An understanding of the anatomy of the lesser toes is important to appreciate the pathologic changes that occur with deformity. The lesser toes serve to distribute pressure and balance the foot. Deformities can lead to pain, callus formation, transfer lesions, and compensatory gait changes. The deformity initially is flexible, but it may become more rigid as it progresses. The terms that are utilized to describe deformities of the lesser toes are often used incorrectly. This can lead to misunderstandings about the exact pathophysiology and treatment.

A mallet toe is defined as an isolated flexion deformity of the distal interphalangeal (DIP) joint. A hammer toe is a flexion deformity of the proximal interphalangeal (PIP) joint, with or without DIP joint involvement. Finally, a claw toe deformity is an extension of the metatarsophalangeal (MTP) joint with flexion of the PIP and DIP joints (Figure 1). Claw toes often are frequently associated with neuromuscular conditions and typically involve multiple lesser toes and both feet. A hammer toe, however, can occur in isolation; the second toe is most commonly affected.³

The static stabilizers of the lesser toes include the plantar plate, joint capsule, plantar aponeurosis, and the proper and accessory collateral ligaments. The dynamic stabilizers include the extrinsic muscles (extensor digitorum longus and flexor digitorum longus [FDL]) and the intrinsic muscles (extensor digitorum brevis and flexor digitorum brevis, lumbricals, and interossei). The FDL tendon inserts on the distal phalanx and flexes the DIP joint. The flexor digitorum brevis tendon inserts on the middle phalanx and flexes the PIP joint. Because there is no direct flexor insertion on the proximal phalanx, the MTP joint in the extended position lacks antagonists, resulting in flexion in the PIP and DIP joints. The extensor digitorum longus tendon divides into three slips over the proximal phalanx (Figure 2); the middle slip inserts onto the base of the middle phalanx, and the medial and lateral slips pass laterally and converge to form the terminal tendon that inserts on the base of the distal phalanx. The transverse metatarsal ligament divides the intrinsic musculature, with the interossei dorsal and the lumbricals

plantar to the ligament. Both muscles are plantar to the MTP joint axis and provide flexion of the MTP joint. The intrinsic muscles pass dorsal to the PIP and DIP joint axes to extend these joints.⁴ Hammer toe and claw toe deformities occur with simultaneous contracture of the long flexors and extensors of the toe, causing imbalance and overpowering the weaker intrinsic muscles.⁵

The MTP joint often is involved in these deformities. It is stabilized by collateral ligaments and the plantar plate. As the deformity progresses, attenuation of the plantar plate leads to subluxation of the proximal phalanx dorsally onto the metatarsal head. The metatarsal fat pad is pulled distally, and the metatarsal head is depressed plantarly, leading to metatarsalgia.

Patients commonly report pain that is often associated with footwear, as well as callus formation over the PIP joint, corn formation, and pain at the tip of the toe. In addition, the patient may have pain and callosity under the MTP joint. A standing and seated foot examination is imperative. Many deformities cannot be truly appreciated during the seated examination alone. The position of the hallux should be evaluated as a possible contributor to lesser toe deformity. A careful examination of the patient’s neurovascular status is important because a neurologic condition may be the underlying etiology. If surgery is being considered, it is necessary to ensure that tissue perfusion is adequate for successful healing.