Percutaneous Scarf

Eduard Rabat

Josep Torrent

♦ INTRODUCTION

The open scarf osteotomy is an effective and reproducible technique that allows for the correction of the hallux valgus angle (HVA), intermetatarsal angle (IMA), and distal metatarsal articular angle (DMAA) and provides postoperative pain relief.¹,²

Burutaran in 1976 was the first to describe a Z-shaped osteotomy. The technique’s main indication was for lengthening the first metatarsal in pediatric patients with brachymetatarsia (Morton syndrome).³

Weil named the Z-shaped first metatarsal osteotomy the scarf osteotomy. They performed the first study on local vascularization, modified the bony cuts, and increased the length of the osteotomy.⁴ Finally, Barouk popularized the technique globally, particularly in Europe.⁵ Influenced by Barouk, we began implementing the scarf procedure in the 1990s, and it has since become the authors’ gold standard procedure for hallux valgus correction.

The three cuts of the scarf osteotomy provide good inherent postoperative stability.⁶ The main displacements of the osteotomy are in the transverse plane, mainly lateral shift, with medial rotation (DMAA correction) if necessary. In the frontal plane, it is possible to rotate and lower the metatarsal head, while in the sagittal plane, shortening or lengthening can be performed if required.

The great versatility of the scarf osteotomy was the reason we chose this technique as the first option for hallux valgus treatment, apart from the natural evolution toward a minimally invasive procedure. We perform the osteotomy percutaneously with burrs and the use of internal fixation in the form of headless compression screws, also introduced via a minimally invasive approach.

Main Characteristics of the Percutaneous Scarf

Distal and extra-articular metatarsal osteotomy
Mild bunionectomy if required
Three cuts: distal dorsal, diaphyseal, and plantar proximal
Two apexes of the osteotomy: proximal and distal
Osteosynthesis: one or two cannulated headless 3-mm screws
Soft-tissue procedures: lateral release in most cases
Akin osteotomy⁷ is performed in 95% of cases, without osteosynthesis
Akin osteotomy is incomplete preserving the dorsolateral cortex

♦ PREOPERATIVE PLANNING AND PREPARATION

Weight-bearing radiographs of both feet are taken in anteroposterior and lateral projection, preoperatively and during longterm follow-up. The factors evaluated included HVA, I/II IMA, the congruence of the first MTP joint, the presence of arthritis of the first MTP joint, and the position of the medial sesamoid.

Arthritis was graded according to Coughlin and Shurnas’ classification.¹¹ The position of the medial sesamoid was assessed in relation to a line drawn along the longitudinal axis of the first metatarsal on the dorsoplantar weight-bearing radiograph according to the measurement system proposed by Hardy and Clapham.¹²

We also recorded the metatarsal shortening point (MS point) as described by Barouk.⁵ The MS point is the proximal location of the first phalanx basis. The MS point determines the need of the lateral release and shortening of the first metatarsal. The MS point becomes more proximal when there is retraction of the structures on the lateral part of the first MTP joint.

Materials

Specific instruments include a 3-mm Beaver blade, a large Shannon burr (20 mm × 2 mm), and a short Shannon burr (12 mm × 2 mm). A wedge burr (13 mm × 3.1 mm) is used in case medial eminence excision is needed. A specific handpiece system set at high torque and low speed is required.

Osteosynthesis is performed with headless compression screws of 3 mm diameter. As the aim of the fixation is stabilization, not compression, fully threaded screws are recommended.

Surgical Approach

Patients are placed in the supine position. A single intravenous dose of antibiotic prophylaxis (2 g of cefazolin) is indicated for all patients just before surgery.

The procedure is performed under an ankle nerve block without a tourniquet assisted by intraoperative fluoroscopy. The ankle block includes the block of the tibialis posterior nerve, deep peroneal nerve, superficial peroneal nerve, saphenous nerve, and sural nerve, for which 30 mL of equal parts 0.25% bupivacaine and 1% lidocaine without epinephrine is used.

