Welcome to Deep Dive Ortho. Today, we're getting
to grips with a really common yet, well, often
quite frustrating wrist injury, the trichetral
fracture. That's right. It might actually surprise
you just how prevalent these are. We're talking
the second most common carpal bone fracture.
Indeed. About 15 % to 18 % of all carpal fractures,
give or take. Which is significant. But despite
that, they're Let's face it, notoriously tricky
to diagnose, often just labeled a wrist sprain.
Exactly. Or if they're simply radiographically
occult, just don't show up on the initial x -rays.
So our aim today is to really give you a deep
understanding of these elusive injuries. We want
to look at the subtle diagnostic clues, the,
well, the surprisingly complex ways they happen.
Mechanisms, yes. Yeah. Which have evolved quite
a bit. And the latest thinking on management,
both conservative and surgical. We've got our
expert here to guide us through all this. Thank
you. It's great to be here. We're talking about
a small bone, the trichobrum, but one that plays
a really pivotal role in how the wrist works.
Can you just remind us where it sits anatomically?
Of course. So if you picture the wrist, the trichotrum
is this sort of wedge -shaped bone. It's in the
proximal carpal row over on the ulnar side, the
little finger side. OK. And its position is key.
It connects with several neighbors. The lunid
bone next to it, the pisiform sits right on top.
and the hamate is distal to it. Right. And it's
connection to the ulna. Ah, well that's interesting.
It doesn't directly touch the ulna. Instead,
it connects via the TFCC, the triangular fibrocartilage
complex. Disc. Precisely. Which acts as a crucial
shock absorber and stabilizer for that medial
side of the wrist. And another really important
point, its dorsum medial surface, the back, has
these two significant areas where ligaments attach.
strong ligaments. Ah okay so not just bone -on
-bone articulation but critical ligament anchor
points too. Exactly and that's why when the tricotrum
gets injured it's well it's really just the bone
itself the surrounding structures especially
those ligaments are often involved. It sort of
sets the scene for why these injuries can be
complex. That's a perfect setup. It immediately
tells us, we're not just dealing with a simple
chip. So let's dive into that complexity. How
do these fractures actually happen? There's been
quite a debate over the years, hasn't there?
Oh, absolutely. A real sort of historical back
and forth. It mainly centered around two competing
ideas, ligament avulsion versus impaction. Pull
versus push, essentially. You could put it like
that, yes. The traditional views were fairly
distinct. First, you had the ligament avulsion
theory. Right. This suggested that these fractures
particularly the common dorsal ones, happened
when a ligament attaching to the trichotrum was
pulled so hard, perhaps during a fall with the
wrist bent sharply forward and inwards, palmar
flexion and radial deviation, that the ligament
just pulled a fragment of bone off with it. Simple
tensile failure at the insertion site. Okay,
so a pulling mechanism. What was the alternative?
The alternative was the endocarpal impaction
theory. Garcia Elias, a well -known hand surgeon,
really detailed this. He proposed a chisel action.
Yes, the idea was that the ulnar styloid process,
that bony bump on the end of your ulna, acted
like a chisel. During forceful dorsiflexion,
bending the wrist back hard combined with ulnar
deviation towards the little finger. That classic
fall mechanism. Exactly. The styloid would supposedly
strike the dorsal aspect of the trichatrum and
chip a piece off. And this theory gained some
traction because some studies noted a slightly
longer ulnar styloid in these patients. They
measured the ulnar styloid process index, the
USPI. Right, I remember reading about that. I
mean USPI of about .29 was reported. That's the
figure often cited, suggesting a longer styloid
might predispose to this impaction. Then later,
Hucker and Menchik sort of expanded on this impaction
idea. How so? They suggested it wasn't maybe
just the ulnar styloid. They argued that the
edge of the hamat bone, the dorsoproximal edge,
could also act as a chisel against the trichatrum
in that same extended ulnar deviated position.
OK, so a similar impact mechanism, but potentially
from a different bony structure. So historically
it was pull versus impact, either from the ulna
or the hermit. That was the basic picture, yes.
