DEFINITION

The distal chevron osteotomy has proven to be a reliable, reproducible method of bunion repair for mild to moderate deformity. By altering the location and displacement of the osteotomy, the indications can be expanded to more complex deformities while preserving the straightforward surgical exercise.

The apex of the chevron osteotomy can be modified to a more proximal location along with a reduced angle to provide a stable healing surface that facilitates maximal lateral translation.

The proximal location of the osteotomy also reduces the risk of avascular necrosis and permits safe lateral capsule release needed for larger corrections.

This technique facilitates treatment for moderate to severe bunion deformity with a straightforward surgical method using limited, readily available internal fixation.

 

 

ANATOMY

 

Factors contributing to a bunion deformity vary among individuals. The diverse anatomic features require scrutiny during surgical planning.

 

Pertinent to the corrective factors of a translational osteotomy is the width of the distal metatarsal. The amount of correction may be limited in a small, narrow, or “hourglass”-shaped bone.

 

The distal metatarsal articular angle (DMAA) may be altered by varus or valgus rotation during a distal osteotomy. This additional corrective factor should be addressed during the surgical planning.

 

The position of the sesamoids needs to be assessed for optimal correction. Station III subluxation usually requires a lateral capsule release to restore normal joint mechanics.

 

Hypermobility of the first ray should be evaluated. Correction by lateral translation of the distal metatarsal may be compromised if the cuneiform-metatarsal joint is unstable.

 

IMAGING AND DIAGNOSTIC STUDIES

 

Weight-bearing anteroposterior (AP) and lateral radiographs are used to determine bone morphology, associated disease, and deformity parameters used in decision making.

 

The ideal correction is based on a line drawn along the first metatarsal that is parallel to the second metatarsal shaft and touches the medial base of the first metatarsal or cuneiform. This line crosses the first metatarsal shaft bisector near the ideal location for a corrective osteotomy. It also estimates the amount of translational correction needed and whether there is sufficient remaining metatarsal to receive the distal metatarsal head (FIG 1). In this example, the osteotomy could be placed slightly distal to the intersecting lines to use more cancellous bone and still have adequate bone to place the capital fragment.

 

The grade of sesamoid subluxation is evaluated to determine whether a lateral capsular release is indicated. The DMAA is assessed to determine any varus or valgus rotational correction needed at the time of the osteotomy.

SURGICAL MANAGEMENT

Positioning

 

The patient is positioned supine. When regional ankle block anesthesia is used, an ankle tourniquet is applied. Otherwise, a thigh tourniquet can be used for general or spinal anesthesia.

 

 

 

 

FIG 1 • The “ideal correction” is found by drawing a line parallel to the second metatarsal bisector that touches the base of the first metatarsal. The position where this line crosses the first metatarsal bisector helps determine the location and degree of translation possible for the first metatarsal osteotomy.

 

 

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TECHNIQUES

• Soft Tissue Preparation

When significant sesamoid subluxation is present (grade II or III), use a dorsal first web incision to expose the lateral capsule.

A Freer elevator is helpful to probe and identify the dorsal margin of the subluxed lateral sesamoid. Then incise the capsule longitudinally from the phalanx to well proximal to the lateral sesamoid. The adductor tendon is plantar to this incision and is preserved. Leave the intermetatarsal ligament intact. The purpose

 

of this longitudinal cut is to allow medialization of the plantar sesamoid complex at the time of capsule repair from the medial side. Inspect the lateral sesamoid for wear or osteophytes that can be trimmed. Release adhesions and confirm that a freer elevator can be easily passed from proximal to distal between the metartarsal head and sesamoids.

 

Expose the medial joint through a longitudinal incision. Identify and protect the superficial peroneal nerve. Mobilize the tissues to expose the capsule from the medial sesamoid inferiorly to the extensor hallucis longus tendon superiorly. The medial plantar digital nerve is also at risk as the dissection nears the medial sesamoid and needs to be protected.

 

Cut the capsule longitudinally and slightly plantar to the center of the metatarsal. Reflect the capsule to expose the medial metatarsal eminence and the joint, avoid stripping the dorsal and plantar aspect to minimize risk of vascular insult.

• Bone Preparation

 

Remove the medial eminence with a power saw. The amount of bone is based on radiographic interpretation. Avoid excessive removal to prevent hallux varus. Usually, the cut is 1 to 2 mm medial to the articular margin or the sagittal groove.

