Can A Reamer System Improve First MPJ Fusions?

There are many methods you can use to prepare the first metatarsophalangeal joint (MPJ) for arthrodesis. One of those techniques involves using a cup and cone reamer system. Using this system can be helpful, especially when there has been some trauma to the joint surface, when you’re dealing with an extremely arthritic joint with hypertrophy or when the patient has a square metatarsal head. These conditions could potentially prohibit an exact coaptation of the opposing bones.
However, the cup and cone reamer system (Howmedica) is designed to take advantage of the convexity of the first metatarsal head and the concavity of the base of the proximal phalanx, which yields solid contact between two opposing surfaces for arthrodesis.1 The Howmedica system contains five matching barrel reamers as well as proximal and distal bits that are 10, 12, 14, 16 and 18 mm in diameter.

Insightful Step-By-Step Tips
When it comes to the first MPJ arthrodesis, begin by making a dorsal-medial incision. Dissect through the tissue layers to the capsule. You may commonly encounter significant synovial fluid and osteophytes, which you can debride with a rongeur. You can achieve chondroplasty with the small joint reamer system or with another technique of your choice. I have found a rotary burr to be quite sufficient for this job.
Proceed to place a 0.062-inch smooth Kirschner wire axially through the first metatarsal head and make sure it is securely within the shaft. Occasionally, you may need to use the barrel reamer to yield a cylindrical distal metatarsal. You can attach it to a Jacobs chuck and trauma drill, and then guide the entire assembly over the K-wire.

Perform reaming until you’ve obtained a smooth cylindrical surface. (You may omit this portion of the technique since the concave and convex surface reamers are often sufficient to prepare the arthrodesis site.) Attach the cannulated proximal reamer (concave in appearance) to a trauma drill/reamer via a Jacobs chuck and then place the entire assembly over the Kirschner wire so it sits flush with the metatarsal head.
Perform reaming until the subchondral plate is denuded and you see bleeding bone. Remove the Kirschner wire and place it axially through the base of the proximal phalanx. Use the convex reamer in the same fashion to prepare the phalangeal surface. The result is a surgically induced cup and cone. I prefer to drill with a 2-mm drill bit on both surfaces at this point.

A Few More Pearls About Reaming
Reaming through the subchondral plate is absolutely necessary if you wish to obtain consistent union of any arthrodesis site. Inadequate preparation of the bone surface is one of the most common surgical causes of failure of arthrodesis second to improper fixation. Other causes for delayed union or non-union include patient factors such as non-compliance with weightbearing restrictions and smoking.
Using the “ream” setting on the trauma drill is necessary because of the lower RPM and torque differential when compared to the “drill” setting. I have found the drill setting to be too aggressive.
Adequate soft tissue exposure and retraction is necessary in order to avoid damage to delicate structures by the reaming process.

Addressing Final Positioning Of The Hallux
One topic of discussion among many surgeons is the final positioning of the hallux on the metatarsal. The literature can be rather vague with respect to exact angles.2,3 Much of this depends on the type of patient you are treating. Obviously, a female patient who is adamant about continuing to wear high-heeled shoes would dictate one position while an inactive male might require another position.

After we have prepared the joint surfaces, we’ll employ a Kirschner wire for temporary fixation axially through the hallux and into the metatarsal shaft. We then use the metal cover that comes with many screw sets to act as an intraoperative weightbearing surface. Then we manipulate the hallux into a position where the tuft is just off the weightbearing surface. When you squeeze the tuft of the hallux from medial to lateral, it touches the weightbearing surface. Rotate the nail plate until it faces up. You can determine the varus/valgus position by appearance and potential shoe gear. This method works quite well with most first MPJ arthrodesis procedures.
You can achieve subtle changes in hallux position quite easily with this method as opposed to joint resection, where you are left with two square
surfaces. The latter of these joint preparation techniques does not allow for such subtle changes of hallux position and subsequently, you will spend more time in the operating room attempting to obtain proper positioning.

What About Fixation?
Many forms of fixation are available and most often reflect the experiences of the surgeon. Buranosky, et. al., have tested the stability of fixation for first MPJ arthrodesis.4 The outcome of this study suggested a dorsal plate with an interfragmentary screw was the most stable construct when compared to two crossed screws. I prefer the crossed screw technique for speed, reliability and relative lack of prominence.
If fixation is solid, allow the patient to bear weight to tolerance in a cast brace. Obtain radiographs a week after the surgery and again at six to eight weeks postoperatively. Keep in mind that radiographic union of the arthrodesis site will not be complete for 12 weeks. Once you see satisfactory progression of the fusion process on plain films, you can gradually transition the patient into a shoe.

Final Thoughts
First MPJ arthrodesis is a proven surgical procedure for treating pathology in this region. The small joint reamers make preparation of the arthrodesis site faster and more congruous, which facilitates ease of positioning and the reliability of fusion.

Dr. Harrod practices in Richmond, Muncie and Indianapolis, IN. He received an AO Trauma Fellowship in Dresden, Germany.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons. He is board certified in foot surgery. Dr. Burks practices in Little Rock, Arkansas.

References:

References

1. Howmedica, Inc. Rutherford, NJ.

2. Yu GV. First Metatarsophalangeal Joint Arthrodesis, in Comprehensive Textbook of Foot Surgery, 2nd edition p. 564.

3. Hansen Jr. ST. Arthrodesis of the First Metatarsophalangeal Joint, in Functional Reconstruction of the Foot and Ankle, p. 343-344.

4. Buranosky DJ, et. al. First metatarsophalangeal joint arthrodesis: quantitative mechanical testing of six-hole dorsal plate versus crossed screw fixation in cadaveric specimens. J Foot Ankle Surg 2001 Jul-Aug 40(4)208-13.

Additional References

5. Coughlin MJ, Abdo RV. Arthrodesis of the First Metatarsophalangeal Joint with Vitallium Plate Fixation. Foot and Ankle Vol. 15 (1) Jan 1994.

6. Coughlin MJ. Technique for Metatarsophalangeal Arthrodesis Using Small Joint Reamers and Small Fixation Plates. Distributed by Howmedica, Inc.