But as often happens in medicine, things aren't
usually that simple, are they? What have newer
techniques, especially MRI, shown us? Has it
clarified things or, dare I say, made it even
muddier? Huh. Well, complex might be a better
word than muddy. But yes, you're absolutely right.
Modern MRI studies, like the one by Bess and
colleagues, have really peeled back the layers
here. OK. And their findings don't just tweak
the old theories. They, well, they challenge
some of the fundamental assumptions and show
it's often a much more mixed, multifactorial
picture. How so? Let's take the ulnar styloid
impaction theory first. What did the MRI data
show there? Well, firstly, the average USPI they
found in their patients was 0 .21. Which is normal.
Exactly. Within the normal range. Yeah. Not consistently
high like the theory predicted. But here's the
really interesting bit. The median USPI was actually
higher in patients whose injury story sounded
more like an avulsion 0 .27. Higher in the avulsion
group. Yes. Compared to those whose story suggested
impaction. where it was .20. So that directly
contradicts the simple idea that a long styloid
equals impaction fracture. It's clearly not that
straightforward. Okay, that's definitely counterintuitive.
What else did the MRI reveal about the ulnar
styloid's role? This is perhaps the most damning
evidence against the direct ulnar styloid chisel
idea. at least in the cases they studied. They
found no fracture or even bone marrow edema bone
bruising in the ulnar styloid process itself
in any of their patients with trichotral fractures.
None at all. None. And you'd really expect to
see some sign of trauma on the styloid if it
was directly hitting the trichotrum hard enough
to break it. That seems pretty conclusive for
those cases, doesn't it? It makes direct impaction
from the ulna seem unlikely as the sole cause.
It certainly makes it much less likely in those
instances, yes. However, The heme impaction theory
did get some support. Oh, OK. How? They did find
bone marodema in the hamat bone in nearly a quarter
of the patients, 23 .8%, which does suggest that
the hemo hitting the trichotrum, as Hucker and
Menchik proposed, could well be a contributing
factor in that extended ulnar deviated position.
So maybe the heme is the more common impactor
than the ulna. Okay, so the picture is shifting.
Less ulna, maybe more heme involvement in impaction.
What else complicated the simple avulsion versus
impaction story? Well, they looked at specific
fracture patterns using the Gersi -Alias classification
we'll discuss later. He'd suggested type III
fractures partially displaced at the distal end
were likely evulsions. And Besse's group did
find a lower mean USPI for these, .17, which
sort of fits. But crucially, they found this
type III pattern was significantly more common
in the group whose history suggested impaction.
Oh, right. So the pattern associated with a lower
USPI thought to be evulsion was actually more
common in the impaction group. Precisely. Yeah.
doesn't fit neatly into either box. It suggests
a real overlap, maybe a combination of forces
rather than one single mechanism defining the
fracture type. Okay, it sounds truly multifactorial.
And what about the ligaments in all this? Did
they find differences between the evulsion and
impaction groups there? This is probably the
most critical finding. Clinically speaking, they
found no significant difference in how often
associated ligaments were torn between the supposed
avulsion and impaction groups. Really? So regardless
of whether it looked more like a pull or a push
fracture? The surrounding ligaments were just
as likely to be injured. It strongly points towards
a complex combined injury mechanism where the
soft tissues nearly always take a hit, whatever
the primary force on the bone appears to be.
Wow. So the key takeaway is forget simple either.
It's a complex interplay and assume ligaments
are involved. That sums it up perfectly. It's
a dynamic event affecting the whole complex.
So if the mechanism is this complex, does that
translate into different types of tricatural
fractures? And more importantly, given what we've
just heard about ligaments, what associated injuries
should we really be looking for? Absolutely.
Yeah. Understanding the different fracture types
is key for management. For the common dorsal
cortical fractures, the Garcia -Elias system
is useful. It goes from type 1 Undisplaced. Just
a crack. Essentially, yes. Types 2 and 3 are
partially displaced, either proximally or distally.
