Lapidus(1st MTC) fusion using the Paragon 28 Phantom intra-medullary nail system

It is important to have a reasonable clinical-radiological correlation for surgical cases. Normally severe cases are associated with a prominent bunion, severe valgus of the great toe and pronation of the toe due to lateral soft tissue constraints.
It is also important to note effect of lateral hallux deviation on lesser toes, which are normally laterally deviated as a result or suffering with a hammer toe deformity.

In pre-op analysis, I give special emphasis to evaluate the intermetatarsal angle, the hallux valgus angle and “the angle to be correct” (Ortiz et al. 2016) in order to decide which surgical technique is most appropriate.
In general, for severe hallux valgus and/or when there is a need for a correction of more than 9 degrees of the intermetatarsal angle, a lapidus or MTP Fusion is chosen.
For correction less than 9 degrees an osteotomy like scarf or chevron is my choice.
In this case, there is an IM angle of 18.4 degrees with an angle to be corrected of 11.7 degrees and a normal MTP joint, so my choice in this cases would be a lapidus fusion. It’s important as well to evaluate potential TMT joint instability, which would be another factor to consider in the decision making process.
Ortiz C, Wagner P, Vela O, Fischman D, Cavada G, Wagner E. “Angle to Be Corrected” in Preoperative Evaluation for Hallux Valgus Surgery: Analysis of a New Angular Measurement. Foot Ankle Int. 2016 Feb;37(2):172–7.
Ortiz C, Wagner P, Vela O, Fischman D, Cavada G, Wagner E. “Angle to Be Corrected” in Preoperative Evaluation for Hallux Valgus Surgery: Analysis of a New Angular Measurement. Foot Ankle Int. 2016 Feb;37(2):172–7.

Landmarks are drawn with a skin marker, defining the 1st TMT joint (1), 1st metatarsal longitudinal axis(2), 1st phalanx metaphysis (for the Akin osteotomy and bunion exostectomy incision, 3) and lateral ligament release insicion (4).

Carry out a medial incision over the 1st TMT joint, using fluoroscopic help to locate the joint.Create a sub-periosteal pocket just in the medial aspect, enough for introducing the 4mm burr inside the TMT joint, using the specially designed MIS periosteal elevator surrounding the joint.
This comes with the rest of the MIS instrumentation for forefoot surgery. Be aware of the extensor tendon running dorsal to the joint and the tibialis anterior tendon at the medial-plantar aspect. Also, avoid getting too deep into the second metatarsal as you can damage the dorsalis pedis neurovascular bundle, which crosses through the proximal 1-2 metatarsal web space to the plantar aspect of the foot.

After adequate soft tissue mobilisation prepare the 1st TMT joint percutaneously.
Preparation is parallel with the articular line using a 4mm burr and 6000 RPM and continuous saline irrigation, under image intensification.

After adequate soft tissue mobilisation prepare the 1st TMT joint percutaneously under image intensification.There are two key points to respect when using the burr:
Firstly, it is important to select a burr blade that is not too long, to avoid the burr itself damaging the skin edges. Normally a 20mm long burr will be enough for joint preparation.
Secondly it is important to use the burr in a very systematic and controlled way during resection, in order to not over or asymmetrically resect bone, damage tendons or the neurovascular bundle in the first web space.
First, look under image intensification at the exact depth of the joint and keep to it while using the burr. Then, while you are at the centre of the joint, start a 180 degree movement against both joint surfaces, not exiting either the dorsal or plantar aspect of the joint.
A depth of approximately 2mm is required on each joint surface. In particular be careful not to over-resect the joint surfaces, which will significantly compromise Burring should be done under image intensification

After correct preparation of the TMT joint manual reduction should result in complete and homogeneous apposition of both articular surfaces.With fluoroscopic imaging I judge in both planes correct joint preparation, based visually both upon the new space created and also the movement that this allows.
Try to not over-resect as 1st metatarsal shortening may produce transfer metatarsalgia. Normally, resecting by the width of the burr is enough.
When you reduce the joint after preparation, in some patients there is a medial joint gap despite being careful to keep to a after flat and congruent resection. If this occurs you will probably need a lateral sided wedge resection of the TMT joint in order to get flat apposition of both prepared surfaces.
To do this using the same burr resect a little bit more in the lateral side of the TMT joint as to create a lateral sided wedge, avoiding 1st metatarsal shortening.

