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DIFFERENTIAL DIAGNOSIS
INJURIES TO THE FOOT IN ENDURANCE SPORT
By Nat Padhiar, MSc FCPod (surg)
In endurance sport there are both extrinsic and intrinsic fac- tors that can lead to an injury. Extrinsic factors include train- ing programmes, shoes, training surface, distance and first time runners. Intrinsic factors include biomechanical factors such as excessive pronation or supination and age. Statistics show that first time marathon runners aged between 18 to 26 years of age have a higher incidence of injury. This may relate to over enthusiasm and poor preparation. Veteran runners (>40years) have a lower incidence of injury.
Differential diagnosis
1. MORTON’S METATARSALGIA Also known as Morton’s digital neuralgia, Morton’s neuroma, Morton’s syndrome and lesser metatarsalgia. The condition was first described by Lewis Durlacher in 1845 but gained interna- tional recognition in 1876 when a vivid account was given by Thomas Morton and by Betts in 1940.
Clinical picture The condition is more common in females than males (5:1) with age ranging from 18-50 years. The pain and discomfort occurs mainly in the middle three toes, most commonly in the 3rd and 4th intermetatarsal space (IMS) (Fig.1). Pain in and around all three toes may indicate a double lesion. It is rarely seen between the 1st/2nd and 4th/5th intermetatarsal space.
Injury statistics from the last Glasgow marathon revealed that 60.1% of all the registered injuries occurred in the foot. These were divided as follows: ● nail injuries - 32.7% ● blisters - 16.1% ● musculoskeletal aspect of the foot - 11.3%
In addition, the next most common injuries involved: ● Achilles - 6.1% ● knee - 19.4% ● muscle injuries - 8.1%
Reproduced with permission from Sports Injuries - Their prevention and treatment
Figure 2: Compression of the interdigital nerve (Morton’s syndrome) 1st metatarsal
Extensor hallucis longus
Tibialis anterior
3rd & 4th inter- metatarsal space
5th metatarsal
Extensor digito- rum longus
Talus
Tendons of peroneus longus and brevis
Peroneal retinaculum
©1999 Primal Pictures Ltd Figure 1: Anatomy of the dorsal aspect of the foot (superficial view)
Some graphic descriptions include, ‘hot poker through the foot’, ‘stone in the shoe’, ‘bad toothache’ and ‘burning toes’. The pain occurs mainly on weightbearing and in narrow shoes. Relief is achieved by rest and reducing the compression of the forefoot. Often there is history of paraesthesia and numbness of the corre- sponding toes. Referred pain proximally may indicate low back (lumbar) involvement. The cause of pain/discomfort is usually compression of the plantar interdigital nerve (Fig.2). Histologically, the neurovascular bundle is symmetrical and fusiform in shape. Clinically pain can be reproduced by compres- sion of the foot (Fig.2), often accompanied by a click (Mulder’s click).
Investigations ● A high resolution ultrasound scan is the investigation of choice, however variation in reporting does exist and may be dependent on the experience and skill of the radiologist ● Gadolinium enhanced MRI may prove useful in a situation where there is doubt about the diagnosis and other structures are suspected eg. intermetatarsal bursitis, Schwannoma
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