Hallux valgus- Lateral MTP joint release ( modified McBrides procedure)

The Hallux valgus deformity to be corrected with a first metatarsal osteotomy.
The first step will be a modified McBrides.

The 1st MTP joint is identified by moving it. Access is required to lateral aspect of the joint for the release to be performed.

The placement of the skin incision should in most cases be close to the lateral aspect of the 1st metatarsal head and at the level of the joint.
This placement avoids excessive dorsal soft tissue dissection in gaining access to the deeper structures.
If however the second MTP is to be accessed (eg for a Weils osteotomy) then the incision should lie midway between first and second metatarsals.

The knife dissection should just be through the skin to the fat layer.
A pair of fine tenotomy scissors are then taken up to blunt dissect the fat layer with the objective of defining the well defined fascia that overlies the first dorsal interosseous muscle.

There is often a branch of the deep peroneal nerve in the fat layer that can be preserved.
Beneath is the fascia overlying the interosseous muscle. A Wests’ retractor is useful to put the soft tissues under tension and assist in defining this soft tissue plane.

The superficial fat should be swept off the tougher, underlying fascial layer

A knife is used to open the fascia once its extent has been defined, to reveal the interosseous muscle beneath

The fascia needs to be released distally as far as it extends into the first web space and proximally slightly beyond the level of the MTP joint .
The purpose of this is to allow an adequate mobilisation of the underlying muscle to reveal the lateral aspect of the joint.

The interosseous muscle is freed from the lateral aspect of the 1st metatarsal by blunt or sharp dissection.
The Wests retractor can next usefully be placed beneath the medially freed margin of the interosseous to sweep it laterally and expose the lateral and plantar aspect of the 1st MTP joint.

The lateral aspect of the joint capsule is now easily seen
The neuro-vascular bundle sits in the plantar aspect of the exposure and need not be approached.

A better view of the deep aspect of the first web space prior to deep soft tissue releases for the lateral release.
The thick capsule of the first MTP joint (1) into which attaches the adductor muscle(2). The adductor is usually not this well defined.
The blue line (4)indicates the more superficially located and now detached superficial fascia.
(3) indicates the transverse metatarsal ligament.

A horizontal capsulotomy is performed at the level of the MTP joint and placed just above the lateral sesamoid.
If made in the correct position synovial fluid should be immediately seen. There is also a loss of resistance as one passes into the joint with the knife.
If not correct a second parallel incision should be made a few mm above or below the initial incision.

With the capsulotomy correctly located for the lateral release the articular surface of the lateral sesamoid can easily be seen. A McDonalds is useful to probe the joint open and confirm the location of the sesamoid.

The adductor insertion is dissected off the sesamoid. This sharp dissection should release muscle fibres proximally, extend plantar-wards (but not to the plantar surface of the sesamoid) and exit with a lateral cut distally through the sesamo-phalangeal ligament(a non-discreet condensation of the capsule between the sesamoid and base of proximal phalanx .

The lateral directed cut through the sesamo-phalangeal ligament is aided by stressing the MTP joint at this stage into varus. The cut is lateral at the level of the joint just and distal to the sesamoid.
Following this stage of the lateral release the MTP should be stressed into varus. Ten degrees beyond neutral indicates an adequate lateral release has been performed.

More frequently a further release is required to allow the joint into varus. This is performed by adding a vertical limb to the capsulotomy.
In large deformities especially care should be taken with the superior extent of this cut which may come close to the extensor tendons which will sit lateral to the dorsal aspect of the joint.
The cut starts at the distal extent of the sesamoid and is extended superiorly at the level of the MTP joint.

The articular surface of the sesamoid is clearly seen (1) as is its lateral aspect, now freed of the insertion of the adductor (2).
The sesamo-phalangeal ligament (3) has also been sectioned.

An appropriate amount of resulting MTP joint mobility is demonstrated.

The wound is closed with a 2.0 Vicryl followed by a 3.0 Vicryl subcuticular suture.