As we all know, in hallux varus, the first metatarsal assumes a medially deviated position and moves closer to the midline of the body. A purely transverse plane deformity, hallux varus is the most common complication of hallux valgus surgery.1 The reported incidence ranges from 2 to 17 percent.2
Congenital hallux varus is typically due to connective tissue disorders (i.e. Marfan syndrome and Ehlers-Danlos syndrome) or is associated with Down syndrome and neuromuscular disorders (i.e. cerebral palsy).2
Acquired hallux varus most commonly arises following surgical correction of a bunion deformity but can result from trauma in which the lateral structures are disrupted.1-3
Note that the severity of the condition depends on the inherent flexibility of the deformity, the time elapsed from the initial surgery, the degree of musculotendinous imbalance, the amount of structural malalignment and any other underlying disorders.2
Taking a closer look into the surgically produced hallux varus, there are a handful of factors that can lead to the deformity. These factors include:1,2
• overplication of the medial joint capsular tissue;
• medial displacement of the tibial sesamoid;
• over-pull of the abductor hallucis muscle against a weakened or absent adductor hallucis/ligamentous structure;
• overcorrection due to osteotomy or a post-op dressing;
• excessive resection of the medial prominence (aka staking the metatarsal head); and/or
• removal of the fibular sesamoid (McBride procedure) was originally the most common culprit.1,2
These etiologic factors are not always evident intraoperatively. One should take steps during the corrective bunion procedure to reduce the chances of hallux varus but unfortunately, there is no specific measurement to know if you have successfully avoided a hallux varus deformity.
The type of treatment depends on the severity of the deformity and whether it is a fixed or flexible deformity.4 Given that one cannot reduce a fixed deformity by passive manipulation, surgeons can best correct the deformity by soft tissue and osseous measures. A flexible deformity is susceptible to passive reduction and surgeons often correct it by soft tissue types of procedures only. A mild form of hallux varus with 7 to 10 degrees of deviation is usually flexible and painless, and typically does not need corrective measures.3 More severe forms may require anything from soft tissue releases to a reverse osteotomy.
Soft tissue release. If surgeons accidentally over-tighten the medial capsular structures, all that may be needed is a release of those tissues and a more loose approximation.
Tendon transfers. There are multiple ways of performing this with several possible tendinous structures. The goal of the tendon transfer is to relocate the tendon to an area that will produce the opposite effect and reduce the hallux varus. There are several types of tendon transfers.
• Abductor hallucis tendon transfer. The ideal deformity for use of this type of transfer is one in which there is little to no metatarsal deformity and medial deviation of the hallux is less than 30 degrees.4 One transfers the tendon to the lateral aspect of the base of the proximal phalanx to pull the toe to neutral or slight abduction.
• Extensor hallucis longus transfer. The idea of this transfer is to direct the extensor hallucis longus, a major deforming force, to the lateral side of the toe.1,5 A necessary adjunctive procedure in this transfer is to fuse the interphalangeal joint of the hallux to prevent a hammertoe type of deformity. You can either take the entire tendon or half. This procedure is effective in 80 percent of patients.1,5
• Extensor hallucis brevis transfer. The difference between this transfer and the extensor hallucis longus is that this one acts more like a static restraint from the deforming forces while the extensor hallucis longus is more of a dynamic restraint.6 In a study by Myerson, using the extensor hallucis brevis also reduced the stiffness at the metatarsophalangeal joint that typically occurs with the extensor hallucis brevis transfer.6
Osseous procedures. The idea behind any type of bone work is to make your cuts in the opposite fashion as you did from the original surgery. There are several ways to do this. The main point is that osteotomies are required for a rigid varus deformity.
There is no way to completely avoid hallux varus. While we can perform a corrective bunion surgery and the steps/tips to reduce the risk of a varus deformity, we should caution patients that, as in life, nothing is absolute. Diagnosing a hallux varus early is paramount in minimizing the type of correction needed.
1. Thordarson D. Foot and Ankle, second edition. Lippincott, Williams and Wilkins, Philadelphia, 2012.
2. Banks AS, Downey MS, Martin DE, Miller SJ (eds.) McGlamry’s Comprehensive Textbook of Foot and Ankle Surgery, volume 1, first edition. Lippincott, Williams and Wilkins, Philadelphia, 2001.
3. Coughlin MJ, Mann RA, Satlzman CL (eds.) Surgery of the Foot and Ankle, volume 1, eighth edition. Mosby, Philadelphia, 2007.
4. Allen PG, Schon L. Hallux varus: correction with the abductor hallucis tendon transfer and suture button construct insertion. Techniques Foot Ankle Surg. 2009; 8(4):194-99.
5. Johnson KA, Spiegl PV. Extensor hallucis longus transfer for hallux varus deformity. J Bone Joint Surg. 1984; 66A(5):681-6.
6. Myerson MS, Komenda GA. Results of hallux varus correction using an extensor hallucis brevis tenodesis. Foot Ankle Int. 1996; 17(1):21-27.