Type 4 is completely displaced. Type 5 means
multiple fragments, more committed. And type
6 is a more significant vertical frontal fracture
involving the whole dorsal surface. Right. But
beyond those dorsal ones, what are the main anatomical
types? Broadly, we think of three main types.
First, the dorsal cortical fractures we've been
discussing, they make up the vast majority, 93
to 95%. And also called benign. Historically,
yes, but maybe that's misleading given the ligament
issue. They typically happen from falls onto
an extended ulnar deviated wrist, the impaction
scenario. But they can also result from avulsion
of the dorsal radiotricotrol or scaphotricotrol
ligaments, particularly in wrist flexion with
radial deviation. So same fracture appearance.
Potentially different initiating force. Understood.
What's the second type? Second are trichotral
body fractures. These are less common, but generally
indicate higher energy trauma. More serious,
then? Definitely. Because they involve the main
structural part of the bone. You often see these
alongside really significant wrist injuries,
like peri -lunar fracture dislocations. Ah, right.
Part of a bigger picture. Exactly. A trichotral
body fracture is found in something like 12 to
25 percent of peri -lunar injuries. It's a red
flag for major carpal disruption. The mechanism
is usually direct compression, axial loading,
or crush injuries. OK. And because they're central
in high energy, they're often associated with
a whole host of other problems. Lunar trichotrial
ligament tears, scaphoid fractures, distal radius
fractures. You have to look carefully for these
associated injuries. Missing them is bad news.
Absolutely. And the third type. The least common,
but potentially the most problematic for stability
are volar cortical fractures. On the palm side?
Yes. Usually caused by avulsion of the volar
ligaments, like the ulnotrichotrol or lunotrichotrol
ligament. Why are they more problematic? Because
those volar ligaments are absolutely critical
for maintaining the alignments of the carpal
bones. Injuring them carries a much higher risk
of leading to carpal instability, which can cause
long -term pain and dysfunction if it's not picked
up and managed correctly. They need a high index
of suspicion. So it really hammers home that
point about associated injuries. It's not just
the bone. And that best study you mentioned really
quantified this ligament issue, didn't it? It
really did. And the figures are, well, quite
sobering. They found that an incredible 95 .2
% of patients with dorsal trichatrial fractures
had at least one associated dorsal carpal ligament
injury. 95%. 20 out of 21 patients. It essentially
means if you diagnose a dorsal trichatral fracture,
you should assume there's significant ligament
damage until proven otherwise. That completely
changes the perspective from a simple fracture
or sprain? It absolutely should. The specific
breakdown is also revealing. Dorsal ulnortrichatral
ligament tears were seen in 81%. Dorsal intercarpal
ligament tears in 76%. And dorsal radiocarpal
ligament tears in about 67%. These ligaments
are almost routinely injured alongside the bone.
Is there any correlation between where the bone
bruising is on MRI and which ligament is torn?
Interestingly, no. They looked for that but found
no statistically significant link. Where the
bone marrow oedema was located didn't reliably
predict which specific ligament was injured.
So you can't rely on the bone oedema pattern
to guide you on the ligaments? Not reliably,
no. The implication is clear. High suspicion
of ligament injury is warranted in nearly all
cases, irrespective of the precise edema pattern
on the MRI. Okay, that 95 % figure is the one
I'll take away. Assume ligament injury. Now,
if we need to assess these ligaments, especially
with MRI, how well can we actually see them?
Are there imaging pitfalls we need to be aware
of? That's a very practical question. Generally,
3D gadolinium enhanced MRI using sequences like
VBE is pretty good. The best study identified
over 92 % of these ligaments in healthy controls.
So MRI is the tool. It's definitely our best
tool for soft tissues, yes. But, and it's important,
but visibility isn't perfect for all the ligaments.
