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Hammer digit syndrome refers to a group of deformities of the toes that causes the toes to be in a fixed position. Depending on the type of deformity, this fixed position may be flexed (where the toes are pointed downwards) or extended (where the toes are pointed upwards). The deformities come in a wide range, with names like mallet toe, claw toe, and hammertoes. Of these types of digital deformities, hammertoes are the most common form.
Types of Deformity: The lesser digits of the foot (all but the hallux, or great toe) consist of three bones called phalanges, which are connected to a longer bone called a metatarsal. The joints between theses bones are named for the bones they connect, referred to as metatarsophalngeal joints, and the proximal and distal interphalangeal joints.
With hammertoes, the deformity is seen across all of the joints. This causes the toes to curl up in a predictable pattern, as seen in the picture above. The metatarsophalangeal joint will be fixed in an extended position (with the joint bent upwards) and the proximal interphalangeal joint will be fixed in a flexed position (with the joint bent towards the ground). The distal interphalangeal joint will commonly be bent in an extended position as well.
Mallet toes show a flexed joint only at the distal interphalangeal joint (the joint furthest down the toe, closest to the nail). Claw toes will show a flexion deformity at both the distal and proximal interphalangeal joints, which will curl the toe in the shape of a claw. Hence the name, claw toes.
Causes of the deformity: Normally, the toes are kept in their straight position by a balance from the muscles the insert into the digit. These include both intrinsic and extrinsic muscles of the foot. The extrinsic muscles the insert into the lesser digits are the extensor digitorum longus on the top (dorsal surface) of the foot, and the flexor digitorum longus on the bottom (plantar surface) of the foot. The intrinsic muscles include the lumbricales and interossei muscles, as well as the flexor digitorum brevis and the extensor digitorum breivs. Together, all of the muscles will help to balance the toes, keeping them straight.
When the muscular balance of the digits is lost, it can cause hammer digit syndrome to develop. Most commonly, this will result in the hammertoe variety. There are several different ways that this imbalance can occur.
· Flexor Substitution: The extrinsic flexors of the foot and toes all originate from the back of the leg, or the posterior compartments. These muscles insert into the foot , and act to bring the bones of the foot, including the toes, towards the ground. This is known as plantarflexion. When these muscles become weakened, particularly the soleus muscle, the other flexors are forced to substitute for the soleus. When the flexor digitorum longus substitutes for the soleus, it causes the toes to curl. This can contribute to hammer digit syndrome.
· Extensor Substitution: This is essentially the same mechanism as flexor substitution, but the problem originates with the extrinsic extensors of the foot. The extensors are located in the anterior compartment of the leg. In particular, when the tibialis anterior becomes weakened, the extensor digitorum longus will increase its pull on the toes. This will cause the toes to curl up.
· Flexor Stabilization: This is a problem with the intrinsic muscles of the foot, in particular the interossei and the lumbricales. These two groups of muscles function to stabilize the toes. When the muscles become weakened, such as in flat feet, the relative pull from the flexor digitorum longus increases. This will cause the toes to curl.
High-Heeled Shoes and how they contribute to Hammertoes: It is commonly accepted among podiatrists and other foot and ankle specialists that high-heeled shoes can help contribute to the development of hammertoes. This is due to the position that the foot is put in when wearing high-heels. When a foot is placed in a high heeled shoe, the foot is in a plantar-flexed position. This lengthens the extensor muscles of the foot (especially the tibialis anterior), which effectively weakens the pull of the muscle on the foot. Thus, extensor substitution is allowed to take place. Similarly, when a person wears high-heeled shoes all day, the flexors and intrinsic musculature is not functioning in its optimal motion. The long flexors of the toes can be over-worked, causing further curling of the toes. Therefore, he use of high-heeled shoes creates the perfect situation for hammertoes and other varieties of hammer digit syndrome to develop.
Complications of Hammer Digit Syndrome:
Because the toes are no longer straight in hammer digit syndrome, they may no longer fit properly into shoes. A toe that is curled up inside a shoe may be forced to rub up against the shoe, causing pain and hotspots to develop. These areas of friction can quickly develop into corns and calluses. The areas of friction are commonly seen on the top of the toes, at the joints.
Additionally, when the toes are curled up, weight can no longer be placed on the toes in the proper way. Therefore, the weight is shifted more onto the ball of the foot, which can cause large calluses to develop on the bottom of the feet.
Treatment: There are a number of factors that play into the treatment of the different varieties of hammer digit syndrome. Most commonly a conservative approach is taken first. This would include things like trimming of the corns and calluses, a change in shoe gear to accommodate the deformity, and different padding techniques to help alleviate some of the pain. All of these measures will help relieve the pain associated with hammertoes, but will not correct the deformity.
The only way to truly correct the deformity is to have surgery on the toes. Depending on the extent of the deformity, the surgery may address only the soft tissues of the toes (the ligaments and tendons influencing the deformity) or it may include the removal of some of the bone in the toes.
