DEFINITION

Correction of major bunion deformities through the proximal portion of the first metatarsal is widely recognized as the established method of reducing the angle between the first and second metatarsal.3,4,5,6

More than 138 techniques have been described for bunion correction, with widely varied methods of fixation of these osteotomies including pins or screws.

Pins provide little inherent stability and have been associated with postoperative infections. Getting excellent fixation of screws can be a problem in cases in which there is poor bone quality.

Plates, although widely used in all other osteotomies, have not been routinely employed in bunion surgery because of the fear of prominence and irritation of the patient's foot.

Recently, the use of locking plates and locking screws has been increasing in the orthopaedic world. The locking plates provide a fixed-angle device, which allows for a potentially stronger method of fixation.4

The advantages of plate fixation for the patient include no external pins, potentially no second procedure to remove hardware, less pain because the osteotomy is stable, and early full or at least partial weight bearing.

Advantages for the surgeon are that it is possible to do any osteotomy for the first metatarsal and that excellent and secure fixation is obtained.

Although many different configurations of the osteotomy can be used, the proximal chevron osteotomy permits a greater degree of correction compared with distal osteotomies. It does this through both an

angular and translational displacement of the distal portion of the first metatarsal.2

SURGICAL MANAGEMENT

Approach

The procedure is performed through a single midmedial longitudinal approach to the first metatarsal with the use of an Esmarch tourniquet (FIG 1) or pneumatic calf tourniquet.

FIG 1 • A. Simulated weight-bearing view of foot. B. A midmedial approach to the first metatarsal is used. The first metatarsophalangeal and first TMT joints are identified.

TECHNIQUES

• Exposure

The skin and subcutaneous tissues are incised sharply to expose the first metatarsophalangeal joint capsule. Care is taken to protect the medial dorsal and plantar cutaneous nerves.

A vertical capsular resection is performed to remove about 3 to 5 mm of capsule just proximal to the base of the proximal phalanx (TECH FIG 1).

A longitudinal incision may also be made in the capsule, excising the midportion.

A dorsomedial incision is made in the capsule parallel to the first metatarsal, creating a plantarly based capsular flap with exposure of the medial eminence.

TECH FIG 1 • Thick skin flaps are preserved, and a vertical segment of redundant capsule is excised.

89

• Release of Lateral Joint Structures

   

  The lateral soft tissues are released from within the metatarsophalangeal joint after distraction of the sesamoids from the first metatarsal with a lamina spreader.

   

  First, use a blunt Freer elevator to develop some room and then cut the capsular tissue with a sharp no. 15 blade (TECH FIG 2).

   

  The medial approach to the release avoids making a separate 1 to 2 incision, and the medial incision is

  just as effective.1,6 It is no longer necessary to make a separate 1 to 2 incision to release the lateral capsule. And it has been shown that release of the adductor does not significantly improve the ability to

  correct hallus valgus.2

   

   

   

  TECH FIG 2 • A. A plantarly and proximally based capsular flap is created, and the capsule is released with a Freer elevator. B. A no. 15 blade is used to complete the release of the lateral capsular attachment to the lateral sesamoid.

   

  Complete release can be confirmed when the great toe can be brought into about 15 degrees of varus through the metatarsophalangeal joint.

   

  The proximal first metatarsal is subsequently exposed both dorsally and plantarly.

• Metatarsal Osteotomy

   

  The location of the tarsometatarsal (TMT) joint is confirmed, and a point is marked about 20 mm distally from the first TMT joint for the apex of the osteotomy and at the midpoint in the dorsoplantar direction.

   

  A proximally based chevron osteotomy is created at an angle of about 60 degrees using a microsagittal saw.

   

   

   

  TECH FIG 3 • A,B. A microsagittal saw is used to create a 60-degree chevron osteotomy with the apex 20 mm from the TMT joint. C. A pointed towel clip is used to hold the proximal metatarsal while the shaft is angulated and translated laterally to decrease the 1-2 intermetatarsal angle and narrow the foot. A K-wire is advanced from the TMT joint into the shaft to hold the correction temporarily.

   

   

  Complete release, both plantarly and dorsally, is confirmed, and care is taken not to fracture either limb of the chevron osteotomy (TECH FIG 3A,B).

   

  The proximal fragment is grasped with a towel clamp, and the distal fragment angulated laterally.

   

  It also is translated 3 to 5 mm laterally and plantarly enough to coapt the superior portion of the chevron, leaving an opening in the plantar portion of the osteotomy (TECH FIG 3C).

   

   

  90

• Osteotomy Fixation

   

  The translated position is secured temporarily with a 0.062-inch Kirschner wire (K-wire).