Which ones are tricky? Well, the dorsal intercarpal
ligaments showed up very well. completely visible
in almost 97 % of cases. The dorsal radiocarpal
was also good, 80 % complete visibility. But
the dorsal ulno -tree control ligament was much
more challenging. It was only completely visible
in about 53 % of cases. And worryingly, it wasn't
seen at all in nearly a quarter. 23 .3 % of the
healthy controls. Not seen at all, even when
presumably intact. Exactly. So if you don't see
it clearly on the scan, you can't automatically
assume it's torn or absent. There might be technical
limitations. Why is that one harder to see? It's
likely due, at least in part, to something called
the magic angle artifact. Right, I've heard of
that. Because ligaments are ordered collagen
fibers, If they lie at roughly 55 degrees to
the main magnetic field of the MRI scanner, they
can produce an artificially high signal. Making
it look like a tear. Precisely. Or just making
it blurry. The dorsal ulnitricular ligament has
a curved path, and combined with the short echo
time, TE, used in some sequences, it's particularly
susceptible. So you have to interpret findings
relating to that specific ligament with a degree
of caution. Reported tear rates might be slightly
inflated due to this artifact. That's a really
crucial point for interpreting MRI reports. Combine
the imaging with the clinical picture and be
aware of potential artifacts. Absolutely. Clinical
correlation is paramount. Know the limitations
of the test. Which leads us perfectly into evaluation
and diagnosis. Given these challenges, occult
fractures, tricky ligaments. What should alert
us clinically? What's the typical presentation?
Well, the starting point is always that high
index of suspicion, especially with the right
history. Clinically, patients usually complain
of quite specific ulnar -sided wrist pain. Often,
yes. They might say it's worth with bending the
wrist, flexion, or extension. You often find
some swelling on the dorsal side. And the key
sign is usually localized tenderness right over
the dorsal aspect of the trichotrum. If you press
there, they'll likely jump. OK. And the history?
Typically, it involves excessive load or the
classic fall onto an outstretched hand injury,
often with the wrist extended and pushed towards
the little finger side, that ulnar deviation.
Right. Think of someone falling backwards. But
remember, the flexion radial deviation mechanism
can also occur. So keep an open mind. Some also
say wrist flexion can be more painful if it displaces
a dorsal fragment. Good tip. Now, the radiographic
challenges. You mentioned occult fractures. How
often are we talking? It's surprisingly often.
Some older studies suggested up to 80 % might
be missed on initial plane x -rays. 80%. That's
huge. It is. Even the best MRI study found 19
% were occult on the initial radiographs they
reviewed. It just highlights how insensitive
standard x -rays can be for these small, complexly
located bones. Compared to, say, a scaphoid fracture,
The combined sensitivity of clinical exam and
x -ray is often lower for the trichotrum. So
what x -ray views should we be ordering to maximize
our chances? You definitely need more than just
the standard PA and lateral, although the lateral
is often the most useful for seeing dorsal fragments
displaced posteriorly. Okay. You should also
get a 45 -degree pronated oblique view. This
can sometimes rotate the trichoderm out from
overlapping bones, and a radial deviation view
might help highlight volar fractures by tensioning
those ligaments. Any specific signs to look for?
There's the slightly amusingly named pooping
duck sign. The what now? The pooping duck. On
the lateral view, sometimes the trigger profile
looks a bit like a duck's head, and a dorsal
cortical fragment can look like it's, well, exiting
posteriorly. It's quite memorable. if you see
it. I'll definitely remember that one. But even
with these views, many are still missed. Yes,
a significant number. So the rule has to be,
if you strongly suspect a trichetral fracture
based on the clinical picture, but the x -rays
are normal or equivocal, you must pursue further
imaging. Which brings us to CT and MRI. If x
-rays aren't enough, what's the specific role
for each of these? When do you choose one over
the other? Excellent question. They both have
critical but slightly different roles. CT is
brilliant for bone detail. It's really the next
step if you suspect an occult fracture that X
-ray missed. better at seeing the fracture line.
Much better. The cross -sectional views cut through
the overlap issues. CT is also more accurate
for measuring the exact size and volume of any
fragments, which can be really important if you're
considering surgery deciding if a piece is big
enough to fix, for example. So high clinical
suspicion, negative x -ray CT for bone. That's
a very common and logical pathway, yes. But MRI
comes into its own, crucially, when you're worried
about instability or, as we've discussed extensively,
associated ligament injury. Which is almost always.
