility.
In 8% of his cases.
Do we use dual mobility?
8% of our cases.
We don't need to.
It's an unneeded expense.
(04:23):
There was a study in JOA in2024, looked at 180 anterior
versus 180 posterior approachesall two Bs.
The worst hip spineclassification, there was 0.6%
dislocation in the anterapproach.
That's about the same as in thestudies that aren't using it,
and 2.7% in the posteriorapproach still not as good.
So why does approach matter?
It's because we're able to laythe patient's supine, but also
(04:43):
we're able to disrupt thetissues less.
You can keep your obturatorexternus intact.
You can keep your posteriorcapsule intact, maybe repair
your anterior capsule.
Your stated goal could be wrongin making these corrections.
You could actually make theproblem worse.
You could, IM measurementerrors.
It doesn't always take intoaccount hip flexion contracture.
Think about that.
And femoral anteversion is oftennot even considered in the whole
thing of, am I gonna adjust mycomposition?
(05:04):
When you look at what'srecommended in hip spine
classification, if you put yourcups at 40 degrees and 25
degrees of anteversion, you'regonna hit all of them, your one
a's your two as.
Two, two B's.
Two, two a's all of those areincluded.
So the difference you're gonnamake is maybe five degrees in
composition is always changing.
Just the anteversion, you'rereally not making any difference
at all.
So what does matter?
(05:24):
Do an anterior approach.
Minimize soft tissue releases,recreate your leg length and
offset.
Stop worrying about this littletiny change of cup position that
you can't actually make.
Even with the robot, you mightbe hitting the wrong target.
I yield my time.
Edwin Su (05:37):
Nathan, Nathan.
Nathan.
Uh, boy.
Am I gonna school you?
Uh, this is my first, uh,invitation here and, uh, I feel
like I just got invited to aspecial club.
So thank you to the organizers.
Uh, so I, I, I, um, I'm gonnastart this debate with a survey.
So, how many of you are usingfluoroscopy for your DA total
(05:57):
hip replacements?
Show of hands, please.
93 people.
Okay.
How many of you are positioningyour cup based on the standing
pelvic position?
Show of hands.
Okay.
Not as many as I thoughtactually.
Uh, so, um, well, I would arguethat if you are trying to
position your cup at the time ofsurgery to the standing pelvic
(06:21):
position, then you are alreadytaking into account the hip and
spine position.
And the mechanics and how itaffects your, uh, cup stability,
your hip stability.
So you said that there were noholds barred for this debate.
I tried to look up all dirt onNathan.
Uh, he runs a pretty clean ship.
I didn't see any, uh, evidenceon social media, so fortunately
(06:44):
didn't have anything.
Uh, but that may be because he'sbeen living under a rock and he
hasn't seen in the last fiveyears about a hundred pa papers
written about the hip and spinerelationship.
I wish I could believe yourmagical thinking, that DA
approach could make ourdislocations disappear.
But we can't overcome the lawsof physics.
(07:04):
We are making an incision.
We are gonna disrupt the softtissues more in the anterior
than the posterior granted.
And I think you'll all do abeautiful job, and that's why
we're here talking about the DAapproach.
But our dislocation rate willnot be zero.
The the ball that we insert issmaller.
We have the soft tissuecompromise and the hip spine
mechanics will influence wherethe pelvis is in space.
(07:26):
And we have to take that intoaccount when we position our
cup.
The two situations where that'simportant are in the stiff spine
and in pelvic tilting this willoccur because the pelvis is a
bridge between the hip joint andthe spine.
So Nathan, the hip bone isconnected to the pelvis bone,
which is connected to the spinebone, and that is why we need to
(07:47):
take this into account.
Okay?
He's given some eloquent, uh,arguments that you don't need to
take that to into accountbecause our soft tissue envelope
is good.
Um, but I would submit to youeven in those papers that show
there, there is a reduced riskof dislocation with the DA
approach.
It is not zero.
