h a l f b a k e r yWe have a low common denominator: 2
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Today, my daughter broke her arm (she's
fine, and quite proud of her cast). She
fell
over and landed badly, and the school
nurse, not suspecting a fracture, gave
her
an ice pack on the assumption it was a
bruise. Only when we got her arm X-
rayed was it clear there was a break -
there
wasn't a huge amount of pain or
anything obvious, and nine times out of
ten it would have turned out to be what
the school nurse thought - a
bruise.
This got me wondering
if
there was some easier way to tell if there
were a fracture before schlepping
someone off to casualty for an X-ray.
Bones are pretty rigid (at least after early
childhood), and must transmit vibrations
quickly and well. So, suppose you had a
transducer which could be pressed firmly
onto the skin near one end of the bone
(*not* near the suspected fracture!),
which
sends out brief pulses of sound. A
second, stethoscope-like transducer
detects the sound waves arriving at the
other end of the bone and, from the
delay
and intensity, can tell whether there's a
continuous bone-path between the two
ends. If there's a fracture, then obviously
an X-ray is needed.
This
would probably
work only in certain cases. For example,
a
break in the ulna could be easy to detect,
since the transducers can be pressed
firmly against the wrist-bone (do I mean
the knobbly end of the ulna?) and the
elbow. Breaks in the humerus might be
harder to detect, since I don't think the
upper end of the humerus comes close to
the skin. But, in some situations, it
might
be a handy and simple diagnostic tool.
patent WO2004093686
http://v3.espacenet...DX=WO2004093686&F=0
A method of diagnosing a subject by delivering ultrasound signals to a bone surface [xaviergisz, Jul 13 2005]
Handheld ultrasound diagnosis of extremity fractures
http://www.ncbi.nlm...15376408&query_hl=5
...successfully identified long bone fractures in three patients using hand portable ultrasound... [xaviergisz, Jul 13 2005]
TDR or Time Domain Reflectometry
http://www.tscm.com/tdr.html
Look at the amplitude and the position of the reflections. A cable tester using this method can be held in the hand. [Ling, Jul 13 2005]
Curing broken bones with ultrasound
http://www.fda.gov/...tures/396_bone.html
[DrCurry, Jul 13 2005]
one I broke earlier.
x-ray_20machine_20n...the_20post_20office
[po, Jul 13 2005]
Forearm Diseases
http://focosi.alter...#forearm%20diseases
Elbows are discussed above this. [reensure, Jul 14 2005]
Journal of Trauma
http://www.jtrauma....!-949856031!9001!-1
Advanced Ultrasonic Diagnosis of Extremity Trauma: The FASTER Examination
94% accurate in 158 examinations performed in 95 patients. [reensure, Jul 16 2005]
Sonsonite, Inc.
http://www.sonosite...ducts_overview.html
Weigh in at as little as three pounds (compare to your Blackberry) [reensure, Jul 17 2005]
[link]
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maybe you could use a needle to actualy contackt the bone and transmit the vibrations along that. |
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You might need a very sensitive detector as the vibrations might travel through fractured bone if the two pieces are still in contact or there is another bone connecting the pieces. It is a cool idea though. [+] |
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great idea - I wonder if anyone's tried it before. |
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I like it! You seem to have two options: sound transmission and ringing. |
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A dry bone with nothing around it would certainly ring at a certain tone, much like a bell, but might not do so in the body. I was taught to test new grinding wheels for invisible cracks by ringing them. I once kept a cracked dinner plate just to demonstrate the difference in tone between it and a good plate. It may be possible to determine what the bone should sound like if not fractured. |
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I have this mental Norman Rockwell image of a kindly country doctor holding a tuning fork to a sobbing child's arm. |
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Of course medical use of ultrasound is baked, but I've only seen it for imaging and questionable physiotherapy. Ultrasound for bone flaw detection? Now that's got me thinking. Industry uses ultrasound for flaw detection, but I think the material has to be homogenous, which might be a problem here (plenty of noise from skin/meat/bone interfaces). |
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Later: ah, links. Righto. |
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Check for unusual reflections (time domain reflectometry), same as finding a fault in a cable, especially fiber optic cable. Compare left and right arms/legs to each other. |
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<aside> I have often wondered why the diagnosis is required, for minor fractures. Confirmation that it hurts? |
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//Compare left and right arms/legs to each other.// Brilliant, Ling! So obvious once it's mentioned. That is the key to this idea. |
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Hmm. The links show that ultrasound
can be used successfully, som I guess
this is partly baked. However, I
presume that the systems described are
using fairly sophisticated equipment
similar to that used for (eg) foetal
imaging? I was hoping for a simpler
system - just a couple of transducers to
measure time delays in transmission
along the bone, rather than imaging
through reflection. But on the other
hand, perhaps a "simple" system might
be too unreliable to be
worthwhile.
