Dorsal Approaches to the Metatarsophalangeal Joint of the Great Toe

Dorsal Approaches to the Metatarsophalangeal Joint of the Great Toe‌

The dorsal approach can be employed for most of the surgeries to the metatarsophalangeal joint of the great toe for the treatment of bunions or hallux rigidus.

Its use includes the following:

1. Excision of metatarsal exostosis (bunionectomy)

2. Distal metatarsal osteotomy

3. Excision of the proximal part of the proximal phalanx

4. Soft tissue correction of hallux valgus, including reefing procedures, tenotomies, and muscle reattachments

5. Arthrodesis of the metatarsophalangeal joint

6. Insertion of total joint replacements

7. Dorsal wedge osteotomy of the proximal phalanx in cases of hallux rigidus

The skin overlying a bunion may be red, thin, and inflamed. In extreme cases, frank ulceration with associated infection may occur. A careful assessment of the skin and vascular state of the foot is mandatory as part of the preoperative workup.

Position of the Patient

Place the patient supine on the operating table. After exsanguination, use a tourniquet placed midthigh. Alternatively, used a soft rubber bandage to exsanguinate the foot, then wrap the leg tightly just above the ankle (see Fig. 12-1).

Landmarks and Incision

Palpate the head of the first metatarsal bone and the metatarsophalangeal joint, which are on the ball of the foot and its medial border. In cases of

bunion, the metatarsal head is prominent medially.

Palpate the extensor hallucis longus tendon on the dorsum of the foot. When it is tight, it stands out when the great toe is passively flexed in the plantar direction. In most cases of hallux valgus, it is displaced laterally.

Begin the dorsal incision just proximal to the interphalangeal joint and just medial to the tendon of the extensor hallucis longus muscle. Extend the incision proximally, parallel, and just medial to the tendon of the extensor hallucis longus. Finish about 2 to 3 cm proximal to the metatarsophalangeal joint. Note that the final incision is straight (Fig. 12-71).

The dorsal incision avoids cutting through the thin, frequently atrophic skin overlying the medial aspect of the first metatarsal osteophyte. The disadvantage of the incision is that more soft tissue dissection is required to carry out procedures on the medial capsule. Terminal cutaneous branches of the deep peroneal nerve and saphenous nerve are also more at risk.

Internervous Plane

There is no true internervous plane. The bone is subcutaneous; the two tendons that lie close to the dissection—the extensor hallucis longus and the adductor hallucis—receive their nerve supply proximal to this approach and cannot be denervated by it.

Superficial Surgical Dissection

Divide the deep fascia in line with the incision, and retract the tendon of the extensor hallucis longus muscle laterally. To enter the joint, incise the dorsal aspect of the joint capsule. The type and position of the capsulotomy depends on the procedure to be performed (Figs. 12-72 and 12-73).

Deep Surgical Dissection

Incise the periosteum of the proximal phalanx on the first metatarsal bone longitudinally. Using both sharp and blunt dissections; strip the coverings of the bone, taking care not to damage the tendon of the flexor hallucis longus muscle, which lies in a fibro-osseous tunnel on the plantar surface at the proximal phalanx, between the sesamoid bones. The extent of the deep dissection depends on the procedure to be carried out. Strip only a

minimum of periosteum of the bone. Do not strip all the soft tissue attachments off the first metatarsal if the distal osteotomy of that bone is to be performed, as the metatarsal head may be rendered avascular by stripping.

Figure 12-71 Dorsal incision for the approach to the metatarsophalangeal joint of the great toe. Note that the tendon of the extensor hallucis longus is displaced laterally and that the sensory nerve to the medial aspect of the great toe runs parallel to the incision. Note that the great toe is framed by branches of the saphenous nerve medially and the deep peroneal nerve laterally.

Figure 12-72 Develop the skin flaps. Divide the deep fascia in line with the skin incision, and retract the tendon of the extensor hallucis longus laterally.

Figure 12-73 Incise the joint capsule dorsally, and remove as much of the capsule as necessary depending on the procedure to be performed.

Dang

The tendon of the extensor hallucis longus muscle, which lies on the lateral edge of the wound, should not be cut during the approach. In most cases of bunion, the tendon bowstrings laterally across the metatarsophalangeal joint and is lateral to the incision. Protect the dorsal digital nerve if it can be seen along the line of the incision (see Figs. 12-71 and 12-74). The tendon of the flexor hallucis longus muscle is vulnerable at the base of the proximal phalanx. The tendon lies in a groove on the plantar surface of the proximal phalanx so close to the periosteum that, if care is not taken, it may be damaged during stripping. Note that this tendon is often displaced laterally in patients with hallux valgus (see Fig. 12-54).

How to Enlarge the Approach

Careful and systematic stripping of the bone provides an adequate view of the joint. The approach cannot be extended usefully to other joints in the foot, but may be extended proximally to access the shaft of the first metatarsal bone.