Dorsolateral Approach for Bunion Surgery
Dorsolateral Approach for Bunion Surgery
The dorsolateral approach for bunion surgery allows access to those structures present on the lateral aspect of the metatarsophalangeal joint of the hallux. It is used almost exclusively for soft tissue corrective procedures in cases of hallux valgus.
Its uses include the following:
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Tenotomy of the adductor hallucis tendon
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Release of the lateral (fibular) sesamoid bone and, rarely, excision of that bone
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Division of the transverse metatarsal ligament
Soft tissue procedures in hallux valgus are often accompanied by other surgical procedures: Classically, first metatarsal osteotomies. This surgical approach, therefore, is often combined with dorsomedial approaches to the metatarsophalangeal joint of the hallux.
Soft tissue procedures, in isolation, are contraindicated in advanced arthrosis of the metatarsophalangeal joint, spasticity of any type, and when the distal metatarsal proximal phalangeal angle is greater than 15 degrees. As with all procedures on the distal part of the foot, a preoperative assessment of the vascularity of the foot is mandatory.
Position of the Patient
Place the patient supine on the operating table. After exsanguination, use a tourniquet placed on the middle of the thigh. Alternatively, use a soft
rubber bandage to exsanguinate the foot, then wrap the leg tightly just around the ankle (see Fig. 12-1).
Landmarks and Incision
Palpate the head of the first metatarsal bone and the metatarsophalangeal joint on the ball of the foot and along its medial border. Palpate the extensor hallucis longus tendon on the dorsum of the foot. If you flex the toe passively in the plantar direction, the tendon stands out, making identification easier.
Make a 4- to 5-cm longitudinal incision on the dorsal aspect of the foot in the first web space. Center the incision between the first and second metatarsal heads. The incision should extend some 2 cm beyond the metatarsophalangeal joints of the hallux and second (index) toe (Fig. 12-77).
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Figure 12-77 Make a 4- to 5-cm longitudinal incision on the dorsal aspect of the foot in the first web space. Center the incision between the first and second metatarsal heads.
Internervous Plane
There is no internervous plane. The only muscle involved in the approach
—adductor hallucis—receives its nerve supply well proximal to the surgical field, thus the muscle is not denervated by the approach. Terminal branches of the deep peroneal nerve supply skin in the region of the first web space. Care must be taken to preserve these nerves so as not to denervate the skin, creating an area of anesthesia postoperatively.
Superficial Surgical Dissection
Deepen the incision in the line of the skin incision through subcutaneous tissue and fat. Continue dissection to expose and then incise the adventitious bursa present between the first and second metatarsal heads (Fig.12-78).
Deep Surgical Dissection
Insert a self-retaining retractor between the first and second metatarsal heads. Identify the tendon of adductor hallucis as it inserts jointly into the lateral sesamoid bone and the lateral aspect of the proximal phalanx of the hallux (Fig. 12-79). Using a knife blade, develop a plane between the metatarsal head dorsally and the lateral (fibular) sesamoid bone plantarly (Fig. 12-80A). Develop this plane until the blade strikes the base of the proximal phalanx. Turn the blade laterally and plantarward to release the adductor tendon from the base of the proximal phalanx. Withdraw the blade in the same plane between the metatarsal head and the sesamoid, dividing the remainder of the capsule running between the sesamoid bone and the metatarsal. Identify the cut end of the adductor hallucis tendon and dissect it carefully, proximally, until the muscle fibers of the adductor hallucis are found. At this stage, you will be able to see the lateral (fibular) sesamoid clearly (Fig. 12-80B).
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Figure 12-78 Deepen the incision in the line of the skin incision through subcutaneous tissue and fat. Continue dissection to expose and then incise the adventitious bursa present between the first and second metatarsal heads.
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Figure 12-79 Insert a self-retaining retractor between the first and second metatarsal heads. Identify the tendon of adductor hallucis as it inserts jointly into the lateral sesamoid bone and the lateral aspect of the proximal phalanx of the hallux.
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Figure 12-80 A: Using a knife blade, develop a plane between the metatarsal head dorsally and the lateral (fibular) sesamoid bone plantarly. B: Identify the cut end of the adductor hallucis tendon and dissect it carefully, proximally, until the muscle fibers of the adductor hallucis are found. At this stage, you will be able to see the lateral (fibular) sesamoid clearly.
Reinsert the self-retaining retractor deeply, spreading the first and second metatarsal heads apart. This places the transverse metatarsal ligament, which passes from the second metatarsal bone into the lateral (fibular) sesamoid, under tension. Carefully divide the ligament with sharp dissection, noting that the common digital nerve and the artery to the first web space are immediately underneath the structure.
Dang
Terminal branches of the deep peroneal nerve may be injured in superficial surgical dissection. Staying in the midline of the web space will reduce the risk of injuring these important cutaneous nerves. Careless incision of the transverse metatarsal ligament may injure the digital nerve that lies immediately underneath. This risk can be minimized if the structure is identified and stretched using the self-retaining retractor.
How to Enlarge the Approach
This approach cannot be usefully extended either proximally or distally. Its use is exclusively confined to soft tissue procedures on the lateral aspect of the metatarsophalangeal joint of the hallux.