Matthew J. DeOrio and James K. DeOrio
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.1–4
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 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.2
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 approach to the first metatarsal with the use of an Esmarch tourniquet (FIG 1).
FIG 1 • A. Simulated weight-bearing view of foot. B. A mid-medial approach to the first metatarsal is used. The first metatarsophalangeal and first tarsometatarsal joints are identified.
TECHNIQUES
SKIN AND CAPSULAR INCISION
The skin and subcutaneous tissues are incised sharply to expose the first metatarsophalangeal (MTP) 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 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.
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).
Complete release can be confirmed when the toe can be brought into about 15 degrees of varus through the MTP joint.
The proximal first metatarsal is subsequently exposed both dorsally and plantarly.
TECH FIG 2 • A. A plantar 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.
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 dorsal plantar direction.
TECH FIG 3 • A microsagittal saw is used to create a 60-degree chevron osteotomy with the apex 20 mm from the tarsometatarsal joint.
A proximally based chevron osteotomy is created at an angle of about 60 degrees using a microsagittal saw.
Complete release, both plantarly and dorsally, is confirmed, and care is taken not to fracture either limb of the chevron osteotomy (TECH FIG 3).
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 4).
TECH FIG 4 • 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.
OSTEOTOMY FIXATION
The translated position is secured temporarily with a 0.062-inch K-wire.
The prominent proximal fragment is cleaned of periosteum and removed flush with the distal fragment.
The largest 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 5A,B).
A four-hole hole locking plate is used to bridge the osteotomy medially (TECH FIG 5C).
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 5D).
The K-wire is removed, stability is confirmed, and correction and alignment are confirmed with fluoroscopy (TECH FIG 6).
TECH FIG 5 • A,B. The prominent proximal bone is removed with a saw. The opening created by plantar flexing the metatarsal creates a gap into which the removed bone may be impacted. C. A fourhole locking plate is applied at the osteotomy site. D. The prominent medial eminence is removed 1 mm medial to the sagittal sulcus.
TECH FIG 6 • A,B. Correction of the hallux valgus angle and the 1–2 intermetatarsal angle is confirmed with fluoroscopy.
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 7).
The deep tissues also are closed over the plate to avoid later plate removal.
TECH FIG 7 • 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.
The skin is closed with interrupted vertical mattress 4-0 nylon sutures and a compressive dressing (TECH FIG 8).
TECH FIG 8 • The skin is closed with interrupted 4-0 nylon vertical mattress sutures.
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
· 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.
· Gallentine JW, DeOrio JK, DeOrio MJ. Bunion surgery using locking-plate fixation of proximal metatarsal chevron osteotomies. Foot Ankle Int 2007;28(3):361–368.
· 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.
· Sammarco GJ, Russo-Alesi FG. Bunion correction using proximal chevron osteotomy: A single-incision technique. Foot Ankle Int 1998; 19:430–437.