70.4 Catastrophes with casts

Two disasters can befall the circulation of an injured limb. An unwisely applied cast can cause both of them: (1) If its circulation is completely obstructed, the limb becomes gangrenous, so that all its tissues die, including the skin. (2) If pressure builds up in a tight space, such as a fascial space, the compartment syndrome may develop, followed by Volkmann’s ischaemic constructure.

Figure 70.3: SOME PREVENTABLE DISASTERS. A, a pressure sore. B, Volkmann’s ischaemic contracture of the hand. C, Volkmann’s ischaemic contracture of the leg.

The compartment syndrome is caused by the partially ischaemic muscle swelling, squeezing out its own blood supply becoming hard and partly necrotic, and then slowly fibrosing over several months. As it does so, it strangles the vessels and nerves of the limb. The patient’s skin remains intact, and although its nutrition may be impaired later, it does not become gangrenous. Volkmann’s ischaemic contracture is the final result. This is usually an anaesthetic, crippled, clawed, forearm. But it can also be an ankle in extreme equinus, with flexion of its midtarsal joint and dorsiflexion of its MP joints and toes. Volkmann’s contracture is one of the ultimate orthopaedic disasters, because it cripples for life, it cannot be adequately treated, and it is almost always preventable!

In its less extreme forms Volkmann’s ischaemic contracture is more common than most people think. It may only show itself later as a stiff foot, or a very stiff hand that gradually begins to develop severe contractures during the months that follow the injury.

A patient’s forearm muscles are most commonly involved by Volkmann’s ischaemic contracture, and occasionally the muscles of his lower leg, but never by the muscles of his upper arm, or his thigh, which are less firmly enclosed in fascia. Usually, the tight fascia of his forearm or leg is enough to restrain the swollen tissues and start the syndrome, but a tight bandage (including an Esmarch bandage), or a tourniquet, or gallows (78.2) or extension traction (78.3), or an unsplit cast can all precipitate it. Although a layer of cotton wool between a patient’s skin and the cast reduces the risk, any cast all round a limb is a potential source of disaster. Most cases occur in the forearm of children following forearm fractures or supracondylar fractures (72.8). Some follow fractures of the tibia (81.14), and a few follow injuries to the thenar muscles, or dislocations of the elbow (72.4) or knee (79 .8). Occasionally in adults, and very rarely in children, there is sot tissue injury only with no fracture.

Correct management will usually prevent ischaemia, but always be watchful for the early signs (55.3); these are pain, paraesthesiae, pallor, and paralysis. The presence of a peripheral pulse does not exclude the compartment syndrome. The critical symptoms are the patient’s inability to use the muscles of his limb, and pain. The ordinary pain of an immobilized fracture is moderate and improves. Ischaemic pain is more severe and gets worse during the first few hours after an injury. Pain after 48 hours is more likely to be caused by infection.

A well applied circular cast should reduce the pain of a fracture. If a patient, especially a child, complains of pain, take his complaints seriously, it is probably due to: (1) pressure on a bony point which may only subside as his skin erodes away, or (2) ischaemic pain which you must relieve. Pain is not an indication for aspirin or pethidine, it is an indication to find out why there is pain, and to split, window or renew the cast. So, never apply a circular cast to a patient who is unconscious from other injuries, and so unable to complain of pain. He may develop the compartment syndrome only too easily.

SHANTI (8 years) had an undisplaced fracture of the distal end of her radius. There was almost no swelling. A circular cast was applied. She returned the next day crying in pain. She was given aspirin and sent home. Three days later she returned with a gangrenous hand and sloughing forearm muscles. Her forearm was amputated. LESSONS (1) An undisplaced forearm fracture does not require a circular cast; all she needed was a slab and a crepe bandage. (2) Never treat a painful cast with analgesics only. (3 If you apply a circular cast, ALWAYS split it. (4) Pain, numbness, and paralysis are signs of impending Volkmann’s ischaemic contracture.

ABDULLAH (8 years) had a supracondylar fracture. It was successfully reduced within an hour and a skin tight cast was applied. He returned the following day saying that his fingers hurt, but was sent home without removal of the cast. Five days later he returned again. This time all his fingers and thumb were black and gangrenous, and had to be amputated. LESSONS (1) A cast is not the treatment for this fracture. (2) Don’t apply a skin tight cast immediately after an injury, before the limb has had time to swell—wait at least 12 hours. (3) Take any complaint of pain seriously and split or remove the cast immediately.

VOLKMANN’S CONTRACTURE—A PREVENTABLE CATASTROPHE

Use procedures, particularly slabs and a crêpe bandage or a split cast, which will make the syndrome less likely.

Identify the patients at particular risk and examine them frequently. Record your findings carefully, and note at what time you made them.

Watch for pain, paraesthesiae, pallor, and finally paralysis, and teach your staff to do the same.

Check the sensation of the nerves in the involved area using two point discrimination, or a pin. In injuries of the forearm, test for pain on passive extension of the fingers. Test the strength of all involved muscles. Feel the compartment for tenderness and tenseness.

CAUTION! Remember that a normal pulse does not exclude the compartment syndrome.