Imagine a doctor doing ordinary activities in his kitchen, stopping to draw some of the everyday objects around him, like an orange and a corkscrew. Then watch him turn those drawings into advanced patents for hip and knee replacements. Dr. Michael Ries holds 45 patents, and many of his ideas came to him in the kitchen. The remarkable efficiency of the human hip and knee are described here through simple illustrations, explaining why hip and knee replacements will never be quite as perfect as the joints we were born with. Health care professionals, patients considering joint replacement, students, and inventors will find The Joint Kitchen informative, entertaining, and thought-provoking. Dr. Ries shows that a state of tranquility allows the creative and problem-solving parts of the brain to connect and form new ideas that can transform and improve lives.
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START IN THE KITCHEN
THERE ARE A lot of great things in the kitchen. People have been eating food and preparing meals for thousands of years, and have pretty much figured out how best to do it. The best way to find out what's in the kitchen is to empty the dishwasher. This activity, which is also generally viewed favorably by spouses or housemates, requires that you identify each eating and cooking utensil in the dishwasher and place the items in cabinets and drawers containing similar things.
When you empty a dishwasher can be important. Other people in the kitchen may stake out their own personal space, usually near the refrigerator or sink or stove. So the best time to empty the dishwasher is when no one else is there, or they know what you're doing and stay out of your way. Spousal awareness of your activity may also achieve important appreciation points possibly redeemable for future personal favors.
Most of the items in the dishwasher — plates, bowls, glasses, and silverware — are generally familiar. So, it's not too difficult to figure out where they go. After that, there may be some things that are unrecognizable, and therefore more of a challenge. These represent more advanced kitchen aids like a meat tenderizer or garlic press. You can quietly hide them in some obscure cabinet or shelf, but it's probably better to just ask someone with more knowledge and experience what it is and where it goes.
Finding a place to put the cheese grater can be difficult, because there are no other cooking items in any way similar to it. If there are no other similar utensils in any of the cabinets or drawers, you don't really have an obvious spot to put it. You could ask where it goes, but no self-respecting adult with a Y chromosome would admit such ignorance, but us Xers might. If there is no obvious spot to put something, us males might just put it anywhere.
This seemingly lackluster response is, actually, thinking outside the box. Maybe it's a small box, but still a box of conventional wisdom. Let's pretend that we put that cheese grater in some random drawer or cabinet. It's no longer in sight. Mission accomplished, correct?
Now, step back and analyze what really just happened. There is a specific reason that you put it where you did, but you probably don't know (or really care) why you chose that spot. Now you just invented something, a never-been-used-before spot to put the cheese grater. The point here is that creative thinking occurs on many levels, and we subconsciously do it every day.
When I look at a cheese grater I see a remarkably efficient and simple tool. It is inexpensive to manufacture since holes are just punched into a flat metal sheet. Designing engineers seek to replicate the same simplicity and efficiency in surgical instruments.
Orthopaedic surgeons use a similar device to prepare bone for the acetabular socket of a total hip replacement. A "cheese grater reamer" rotates with a battery operated power tool like a drill or router to grind up and remove bone. It shapes a hemispherical cavity in the pelvis to fit the acetabular cup socket of a total hip replacement.
TOTAL HIP REPLACEMENT is a wonderful treatment for arthritis. We have been doing hip replacements since the late 1960's, and the procedures and results have improved over time.
The arthritic wear of the cartilage can be seen very easily on an X-ray as narrowing of the joint surface, or space, between the hip ball and socket.
Orthopaedic surgeons are affectionately referred to as orthopods because of their extraordinary physical strength, genetic predisposition to understand and use carpentry tools without any prior instruction or training, and unparalleled knowledge gained through years of fixing things — like broken bones, arthritic hips, and household appliances.
A "total" hip replacement just means that you replace both the ball and the socket. There are two basic metal parts that attach directly to the bone–the stem which goes into the thigh bone (femur) and the cup or socket, which goes into the acetabulum (part of the pelvis). The artificial parts are usually made from titanium, which bone adheres to nicely. A plastic liner fits into the metal socket and a ceramic or metal ball fits onto the end of the stem so the bearing surface of the joint is formed by the ceramic or metal ball and plastic liner.
Once the parts are assembled, the replaced hip moves freely and rotates like a normal joint.
During hip-replacement surgery, the hip is dislocated (ball removed from the socket) and the acetabulum, or socket, is prepared with a "cheese grater" reamer to remove the arthritic cartilage and bone and make a smooth surface for the metal acetabular cup to fit into. The reamer creates a hemispherical cavity (half of a circle) in the bone.
Now, don't freak out at the next photo. Just imagine Julia Child and her veal chops.
