Imagine facing a persistent infection after shoulder
replacement surgery. Well, it's a surgeon's nightmare,
isn't it? And a patient's ongoing struggle. Absolutely.
But one treatment approach, this two -stage revision
with antibiotic spacers, it's shown really remarkable
success rates. I mean, as high as 95 % in getting
that infection under control. That's right. The
control rates can be very good. Yet, as often
happens in complex surgery, getting rid of the
infection, that's really only part of the story.
Does it restore function? What are the costs?
The complications? Exactly. Function is key.
And that's what this deep dive is all about,
unpacking that complexity. Welcome to the deep
dive, the show where we take your sources, the
latest research papers, essential articles, even
your own detailed notes, and extract the most
important nuggets of knowledge or insight. Think
of it as your shortcut to being truly well informed
on a critical topic. Today, we're diving deep
into a significant research paper focusing on
treating infected shoulder prostheses using precisely
that two -stage revision approach. And who better
to guide us through this material than one of
the authors of the paper itself? We're joined
today by Professor Mo Imam, an orthopedic expert
with an extensive publication record. He brings,
well, unparalleled insight directly from the
source. It's brilliant to have you here. Thank
you. It's a pleasure to be here and discuss the
work. Great. Let's jump straight in then with
a rapid -fire setup to frame our conversation.
First question. Shoulder periprosthetic joint
infection, PJI. Why is this particular type of
infection often considered, well, more challenging
to treat than PJIs in, say, the knee or hip?
Yes, that's a critical starting point. Shoulder
PJI, it really does present some unique difficulties.
A major factor is the microbiology. So alongside
more common organisms like coagulus negative
staphylococci, we frequently encounter propionobacterium
agnes. or P. acnes, as it's often called now,
cutie -bacterium axes. Now, while it's often
less virulent than, say, Staphylococcus aureus,
which you see more often in knee and hip PJIs,
P. acnes can be notoriously subtle in its presentation.
Sometimes pain is the primary or even the only
symptom. The only symptom. That must make diagnosis
quite elusive. It does. You can't always rely
on those classic signs of infection. And then,
both P. acnes and other organisms, they readily
form biofilms on the implant surface. This protective
layer, it sort of shields the bacteria from antibiotics,
making them incredibly persistent, difficult
to eradicate without surgery, and crucially,
local antibiotic delivery. Subtle presentation
and stubborn biofilms understood. Okay, second
rapid question. The paper focuses on a two -stage
revision using antibiotic spacers. In brief,
what does that process actually entail? Well,
it's essentially a sequence. It's designed to
eradicate the infection before re -implanting
a new prosthesis. So stage one involves removing
the infected implant completely, meticulously
cleaning out all the infected tissue that's the
debridement, and then inserting a temporary cement
spacer. A spacer. Yes, and the spacer acts as
a local depot. It eludes high concentrations
of antibiotics directly into the infected site.
And of course, systemic antibiotics are given
as well. And stage two. What happens then? Stage
two is performed once we believe the infection
is cleared and the patient has completed their
course of antibiotics. It involves removing that
temporary spacer and then implanting a new definitive
prosthesis. The goal really is to put a sterile
implant into what is now hopefully a sterile
environment. Two distinct stages then aimed at
clearing the infection first. Right. Final rapid
-fire question. What was the single most important
finding from this specific research regarding
the control of the infection itself? I'd say
the headline result from this particular series
is the high rate of infection control we achieved
with this two -stage approach. We saw successful
eradication in 36 out of the 38 patients available
for the final analysis. 36 out of 38, which translates
to an impressive 95 percent success rate based
on the defined criteria we use. Ninety five percent
infection control. That's a really powerful statistic.
But how do you get there and what's the full
picture beyond just eradicating the bug? Let's
dive deeper into the process, the challenges
and importantly, the patient outcomes in this
core segment. Let's do that. So diving deeper
into that challenge you mentioned earlier, the
source material makes it quite clear that shoulder
PGI is Well, it's feared by surgeons. It is,
yes. You highlighted the common organisms found
in this study. Coagulase negative, Staphylococci,
that was 42%, and P. acnes at 33%. That's correct.
