Proximal Metatarsal Osteotomy for Bunion (Hallux Valgus) Correction

Summary

A variety of bone cuts (osteotomies) of the first metatarsal have been described as a means of correcting bunion deformities. Bone cuts in the proximal (nearer to the ankle) part of the first metatarsal can more easily correct a larger bunion (greater deformity) than a distal Chevron osteotomy, performed in the more distal (nearer the big toe) aspect of the first metatarsal. Commonly performed proximal metatarsal osteotomies for bunion correction include:

Indications

A proximal metatarsal osteotomy is indicated for patients with a moderate to severe painful bunion deformity that has failed non-surgical management. An ‘osteotomy’ is a cut made in the bone.

Procedure

A proximal metatarsal osteotomy is a cut made in the first metatarsal bone, near one end of the bone called the base of the first metatarsal bone which is the one that is near the midfoot. After this cut is made, the rest of the bone is manipulated or pushed inwards and rotated to correct the bunion deformity. There are several types of proximal metatarsal osteotomies, all of which have the same goal of reducing the angle between the first and second metatarsal (also known as the “intermetatarsal angle”):

Ludloff osteotomy: an oblique cut is made along the side of the shaft of the first metatarsal, and rotated to reduce the angle
Cresentic osteotomy: a semi-circular cut is made back along the base of the first metatarsal, and rotated to reduce the angle
SCARF osteotomy: a Z shaped cut is made from the side of the first metatarsal, using most of its length to give it a more stable configuration. The bone is then moved and/or rotated to reduce the angle.

There are several other types of proximal metatarsal osteotomies, such as the proximal closing wedge osteotomy, the proximal chevron osteotomy, and the medial chevron opening wedge osteotomy, all of which have the same goal of reducing the intermetatarsal angle. The bone on either side of the osteotomy is stabilized with plate/screw fixation while the bone heal in the new position.

Along with this procedure, the bunion (part of the metatarsal head) is also shaved off to make it less prominent and narrow the foot. A soft tissue procedure is performed on the first metatarsophalangeal joint, which releases the tight soft tissue structures on the lateral side of the first metatarsal (near the second toe) and tightens up the soft tissues on the medial side (over the bunion). This helps to correct the bunion deformity. This type of procedure is called the McBride Procedure.

Recovery

During the first 6 weeks following surgery, the bone heals in its new position and the patient’s weight-bearing is limited to protect the construct. At around six weeks and after x-rays verify that the cuts made in the bones have healed, the patient can advance to weight-bearing as tolerated in a protective shoe with physical therapy to maintain as much motion as possible in the great toe joint (first metatarsophalangeal joint). By 8-12 weeks after surgery, the patient can then transition into a stiff sole shoe.

During the first four months, 75% recovery is gained; however, it can be up to a year for maximal improvement. It’s important after the initial swelling has settled, for the first metatarsal to be splinted in its corrected position and gently moved to minimize stiffness. The swelling in the leg and the foot after surgery on the foot is usually dependent and gets worse towards the end of each day. This on and off swelling in the lower limbs can last for a long time. To minimize this on and off swelling, the patient can use a compression stocking.

Potential Complications

General Complications

Specific Complications

Malunion (Bone heals in the wrong position): If a malunion occurs, pain is concentrated on other parts of the foot. The risk factors for a malunion include walking too early, inadequate fixation, or malalignment during initial procedure.
Nonunion or Delayed Union: Risk factors include being a smoker, vitamin D deficiency, poor nutrition, walking too early, and inadequate fixation.
Overload second metatarsalgia (Transfer metatarsalgia): If the new position of the first metatarsal is such where that part of the foot is not taking its share of the weight, then more weight will be more concentrated at the base of the second metatarsal, resulting in painful symptoms
Pain/numbness around local nerves
Stiffness of the big toe: the metatarsophalangeal joint can develop arthritis in the future which is independent of the bunion or surgery for it.
Recurrence of the bunion deformity
Failure to fully correct bunion deformity
Over correction (Hallux Varus): this specific complication is related to the soft tissue procedure. If the soft tissue is released too much on the outside, the toe can curve inward, which is very difficult to correct requiring surgery.

Previously edited by Paul Juliano MD, Christopher Arena MD, and Peter Stavrou, MD

Edited December 6, 2020

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