Everyone knows that bones break when you fall on them hard enough. But bone is more like a tree limb than a rock — it bends before it breaks. In order to create a tight "press fit" of the metal cup inside the hemispherical bony cavity, the cup is slightly larger (oversized) compared to the dimensions of the reamed cavity — usually 1-2 mm. The cup is impacted into the acetabulum (with a mallet, which is a metal hammer) or "press fit," which improves stability of the cup and encourages osteointegration, or growth of bone into the outer surface of the cup, by a process that resembles fracture healing. When the reamed bony hemispherical cavity is expanded by impacting, or press fitting an oversized cup, it opens toward the rim and becomes more of an elliptical shape than a hemisphere. The cup is also hemispherical like the cavity in the bone into which it fits, but the cup is slightly larger, so it fits tightly into the bone. This means that when the cup is inserted into the bone the outer rim of the bone expands.
INTO THE SILENT ZONE
If you are in the kitchen you might notice that a cut orange has a similar shape to the cup and the reamer — a hemisphere.
Well, the only way you can eat the orange is to cut it in half again. Then it sort of spreads apart and resembles a shape that's wider than when it started.
I pretty much do this every morning.
One day a friend of mine who works for a company that makes hip and knee replacements pointed out to me that two competitive companies make widened acetabular cups, which fit more tightly inside the reamed bone than hemispherical shaped cups. One of these has wider rim and is called a Dual Geometry or Dual Radius cup. Its design is protected by United States patent 4704127 and this is what the patent drawing looks like:
The other one has an elliptical shape. It's also patented, United States patent 5443519, and looks like this:
The next morning before breakfast I drew a picture of a cut orange on a napkin and sent it to my friend. Shortly after my drawing was redone professionally and became United States issued patents 5676704, 5782928, and 5879405.
The invention worked and is named the Interfit® prosthesis. (Smith and Nephew, Inc. Memphis TN) acetabular cup.
HIP REPLACEMENTS WORK great and many people have them now, but like anything else they can get old and wear out. If a hip replacement wears out or isn't working right for, it can be fixed, which means having a redo or revision surgery. The old cup is removed and using larger reamers; a new cup is installed. The old cup was pretty much the same size as the normal or anatomic acetabulum; but the new cup is bigger. We call the revision a "jumbo" cup. It usually doesn't fit as well as the old or primary cup, so screws are used to fix it to the bone. This also works well, but there are some annoying issues with the "jumbo" cup.
First of all, the middle of the jumbo cup is a little higher than the middle of the smaller primary cup. This is just a geometric fact.
The next ugly little side effect about the big cup is that it's wider than the old cup and protrudes into the front of the pelvis. If you look at the hip from the side, a cup that would be used in a primary hip replacement has bone all around it.
The word iliopsoas comes from ancient scholars who only spoke Latin. Since we don't speak Latin anymore, we now call it the psoas (p is silent so it's pronounced "soas"). The psoas is the main flexor muscle of the hip, so it's used when you lift up your leg to get in a car, get out of a chair, go upstairs, ski, get out of sand traps, and carry groceries into the house. After a jumbo cup is put in the hip, the psoas can rub on the front edge of the cup which causes tendonitis (pain) whenever the muscle is used.
There is not much we can do for psoas tendonitis. Physical therapy and injections sometimes help. If that doesn't work then surgery to tenotomize (cut) the tendon into two pieces stops the pain. Unfortunately this means that the muscle no longer works and the hip is weak. That's just the way it is.
INTO THE SILENT ZONE
If you get up early in the morning, before anyone else is awake, you are on your own. The first instinct is to look in the refrigerator. Some things like yogurt and orange juice are pretty easy to consume since you don't have to cook them. Toasting a bagel is also somewhat intuitive. The next step is cooking an egg, which requires a more advanced skill set, slightly beyond operating the microwave.
To fry an egg you need to look at it in the frying pan to figure out when it's done. Sometimes it's hard to tell. You don't want to burn it, but you also want to wait long enough that the whole thing is not too gooey. The yolk is never really right in the middle.
What is the egg's connection to hip replacement?
The egg resembles a jumbo acetabular cup, but the center (yolk) is at the bottom instead of the middle. If somebody made a jumbo cup with the same shape as the egg then the hip center wouldn't be elevated, which would be nice.
The invention is called the Restoration Anatomic Shell (Stryker Inc., Mawhaw, NJ).
Now this one also happened in the morning, which is when you cook breakfast. I don't know if the fried egg directly inspired the new acetabular cup idea, but every time I fry an egg I can see its shape. It's sort of a chicken and egg story. Who knows if the egg came first or the new acetabular cup idea, but they are connected somehow.
A HIP REPLACEMENT IS a ball and socket joint just like the normal hip. Once in a while, sometimes when the muscles are weak or the prosthesis is not ideally positioned, a hip replacement can dislocate (pop out of the socket), which causes incapacitating pain. Then it needs to be reduced (put back in the socket), usually under anesthesia.