Under fluoroscopic guidance identify the hallux MTP joint and perform a lateral release (metatarsosesamoid ligament and lateral capsule) using a minimally invasive technique.
Under AP fluoroscopic imaging, localise the sesamoids and at this level, making a 2mm incision lateral to the fibular sesamoid, through which you vertically insert the beaver blade while maintaining a varus directing force to the hallux in order to tense the metatarso-sesamoid ligament. This is the structure intended to be released along with the lateral capsule. Avoid getting too deep with the blade, 1.5-2cm is normal but depends on patient size, as the plantar structures are potentially vulnerable to injury here.
After releasing, you will feel less tension during varus angling the MTP joint and also one can see sesamoid medialization happening on the image intensifier pictures.
For those unfamiliar with the technique of an open lateral release (known also as the modified McBrides procedure) this should be read first Lateral MTP joint release ( modified McBrides procedure)

After the lateral release, correct metatarsal pronation and hallux supination manually (de-rotate the hallux manually) and apply inter-metatarsal compression, then temporarily fix the 1st and 2nd metatarsal corrected position with a 2mm K wire.This step can be aided by a K wire, drilled into the metatarsal to supinate it, and a Backhauss clamp applied between 1st and 2nd metatarsal heads in order to reduce the inter-metatarsal angle.

For the Lapidus nail insertion, first make a 2cm incision over the proximal 1st metatarsal dorsal cortex, avoiding the extensor tendons.The incision starts 2cm distal to the TMT joint (located under fluoroscopic imaging) and extends for 2cm following the metatarsal axis. After skin incision you will find the extensor tendon, so continue your dissection medial to the EHL tendon down to bone.

Next step is positioning the “spherical” wire, which will serve as a guide for the nail positioning system, into the medial cuneiform.The target pin with its integral sphere is drilled into the plantar and proximal aspect of the medial cuneiform, located with the image intensifier.

From the lateral perspective aim the guide-wire to the most plantar-proximal aspect of the medial cuneiform (as marked here), avoiding entering the talo-navicular joint.It is key to aim distally with the target pin to avoid this joint.

Confirm the start point under fluoroscopy for the “spherical wire” (1) using a lateral and also dorsal view. Its planned trajectory should not breach the talo-navicular joint.

The spherical wire is driven into the medial cuneiform once, its correct start point is verified.
It is inserted carefully under II control until its thicker portion is in contact with cortical bone.
It is important to avoid breaching the talo-navicular joint, and it is evident from this AP image how close that joint is.

After adequate fixation of the spherical wire, place the “claw” end of the poly-axial targeting guide(1) on the spherical wire so that it “clicks” into place to allow rotatory motion on the sphere wire, but does not disengage.
The nail entry point is marked on the dorsal aspect of the metatarsal bone approximately 23mm proximal to the TMT joint with the aid of a special positioning guide (2), slightly lateral to the metatarsal mid axis.

These are the 2 jigs required for the Phantom nail.
Outrigger Slider (this is specific to the nail size chosen)
Outrigger
Thumb Screw
Phantom Nail
Sphere Wire
Polyaxial Targeting Guide
Polyaxial Targeting Guide – Sleeve Insert

Soft tissue protection is provided with the wire sleeve and a retrograde 2.3mm k wire is inserted at the previously exposed site, 2cm proximal to the TMT joint.The wire runs from slightly lateral in the dorsal metatarsal cortex and aiming towards the spherical wire using the polyaxial targeting guide(1).
After adequate K wire positioning, confirmed fluoroscopically, measure the length by the provided depth length gauge and drilling over the 2.3 mm K-wire using the 5.5mm cannulated drill and tissue protector.

Measure the length by the provided depth length gauge and drilling over the 2.3 mm K-wire using the 5.5mm cannulated drill, remove the wire and insert the nail on the specifically sized jig.After drill and K wire removal, mount the nail insertion system with the appropriated sized nail.
Nail lengths starts at 38mm, which is enough for most Lapidus fusions. In our population, the most used nail is a 42mm, but it depends on patient size.
Match the outrigger to the correct outrigger slider, specific to each nail size/side (1).
Attach the desired size of the Phantom Nail to the outrigger by turning the thumb screw in a clockwise direction to thread into the inside of the Phantom Nail until two-finger tightness is achieved (2).
Insert the thumb screw into the outrigger and down into the nail to secure it, prior to insertion (3)
Insert it through the previously drilled hole until the contoured piece on the outrigger is flush with the dorsal aspect of the first metatarsal. Normally, you don’t need to hammer the device and it enters smoothly.
The gold portion of the outrigger is buried in the 1st metatarsal to allow for compression.
Adequate nail positioning is confirmed with Image intensifier, so the nail tip is just touching the target pin and not crossing into the talus, as well as the proximal part is buried approximately 2mm under the dorsal metatarsal cortex. In the AP view it should be aligned in the centre of the TMT joint.

