Handling bones and other calcified tissue
Seth L. Haber, MD
Let’s continue this vade mecum on the handling of bones and other calcified tissue, which we began in the December 2003 column. There, we had discussed safety, orienting the specimen, fixation, decalcification, marking the tissue, and saws.
These innovations are based on the experience and expertise of Izak B. Dimenstein, MD, PhD, HT (ASCP), of Loyola University Medical Center, Maywood, Ill., and my experience at Kaiser Permanente Medical Center, Santa Clara, Calif.
Saws and other instruments
After reading the December column, Adrian Winters, PA, of Temple, Tex., wrote
to tell me that Mar-Med in Cleveland (440-572-5175) makes an 18-pound tabletop
band saw (about the size of a microscope), with a diamond blade, that is reputed
to be safe, convenient, and easy to clean. Furthermore, it’s quiet and raises
almost no aerosol of bone dust. Ron Seink at Mar-Med referred me to Frank Tringale,
HT, HTL, supervisor of histology services at Stanford University, who recently
bought one and was willing to demonstrate it for me. It was so impressive that,
after I worked with it for a while, I was willing to offer up the tip of my
fifth digit "for the cause." I gingerly advanced it to touch the edge of the
blade when it was running, and applied pressure. I was surprised to get it back
intact, without even a break in the skin. Therefore, I humbly retract my condemnation
of all band saws as malicious, dangerous, and unnecessary space-occupying lesions-to-be.
If you need a band saw, Mar-Med’s Bone Band Saw ($810 with heavy grit saw blade,
foot switch, and guide/ fence) exceeds performance and safety expectations.
Properly used, it will cut down on your need for other saws, including the expensive
Stryker oscillating saw, which does raise an aerosol of bone dust, and other
You will probably want curettes and rongeurs for marrow and for biopsying cancellous bone. Hammers and chisels are essential-to carpenters and orthopods, who can sometimes be hard to tell apart. Unless you have a specific need or skill, you can probably do well without their tools. Never try to cut calcified material or insufficiently decalcified bone by pounding with a hammer on a scalpel blade, knife, Pathco razor blade, or single-edge razor blade. It can be dangerous and is generally ineffective. Fragments of steel from the blades may become embedded in the tissue, where they wreak havoc on microtome blades.
At Kaiser Permanente Medical Center in Santa Clara, we had an assortment of pliers. Choose an appropriate size locking (for example, ViseGrip) pliers. They come in several sizes, each with concave articulating surfaces designed for grabbing pipe, or flat parallel articulating surfaces. Sometimes you’ll want to use long-nose pliers, and they’re inexpensive. You might consider a couple of sizes of Channel-Lock pliers.
You’ll also want a couple of sizes of Russian Box-Tooth forceps and a few larger clamps that the OR is discarding. Also, to hold some specimens, look at the assortment of small plastic bar clamps (AKA pipe clamps, framing clamps) at the hardware store.
An overly generous assortment of saws, pliers, vices, and similar instruments, suitable for the needs and wants of several pathologists, will probably cost less than $200 to $300 at a hardware store like Sears or Home Depot.
At Kaiser Permanente Medical Center, we check the daily OR schedule against the list of patients suspected or known to have interesting hematological disorders. We then ask the surgeon to send us a piece of rib or other accessible bone. That gives us an excellent specimen, and the patient is spared an aspiration or biopsy. A large pliers is invaluable here for crushing the specimen and squeezing the marrow out. Just fix the coagulum and, after minimal decalcification, handle it like a soft tissue specimen.
Immobilizing the specimen
Archimedes said, "Give me a lever long enough and a fulcrum on which to place it, and I shall move the world." In working with bones, all of your tools and techniques (levers) are useless unless you have a "fulcrum" on which to hold the specimen in position while you work on it.
Most pathologists use some sort of custom-made or adapted wooden jigs to hold bony specimens. The problem is that the jigs are generally deeply scarred, contaminated, and almost impossible to clean properly, and they never quite fit the specimens. Don’t forget to wear those cut-resistant gloves, at least on the hand that holds the specimen.
