Joint Adventures

The cells in our bodies are constantly being replaced naturally. Like the Ship of Theseus, am I still me? I feel like it’s the same me but with inevitable deteriorating physical capabilities as I age. I hope I retain my mental acuity, but there may come a point where I don’t recognize others or even myself. We consider aging a natural course of events although we don’t know exactly why our bodies have a clock that winds down towards eventual death. But thanks to doctors, scientists, engineers and inventors, there are artificial replacements for the wear-and-tear.

 

Which body parts can be replaced and what can they be replaced with? This is the question prompting Mary Roach’s latest book, Replaceable You. I’ve enjoyed several other books by Roach, who deftly combines humor, fearlessness, all while she teaches you some very interesting facts about the limitations of being humans and possibly how to get around them. She also somehow gains entry into surprising places and manages to get people to divulge interesting information that is unexpected. With words, she also capably paints a picture of the sights, sounds, and smells of wherever she happens to be.

 

Today’s blog post is on Chapter 8, “Joint Ventures”, subtitled “woodworking without wood”. As a reader, I feel I’m transported by Mary’s Adventures. To give you a taste of her writing, here’s how the chapter begins: “The third hip replacement of the morning looks very much like the second and first. The patient and the whole operating table are covered with surgical drapes, resembling not so much a person having surgery as a small vehicle under a tarp. A surgeon stands alongside, holding a metal instrument in a hole in the patient’s side. The hole – the incision – is held open by a circular plastic retractor the size of an automobile gas cap. From where I stand, six feet back, this is all I can see. Hip replacement has the visual drama of a visit to a Chevron station.”

 

The next paragraph begins in an arresting way: “It’s the sounds that undo you. The whine of the bone saw as the surgeon cuts…” I’ll stop describing here, but you can bet that Roach makes plenty of comparisons to a woodworking shop. But there’s a major difference as Roach goes on to describe: “A (wood) cabinet has no immune system. It doesn’t throw up defenses against building materials it perceives as hostile invaders. It doesn’t die under siege from bacteria that gained a foothold on a piece of inlaid metal or plastic. In other words, the surgeon’s skill can take you only so far. It’s the material guys you’re depending on for a lasting, complication-free build.”

 

My aging mother has had both hips replaced in the last three years. I’m glad for the significant pain reduction that has resulted, and the efficiency of modern medicine. I don’t recall exactly what materials were used, but Roach takes me through the history of such joint replacement starting in 1938 when stainless steel was used for both stem and socket cup. Titanium and other alloys eventually replaced this, but metal-on-metal wear and tear can result in debris that leads to inflammation. Ceramics (metal-oxides) can reduce the wear but their underlying brittleness can be a problem in a high-impact situation. Teflon was used at some point, but there were problems; compact polyethylene has proved better. And so it goes in the evolution of materials. The challenge, as Roach notes, is that “you can’t know for certain how a material will perform or react until you put it into a patient and watch what happens for five, even ten, years. Yet the time required by the FDA to establish the safety of a new medical devices is often shorter.” Worse, there’s a “minor changes” loophole that can avoid clinical trials.

 

Ivory turns out to work surprisingly well. We know this from a surgeon in Burma who managed to persuade a local ivory carver to fashion “knob-topped stems to push inside people’s bones, where no one would even see them. It was like trying to hire Georgia O’Keeffe to paint the janitor’s closet.” No wonder most of the artisans turned him down. The surgeon performed hundreds of successful surgeries with only a two percent failure rate, which is an astoundingly successful rate, given this was in the mid-twentieth century. Part of why is the low infection rate with ivory even without antibiotics. There’s a tricky balance at play: Ivory is very smooth providing fewer nooks and crevices for bacteria to invade, but modern materials are also intentionally made porous to encourage bone growth. You want the bone to grow in before bacteria can proliferate. I also learned that an exception comes from dental implants because saliva and possibly our gum tissue seem to have natural antibiotics because the mouth is literally a cesspool. The stringent “clean” practices in joint replacement surgery have evolved significantly to reduce infection rates, and Roach gives credit to those who painstakingly tested different protocols.

 

I haven’t named any of the people Roach discusses as she sets up her joint-replacement learning adventure. That’s because Roach has some very funny bits about the name coincidences; you can get your hands on her book and read them laughing out loud for your own enjoyment. Her acknowledgements section is also hilarious, where she thanks all these people who said “yes” to her invading their workspaces and pestering them with questions. You might also want to know about all those other body parts you might want to replace and where we are with the technology. Let’s just say I was surprised at the very wide range of stuff discussed in Replaceable You. You might be surprised too!