First Metatarsophalangeal Joint Fusion

14 First Metatarsophalangeal Joint Fusion

Brian S. Winters

Abstract

Fusion continues to be the most successful and reproducible long-term option for reconstruction of the first metatarsophalangeal (MTP) joint in the setting of an unsalvageable joint or severe deformity, such as hallux rigidus, avascular necrosis, infection, rheumatoid/inflammatory arthropathy, and severe hallux valgus. A number of studies have described improved functional outcomes with this procedure that are associated with high success rates of union using various techniques of joint preparation and internal fixation, regardless of the etiology of degeneration. If you adhere to certain principles, you can expect your patients to achieve a good functional result and near-normal activity level. This chapter will help guide you to evaluate pathologies involving the first MTP joint and successfully perform a first MTP joint fusion when indicated.

Keywords: first metatarsophalangeal joint, fusion, arthritis, degenerative joint disease, hallux rigidus

14.1 Indications

14.1.1 Pathology

• Common etiologies of first metatarsophalangeal (MTP) joint pain include hallux rigidus, which can be caused by degenerative or posttraumatic arthritis; avascular necrosis; infection; rheumatoid/inflammatory arthropathy; and severe hallux valgus deformity.¹

• The patient’s major complaint is typically pain and stiffness.

14.1.2 Clinical Evaluation

• The initial step in assessing patients with first MTP joint pathology includes a thorough history to determine when they began to experience pain, its exact location, activities that exacerbate or relieve symptoms, and whether any constitutional symptoms are present.

• The physical examination should assess the overall alignment of the foot and ankle as deformity, such as an adult-acquired flatfoot or valgus ankle, can exacerbate symptoms by creating a pathologic pressure distribution and may also need to be addressed.

• If a prior surgery was conducted, scars and skin quality should be carefully evaluated.

• In the appropriate setting, infection needs to be ruled out as a cause of persistent pain.

• Palpate the distal pulses and obtain a vascular consultation if there is any concern for critical peripheral vascular disease.

14.1.3 Radiographic Evaluation

• Weight-bearing anteroposterior (AP), oblique, and lateral radiographs routinely provide sufficient information to make a definitive diagnosis and formulate a treatment plan.

• In some situations, advanced imaging modalities, such as magnetic resonance imaging (MRI) and computed tomography (CT), may be needed to further evaluate the underlying pathology, such as avascular necrosis.

• In cases where infection is suggested but not confirmed, a Ceretec bone scan or tagged white blood cell scan may be warranted.

14.1.4 Nonoperative Options

• Nonsteroidal anti-inflammatory medication.

• Custom-molded orthotics with a Morton extension.

• Steroid injections.

• Shoe-wear modification (i.e., rigid sole, deep/wide toe box).

14.1.5 Contraindications

• Active infection.

• Situations where approximately 1 cm or greater bone loss is anticipated.

• Severe peripheral vascular disease.

• Uncontrolled diabetes as determined by HbA1C.

• Active smoking.

• Poor soft-tissue envelope.

14.2 Goals of the Surgical Procedure

The ultimate goal is to decrease pain, correct forefoot alignment, and restore patient function.

14.3 Advantages of the Surgical Procedure

Several procedures have been described,² but fusion continues to be the most successful and reproducible long-term option for reconstruction in the setting of an unsalvageable joint or severe deformity, with rates of union being described ranging from 77 to 100%.¹^,³^,⁴

14.4 Key Principles

Meticulous surgical technique must be adhered to throughout the entire procedure in order to decrease soft-tissue trauma and potential for wound complications.

• The length of the first ray must be maintained. Significant shortening can result in pain at the MTP joint region and subsequent transfer metatarsalgia.⁵^–⁷

• Both sides of the joint must be thoroughly debrided to a healthy, bleeding bed of bone in order to maximize the chance of union.

• After the joint is debrided, the hallux needs to be appropriately aligned:

10 to 15 degrees of valgus.

Neutral rotation.

10 to 15 degrees of dorsiflexion relative to the floor.

• Rigid internal fixation is used to compress and stabilize the joint.

14.5 Preoperative Preparation and Patient Positioning

The patient should be placed in the supine position with the foot about a fist length from the end of the operating table. If significant external rotation of the operative extremity is present, a well-padded bump should be placed under the ipsilateral hip so that the foot is pointing toward the ceiling. It is recommended to use a tourniquet, either at the thigh or calf, in order to prevent excessive bleeding into the soft tissues and improve intraoperative visualization. Despite this, meticulous hemostasis still needs to be obtained throughout the procedure in order to prevent a postoperative hematoma and reduce the risk of wound complications/infection. The foot and ankle is then prepped and draped in the standard sterile fashion.

14.6 Operative Technique

14.6.1 Surgical Approach

The first MTP joint is best accessed through a dorsal midline approach (Fig. 14.1). This allows for an expansile incision, if necessary, to obtain adequate exposure. It also avoids the area of the dorsal medial cutaneous nerve. Before making your skin incision, it is imperative that any old scars are noted and incorporated into the new incision, if possible. Unfortunately, this is not always feasible, and in these situations, it is best to make your incision as dorsal as possible. The incision should start approximately 2 cm proximal and extend approximately 2 cm distal to the first MTP joint. The incision is then extended in both directions as needed in order to gain access to the joint while minimizing soft-tissue tension. Therefore, the length of the incision will vary from patient to patient. After the skin and subcutaneous tissue are retracted, the extensor hallucis longus (EHL) tendon will be encountered, which should be isolated and retracted laterally (Fig. 14.2).

The joint capsule should then be incised in line with your skin incision directly down to bone. The capsule and medial/lateral collateral ligaments are then released on both sides of the joint, full thickness, as a continuous envelope using sharp dissection (Fig. 14.3). This will ensure a sufficient release and provide adequate soft-tissue coverage during your closure, which is particularly important when a plate is used. The plantar aspect of the joint should be left intact in order to preserve the blood supply to the proximal phalanx and metatarsal head. Any osteophytes, remaining soft tissue/cartilage, and implants should then be removed.

Fig. 14.1 Planned incision for the dorsal midline approach to the first MTP joint.

Fig. 14.2 Exposure of the extensor hallucis longus tendon. This should be retracted laterally.

Fig 14.3 Exposure of the first MTP joint following full-thickness release of the capsule and collateral ligaments. The central marking on the metatarsal head is your planned entry point for the guidewire.