And you all are surgeons herewho are interested in education,
(08:09):
learning from others, and doingthe best for our patients except
for Ben Domb, who just came herefor the social events.
But, uh, I would submit to youif you are interested in that.
Then you must take into accountthe hip and spine relationship.
So from a practical standpoint,you don't need to get 14
studies, you just need torealize that the spine does
(08:29):
influence the pelvis.
And basically the two situationsthat I'm concerned about that
keep me up at night are thestuck standing position where
the pelvis does not roll back inthe sitting position and then
you're at risk for posteriordislocation.
And I will give you that.
The DA approach, I thinkmitigates.
That to a large degree.
So most of the time you don'treally have to worry about that
(08:50):
stuck standing position.
It's the stuck sitting positionthat you really have to worry
about when you look at thatstanding pelvis, and it looks
like an ob, an outlet view, theyare basically posteriorly tilted
and they're gonna be at risk foranterior instability, and those
are the ones that you have to becareful about.
Minimize your cup position andeven minimize your anteversion
(09:10):
on the cup and consider dualmobility.
So, um, in conclusion, Nathan, Ithink if you wanna do the best
for your patient, you need torealize that the hip spine
mechanics are a risk factor fordislocation.
You recognize risk factors forother conditions and you don't
ignore them.
Why ignore the hip and spinerelationship?
Joseph M. Schwab (09:29):
One minute rebuttal.
Nathaniel Nelms (09:31):
Wow.
Um, I don't believe any of that.
Let's start with that.
Um, I think maybe what we shouldall do is do hip resurfacings.
Like you, I'm sure you use allthe hip spine classification for
every one of your hipresurfacing patients you take
care of.
I just question, you know, Ijust go back to my points of,
um.
You know, can we keep it simple?
(09:52):
Your goal is maybe to get it to0% dislocation.
Is that reasonable?
Is that possible?
There are some patients who havesoft tissue abnormalities,
they're hyper lax.
Some of the recommendations fromthe, uh, hip spine
classification are go dualmobility.
Well, if, if you have to go dualmobility, can you really get an
optimal composition that's gonnaget you to 0% dislocation?
(10:13):
So maybe we could get closer to0% if we just put, dual mobility
in all of our patients.
But we're not gonna get there.
Even doing that.
There are weird things thathappen.
We all absolutely want to do ourbest, right?
Do it.
But this isn't gonna get usthere.
Edwin Su (10:26):
I think it'll, I think it'll get us closer, Nathan.
So if we recognize that in that,in that, uh, situation where the
spine effects the pelvis, we canmodify certain things, just
little tweaks and try to get itas close to zero as possible.
I think we're on the same page,but I think you should take into
account the hip spine mechanics.
Joseph M. Schwab (10:44):
All right.
Thank you.
Thank you, debaters.
Please go to your app.
Vote for who won.
At the end of the day, whetheryou lean towards Nathan's call
for simplicity or Edwin'semphasis on biomechanics,
there's one point they bothagree on.
Our goal is the same.
We're all trying to givepatients the most stable,
(11:05):
durable, and predictable hipreplacement possible.
Some of us approach that byreducing variables.
Others approach it by trying tomeasure and account for them.
And the truth is bothphilosophies have merit
depending on the patient infront of you.
Hip spine mechanics won't matterfor everyone and they won't
matter in every case, but theydo matter when they matter.
(11:29):
And part of being a thoughtfulsurgeon might be knowing when
that moment is.
If today's debate helped yousharpen your thinking or
reconsider your assumptions.
Then it accomplished exactlywhat these conversations are
meant to do.
Thank you for joining me forthis episode of the AHF Podcast.
As always, please take a momentto like and subscribe so we can
(11:51):
keep the lights on and keepsharing great content just like
this.
Please also drop any topic ideasor feedback in the comments
below.
You can find the AHF podcast onApple Podcasts, Spotify, or in
any of your favorite podcastapps.
As well as in video form onYouTube slash at Anterior Hip
(12:13):
Foundation, all one word.
