Modified McBride’s Bunionectomy

John Campbell

Abstract

Modified McBride’s bunionectomy is a useful procedure for the correction of hallux valgus (bunion). Although it was originally described as an isolated technique, it is much more commonly performed in conjunction with proximal metatarsal osteotomy or tarsometatarsal arthrodesis in contemporary practice. A key goal of the procedure remains correction of the abnormal anatomy and mechanics while sparing the metatarsophalangeal joint and maintaining motion. Principles of the procedure include distal soft-tissue correction and balancing of the hallux metatarsophalangeal joint along with resection of the medial eminence. This requires release of the contracted lateral tissues, including the adductor hallucis tendon, intermetatarsal ligament, and lateral joint capsule. The medial eminence is removed, and a medial capsular imbrication removes redundant tissue and helps align the joint. Meticulous surgical technique is necessary to ensure good outcomes. This includes careful balancing of the soft tissues, avoidance of excessive removal of the medial eminence to prevent iatrogenic hallux varus, and minimizing capsular stripping to prevent osteonecrosis. Good clinical results can be expected in cases of flexible hallux valgus with mild to moderate deformity.

Keywords: bunion, hallux valgus, bunionectomy, McBride’s procedure, distal soft-tissue correction

7.1 Indications

• A refinement of Silver’s original bunionectomy procedure from 1923,¹ later modified by McBride.²^–⁴

• Contemporary technique traces back to Mann and Coughlin,⁵ who modernized McBride’s and DuVries’ method including two incisions.

• Relies on correction of abnormal anatomy and mechanics without joint destruction/ablation.¹^–³

• Can be used in isolation for mild to moderate hallux valgus and flexible deformity.

• Can be used for moderate to severe hallux valgus with flexible deformity in conjunction with proximal first metatarsal osteotomy or first tarsometatarsal (TMT) arthrodesis⁵^–⁷ (Chapters 9, 11, and 20).

7.1.1 Clinical Evaluation

• Determine location of tenderness.

• Assess range of motion of hallux metatarsophalangeal (MTP) joint.

• Determine flexibility/reducibility of hallux MTP joint.⁴

• Identify hypermobility of the first TMT joint.

• Assess lesser toe deformities.

• Confirm intact pulses and sensory function of the foot.

7.1.2 Radiographic Evaluation

• Weight-bearing radiographs of the affected foot, including anteroposterior, oblique, and lateral views.

• Identify degree of hallux valgus deformity, including

Congruent versus incongruent (subluxed) deformity (Fig. 7.1).

Measurement of hallux valgus angle (HVA), first/second intermetatarsal angle (IMA), and distal metatarsal articular angle (DMAA).

Presence of hallux MTP arthritis.

Assess lesser toe deformities.

7.1.3 Nonoperative Options

• Low-heeled, wide toe-box shoes.

• Foam or silicone gel spacers or pads.

Fig. 7.1 (a) Congruent hallux valgus and (b) incongruent hallux valgus, with subluxation of the joint.

• Custom-molded orthotic insoles.

• Nonsteroidal anti-inflammatory medications.

• Avoidance of activities or shoes that exacerbate symptoms.

7.1.4 Contraindications

• Active infection of the foot.

• Severe peripheral vascular disease.

• Psychiatric disease, noncompliant patient.

• Congruent hallux valgus deformity (would cause subluxation or incongruence of joint).

• Severe hallux valgus deformity: IMA > 14 to 15 degrees; HVA > 30 to 40 degrees.⁵^–⁷

• Rigid deformity or end-stage arthritis of MTP joint (better treated with arthrodesis).²

• Underlying inflammatory arthritides or neurologic disorders with high chance for recurrent deformity, e.g., rheumatoid arthritis, gout, cerebral palsy, spasticity (better treated with arthrodesis).

7.2 Goals of Surgical Procedure

• Release of contracted lateral structures—adductor hallucis tendon, transverse metatarsal ligament, and lateral capsule (Fig. 7.2).

• Removal of medial eminence.

• Imbrication of medial soft tissues.

• Reduction of HVA and IMA.

• Improved congruence of MTP joint.

Fig. 7.2 Contracted lateral structures contributing to hallux valgus deformity; lateral slip of the flexor hallucis brevis inserting on the fibular (lateral) sesamoid; transverse metatarsal ligament between first and second MTP capsules; oblique and transverse slips of the adductor hallucis muscle inserting onto fibular sesamoid and lateral MTP capsule.

7.3 Advantages of Surgical Procedure

• Important technique in the foot surgeon’s armamentarium.

• Technically facile and easily learned.

• Can be performed alone or in combination with proximal bony procedures based on the severity of deformity.⁵^,⁷

7.4 Key Principles

7.4.1 Dorsal First Web Space Incision

• Release of adductor hallucis (conjoined) tendon.¹^–⁷

• Release intermetatarsal ligament.

• Incise suspensory (metatarsosesamoid) ligament.

