The term “bunion” refers to the any enlargement around the first metatarsal phalangeal joint (MTPJ). The term “hallux valgus” has been used as a catch-all phrase to include all types of bunions without being specific. The actual definition of “hallux valgus” is a frontal plane deformity of the great toe in which the plantar aspect of the toe is beginning to face the second toe. “Hallux abductus” is a transverse plane deformity of the great toe in which it is moving toward, abutting, overriding, or underriding the second toe. In most cases the surgeon will make a diagnosis of “hallux abductus with bunion deformity” (Fig. 32-1) or “hallux abducto-valgus with bunion deformity” depending upon the preoperative position of the great toe. A “dorsal bunion” is an enlargement over the dorsal aspect of the first MTPJ and in most situations is indicative of limited first MTPJ motion known as “hallux limitus.”

Bunion deformities are complex problems and dynamic, meaning that over time the deformity will most likely progress regardless of the conservative measures employed. This is especially true if there is any structural malalignment of the bones that comprise the first ray. Once a “bunion” deformity has developed there are no conservative measures that will reverse the situation. Conservative measures may halt the progression of the deformity and/or reduce the symptoms associated with it. The etiologies are varied and at times are the result of several different causes. The following are the more common causes of bunion deformities:

It should be noted that once the intrinsic and extrinsic muscles of the LE abnormally function during gait and the patient significantly pronates, the hallux begins to deviate toward the second toe and retrograde forces on the first metatarsal begin to move this bone more medially. The more transverse plane mobility that exists at the first metatarsal cuneiform joint (MCJ), the more the first metatarsal may splay from the second metatarsal. The more sagittal plane mobility that exists at the first MCJ, the more the first metatarsal will migrate dorsally and produce limited first MTPJ motion (hallux limitus rather than a medial bunion deformity with a hallux abductus).

A very detailed clinical examination of the foot and LE is required both non–weight bearing and weight bearing to determine areas of pathology contributing to the “bunion” deformity. Objective measurements of the first MTPJ range of motion (ROM) (dorsiflexion and plantarflexion) are obtained non–weight bearing (Fig. 32-2). The amount of dorsiflexion deemed necessary for a normal propulsive gait is approximately 65° (Fig. 32-3). Since plantarflexion of the first MTPJ is not a motion required for gait, there are really no normal values usually considered other than knowing that the first MTPJ can plantarflex to some degree without discomfort. Evaluation of mobility at the first MCJ on both the transverse and sagittal planes is important to detect any hypermobility. If sagittal plane hypermobility of the first ray appears to exist, then one should dorsiflex the hallux at the first MTPJ and evaluate the motion again. By dorsiflexing the hallux, one is engaging the plantar fascia (windlass mechanism). If the abnormal sagittal plane motion is no longer present, then the use of an orthotic device will most likely halt any deforming forces caused by hypermobility of the first ray, which are usually jamming of the first MTPJ in gait, limited first MTPJ motion, and transfer metatarsalgia. However, if by engaging the windlass mechanism by dorsiflexing the hallux and the hypermobility appears to remain, then a surgical procedure aimed at stopping this motion is usually needed, such as a fusion of the first MCJ known as a Lapidus procedure. Symptoms may not always be the indication for pursuing a surgical correction of the “bunion.” A patient who has a progressive hallux abductus and a bunion deformity in which the hallux is significantly abutting the second toe but is asymptomatic may require a surgical correction of the deformity to prevent deformity of the second toe and dislocation of the second MTPJ.

Weight-bearing radiographic evaluation of the foot is extremely important in the evaluation of the “bunion” deformity to determine any structural malalignment of the first ray and at which level or levels the pathology exists (Fig. 32-4). A unique aspect of the first MTPJ is the presence of two sesamoid bones on the plantar aspect of the metatarsal head (Fig. 32-5), which serve as a fulcrum for the tendons of the flexor hallucis brevis muscle that attaches to the plantar aspect of the base of the proximal phalanx. At times the fibular sesamoid bone may become a very powerful deforming force and the surgeon may need to release its soft tissue attachments or excise it (Fig. 32-6). This maneuver can create scar formation to such an extent as to limit first MTPJ dorsiflexion postoperatively.

