Disorders of the forefoot and toes

The forefoot

Short first metatarsal bone

This is known as Morton’s syndrome. Sometimes a short first metatarsal is related to pain, sometimes it is not. If the first metatarsal is too short and hypermobile, most of the body weight will be borne by the second metatarsal. Because of the hypermobility and shortening, the transverse arch becomes depressed and metatarsalgia results (p. e308 of this chapter).

This condition was first described in 1855 by Breithaupt,¹ a Prussian military doctor, who stated that many soldiers developed painful swellings at the dorsum of their feet after long marches. He called this Schwellfuss but the cause remained unclear until Stechow² proved that the condition is caused by stress fracture.

Stress fractures of the metatarsal bones comprise 3.7% of all sport-related injuries, with the second and third metatarsal accounting for 80–90% of the fractures.3–5 Stress fractures of the metatarsals are also common in military recruits and in long-distance runners. It has been reported that up to 20% of stress fractures in athletes⁶ and 23% of stress fractures in military recruits⁷ are located in the metatarsals.

The lesion should be suspected when a patient presents with unilateral and localized warmth and oedema at the dorsum of the foot. Often the symptoms appear after a long walk but sometimes there is no specific precipitating activity. It is surprising that children are almost as liable to marching fractures as adults. Cyriax’s ⁸ (his p. 440) youngest patient was a 6-year-old boy.

During the first weeks after the onset of pain, there is local warmth and oedema over the dorsum of the forefoot. The normal findings on functional examination of the ankle and midfoot contrast with tenderness at the forefoot. Because not only the bone but also the interosseous muscles at both sides are involved, the tenderness is more extensive than might be expected from the fracture itself.

During the first few days, the fracture (usually a hair-line crack) may not be revealed by routine radiography. The diagnosis is confirmed after a few weeks, when the callus formation around the fracture becomes radiologically apparent. Earlier confirmation of the diagnosis is obtainable by either radionuclide bone imaging,9,10 or ultrasound examination.^11–13

The true Jones fracture is defined as an acute fracture at the junction between the proximal diaphysis and metaphysis of the fifth metatarsal without distal extension beyond the fourth to fifth intermetatarsal articulation.¹⁴ The mechanism of injury is believed to be an abduction force applied to the forefoot with simultaneous ankle plantar flexion.¹⁵ A Jones fracture can be treated with 6 to 8 weeks of non-weight-bearing immobilization resulting in fair to good outcomes.^16,17 Operative treatment is selected if the patient is a high-performance athlete or nonoperative treatment fails.¹⁸

A proximal diaphyseal fifth metatarsal stress fracture is defined as a stress fracture in the zone of the proximal fifth metatarsal immediately distal to the Jones fracture’s anatomic area.¹⁹ The mechanism of this injury is believed to be a repetitive load applied under the metatarsal head over a relatively short time, resulting in an overuse phenomenon. A proximal diaphyseal fifth metatarsal fracture may have a very long healing time and non-union can develop in as much as 25% of cases. For this reason, operative treatment is usually recommended.²⁰

Splay foot

A splay foot is a broadened forefoot, with weakness of the intermetatarsal ligaments, associated with weakness of the intrinsic muscles.

Very often splay foot starts with excessive dorsiflexion movement of Lisfranc’s joint, which occurs when too much weight falls on the midfoot. This is particularly likely to occur in women who wear high heels. When excessive weight falls on the midfoot, the talus is pressed downwards, and the metatarsals undergo an upwards pressure, so that they are given excessive horizontal play and the transverse arch flattens. The result is a painful overstretching of the transverse interosseus ligament and an increase in weight on the middle metatarsal heads. Calluses will form on the plantar surfaces of the heads and bruising of the plantar aspect of the capsule of the metatarsophalangeal joints (so-called chronic metatarsalgia) results. In practice, splay foot is not a specific entity but usually accompanies a midtarsal strain.