And that point about P. acnes being less virulent,
but often causing only pain for clinicians listening,
that sounds like a crucial diagnostic trap to
avoid, doesn't it? Absolutely. It really is.
You simply cannot wait for the typical signs
of sepsis or acute inflammation sometimes. Persistent,
unexplained pain in a prosthetic shoulder. must
raise suspicion for a low -grade infection, particularly
P. acnes. And then, as we discussed, the biofilm
protects these bacteria, making surgical intervention
almost always necessary for eradication. You
can't just rely on antibiotics alone, usually.
And the two -stage strategy is built specifically
to address that biofilm and the persistent infection.
Tell us a bit more about stage one as it was
actually performed in the study. You removed
the prosthesis, did the debridement, and implanted
that handmade cement spacer loaded with gentamicin
and vancomycin. What was the post -operative
antibiotic regimen like? OK, so the protocol
involved two weeks of intravenous antibiotic
therapy initially. This was often adjusted based
on the culture results once the specific organism
was identified. Kalared therapy. Yes. And this
IV course was followed by a pretty substantial
course of oral antibiotics, typically lasting
for 10 weeks. So the combination approach local
delivery from the spacer and a prolonged systemic
course. Ten weeks oral after two weeks four.
That's quite a commitment for the patient. It
is indeed. Compliance is obviously key. Then
stage two, the re -implantation. The paper notes
that reverse total shoulder arthroplasty, or
TSA, was the default for most patients. 26 cases,
I think? That's right, 26. But hemiathroplasty,
HA, was used as a sort of salvage option for
severe glenoid bone loss in a smaller number,
eight cases. All right. And quite significantly,
14 patients didn't actually proceed to stage
two at all. They retained the spacer permanently.
Why was that? Well, the decision for the definitive
implant, or indeed whether to implant one at
all, was dictated by several factors. Things
like the extent of bone loss, particularly on
the glenoid side, which can be severely compromised
after infection, and the spacer implantation
itself. Right, the socket side. Exactly. And
also the patient's overall medical fitness or
sometimes their willingness or lack thereof for
further major surgery. RTSA generally offers
better function in many scenarios, but it simply
isn't possible without adequate bone stock to
support it. HA and retaining the spacer were
fallback options for the most difficult situations
or less fit patients. Essentially, yes. HA for
severe bone loss where RTSA wasn't feasible.
And retaining the spacer for those unable or
unwilling to undergo the second stage. And the
study population itself, 48 patients treated
initially, 38 available for analysis at a minimum
of 24 months follow -up. It's mentioned that
40 of the 48 were referrals from elsewhere for
PJI treatment. That tells us something, doesn't
it? These were likely already complex established
infections. Indeed. That's a very important point.
These were challenging cases, often patients
who had undergone previous surgeries. They weren't
typically primary PJIs presenting early and otherwise
healthy patients. They were often tertiary referrals.
