Essential Insights On Hallux Valgus
Since the introduction of the Austin procedure, surgeons have noticed that modifications that shorten and plantarflex the first metatarsal, and allow reduction of the proximal articular set angle facilitate better MPJ motion. This is due to the resultant joint decompression and reduction of dorsal jamming from the head being dropped down and the realignment of the hallux with its metatarsal.
Correction of the proximal articular set angle (PASA) should be the primary goal that drives procedure selection. Adaptation of the first metatarsal head to the functional position of the hallux is what creates the PASA. Realigning the deviated metatarsal’s articular surface to its new functioning position should be the first priority when reducing the deformity. Then one can reduce the IM angle. Since PASA reduction provides relative lengthening of the metatarsal, one needs to perform some type of decompression procedure as well. This involves first metatarsal shortening and, preferably, concurrent plantarflexion of the metatarsal head to prevent its elevation.
Except in extreme cases, one can stabilize hypermobility of the first ray by joint decompression and reduction of the PASA and IM angle. The first ray (navicular, cuneiform and first metatarsal) cannot be stabilized in the transverse plane with a metatarsal-cuneiform fusion. Truly hypermobile first rays would present as a metatarsus primus elevatus on weightbearing radiographs with a navicular-cuneiform ptosis. This would require a navicular-cuneiform fusion of some type if the deformity is very flexible or rigid. If such a deformity exists for the first metatarsal-cuneiform joint, then it would need to be fused for stability. Transverse plane widening of the interspace between the first and second metatarsal bases (IM angle) will reduce without fusion.
Functional hallux limitus with or without metatarsus primus elevatus is a component of almost every case of hallux abducto valgus. When evaluating a bunion deformity, one should load the first ray and put the first MPJ through a range of motion. Upon dorsiflexion, the joint will invariably jam, either preventing further dorsal migration (look for a hallux extensus) or causing further dorsiflexion through a valgus rotation of the hallux. In both cases, one needs to decompress and plantarflex the first metatarsal joint. If there is a remaining valgus rotation with the joint loaded, then one would likely need to excise the fibular sesamoid.
Why I Prefer The Modified Weil Osteotomy
I could live with any or all combined procedures that address these five points. The best of all worlds would be one that accomplishes most of these goals easily with the least risk of complication and the quickest recovery for the patient.
I have accomplished this via a modified Weil osteotomy through the first metatarsal head in an oblique fashion from dorsal-distal to plantar-proximal.
Before the osteotomy, make a medial, curvilinear capsulotomy, allowing exposure of the metatarsal head for resection of the medial eminence. Following the osteotomy, reduce the head of any PASA and then translocate the head laterally to reduce the IM angle. Some shortening has to occur here for joint decompression. This osteotomy allows plantarflexion with concurrent shortening for decompression. However, one should only allow enough shortening to preserve a normal amount of dorsiflexion without jamming the joint. Excessive shortening can cause the hallux to remain dorsiflexed, preventing adequate toe purchase on the ground due to concurrent plantarflexion of the head.