Hammertoes are a collection of toe deformities. Although many people define hammertoes in different ways, we will use it in its broadest sense as a term describing all deformities of the smaller toes in which the toes curl.   The typical hammertoes is a deformity of the toe where the PIPJ flexes.  This causes this joint to be prominent on the top edge, often the knuckle pads are knobby or discolored from the position and the pressure from shoewear. 

            Deformities at other joints are common. The most frequent associated deformity is an extension deformity at the MPJ.  This raises the toe against the shoe wear. The deformity can even progress to the point where the MPJ becomes dislocated.   On occasion, however, the joint can be in normal alignment.  The deformity at the DIPJ can be extension or flexion.  A variant of the hammertoe is the mallet toe in which the DIPJ only is deformed into flexion. 

            Any of these joints can be turned to the inside or outside in addition to the other deformity.  In fact, one of the most common of these deformities is the “cross-over second toe”.  In this deformity, the second toe completely overlaps the big toe.  This can make it extremely difficult to fit the foot into shoes.  Many people also become very conscientious of the appearance of this deformity.

            The most frequent complaint from a hammertoe is pain underneath the toe in the ball of the foot.  Other problems arise when the toe hits the shoe, when a prominent corner of the toe.  A callus can form over the top of one of these boney prominences or in between the toes.  A callus or even a sore can form also at the very tip of the toe when the toe is not flexible and the tip jams against the floor with weightbearing.

What causes hammertoes?

            This is an area of some discussion among medical professionals.  Occasionally, people state that they are lifelong or occurred at birth.  More commonly they developed their position after an irritation of the MPJ, most commonly the second MPJ, in the ball of the foot.  It is likely that this irritation of the MPJ is a Forefoot Overload Syndrome.  Irritation of the MPJ is often associated with prominence or increased length of the second metatarsal in relation to the adjoining metatarsals.  It is also commonly associated with bunion.  Bunions are often accompanied by decreased pressure on the portion of the ball of the foot under the big toe.  This pressure is partially transferred to the second toe and thus overloads this portion of the joint wearing out the ligaments stabilizing the joint. 

            When the MPJ becomes inflamed, the ligaments start to fail.  Usually the ligaments allow the joint to extend, although the ligaments can also begin to fail so that the toe drifts toward the inside or outside of the foot.  As the MPJ starts to extend, the flexor tendons on the bottom of the toe begin to flex the PIPJ and DIPJ.  Over time, the ligaments within these joints become so stiff that it is even difficult to straighten the toe manually with your hand.

            A peculiar thing can happen to the toe as it gets into this process.  The ligaments constraining the flexor tendons can also begin to stretch allowing the tendons to slide from their normal position on the bottom of the MPJ.  They can continue this slide, sometimes fairly abruptly, until they flip to the side of the joint.  This most commonly occurs in the second MPJ when the second toe crosses over the big toe.  When the tendons assume this position, they no longer work properly.  Instead of doing their normal function of flexing the toe joints, in this new position, they instead cause the toe to deviate to the side, usually the inside of the joint.  The extensor tendons, because they no longer are opposed by the flexor tendons in their new position, begin to extend the toe even more.

            A second method for the development of hammertoes involves damage to the nerves.  When nerves are damaged especially by metabolic problems such as diabetes or in congenital problems, the longest nerves are often the most prone to injury.  The longest nerves of the body are those that give sensation to the toes and those that control the muscles in the foot.  These muscles are called the intrinsic muscles and are most important in control of the PIPJ and MPJ of the toes.  When the nerves are damaged, these muscles become fibrotic and loss their fine balance and can lead to deformity of the joints resulting in a stiff hammertoe.  This is the problem commonly seen in diabetics with hammertoes. 

            The final method and least common is trauma.  A direct blow such as a stubbing injury to the toes can injure the ligaments around any joint in the toe, just as it can in the hand when you jam your finger.  This can lead to a hammertoe deformity.

What else could it be?

            By far and away, the most important cause of foot deformity is hammertoe deformity.  The few mimics of hammertoe deformity can usually be eliminated by a careful physical examination.  Tenderness is usually well localized to the MPJ of the affected toe and not into the web spaces or into the toes themselves or into the midfoot. 

Other problems that may be confused with hammertoe may be:

1. Interdigital neuroma or Morton’s neuroma (usually in the web space, primarily the one between the third and fourth toes)
2. Stress fracture of the metatarsal (usually swollen and the tenderness generally is along the metatarsal shaft away from the joint, often a swelling is appreciated on the bone)
3. Traumatic fracture of the phalanges (if severe, can cause deformity, tenderness is uaually located on the affected bone and radiographs show the fracture)
4. Soft corn in between the toes (usually fairly plainly seen on physical examination
5. Osteochondrosis of the metatarsal head (usually evident on radiograph)

What do you do about it?

Evaluation

            Radiographs are critical for eliminating several important other problems.  Osteochondrosis of the metatarsal head and stress fractures may be suggested by physical examination, but can only be excluded by radiographs.  However, for non-operative treatment, they can sometimes be delayed. 

            Laboratory examination is infrequently necessary unless gout or other inflammatory or infectious process is suspected. 

            Other radiographic examinations such as MRI, bone scan, or CT scan are sometimes ordered to rule out malignant processes or stress fractures which are not apparent on radiographs.  As a rule, these studies are rarely necessary.