Which makes the 95 % infection control rate perhaps
even more impressive. Well, it certainly highlights
the effectiveness of the approach in a difficult
cohort. How did you rigorously define and confirm
infection control in this study? What was the
diagnostic process involved? OK, so infection
control was defined by the absence of the recognized
musculoskeletal infection society. the MSIS criteria
for PGI at the final follow -up point. The standard
criteria. Yes. And the diagnosis itself relied
heavily on careful microbiological workup during
the surgeries. This involved taking multiple
tissue samples. We stipulated a minimum of three
and culturing them on different media, both anaerobic
and aerobic, and crucially incubating them for
at least 10 days. Ah, the 10 -day incubation
period again. That seems like a really vital
nugget of information for anyone in a lab or
clinic dealing with suspected shoulder PGI, doesn't
it? Especially for P. acnes. It is absolutely
critical. We can't stress that enough. Shorter
incubation times, say the standard five or seven
days, risk missing these low -growing organisms
like P. acnes. And if you miss it. If you don't
identify the pathogen, you can't target the antibiotic
therapy effectively. It compromises your chances
of eradication. So yes, extended culture time
is non -negotiable for a thorough diagnosis in
this specific setting. Makes perfect sense. And
as you mentioned, despite all these careful steps,
the headline result was 95 % infection control
in 36 out of 38 patients analyzed. Remarkable
success for such a difficult problem. What happened
in the two cases where control wasn't ultimately
achieved? Yes, it's important to look at the
failures too. In one case, it was a persistent
P. acnes infection after the re -implantation
stage. This was in an older patient with a history
of steroid use, which can be a risk factor. The
other failure was a persistent coagulase negative
staphylococcus infection, also after re -implantation.
In both instances, the patients experienced ongoing
pain, but unfortunately declined further surgical
intervention. Right, and that's another factor,
isn't it, in managing these complex cases, patient
choice, and their tolerance for surgical risk,
especially after multiple procedures? Precisely.
High success rate, but not absolutely guaranteed,
and patient factors certainly play a significant
role in the final outcome. Okay, so infection
control is paramount, and the results look good
there. But functional recovery is often the patient's
main priority, isn't it? How did the study actually
measure how well patients' shoulders were working
and feeling after all this treatment? We use
standard validated scoring systems, primarily
the constant Murley score and also the relative
constant score, which adjusts for age and gender,
making comparisons a bit fairer. We also use
the subjective shoulder value SSV, where the
patient rates their shoulder function themselves
on a percentage scale from 0 to 100. And of course,
the pain score, which is part of the constant
assessment. And when were these measured? These
were measured before the first stage, so baseline
pretreatment, and then again at the latest follow
-up point. That was either after the second stage
re -implantation or, for those who didn't have
a second stage, after the spacer implantation
when follow -up concluded. Right. Looking at
all patients treated with spacers, regardless
of the final step, what did the overall group's
functional outcome show? Was there improvement?
Yes. For the entire cohort treated with the spacer
protocol. So lumping everyone together initially,
there was this statistically significant improvement
in the overall constant scores, the relative
constant scores, the subjective shoulder value,
and importantly in their pain scores compared
to their pre -treatment levels. So as a group,
the treatment did improve symptoms and function
overall. Correct. On average, patients felt better
and functioned better than before the treatment
started. Okay, overall improvement is good news.
But this is where, as you say, the devil is often
in the detail. What did the functional outcomes
look like when you broke them down by the type
of final treatment? So comparing the RTSA group
versus the hemi -arthroplasty group versus those
who just retained the spacer. This is where it
gets really interesting, I think. Indeed it is.
This is where we saw quite marked differences.
Patients who completed the full stage process
and received a reverse total shoulder arthroplasty,
the RTSA, in the second stage showed a significant
functional improvement. Their mean constant scores
increased notably, from about 31 pre -op to 51
post -op. A definite jump there. Yes. However,
those patients who received a hemiarthroplasty
in the second stage, and also those who permanently
retained the cement spacer, did not show statistically
significant improvement in their constant and
Murley scores. No significant improvement in
those two groups. That's right. For the HA group,
the mean score went from about 22 to 24, basically
unchanged. For the spacer group, it went from
18 up to 35, which sounds like an increase, but
the p -value was 0 .093, so it didn't meet the
threshold for statistical significance in our
analysis. Wow. That functional disparity between
the RTSA group and the others is really quite
stark. Does this finding mean that RTSA is inherently
functionally superior for these PGI cases? Or
perhaps that HA, or just retaining the spacer,
are simply poor options for function after infection?
That's a really crucial point of interpretation,
and one the authors, including myself, discussed
at length. The functional difference wasn't necessarily
simply due to the type of implant itself. The
significant factor was almost certainly the baseline
condition of the patient and their shoulder.
