Less invasive hip replacement has been all the rage this past decade. Often called, “hip resurfacing”, the concept seems attractive. You take out less of the arthritic hip joint and because the hip joint device is smaller, you can use a smaller incision. In fact, while in cardiology “minimally invasive” means treating someone through a needle and vein, in orthopedics that moniker has often been applied to slightly smaller versions of big surgeries. However, is this “minimally invasive” surgery really less invasive? Are there problems with this hip surgery?
To make the smaller surgery work, the doctor has to use a metal on metal implant. However, there have been a raft of issues with metal on metal devices. The FDA has clamped down on these metal hip replacements due to their side effects. In fact, quite a few studies have shown high levels of metal in the blood due to the wear particles given off by the devices. One manufacturer has had issues with recalls due to the high failure rate of the hip devices (40% went bad after 5 years).
With all of those issues, it wasn’t a big surprise to see another study this morning that shows higher cobalt and chromium metal levels in patients who had hip resurfacing when compared to traditional hip replacement. What was a shocker was that these patients have structural changes in their brains on MRI that weren’t found in the traditional hip replacement patients! Which areas had problems? The occipital cortex (where signals from the eyes are processed) is one of the regions of the brain that showed issues. The optic chiasm (the part of the brain where the eye nerves cross) also looked different in these hip resurfacing patients. In summary, the structural changes in these patients seemed to revolve around the visual system. Why? Problems with hip replacements and vision have been reported by others as well. Animal studies have shown that high cobalt metal levels can effect the nerves in the eye. Hearing and vision loss are also commonly associated symptoms with both chromium and cobalt toxicity.
The upshot? Elevated blood levels of metals are a big problem in many joint replacement devices including knees and hips. The worse of these implants seems to be metal on metal hips. It’s downright scary to consider that you can see and measure changes in the visual processing systems of the brain in asymptomatic patients who have undergone hip resurfacing!