The causes of a hammer toe appear to be multifactorial. The high incidence of hammer toes in the female population has led some to suggest that a constricting toe box is also a causative factor of this deformity. Coughlin et al reported that 62% of the patients in his series considered ill-fitting shoes to be a cause of their hammer toe deformity. The high incidence of female involvement has been previously reported; females constituted 85% of the patient population in a large series. The incidence of hammer toes is reported to increase with increasing age, with the peak incidence in the fifth through seventh decades. Coughlin et al noted in 67 patients that 30% had only single toe involvement, and 40% had three or more toes involved. Although Reece et al, Coughlin et al, and others have reported the second toe to be the most commonly involved. Ohm reported an equal frequency of occurrence in the second, third, and fourth toes. Coughlin et al noted that increased length in comparison to adjacent digits might be a factor in hammer toe development, although this was not a factor in almost one half of cases. A hammer toe deformity may be caused by a muscle imbalance in association with neuromuscular diseases, such as Charcot-Marie-Tooth disease, Friedreich ataxia, cerebral palsy, myelodysplasia, multiple sclerosis, and degenerative disk disease. The deformity also is seen in patients with an insensate foot associated with diabetes mellitus and Hansen disease. Patients with rheumatoid arthritis, psoriatic arthritis, and other types of inflammatory arthritis also can develop hammer toe deformity. Associated hallux valgus deformities have also been implicated as a cause of hammer toe formation.
Occasionally, after fractures of the tibia or other trauma, a progressive hammer toe deformity is observed and is likely the result of nerve or muscle injury from elevated compartment pressures in the involved leg or foot.
A hammer toe deformity may be flexible, semiflexible, or rigid. If the deformity is flexible, the toe may be passively corrected to a neutral position. However, if the deformity is rigid, joint contractures preclude passive correction. The rigidity of the deformity determines the specific surgical procedure that should be performed when conservative measures have failed. The position of the MTP joint when the patient is standing must be carefully evaluated. If a hyperextension deformity is present, correction of only the hammer toe deformity will result in the toe sticking up in an extended position, making shoe wearing difficult. If the MTP joint is subluxated or dislocated, this deformity should be corrected simultaneously with the hammer toe correction.
Tightness of the flexor digitorum longus tendon should be carefully observed with the patient in a standing position. If the flexor digitorum longus tendon appears to be tight in the toe adjacent to the involved toe, the involved toe probably also has a contracture of the flexor digitorum longus tendon. In this case, the tendon should be released in the deformed toe during surgery, or the deformity will probably recur over time.
Another consideration in the treatment of a hammer toe is that there must be sufficient space for the corrected toe to occupy. If a patient has a concomitant hallux valgus deformity that has diminished the interval between the first and third toes and forced the second toe into dorsiflexion, adequate space must be obtained for the corrected lesser toe or the deformity can recur.
A hallux valgus repair may be necessary to obtain sufficient space between the first and third toes to realign the second toe successfully. At times, the adjacent lesser toes can drift into medial or lateral deviation, again diminishing the interval that the corrected toe should occupy. These toes may need to be corrected to afford the corrected hammer toe adequate space. A young patient with a flexible deformity is a candidate for conservative treatment. Likewise, an older patient with multiple medical problems may be a poor surgical candidate. The most important conservative measure is for the patient to acquire roomy, well-fitted shoes.The preferable characteristics of such shoes include a high and wide toe box and a soft sole with a soft upper portion of the toe box. This helps to prevent direct pressure against a hammer toe and subsequent development of painful callosities or ulcers. Local treatment can consist of a doughnut-shaped cushion, foam toe cap, foam tube-gauze, or viscoelastic toe sleeves placed over the PIP joint. Shoes with a stiff insole or a rocker-type outer sole may relieve pressure on the forefoot and diminish metatarsalgia.
The shoe itself might need to be modified if the patient has pain beneath the metatarsal head. Such a modification can consist of a soft metatarsal support, a metatarsal bar, or a comfortable orthosis that relieves pressure beneath the involved metatarsal head. At times,
patients modify their shoes to reduce pressure on a symptomatic hammer toe. A toe cradle can elevate the involved digit and reduce pressure on the tip of the toe. In more advanced cases and with multiple toe involvement, an extra-depth shoe with a polyethylene foam (Plastazote) insole can help to distribute pressure more uniformly on the plantar aspect of the foot. A program with daily manipulation of the toes should be started to try to keep the toes flexible.
If a deformity of the MTP joint exists along with a hammer toe deformity (a complex hammer toe deformity), surgical correction of this deformity also must be considered. In cases of a mild deformity, an extensor tenotomy or lengthening may be sufficient to achieve correction. In cases of a moderate hyperextension deformity of the MTP joint, an extensor tenotomy and MTP capsule release may be necessary. Kirschner wire fixation also may be necessary to stabilize the arthroplasty site as well as the MTP joint. A flexor tendon transfer also may be necessary to achieve stability of the MTP joint. Where subluxation has progressed to frank dislocation of the MTP joint, the soft tissue procedures described are inadequate to achieve reduction, and a metatarsal osteotomy is necessary.
With time, and even with appropriate conservative management, most of these deformities become fixed and often require surgical correction. If surgery is required, it is important that the procedure be carefully selected, depending on the specific cause and type of the deformity.
The patient with a flexible or dynamic hammer toe has a deformity when standing. Practically no deformity is present when the patient sits on the examining table with the foot in an equinus position. The deformity can then be reproduced by dorsiflexion of the ankle joint and with pressure placed beneath the metatarsal heads. These patients do not have the classic claw toe deformity because the MTP joint is not involved. The deformity appears to be caused by a contracture of the flexor digitorum longus tendon. This deformity may be corrected by a flexor tendon transfer.
Source :
COUGHLIN AND MANN’S Surgery of the Foot and Ankle, 10th edition , 2023