Laboratory Studies
If inflammatory arthropathy is suspected, serologic evaluation should be considered. Tests include evaluation of rheumatoid factor (RF), antinuclear antibody (ANA), human leukocyte antigen (HLA) B27, and Lyme titers.
Imaging Studies
Radiographic evaluation of hammertoe is not necessary for clinical diagnosis; however, it can be helpful for ruling out alternative diagnoses and can aid in surgical planning. Imaging considerations in the evaluation of hammertoe deformity include the following:
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Weightbearing anteroposterior and lateral radiographs of the involved foot are useful (see the images below)
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Intra-articular and periarticular erosions suggest rheumatoid arthritis and psoriatic arthritis, respectively
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Enlargement of the metatarsal head and osteophytes suggests a previous Freiberg infraction
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Varus angulation and/or dorsal subluxation or widening of the joint space of the metatarsophalangeal (MTP) joint suggests MTP instability
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The presence of other deformities should be noted, especially hallux valgus (see the images below), which is associated with the "crossover" toe deformity
Anteroposterior radiograph showing hammertoe deformity in second toe and associated hallux valgus deformity in forefoot.
Histologic Findings
Histologic evaluation is typically not available or necessary before hammertoe treatment. Skin ulceration and osteomyelitis may occur in neuropathic patients with hammertoe deformity. Histologic confirmation of osteomyelitis precludes most hammertoe reconstruction procedures.
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Diagram comparing clinical appearances of lesser-toe deformities.
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Morton foot, wherein second ray (metatarsal and corresponding toe) is longer than first ray.
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Pathomechanics of hammertoe deformity. Elongated plantar plate, caused by either metatarsophalangeal (MTP) synovitis and instability or chronic MTP hyperextension due to toe crowding, results in MTP subluxation or dislocation with compensatory proximal interphalangeal (PIP) flexion.
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Painful dorsal callus over proximal interphalangeal (PIP) joint of second toe, caused by long-standing, fixed hammertoe deformity.
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Physical examination maneuver to diagnose metatarsophalangeal (MTP) instability, wherein examiner attempts to translate proximal phalanx dorsally relative to metatarsal head. In most patients, subluxation is possible; therefore, this test is positive only when it causes pain.
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Hammertoe shield for treatment of flexible hammertoe. Sling over proximal phalanx straightens toe, while shield under metatarsal head provides padding for painful callus that may be present, supports toe plantarly, and anchors sling.
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Severe hammertoe deformity in second toe overlapping great toe with associated hallux valgus deformity.
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Anteroposterior radiograph showing hammertoe deformity in second toe and associated hallux valgus deformity in forefoot.
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Lateral radiograph showing hammertoe deformity.
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Intraoperative fluoroscopic image showing correction of deformities in first and second rays and use of K-wires to stabilize osteotomies.
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Anteroposterior radiograph at 3-month follow-up showing correction of hammertoe and hallux valgus deformities.
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Lateral radiograph at 3-month follow-up showing correction of lesser-toe deformity.
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Clinical photograph showing correction of deformities involving second and great toes.
