Claw Toe 

The term claw toe is most likely derived from the affected toe's similarity in appearance to the claw of an animal or talon of a bird, as shown in the image below. The talon typically curves upward before it makes a descending C-shaped curve.

A claw toe is a lesser toe with dorsiflexion of the proximal phalanx on the lesser metatarsophalangeal (MTP) joint and concurrent flexion of the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints, as shown in the images below.

Claw toe is differentiated from hammer toe by the combined dorsiflexion of the MTP joint and plantar flexion of the DIP joint in claw toe, as shown in the image below. In contrast, a hammer toe may have some hyperextension at the MTP joint or some flexion at the DIP joint, but not both concurrently. Typically, the DIP joint is extended in a hammer toe.

Hammer toe is differentiated from curly toe, which has combined plantar flexion of all 3 joints, as seen in the first image below, and from a mallet toe, which has a neutral position of the MTP and PIP joints and flexion at the DIP joint, as seen in the second and third images below. The Table contains descriptions of lesser toe deformities. Clawing often affects multiple toes, as seen in the last image below.^{[1, 2, 3, 4]}

Table. Lesser Toe Deformities (Open Table in a new window)

Frequency

The prevalence of claw and hammer toe deformities ranges from 2-20%, with gradually increasing frequency as people age. Therefore, claw toe is most often seen in patients in the seventh and eighth decades of life. Women are affected 4-5 times more than men. Little is mentioned in the literature regarding these deformities in non-shoe-wearing populations.^{[5, 6, 7, 8]} Most people have no underlying disease responsible for the claw toe deformity, but it can occur in association with neuromuscular diseases, such as multiple sclerosis, Friedreich ataxia, Charcot-Marie-Tooth disease, cerebral palsy, mild dysplasia, stroke, and lumbar nerve root impingement. Metabolic diseases, such as diabetes and inflammatory arthropathies (eg, rheumatoid arthritis, psoriasis), can also be accompanied by claw toe deformity.

Claw toe deformity results from altered anatomy and/or neurologic deficit, resulting in an imbalance between the intrinsic and extrinsic musculature to the toes.^{[9, 10]}

The extensor tendon crosses and is held over the MTP joint by an aponeurotic band of fibrous tissue. Although it does not insert into the proximal phalanx, it is able to dorsiflex the proximal phalanx of the MTP joint through this aponeurotic band, which goes around the MTP joint and is inserted onto the plantar plate (see first image below. The extensor tendon splits into 3 parts over the proximal phalanx. The central slip attaches itself to the dorsal aspect of the base of the middle phalanx. The medial and lateral slips rejoin distally to insert on the dorsal aspect of the base of the distal phalanx (see second image below). The extensor tendon is only capable of extending the PIP and DIP joints when the MTP joint is in neutral flexion. Otherwise, this is accomplished by the intrinsic musculature.^{[11, 12, 13] [14]}

The intrinsics are made of the lumbricals, which are strong extenders of the PIP and DIP joints by virtue of their attachment onto the extensor sling and the interossei. Interossei are weak extensors of the interphalangeal joints because so few fibers reach the extensor sling. Furthermore, when the MTP joint is hyperextended, the lumbrical power in extending the PIP and DIP joints is reduced because of a mechanical disadvantage. The flexor digitorum longus (FDL) tendon inserts into the plantar aspect of the distal phalanx, and the flexor digitorum brevis inserts onto the middle phalanx. Thus, no major antagonist to dorsiflexion of the proximal phalanx is present. Hence, when the proximal phalanx dorsiflexes, static tightening of the flexors occurs, which subsequently flexes the PIP and DIP joints. Stabilization of the lesser MTP joint comes from the static restraint of the plantar plate and the collateral ligaments.

The collateral ligaments have been reported as the primary stabilizers of the lesser MTP joint. The 2 sets of collateral ligaments both emanate from the lateral metatarsal head. The phalangeal collateral ligament inserts into the proximal phalanx, and the accessory collateral ligament inserts onto the plantar plate. The plantar plate is attached from the base of the proximal phalanx to an origin on the metatarsal head, just proximal to the plantar articular cartilage.

When the collateral ligaments and plantar plate lose resiliency or are stretched through repetitive dorsal directing forces on the proximal phalanx from ground reactive forces, the proximal phalanx dorsiflexes. Without a strong plantar flexor attached to the proximal phalanx, the proximal phalanx remains in dorsiflexion, and the PIP and DIP joints subsequently flex (see image below). When the flexed position of the PIP and DIP joints remains constant, the collateral ligaments fibrose along the sides of the PIP and DIP joints, and the position of their joints becomes fixed. When this occurs, the claw toe deformity becomes rigid, whereas previously it was considered flexible. This separation of flexible and rigid most often occurs at the PIP joint.

Presentation

Patients with claw toe deformities can present with a variety of symptoms related to the position of the toe. Patients most often report pain at the dorsal PIP joint from an impingement of the toe on the shoe. A callus or erythema is present over the dorsal PIP joint where it abuts the shoe. Patients also may report pain at the tip of the toe from pressure against the point of the distal phalanx.^[15] Patients can have a callus at the tip of the toe and a malformed nail, especially patients with diabetes and neuropathies (see image below). When pain beneath the callus exceeds the neuropathic threshold in a patient with diabetes, an abscess may be present beneath the callus, which is discovered only when the callus is debrided. The other source of pain is the MTP joint, which develops synovitis because of irritation from its extended position and instability.

Another less often seen presentation is impingement of the lateral claw toe on the adjacent toe, causing a callus or soft corn on the medial border of the claw toe. This is usually secondary to clawing of the fourth or fifth toe. Finally, the relative increased pressure beneath the metatarsal head from the inability of the toe to share in weightbearing can result in metatarsalgia. This occurs secondary to distal migration of the plantar fat pad with hyperextension of the MTP joint.

Physical examination

Assessing claw toe primarily consists of a physical examination, with additional tests as required. With the patient sitting, each of the 3 joints (ie, MTP, PIP, DIP) is tested for flexibility in the sagittal plane and stability in the frontal and sagittal planes. Vascularity of the toe is assessed clinically, and the presence of calluses or erythema is duly noted. Normal sensation can be determined by the patient's ability to feel a 0.5-g force with a monofilament pressure device. If the patient cannot detect a 10-g force applied with a monofilament pressure device, this indicates loss of protective sensation.

Indications for treatment are the presentations described in Clinical that produce pain.

See Pathophysiology.

Contraindications to operative treatment include poor vascularity to the toe (including vascular problems that could lead to ischemia and possible need for amputation following surgery, eg, diabetes, atherosclerosis) and poor skin quality. Of course, an open infected wound, for instance on the PIP joint from shoe pressure, should also be resolved prior to surgery.