Which is in over 95 % of cases, according to
that best study. So MRI is often essential. It's
also useful if CT is negative, but you still
suspect an occult fracture, as MRI can pick up
bone marrow edema. the bruising, even before
a clear fractal line forms. And it shows the
soft tissues. Exactly. Ligaments, the TFCC, cartilage.
Given the high rate of ligament tears, you could
argue MRI is needed in most cases to get the
full picture and planned treatment probably to
avoid long -term problems like instability. So
it's not really an either with CT and MRI sometimes?
Often not. You might need both, depending on
the clinical question. CT for the bone detail,
MRI for the soft tissues, and subtle bone injury.
And don't forget to look at the other carpal
bones too. Best found edema in the hemat in nearly
24 % of cases and in other wrist bones in 19%.
It's often a wider injury pattern. Right, a comprehensive
assessment is key. Okay, let's say we've navigated
the diagnosis, we got the imaging, we know the
fracture type and any associated injuries. How
do we manage these? What's the first line approach
usually? For the majority, especially those undisplaced
or minimally displaced dorsal cortical fractures
without instability. non -displaced body fractures,
and stable volar fractures, non -operative management
is definitely the way to go. Good news for the
patient. Absolutely. The trichotrum generally
heals well thanks to a decent blood supply. The
mainstay is immobilization, usually for about
four to six weeks. How is that typically done?
Just a cast? It's usually phased. Yeah. Initially,
say for the first few weeks while things are
swollen and sore, a volar splint is often preferred.
wrist in slight extension. Oh, movable. Yes,
which allows for gentle range of motion exercises,
just wiggling fingers and thumb, and for hygiene.
Cold packs are also really helpful in this early
phase, especially the first 72 hours, to manage
that swelling and pain. Okay, split first, then
what? Once the initial swelling settles, maybe
around the 2 -4 week mark, depending on the case,
you might transition to a proper short arm cast
for more rigid support as healing progresses.
And after the cast comes off, usually around
four weeks, maybe slightly longer, you'd move
to a removable wrist splinter brace. This allows
for gradual increases in movement and starting
gentle strengthening exercises. The goal is regaining
mobility without stressing the healing site too
much. When can patients expect to get back to
normal activities? Weight -bearing activities
can usually be gradually resumed around eight
weeks post -injury, assuming things are progressing
well and pain allows. Full unrestricted activity
might take a bit longer. And the outcomes with
this conservative approach? Generally very good.
Most fractures manage this way heal well, often
with what's called a fibrous union. Not solid
bone. Not always solid bone, but strong fibrous
tissue connecting the fragments. And crucially,
this is usually completely asymptomatic. Patients
typically get significant pain relief and recover
good wrist motion, often within six to eight
weeks of starting treatment. So for most, surgery
isn't needed. That's very reassuring. But inevitably,
some cases do require surgery. What are the main
indications for going down the operative route?
Yes, surgery definitely has its place. The main
triggers are significant displacement of the
fracture fragments, clear evidence of carpal
instability, associated fracture dislocations
involving the trichotrum, or those relatively
rare cases of symptomatic non -union where conservative
treatment has failed and the patient still has
pain or mechanical issues. So instability and
significant displacement are key flags. Absolutely.
The goal of surgery is to put things back where
they belong, make the wrists stable, and optimize
long -term function. What surgical techniques
are typically used? It depends on the specifics,
of course. Open reduction internal fixation,
or ORAC -A, is common for displaced body fractures
or instability. So opening it up and fixing it.
Exactly. You make an incision, carefully reduce
the fragments back into place, and then fix them
internally. You might use small interfragmentary
screws to compress the fragments, or perhaps
K -wires, which are temporary pins. If ligaments
need repairing, you might use suture anchors
drilled into the bone. Right, like Herbert screws
for fracture dislocations. Herbert screws were
often used, yes, sometimes combined with K -wire
stabilization across the lunatric ritual joint
if needed. Okay, so... RIF is one option. Are
there others? Yes. Particularly for those problematic,
symptomatic non -unions. Especially if it's a
small fragment and not involving the joint surface.