Ling's point
about comparing limbs is excellent and
would remove a lot of the 'noise' from
the system.
//I have often
wondered why the diagnosis is
required, for minor fractures.
Confirmation that it hurts?// Well, I
would have thought the same. But this
fracture produced no more pain than a
bad bruise, and she could rotate her
forarm and flex her wrist. Nevertheless,
the X-ray revealed a break right
through the bone which definitely
required a cast. I was surprised too. |
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a TDR system would be relatively simple: send a sound pulse down the bone, and listen for the echos. No need for an image. See link for example on cable testing.
p.s. Best wishes to your daughter. I hope it doesn't ache too much at night. |
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This is a great idea - I love ideas that will work with an affordable amount of current technology. Unfortunately the "needle into the bone" method would be both the most reliable and the most painful. |
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A agree the needle would give you the
cleanest signal, but it then becomes a
'procedure' and more of a faff than an
X-ray. Perhaps just a blunt pointy
probe (if you see what I mean) that
could be pressed against the skin where
the bone was nearest the
surface.
Assuming that bone-
transmitted sounds are significantly
faster/stronger than flesh-transmitted
ones (perhaps best for shear waves
rather than compression waves?), I'd
expect the skin-bone-skin signal to be
distinguishable from the skin-flesh-
skin one, though I don't know how clear
it would be. And as Ling said, an echo
returning from the break might be an
alternative method (would this work in
the case of an irregular shaft like a
bone, which can have bumps and
knobbles where muscles/tendons
attach?).
Ling - many thanks - arm
was fine last night, so hopefully it'll all
go smoothly. She was at school today
enjoying her fame! |
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In all fairness, couldn't the doctor just use a sonogram? And then start curing the fracture on the spot (see link). |
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The problem with having flesh in the way is that flesh tends to absorb high frequencies. The resonant frequency of a bone is pretty high already (I'm guessing here from the memory of what a dropped sheeps bone sounds like) and will double if there's a break in the middle. You might be right about the skin/bone/skin signal though - it will hopefully transmit *enough* hf. |
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How's about this: make a machine that fires a quick pulse of sound (pink noise would be good) into the bone (via the thinnest piece of flesh), records the resonance left behind in the bone (it will vibrate for a small fraction of a second), and stores an analysis of the frequency response of the sound. You then use it once on the injured arm and once on the opposite arm. The machine compares the two sets of frequency response data and tells you whether the arms sound the same or different. If they sound different there's probably a fracture, if not then there isn't (or it's very small). Best of all, this should be quite compact and cheap. [Dr C] - this could be made for £50-100 and kept in school first-aid cabinets. |
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[Wagster] - sounds plausible to me :-) I
guess in the end it's a case of suck-it-
and-see. I wonder if there's research
funding available to break kids arms?
