A Simple But Effective Technique For First MPJ Fusion
I want to discuss a simplified technique for a first metatarsophalangeal joint (MPJ) fusion. I think we sometimes get caught up in the hype of plating systems and joint preparation devices. Sure, it is fun to use these and they do work. However, at times, I have found that using these devices can be counterproductive, making things more difficult than they should be.
Many of the instrumentation kits for plating systems have reamers for joint preparation. Although these reamers can do a great job of removing cartilage and preparing your fusion site, there are some potential pitfalls. The first potential problem is that the cutting flutes tend to be very aggressive and if you are not careful in applying negative pressure (i.e. “touch–touch”), you will lose significant bone length.
Secondly, in order to get unobstructed exposure (the reamer hitting the other side of the joint), you really need to do an aggressive dissection and stripping of soft tissue, which cannot be good for bone healing.
Finally, even though the “ball and socket” or “cup and cone” construct aids in positioning the toe in all directions, it is not as stable as a “tabletop” preparation. The tabletop joint preparation prevents motion of the toe in all directions, making the ultimate fixation construct even more stable.
So the simple technique that I do is to hold the toe in the desired position and pass the saw through the joint a few times. Then use a rongeur to remove bone and cartilage fragments. Employing a curette can facilitate removal of any residual cartilage. Then you can use the technique of reciprocal planing to get your final preparation and toe position.
For fixation, you can do what you are comfortable with doing. I tend to use a single K-wire down the middle (just like in hammertoe surgery). This is my positioning K-wire before performing further fixation. Load the foot, make sure the toe position is perfect clinically and use fluoroscopy to confirm the position. Then I typically use compression staples. I can leave the K-wire in for four to six weeks if I want or need an additional point of fixation.
I only consider using a plate when I am doing a revision of a non-union or if I need to incorporate an interpositional bone graft.
The main reason to avoid the tabletop technique would be with a very short first metatarsal in which shortening of the metatarsal is a major concern. In that instance, I will use only hand instrumentation with a curette and rongeur to remove only cartilage and then use a rotary burr to thin the subchondral bone. I will then follow up with fenestration of the metatarsal head and base of the proximal phalanx with a 1 to 2 mm drill bit.
In summary, the tabletop joint preparation requires less dissection and stripping of soft tissues, and provides good inherent stability. You will also get down to good, raw cancellous bone at the fusion site. This is important for quick consolidation of the fusion.