Handlebar Palsy

 Physiotherapist Tim Bickerton looks at hand injuries in cycling, analysing the symptoms and suggesting some good ways to prevent painful and debilitating problems.

A regular complaint from cyclists is that their hands feel weakness, clumsiness, cramping and pins and needles after a long ride. These symptoms often indicate a condition known as handlebar palsy, a nerve compression syndrome in the hand caused by bearing weight on the handlebars.

Handlebar palsy effects both MTB and road cyclists. This condition was first described in cyclists by researches as early as 1896. More recently studies of the injury’s occurrence in long-distance cyclists have found that symptoms of nerve compression prevalence are as high as 70% (Dettori and Norvell). The term palsy has been regularly used to describe this condition because the riders’ hand develops muscle paralysis. Handlebar palsy particularly refers to the loss of muscle function in the hand.

Interestingly, cyclists who experience handlebar palsy may be unaware they are causing significant nerve damage until a severe nerve lesion develops. This is because easily recognisable symptoms of numbness, pins and needles and pain may not always accompany other less distinguishable symptoms, such as hand weakness and loss of dexterity (Capitani and Beer).

Anatomy

The ulnar and median nerves of the hand and wrist are potential areas for compression in cyclists. In general terms, a nerve is essentially the electrical conduit of the body that stimulates muscles to move and allows us to sense our environment.

If you were to follow the path of the ulnar and median nerves from their origin in the cervical spine (neck) to the tips of the fingers you would find the nerves pass through many passages of potential compression.

When the ulnar and median nerves arrive at the wrist, they have already stimulated many muscles and skin of the forearm; they then take passage through the small tunnels of the wrist, allowing muscle function and sensation in the hand.

The ulnar and median nerves take two distinct pathways through the wrist. The median nerve passes centrally through the carpal tunnel; a space created by small bones and dense overlying soft tissue at the wrist. The ulnar nerve passes over the carpal tunnel closer to the skin (Figure 1).

The ulnar nerve, being closer to the skin and having less protection from the carpal bones, is more susceptible to external compressive forces in this area. Although the ulnar nerve is indeed vulnerable as it crosses the wrist, the most common area of compressive damage of the ulnar nerve in the cyclists occurs at, or just before, an area known as the Guyon’s canal where the ulnar nerve splits in two (Figure 1).

This may be due to the fact that the opening of the canal is narrow, predisposing it to mechanical damage at this point.

One branch of the ulnar nerve supplies the skin on the inside of the hand, all of the little finger, and half of the ring finger. The second nerve branch is known as the muscular branch (stimulates muscle). This muscular branch supplies the deep muscles that lie between the bones of your palm. These muscles are integral for most hand activities, including gripping, hand writing and playing the piano. Damage to the muscular branch leaves paralysis, atrophy and weakness of the hand without numbness.

Ulnar Nerve Compression Types (Capitani and Beer)

Damage to a nerve can happen in two ways; either the nerve conducting portion may be damaged (axonotmesis), or the insulation around the nerve is damaged (neuropraxia). Both ways affect hand function. Pictured in Figure 1 are possible sites of ulnar nerve damage. The site of damage is accurately diagnosed from their associated signs and symptoms detailed below.

Type 1: Ulnar nerve compression at the entrance into the Guyon’s canal

• Numbness and pins and needles on the inside of the hand, little finger and half of the ring finger.
• Weakness, clumsiness, and cramping in the hand and muscle wasting in the back of the hand.

Type 2 and 3: Ulnar nerve compression at the exit of Guyon’s canal and effects the muscular branch only (Handlebar Palsy).

• Weakness, clumsiness and cramping in the hand and muscle wasting in the back of the hand, no altered sensation so the cyclist may be unaware of nerve damage.

Type 4: Compression of sensory nerve fibres only

• Numbness and pins and needles on inside of the hand, little finger and half of ring finger.

Mechanism of Injury

As the palm of your hand rests on the handlebars or grips, a potential site for nerve compression is established. The distribution of your body weight conceded through the bars determines the amount of compression experienced. If a nerve is compressed for a long period of time it results in an inability to send electrical signals to the muscle, and the muscle becomes weak.

