First Metatarsophalangeal Joint Arthrodesis Perspective 1

Arthrosis of the first metatarsophalangeal (MTP) joint is commonly seen in osteoarthritis (hallux rigidus), rheumatoid disease, and gout.

The indication for surgical treatment of the first MTP joint is pain where conservative treatment has failed.

Arthrodesis of the first MTP joint is the surgical treatment of choice in rheumatoid disease and is indicated in hallux rigidus when the disease is advanced.

Many techniques in preparation of the joint exist to provide good cancellous apposition:

Flat cuts: These make accurate positioning of the toe difficult.

Cone or peg socket: This leads to excessive shortening.

Ball and socket: This results in minimal shortening and has the additional benefit of ease of adjustment in positioning the toe.

Various methods of fixation have been described. The most biomechanically advantageous method of fixation has been shown to be a dorsal plate and compression screw.^2,3

ANATOMY

The first MTP joint is a ball-and-socket joint.

The normal hallux valgus angle is less than 15 degrees.

The metatarsal inclination angle relative to weight bearing is usually 25 to 30 degrees but varies with foot type (greater for cavus, less for planus) (FIG 1).

The final position of the arthrodesed first MTP joint must allow for heel rise during the late stance phase of gait.

The position can be checked by applying a flat surface to the sole of the foot. The tip of the toe should clear the surface with the interphalangeal joint in full extension and should touch the surface with the interphalangeal joint in 45 to 60 degrees of flexion.

PATHOGENESIS

Primary osteoarthritis (hallux rigidus) and the inflammatory arthritides (rheumatoid, gout, psoriatic arthritis) account for the majority of causative factors.

Secondary osteoarthritis arises from mechanical abnormalities (hallux valgus and varus) and trauma resulting in joint incongruity and excessive cartilage wear.

NATURAL HISTORY

The natural history of first MTP joint arthrosis is related to its cause.

Hallux rigidus is a progressive disease process and the joint will deteriorate with time, but the patient’s symptoms may not show the same deterioration.

Progression of arthrosis secondary to the inflammatory arthritides will be related to the activity of the disease.

PATIENT HISTORY AND PHYSICAL FINDINGS

In true hallux rigidus, patients experience an insidious onset of pain, swelling, and stiffness in the first MTP joint that is aggravated by activity (eg, walking, running).

Lateral forefoot pain due to overload may develop as the foot supinates to avoid dorsiflexion of the first ray just before and immediately after heel rise.

A comprehensive physical examination is required to enable diagnosis and selection of correct surgical procedure.

The physician should palpate the MTP joint for tenderness; dorsal or dorsolateral osteophytes (cheilus) may be palpable and tender.

The physician should examine the range of motion of the MTP and interphalangeal joints. Restriction in dorsiflexion but full plantarflexion may indicate that dorsiflexion osteotomy of proximal phalanx may improve the dorsiflexion arc.

The grind test is not normally painful unless an osteochondral defect is present or degeneration is advanced. If painful, then arthrodesis is indicated.

The physician should observe the patient’s walking gait. Avoidance of weight bearing on the hallux implies pain. Callus may be present under the lesser metatarsals.

The physician should palpate for posterior tibial and dorsalis pedis pulses. Peripheral vascular disease is a contraindication to surgery. If suspected, vascular assessment and treatment is required first.

The physician should palpate and move the tarsometatarsal joint. Arthrosis of the tarsometatarsal joint is a relative contraindication to arthrodesis of the first MTP joint. The examiner should also palpate and move the interphalangeal joint. Arthrosis of the interphalangeal joint is a contraindication to arthrodesis of the first MTP joint.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Weight-bearing anteroposterior (AP) and lateral radiographs should be obtained before surgery.

The severity of the arthrosis can be assessed and any coexisting forefoot pathology identified and addressed at the time of surgery.

The hallux valgus angle and the metatarsal inclination angle should be measured accurately.

The lateral radiograph shows the cheilus and any narrowing of the joint space (either dorsally or throughout).

Hallux rigidus can be graded using the clinical and radiologic information obtained.

We have created a seven-point clinicoradiologic grading system (adapted from Coughlin and Shurnas¹) that correlates the severity of the disease (symptoms, clinical examination, and radiologic findings) with the appropriate surgical procedure (Table 1).