THUMB INJURIES FROM SNOW SPORTS
Hand injuries in general tend to be disregarded by both patients and doctors - until you happen to sustain one yourself. Never was this more the case than in thumb injuries - you really wouldn't believe how important your thumb is until you have injured it. Your thumb allows the movement of opposition - against the index finger - and this gives you the ability to grip with your hand. Lose this function and you will lose basic skills that you take for granted - like holding a pen, a knife/fork or spoon or undoing buttons on your shirt.
On this page I will describe the thumb joint, the common thumb injuries we see as a result of snow sports, their treatment and some ways to reduce the chances of sustaining a thumb injury whilst skiing, snowboarding or skiboarding.
Anatomy of the thumb joint
The thumb comprises of three bones - the distal phalanx, the proximal phalanx and the metacarpal bone.
The latter forms a join with the trapezium bone in the hand as shown on the right. The thumb also has one very important joint when it comes to snow sports - the metacarpo-phalangeal (MCP) joint. This joint is supported and stabilised on the inside by the all important ulnar collateral ligament - the UCL. It is the MCP joint - and the UCL in particular, that are involved and injured in the classic skiers injury - "skier's thumb".
Current epidemiology of thumb injuries from snow sports
Taking the data from our ongoing study in Scotland, the % of all injuries affecting the thumb joint by snow sport is shown below.
Alpine skiing - 5%
Snowboarding - 3.2%
Skiboarding - 1.1%
Our incidence of thumb injuries from alpine skiing is 5%, which is lower than in some other studies which have quoted thumb injuries to constitute 10-15% of all injuries. You can see that skiing has the highest incidence of thumb injuries and skiboarding (snowblading) the lowest. I will discuss why this might be in the subsequent sections of this page.
Mechanisms of thumb injury from snow sports
If you have read the other pages on this website relating to orthopaedic injuries, you will have learnt that they occur either as a result of direct impact to the area concerned, or from the application of unusual forces (an indirect injury). The thumb joint is no different.
Direct impact injuries
These injuries usually occur as the result of collisions with fence posts, icy surfaces, other 
skiers/boarders etc. Contusions (bruising), lacerations and fractures can all result from this mechanism depending on the exact nature of the force(s) applied. Most of these injuries will heal within a short time frame, although fractures of any area of the thumb need to be treated with a bit of respect. Any such injury will lead to short term disability and the loss of grip in the affected hand. As with fractures elsewhere in the body, the seriousness of the fracture increases depending on the type of injury. As a general rule of thumb (pardon the pun), most undisplaced fractures can be managed in a cast or splint with careful follow up to ensure functional recovery takes place. The following features all signify a significant injury - many will require operative intervention along with careful orthopaedic management and follow up:
- Displaced fractures
- Fracture dislocations
- Compound (open) fractures
- Fractures through the articular (joint) surface
The thumb injuries that snowboarders and skiboarders tend to sustain are direct injuries. Skiboarders are less vulnerable to these than snowboarders because in general they tend to fall onto their upper limbs less often (being able to step out one leg and regain balance which isn't possible on a snowboard)
Indirect injuries
The thumb joint can also be injured by the application of unusual forces across the joint - this is especially so at the MCP joint where the UCL is susceptible to being stretched and injured as a result of the thumb being bent outwards. This mechanism is seen in the injury known as "skiers thumb".
Skier's thumb
This is the number one thumb injury seen amongst skiers and so I am going to devote a bit more attention to it.
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Mechanisms of injury
The main reason for skier's thumb (and hence the reason that the thumb joint is injured more from 
skiing than snowboarding) is the fact that most skiers ski with a thumb pole held in the palm of their hands. Furthermore, most skiers also use the pole straps routinely supplied in order to secure their poles to their wrists so that they don't lose the pole when they fall over.
Unfortunately, a direct result of this is that when the skier does fall onto their hand, the pole handle is sitting in the palm of the hand and can act as a lever across the MCP joint, forcing it into abduction/radial deviation).This tends to apply force across the MCP joint, stretching and damaging the UCL in the process.
It is also possible for skiers to sustain the same injury without falling. In this case, the skier plants their ski pole in the snow but is unable to remove it in time as they move forwards, once again applying damaging force across the MCP joint and the UCL
Snowboarders and skiboarders are far less vulnerable to skier's thumb simply because they don't use ski poles.
