Mixing Crank Lengths for Leg discrepancy

Discussion in 'Cycling Equipment' started by irishunder23, Feb 12, 2007.

  1. irishunder23

    irishunder23 New Member

    Joined:
    Feb 12, 2007
    Messages:
    3
    Likes Received:
    0
    I broke my Femur a while ago after a Car/Bicycle accident and now my left leg is 30 mm shorter than the right one. This has been the cause of much back pain recently.
    I have read that to correct this difference in length on the bike you only need to go 1/3 of the length discrepancy, i.e. Build up the cleat on the shorter side by 10 mm.
    I recently bought a 165mm left crank for my bike which has got 175mm cranks. I am in two minds weather to bother putting it on or not,
    does anyone know if it is the right thing to do in my situation or are ther any other fix's?

    Suck that fucking wheel
    paulo :confused:
     
    Tags:


  2. 9.8mps2

    9.8mps2 New Member

    Joined:
    Feb 9, 2006
    Messages:
    106
    Likes Received:
    0
    I am anxious to hear a qualified response . It seems logical to just go through the fit process thoroughly, and setting up each leg independently with the modified crank. With that much femur difference you will need a smaller circle to maintain the same angular movement. Maybe fine tune by adding cleat height .
    You must have taken a pretty good hit.
     
  3. irishunder23

    irishunder23 New Member

    Joined:
    Feb 12, 2007
    Messages:
    3
    Likes Received:
    0
    40mph head on into a car during a race. cleat height you reckon? as in a shim under my cleat?
     
  4. bulaboy

    bulaboy New Member

    Joined:
    Jan 5, 2006
    Messages:
    135
    Likes Received:
    3
    My left leg is one inch shorter than the right. I use a 165mm crank on the left and 172.5 on the right. I got fit kitted last year with this set up and after looking at the video the guy fitting me said it worked perfectly. Your leg length discrepancy is just a bit more than mine so the 165/175 might just be the ticket! Good luck.
     
  5. 9.8mps2

    9.8mps2 New Member

    Joined:
    Feb 9, 2006
    Messages:
    106
    Likes Received:
    0
    Fek'in OUCH !
    Good that Bulaboy above had someone who knew what they were doing arrive at the same solution.
    I would think that to best stay away from the back difficulties ,priority would go to matching the saddle height - hopefully with just the crank difference, but if required shim to match. Your crank up position (leg most flexed) will likely vary from side to side - can't have both. Could perhaps play with the seat setback to "cheat " these angles and get the best symmetry. You be hav'in a custom ride for sure.
    I'll assume that you have an intact black sense of humor...I used to work for an orthopedic surgeon who could lop a bit off righty if you like ?
    Seriously, please post back with any results, it's very interesting to me .
     
  6. davidbod

    davidbod New Member

    Joined:
    Oct 7, 2003
    Messages:
    717
    Likes Received:
    0
    I think your on the right track here. When the difference is from hip to knee you need a crank length difference to adjust. Remember you want your knee over the pedal to be at the same position on the right and left side when the pedal is forward and horizontal to the ground. When the difference is in the lower leg, a shim would be used. I know for the shim you would only dial out about half the discrepency, but this assumes your body has adjusted over years to the leg length difference. The idea being if you dial it all out your over compensating for something your body has already partially compensated for.

    If your injury is recent you may need to dial it all out. Also with that much difference you need to be thinking shoe inserts to correct for walking running also. Bottom line though you should be able to talk to a Dr about this and get professional help.
     
  7. 9.8mps2

    9.8mps2 New Member

    Joined:
    Feb 9, 2006
    Messages:
    106
    Likes Received:
    0
    But remember dav ( I COULD be very wrong here ), a rider his age in Ireland may not have access to a KOALA outfit like we have here. It seems logical that he should be able to get some assistance in overcoming this "disability". A custom setup bike may well be his best tolerated form of excercise and rehab . I just don't know much about Irish healthcare.
    One things for sure , good on him for staying with it.
     