Episodes of the AHF Podcast comeout on Fridays.
I'm your host, Joe Schwab,asking you to keep those hips
and spines happy and healthy.
Hi, this is Joe Schwab and if you recognize
my voice, it's probably becauseyou've heard another episode of
the AHF podcast, which meansyou're listening again, and I
can't tell you how much Iappreciate that.
And because you're listening,again, I want to ask you a
favor, if you could share thispodcast with a colleague or a
(00:24):
friend or somebody you thinkmight be interested in this type
of content.
Or better yet, leave us a reviewon your podcast platform or give
us five stars, or you could doall of those things.
We really appreciate it and ithelps us grow.
Anyway, thank you so much forbeing a listener and a
(00:44):
subscriber to the AHF podcast.
Now let's get on with the show.
(01:04):
Welcome to the AHF podcast.
I'm your host, Joe Schwab.
One of the reasons we host thesegreat debates is pretty simple.
Orthopedics moves forward whenthoughtful surgeons disagree
respectfully.
So much of what we do in theoperating room comes down to
judgment, often more judgmentthan maybe we'd like to admit,
(01:27):
and when the evidence isn'tdefinitive.
When two smart people can lookat the same set of data and
reach different conclusions,that's exactly the moment when
debate becomes valuable.
Today's topic is one that everyanterior hip surgeon has
wrestled with in one way oranother.
Does the hip spine relationshipreally matter for the anterior
(01:51):
approach?
Taking the pro position, we haveDr.
Nathaniel Nelms taking the conposition.
Dr.
Edwin Su.
What you're about to hear isn'tjust a clash of viewpoints.
It's a glimpse into howexperienced surgeons think, how
they weigh risk, and how theydecide what matters in the
pursuit of safer, more reliableoutcomes.
(02:14):
Let's get into it.
The next debate topic is:"Thehip spine relationship does not
matter for anterior approach".
Taking the pro position, Dr.
Nathaniel Nelms, taking the conposition, Dr.
Edwin Su.
Four minutes to you.
Dr.
Nelms.
Nathaniel Nelms (02:33):
Thank you very much.
I posit to you that this is themost important debate that you
guys are going to face.
In your practice at all?
I think that in everything wehear, we need to do more, more,
more.
You need technology, you needthe robot, but have you guys all
been made to feel guilty ifyou're not getting five extra
hip and then spine x-rays andthen all this extra technology?
(02:56):
But I ask, where is theevidence?
There is not one study that'spublished when it comes to
anterior total hip thatdemonstrates any advantage to
using the hip spine relationshipperiod.
End of debate right there.
So you do not need to havefunctional spine x-rays, a full
body EOS CT, save that for theposterior robotic total hip
(03:19):
patients.
First, let's come back to what'sthe problem.
All that the hip spinerelationship was ever designed
to deal with was dislocation.
And the problem came becausesurgeons that were doing their
patients in a lateral position.
And, um, we're havingdislocations despite using
navigation in robotics.
Why was that?
It was because they were puttingthe cup in a position relative
to the pelvis, but not thinkingabout the functional position,
(03:41):
which we can get just by layingthe patient's supine and doing
an anterior hip.
The pelvic tilt is alreadyaccounted for when you use
fluoroscopy and put the cup inan appropriate position.
You're already taking intoaccount those differences in
pelvic position.
So when it comes to evidence, isthere, uh, any evidence?
The hip spine relationship isimportant.
Absolutely it works in theposterior approach.
(04:02):
For the anterior hip, there iszero.
Vigdorchik one of the foundersof this principle.
He applied this to a large groupof patients.
He found he was able to bringhis dislocation rate down to
0.8%.
That's still higher than mostseries with the anterior
approach.
And to do that, he had to useeight dual mobility.
In 8% of his cases.
Do we use dual mobility?
8% of our cases.
We don't need to.
It's an unneeded expense.