Treatment includes a high heel with a horizontal upper surface, which prevents the forwards gliding of the talus and thus releases the forefoot (see Ch. 59), and energetic training of the short plantiflexor muscles of the toes.

Localized splaying indicates a ganglion lying between two metatarsal heads. When the patient stands, an excessive interval is seen between two toes and palpation reveals a semisolid tumour keeping the heads apart (see p. e309 of this chapter).

The first metatarsophalangeal joint

The capsule of the first metatarsophalangeal joint is reinforced on the plantar surface by a fibrocartilaginous plate that is attached distally to the proximal phalanx and proximally to the plantar aspect of the neck of the first metatarsal. This volar plate contains the two sesamoid bones, inserted in the tendons of the flexor hallucis brevis (Fig. 2). The flexion–extension movement is a rolling and sliding of the metatarsal head within the stable support made up of the base of the proximal phalanx and the volar plate.²¹

Fig 2 The first metatarsophalangeal joint; colour indicates the location of the sesamoid bones within the tendons of the flexor hallucis brevis.

The joint is extremely important for normal gait. There must be 60–70% of extension with the first metatarsal to allow the hallux to function normally during the stance phase of gait.²² In the final stage of forefoot contact, 40% of body weight is imposed on the joint and the big toe²³ (Fig. 3).

Fig 3 The final stage of forefoot contact during walking.

During extension, the sesamoids are drawn from the head–neck junction of the first metatarsal to the distal head area. The average range of motion is 50°.²⁴ Apart from their function in weight bearing, the sesamoids also serve as a fulcrum that increases the mechanical advantage of the flexor hallucis brevis tendon.

The clinical examination of the big toe is summarized in Box 1.

Box 1 Clinical examination of the big toe

Inspection

Redness and swelling: gout

Gross osteophytes: arthrosis

Valgus deformity and enlarged medial portion of the metatarsal head: hallux valgus

Ingrowing toe nails

Dermatological conditions

Functional examination

Passive extension and flexion

Normally the big toe can be extended to a right angle with the forefoot, whereas flexion is only 30–45°. Both end-feels are elastic

Passive abduction, adduction and rotations

Resisted extension: extensor hallucis longus and brevis

Resisted flexion: flexor hallucis longus and brevis

Palpation

For tenderness, fluid and osteophytes

The capsular pattern

The capsular pattern at the first metatarsophalangeal joint is slight limitation of flexion, together with marked limitation of extension (Fig. 4).

Fig 4 The capsular pattern at the first metatarsophalangeal joint.

Gout

The first metatarsophalangeal joint is usually the first joint to be affected in gout. The attack is characterized by a sudden onset of intense pain, frequently at night. The joint is swollen and exquisitely tender. The overlying skin is tense, warm and dusky red. The attack lasts 1–2 weeks, and asymptomatic periods of months or years commonly follow the initial acute attack.²⁵

An acute attack can frequently be aborted by colchicine or by one of the non-steroidal anti-inflammatory drugs.26–28 When attacks are frequent or other gouty complications such as tophi occur, lowering of blood uric acid is indicated.²⁹

Arthritis in adolescence

Early osteoarthrosis at the first metatarsophalangeal joint, mostly bilateral, occurs in adolescence and is the result of osteochondritis dissecans.³⁰ It leads to the formation of a hallux rigidus in young adults.

The teenage patient, nearly always male, develops large osteophytes at the dorsum of both first metatarsophalangeal joints. The onset is slow and there is no history of overuse or of injury. Initially the pain appears only during hyperextension of the big toe. Later, the joint gradually fixes in the neutral position, leading to a hallux rigidus. Pain at every step is inevitable from stress on the rigid joint.

Clinical examination shows the big toe to be fixed in a neutral position. There is only a small range of extension and flexion. The end-feel is hard and large osteophytes can be palpated on the dorsum of the joint.

Because the patient is unable to extend the big toe during the foot-off phase, treatment must aim to introduce a forefoot movement that does not interfere with the mobility of the joint but nevertheless enables the heel to move upwards while the forefoot is on the ground. To do this, a ‘rocker’ is placed in or under a thick and solid sole of a shoe, at the joint line (Fig. 5).