 

Determine the apex of the osteotomy and mark it with a surgical pen (TECH FIG 1). It is typically 15 to 20 mm from the articular surface. Outline the proximal limbs at an angle of about 35 to 45 degrees. If the limbs are too short, there may be instability; if they are too long, there may be difficulty translating or rotating the distal head portion.

 

Next, use a Freer elevator to gently strip the periosteum and soft tissue over the area where the osteotomy is anticipated to cut the dorsal and plantar aspects of the metatarsal. Again, leave the tissues distal to the bone cut in place to minimize vascular compromise.

 

The osteotomy can be affected by the saw position with a dorsal, plantar, proximal, or distal angulation. Generally, a straight or neutral cut is best.

 

 

 

TECH FIG 1 • Usual location for the osteotomy.

 

 

 

TECH FIG 2 • A. The osteotomy is translated laterally with traction and thumb pressure on the distal end, whereas counterpressure is applied with a towel clip to the medial spike of the proximal end. B. The lateral cortex of the proximal metatarsal provides a stable spike to perch the distal head fragment. C. Radiographic check of pin placement and alignment.

 

 

After completing the osteotomy, the distal head fragment should be readily mobilized. Translation is facilitated by applying traction to the toe with one hand and using the other hand to pull with a towel clip on the apex of the proximal metatarsal. Thumb pressure against the head while maintaining traction will allow repositioning of the metatarsal with minimum force (TECH FIG 2A).

 

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If the head fragment is not readily mobilized, the osteotomy needs to be rechecked and cut. Too much force can break the lateral metatarsal spike.

 

Because the osteotomy is often proximal to the metaphyseal bone, the lateral cortex may appear as a spike. The distal head is then perched on this lateral process to maintain length (TECH FIG 2B). Up to 90% translation is possible and satisfactorily stabilized with Kirschner wires (K-wires). Slight varus or valgus tilt can be applied as indicated by the DMAA.

 

Using 0.054 smooth K-wires, direct a pin from the proximal third of the metatarsal medially while also engaging the lateral metatarsal cortex before entering the distal head fragment. These three points of fixation help maximize stability with large corrections (TECH FIG 3). Place a second similar pin and check the position with radiographic control. K-wires are typically percutaneous, bent, and left out of the skin but can be cut adjacent to the bone and removed electively. Alternatively, a buried small, 3-mm cannulated screw can be used for one of the K-wires, but a second point of fixation, such as a percutaneous K-wire, is recommended for several weeks.

 

 

 

TECH FIG 3 • Optimal pin placement. Note contact with the medial and lateral aspect of the proximal metatarsal before entering the distal head fragment.

 

 

Cut the large prominence of bone from the proximal to medial metatarsal and contour it in line with the distal head's medial margin. It is important to cut this back proximal enough to avoid a residual bump at the mid-metatarsal area (TECH FIG 4).

 

 

 

TECH FIG 4 • The saw is used to remove the remaining medial bump of the first metatarsal. This needs to be contoured in line with the medial metatarsal head to avoid symptoms at this area postoperatively.

• Soft Tissue Closure

 

Tighten the medial capsule by removing a U-shaped wedge of tissue from the plantar limb of the capsule to near the medial sesamoid. The amount of tissue removed is judged to allow adequate correction of the hallux valgus. Next, repair the defect in the plantar capsule with two figure-8 sutures. A small stout needle facilitates passing suture here. Then perform a “pants-over-vest” closure between the plantar and dorsal capsule to medialize and improve sesamoid position. The goal is to bring the medial sesamoid to the medial margin of the metatarsal head (TECH FIG 5). Skin closure and bunion dressings are then applied.

 

 

 

TECH FIG 5 • A,B. From the longitudinal capsule incision, a U-shaped wedge of capsule is removed from the plantar limb of the capsule, then sutured to tighten and correct the hallux valgus. (continued)

 

 

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TECH FIG 5 • (continued) C. Suture is placed in a pants-over-vest technique to advance the plantar capsule medially and dorsally. D. The remaining capsule is closed.

 

 

 

PEARLS AND PITFALLS

 

• Avoid routine lateral adductor release to reduce the risk of hallux varus unless specifically indicated by the clinical situation. The increased lateral translation of the osteotomy usually decompresses the lateral structures. The main focus is to realign the sesamoids under the metatarsal head.

   

• An aggressive contouring of the proximal portion of the metatarsal is necessary to reduce the risk of a residual bony bump near the osteotomy site. This often goes into the medullary canal. The K-wires need to be placed proximal enough to avoid being cut out during this maneuver.