Not articular. Precisely. In those cases, fragment
excision, just removing the troublesome little
piece, can be a very effective option. Just take
it out. Yes. Sometimes trying to fix a tiny chip
is more trouble than it's worth. There was a
case report of a young man with a tiny, painful
non -union, only about five millimeter. They
excised it. brief immobilization, and he became
pain -free. Others have reported success excising
slightly larger fragments, too. It's a good option
for selected cases. That makes sense for small,
non -articular, persistently painful fragments.
What about post -op? Still needs immobilization,
of course. Maybe six weeks in a cast, then a
brace, followed by rehab. Outcomes are generally
good. Maybe some slight loss of flexion or extension
compared to the other side. But usually satisfactory
function and pain relief. And crucially, You
have to address the associated injuries found
earlier. Absolutely vital. If the pisiform is
subloxed, you might need to excise it or fix
the trichotrum. If the lunotrichotral ligament
is unstable, it needs pinning or repair. Surgery
has to address the whole problem, not just the
trichotral fragment in isolation. It really highlights
that holistic diagnostic approach again. Okay,
so... After treatment, whether conservative or
surgical, what's the general outlook and what
potential complications should we be keeping
an eye out for long term? The overall outlook
is generally positive. As we said, functional
recovery is typically good to excellent for most
patients, even those with some associated ligament
issues provided they're managed correctly. People
often get back to good function relatively quickly.
That's good to hear. What about non -union? You
mentioned it's rare but can be symptomatic. Yes.
True non -union is uncommon, especially in body
fractures. Fibrous union is more frequent and
usually fine. But if a true non -union does occur
and becomes symptomatic, causing persistent pain
or clicking, that's when it can cause significant
disability and might need that surgical excision
or fixation we discussed. Okay. What other long
-term issues can crop up? Well, related to the
associated injuries mostly. TFCC injury is common,
especially with dorsal fractures. If it remains
symptomatic despite initial treatment, it might
need arthroscopic debridement or repair later
on. Right. Pizzotrich or periosaurosis arthritis
in the joint between the pisiform and trichotrum
can develop if the fracture went into that joint
or sometimes related to a nonunion there. If
that becomes painful, excising the pisiform can
be a good solution. Makes sense. And the big
one, though thankfully less common if things
are managed well initially, is persistent carpal
instability. This usually results from missed
or undertreated ligament injuries, especially
involving the lunotrichotrial ligament. It really
underlines why that initial thorough assessment
with advanced imaging is so incredibly important
to catch these instability patterns early. Absolutely.
Preventing that long -term instability seems
key. Well, this has been an incredibly thorough
exploration. We've really covered the ground
from presentation to long -term follow -up. We
have. It's clear that these fractures, despite
being common, are anything but simple. From understanding
the shift in thinking about mechanisms away from
simple, either to this complex, multifactorial
picture revealed by MRI, to appreciating that
staggering 95 % rate of associated ligament injuries,
it really changes the game. It really does. It
mandates that high index of suspicion and the
readiness to use advanced imaging like CT and
MRI, not just for the bone, but critically for
those soft tissues. It's about seeing the whole
wrist complex. Precisely. and then tailoring
the management, knowing that most do well with
straightforward immobilization, but also recognizing
the clear indications for surgery, like ORIF,
or even fragment excision when needed. This deep
dive has certainly illuminated a corner of wrist
trauma that deserves careful attention. It might
look like a small chip, but the implications
can be significant. Indeed. If you, listening,
found this deep dive valuable, please do consider
leaving us a rating or perhaps sharing it with
a colleague. And finally, a thought to take away
and perhaps ponder. Given everything we've discussed
about the extensive soft tissue attachments and
that near -universal ligament involvement, how
might future advances perhaps in dynamic imaging
techniques or maybe even intraoperative assessment
tools further refine our understanding of wrist
kinematics after these trick - How could that
ultimately help us improve long -term stability
and function for our patients even more?