Usually it takes many hours of riding for the nerve to be compressed and damaged. However, some have found that a single day of mountain bike riding, in particular down hilling, can cause sufficient compression to the ulnar nerve (Capitani and Beer).

This acute onset is due to a large proportion of the rider’s body weight being supported by the hand on the corner of the handlebar during down hill off-road cycling. Therefore, the contact point, weight distribution and contact surface are the three fundamental factors affecting handlebar palsy (Figure 3).

Other proposed contributing factors are prolonged wrist extension, general body fatigue (causing increased hand weight bearing), surface vibration, handlebar reach too long, shape of handlebars, inadequate suspension, worn handlebar padding/grips and worn gloves (Patterson, et al, Dettori and Novell).

Prevention Strategies

Cyclists who believe they are at risk of suffering from handlebar palsy should first consult their professional bike fitter. All adjustable variables of the bike fit should be reviewed and attuned if necessary. The most important variables are seat height, reach and handlebar height where erroneous positions may contribute to increased hand bearing weight.

The main goal of the bike-fit review is to reduce the amount of hand bearing weight. The result of this should be that the rider has not more than a gentle pressure through the hands on the bars. Following the review the cyclist should now be comfortably postured on their bike and the proceeding approaches should also be exhausted:

• Handlebar tape/grips have adequate cushioning
• Gloves are used and also have adequate cushioning
• Regularly change hand position on bars (Figures 5 to 7)

As well as the above, the enthusiastic cyclist should also adopt a comfortable and resilient riding posture. This is perhaps more important for the long-distance cyclists’, because flaws in postures are grounds for early onset of fatigue in the trunk. If the trunk becomes tired the hands will invariably bear more weight to stabilise you on the bike.

Developing a better posture on the bike requires good trunk muscle endurance and may take many months to develop. The process should be facilitated by a trained observer, such as a coach. It should be an individualised approach and incorporate ideas of ‘core’ stability as we covered in the Mar/Apr 2007 edition of Bicycling Australia.

Prognosis

The length of time from initial injury to full recovery is variable and depends upon the extent of nerve damage. In general, nerves grow back at approximately 1-2mm per day. Given all aggravating factors have been removed, a full recovery for the ulnar nerve in the hand should occur between six to eight weeks.

Treatment

The main goal of treatment is to encourage normal healing of the ulnar nerve. Therefore, rest from aggravating activities (compression) is strongly advised. A period of time off the bike is recommended for both healing and safety reasons.

During the rehabilitation process a physiotherapist may be required to retrain and strengthen the deep hand muscles. Pictured in Figures 8 to 11 are examples of exercises that a physiotherapist may prescribe. This group of exercises will assist in retraining and strengthening the hand muscles affected by handlebar palsy.

1. Place the hand palm down on a table, move the fingers apart keeping the hand still, repeat 10 times (Figure 8).
2. Hold the hand on the side, bend your fingers so that you also cup the palm and touch finger tips near to the wrist, repeat 10 times (Figure 9).
3. Place a pen between your fingers and squeeze 10 x 5 second holds (Figure 10).
4. Hold the hand on the side, bend the fingers where they join with the palm while keeping the fingers straight and the palm still, and repeat 10 times (Figure 11).

The above exercises are good examples only and you should be guided by your physiotherapist.

References:

• Capitani, D. and Beer, S. (2002). Handlebar Palsy – a compression syndrome of the deep terminal (motor) branch of the ulnar nerve in biking. Journal of Neurology. 249; pp 1441-1445.
• Patterson, M., Jaggars, M, Boyer, M. (2003). Ulnar and Median Nerve Palsy in Long-distance Cyclists. The American Journal Of Sports Medicine. 31 (4) pp 85-589.
• Dettori, N. and Norvell, D. (2006). Non-Traumatic Bicycle Injuries – A Review of the Literature. Sports Med. 36 (1) pp 7-18.
• Snell, R.S. Clinical Neuroanatomy for Medical Students Fifth Edition. LippinCott Williams and Wilkins. Baltimore (2001).

Image: Cor Vos