Bunionette correction with short Scarf osteotomy

Pre-operative appearance of the Bunionette
Very obvious soft tissue swelling at the joint and clinically there seems a fair degree of lateral angulation of the metatarsal shaft from its midpoint distally (though this has of course been confirmed with a pre-operative Xray)
In this case there is no evidence of varus deviation at the 5th MTP joint
There is also no inter-current Hallux Valgus.

A lateral and mid-line skin incision over the prominence.
It does not need to extend to far distally beyond the MTP joint and can it in general at most taken proximally to the midpoint of the 5th metatarsal shaft.
Once the skin is cleanly cut use a pair of tenotomy scissors to mobilise the skin and attached fat from the deeper layers.

The fat layer should be blunt dissected through sufficiently to allow identification of the margins of the Metatarsal shaft. As with all Orthopaedic surgery it is worth taking a moment to see if any cutaneous nerves are immediately in the plane of dissection and can be avoided. The lateral aspect of the 5th toe gets its cutaneous innervation from terminal branches of the Sural nerve. The dorsomedial aspect receives innervation from the dorsal cutaneous nerve to the 4th web space (ultimately a subdivision of the Superficial peroneal nerve). Once the muscle belly of abductor digiti quinti is seen (1) there is no need for more proximal dissection.

Sub-periosteal dissection to expose the metatarsal and joint, required for surgical correction of Bunionette.
As with the first ray leave the plantar attachments & blood supply to the metatarsal head intact (1).
The capsular structures should also be opened carefully and in particular as a single sheet dorsally and one plantar, to allow effective soft tissue correction of any varus deformity at the MTP .To allow this the distal attachments to the Phalanx of the capsule also need to be preserved.
A Homans’ rectractor and McDonalds’ are used to deliver the metatarsal head and protect the soft tissues. The head should be inspected for chondral damage but this is very unusual with the 5th metatarsal.

Dissection need not proceed as far as the Abductor Digiti Quinti(1). A far shorter osteotomy can be used than is required for a bunion.
Correcting the deformity is invariably far less taxing than a Hallux Valgus . It is of course important the the correct operation is chosen which has the ability to correct the deformity. A degree of capsular reefing will be required in some cases but otherwise the additional steps seen with Hallux Valgus correction are not replicated.

A small amount of bone only needs to be removed from the lateral prominence(1)of the bunionette.
In general use a short and narrow blade on the saw (unlike the one being used here).

A standard Scarf type osteotomy is performed, using the same technique as described for Hallux Valgus.
It is important to not cut too far plantar with the first vertical and distal cut. Once the small exostosis has been removed mark the point that you are going to cut too with the end of small pair of forceps making a hole into the bone and make sure the cut doesn’t go beyond this. This should be centrally placed with respect to the lateral surface area.
The long(er) horizontal cut should split the shaft midpoint (equal bone above and below is what to strive for) and be angled plantar-wards slightly.
The proximal and plantar based cut is the final one and should parallel the initial vertical cut.
You may need to pass a sharp and appropriately narrow Lambotts’ osteotome through all the cuts if the osteotomy isn’t immediately mobile (though with the 5th metatarsal this is unusual)
Of course if there is not an angular deviation of the shaft but just simply a prominence of the metatarsal head then this alone can be removed.
Alternate designs of the osteotomy are a Chevron with a long plantar cut or a pure oblique diaphyseal cut

The inferior limb of the osteotomy(1) can be both translated medially as well as angulated laterally(to correct the articular angle) if required for correction.
See the post-operative X-rays for an example of correction in both these directions.

The translated metatarsal is effectively held using a pair of Kochers forceps(1). On occasion an additional small K wire (1 mm diameter approximately) across the osteotomy can be used to help stabilise during fixation. What size fixation is appropriate is determined by bone size. Generally a twist off screw(2) between 11-14 mm will do the job. Subtle variations in the implant design of twist-off screws between manufacturers make this a “home-run” step or pain in the ass.
The twist-off screws come with a shank (allowing attachment direct into a chuck) fixed to the head. The screws are self-drilling and self tapping and need to be drilled into the bone carefully and not under too much power or pressure or the shank will snap off well before the screw is fully drilled or seated. If this happens there is a purpose designed screw-driver to finish the job , which I suggest you have to hand every time you start drilling.
Some manufacturers screws seem to break off habitually too soon so its worth avoiding those. Some thread dimensions are such that they fix poorly too often and its also worth identifying and avoiding those too.
The screw size is of course guessed and not measured so if you don’t get a good fix consider going slightly longer .You can afford to go beyond the cortex a bit in most areas apart from the metatarsal head. You should check the plantar aspect of this before closure to ensure the screw hasn’t penetrated.

Proximal fixation of the osteotomy is also required, again using a twist off screw. This is angled medially to catch the displaced plantar cortex.
Once both screws have been inserted check manually the stability of the fixation. If poor (and long enough screws have been used) consider a 3rd more centrally placed screw.

A redundant overhang of bone(1) produced by translating the lower segment and correcting the bunionette. This will be removed with a small power saw and blade.

Further excess bone removed after the metatarsal translation and Bunionette correction.The alignment of the little toe should also be considered and a lateral soft tissue plication performed in all cases.
If there is a pre-operative varus angulation at the joint then a capsular closure in the style shown for Scarf and Chevron osteotomies is performed. The excision of a V shaped segment of capsule from the inferior limb of capsule allows a tightening closure to be performed with resulting corrective lateral pull on the MTP joint. If the MTP is not deformed then care needs to be taken during closure not to deform the joint into valgus and a direct closure with interrupted 2.0 Vicryl sutures can be performed.
Skin is closed with a subcuticular closure.
A padded dressing is used to splint the toe in a corrected position.

Pre-operative(left) and post operative(right) X-Ray films demonstrate the versatility of the Scarf osteotomy. Using translation as well as angulation both the increased inter-metatarsal angle as well as lateral angulation of the metatarsal shaft have been corrected.

Pre-operative(left) and post operative(right) clinical pictures showing the narrowing effects upon each border of the foot of using concurrent Scarf osteotomies for both the 1st and 5th metatarsals.