Dorsomedial Approach to MTP Joint

The Dorsomedial Approach to MTP Joint makes possible most surgery on the metatarsophalangeal joint of the great toe for the treatment of bunions or hallux rigidus.

The Dorsomedial Approach to MTP Joint indications include the following:

1. Excision of the metatarsal head.
2. Excision of the proximal part of the proximal phalanx.
3. Excision of metatarsal exostosis (bunionectomy).
4. Distal metatarsal osteotomy.
5. Soft-tissue correction of hallux valgus, including reefing procedures, tenotomies, and muscle reattachments.
6. Arthrodesis of the metatarsophalangeal joint.
7. Insertion of joint replacements.
8. Dorsal wedge osteotomy of the proximal phalanx in cases of hallux rigidus.

Position of the Patient

Place the patient supine on the operating table.

Landmarks and Incisions

Landmarks

1. The head of the first metatarsal bone.
2. The metatarsophalangeal joint.
3. The extensor hallucis longus tendon

Incisions

The Dorsomedial Approach to MTP Joint can be done by one of the following incisions:

Dorsomedial Incision:

• The dorsomedial skin incision provides access to the exostosis on the metatarsal head without much skin retraction; it is by far the most commonly performed incision.
• The bursa covering the exostosis may have become inflamed, complicating the surgery, and the skin on the medial aspect of the metatarsophalangeal joint is thinner than on the dorsum of the joint and may not heal as well.
• Begin the dorsomedial incision just proximal to the interphalangeal joint on the dorsomedial aspect of the great toe.
• Curve it over the dorsal aspect of the metatarsophalangeal joint, remaining medial to the tendon of the extensor hallucis longus muscle.
• Then, curve the incision back by cutting along the medial aspect of the shaft of the first metatarsal, finishing some 2 to 3 cm from the metatarsophalangeal joint.

Dorsal Incision:

• 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.

Internervous Plane

There is no true internervous plane in Dorsomedial Approach to MTP Joint, because the bone is subcutaneous and the two tendons close to the dissection, the extensor hallucis longus and the abductor hallucis, receive their nerve supplies proximal to this approach and cannot be denervated by it.

Superficial Dissection

Dorsomedial Incision

• Incise the deep fascia in line with the incision. Then, cut down to the dorsomedial aspect of the metatarsophalangeal joint.
• The dorsal digital branch of the edial cutaneous nerve, which often is visible, is retracted laterally with the skin flap on the lateral edge of the wound.
• Make a U-shaped incision into the joint capsule, leaving the capsule attached to the proximal end of the proximal phalanx.

Dorsal Incision

• 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.
• Note that the type and position of the capsulotomy depend on the procedure to be performed

Deep Surgical Dissection

• For both incisions, incise the periosteum of the proximal phalanx and first metatarsal bones longitudinally.
• Using blunt instruments, strip the coverings off the bones, taking care not to damage the tendon of the flexor hallucis longus muscle, which lies in a fibroosseous tunnel on the plantar surface of 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 off the bone. Do not strip all the soft-tissue attachments off the metatarsus if a distal osteotomy of that bone is to be performed, because the metatarsal head is rendered avascular by stripping.

Approach Extension

The Dorsomedial Approach to MTP Joint cannot be extended usefully to other joints in the foot, but may be extended proximally for access to the shaft of the metatarsus.

Dangers

The structures at risk in Dorsomedial Approach to MTP Joint include:

1. The tendon of the extensor hallucis longus muscle
2. The tendon of the flexor hallucis longus muscle

References

• Surgical Exposures in Orthopaedics book – 4th Edition