Patients who ended up receiving an HA typically
had severe glenoid bone loss, as we discussed.
That necessitated using it as a salvage option.
Their potential for functional recovery was already
limited from the very start, regardless of the
implant. Because the foundation wasn't there.
Precisely. Similarly, patients who retained the
spacer often did so because of significant medical
comorbidities or being deemed unfit or inoperable
for a second stage. Again, this selects for a
group with lower baseline functional potential
and perhaps lower demands. I see. So the key
takeaway here isn't necessarily that RTSA causes
better function in PJI, but more likely that
the patients who were actually eligible for an
RTSA in stage two were already a different, perhaps
healthier cohort with better underlying bone
stock to begin with. Exactly that. Their better
starting point allowed for greater functional
recovery potential. The patient's initial condition
seems to be the major predictor of the functional
gain you can achieve, particularly in those most
compromised cases where options are limited.
That makes a lot of sense. It's about the patient
factors as much as, or maybe even more than,
the hardware choice in the end stage for these
really complex cases. It highlights the critical
importance of patient selection, managing expectations
realistically based on their initial condition,
the state of their bone, particularly the glenoid,
and their overall health. Now, the paper also
highlights complications. This is complex, high
-risk surgery. We know that. What was the complication
rate actually like in this series? Well, unfortunately,
and perhaps unsurprisingly, given the nature
of the problem, complications were common. They
occurred in 58 % of the patients in this study
cohort. 58 %? That's more than half. It is. It
really underscores the inherent difficulty and
the significant morbidity associated with treating
established shoulder PGI. This high rate also
led to a substantial number of patients requiring
further revision surgery down the line. 35 %
overall needed more operations. Wow, 58 % complication
rate and 35 % needing further revision. That's
substantial. What were the most frequent complications
that you observed? The most common issues we
documented included things like progressive glenoid
destruction, bone loss on the socket side, occurring
after the spacer was implanted but before re
-implantation, also post -operative hematoma,
subsequent shoulder instability after re -implantation,
wound healing problems, which are always a concern,
aseptic loosening of the eventual implant, meaning
loosening not due to infection, and periprosthetic
fractures around the implant or bone. The rates
did vary slightly across the subgroups, but that
overall figure of 58 % is a clear reminder of
the challenges involved here. Definitely sobering
figures. The study also, quite rightly, acknowledges
its own limitations. What are the key points
the authors mention there? Yes, we were upfront
about those. Firstly, it's a retrospective study,
meaning we look back at data already collected
rather than a prospective trial designed from
the start. That has inherent limitations. As
we've just discussed at length, we highlighted
the significant baseline differences between
the treatment subgroups RTSA, HA, SPACER, DATA
as a major limitation when trying to directly
compare their functional outcomes. There weren't
equivalent groups to start with. The relatively
small numbers in the HA and the SPACER subgroups
also limit the statistical power of those specific
analyses. You have to be cautious interpreting
results from small groups. And finally, there
was some loss to follow up. About 21 % of the
original cohort couldn't be included in the final
analysis for various reasons, which is quite
common in long -term surgical studies, but still
a limitation to acknowledge. Understood. So pulling
all this together now, the study confirms that
this two -stage approach is highly effective
for infection control, achieving that 95 % rate.
