Proximal Metatarsal Opening Wedge Osteotomy for Hallux Valgus Correction

The proximal opening wedge osteotomy is one of the more than 150 procedures described for the treatment of hallux valgus, indicating the complexity of this deformity.

It was first described by Trethowan¹⁰ in 1923. Trethowan¹⁰ used no fixation, as he thought that by maintaining an intact lateral cortex and using a well-fitting wedge graft, the osteotomy was relatively stable.

The procedure was initially performed mainly for adolescent bunions with questionable results. It was also used in the pediatric population with minimal deformity, prophylactically to prevent progression of the deformity.^1,7,9

The proximal opening wedge osteotomy fell out of favor in subsequent years due to concerns regarding stability and nonunion at the osteotomy site. More recently, the possibility of arthritis in the first metatarsophalangeal joint (MPJ) due to “jamming” and recurrence of the deformity as a result of the metatarsal lengthening created by the opening wedge was questioned.^2,3,11

The earlier concerns have largely been addressed by the advent of more refined surgical techniques, superior internal fixation, and improvement in bone grafting. The addition of a distal closing “chevron-type” wedge osteotomy counteracts the lengthened first metatarsal and negates the increased distal metatarsal articular angle (DMAA), which does occur with the proximal opening wedge osteotomy being a rotational osteotomy.

SURGICAL MANAGEMENT

The proximal opening wedge osteotomy is reserved for the correction of moderate to severe (hallux valgus angle >30 degrees and 1–2 intermetatarsal [IM] angle >15 degrees) hallux valgus (HV) deformity.

The procedure is performed in combination with a lateral distal soft tissue release and a closing distal medial-based wedge osteotomy (chevron-type).

Positioning

The patient is placed supine on the table with a bolster under the ipsilateral buttock if the lower limb is too externally rotated.

A thigh tourniquet is used. Although the procedure is done under general anesthetic, a regional block may be given for postoperative pain relief.

TECHNIQUES

Exposure

The first part of the procedure is the lateral distal soft tissue release while the first web space is still wide.

A 1- to 1.5-cm incision is made on the dorsum of the first web space.

The adductor hallucis tendon is identified and is sharply dissected from its insertion on the proximal phalanx of the hallux.

The dissection is carried proximally and the sesamoid suspensory ligament (between the lateral hallucal sesamoid and the first metatarsal) is transected. There is no need to release the lateral hallucal sesamoid completely.

Capsulotomy

A lateral capsulotomy is next performed. At this stage, one should be able to passively push the hallux into ±20 degrees varus.

A medial incision is made, extending from just distal to the first MPJ proximally along the shaft of the first metatarsal to the first tarsometatarsal (TM) joint.

The incision is carried down to the medial capsule (identified by the vertical orientation of its fibers). Care should be taken not to injure the medial cutaneous nerve, which should be in the dorsal flap.

Inferiorly, the dissection is carried down to the abductor hallucis tendon.

A vertical capsular incision is made approximately 2 to 3 mm proximal to the articular surface.

A more proximal incision is made parallel to the first and joined above with an inverted V and inferiorly with a V, thus excising an elliptical piece of capsule.

The width of this capsular piece is determined by the size of the medial eminence and the amount of deformity that is to be corrected (TECH FIG 1).

A horizontal capsular incision is now made from the dorsal extent of the vertical incision, proximally to the first TM joint.

The capsule is then sharply dissected off the medial eminence.

The medial eminence is cut with a small oscillating saw.

Care is taken to remain medial to the groove and flush with the medial shaft of the first metatarsal.

If there is a significant dorsal bunion, this, too, is resected.

Osteotomy and Plating

The first TM joint is identified with a needle or under fluoroscopy.

A transverse proximal osteotomy is performed approximately 1 cm from the TM joint.

The osteotomy must not be completed, that is, maintain an intact lateral cortex.

Depending on the set, the osteotomy is carefully prized open with either one or two osteotomes or a small distractor, taking care not to fracture the lateral cortex (TECH FIG 2A).