  8. alienator

    alienator Well-Known Member

    Joined:
    Jun 10, 2004
    Messages:
    12,596
    Likes Received:
    160
    What the OP needs is someone who can fit and/or analyze position and form for biomechanical issues. While a lot of the time, mechanically compensating for leg length differences (with shims and etc) is appropriate, there are also times when it is not. If your body has already adapted to the leg length difference, then compensating with shims or differentially sized crank arms can actually hurt you. You should consult with an orthopod, physical therapist, or someone hip to biomechanics.
     
  9. The Evil Twin

    The Evil Twin New Member

    Joined:
    Dec 14, 2006
    Messages:
    89
    Likes Received:
    0
    have you talked to an ortho surgeon? femurs can be lengthened using russian braces, it's long and painful.
     
  10. alienator

    alienator Well-Known Member

    Joined:
    Jun 10, 2004
    Messages:
    12,596
    Likes Received:
    160
    Ah the ol' Ilizarov methods. Fun! I had a rod in my tibia made "dynamic", as the surgeon termed, wherein he removed the screws from one end so that the rod would slide up and down inside my tibia allowing the fracture site to mash together a bit when walking to promote healing of a non-union. As fun as that was, I'd seriously decline any offer to have an Ilizarov lengthening done on you, unless you really enjoy pain.
     
  11. OldGoat

    OldGoat New Member

    Joined:
    Nov 13, 2006
    Messages:
    390
    Likes Received:
    2
    Maybe these guys could offer some suggestions; they specialize in issues like leg length discrepancy and custom adaptive equipment:

    http://www.hscycle.com/index.html
     
  12. bulaboy

    bulaboy New Member

    Joined:
    Jan 5, 2006
    Messages:
    135
    Likes Received:
    3
    I had 2 Ilizarovs done. The first was a non union and the second was to avoid amputation. They still screwed it up, which is why my leg is one inch short.
     
  13. alienator

    alienator Well-Known Member

    Joined:
    Jun 10, 2004
    Messages:
    12,596
    Likes Received:
    160
    Was your original fracture an open fracture?

    I went through 5 operations, one internal bone growth stimulator, and a couple funky external treatment modalities before mine healed. I feel your pain or at least can imagine how much it might have sucked for you.

    I think you should seek out one of the more advanced fit clinics, one that does video analysis of your cycling fit and technique. Who knows, if there's a biomechanics department at a local university, they may do such things. Again, I think you'd need such analysis to see what corrections are really needed.

    Good luck.
     
  14. barndoor

    barndoor New Member

    Joined:
    Oct 15, 2004
    Messages:
    9
    Likes Received:
    0
    As a US Chiropractor and cyclist I have a few thoughts. After so many surgeries and trauma, I would check with a chiro who can determine actual leg length difference from a functional difference. By this I mean your pelvis could be off by 5-10 mm. This would cause the legs to lengthen or shorten depending on which side is out of whack. Spinal adjustments to the lumbar spine and pelvis could stabilize the functional part of the leg length difference. Then the"actual 30mm" short leg may be more or less.

    After treatment a more accurate set up on the biike could be done
     
  15. bulaboy

    bulaboy New Member

    Joined:
    Jan 5, 2006
    Messages:
    135
    Likes Received:
    3
    My initial injury was in 1972. Got T boned while on a motorcycle. 3" of tibia was missing. !2 surgeries later (that incl skin grafts, bone grafts and the 2 Ilizarovs) I'm OK. Still some problems to be sure but I know what I can and cannot do and how to manage the problems. My fit on the bike is as good now as it's ever been.

    What happened to you?
     
  16. alienator

    alienator Well-Known Member

    Joined:
    Jun 10, 2004
    Messages:
    12,596
    Likes Received:
    160
    Ah, I see now. External fixators on tibia/fibula fractures are, well, a tough choice for a doc. Tib/fib fractures are the ones most likely to end up with some infection. Well, tib/fib fractures have the highest rate of infection among fractures.