Occasionally this gets to be a recurrent problem and requires more surgery to fix it. One method is to use a constrained cup socket in which the ball fits into a plastic polyethylene liner. A metal ring is placed around the rim of the plastic to prevent the ball from separating. The ring makes the outer circumference of the cup smaller so it restricts hip motion, which is not great solution. Over time this mechanism often breaks.
Another way to improve the stability of the hip is to use a dual mobility prosthesis. Dual mobility hip replacements have a large round mobile plastic bearing that surrounds the metal ball, and fits into a metal socket. These implants had been used for many years in Europe before they became available in the United Sates.
These make the femoral head (ball) bigger, which helps increase hip motion, and are difficult to dislocate, but they still can. When they dislocate, the two parts of the femoral head can separate, which is a problem. If this happens, then surgery becomes necessary to fix it. It would be nice if the dual mobility head could be constrained within the socket, preventing the two pieces from separating. If the metal liner extended past the equator, then it would constrain the head.
Of all the common kitchen items I routinely encounter, none influenced an invention more directly than the common canning jar. Often, they're invisible, but their simplicity is brilliant.
INTO THE SILENT ZONE
Occasionally a jar can wind up in the dishwasher. Who knows why? Maybe one of the kids put it there because the garbage was full. Maybe your wife put it there because she wants to use it for something important. Now you've got to find the top. So now you are holding the jar top upside down to look at the inside and see if it's the right size to fit the jar. Maybe no one ever pointed this out, but the jar top has four tabs.
The tabs on the jar top sort of look like the rim of the constrained cup that extends beyond the equator. If the rim of the liner is more like a jar top with tabs, then the dual mobility head might be fitted with threads that could be screwed into the liner. That might work, I thought. The threads allow the head to be screwed in past the outer rim of the liner and then it can't separate.
So there it was right in front of my nose — a constrained dual mobility cup. This one occurred in the kitchen while holding a jar top. My patent on the devise has been filed and is pending.
KNEE REPLACEMENTS ARE a great treatment for arthritis — maybe not as good as hip replacements, but still pretty effective. There are three bones in the knee: the femur (thighbone), tibia (shinbone), and patella (kneecap). The patella is connected to the quadriceps muscle over the front of the knee. The femur and tibia are connected by ligaments, which are made of strong collagen fibers, so the knee bends like a hinge joint. It also rotates a little bit as it bends. The knee has four ligaments — two on each side (collateral ligaments) and two inside the middle of the knee (cruciate ligaments).
In a knee replacement, the anterior cruciate ligament is removed because it's in the middle of the knee and in the way of the replacement prosthesis. After the anterior cruciate ligament is removed the knee is less stable. A lot of people who injure their anterior cruciate ligament need to have surgery to fix it. There is also a posterior cruciate ligament. Some knee replacements retain the posterior cruciate ligament, called cruciate retaining, or CR.
When the two cruciates merge they twist around each other, which helps the femur rotate externally (outward) as the knee bends. This is called the screw home mechanism, which makes the knee fully flex and the quadriceps muscle to work efficiently. Unfortunately, when there is only one cruciate ligament the knee doesn't rotate normally.
The posterior cruciate ligament can be removed during knee replacement and replaced with a vertical rectangular shaped post on the tibial insert and a cam, or transverse bar, on the femoral component between the two condyles (inner and outer curved joint surfaces on the end of the femur). This is called a posterior stabilized or PS knee replacement.
The PS knee has the cam and post for posterior stability. That's fine, but it doesn't rotate or do the screw home movement like the normal knee. If the femur doesn't rotate externally (outward) as the knee bends, then the knee may not bend fully and the quadriceps muscle loses some efficiency. It would be nice if when the replaced knee bent (flexed) it also rotated, but it doesn't. So the replaced knee works OK but not as good as the normal knee.
INTO THE SILENT ZONE
Have you ever tried to open a wine bottle without a corkscrew? It can't be done. The corkscrew is an essential item for every kitchen and household, and deserves a prominent position in the front of the uppermost silverware drawer, so it's easy to find and easy to return to the right spot. The corkscrew rotates as it goes into the cork and unwinds as it retracts; it moves up and down and rotates.
The cam of the PS knee contacts the top part of the post when the knee is relatively straight and then moves down the post toward as the knee bends. The post is rectangular shaped. So how about twisting the post like a corkscrew? I thought.
Excerpted from "The Joint Kitchen"
Copyright © 2017 Michael David Ries, MD.
Excerpted by permission of Koehler Books.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
I. START IN THE KITCHEN, 5,
THE ORANGE, 9,
THE EGG, 18,
THE JAR, 28,
THE CORKSCREW, 35,
II. GO OUTSIDE, 44,
THE CHAIR LIFT, 45,
THE DRY FLY, 56,
SNOW ON THE ROOF, 74,
THE GARAGE, 81,
III. FINISH THE JOURNEY, 91,
About the Author, 102,