   

• Two K-wires are recommended to reduce the risk of head migration until healing callus has developed.

   

• Other stabilization techniques such as screws or custom plates can be tried, but too rigid fixation may reduce or delay the callus healing response needed to fill the lateral offset created with this technique.

 

 

POSTOPERATIVE CARE

 

Patients are instructed to keep the limb elevated the majority of the first 2 weeks postoperatively. They are allowed to “heel walk” in a postoperative shoe with crutches provided for longer distance or pain management.

 

At 2 weeks, sutures are removed and another bunion dressing is applied. The patient is instructed to passively dorsiflex and plantarflex the toe.

 

At 5 weeks, the pins are removed and the patient is taught to use a compression wrap and toe spacer. Aggressive range-of-motion exercises are initiated. For maximal translation cases, pins are sometimes left in for 6 weeks if no callus is seen on the fifth week x-ray.

 

 

 

FIG 2 • A. Intraoperative radiographic appearance of the osteotomy. The “medial bump” still needs removal from the metatarsal. Office radiographs at 2 weeks (B), 8 weeks (C), and 12 months (D).

 

 

Patients are followed on a 3- to 4-week basis to monitor healing and alignment (FIG 2).

 

With larger osteotomy translation and correction, radiographic healing can take 3 months or more. However, the osteotomy is usually stable for activities of daily living within 2 months. Sports and strenuous activities may require 3 to 5 months of healing.

 

OUTCOMES

We assessed 72 procedures in 62 patients operated on between January 1, 2002 and December 30, 2003. American Orthopaedic Foot and Ankle Society (AOFAS) scores and radiographic assessments were obtained from 39 at an average of 27.6 months after surgery.

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AOFAS scores averaged 93.3, with complete radiographic healing in all patients.

Hallux valgus angle correction averaged 22.3 degrees and intermetatarsal angle correction averaged 7.7 degrees.

 

 

COMPLICATIONS

Complications included three symptomatic hallux varus deformities that were felt to be due to routine adductor release. This has been revised to a limited lateral capsule release as described here with preservation of the adductor tendon in most cases.

There were three symptomatic medial diaphyseal “bumps” due to inadequate resection of the medial metatarsal after translation. This is now being addressed with more aggressive medial contouring.

There was one symptomatic dorsal malunion and one case of surgical neuritis of the peroneal nerve branches.

Only three cases of new or increased transfer lesions were identified. No cases of avascular necrosis were identified.

 

 

SUGGESTED READINGS

1. Austin DW, Leventen EO. A new osteotomy for hallux valgus. Clin Orthop Relat Res 1981;(157):25-30.

    

    

2. Harper MC. Correction of metarsus primus varus with the chevron metatarsal osteotomy. An analysis of corrective factors. Clin Orthop Relat Res 1989;(243):180-183.

    

    

3. Johnson KA, Cofield RH, Morrey BF. Chevron osteotomy for hallux valgus. Clin Orthop Relat Res 1979;142:44-47.

    

    

4. Murawski D, Beskin JL. Increased displacement maximizes the utility of the distal chevron osteotomy for hallux vagus deformity correction. Foot Ankle Int 2008;29:155-163.

    

    

5. Oh IS, Kim MK, Lee SH. New modified technique of osteotomy for hallux valgus. J Orthop Surg 2004;12:235-238.

    

    

6. Sanhudo JA. Correction of moderate to severe hallux valgus deformity by a modified chevron shaft osteotomy. Foot Ankle Int 2006; 27:581-585.

    

    

7. Sanhudo JA. Extending the indications for distal chevron osteotomy. Foot Ankle Int 2000;21:522-523.

    

    

8. Sarrafian SK. A method of predicting the degree of functional correction of the metatarsus primus varus with a distal lateral displacement osteotomy in hallux valgus. Foot Ankle Int 1985;5:322-326.

    

    

9. Schneider W, Aigner N, Pinggera O, et al. Chevron osteotomy in hallux valgus. Ten-year result of 112 cases. J Bone Joint Surg Br 2004; 86(7):1016-1020.

    

    

10. Stienstra JJ, Lee JA, Nakadate DT. Large displacement distal chevron osteotomy for the correction of hallux valgus deformity. J Foot Ankle Surg 2002;41:213-220.

     

     

11. Thordarson D, Ebramzadeh E, Moorthy M, et al. Correlation of hall