As orthopedic surgery continues to head in the direction of less invasive surgical techniques, this article explores the application and evolution of minimally invasive/percutaneous techniques in the surgical correction of hallux valgus deformities. Modern techniques are described and available literature is reviewed.

Keywords

Hallux valgus

Bunion

Minimally invasive

Percutaneous

MICA

Chevron

Key points

Introduction

During the past 20 years, surgery has seen an inexorable trend toward less invasive and keyhole approaches. For instance, in the field of general surgery, laparoscopic cholecystectomy and appendicectomy have become firmly established as the surgical gold standards. If an equivalent technical result to an open surgical procedure is possible to achieve with a safe but less invasive approach, then better patient outcomes ought to follow, and the profession should continue to strive in this direction.

Orthopedics has not been left behind in this less invasive evolution. Arthroscopic ankle cheilectomy and arthroscopic ankle fusion are replacing open approaches. However, minimally invasive hallux valgus surgery has been slower to establish. In fact, the number of proposed open procedures to treat this condition continues to increase. However, the Arbeitsgemeinschaft für Osteosynthesefragen (AO) group's principles of minimizing soft tissue trauma and periosteal stripping are just as relevant to hallux valgus surgery as they are to fracture management.

Perhaps this reluctance to embrace minimally invasive techniques in hallux valgus correction is partly explained by the general perception that bunions are “easy to do and easy to get wrong.”

In fact, a literature review shows that approximately 85% of patients report good outcome after open hallux valgus correction. Analysis of the remaining 15% reveals frequent issues with stiffness and pain related to the soft tissues rather than purely osteotomy issues. Thus, perhaps the key to improving outcome after hallux valgus surgery lies in a less invasive soft tissue approach rather than which of the myriad described osteotomies is used. That said, early minimally invasive techniques failed to adhere to the AO principles of rigid internal fixation and early mobilization and have been associated with poor outcomes, adding fuel to concerns that “minimally invasive” equates to “easier to get it wrong.”

Principles of minimally invasive surgery

The term minimally invasive refers to the skin incision/approach, not the type of osteotomy used. Despite this, several disparate operations using minimally invasive techniques are frequently grouped together under the “minimally invasive” banner in a way that does not make sense and does not occur when referring to open techniques. The ability to differentiate between different techniques is important for meaningful and rational comparison to be made.

Evolution of minimally invasive first metatarsal osteotomies

Less invasive procedures were promoted by Wilson1 and Bösch and colleagues2 in the 1980s. The latter was a more percutaneous approach and used a subcapital Hohmann osteotomy3 through a short vertical incision at the level of the neck of the metatarsal. However, the first truly minimally invasive technique to gain prominence was a modification of the Reverdin osteotomy4 developed by Stephen Isham5 published in 1985 (and more recently popularized by Mariano De Prado in Spain).6 Isham5 developed a modification of the Shannon burr with end and side cutting performance to perform an oblique medial closing wedge osteotomy of the head of the first metatarsal. The osteotomy was extra-articular but intracapsular. He combined this with a minimally invasive Akin operation, bunionectomy, and adductor release. He believed that this construct was sufficiently stable that no internal fixation was required, and used postoperative rehabilitation as for a minimal incision Silver-Akin procedure, using postoperative splint dressings to stabilize the correction.

Isham and Nunez7 stated that a marked improvement of short-term and long-term results were immediately apparent. However, although these investigators acknowledge that the average shortening is 5 mm and that this can be greater, they do not describe any related complications.

The lack of fixation and the degree of shortening inherent in this procedure are causes for concern, and the results have not been reproduced8 despite the large-scale uptake by podiatrists in the United States in the 1970s to1990s. In fact, sparse independent literature exists on the Reverdin-Isham procedure.

Perhaps because of poor experiences associated with these early minimally invasive techniques,9 little interest has been shown in minimally invasive surgery in the United States in recent years. The next stage of development has occurred in Europe, where several centers have been developing minimally invasive techniques and showing positive results with reduced inpatient stay and better recovery,10 which has served to reignite interest and add momentum to the evolution.

The Bosch osteotomy has regained interest in Europe and was popularized by Magnan and colleagues11,12 and Giannini and colleagues,13 who called his modification the SERI (Simple, Effective, Rapid, Inexpensive). Excellent results with full correction, mean American Orthopaedic Foot & Ankle Society (AOFAS) scores of 91.8, and no significant complications have been published,14 even at 10-year follow-up.15 However, it is concerning that these procedures use an inherently unstable vertical osteotomy at the level of the neck, which is splinted by a single K-wire (passed through the soft-tissues of the medial hallux and then run down the medullary canal of the metatarsal) rather than rigidly internally fixed.

Independent analyses of this technique have generally failed to reproduce good results,16 even with a second K-wire to transfix the osteotomy.17 In a prospective study, Kadakia and colleagues9 reported almost universally poor results even at short-term follow-up, with some patients experiencing major complications, such as dorsal malunion (70%), recurrence (40%), osteonecrosis, and wound complications. The investigators discontinued the study after only 3 months because of the magnitude and frequency of the complications observed.

Minimally invasive Chevron-Akin

The wish to pursue the sound (AO) principles of modern fracture fixation must lead not only in the direction of less invasive (or perhaps better described as less disruptive) soft tissue surgery but also toward stable internal fracture fixation. Thus, applying this to hallux valgus surgery, the objective should be to achieve an accurate and controllable osteotomy with stable internal fixation without compromising the soft tissue envelope of the fracture or adjacent hallux metatarsophalangeal joint (MTPJ). It is from these objectives that the minimally invasive Chevron-Akin (MICA) has been proposed. Developed by Joel Vernois and David Redfern in the United Kingdom,18 this technique involves the use of percutaneous surgical techniques to create a chevron-type osteotomy at the level of the distal diaphyseal-metaphyseal junction of the first metatarsal and an Akin-type osteotomy of the hallux proximal phalanx, both of which are internally fixed with compression screws and combined with a percutaneous distal soft tissue release.

The MICA technique is the first minimally invasive hallux valgus correction technique to truly marry the perceived advantages of an extracapsular first metatarsal osteotomy in which the fracture soft tissue envelope is preserved with rigid...