Arm Pump – Chronic exertional compartment syndrome (CECS)

 

Overview

Arm pump is a compartment syndrome overuse type injury. In that respect it is quite unusual in motorcycle racing, as the majority of injuries are traumatic in nature. It seems to be more commonplace in motocross, yet the list of Motogp riders who have suffered from this complaint includes:

Toni Elias, Sylvain Guintoli, Nicky Hayden, Chris Vermuelen, John Hopkins, Makoto Tamada, Marco Melandri and Kenny Roberts jnr.

It exists due to the complex coordination necessary at the hands and wrists required to control a high powered motorcycle.

It must be differentiated from Acute compartment syndrome (where symptoms do not go away with rest), which is a normally caused by injury and is a true emergency. There may be permanent muscle damage in acute compartment syndrome unless surgically treated in less than six hours. It has been discovered when testing canine muscle that fewer than 5% of muscle cells were damaged after 4 hours of ischemia, while nearly 100% of muscle cells were damaged after 8 hours of ischemia.

When you grip something in your hand there is co-contraction between the muscle groups on the back (dorsal) and front (volar) of the forearm. To necessitate a stronger grip the wrist is pulled into extension. This co-contraction results in an increase in compartment pressure, ie. It is harder for the blood to flow through this region.

Thus to simply grip a handlebar increases pressure. To grip the handlebar of a rapidly accelerating or decelerating motorcycle necessitates stronger grip levels. If you then add the throttle action, which uses the dorsal wrist extensors more than the volar wrist flexors, then the clutch and brake levers, which use the volar finger flexors, then the complex nature of this injury starts to appear.

If you then factor in a “technical” circuit with repeated braking from high speeds followed by lots braking zones, lots of direction changes, short periods of acceleration, it becomes clear that the forearms do not get a lot of rest per lap.  Circuits such as Mugello with their long straights at least afford a period of rest from repetitive lever use.

Ergonomics are extremely important with this type of injury, hence handlebar and lever position are crucial. As are lever pressures (carbon discs = lower lever pressure for a given braking force), short travel throttles and so on.

 

Pathophysiology 

Muscles are held in fascial sheaths. Fascia is a tough, but thin, white gristle that envelops the compartment like a casing wraps a sausage. Fascia helps to anchor muscles and give them form. Fascia is very strong, but it is not very elastic. The inelasticity of fascia surrounding muscle means that even small increases in the volume of a fascial compartment can cause large pressure increases within the compartment. When subjected to continuous exercise muscle becomes engorged with blood and can increase it's cross sectional area by upto 20%.

The engorged muscle is encased inside the inelastic fascia and, as it grows, the pressure within the fascia compartment increases. Although gases and solids are compressible, fluids are not. The incompressible fluid within the inelastic fascia makes the forearm feel hard as rock.

If the "compartment pressure" rises high enough, blood vessels can collapse, which restricts or stops the flow through that vessel. Veins, with their low pressure and thin walls, collapse earlier than high-pressure, thick-walled arteries. When venous flow reduces, arterial blood continues to enter the fascial compartment but is restricted from leaving (venous congestion). This restricted outflow further increases the pressure within the fascia compartment. If the compartment pressure rises higher than the pressure in the capillaries, or even the arteries, then these vessels may collapse, resulting in "muscle ischemia"-a painful condition of oxygen deprivation.

When the activity is stopped, the pressures gradually dissipate and the symptoms resolve, unlike as previously stated Acute Compartment Syndrome which does not.

 fig.1

  

This figure shows a cross section through of a left forearm.

 The compartments are labeled anterior (volar), posterior (dorsal) and the mobile WAD*.

 If you horizontally split the figure above; the top half would be the anterior (volar) compartment, and the lower half the posterior (dorsal) compartment.

 The posterior compartment contains those muscles which extend the wrist and fingers, and is innervated by the Radial nerve.

 The anterior compartment contains the muscles which flex the wrist and fingers,and is innervated mainly by the median nerve.

 NB. It is important to realize that both the Radial and Median nerves originate from the nerve roots C5 C6 C7 C8 & T1, hence a neck injury may well refer pain into these areas.

 Objective criteria for the diagnosis of chronic compartment syndrome are:

·        resting compartment pressures of 15 mm Hg or higher

·        1-minute post-exercise pressures of 30 mm Hg or higher

·        5-minute post-exercise pressures of 20 mm Hg or higher

 *(Mobile WAD is a collective term for the lateral muscles brachioradialis, extensor carpi radialis brevis & extensor carpi radialis longus). 