Fig 5 A ‘rocker’ fitted to the shoe.

Instead of extending at the first metatarsophalangeal joint, the forefoot will now rock during a normal gait. If this is not adequate, a steel plate in the sole prevents further stress on the rigid joint, but the resulting gait is less natural.³¹

Surgery for hallux rigidus consists of resection of osteophytes and metatarsal head (cheilectomy)³² or resection arthroplasty.^33–35

Traumatic arthritis

This results from a direct trauma or forceful hyperextension of the joint. This is the case in osteoarthrosis, in which a superimposed post-traumatic arthritis easily occurs. It is also encountered in certain sports, such as soccer and American football.36–39 Treatment consists of an intra-articular injection of 10 mg of triamcinolone and prevention of further overstretching.

Arthrosis in middle age

Osteoarthrosis at the first metatarsophalangeal joint (MPJ) is the second most common disorder affecting the foot after hallux valgus. The prevalence of the condition increases with age, and it has been reported that radiographic changes in the first MPJ are evident in approximately 46% of women and 32% of men at 60 years of age.⁴⁰ The degeneration and stiffness is not the result of a previous aseptic necrosis but has probably been induced by trauma or repetitive stresses. Sometimes a heavy weight falling on the joint or a fracture is the precipitating cause. Repetitive stresses during extension (as in women wearing high heels) can influence the degeneration.

Deterioration is slow and insidious, and therefore symptoms may not arise for years. They appear only when the joint becomes overstrained.⁴¹ In other words, the source of the pain is not the osteoarthrosis as such but the superimposed post-traumatic arthritis. Symptoms therefore start when some dorsiflexion is lost: in men when 45° of extension range has been lost, in women who wear high heels when only 20 or 30° has been lost. The typical case is consequently a middle-aged man or woman who has pain at the big toe during and after walking.

Clinical examination shows a painful and markedly limited extension of the big toe, together with slight limitation of flexion. The end-feel is hard. Osteophyte formation and some local tenderness can be palpated at the dorsum of the joint.⁴²

Because the pain is the result of a post-traumatic arthritis, it can be abolished by one intra-articular injection of triamcinolone. If the patient is careful in the future, wears appropriate shoes with thick, solid soles and avoids high heels, relapses are not to be expected. During the last decade an alternative treatment termed ‘viscosupplementation’ – the intra-articular injection of hyaluronan with the aim of restoring the viscoelasticity of the synovial fluid – has been proposed and studies show promising results.43,44 Good results can also be achieved by traction. Alternatively, mobilization, using traction–translation techniques can be used.⁴⁵ In advanced cases, in which there is hallux rigidus, the use of a ‘rocker’ and a steel sole must be advised (Fig. 5). If all conservative treatment fails, surgery can be undertaken.^46,47

Technique: injection

The patient sits with the foot flat on the couch. The physician grasps the distal phalanx and pulls it in an axial direction, with a slight flexion component. This distracts the joint surfaces and enables the joint line to be identified, which is not always easy to do in patients with large osteophytes: the depression between the osteophyte and the bone should not be mistaken for the joint line. A 1 ml syringe is filled with steroid suspension and fitted with a thin 2 cm needle. After identifying the joint line and the tendon of the long extensor, the needle is passed into the space between the two bones, medially to the tendon (Fig. 6) and the steroid is injected.

Fig 6 Intra-articular injection of the first metatarsophalangeal joint.

The patient should be warned of severe after-pain for 12–24 hours but will be pain free afterwards. If care is taken in the future, a second injection will not be necessary.

Rheumatoid arthritis

This disease often affects the metatarsophalangeal joints.⁴⁸ The usual signs and symptoms of an inflamed joint are seen. The patient has nocturnal pain and morning stiffness. Clinical examination reveals a capsular pattern and a capsular thickening at a warm and swollen joint. Treatment is causative.