Various angular measurements are taken and correlated with the clinical examination.

The surgeon must also take into consideration the patient’s overall medical health, body type, age, occupation, and home environment before deciding which surgical procedure or procedures would best correct that patient’s “bunion” deformity. While the clinical and radiographic evaluation data may indicate an “ideal” surgical correction, the specific medical and/or social data on that specific patient may dictate a lesser surgical correction.

One of the more common bunionectomy procedures involves a first metatarsal osteotomy (Austin or Chevron procedure) and a soft tissue rebalancing (McBride procedure) to correct both a positional and a structural malalignment (see Fig. 32-11, A). A pneumatic ankle cuff is used to stop all blood flow into the foot and allow for a dry field during the procedure, which usually requires 45 to 60 minutes to complete. After a sterile preparation of the foot, a dorsal medial incision is made over the first MTPJ and by using blunt and sharp dissection the subcutaneous tissues and neurovascular elements are separated from the dorsal and medial aspect of the first MTPJ capsule (see Fig. 32-7, A). The surgeon then uses one of many capsulotomies to enter and expose the first MTPJ.

Fig. 32-7, B shows an inverted “L” capsulotomy having been performed and the incision through the medial suspensory and collateral ligaments. Following this maneuver, the surgeon then is able to expose the medial and dorsal aspects of the first metatarsal head as shown in Fig. 32-7, C. Based on the preoperative x-ray and a preoperative template, if constructed, the surgeon is able to determine how much of the medial eminence of the metatarsal head needs to be removed as seen in Fig. 32-11, B. Once the medial eminence has been removed, the surgeon can use a sterile marker and create the proposed osteotomy site. At this time and before performing the osteotomy, the surgeon decides whether to perform a lateral release of the first MTPJ or remove the fibular sesamoid bone; then further dissection is performed in the first interspace as shown in Fig. 32-7, D. Some surgeons elect to perform this maneuver through a second incision over the dorsal aspect of the first interspace. This portion of the procedure is performed to release any abnormally tight soft tissue structures that are holding the hallux in the abductus position. Using some type of power instrumentation, the bone is cut completely through from medial to lateral, severing all cortical surfaces as shown in Fig. 32-11, C. Then based upon the surgeon’s evaluation of the preoperative x-ray and/or preoperative template, the metatarsal head is transposed laterally toward the second metatarsal by a certain number of millimeters. Once the metatarsal head has been transposed to the desired amount, the osteotomy site is fixated based upon the surgeon’s preference and the medial overhang of bone on the metatarsal shaft is removed flush. Fig. 32-11, D is a postoperative radiograph in which the osteotomy site was fixated with absorbable rods, which are radiolucent. Fig. 32-11, E and F, are postoperative radiographs in which the osteotomy site for this type of procedure was fixated with two cannulated screws.

Once fixation is completed, the structural component now has been corrected. The next portion of the procedure is the completion of the soft tissue rebalancing. In this specific example an inverted “L” capsulotomy was performed medially. The surgeon’s assistant holds the hallux into a corrected position on the transverse plane, and the surgeon can then appreciate how much redundant medial capsular tissue is present. This medial redundant tissue is excised and the medial capsule closed using suture material of the surgeon’s preference (see Fig. 32-7, E). The dorsal portion of the capsule is then closed again using suture material of the surgeon’s preference. Some surgeons will elect to close the subcutaneous tissues and others will insert several buried knot sutures in the dermal layer to take the tension off the skin before skin closure. Skin closure is accomplished usually with a nonabsorbable material, again based on the surgeon’s preference.

Bandages are applied in such a manner as to control postoperative edema and reinforce the soft tissue realignment of the first MTPJ. The patient is placed either in a surgical postoperative shoe or a removable walking boot. Both devices allow for the patient to begin immediate ambulation with elimination of the propulsive phase of gait, which is needed because of the osteotomy procedure.