But seriously, I'm glad the idea is at
least not completely unfeasible. Also
glad to hear you say "£50-100" - this
was the sort of thing I was hoping for
(not a hospital instrument, but a a first-
aid accessory). Certainly, any indication
of a fracture would be followed up with
a trip to hospital and an X-ray. |
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Injury to the growth plates of the ends (epiphyses) of long bones is the most significant, or at least is a major cause of adult deformities arising from childhood injuries. Most of these fractures and the subsequent nonunion that might develop, particularly after repetitive stress on the fracture site (read that as "suck it up and get back in there") are amenable to aggressive treatment. That is why proper identification of a child's injury is so important. |
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I'd be interested to know if there is a predilection to the onset of carpal tunnel syndrome in adults who were victims of mismanaged growth plate injuries as children. |
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//That is why proper identification of a
child's injury is so important.// I agree
- ideally you'd want to guarantee
detection of a fracture. Presumably, the
highest rate of non-detection of
fractures is in cases like my daughter's,
where there was little pain and it looked
more likely to be a bruise. I guess any
'simple' fracture detector would have to
tread a narrow line between false
alarms and false negatives. Too many
false alarms and you'll have people
wanting X-rays even though common
sense says it's just a bruise. False
negatives, on the other hand, would be
worse.
On the other hand, relying
only on 'eyeballing' and pain-levels
must also have a significant rate of both
false positives and false negatives.
(Incidentally, on a personal note, I
presume that the growth-plate at the
distal end of the ulna is pretty close to
the head of the bone and not a couple
of inches proximal to it?) |
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I'd hope so. There is a classical type of fracture of that bone. Watch the 5 Ps. These are pain, pallor, pulselessness, paresthesias, and paralysis. Pain is the earliest sign. Symtoms get no worse ... have no fear. |
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//pain, pallor, pulselessness,
paresthesias, and paralysis// Nah, she
didn't have any of those. What is this
'classical fracture'? I was surprised that
this one was clean across (rather than
having any longitudinal 'splits'. (Sorry,
off-topic here in a purely self-
interested way). |
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heh. Classical fracture: I'm surprised no one took the time to put a 'camp spin' on that. It's just something I say when I don't have a medical degree, but recognize a response to some specific injury that could only be named eponymously or by reference to specific tendons, nerves, or bony prominences involved. Again, I don't diagnose conditions. (see link) I'd rather you'd search to your own limit for that type of thing ... but if the condition isn't getting worse, there should be minimum swelling to produce nerve damage or contractures of any muscles. Beyond that, the likelihood of growth plate injury two inches proximal from a wrist is small, but the important thing to recognize is that stability and nourishment will heal the fracture quicker and with less risk of complications. |
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Ah. Well, one has to admire a good
bluff. If you ever need any dental work
done, let me know.... :-, |
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[Basepair] I sympathize with your daughter as we will both be recovering from broken bones. She will sooner than I, I assume.
I wonder if this is the chance for her to become a baker? Perforated or Castellated Casts? I imagine that the standard cast is a pain in the cast for those that have to endure it.
If when formed, the cast is wraped in a perforating or castellating plastic forming agent, the aeriation of the skin underneath the cast might be a such a relief that those who've not had such would should wiggle with joy at the concept?
I knew at once I broke my bone as I heard it snap/pop (in 4 pieces). I support this idea with all of my heart & pain.
My best wishes for the recovery of your daughter! |
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Thanks, [Zimmy]. I also worry about the
close skin contact of a conventional
plaster - I'm amazed that the skin
doesn't get infected with such long
enclosure. (I understand, though, that
things do get pretty manky in
there!).
A 'breathable cast'
would be good if it doesn't already
exist. I also wondered if casts couldn't
be 'accessorized' to compensate for the
loss of limb-use. A few clipboard-style
clips and knobs would be handy for
holding things; perhaps also a pen-
holder (not to write with, but to store
the pen), an inbuilt watch....the list is
endless. |
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<HB off topic> ... mmm liability. </> |
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When radiographs can be relayed to a remote emergency doctor, I think a school nurse (for example) would be in a far better position to decide if a call to EMS is necessary. |
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