Venture into a kitchen supply store like Williams Sonoma and look at the melon ballers. They look like a gangly pair of pliers with an approximately 2-cm metal hemisphere attached to each end. It’s designed to make it fast and easy to carve melon balls, but it’s great for holding specimens steady while you work on them. Ice cream scoops are great just to pin a specimen down while you work on it.
Although the wooden jigs, pliers, melon ballers, ice cream scoops, and bar clamps are all useful, every pathologist needs at least one good vice. Get the vice with a vacuum base, so you don’t have to clamp or screw it down to the dissecting table. It will stick to any flat Formica or stainless steel surface.
Now it’s time to throw away that wooden jig. Just as the neighbor whispered to Benjamin in "The Graduate" that the future is, in one word, "plastics," that’s what I’m whispering to you now.
At Kaiser Permanente, I could choose from among three possible hold-downs. The first is an appropriately sized piece of the sound-deadening tiles that are hung on ceilings or walls. It’s easy to press smaller pieces of bone into it for a form-fit depression.
The second was for slightly larger specimens; I used an appropriately sized block of firm polyethylene foam, which our receiving department was only too glad to get rid of. It is used to pack delicate or heavy equipment for shipping, and the receiving department generally discards it. Almost any major piece of laboratory equipment will come packed with enough of that material to last most of us for more than a year. Chunks of hard Styrofoam, from the same source, work almost as well, but small fragments of it tend to stick to most surfaces by static electricity.
With a scalpel blade or a Pathco razor blade in the proper handle, cut out an appropriate shape into which to press the bone. If it doesn’t fit perfectly, just press the bone down harder, and it’ll compress the plastic to a better fit. Fortunately, you don’t have to worry about risking your fingers by holding the specimen with them. Just tape the specimen into the custom jig you just created.
The third option was the most elegant. Form the ultimate custom holder from some of that insulating material that squirts out of a can like shaving cream. It expands about 10-fold and hardens quickly. You can use a specimen container of the appropriate size to make a mold, just as you embed tissue for a frozen section. Put a little at the bottom of the container and let it harden around the specimen. Then squirt in more foaming insulation to build up a mold around the bone. You can even combine techniques, squirting a little foaming insulation to hold the specimen in the polyethylene foam or Styrofoam block that you custom cut. If you roughen the surfaces of the polyethylene plastic, the foaming insulation will adhere better. You can minimize the problem of the foamed plastic sticking to everything by coating the tissues or shaped plastic jig with liquid soap, mineral oil, or cooking spray. All of these plastic holders are disposable and should be discarded when you’re through.
Don’t forget, the whole purpose of this exercise is to obtain a thin, well-cut, oriented, and decalcified specimen. The specimen should be about 2- or 3-mm thick and clear the sides of the embedding mold by at least 1 mm. Parallel hacksaw blades will make it easier for you to cut such specimens. In December, we suggested choosing a hacksaw with blade-holding posts that are long enough to hold the two blades, separated by small washers. The tissue should not be over-decalcified. You’ll know how well you succeeded by the histotechnologist’s teeth: Is he or she gritting them or showing them in a wide grin?
We know there’s more
I wish I’d had a guide like this when I was a resident. And I think I hear choruses of "amen" from my former histotechnologists.
If Dr. Dimenstein and I can devise and report so many innovations just on the
handling of bone and other calcified tissue, just think how many more innovations
on these and other topics could be shared by the thousands of CAP TODAY readers.
If you send your innovations to me, I’ll describe them in the June or September
column-with full attribution, of course-and we can all benefit from them. RSVP.
Dr. Haber is emeritus chief of the Department of Pathology, The Kaiser Permanente
Medical Center, Santa Clara, Calif., and clinical professor of pathology at
Stanford University School of Medicine. He can be reached at 1375 Pitman Avenue,
Palo Alto, CA 94301; phone 650-321-3441; e-mail slhaber@
stanford.edu; and fax 650-321-6773.