Hallux valgus, commonly known as a bunion, is a complex and often painful deformity of the forefoot characterized by the lateral deviation of the great toe (hallux) and medial deviation of the first metatarsal. This progressive condition can lead to significant discomfort, difficulty with footwear, and a diminished quality of life. While conservative management offers relief for some, surgical intervention remains the definitive solution for correcting the underlying structural pathology. Among the plethora of surgical techniques developed over the decades, the Chevron osteotomy has emerged as a cornerstone procedure, renowned for its stability, versatility, and predictable outcomes for a specific and common patient population. This essay will explore the anatomical basis of hallux valgus, the rationale and technique of the Chevron osteotomy, its indications and limitations, and its enduring role in the foot and ankle surgeon’s armamentarium.
The pathoanatomy of hallux valgus is multifactorial, involving a biomechanical breakdown at the first metatarsophalangeal joint (MTPJ). The deformity is not simply a “bump” on the side of the foot; rather, it is a tri-planar deformity consisting of lateral deviation of the proximal phalanx (valgus), medial deviation of the first metatarsal (primus varus), and, frequently, rotation (pronation) of the hallux. This misalignment places abnormal tensile forces on the medial soft tissues and compressive forces on the lateral structures, leading to the prominent, inflamed medial eminence colloquially known as the bunion. Over time, the medial joint capsule becomes stretched, the lateral structures contracted, and the sesamoid apparatus, which is vital for weight-bearing, becomes subluxed laterally. The goal of any corrective surgery is to realign the first ray, restore joint congruity, and rebalance the soft tissues, thereby alleviating pain and restoring function.
The Chevron osteotomy, first described by Corless in 1976 as a modification of an earlier procedure, is a distal first metatarsal osteotomy distinguished by its unique V-shaped cut. The name “chevron” is derived from the military insignia and heraldic symbol, reflecting the inverted ‘V’ configuration of the bone cut. The primary biomechanical principle behind this osteotomy is its inherent stability. The shape of the cut creates a large, cancellous bone surface area for healing and, crucially, provides excellent intrinsic stability against dorsal and plantar displacement due to the interlocking nature of the two bone fragments. This stability is a significant advantage over some linear osteotomies, which may require more rigid internal fixation and are prone to displacement.
The surgical technique is precise and methodical. Through a medial incision over the first MTPJ, the surgeon exposes the medial eminence. The prominent portion of the medial metatarsal head is resected, but care is taken to preserve the sagittal groove, a critical landmark for the sesamoid apparatus. The apex of the V-shaped osteotomy is centered within the metatarsal head, typically about 5-10mm from the joint surface. The two arms of the ‘V’, each usually angled at 60 degrees, are then carefully created with a oscillating saw, directed proximally. The capital fragment (the metatarsal head) is then manually translated laterally, effectively reducing the intermetatarsal angle between the first and second metatarsals. This lateral shift of the head recenters the sesamoids beneath it and realigns the articular surface of the metatarsal head with the proximal phalanx. The displaced fragment is typically fixed with a single, small compression screw or a bioabsorbable pin, which provides rotational control and enhances the already favorable stability of the construct. Any remaining medial prominence is smoothed, and the medial joint capsule is tightened (medial capsulorrhaphy) to secure the correction.
The key to the success of the Chevron osteotomy lies in its appropriate application. It is predominantly indicated for mild to moderate hallux valgus deformities, generally defined by an intermetatarsal (IM) angle of less than 15 degrees and a hallux valgus angle of less than 40 degrees. It is an excellent choice for younger, active patients with good bone quality, as the osteotomy is performed within the cancellous bone of the metatarsal head, which has a rich blood supply and heals reliably. The procedure’s ability to correct the deformity while preserving the motion of the first MTPJ is another significant benefit, making it a joint-preserving operation.
However, the Chevron osteotomy has its limitations, and recognizing them is paramount to avoiding poor outcomes. It is generally contraindicated for severe deformities with a high IM angle, as the amount of lateral translation achievable is limited by the width of the metatarsal shaft. Attempting to over-correct a severe deformity can lead to instability, malunion, or avascular necrosis (AVN) of the metatarsal head. AVN is a rare but serious complication, theorized to result from the disruption of the intraosseous blood supply during the osteotomy, particularly if the dorsal or plantar capsular attachments are violated. The procedure is also less suitable for patients with significant joint arthritis (hallux rigidus), as it does not address the degenerative changes within the joint itself. In these cases, an arthrodesis (fusion) may be a more appropriate option.
The evolution of the Chevron technique demonstrates its adaptability. Surgeons have developed modifications to extend its utility. The long-arm Chevron, for instance, involves a more proximal apex and longer limbs, allowing for greater lateral translation and thus addressing moderately severe deformities more effectively. Furthermore, the addition of an Akin osteotomy (a medial closing wedge osteotomy of the proximal phalanx) can be performed concurrently with the Chevron to correct any residual hallux valgus or pronation deformity of the toe itself, creating a powerful double correction for complex presentations.
The Chevron osteotomy remains a vital and enduringly popular procedure in the surgical management of hallux valgus. Its design, which masterfully balances the competing demands of effective correction and structural stability, has stood the test of time. For the patient with a mild to moderate bunion deformity, it offers a reliable path to pain relief, improved foot alignment, and a return to normal activity with a low complication profile. While not a panacea for all bunion types, its clear indications, proven biomechanical advantages, and potential for modification solidify its status as a fundamental and indispensable technique. As with all surgical interventions, its success hinges on the surgeon’s meticulous technique and, most importantly, the careful selection of the right patient for the right procedure. In the pantheon of bunion corrections, the Chevron osteotomy rightly holds its place as a gold standard.