I attended the BMC climbing injury symposium at the end of November 2016. Since then I’ve looked up a lot of the research on finger injuries to try put together a summary of what we know about pulley injury. The information comes from the presentations in the conference itself by leading climbing doctors Dr. Volker Schoffl (surgeon, climber 8a, and author of One Move too Many) and Dr. Isa Schoffl (Paediatrician, climber 7a+), David McLeod, as well as other published research.
Fingers are the most common sports climbing injury representing 52% of climbing injuries. Pulley injuries comprise a huge 60% of finger injuries.
Pullys are bands of connective tissue that hold the finger flexor tendons close to the bone. They allow the force from the flexor muscles translate into rotation and torque at the finger joints. There are 5 annular pulleys in the finger A1-A5. The A2 and A4 pulleys are the most important in restraining the bowstring of the flexor tendons and the A2 pulley is the most commonly injured.
How do they get injured?
They can get injured in crimp position associated with unexpected feet slipping off a hold, dynamic moves, or a lot of repetitive finger training when tired like campusing. A pulley tear can be associated with a popping sound, feeling of tearing, pain, reduced range of motion of the finger, some swelling and tenderness if you rub the area of the injury. In a bad tear involving multiple pulleys bowing stringing of the tendon can be seen on flexing the finger against resistance.
It is thought that injury occurs on pulleys due to two factors: 1. Pulleys having to resist a strong bowstring force of the flexor tendons, and 2. a sudden increase in the frictional stress of the loaded flexor tendon on the pulley for example when feet slip unexpectedly off a hold.
So what has the research found…
Dr. Isa Schoffl has also carried out research on pulley injuries in the lab and found that less force is needed to rupture a pulley on the eccentric motion i.e. tired finger suddenly releasing from a hold, than on the concentric (the action when you squeeze something like a stress ball). This is thought to be linked to friction between the tendon and the pulley when in a crimp position. The theory from friction has come from bats. Bats can hang from their “fingers” for days on end, or even when dead, without muscular tiring due to tendon locking off mechanism. This theory has been researched by Schweizer (2003) who showed there is a level of resistance between the flexor tendon and A2 pulley in the crimp position. However, when there is a sudden release of a hold due to fatigue or loss of a foothold the fingers experience a sudden increase in load and may injure the pulley.
In a small study Schweizer et al found that in the crimp position the force on the A2 pulley is 3 times the force applied to hold at the finger tip. It’s also been shown that the A2 pulley was 36 times more loaded in the crimp position than in the slope position (open handed grip). The force of the finger flexors in recreational climbers could theoretically be greater than 400N which is very close or beyond the maximum strength of the A2 pulley of 407N seen in cadaver studies.
The picture on the left shows the crimp position. The finger joint nearest the palm (PIP) is flexed, and the the joint furthest from the palm (DIP) is extended. It is thought that the more flexed the PIP joint the greater the stress on the pulleys. In the open handed position (pictures on the right) there is less than 90 degrees flexion in the PIP and there is flexion at the DIP joint.
How to reduce the risk of pulley injury
It was interesting to hear Dr. Isa Schoffl and David MacLeod that due to past injury they never crimp any more but favour an open-handed grip, or “3 finger swipe” in Dave’s case. Anecdotally it is thought that those new (ish) to climbing prefer a crimp position, and those who have been climbing longer have preference for more of an open-handed position – possibly due to stronger fingers from climbing longer, experience, or possibly as a result of previous finger injury.
To summarise the above and to add some more findings from Schweizer:
- The A2 pulley is 36 times more loaded in the crimp position than in open handed position
- The max force of a single (mono) finger in a slope grip is about 20% higher than in a single finger in a crimp grip position
- And a 5-finger crimp is just 5% stronger than a 5-finger sloping hold (open handed position).
- Other interesting information coming from the study by Schweizer is that at least 3 middle to long routes need to be climbed to get warmed up and be ready for maximum loads to the area of the finger tendons and pulleys. This would be similar to 100 climbing moves with 50 cyclical holds in the finger position to be trained on each hand e.g. same finger position you are going to use on finger board, campus board etc.
In summary…..to reduce likelihood of finger injury warm up well and work on developing open handed strength to reduce reliance on crimping.
Think you have a pulley injury?
If you have injured the pulley the outlook is good however the healing and rehab injury can take time depending on the extent of the injury. A complete multiple pulley rupture with obvious bowstringing would require referral to a hand surgeon.
Determining the extent of injury can be made in part by the history of the injury and the level of loss of function after the injury. An x-ray may be required to rule out a fracture to the finger particularly where there was a loud pop or crack sound on injury. An ultrasound or MRI can tell you more if you have health insurance, and if there is an experienced radiographer used to imaging fingers but it can take up to 2 weeks to make an appointment.
The majority of pulley injuries can be managed conservatively with a combination of treatment, immobilisation, rehab, taping, and a graduated return to climbing. This could take 6 weeks to 6 months depending on the injury severity and how patient you are (probably the biggest limiting factor to a return to climbing!!!). There is a culture amongst climbers to ignore finger pain until it really gets in the way of their climbing during which time the injury could be getting worse and their rehab time extending.
If you are aged 12-16 and you have finger pain after training or pain in your finger in the morning without a history of a trauma to it, then rest for 1 week (i.e. no climbing). If the pain does not go away or if the pain comes back on returning to climbing you must go to your Doctor to have it checked out. It could be a sign of injury to the growth plate in the finger joints which needs to be managed properly.
Moor B., Nagy N., Snedeker J, Schweizer A. 2008 Friction between finger flexor tendons and the pulley system in the crimp grip position. Journal of Clinical Biomechanics
Schoffl I., Oppelt K., Jungert J., Schweizer A., Bayer T., Neuhuber W., Schoffl V. 2009. The influence of concentric and eccentric loading on the finger pulley system. Journal of Biomechanics 42 2124-2128
Schoffl I., Oppelt K., Jungert J., Schweizer A., Neuhuber W., Schoffl V. 2009. The influence of the crimp and slope grip position on the finger pulley system. Journal of Biomechanics 42 2183–2187
Schweizer A., Frank O., Ochsner P.E., Jacob H.A. 2003. Friction between human finger flexor tendons and pulleys at high loads. Schweizer A, Journal of Biomechanics 36 63-71
Schweizer A. 2001. Biomechanical properties of the crimp position in rock climbers. Journal of Biomechanics 34 217-223
Vigouroux L, Quaine F, Labarre-Vila A, Moutet F. 2006 Estimation of finger muscle tendon tensions and pulley forces during specific sport-climbing grip techniques. Journal of Biomechanics. 39 2583-92