Distal Chevron Osteotomy Perspective 2

The primary indication for a chevron osteotomy is symptomatic hallux valgus deformity with a moderate deformity with an intermetatarsal angle of less than 15 degrees. The first metatarsocuneiform joint should be stable. The osteotomy can also be used to correct an abnormal distal metatarsal articular angle. It is used as a sole procedure in those presenting with minimal transfer symptoms.

Preoperative Planning

Anteroposterior (AP) and lateral weight-bearing radiographs of the foot are evaluated for metatarsal length, intermetatarsal angle, hallux valgus angle, distal metatarsal articular angle, and interphalangeal angle for cases that may require a proximal phalangeal osteotomy to obtain complete correction.

Congruency of the joint, presence of osteophytes, the size of the bony medial eminence, and the position and condition of the sesamoids are noted.

Positioning

Surgery is performed on an outpatient basis.

Prophylactic antibiotics are administered.

A thigh tourniquet is applied.

The patient is positioned supine with a sandbag under the ipsilateral buttock so the big toe points to the ceiling.

TECHNIQUES

Chevron Osteotomy

Exposure

Perform the distal soft tissue release through a first web space incision. Take care to avoid stripping the lateral metatarsal head soft tissues. We then perform the osteotomy in a step manner as described in the following text.

Approach the metatarsal through a medial longitudinal incision extending from a point 1 cm proximal to the medial eminence to the medial flare of the proximal phalanx. This can be extended distally if a phalangeal osteotomy is required. Identify the dorsal medial cutaneous nerve and incise the medial capsule sharply in a single longitudinal direction (TECH FIG 1A).

Expose the medial eminence and resect it 1 mm medial to the sagittal sulcus (TECH FIG 1B).

The most important part of the exposure is the identification of the plantar vascular supply (TECH FIG 1C). The osteotomy must be extracapsular. This plantar vascular supply must remain attached to the capital fragment to minimize any risk of avascular necrosis (AVN).

Osteotomy

The apex of the osteotomy is defined as the center of an imaginary ellipse or circle started by the articular surface of the metatarsal. Mark the apex with ink (TECH FIG 2A).

Create the transverse limb of the osteotomy from the apex to the plantar surface of the metatarsal. The obliquity of this cut varies; the most important factor being that the osteotomy must remain extra-articular and the plantar vascular supply must be maintained to the metatarsal head (TECH FIG 2B). Complete the osteotomy through to the lateral side.

Perform the vertical osteotomy by measuring a 90-degree angle to the plantar cut and then angling the saw blade to reduce this angle by 10 to 20 degrees. The exact angle is not crucial; we find that aiming for the angle to be between 60 and 80 degrees produces a stable osteotomy (TECH FIG 2C). Complete this osteotomy to the lateral side to allow displacement of the head fragment. Take care to protect the extensor hallucis longus tendon while performing the vertical osteotomy.

Compression and Fixation

Use a sharp towel clip to grasp the proximal fragment and use the thumb to apply lateral displacement to the capital fragment (TECH FIG 3A). We allow a maximum of 50% displacement. A McDonald dissector can be used to tease the capital fragment over if required.