Hip Wear From Cycling: Prosthetic / engineering type question.

[DirkV]

HI Cycling friends.
So cycling is low impact on our hips and good for recovery. Luckily, I've loved cycling since I got my first Schwinn Sting Ray in 2nd or 3rd grade and have been riding ever since.
Post surgery, I've been cycling more and more, enjoying pain-free riding with non-arthritic hips. I had a pause for concern on today's ride, when I did some rounded math. I'm training approx 10 hrs a week on bike. My average cadence is approx 85 / min. That's a total of 51,000 pedal strokes a week.
I know we're all kind of guinea pigs w/ relatively new surgical technique. Anybody w/ any engineering facts to assuage this concern?
I think we'd have to factor all the positive health results from physical fitness. And consider that most any exercise, even low impact, involves repetitive motion at the hip joint (walking, swimming, etc.)

A couple cycling asides:
Steve, read about your exploits in another thread: 40-plus miles 6 weeks or so post surgery. Incredible!

And a word of warning to other cyclists on this board. When Spencer says, "why don't you come down to Tucson for a ride?" He means it. And then the next thing you know, you'll be planning to climb Mt Lemmon.  :P Seriously, thanks for the invite. According to my stats, it's just under 6k of climbing over 30 miles, ending at some 8K of elevation. But it's a testament to what we can do w/ resurfaced hips that we can plan something like this 7 mo post surgery for Spencer and 10 mo after my last bilat.
Keep lookin up,
-Dirk

[Bionic]

I have no data yet but rather an observation.  A resurfaced hip bearing is not generally metal-on-metal when in use because the space between the components is filled with synovial fluid.  Moving the joint actually distributes the fluid so that most of the motion is actually metal on fluid rather than metal on metal.  This fact reduces the wear rate substantially as compared with that of a dry bearing.

Another observation is that bicycling may be easier on the hip bearing than other types of exercise, including walking and running.  The idea is that bicycling works the hip over a larger range of motiion than other forms of exercise and therefore tends to draw more synovial fluid into the bearing to lubricate it.  Another consideration is that the compressive forces on the hip joint during bicycling are generally (but not always) less than those during running or walking.

[Todd]

Funny thing the day my wife and I returned from the hospital to greet our 4 kids.  When my wife decided she was going to sleep in my daughter's room because I was so up and down during the night, my sensitive 8 year old son broke into tears thinking she was abandoning me because I was part "robot" as he says.  "Even though he is part robot, he's still the same dad."  Part robot is actually pretty accurate.  We are simple machines with very basic mechanical rules.  Lubrication, friction, force, etc. How we treat our new machine will determine how long it lasts and how it functions.  I'm happy there are good metalurgical engineers out there who know a thing or two about corrosion.  I'm pretty confident that they got things right.
ps. My wife did return to our room once I began sleeping through the night, so my son has come to terms with a dad who's part robot.
todd 

[sgoulet]

This answer is definitely not from a scientific perspective, but cycling is definitely easier for me right now than walking.  I agree with your assertion about cycling versus walking or running.

When I get on the bike right now -- indoor exercise bike or outdoor road bike -- I feel no pain and actually no effects of a new hip.  I still feel a little pain in walking -- especially at start-up.  I feel my "power" or strength on a bike is already back to about 90% of pre-hip state.

After I cycle for an hour, my groin, glutes, hip area, etc is very stretched and relaxed.  I am convinced that cycling is the perfect exercise for post-hip PT.

Steve

[dvander]

Hey!  I enjoyed reading the posts about cycling.  At almost ten weeks, I got on mine for the first time yesterday for a brief, relaxing ride.  Can hardly wait for warm weather to go long and hit it hard. What fun!!!! 

Thanks for the info.

Dwight V

[Bionic]

I'd like to see a model of the hip to get a better idea of how the hip joint moves during the normal bicycling stroke to see if there's any edge loading of the components.  The best my imagination can do right now tells me that the femoral component spins on its central axis while also rotating slightly internally (toward the mid-line of the body) on every upstroke, and then goes back to normal on the downstroke.  I think it needs to rotate internally to prevent the knee from swinging out (I'm experimenting with a dental probe as a model :) ).

Based on what I'm seeing, the internal rotation is pretty small, maybe 10-degrees, I would guess.  I think that's small enough with normally placed components to avoid any edge loading on the bearing.  Maybe I'll try to do the math later.

[DirkV]

Thanks for all the good replies.
-Dirk