(04:23):
There was a study in JOA in2024, looked at 180 anterior
versus 180 posterior approachesall two Bs.
The worst hip spineclassification, there was 0.6%
dislocation in the anterapproach.
That's about the same as in thestudies that aren't using it,
and 2.7% in the posteriorapproach still not as good.
So why does approach matter?
It's because we're able to laythe patient's supine, but also
(04:43):
we're able to disrupt thetissues less.
You can keep your obturatorexternus intact.
You can keep your posteriorcapsule intact, maybe repair
your anterior capsule.
Your stated goal could be wrongin making these corrections.
You could actually make theproblem worse.
You could, IM measurementerrors.
It doesn't always take intoaccount hip flexion contracture.
Think about that.
And femoral anteversion is oftennot even considered in the whole
thing of, am I gonna adjust mycomposition?
(05:04):
When you look at what'srecommended in hip spine
classification, if you put yourcups at 40 degrees and 25
degrees of anteversion, you'regonna hit all of them, your one
a's your two as.
Two, two B's.
Two, two a's all of those areincluded.
So the difference you're gonnamake is maybe five degrees in
composition is always changing.
Just the anteversion, you'rereally not making any difference
at all.
So what does matter?
(05:24):
Do an anterior approach.
Minimize soft tissue releases,recreate your leg length and
offset.
Stop worrying about this littletiny change of cup position that
you can't actually make.
Even with the robot, you mightbe hitting the wrong target.
I yield my time.
Edwin Su (05:37):
Nathan, Nathan.
Nathan.
Uh, boy.
Am I gonna school you?
Uh, this is my first, uh,invitation here and, uh, I feel
like I just got invited to aspecial club.
So thank you to the organizers.
Uh, so I, I, I, um, I'm gonnastart this debate with a survey.
So, how many of you are usingfluoroscopy for your DA total
(05:57):
hip replacements?
Show of hands, please.
93 people.
Okay.
How many of you are positioningyour cup based on the standing
pelvic position?
Show of hands.
Okay.
Not as many as I thoughtactually.
Uh, so, um, well, I would arguethat if you are trying to
position your cup at the time ofsurgery to the standing pelvic
(06:21):
position, then you are alreadytaking into account the hip and
spine position.
And the mechanics and how itaffects your, uh, cup stability,
your hip stability.
So you said that there were noholds barred for this debate.
I tried to look up all dirt onNathan.
Uh, he runs a pretty clean ship.
I didn't see any, uh, evidenceon social media, so fortunately
(06:44):
didn't have anything.
Uh, but that may be because he'sbeen living under a rock and he
hasn't seen in the last fiveyears about a hundred pa papers
written about the hip and spinerelationship.
I wish I could believe yourmagical thinking, that DA
approach could make ourdislocations disappear.
But we can't overcome the lawsof physics.
(07:04):
We are making an incision.
We are gonna disrupt the softtissues more in the anterior
than the posterior granted.
And I think you'll all do abeautiful job, and that's why
we're here talking about the DAapproach.
But our dislocation rate willnot be zero.
The the ball that we insert issmaller.
We have the soft tissuecompromise and the hip spine
mechanics will influence wherethe pelvis is in space.
(07:26):
And we have to take that intoaccount when we position our
cup.
The two situations where that'simportant are in the stiff spine
and in pelvic tilting this willoccur because the pelvis is a
bridge between the hip joint andthe spine.
So Nathan, the hip bone isconnected to the pelvis bone,
which is connected to the spinebone, and that is why we need to
(07:47):
take this into account.
Okay?
He's given some eloquent, uh,arguments that you don't need to
take that to into accountbecause our soft tissue envelope
is good.
Um, but I would submit to youeven in those papers that show
there, there is a reduced riskof dislocation with the DA
approach.
It is not zero.
And you all are surgeons herewho are interested in education,
(08:09):
learning from others, and doingthe best for our patients except
for Ben Domb, who just came herefor the social events.
But, uh, I would submit to youif you are interested in that.
