Emerging Insights On The First MPJ Arthrodesis

Author(s): 
Shelby Swanson, BA, Andrea Dyack, BS, BA, and Michael S. Lee, DPM, FACFAS

   Hyer and colleagues performed a cost comparison of the crossed screw technique versus dorsal plating for first MPJ arthrodesis while also analyzing fusion rates and complications.3 This series included 45 patients with a 20 month follow-up. There were no statistically significant differences between techniques in regard to the proportion of patients achieving fusion, time to fusion or prevalence of complications. The mean cost for crossed screws was $374.05 (± 76.30), which was significantly lower than the mean cost for the dorsal plating technique, which was $603.57 (± 234.70). The authors concluded that screw fixation incurs less cost without compromising clinical results.

Salient Insights On Surgical Technique

Surgeons typically perform the procedure with the patient under regional or general anesthesia. The senior author prefers to utilize tourniquet control of the field and notes that an ankle tourniquet is appropriate in the case of first MPJ arthrodesis. In cases of revisional bunions, failed implant arthroplasty or non-unions, one should consider the potential need for bone grafting, particularly if a structural graft is indicated to re-establish or maintain length.

   The senior author prefers a medial approach as it allows for ease in fixation with crossing screws and provides a more acceptable cosmetic result for the patient. Create a medial capsular incision and elevate the capsule and periosteum from the medial aspect of the first metatarsal and the base of the proximal phalanx. One should limit dissection around the metatarsophalangeal joint in order to prevent unnecessary stripping of the soft tissue and blood supply to the fusion site.

   Using power and hand instrumentation, proceed to resect all loose bodies and spurring surrounding the MPJ. One may then use mini-Hohmann retractors to provide better exposure to both the metatarsal head and the base of the proximal phalanx. Curettage can remove any remaining cartilage. Use a high-speed 2 mm burr to resect and amalgamate the subchondral plate.

   Surgeons can then fenestrate the joint surfaces via a K-wire, drill bit or fish scaling with a small osteotome. While power reamers are available, the senior author cautions surgeons about using these due to potential excessive shortening of the first ray and the increased exposure required to introduce the instrumentation.

   Then position the fusion site and temporarily fixate it with 0.062 inch K-wires. In cases of hallux rigidus, one can obtain the optimum position with the toe completely derotated, 5 to 10 degrees of abduction and approximately 15 degrees of dorsiflexion. One may slightly increase dorsiflexion if necessary, particularly in females who may desire to wear up to a 2-inch heel.

   Positioning is difficult in the sagittal plane intraoperatively. Surgeons can utilize the tray lid from the small fragment screw set to help determine proper hallux positioning, allowing approximately one finger’s breadth to pass between the hallux and the lid as the lid loads the foot.

   In cases of hallux valgus, particularly longstanding cases or in patients with rheumatoid arthritis, take care not to “over-straighten” the hallux as it may serve as a long lever and prove difficult for the patient to ambulate.

Comments

I am happy to report 100% fusion rate with my great toe joint fusions. I'd like to share my technique and present a case I am considering doing currently:

Here are my surgical pearls for fusion of the first metatarsal phalangeal joint:

Like the authors, I use a technique to remove cartilage from the two bones with a rotary burr. I find it very helpful to have a baby lamina spreader to assist in distraction of the joint in order to simplify access. My instrument of choice is the Synthes brand baby lamina spreader.

I fenestrate the bones with a 0.045 wire, which allows more holes than a 0.062 wire.

I prefer using cross 3.0 mm cannulated screws.

I too use the lid of the screw set to ensure the proper 15 to 20 degrees of dorsiflexion. I temporarily fixate with cross guide wires and an additional 0.062 k-wire.

I prefer to put the plantar screw in from proximal medial to distal lateral and then add the more dorsal screw from distal medial to proximal lateral.

I find this to be a very rewarding surgery as most patients are in a lot of pain prior to performing this surgery, hence the need for this aggressive joint destructive procedure.

Here is an interesting case. I have a 64-year-old female with posterior tibial tendon dysfunction secondary to back surgery with a unilateral flat foot and severe hallux abducto valgus. She underwent a distal osteotomy for hallux valgus four years ago. In under one year, her hallux valgus was back as bad as before surgery.

She has an IM angle of 14 degrees, a short first met and HA of 60 degrees.

I am considering an opening base wedge osteotomy with a Wright Medical plate and staging three to six months later a fusion of the first MPJ. I feel as though an opening wedge osteotomy will work but the forces due to her posterior tibial tendon dysfunction and severe pronation will cause the bunion to return like after her last surgery.

Any experience combining a first metatarsal osteotomy with an arthrodesis? Any insight would be appreciated.

Lawrence Silverberg, DPM
blog: www.bestpodiatristnyc.com
bestpodiatristnyc@gmail.com

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