Indications

Chevron osteotomy is a procedure performed primarily for correction of hallux valgus that is associated with a mild to moderate increase in the intermetatarsal (IM) angle. In our experience, an adductor release is important for an optimal result, and if any doubt exists regarding the adequacy of the chevron osteotomy for correction, it is preferable to perform a distal soft tissue release. This additional step is even more important in patients who are found to have a greater degree of hallux valgus than that expected on the basis of the radiographic IM angle, for whom the soft tissue release is very useful. Recent years have seen an increased interest in “pushing” the procedure for correction of more severe deformity, addressing IM angles of up to 20 degrees. Correction of severe deformity does require moving the metatarsal head laterally by at least 50%, thereby increasing the risk for malunion resulting from poor bone contact. The use of novel internal fixation devices has allowed for 80%–90% translation while maintaining rigid stability of the osteotomy ( Fig. 1.1A–B ).

A large IM angle that would traditionally require a proximally based correction. (A) An excellent correction was achieved with the use of a large (80%) shift of the metatarsal head in conjunction with an Akin osteotomy. (B) This magnitude of correction would traditionally have required a proximally based correction.

The incidence of avascular necrosis of the metatarsal head does not increase when a soft tissue release is performed simultaneously with the osteotomy. Avascular necrosis of the metatarsal head typically results when excessive periosteal stripping is performed along the dorsal lateral metatarsal neck, which really does not need to be exposed. The osteotomy can be performed in conjunction with a closing wedge osteotomy of the hallux proximal phalanx (Akin osteotomy) for patients in whom the hallux valgus interphalangeus angle is abnormal ( Fig. 1.2A–B ). Failure to correct the distal metatarsal articular angle (DMAA) will result in persistent deformity requiring a more complex revision procedure typically involving a distal closing wedge osteotomy in conjunction with proximal correction. In patients with an increased DMAA, anatomic correction of the deformity with a biplanar chevron osteotomy is ideal ( Figs. 1.3 and 1.4A–C ). In geometric terms, the improvement obtained in the distal angulation between the first and second metatarsals will correspond to the magnitude of the lateral shift. It is stated that a 1-degree improvement in angulation will take place with a 1-mm shift of the metatarsal. Although this dictum implies that a deformity greater than 14 degrees cannot reestablish the alignment, such limitation is not supported in clinical practice.

A moderate hallux valgus deformity with significant pronation of the proximal phalanx that makes accurate evaluation of the hallux valgus interphalangeus difficult (A). Correction was achieved with distal chevron osteotomy with additional Akin osteotomy to achieve a neutral alignment, restoring the parallel alignment of the proximal and distal articular aspect of the proximal phalanx (B).

The patient was a 14-year-old girl with a clinically symptomatic hallux valgus (A) with a hallux valgus angle of 30 degrees and an intermetatarsal angle of 16 degrees on the preoperative radiograph. (B) A biplanar chevron osteotomy was planned, with a distal soft tissue release. (C) Note the apparent change in the distal metatarsal articular angle (DMAA) on the radiograph, more likely caused by pronation of the first metatarsal than a true increase in the DMAA. The intraoperative image does show and increase in the DMAA with an erosion of the medial aspect of the metatarsal head.

Note the increased distal metatarsal articular angle in this patient (A). Use of a modified chevron with a longer plantar limb was used to facilitate the angular correction. The large flat dorsal limb allows for a simplified correction as only the dorsal vertical limb requires a wedge resection. The long plantar limb simply rotates and does not require a second cut (B). The large surface that is created heals predictably well, with dorsal to plantar screw fixation used in all cases (C).

Approach to a Standard Chevron Osteotomy

An incision is made medially at the junction of the dorsal and plantar skin, extending proximally for 3 cm from the flare just distal to the metatarsophalangeal joint. This incision is far safer, with more predictable results, than a dorsally based approach, which endangers the nerve and is associated with increased risk for an extension contracture. The incision is deepened through subcutaneous tissue. The soft tissues are dissected carefully to identify the terminal medial cutaneous branch of the superficial peroneal nerve, which is then dorsally retracted ( Fig. 1.5A–K ). It is easier to free the nerve with a hemostat, rather than with a knife or scissors.

Steps in the chevron osteotomy. In this patient, the incision was marked out more distally to perform an additional phalangeal osteotomy (A–C). After the incision is made (A), the dorsal medial cutaneous branch of the superficial peroneal nerve is wiped with a sponge, identified, and retracted (B and C). After longitudinal capsulotomy (D), subperiosteal dissection is performed only medially and dorsally along the metatarsal neck, in the location of the plane of the osteotomy (E). The exostectomy is performed (F and G), and the osteotomy is marked using an electrocautery (H). (I) A fine, small saw blade is used to make the cut at a 60-degree angle. (J) A small clamp is used to grasp the metatarsal neck, and the head is pushed laterally and fixed with a guide pin and a headless cannulated screw. (K) The medial overhanging ledge of bone is shaved.

We now prefer to use a straight, horizontally oriented capsular incision placed slightly more toward the plantar aspect of the metatarsal head. Although many capsular incisions are possible, the correction of the deformity should be obtained by bone realignment and soft tissue balancing to obtain an optimal result. These essential elements of the surgical correction cannot be replaced by a tight capsulorrhaphy, which never constitutes adequate treatment for hallux valgus. The capsular closure should only gently pull the hallux into neutral alignment. Once the capsule is dissected off the medial eminence and the medial aspect of the metatarsal head, the tibial sesamoid is visible. Inspection of the articular surface for cartilage defects or erosion is important.