Scarf is performed on an outpatient basis. After the procedure, patients spend 2 to 5 hours in the ambulatory area before being discharged.

SURGICAL TECHNIQUE

The scarf osteotomy can correct the 1-2 IMA and the DMAA and allows for rotation of the metatarsal head and big toe, elevation and lowering of the metatarsal head, as well as lengthening or shortening of the first metatarsal. First, the amount of lateral displacement of the metatarsal head required to correct the IMA is estimated. Then, the need for metatarsal shortening or lengthening is assessed based on the Barouk technique³ of calculating the MS point.

STEP 1: Incision and Creation of the Working Space

The patient is placed in a supine position without a tourniquet. A horizontal 0.5- to 1-cm wound is made in the medial side of the foot, approximately 0.5 cm proximal and centered just below the hypertrophic medial eminence on the first metatarsal head and parallel to its long axis (Figure 4.1). Then, a gentle dissection is performed between the metatarsal head and the articular capsule to create the working space. Thereafter, with the elevator, the most dorsal aspect of the metatarsal bone is reached. The distal apex is positioned at the midpoint of the dorsal cortex and the plantar cortex.

STEP 2: Distal Apex

The distal apex is present at the midpoint of the dorsal and plantar aspects of the metatarsal bone. This surgical point is the reference for the scarf osteotomy. Once the exact point is decided, the metatarsal is drilled in a medial to lateral direction with the burr.

The large Shannon burr (20 mm × 2.2 mm) is inserted through the percutaneous incision, and fluoroscopy is used to verify that the tip of the burr is centered at the distal apex of the planned osteotomy (Figure 4.2).

According to the preoperative plan, the length of the metatarsal bone can be modified with the transverse cuts of the scarf osteotomy. As a burr is used instead of a saw to perform the osteotomy, the unavoidable shortening produced by the burr must be considered, meaning that a minimum of 2 mm and an additional 1 mm due to the vibration is shortened as the osteotomy progresses.

Direction of the Distal Apex

The reference is the long axis of the second metatarsal. The length of the first metatarsal can be modified according to this reference. The direction of the proximal transverse cut must be the same.

A proximal inclination cut relative to the long axis of the second metatarsal will shorten the first metatarsal. A perpendicular cut relative to the long axis of the second metatarsal maintains the length, and when the cut is directed distally, the metatarsal bone is lengthened. Nevertheless, considering the extra shortening because of the burr, the direction of the transverse cut must always be designed to be slightly more distal than planned (Figure 4.3).

Perpendicular cut

This direction will shorten the first metatarsal by about 3 mm considering that the cut is performed with a burr instead of a saw. This design is indicated for patients with mild index plus, where it is only necessary for a slight shortening of the first metatarsal.

Proximal inclination

The proximal inclination of the cut shortens the metatarsal bone. This shortening is necessary for severe hallux valgus with an increased IMA in order to create enough space to shift the fragment laterally enough. It is possible to achieve shortening of up to 1 cm with the proximal inclination of the burr.

Figure 4.1 Medial view of the foot showing the metatarsophalangeal joint. Percutaneous approach to perform the scarf osteotomy.

Figure 4.2 A. Distal apex of the osteotomy. B. Clinical view of the introduction of the percutaneous burr at the starting point. C. Fluoroscopic view of the location of the starting point once both cortexes of the first metatarsal bone have been pierced.

Figure 4.3 A. Direction of the distal apex: perpendicular cut. B. Direction of the distal apex: proximal cut. C. Direction of the distal apex: distal cut.

Distal inclination

The 3 mm of unavoidable shortening because of the burr must be considered. If the length of the first metatarsal is to be retained, the direction of the transverse cut should always be designed to be slightly distal. The main indication here is hallux valgus with index minus to avoid transfer metatarsalgia.
Plantarization of the metatarsal head In some cases, plantarization of the head of the first metatarsal bone may be required, for which the apex could be directed from medial-dorsal to lateral-plantar. This maneuver could be useful to avoid secondary metatarsalgia.