Distal Chevron Osteotomy Perspective 1

The first reports of a distal metatarsal osteotomy date back to Reverdin, who described in 1881 a subcapital closing wedge osteotomy for the correction of hallux valgus deformity.

The chevron osteotomy has become widely accepted for correction of mild and moderate hallux valgus deformities. In the initial reports by Austin and Leventen¹ and Miller and Croce,¹³ no fixation was mentioned. They suggested that the shape of the osteotomy and impaction of the cancellous capital fragment on the shaft of the first metatarsal provided sufficient stability to forego fixation.

To increase the indication for this technically simple osteotomy, internal fixation and a lateral soft tissue release have been added.

ANATOMY

The special situation distinguishing the first metatarsophalangeal (MTP) joint from the lesser MTP joints is the sesamoid mechanism.

On the plantar surface of the metatarsal head are two longitudinal cartilage-covered grooves separated by a rounded ridge. The sesamoids run in these grooves.

The sesamoid bone is contained in each tendon of the flexor hallucis brevis; they are distally attached by the fibrous plantar plate to the base of the proximal phalanx.

The head of the first metatarsal is rounded and cartilage-covered and articulates with the smaller concave elliptic base of the proximal phalanx.

Fan-shaped ligamentous bands originate from the medial and lateral condyles of the metatarsal head and run to the base of the proximal phalanx and the margins of the sesamoids and the plantar plate.

Tendons and muscles that move the great toe are arranged in four groups:

Long and short extensor tendons

Long and short flexor tendons

Abductor hallucis

Adductor hallucis

Blood supply to the metatarsal head

First dorsal metatarsal artery

Branches from the first plantar metatarsal artery

PATHOGENESIS

Extrinsic causes

Hallux valgus occurs predominantly in shoe-wearing populations and only occasionally in the unshod individual.

Although shoes are an essential factor in the cause of hallux valgus, not all individuals wearing fashionable shoes develop this deformity.

Intrinsic causes

Hardy and Clapham³ found in a series of 91 patients a positive family history in 63%.

Coughlin² reported that a bunion was identified in 94% of 31 mothers whose children inherited a hallux valgus deformity.

Association of pes planus with the development of a hallux valgus deformity has been controversial.

Hohmann⁵ was the most definitive that hallux valgus is always combined with pes planus.

Coughlin² and Kilmartin and Wallace⁸ noted no incidence of pes planus in the juvenile patient.

Pronation of the foot imposes a longitudinal rotation of the first ray, which places the axis of the MTP joint in an oblique plane relative to the floor. In this position, the foot appears to be less able to withstand the deformity pressures exerted on it by either shoes or weight bearing.

The simultaneous occurrence of hallux valgus and metatarsus primus varus has been frequently described. The question of cause and effect continues to be debated.

PATIENT HISTORY AND PHYSICAL FINDINGS

Patient history often includes the following:

Pain in narrow shoes

Symptomatic intractable keratoses beneath the second metatarsal head (in 40% of patients)

Lateral deviation of the great toe

Pronation of the great toe

Keratosis medial plantar underneath the interphalangeal joint

Bursitis over the medial aspect of the medial condyle of the first metatarsal head

Hypermobility of the first metatarsocuneiform joint

Physical examination for hallux valgus deformity includes the following:

Hallux valgus angle: Normal is 15 degrees or less.

Intermetatarsal angle: Normal is 9 degrees or less.

Measurement of the position of the medial sesamoid relative to a longitudinal line bisecting the first metatarsal shaft

• Grade 0: no displacement of sesamoid relative to the reference line

• Grade I: overlap of less than 50% of sesamoid relative to the reference line

• Grade II: overlap of greater than 50% of sesamoid relative to the reference line

• Grade III: sesamoid completely displaced beyond the reference line

Joint congruency: measuring the lateral displacement of the articular surface of the proximal phalanx with respect to the corresponding articular surface of the metatarsal head, as seen on a dorsoplantar roentgenogram

IMAGING AND OTHER DIAGNOSTIC STUDIES

Radiographs of the foot should always be obtained with the patient in the weight-bearing position with anteroposterior (AP) (FIG 1), lateral, and oblique views. The following criteria are examined:

Hallux valgus angle

Intermetatarsal angle

Sesamoid position

Joint congruency

Distal metatarsal articular angle (DMAA): the relationship between the articular surface of the first metatarsal head and a line bisecting the first metatarsal shaft (normal is 10 degrees or less)

Arthrosis of the first MTP joint

DIFFERENTIAL DIAGNOSIS

Ganglion

Hallux rigidus

NONOPERATIVE MANAGEMENT

Comfortable wider shoes

Orthotics

Spiral dynamics physiotherapy in adolescents

SURGICAL MANAGEMENT

Indications

Symptomatic hallux valgus deformity with a first intermetatarsal angle of up to 16 degrees

Stable first metatarsocuneiform joint

Contraindications

Narrow metatarsal head so that adequate translation is not possible

Intermetatarsal angle of more than 16 degrees

Impaired vascular status

Skeletally immature patient

Severe osteoarthritic changes

Preoperative Planning

Standard weight-bearing AP and lateral radiographs are mandatory.

The hallux valgus and intermetatarsal angles and tibial sesamoid position are measured.

A preoperative drawing is helpful.

Clinical examination includes measurement of active and passive range of motion of the first MTP joint as well as inspection of the foot for plantar callus formation indicative of transfer metatarsalgia and stability of the first tarsometatarsal joint.