Distal Chevron Osteotomy: Perspective 2
SURGICAL MANAGEMENT
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
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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).
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TECH FIG 1 • A. After the skin is incised and the dorsal medial nerve is protected, the capsule is incised in a longitudinal fashion. B. The medial eminence is resected. C. Exposure and preservation of the plantar capsular attachment.
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
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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.
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TECH FIG 2 • A. An imaginary ellipse based on the articular surface is made and the center is marked with
ink. This is used as the apex of the osteotomy. B. The longitudinal cut is performed, ensuring that the proximal limb is extra-articular and the vascular bundle is maintained to the head. C. The saw blade is placed at 90 degrees to the longitudinal cut and then angled to produce a chevron osteotomy of between 60 and 80 degrees.
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.
Use in-line force to compress the head fragment onto the shaft, allowing cancellous impaction (TECH FIG 3B). This aids in the immediate stability of the osteotomy while fixation is achieved.
We prefer fixation using a 1.6-mm Kirschner wire, although a compression screw can also be used. We pass the Kirschner wire in a retrograde fashion under direct vision from the plantar head obliquely across to the proximal fragment and through an appropriately placed small skin incision (TECH FIG 3C). Back the wire out to leave it a few millimeters deep to cartilage, thus maintaining excellent fixation without penetrating the joint. Shave the redundant neck cortex, approximating to 50% of the protruding portion.
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TECH FIG 3 • A. The osteotomy is displaced and held with a clip. B. In-line compression is performed to impact the cancellous fragments together to increase stability. (continued)
Imbricate the medial capsule with a strong absorbable suture while holding the hallux in a neutral or slightly abducted position with the aid of a swab.
Confirm the reduction in the intermetatarsal angle, screws, and relocation of the sesamoids with image intensification with the foot flat on the image intensifier. Assess the need for a proximal phalangeal osteotomy.
Close the wound in layers with continuous Monocryl to the skin and apply a forefoot bandage to maintain the correction.
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TECH FIG 3 • (continued) C. A 1.6-mm Kirschner wire is passed in a retrograde fashion across the osteotomy site.
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Exposure
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The most important part of the exposure is that of the plantar vascular bundle.
Failure to do so may compromise the blood supply to the metatarsal head.
Osteotomy
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If displacement of the osteotomy is difficult, check that all cuts have been
completed. A limited lateral capsulotomy may be performed if needed, restricting the knife cuts to the lateral soft tissues distal to the metatarsal head.
Distal
metatarsal articular angle correction
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To correct an abnormal distal metatarsal articular angle, a small medial wedge
from the vertical limb of the osteotomy can be performed. This will make the osteotomy more unstable, and care must be taken to achieve good fixation.
PEARLS AND PITFALLS
POSTOPERATIVE CARE
If safe, patients are discharged home on the day of surgery with strict advice to elevate the foot whenever resting for the first 2 weeks.
In most cases, they are allowed to bear weight on their heel and lateral forefoot in a hard-soled postoperative shoe.
Cast immobilization is not required.
The wound is inspected at 2 weeks, at which time, the hallux is restrapped and patients are taught simple passive and active toe flexion-extension exercises.
At 4 weeks postoperatively, the osteotomy is assessed. The Kirschner wire is removed in the outpatient setting.
At 6 weeks, the osteotomy is checked radiologically, and if there is consolidation at the line of the osteotomy, the patient is instructed to wear a wide shoe or sneaker and to progress to full weight bearing as tolerated.
Strapping of the hallux is discontinued at this time.
OUTCOMES
The chevron osteotomy is the most commonly performed distal chevron osteotomy for mild hallux valgus in the United States,4 and outcomes are excellent.2,5,9
AVN with the use of a lateral release remains a concern. Recent reports suggest very low rates of AVN when correcting moderate deformities with the chevron osteotomy with a lateral release.1,3,5,7 The improved correction that we see with a lateral release means that we perform it in every case.
Evidence also now suggests that concern that the osteotomy should be reserved for patients younger than 50 years old may not be true, with equivalent results in differing age groups.6,8
COMPLICATIONS
Complications include AVN, stiffness, wound problems, infection, undercorrection, overcorrection, fractures, chronic regional pain disorder, and deep vein thrombosis.
Delayed union and nonunion are rare complications with the use of fixation.
REFERENCES
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Kuhn MA, Lippert FG III, Phipps MJ, et al. Blood flow to the metatarsal head after chevron bunionectomy. Foot Ankle Int 2005;26:526-529.
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Nery C, Barroco R, Réssio C. Biplanar chevron osteotomy. Foot Ankle Int 2002;23:792-798.
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Peterson DA, Zilberfarb JL, Greene MA, et al. Avascular necrosis of the first metatarsal head: incidence in distal osteotomy combined with lateral soft tissue release. Foot Ankle Int 1994;15:59-63.
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Pinney S, Song K, Chou L. Surgical treatment of mild hallux valgus deformity: the state of practice among academic foot and ankle surgeons. Foot Ankle Int 2006;27:970-973.
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Potenza V, Caterini R, Farsetti P, et al. Chevron osteotomy with lateral release and adductor tenotomy for
hallux valgus. Foot Ankle Int 2009;30:512-516.
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Schneider W, Aigner N, Pinggera O, et al. Chevron osteotomy in hallux valgus: ten-year results of 112 cases. J Bone Joint Surg Br 2004;86B:1016-1020.
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Singh SK, Jayasakera N, Nazir S, et al. Use of a polydioxanone (PDS) suture to stabilize the chevron osteotomy: a review of 30 cases. J Foot Ankle Surg 2004;43:306-310.
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Trnka HJ, Zembsch A, Easley ME, et al. The chevron osteotomy for correction of hallux valgus: comparison of findings after two and five years of follow-up. J Bone Joint Surg Am 2000;82A: 1373-1378.
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Trnka HJ, Zembsch A, Weisauer H, et al. Modified Austin procedure for correction of hallux valgus. Foot Ankle Int 1997;18:119-127.