   

  The prominent proximal fragment is cleaned of periosteum and removed flush with the distal fragment.

   

  This removed portion is then placed as bone graft between the fragments at the opening created in the chevron osteotomy from the plantar translation (TECH FIG 4A,B).

   

   

   

  TECH FIG 4 • A,B. The prominent proximal bone is removed with a saw. The opening created by plantarflexing the metatarsal creates a gap into which the removed bone may be impacted. C. A four-hole locking plate is applied at the osteotomy site. D. The prominent medial eminence is removed 1 mm medial to the sagittal sulcus. E. Correction of the hallux valgus angle and the 1-2 intermetatarsal angle is confirmed with fluoroscopy.

   

   

  A four-hole locking plate is used to bridge the osteotomy medially (TECH FIG 4C).

   

  Care is exercised to avoid penetrating the TMT articulation with screws.

   

  The medial eminence is removed 1 mm medial to the sagittal sulcus (TECH FIG 4D).

   

  The K-wire is removed, stability is confirmed, and correction and alignment are confirmed with fluoroscopy (TECH FIG 4E).

• Capsule and Soft Tissue Closure

Meticulous capsular closure is performed with 2-0 Vicryl sutures, holding the toe in slight varus and supination (TECH FIG 5A).

TECH FIG 5 • A. The capsular flaps are closed with 2-0 interrupted Vicryl sutures with the hallux held in good position. Soft tissue coverage of the plate also is obtained. B. The skin is closed with interrupted 4-0 nylon vertical mattress sutures.

The deep tissues also are closed over the plate to avoid symptomatic prominent hardware.

The skin is closed with interrupted vertical mattress 4-0 nylon sutures and a compressive dressing (TECH FIG 5B).

91

PEARLS AND PITFALLS

Indications ▪ Large symptomatic hallux valgus deformity with minimal degenerative change and a 1-2 intermetatarsal angle greater than 15 degrees.

Exposure ▪ During the approach, dissect thick tissue flaps to allow for improved wound healing.

Metatarsal osteotomy

• Pay particular attention to keeping the saw in the same plane while performing the proximal chevron osteotomy to ensure good bony apposition at the site of fixation. Do not overcorrect the 1-2 metatarsal angle; a negative angle may lead to hallux varus.

   

  Locking plate fixation

  • If the plate requires contouring for larger intermetatarsal angles, do not bend the plate through the locking holes or the screws will not seat properly in the plate.

Capsular closure

• By removing redundant medial capsule during the approach, the capsule repair can be accomplished more efficiently at the conclusion of the procedure. The great toe should be positioned in slight varus, about 2 degrees, to allow healing of the capsular tissues in a good position. These tissues will stretch over time. Do not overtighten the capsule because this will overcorrect the toe position and result in varus malalignment. Capsular imbrication also can be used to correct pronation deformity of the hallux.

POSTOPERATIVE CARE

Bunion dressings are applied at the time of surgery, and sutures are removed 2 to 3 weeks from the date of surgery.

Heel weight bearing can be allowed immediately postoperatively, with advancement to weight bearing as tolerated in a regular shoe at 6 weeks postoperatively.

Radiographs are obtained at 6 weeks and 3 months.

REFERENCES

1. Ahn JY, Lee HS, Chun H, et al. Comparison of open lateral release and transarticular lateral release in distal chevron metatarsal osteotomy for hallux valgus correction. Int Orthop 2013;37(9): 1781-1787.

    

    

2. Augoyard R, Largey A, Munoz MA, et al. Efficacy of first metatarsophalangeal joint lateral release in hallux valgus surgery. Orthop Traumatol Surg Res 2013;99(4):425-431.

    

    

3. Easley ME, Kiebzak GM, Davis WH, et al. Prospective, randomized comparison of proximal crescentic and proximal chevron osteotomies for correction of hallux valgus deformity. Foot Ankle Int 1996;17: 307-316.

    

    

4. Gallentine JW, DeOrio JK, DeOrio MJ. Bunion surgery using lockingplate fixation of proximal metatarsal chevron osteotomies. Foot Ankle Int 2007;28(3):361-368.

    

    

5. McCluskey LC, Johnson JE, Wynarsky GT, et al. Comparison of stability of proximal crescentic metatarsal osteotomy and proximal horizontal “V” osteotomy. Foot Ankle Int 1994;15:263-270.

    

    

6. Sammarco GJ, Russo-Alesi FG. Bunion correction using proximal chevron osteotomy: a single-incision technique. Foot Ankle Int 1998; 19:430-437.