Hammertoe

Overview

The toes are vital to walking and stability (see Anatomy of the Foot and Ankle). Toe deformities are commonly caused by a muscle imbalance in the foot as a result of flat feet, traumatic injury, or disease of the toe joints.

There are at least six sets of muscles that control each toe. Two tendons (the extensor digitorum longus and the extensor digitorum brevis) join on the dorsal aspect (top) of the toes and insert into the middle and distal phalanges (bones) of each toe. On the bottom (plantar aspect) of the toes, there are two muscles that, instead of joining like the extensors, remain separate.

Each muscle stabilizes one of the bones in the toe. The flexor digitorum longus muscle attaches to the bone at the end of the toe (distal phalanx) and the flexor digitorum brevis attaches to the middle bone (middle phalanx). The lumbrical and interossei muscles stabilize the inner toe bone (proximal phalanx). If there is an imbalance in the foot, the smaller muscles can be overpowered by the larger flexor and extensor muscles.

If a foot is flat (pronated), the flexor muscles can overpower the others because a flat foot is longer than a foot with a normal arch. When the foot flattens and lengthens, greater than normal tension is exerted. The toes are not strong enough to resist this tension and they may be overpowered, resulting in one of two deformities, depending on which muscle contracts first.

If the flexor digitorum brevis contracts first and overpowers the rest of the muscles in the toe, the middle phalanx (middle bone) is pulled downward, causing the joint between the proximal and middle phalanges to buckle upward. This is known as a claw toe. If the flexor digitorum longus contracts first and overpowers the smaller muscles, it can pull on the proximal phalanx, causing the outer two joints of the toe to bend downward. This results in a hammertoe.

Incidence and Prevalence

Incidence of toe deformities increases with age and ranges from about 2-20%. Claw toes and hammertoes are approximately 5 times more common in women.

Causes and Risk Factors

In most cases, toe deformities are caused by a muscle imbalance in the foot. Flat feet (pes planus), traumatic injuries, and underlying diseases may increase the risk for claw toes and hammertoes. Diseases and conditions that increase the risk include neuromuscular diseases (e.g., multiple sclerosis, Charcot-Marie-Tooth disease, cerebral palsy), inflammatory diseases (e.g., rheumatoid arthritis, psoriasis), and diabetes.

Signs and Symptoms

If left untreated, claw toes and hammertoes can become serious fixed deformities. In many cases, the inside of the shoe rubs against the bent toe joints, gradually causing calluses to form on the tops of the toes. The metatarsal heads support the body weight and pressure calluses and open sores (ulcer) can develop on the sole of the foot. When deformities reach this stage, the toes are fixed in a bent position and cannot be easily straightened. For this reason, it is important to obtain treatment for claw toes and hammertoes when they first begin to develop, before they become fixed.

Diagnosis

Physical examination and tests are used to diagnose toe deformities. The podiatrist, or foot doctor, measures flexibility, stability, and sensation in the toe during physical examination and checks for redness (erythema), swelling, and calluses.

Blood tests may be performed to rule out diabetes, rheumatoid arthritis, underlying infection, and other conditions. X-rays may be used to determine the position of the toes and to detect arthritis, bone inflammation (osteomyelitis), and inflammation of the joint lining (synovitis).

Treatment

Treatment for claw toes and hammertoes depends on the severity of the deformity. When the toes first start to buckle, they can be straightened easily. If flat feet cause the condition, a podiatrist, or foot doctor, can fit the patient for custom-molded orthotics that provide better arch support and help the muscles work together. In these cases, the prognosis is good.

Without treatment, the soft tissue structures that attach to claw toes and hammertoes begin to tighten. Adhesions gradually form from the tendons to the joint capsules, causing a rigid deformity. Surgery is necessary in these cases.

Arthroplasty is a minor surgical procedure that may be used to treat claw or hammertoes. In this procedure, the podiatrist, or foot doctor, or podiatric surgeon makes an incision along the toe and trims the head of the proximal phalanx, allowing the toe to straighten. If the affected toe does not straighten sufficiently after arthroplasty, a number of progressive procedures may be used to achieve the desired result. If these procedures are not successful, it is likely that the deformity has been present for so long that the joint can no longer function properly. In this case, a procedure called arthrodesis may restore normal mobility.

Arthrodesis involves fusing two bones together, typically the proximal and middle phalanges. The surgeon removes the cartilage from the base of the middle phalanx, the bones are fixed together with a removable pin, and they eventually fuse together.

Following surgery, patients must stay off their feet for several weeks. Complications include infection, numbness in the toe, and failure of the procedure that requires additional surgery.