The alignment of the first metatarsal is checked with respect to the medial eminence and the hallux, and the exostectomy is performed with a flexible chisel or small oscillating saw. The medial eminence must be cut from distal to proximal, to create a smooth transition of the metatarsal head with the metaphyseal flare proximally. Making the cut in the sagittal groove is to be avoided. Such a cut will be too lateral, leading to uncovering of the metatarsal head and medialization of the tibial sesamoid. This altered anatomy will allow irritation of the sesamoid with movement, potentially causing arthritis.

The osteotomy is planned with use of a cautery to mark the apex, approximately 8 mm proximal to the articular surface. Although we use many different osteotomy angles, we often use a standard cut at a 60-degree angle, with the dorsal and plantar limbs of the osteotomy equidistant. Alternative limbs of the osteotomy have been described, with the use of a vertical dorsal limb and a long plantar limb to facilitate correction of the DMAA if a guide is not available. Long-dorsal limbs should be avoided, as that may compromise blood flow to the metatarsal head secondary to the significant dorsal and lateral exposure required. For exposure of the dorsal surface of the metatarsal, the soft tissue is dissected dorsally with limited subperiosteal dissection. Visualizing the dorsal-lateral metatarsal is unnecessary, and only the dorsal and medial aspect of the first metatarsal neck is exposed. Care should be taken not to strip any periosteum on the plantar or dorsal surface more proximal to the level of the osteotomy. A saw blade is used for the osteotomy and aligned perpendicular to the axis of the planned limbs of the osteotomy. The use of a 0.045 Kirschner wire (K-wire) to mark the apex of the osteotomy allows for radiographic verification of the angle of the cut relative to the metatarsal head. It is essential not to overperforate the soft tissues laterally; the saw blade should penetrate the lateral cortex only.

The metatarsal neck should be carefully held with gentle pressure from a towel clip, because grasping with significant force can fracture the metatarsal neck. The metatarsal head undergoes a slight disimpaction, is retracted distally, and is then pushed over laterally manually while the metatarsal shaft is held stable. This maneuver is slightly more difficult if a distal soft tissue release has been performed, because the hallux and metatarsophalangeal joint are effectively disarticulated. During this maneuver, the metatarsal head should not be rotated or tilted. The lateral metatarsal shift ideally is approximately 5 mm and should be checked radiographically. If an abnormal DMAA is present, then a biplanar chevron cut is planned ( Fig. 1.6A–C ). Although manually cutting a biplanar wedge is possible, it is not as reliable as use of a mechanical guide. At the completion of the first metatarsal osteotomy, the biplanar jig is inserted into the osteotomy cut, the saw is placed down on the side of the jig itself, and the cut is then made against the surface of the jig. This procedure removes a perfectly formed 1-mm slice of the bone from both the dorsal and the plantar limbs of the osteotomy medially to create the wedge necessary for biplanar correction.

Use of the Toomey cutting jig. A Kirschner wire (K-wire) is inserted into the metatarsal head, and the jig position is marked on the metatarsal. (A) The chevron cut is made according to the shape of the marked fin, and the jig is inserted. (B) The second saw cut is made, leaving a perfect wedge to be removed to correct the distal metatarsal articular angle. (C) The final correction is seen on the radiograph.

Although the metatarsal head is often intrinsically stable, secure internal fixation is preferable. A guide pin is introduced at the dorsal medial border of the metatarsal just proximal to the osteotomy and its position checked radiographically. It is important to insert the screw as far dorsally as possible. With the medial incision, the tendency is to insert the screw a little too far medially, which then limits the amount of bone that can be trimmed at the completion of the procedure. In fact, the easiest method of fixation is to use a percutaneously introduced pin, directed from dorsal to plantar, and as much bone as is necessary can then be removed from the medial overhang. If a screw is used and inserted too far medially, less medial bone can be trimmed. A drill/countersink is used to prevent fracture of the medial metatarsal neck. The position of the guide pin is checked fluoroscopically, and the length is determined; a screw, usually approximately 20 to 22 mm, is inserted across the guide pin; and compression is obtained. The medial overhanging bone from the osteotomy must be smoothed down with a saw by shaving or back-cutting the bone. Once the screw is inserted, an important step is to verify the distal extent of the screw carefully to ensure that it is not in the joint. We have been misled by what initially appears to be a very well-positioned screw, only to find subsequently that the screw is protruding into the joint by 1 mm. Owing to the overlapping shadow of the lesser metatarsal heads, a useful maneuver is to rotate the hallux under fluoroscopy to verify the location of the screw.

Two sutures of 2-0 Vicryl are inserted at an oblique orientation in a pants-over-vest fashion, from the dorsal proximal aspect of the capsule into the plantar distal position, to pull the hallux into slight supination and slight varus. Checking the range of motion of the hallux metatarsophalangeal joint after the capsular repair is important. If the hallux is pulled too far medially or if the range of motion is insufficient, the sutures must be removed and the repair performed again. We prefer to use absorbable sutures for the subcutaneous, with 3-0 Monocryl or 4-0 Vicryl for the subcutaneous tissue and interrupted 3-0 nylon for the skin (Video 1.1 ). Radiographs are obtained at regular intervals after surgery until healing is noted. In the case of residual hallux valgus interphalangeus or inadequate correction of the deformity, the capsular plication should not be used to gain or achieve correction of the deformity. The use of a concomitant Akin osteotomy is more predictable and can be done through the same incision that is extended distally without complication (seeVideo 1.1 ).