 

Symptoms

There is usually pain out of proportion to the injury, tenseness of the forearm, swelling, and pain with passive movement of the compartment musculature. The patient generally has good capillary refill* and a palpable radial pulse.

If the volar compartment is involved, there may be paresthesias and altered sensation over the palm and the volar aspect of the thumb and index, middle, and ring fingers. The small finger is usually less affected than the others, because the ulnar nerve is less dramatically affected than the median nerve. The thumb and fingers will often be held in the flexed position. Elbow flexion and extension are painful, but are better tolerated than finger or wrist movement.

When the dorsal compartment is involved, sensation to the hand and fingers is usually normal, because the posterior interosseous nerve has no sensory component. There often is weakness of thumb, finger, and wrist extension. The hand and wrist are generally held in extension. Flexing the fingers causes excruciating pain.

When compartment syndrome affects the mobile wad*, there can be altered sensation over the dorsum of the hand. There may also be weak wrist extension. Elbow and wrist motion flexion is very painful. Finger flexion is better tolerated than elbow or wrist movement.

*Capillary refill is the rate at which blood refills empty capillaries. It can be measured by pressing a fingernail until it turns white, and taking note of the time needed for color to return once the nail is released. Normal refill time is less than 2 seconds

   

Treatment

Surgical release of the forearm fascia (fasciotomy) is easily performed by an Orthopedic Surgeon. Fasciotomy is not a new or difficult procedure, and is more commonly performed in the leg than the forearm. It is commonly performed in trauma patients to treat or prevent acute compartment syndrome

 By cutting the skin and then slicing the muscle's fascia (or actually removing a strip of fascia) the gristle-like compartment is opened up. This gives the muscles of the forearm room to expand.
Your forearm has four fascial compartments, and it takes two incisions to release all four. The first is a volar incision to release the superficial and deep volar compartments. The second cut is a dorsal incision to release the dorsal and mobile wad compartments.
The use of forearm fasciotomy for arm pump is very poorly documented in the medical literature. In the few studies that have been written up, the authors contradict one another on several points, including what constitutes abnormal compartment pressures and which compartments should be released.

In the forearm there is good evidence showing that compartments are often interconnected and effective release can be accomplished by releasing just the volar compartments.

Typically the operation can be done as an out-patient procedure (no need for an overnight stay). A cast isn't necessary and recovery time is brief. Training can start about two to three weeks after surgery, and a rider can return to competition in four to six weeks.

 Physiotherapy management of recovery should optimize the result of the surgical procedure and reduce the chance of recurrence.

  

Physiotherapy Management

Conservative Physiotherapy management should be comprehensive and specifically include:

  • A review of the riders general physical condition and the various aspects of their fitness regimes
  • A review of upper limb & spinal biomechanics, movement patterns and subsequent muscle imbalances
  • A review of on-bike ergonomics

 Post-operative management should fundamentally mirror conservative care, except for management of the healing (scarring) process.

Treatment can include, manipulative therapy, myofascial release, soft tissue massage, neural mobilization, exercise to lengthen / shorten appropriate muscle groups, and biomechanical rehab. Ultrasound may initially be a useful adjunct to treatment.

The ultimate aim is to facilitate more normal function of the forearm musculature in response to physical activity, and ensure that appropriate fitness activities are being undertaken in the long run.

  

Top tips

1.      Stay balanced, try to position your body weight so that the bike pushes you, rather than pulling you.  Practice shifting your weight forward during acceleration, and shifting your weight back during braking. The main idea is to minimize the demands on your hands and teach you to keep your weight balanced.

2.      It's all in the legs. Squeeze and maneuver the bike with your legs

3.      Relax your grip, your arms, and your hands, and take a deep breath when you can.

4.      Keep your equipment in check
You don't want your equipment to make you work harder than you need to, so be sure your suspension is properly setup. Bar position, lever position, grip compound should also be fine-tuned and individualized. You may find that you can stay more relaxed with your bars more forward, back, etc.

5.      Get your blood flowing
Warm up before you go out on track. A quick jog through the pits or some other exercises to get your blood flowing will encourage circulation through the arms.

6.      Stay hydrated

7.      Breath!
Forgetting to breath while riding as silly as it may sound is among the most common causes of arm pump in beginner-level riders. Paying attention to your breathing will also help you relax.

8.      Emphasize wrist curls with light weights and high repetitions, rather than heavier weights and low repetitions.