    As for me, uhm, I highsided exiting a corner in a roadrace at 120mph. Right after the highside, I was alright....I just finished completely fracturing my right wrist which I had incompletely fractured the week before. However as I was sliding down the track at over 100 miles per, thinking how weirdly cool that was, I happened to look up to see my racebike re-entering the atmosphere. It landed on my right lower leg. The motorcycle jumped on my leg a couple more times as we bounced down the incline off the side of the track. Net result was that I busted my lower leg in 14 places ( I did learn, though, that you know you're having a bad day when you sit up in the ambulance to give the lost medics directions and you notice your foot is facing backwards....).

    At any rate. I asked the doc, after the first surgery when healing was seen to be problematic, why he didn't go for an external fixator. He said that such things are definitely not the first option since they carry a significant (although not necessarily big) risk of infection. The external fixators (of which Ilizarov splints are one type) require "damaging" the periosteum of the bone during placement, which in in turn decreases blood flow to the fractured area. Between the location of my fractures, the massive amount of swelling--even though he delayed surgery for 24 hrs to wait for swelling to reduce--and the fact that I'm a diabetic, he felt an external fixator was not worth the risk.

    Believe me, though, I understand exactly what you're going through. I had a friend who went through exactly what you have (including near surgical amputation and the placement of an external fixator) with a lower leg fracture. I also went through it with a patient of mine who suffered a very similar injury to yours resulting from the same sort of accident (t-boned by a car) and same sort of injuries (multiple lower leg fractures, open, and missing bone fragments). In both cases my friend and my patient went through years of procedures before things turned around for them.

    I had similar fit issues as you. One leg is now sigificantly shorter than the other (about 3/8 to 1/2" or so). I had fit issues and ended up getting video analysis done, the net result of which was 1/4" shim under cleat on the affected side. The video showed that my body had adapted such that all I needed was a 1/4". Shims larger than that caused perturbations in my cadence. 100+ mile days are no issue, now.
     
  17. CAMPYBOB

    CAMPYBOB Well-Known Member

    Joined:
    Sep 12, 2005
    Messages:
    11,945
    Likes Received:
    1,038
    Where were you racing...back east or out west? I used to RR at Mid-Ohio and Nelson's Ledges.


    I had polio when i was 2-1/2 years old. One leg is 1/2" shorter. I'm running a 172.5 crank and set the seat up to go with my shorter leg. For 34 seasons on a bike it's worked out fine for me. Good luck!
     
  18. alienator

    alienator Well-Known Member

    Joined:
    Jun 10, 2004
    Messages:
    12,596
    Likes Received:
    160
    Back east, at Nelson Ledges, the armpit of road race courses! Exiting the Carousel (er...the Turn 10 part), to be exact.
     
  19. CAMPYBOB

    CAMPYBOB Well-Known Member

    Joined:
    Sep 12, 2005
    Messages:
    11,945
    Likes Received:
    1,038
    Yeah...potholes, splits/cracks, speed bumps and an army of frogs on the back of the course.

    I had a buddy that REALLY got busted up coming onto the pit straight during the 24 hours of nelson. He hooked a crack, high-sided it and wound up with a busted arm, busted shoulder, busted ribs with collapsed lung, closed-head injury and compression fracture.

    Keep the rubber-side down, friends.
     
  20. bulaboy

    bulaboy New Member

    Joined:
    Jan 5, 2006
    Messages:
    135
    Likes Received:
    3
    Well if you're gonna wipe out you might as well do it with style. It's a credit to you that you were able to overcome the injuries as well as you have. After I touched down following my crash I lifted my head to check out the damage and my left foot was standing next to my knee like a boot. Is the strength in the shorter leg less than in the other? I find that my short leg just won't maintain the strength. I can devote months to bringing the strength up but as soon as I stop strength training the leg just shrinks back down again. The longer leg will always do more work than the short one and it is quite strong. If I had 2 legs like the good one I'd be an animal on the bike.
     
Loading...
Loading...