Then you must take into accountthe hip and spine relationship.
So from a practical standpoint,you don't need to get 14
studies, you just need torealize that the spine does
(08:29):
influence the pelvis.
And basically the two situationsthat I'm concerned about that
keep me up at night are thestuck standing position where
the pelvis does not roll back inthe sitting position and then
you're at risk for posteriordislocation.
And I will give you that.
The DA approach, I thinkmitigates.
That to a large degree.
So most of the time you don'treally have to worry about that
(08:50):
stuck standing position.
It's the stuck sitting positionthat you really have to worry
about when you look at thatstanding pelvis, and it looks
like an ob, an outlet view, theyare basically posteriorly tilted
and they're gonna be at risk foranterior instability, and those
are the ones that you have to becareful about.
Minimize your cup position andeven minimize your anteversion
(09:10):
on the cup and consider dualmobility.
So, um, in conclusion, Nathan, Ithink if you wanna do the best
for your patient, you need torealize that the hip spine
mechanics are a risk factor fordislocation.
You recognize risk factors forother conditions and you don't
ignore them.
Why ignore the hip and spinerelationship?
Joseph M. Schwab (09:29):
One minute rebuttal.
Nathaniel Nelms (09:31):
Wow.
Um, I don't believe any of that.
Let's start with that.
Um, I think maybe what we shouldall do is do hip resurfacings.
Like you, I'm sure you use allthe hip spine classification for
every one of your hipresurfacing patients you take
care of.
I just question, you know, Ijust go back to my points of,
um.
You know, can we keep it simple?
(09:52):
Your goal is maybe to get it to0% dislocation.
Is that reasonable?
Is that possible?
There are some patients who havesoft tissue abnormalities,
they're hyper lax.
Some of the recommendations fromthe, uh, hip spine
classification are go dualmobility.
Well, if, if you have to go dualmobility, can you really get an
optimal composition that's gonnaget you to 0% dislocation?
(10:13):
So maybe we could get closer to0% if we just put, dual mobility
in all of our patients.
But we're not gonna get there.
Even doing that.
There are weird things thathappen.
We all absolutely want to do ourbest, right?
Do it.
But this isn't gonna get usthere.
Edwin Su (10:26):
I think it'll, I think it'll get us closer, Nathan.
So if we recognize that in that,in that, uh, situation where the
spine effects the pelvis, we canmodify certain things, just
little tweaks and try to get itas close to zero as possible.
I think we're on the same page,but I think you should take into
account the hip spine mechanics.
Joseph M. Schwab (10:44):
All right.
Thank you.
Thank you, debaters.
Please go to your app.
Vote for who won.
At the end of the day, whetheryou lean towards Nathan's call
for simplicity or Edwin'semphasis on biomechanics,
there's one point they bothagree on.
Our goal is the same.
We're all trying to givepatients the most stable,
(11:05):
durable, and predictable hipreplacement possible.
Some of us approach that byreducing variables.
Others approach it by trying tomeasure and account for them.
And the truth is bothphilosophies have merit
depending on the patient infront of you.
Hip spine mechanics won't matterfor everyone and they won't
matter in every case, but theydo matter when they matter.
(11:29):
And part of being a thoughtfulsurgeon might be knowing when
that moment is.
If today's debate helped yousharpen your thinking or
reconsider your assumptions.
Then it accomplished exactlywhat these conversations are
meant to do.
Thank you for joining me forthis episode of the AHF Podcast.
As always, please take a momentto like and subscribe so we can
(11:51):
keep the lights on and keepsharing great content just like
this.
Please also drop any topic ideasor feedback in the comments
below.
You can find the AHF podcast onApple Podcasts, Spotify, or in
any of your favorite podcastapps.
As well as in video form onYouTube slash at Anterior Hip
(12:13):
Foundation, all one word.
Episodes of the AHF Podcast comeout on Fridays.
I'm your host, Joe Schwab,asking you to keep those hips
and spines happy and healthy.
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