After confirming under fluoroscopy adequate nail insertion/size place a drill-pin guide into each of the two holes in the outrigger slider(1), and proceed with proximal fixation.
Next insert a 2.75 mm drill-pin(2) into the cortex through the lateral drill-pin guide, aligning the lateral guide and drill-pin with the tibial crest. This will serve as an anti-rotatory pin while inserting the medial screw.
Aligning the lateral guide assures that the nail is entering in the correct axial position, important for the screws in the next step.
Then insert the medial drill-pin, and after confirming appropriate size, insert the medial screw through the medial screw guide. Repeat these steps for the lateral hole, after removing 2.75 lateral drill pin, and insert a lateral screw also.
The proximal end of the nail is now fixed into the medial cuneiform.

With the nail now adequately fixed to the cuneiform, apply compression to the fusion site through the nail compression system.
To do this, first remove the screw guides from the medial and lateral holes in the outrigger slider, very slightly compress with the screwdriver initially, then remove any temporary fixation across the joint and then use a driver to tighten the top screw (1) on the outrigger completely.

Use the screwdriver (1) to tighten the top screw on the outrigger to create a slight amount of compression.
The temporary fixation across the joint should be kept in until a slight amount of compression is applied to help prevent rotation of the 1st metatarsal. Then, remove any temporary fixation across the joint and continue tightening until “two-finger” tightness is achieved.

After adequate compression is achieved, distal fixation is required. Repeat the steps used to place the screws into the cuneiform fixation, but now use the final outrigger hole in the first metatarsal (1) in mid-lateral direction.It’s my own preference to catch the 2nd metatarsal base with the same screw, although the official Paragon technique does not describe this. While doing this, you can maintain a K wire keeping alignment between 1-2 MTT, as secondary displacements may occur. (optional)

The orientation of the last screw hole for metatarsal fixation is determined by the rotation of the nail, which may vary slightly.
If this screw-holes direction delivers the screw dorsal (which is normal) or plantar to the second metatarsal, I skip second metatarsal fixation and insert a shorter screw just into the first metatarsal.
If it’s possible to catch the second metatarsal though it increases the constructs rigidity.

Remove the outrigger from the Phantom Nail and with the aid of the locking guide drill using the drill-pin into the distal locking hole, followed by a 3.5mm locking screw.

Insert a posteriorly directed 3.5 mm locking screw into the hole in the Phantom Nail at the base of the 1st metatarsal to serve as a second point of fixation in the metatarsal.
Confirm implant placement and size using fluoroscopy. The implant must be flush with the dorsal metatarsal cortex and the tip of the nail should be at the far cortex of the medial cuneiform.

Confirm implant placement and size using fluoroscopy. The implant must be flush with the dorsal metatarsal cortex and the tip of the nail should be at the far cortex of the medial cuneiform.

After correct nail insertion, close the surgical wounds and focus on the MTP joint.
Through portal number 2, with a beaver blade, get access to MTP joint and bunion.

After carefully sub-periosteal stripping and creating a subcutaneous pocket to avoid soft tissue damage, perform the bunionectomy under fluoroscopic control with a 2.3mm MIS burr.Try to not go dorsal with the burr and always applying force against the bone in order to lower the incidence of dorsomedial cutaneous nerve damage.
Also, always use continuous irrigation and be aware to not pass a running burr through the wound edges as it may cause burn injuries.

Go proximal with the burr up to the metatarsal neck-head junction, palpating smoothening of the bunion site as you proceed.
Some times bunionectomy is not necessary as with the TMT realignment the medial eminence is no longer prominent.
If there are any prominent edges, use the burr to smooth them with the soft tissue precautions already mentioned.

After bunionectomy, using same portal, perform an Akin osteotomy in an oblique fashion, orientated proximal-medial to distal-lateral, with the same 2.3mm MIS burr.
The oblique direction is to make fixation with a 2.5 screw easier.

Final radiological appearance after the MIS Akin osteotomy.

The final clinical appearance. The scars are small and the hallux anatomically aligned. The medial eminence appears more prominent than it is due to the excess skin present after removal of the exostosis and reduction of the IM angle. This soft tissue rapidly shrinks post-operatively.