Rheumatoid Forefoot Reconstruction

Rheumatoid arthritis is an inflammatory condition of synovial joints that usually presents as a symmetric polyarthropathy.

Ninety percent of patients with chronic rheumatoid arthritis have involvement of the foot; the forefoot is the most commonly involved area of the foot.

ANATOMY

The metatarsophalangeal (MTP) joint of the foot is stabilized by the plantar plate, the collateral ligaments, the capsule, and a dynamic balance between the intrinsic and extrinsic muscles of the foot.

The intrinsic muscles are plantar to the MTP joint axis and help to plantarflex the joint.

The proximal phalanx of the hallux has a valgus orientation of 0 to 15 degrees at the MTP joint.

A plantar fat pad normally provides cushioning and protection for the metatarsal heads.

PATHOGENESIS

Unrelenting synovitis leads to a painful and swollen joint. This causes a stretching of the ligamentous structures surrounding the MTP joint.

Ligament stretching combined with forces of walking leads to soft tissue instability, articular cartilage destruction, and subchondral bone resorption.

Residual laxity leads to subluxation and dislocation of the lesser MTP joints. This allows the metatarsal head to protrude through the plantar plate and capsule.

The hallux most commonly develops a hallux valgus deformity, with an occasional hallux varus developing.

MTP instability leads to intrinsic muscles becoming dorsal to the MTP axis, which leads to loss of active MTP flexion and interphalangeal extension. This leads to a claw toe deformity.

Dislocation of the metatarsal lesser MTP joints leads to a distal migration of the fat pad, which exposes the metatarsal heads, increasing pressure in this area.

NATURAL HISTORY

Rheumatoid arthritis initially presents in the foot in about 17% of patients.

It is a progressive disorder that may start as synovitis and progress to dislocations and degeneration of the joint.

The longer active rheumatoid disease is present, the greater the likelihood the patient will develop deformities as a result of the associated synovitis.

PATIENT HISTORY AND PHYSICAL FINDINGS

Initially, patients often complain of an insidious onset of poorly defined forefoot pain and difficulty with ambulation. As synovitis leads to deformity within the forefoot, the symptoms then become more localized.

Patients will often have shoe wear–related irritation along the medial eminence of the hallux and along the dorsal aspects of the proximal interphalangeal (PIP) joints of the lesser toes.

With the development of the lesser toe MTP dislocation, pain on the plantar aspect of the metatarsal heads is present.

Hallux valgus: The examiner should look for the degrees of valgus orientation and its impingement on lesser toes. Patients often have pain along the medial eminence and from pressure on the toes (FIG 1).

Lesser MTP dislocation and plantar callus: The examiner should inspect and palpate the dorsal and plantar aspects of the forefoot. MTP instability can vary from subluxation to dislocation. Increased pressure under the metatarsal heads is a common source of pain (FIG 2).

Examination should include range of motion for the ankle, subtalar, and MTP joints.

The examiner should perform a complete vascular and neurologic examination of the foot.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Plain radiographs will often show periarticular osteopenia, symmetric joint space narrowing, marginal cortical erosions, and subchondral cysts (FIG 3).

The severity of hallux valgus and the presence of MTP dislocation can be evaluated.

DIFFERENTIAL DIAGNOSIS

Inflammatory arthritides such as psoriatic arthritis, Reiter syndrome (reactive arthritis), and ankylosing spondylitis

Gout and pseudogout

Connective tissue disorders (ie, lupus)

Inflammatory bowel disease (Crohn disease or ulcerative colitis)

Neurologic disorders

Osteoarthritis

NONOPERATIVE MANAGEMENT

New pharmacologic agents that can control synovitis have the potential for minimizing the severity and frequency of deformities seen.

Shoe wear modifications such as extra-depth shoes decrease shoe wear irritation.

Custom inserts can help relieve pressure from painful areas.

Plantar calluses may benefit from periodic shaving.

SURGICAL MANAGEMENT

Surgical treatment is indicated for patients whose pain is unrelieved by nonoperative treatment or those with ulcerative lesions due to their deformity.

The goals of surgical treatment include the following:

Restoration of the weight-bearing function of the first ray

Relocation of the plantar fat pad

Reduction of pressure under the lesser metatarsal heads

Correction of claw toe or hammer toe deformities

A variety of methods have been described, but probably the most reliable method for accomplishing these goals is with fusion of the first MTP joint, resection of the lesser metatarsal heads, and either osteoclasis or open hammer toe repair.