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Diagnosis
As with most other snow sports injuries, the clue to diagnosis is in the history of what happened. On examination, there is localised tenderness at the base of the thumb over the MCP joint, specifically over the UCL. There may be associated swelling and bruising. An x-ray is often taken to exclude the presence of an associated fracture (sometimes as the ligament gets pulled with force, it pulls off a small piece of bone as well - known in the trade as an "avulsion fracture"). In the absence of a fracture, the stability of the UCL can be tested by holding the thumb metacarpal steady in one hand whilst with the other hand try to abduct the MCP joint. Ideally this should be done with the thumb fully extended and also in 30 degrees of flexion. If the injury is very sore, some local anaethestic can be injected in first to make it all go nice and numb.
Even in a normal thumb, there is a degree of give felt when stressing the MCP joint this, but it should not be excessive. Depending on the amount of give detected in the injured ligament (and this can be compared to the thumb on the casualty's other hand) the ligament injury can be graded as 1, 2 or 3 in increasing degrees of severity.
- Grade 1 - No laxity ('give') in the ligament when stressed. Few, if any, ligament fibres torn.
- Grade 2 - Some laxity in the ligament, but a definite endpoint is present. Some, but not all, ligament fibres torn
- Grade 3 - Complete give in the ligament. All ligament fibres torn.
To complicate things still further, the UCL itself lies underneath a sheath of fibrous tissue called the adductor aponeurosis (AA). On occasions, when the ligament ruptures, one end of the torn ligament folds back and effectively disappears underneath this fibrous sheath making it impossible for the two ends of the ligament to come back together and heal naturally. This is called a stener lesion and is very important to diagnose as its presence makes surgical repair inevitable (see below)
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Management
The flow chart below summarises my recommended management of skiers thumb.
Wherever possible, functional splinting is preferred to a rigid cast.
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Prevention
Unfortunately, no one technique or piece of equipment has ever been shown conclusively to protect against skier's thumb.
Pole handles
Several ski pole handles have been designed over the years to try and address this problem - I'm not sure how many are still commercially available but certainly you don't see them in the shops very much. Looking at some of the designs, they do make sense but I am not aware of any research that shows them to be effective - contact me if you know any different!
Perhaps the best chance of avoiding skier's thumb for most skiers is a combination of being aware of its potential and also using ski pole straps properly. The video clip below describes the correct way to use pole straps to minimise the risks of the pole being in the wrong position at the wrong time.
How to Use Ski Poles -- powered by ExpertVillage.com
Another option is of course to not use the pole straps at all. This might not be a bad option when skiing recreationally on piste, but there is of course a risk that you will drop and lose your pole and/or injure yourself or someone else with it. The risk of loss increases in deep powder snow - a situation where ski poles are actually very helpful. If skiing off piste, poles can be very important if you are caught in an avalanche when they can help you to "swim" to keep close to the surface of the slide.
References
1 Berger C, Holzach P, Matter P. [Skier's thumb injury in the child]. Helv Chir Acta 1994; 60(4):615-621.
2 Campbell JD, Feagin JA, King P, Lambert KL, Cunningham R. Ulnar collateral ligament injury of the thumb. Treatment with glove spica cast. Am J Sports Med 1992; 20(1):29-30.
3 Davies MB, Wright JE, Edwards MS. True skier's thumb in childhood. Injury 2002; 33(2):186-187.
4 Demirel M, Turhan E, Dereboy F, Akgun R, Ozturk A. Surgical treatment of skier's thumb injuries: case report and review of the literature. Mt Sinai J Med 2006; 73(5):818-821.
5 Heim D. The skier's thumb. Acta Orthop Belg 1999; 65(4):440-446.
6 Hergan K, Mittler C. Sonography of the injured ulnar collateral ligament of the thumb. J Bone Joint Surg Br 1995; 77(1):77-83.
7 Hintermann B. [Skier's thumb--osseous injury and rupture of the ulnar collateral ligament]. Z Unfallchir Versicherungsmed 1993; Suppl 1:232-41.:232-241.
8 Hintermann B, Holzach PJ, Schutz M, Matter P. Skier's thumb--the significance of bony injuries. Am J Sports Med 1993; 21(6):800-804.
9 Hoglund M, Tordai P, Muren C. Diagnosis by ultrasound of dislocated ulnar collateral ligament of the thumb. Acta Radiol 1995; 36(6):620-625.
10 Hoogewoud HM. Skier's thumb--the significance of bony injuries. Am J Sports Med 1994; 22(3):433.
11 Noszian IM, Dinkhauser LM, Orthner E, Straub GM, Csanady M. Ulnar collateral ligament: differentiation of displaced and nondisplaced tears with US. Radiology 1995; 194(1):61-63.
12 Primiano GA. Skiers' thumb injuries associated with flared ski pole handles. Am J Sports Med 1985; 13(6):425-427.
13 Roh M, Weiss AP, Akelman E. Skier's thumb: a review. R I Med 1994; 77(11):385-386.
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