An Emerging Option For Treating Severely Subluxed Lesser MPJ Deformities In Seniors

Author(s): 
Michael Tritto, DPM

   I proceed to perform a dorsal transverse capsulotomy to expose the base of the proximal phalanx, which is typically dorsally dislocated on top of the metatarsal neck. One would then dissect the base of the proximal phalanx free from any soft tissue attachments to prepare for resection. Use a sagittal saw to remove the base of the phalanx from medial to lateral, dorsal to plantar, just proximal to the metaphyseal flare of the phalanx. I usually resect no more than 3 to 4 mm of bone. I can always resect more later if necessary but I never resect so much of the base that I can no longer see the flare at the base. Once I have completed the bone cut, I remove the cut portion of the base. At this point, you will now see the metatarsal head and that the toe is much more easily relocated into a more normal anatomic position.

   I subsequently use a McGlamry elevator to free up the rest of the inferior surface of the joint and any other medial or lateral adhesions. I then prepare the proximal interphalangeal joint for fusion. I only resect the articular surfaces off the head of the proximal phalanx and base of the middle phalanx. I use a Trim-It® 1.5 mm pin (Arthrex) or a 1.3 mm OrthoSorb® Pin (Biomet) to fixate. The Trim-It pin is slightly longer and a little more rigid than the OrthoSorb pin. This is a factor depending on the size.

   I use the guide wire that comes with the pin kit to find the medullary canal by hand at the proximal phalanx and drive it in until I can see it exiting the base. Remove the wire and drill distally into the middle phalanx, across the distal interphalangeal joint and out the distal toe. (If you are using the OrthoSorb pin, you will not be able to cross both joints with one absorbable pin because of the length and will need to use two absorbable pins.) Now drive the guide wire across the proximal interphalangeal joint fusion site from distal to proximal through the previous hole you made so you can see the tip of the K-wire coming out the base of the phalanx.

   With the MPJ reduced to a slightly plantarflexed position, drill the wire into the metatarsal head to a depth of about 2.0 to 2.5 cm. Try to make sure the hole is slightly angled going into the metatarsal head because you do not want to go straight down the shaft into the medullary canal. Angling the drill hole allows control over how far the absorbable pin can go into the metatarsal and prevents proximal migration.

   Once you are satisfied with the position, remove the wire and insert the absorbable fixation. With the Trim-It pin, you can retrograde it out the distal toe and then drive the pin from the distal toe, crossing the distal interphalangeal and proximal interphalangeal joints. Drive the absorbable pin so you can see it exiting the base of the phalanx, align it with the hole you already drilled in the metatarsal head and drive the pin into the metatarsal about 2 to 2.5 cm. Once the pin is across the MPJ, cut the pin flush with the tip of the toe and tamp the distal end so it is under the skin. The OrthoSorb pin is not long enough or rigid enough to do it this way. You must insert the OrthoSorb down the proximal phalanx and across the MPJ, leaving about 5 mm exposed at the proximal interphalangeal joint fusion site to place the middle phalanx over. You can also do this with the Trim-It pin if you do not want to cross the distal interphalangeal joint. Closure is normal from here and is the surgeon’s preference.

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