• Stab incisions lateral capsule.⁴

• Suture adductor tendon stump into lateral capsule/periosteum on metatarsal head,²^–⁷can also place sutures between first and second MTP capsules to close down IMA.⁵^,⁷

• McBride’s original technique of fibular sesamoidectomy and aggressive release of the lateral slip of the flexor hallucis brevis tendon²^–⁴ is no longer performed to avoid iatrogenic hallux varus.⁸

7.4.2 Medial Midline Incision⁵^,⁷

• Medial bursectomy and capsulotomy.¹^–⁵^,⁷

• Medial eminence resection.¹^–⁵^,⁷

• Reduction and capsular repair.¹^–⁵^,⁷

7.5 Preoperative Preparation and Patient Positioning

• Use of general anesthesia or regional block with intravenous sedation. Prophylactic antibiotics are administered.

• The patient is positioned supine on the operating room table with use of a thigh, calf, or ankle tourniquet. The operative limb should be freely movable to allow access to the dorsal and medial aspects of the foot.

7.6 Operative Technique (Author’s Preferred Method)

• The dorsal web space between the first and second metatarsals is approached initially. The skin incision is created centrally in the web space and is followed by spreading of the subcutaneous tissues with scissors. Care should be exercised to avoid injury to the terminal branches of the deep peroneal nerve to the hallux and second toe. Thick bursal tissue may be encountered between the first and second metatarsal heads and should be dissected bluntly. A laminar spreader is useful to distract the first and second metatarsals to ensure good visualization of the deep structures of the web space.

• The adductor hallucis tendon is visualized inserting on the lateral aspect of the first MTP joint capsule and fibular sesamoid. The tendon has an oblique slip in addition to a transverse component. A pointed #11 scalpel blade is useful to meticulously release the tendon insertion on the capsule without excessive damage to the deeper structures (Fig. 7.3). Once the tendon insertion is released, scissors can be used in a proximal direction to ensure complete release of the tubular tendon. At the completion of the procedure, the stump of the released adductor hallucis tendon is sutured to the lateral capsule and periosteum of the metatarsal head with one or two 2–0 absorbable sutures to assist in correcting varus of the first metatarsal.

• Next, scissors are used to free both above and deep to the transverse metatarsal ligament between the first and second metatarsal heads. Care is taken to avoid injury to the deeper neurovascular structures. The ligament is then incised in a longitudinal direction with scissors, ensuring complete release (Fig. 7.3). The #11 scalpel blade can be used to create a longitudinal incision through the suspensory ligament, connecting the MTP capsule to the fibular sesamoid. Care is taken to avoid injury to the chondral surface of the sesamoid. Use of a Freer elevator to gently pry open the sesamoid articulation can allow exposure and facilitate complete release with the scalpel both proximally and distally.

• Release of the contracted lateral capsule is then carried out with the scalpel. In the majority of cases, multiple vertical stab cut incisions can be created in a “pie crust” manner to release the capsule. Gentle manipulation of the toe into varus can stretch the lateral capsular fibers. It is helpful to try to obtain at least 10 to 15 degrees of varus of the toe to ensure good release. In cases with severe lateral contracture, a more formal vertical lateral capsular incision may be necessary in order to minimize the risk of recurrence.

• A medial midline longitudinal incision is fashioned over the hallux MTP joint. The dorsal and plantar flaps are carefully elevated to allow full access and exposure to the capsule, with care taken to avoid injury to the dorsal cutaneous nerve to the hallux. Removal of the medial bursa is performed with scissors. Several different capsulotomy incisions have been described (Fig. 7.4). The author prefers an L-shaped capsulotomy with the vertical limb at the level of the joint line and the horizontal limb along the dorsal edge of the metatarsal head (Fig. 7.4a). This leaves the proximal capsular fibers attached near the first metatarsal neck and shaft. This flap is carefully elevated off the medial eminence in a full-thickness manner. It is important to extend the vertical limb plantarly to the tibial sesamoid to ensure adequate release and subsequent correction, while avoiding injury to the plantar nerve to the hallux in the plantar flap.

One alternative capsular incision involves a medial longitudinal capsulotomy in the midline (Fig. 7.4b). The dorsal and plantar flaps are carefully elevated off the medial eminence; at the completion of the procedure, a small wedge or V-shaped portion of capsule can be removed from the plantar flap, allowing side-to-side closure. Another alternative involves a V-, Y-, or chevron-shaped capsular incision (Fig. 7.4c), which allows advancement and imbrication at the time of closure to correct position of the toe.

• The medial eminence resection can be performed with either a power saw or a chisel at the surgeon’s preference. This is typically performed after any proximal metatarsal osteotomy or first TMT arthrodesis is performed. The medial eminence resection is aligned parallel with the medial border of the foot. In order to avoid excessive bone resection and a potential for iatrogenic hallux varus, the author prefers to start the saw or chisel cut 1 mm medial to the sagittal groove on the metatarsal head with the exit point on the metatarsal neck flush with the diaphyseal bone (Fig. 7.5). The bony surface can be smoothed of any sharp edges using a synovial rongeur or small bone rasp.

• The hallux can be reduced to a congruent position on the metatarsal head and checked under fluoroscopy. Redundant medial capsular tissue can be sharply excised with a scalpel blade. The capsulotomy is then closed in side-to-side fashion with multiple figure-of-eight stitches using 2–0 absorbable suture to balance the soft tissues and maintain reduction of the joint (Fig. 7.6).