But functional recovery seems strongly linked
to patient factors and whether they can actually
proceed to an RTSA. What are the broader implications
of this for orthopedic surgeons who are considering
treatment options for shoulder PGI? Well, I think
it clearly validates the potential for a high
success rate in terms of infection eradication
using this demanding two -stage pathway, even
in complex referral cases. That's a positive
message. However, the discussion section in the
paper thoughtfully brings up the comparison to
single -stage exchange procedures. Right, doing
it all in one operation. Exactly. Some studies
investigating single -stage exchange, particularly
perhaps for less virulent organism or different
patient groups, report comparable infection control
rates to the two -stage method. So given the
high complication rate we saw, the patient burden
of multiple surgeries inherent in the two -stage
method, especially if the specific pathogen isn't
known right at the beginning. Well, the single
stage approach becomes a very significant point
of comparison and ongoing debate. It really highlights
that tension, doesn't it? Balancing the absolute
priority of getting rid of the infection versus
the goal of restoring function and minimizing
the overall impact and risk to the patient. That's
precisely the crux of it. It's not just about
clearing the infection anymore, although that
remains critical. It's about finding the optimal
path, the best strategy for achieving a functional
outcome with the lowest acceptable risk profile
for that specific individual patient. It forces
a really careful individualized assessment, doesn't
it? Looking at the patient's overall health,
the specific bug involved, the state of their
bone, and what they can realistically tolerate
and ultimately benefit from. Exactly. There's
no single one -size -fits -all answer in treating
shoulder PJI. Let's run through a quick lightning
round then for some rapid -fire takeaways based
directly on this research. Quickest win for infection
control, according to this study. The two -stage
method itself. It yielded that 95 % success rate
for eradication. Most common culprits identified
in this particular cohort. Coagulus negative
staphylococci and P. acnes were the top two.
Biggest predictor of functional improvement noted
in this study. It seemed to be the patient's
underlying condition and their bone stock, specifically
whether it allowed for an RTSA to be performed
in the second stage. A key diagnostic consideration
highlighted for shoulder PGI, especially when
you suspect P -acnes. Extended culture times
are crucial, at least 10 days incubation. And
one major challenge reeled starkly by the complication
rates. The significant inherent morbidity. The
risk of complications and the potential need
for further surgery remain very high in treating
these complex infections. Excellent summary points.
Okay, let's crystallize the core actionable takeaways
from this deep dive for our listeners. What should
they really remember from this? Okay. Firstly,
this study reinforces that two -stage resission
using antibiotic spacers is a highly effective
method for controlling shoulder PGI, achieving
a 95 % success rate in this particular series
of complex cases. Good. Takeaway number two.
Secondly, restoring good shoulder function after
treating PGI appears to be strongly linked to
the patient's suitability for receiving a reverse
total shoulder arthroplasty in the second stage.
and that suitability is largely driven by their
underlying condition and bone quality. Thirdly,
baseline patient factors, particularly the extent
of glenoid bone destruction, significantly influence
both the treatment pathway that can be chosen
and the ultimate potential for functional recovery.
This is often more critical than the specific
implant used in the most challenging salvage
situations. Fourthly, accurate diagnosis of shoulder
PGI requires diligent protocols. Especially important
is using extended culture times of at least 10
days, particularly to detect those slow growing
organisms like P. acnes. Don't miss the bug.
Crucial point. Fifth. Fifthly, be aware that
this is complex surgery with a notable risk of
complications. Nearly 60 % in this series experience
one, and there's a significant chance around
35 % of needing further revision surgery down
the track. Finally, the study's discussion and
our conversation today really prompts important
consideration of alternative strategies like
single -stage revision. These might offer comparable
infection control with potentially less patient
burden in certain situations, highlighting the
ongoing need to evaluate the optimal approach
for different PGI scenarios in patients. Professor
Immam, thank you so much for guiding us through
this research and providing such clear, really
insightful analysis. Your expertise as an author
on the paper has been absolutely invaluable.
It was my pleasure entirely. Glad to discuss
it. If you found this deep dive valuable, please
do consider leaving a rating or perhaps sharing
it with a colleague on LinkedIn or X. And to
leave you with a final thought based on our discussion
today, given the high infection control rate
with those variable functional outcomes and the
significant complication risks associated with
this two -stage approach, how should we as an
orthopedic community best balance that aggressive
infection eradication with the equally crucial
goals of functional restoration and minimizing
patient burden in these incredibly complex shoulder
PJI cases? cases. Something come all over. That's
all for this deep dive. Join us next time as
we unpack another stack of sources.