 Treatment 

            When embarking on the non-operative treatment of any problem, the goals of treatment have to be carefully defined. Some goals of non-operative treatment are not achievable.  Once a deformity has occurred, there are really no reasonable methods of reversing it.   However, reduction of much of the symptoms associated with a hammertoes deformity is possible.

            The acute inflammation of the MPJ leads to hammertoe deformity nearly 50% of the time.  Occasionally, the deformity can be accompanied by movement of the toe to the inside or outside which can complicate the deformity.  One concept in the treatment of this deformity would be to position or splint the deformity until the acute inflammation subsists.  There have been no studies to examine this.  I have not found a taping or splinting technique that is both effective and comfortable.  Commercial devices such as as the Bundin splint or toe crests are generally only able to position the toe if the deformity is very flexible.  Taping techniques are able to adequately position the toe, but typically cut into the dorsum of the toe in a manner that is not tolerated for long without pain or skin breakdown.

            Another approach to treatment of the forefoot pain especially the pain in the ball of the foot is to wear a stiffer soled shoe.  The stiffness in the sole of a shoe that has a firm rocker sole or has been modified by a steel last in the stole or a spring steel insert placed into the shoe will disperse stress concentration into the ball of the foot.  This decreases pain.  Metatarsal pads placed into the shoe and metatarsal bars placed onto the shoe can disperse pressure and reduce pain. 

            Pressure on deformed toes can be lessened by selecting shoes that have extraroom in the toe box and an upper soft enough to avoid concentrations of pressure.  If a shoe has a compliant upper, often it can be stretched by a commercial shoe stretcher that can be purchased or accessed through a pedorthist or in most shoe repair shops. 

            Separating toes using toe spacers, either silicone or foam rubber or toe sleeves can lessen pressure from toe nails or prominent bones on adjacent toes or on the toe tips.

            Steroid injections are relatively effective in decreasing the inflammation of the MPJ.  The procedure can be administered by a doctor familiar with the technique in the office.  Overall, the degree of pain associated with this is relative mild with 80% of patients in my clinic reporting pain only slightly more than a flu shot.  Over the short run, over half of the patients note significant reduction of the pain.  However, it is not in my opinion a cure, but should be thought of as a treatment of the inflammation that can be used to blunt the pain from the problem while it improves on its own eventually or until a treatment program can be initiated.  Side effects from steroid injection include injection site pain in about 25% which generally lasts for 24-48 hours.  Some clinicians have voiced concern about further damage to the surrounding ligaments and there may be an increased chance of hammertoe formation after this.  Until specific studies are available that examine the rate of hammertoe formation after inflammation of this joint both with and without the concommittant use of intra-articular steroids, it is difficult to say whether this is a complication or a result of the natural course of the problem.

            Finally, rehabilition programs, in my opinion, can be helpful in the treatment of this problem.  A simple program is outline in this website which is geared toward the reduction of forfoot overload..

Surgery

            Surgical treatment of MPJ synovitis and hammertoe deformity is directed to the overall deformity and anatomical factors which may contribute to it.  Certainly, if synovitis of the MPJ without deformity is present, removal of the inflammatory tissue around the joint is a reasonable approach .  I find that this is rarely the case.

            More extensive surgical treatment may involve the lengthening, cutting or redirecting of certain tendons to straighten the various joints involve.  Cutting the ligaments around the MPJ and lengthening the extensor tendon is common. Temporary pinning of the MPJ is often necessary to allow the cut ligaments to heal in the proper length and position for a period of 2-4 weeks. Release of the flexor tendon will often loosen the PIPJ and DIPJ enough to allow for straightening of these joints.  Commonly, transferring these cut flexor tendons around the base of the proximal phalanx can assist in reestablishing the flexion of the MPJ.  Resection of the PIPJ or DIPJ can be added with the intention of obtaining boney fusion of the two bones around the joint if the joint remains stiff.  A shortening osteotomy of the metatarsal, cutting the metatarsal bone and removing a section or allowing one end of the cut bone to slide against the other to shorten the length of the bone, is possible if the metatarsal bones are unusually long relative to the ones next to it.

            If possible preservation of the joint surfaces of the MPJ is preferable to resection of these joints or replacement with silicone devices.

            The procedures are constantly changing and a comprehensive discussion of the exact approach to all the variety of forefoot deformity is beyond the scope of this chapter.  The exact approach to any one foot deformity will vary from surgeon to surgeon.  My own approach is constantly being modified as new devices and information on new techniques become available.

 What can go wrong?

            The most common and troubling problem that can happen after structural correction of a hammertoe is that the deformity can recur or other deformities can be created.  This is most common when there is deviation of the toe toward the inside and outside or when a dislocation is present.

            Numbness is generally present to some extent as the sensory nerves at this level are very small, numerous and easy to injure.

            Persistent pain.

 What are some new treatments on the forefront of medicine?

            A number of new devices have come onto the market for the fusion of the PIPJ and DIPJ.  The result has been more secure and less troublesome fixation of these parts of the surgery. 

            Innovative tendon transfer and ligament repair techniques have also been introduced.  However, these methods have not really been evaluated by investigators that did not develop the techniques.  Unfortunately, these further tests have often dampens the enthusiasm for promising techniques.