Point-Counterpoint: Is A Lateral Release Necessary For Hallux Valgus Correction?
- Volume 25 - Issue 4 - April 2012
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Appreciating The Impact Of Biomechanical Imbalances
The reverse buckling of the hallux on the metatarsal head accentuates the intermetatarsal increase. Most of us clearly understand the general biomechanical instability of the medial column and first ray.
However, the biomechanical tendencies that contributed to the hallux abducto valgus can change during the surgical intervention itself. The adaptive contracture of the lateral soft tissues progressively pulls the phalanx into varying degrees of abduction and valgus/pronation. As this occurs, the base of the phalanx reverse buckles the intermetatarsal angle open even further. We intuitively know this from converse observations in intermetatarsal angle reduction after Keller bunionectomies and even true McBride procedures and first MPJ fusions. These are all cases in which no first metatarsal osteotomy occurred at all.
Indeed, the literature has shown that an effective lateral release itself can reduce the intermetatarsal angle between 2 and 5 degrees.1-3 This mandates continued intraoperative assessment as to the type of osteotomy and quantity of osseous correction required for further reduction of the intermetatarsal angle. In a sense, “as the phalangeal base goes, so go the sesamoids” via their insertion to the phalangeal base. Yet we know that the sesamoids remain immobile and it is the metatarsal head that becomes relocated over the sesamoid apparatus.4
So what should constitute a “lateral release” as an accepted definition for a debate of its merits? All that is required in the greatest preponderance of cases is a release of the fibular sesamoid or suspensory ligament, and the portion of the conjoined adductor/flexor hallucis brevis tendon between the lateral sesamoid and the base of the proximal phalanx. Those very structures are pulling the toe laterally or blocking the metatarsal head from relocating back over sesamoids. One should decide on the amount and necessity of such releases on a case by case basis for effective and reliably lasting correction of the deformity.
Pertinent Insights On Congruence, Cadaveric Correlation And Clinical Confirmation
A congruent joint is by definition not displaced so why would a lateral release be required? These are those infrequent cases of bunions that truly may not need a lateral release at all. However, incongruent joints are more the norm with hallux abducto valgus and have multiple static and dynamic anatomic components. The first metatarsal head drifts medially, thus increasing the angle between the first and second metatarsals. The transverse metatarsal ligament holds the sesamoid complex in place and thus becomes relatively laterally positioned as the metatarsal head displaces medially.
With a progressive deformity, the axis of pull for the adductor hallucis, the flexor hallucis brevis, the extensor hallucis longus and the abductor hallucis become lateralized, which dynamically contributes to the lateral displacement of the great toe. The medial joint capsule and ligaments become attenuated whereas the lateral joint capsule and ligaments become contracted. Ideally, an analysis of the amount of incongruence of the first MPJ and the amount of tension in the lateral soft tissue structures that is causative would allow us to tailor the amount of lateral release required for the case at hand.2
Hromadka and colleagues demonstrated on 30 cadaveric specimens with hallux valgus deformity that 90 percent required only a partial release of the conjoined lateral tendon and full release of the lateral fibular sesamoidal ligament to realign the joint.5 The authors considered less than 15 degrees of hallux abduction to be physiologic with simulated weightbearing and the fibular sesamoid relocated under the metatarsal head.