Pott's Fracture (Ankle)

There are 3 degrees of Pott's fracture:

• First degree. There is an isolated fracture of the medial malleolus. The characteristic feature is that the fracture line is vertical at the base of the medial malleolus with no ligament involved. This presents itself as deformity and tenderness over the medial malleolus only.
• Second degree. The characteristic feature is that in addition to a vertical fracture there is a transverse fracture of the lateral malleolus with inward displacement of the foot. There is tenderness over both medial and lateral sides of the ankle with ligament damage.
• Third degree. In addition to the above, there is a posterior fracture of the tibia with posterior dislocation of the foot. The foot appears displaced from the side. In extreme degrees of abduction or adduction force, the skin over the tendon is stretched and may rupture to cause an open injury exposing the ankle joint. If the skin is broken it is a compound fracture.

Fracture of distal fibula with possible displacement of tibia is discussed in ankle injuries.

It is commonest amongst young adults, especially if involved in extreme or contact sports. It also occurs in older people but is unusual in children, who usually have a fracture through the growth plate. There is a male preponderance of 2:1 but women over 40 have the highest incidence of fracture dislocations.

• It is usually an inversion injury of the ankle but may be caused by forced eversion.
• It often results from sporting injuries, falls or road traffic accidents.
• The direction of the force will produce fractures of varying degrees which may also include damage to ligaments.
• If the force is great, the ankle joint may be dislocated because there is no medial support from the malleolus.
• Fibula may fracture distally if the ankle joint dislocates.

History

• There will be a history of injury to the ankle, usually with forced inversion of the ankle.
• Walking will be very painful or, more often impossible because of pain.
• The sound of a crack on injury does not mean that there is necessarily a fracture.¹

Examination

• There will be tenderness, swelling and possibly bruising around the affected area. It is difficult to distinguish between a fracture and a moderate or severe sprain of the ligaments.
• Palpate along the lower border of both tibia and fibula and the posterior aspect of the joint.
• Assess range of both active and passive movement.
• The ankle joint may be unstable.
• Check the integrity of nerves and arteries of the foot.

Clinically it may be very difficult to differentiate a fracture from a severe sprain without an x-ray unless there is obvious distortion or instability. The Ottawa rules² were introduced in 1992 to reduce the number of unnecessary x-rays whilst at the same time minimising the number of fractures missed. Whilst not absolutely perfect they do have a great deal of respect and if a clinician applies the Ottawa rules, it is a safe and validated way to proceed. Getting x-rays of every injured ankle will have a yield of less than 15%.

The original work has been reproduced elsewhere and analysed by meta-analysis³ and systematic review⁴ and it confirms a specificity of around 100% but a sensitivity of about 30 to 40% for fractures of the ankle. This should still produce a considerable reduction in the number of negative x-rays whilst failing to x-ray very few if any fractures.

The Ottawa rules apply not just to Pott's fractures but to fractures of the forefoot too. They have also been validated in children⁵ and within a university sports medicine environment.⁶

Ottawa rules

• Can the patient walk 4 steps immediately after the injury or when seen as an emergency?
• Check for localised tenderness at specific sites. These are the posterior edge or tip of both malleoli, the navicular, and the base of the fifth metatarsal.

If the patient could walk 4 steps and there is no local tenderness at the specified sites, it is safe to omit x-ray.

Unless the Ottawa rules apply, x-ray is required, both PA and lateral. It may be necessary to x-ray in a stressed position such as attempted inversion to show any distraction. If the ankle joint appears intact a positive stress test does not mean that operation is required.⁷

Non-Drug

• Simple fracture requires analgesia, splint, walking cast, stirrup or brace. Apply the principles of RICER as for soft tissue injuries.
• Crutches will be needed for mobility.
• Displaced fractures require reduction and immobilisation in a plaster cast from below knee to toe for 6 weeks, after the swelling subsides.
• In second and third degree fractures manipulative reduction with or without screw fixation is done under general anaesthesia. The ankle is in plaster with no weight bearing for 4 to 6 weeks after which a second plaster cast is applied to the foot in a neutral position and the patient can partially weight bear.
• After completing the period of immobilisation the patient will begin ankle rehabilitation with physiotherapy.
• The aim of physiotherapy is to restore range of movement to as full as possible, and to use the crutch to assist ambulation.
• When full range of movement is achieved, active exercises are performed including static cycling and weight bearing exercises, moving to proprioception exercises and functional exercises.
• When performing rehabilitation exercises or returning to sport added ankle protection is advised until full strength is regained.
• In second and third degree fractures, patients do active toe exercises and quadriceps exercises while in plaster. On removal of plaster oedema of the leg can be prevented by elastic bandaging and active exercises to mobilise the ankle and improve muscle and vasomotor tone in the leg.

Drugs

NSAIDs are the drug of choice to help with pain and assist with rehabilitation but opiates may be required in the acute condition.

Surgical

• If the fracture is displaced it may need to be reduced under anaesthetic.
• If the joint is unstable operative fixation is required with screws and plates.
• Recent advances include the use of biodegradable implants⁸ that do not need to be removed at a later date.

• Ligament instability may require taping or bracing for all future sporting activities
• Long-term joint stiffness may occur.
• Orthopaedic intervention is required if there is malunion of the medial malleolus as it may result in osteoarthritis or chronic pain. Fixation is required.
• Children tend to get fracture of the growth plate. This is classified according to the Salter-Harris system.

• Good, depending on degree of soft tissue injury and severity of the fracture. The degree of dorsiflexion of the ankle at the time of removal of the cast and fracture classification are clinically significant predictors of outcome but there is still much unexplained variation in outcomes.⁹
• For isolated fibula fractures the prognosis is good.
• Upon retuning to sport, added ankle protection is required such as taping or brace.

Percival Pott (not Potts) was born in London in 1716. Having initially been destined for the clergy, he changed his mind and was apprentice to a surgeon at St Bartholomew's Hospital. He was granted the Grand Diploma by the Company of Barber-Surgeons at the age of 22. He developed a private practice and in 1745 he became assistant-surgeon and in 1749 full surgeon at St. Bartholomew's Hospital, remaining there until his retirement in 1787. One cold January morning in 1756, he was making house calls when he was thrown from his horse and sustained an open compound fracture of lower tibia and fibula. He did not accept advice from colleagues who advocated immediate amputation but he had a lengthy convalescence. Whilst immobile he did much writing including describing the management of fractures, including the one that so justly bears his name. In 1788, having caught a cold whilst out visiting patients, he died of pneumonia.

Conditions that bear his name include:

• Pott's aneurysm that is an arteriovenous aneurysm.
• Pott's cancer is a coal tar-induced cancer of the skin that he noted was common on the scrotum of chimney sweeps.
• Pott's disease and the resulting Pott's curvature and Pott's paraplegia.
• Pott's fracture.
• Pott's gangrene is an eponym for mortification of toes and feet due to arterial obstruction in the aged.
• Pott's puffy tumour is a circumscribed oedema of the scalp associated with underlying osteomyelitis of the skull.