First Metatarsophalangeal Total Joint Arthroplasty

The Roto-Glide (Implants International, Cleveland, United Kingdom; distributed by Intercus, Bad Blankenburg, Germany) is a noncemented TiCaP surfaced three-component device for total replacement of the first metatarsophalangeal (MTP-1) joint (FIG 1). It allows for normal mobility in the joint.

The metatarsal implant has a rather long intramedullary stem. The upper part of the metatarsal head has an anatomic flange. In the middle, it has a crest which corresponds to the natural crest in the lower part of the head. The phalangeal implant also has a stem. This stem is hollow and has a flat surface toward the metatarsal head. Between the metal pieces, a polymeniscus is inserted. This meniscus has a peg corresponding to the hollow phalangeal implant. The cranial surface of the meniscus is congruent with the metatarsal’s surface. It should correspond to the crest for sideboard stability.

Thus, extension/flexion takes place between the meniscus and the metatarsal implant, whereas rotation takes place between the meniscus and the phalangeal implant.

The prosthesis comes with different interchangeable sizes and a set of instruments for precise cutting and drilling.

ANATOMY

The MTP-1 joint is a true synovial joint. It has a capsule and stabilizing elements such as collateral ligaments and tendon. Involved in the articulation are also the two sesamoids.

Functions are dorsiflexion/plantiflexion, abduction/adduction, and rotation.

Mobility is foremost dorsiflexion/plantiflexion (8030) in combination with slight abduction/adduction and rotation that secures an adaption of the great toe to the ground no matter the position of the foot.

PATHOGENESIS

Forces during motion are increasing the more dorsiflexion the joint is loaded in and the forces are applied to the upper half of the metatarsal head and the phalangeal counterpart. These forces lead to degeneration of the cartilage over time that effect primarily the upper aspect of the metatarsal head.

The lower part of the metatarsal head, the base of the phalanx, and the sesamoids are less likely affected.

NATURAL HISTORY

Total replacement of the MTP-1 joint has been in use for about 30 years. It has never reached a standard where it could compete with other treatments such as osteotomy, cheilectomy, arthroplasty, or arthrodesis.³

This chapter describes the evolution and suggests a new concept. Before going into the different prosthetic designs that have been tried, one should consider the facts about the anatomy, function, mobility, and forces applied to the MTP-1 joint during loading.

PATIENT HISTORY AND PHYSICAL FINDINGS

Symptoms of arthrosis of the MTP-1 joint include pain in the joint, especially at the dorsal aspect. This gives pressure problems in shoe wear.

The other trouble is diminished mobility, especially in dorsiflexion.

The contour of the metatarsal head is square. On physical examination, osteophytes can be palpated from lateral, over the dorsal aspect, and to the medial side of the metatarsal head.

There is a painful collision phenomenon in dorsiflexion.

The toe is in an anatomic position and the joint is stable.

There may also be distinct pain when moving the sesamoids, especially the tibial one.

IMAGING AND OTHER DIAGNOSTIC STUDIES

Radiographically, arthrosis in MTP-1 joint is graded into four stages, as shown in FIG 2.

Pedography

Unloading under the MTP-1 joint with decreased contact area and decreased force percentage

Lateral shift of the course of the center of gravity, especially during the second half of the gait stance phase

DIFFERENTIAL DIAGNOSIS

Fracture or pseudarthrosis of the sesamoids

Gout

NONOPERATIVE MANAGEMENT

Nonoperative treatment includes stiffening of insole and/or shoe under the MTP-1 joint to decrease the motion of the joint.

Pain medication, nonsteroidal anti-inflammatory drugs (NSAIDs), rest, and complete unloading are other options for nonoperative treatment.

Physiotherapy has no proven effect.

Injections (with corticosteroids) are not recommended due to limited effect and risk of infection.

SURGICAL MANAGEMENT

Please note that insulin-dependent diabetes mellitus (IDDM) and missing flexor hallucis longus tendon/function are considered as absolute contraindications by the author. Deformities such as hallux valgus are considered as relative contraindications.