When A Revisional Surgery For A First MPJ Implant Does Not Go According To Plan
Surgery is usually a fun experience. Every now and again, however, we all have a case that humbles us and makes us more aware of the difficulty of what we do in the OR. My particular case was a bone block 1st metatarsophalangeal joint (MPJ) fusion after removal of an MPJ metal implant.
Any revisional case is inherently difficult. The surgical site is full of scar tissue. Most of the anatomy is obscured due to tissue remodeling from the previous surgery. Previously placed hardware may be broken, displaced or have migrated. From the beginning, things can be hard to navigate.
In my case, the patient had a metal first MPJ implant of both the metatarsal head and the proximal phalanx. This implant exhibited appropriate placement into the bone but the MPJ was no longer in a rectus position. The hallux progressed into a more valgus orientation and the patient was now feeling pain from the implant grinding upon itself.
The current surgical plan was for implant removal and fusion of the first MPJ with an allograft to make up for loss in length of the hallux. The graft we ordered was a pre-cut corticocancellous graft measuring about 11 mm x 7 mm x 7 mm. We also had some bone putty ready to fill any gaps. Lastly, we made sure multiple hardware options were available so we could adapt accordingly to what we found during the surgery?
Initial dissection was uneventful. Removal of the implant was surprisingly smooth. This style of implant does leave a considerable bony gap in the phalanx as well as the metatarsal head. We filled these voids with the bone putty. As soon as I placed the corticocancellous bone graft into the joint space, I knew that things were about to become difficult. The graft was too small. The length was reasonable for the hallux but the dimensions of the graft kept it from filling the void in the joint space properly.
In preparing for this case, I assumed we would be getting a fresh frozen femoral head-type allograft from which we could cut a custom sized graft to best fit into the space. Instead, we had this tiny crouton inside the joint. When placing the plate dorsally along the first ray for fixation, the graft would not stay central in the joint. This caused the hallux to drift out of rectus.
In reviewing the literature, there is no real consensus as to whether one should use a lag screw for a first MPJ fusion at all, let alone with an allograft. With any allograft, contact surface area is key to getting bony ingrowth and fusion of the graft. The addition of hardware may stabilize the site but will also reduce the surface area of the graft. In our case, we decided that a lag screw was necessary to maintain stability of the graft as well as the position of the hallux.
The screw held the graft in the relative center of the joint and kept the joint stable enough for the plate. The patient did have an increased first intermetatarsal angle, which gave us the next issue. Getting the hallux in line with the metatarsal would give the patient a relative hallux varus based on the rest of the foot, so we left the hallux in a slight valgus position.
In the end, the surgery was fine. The toe was in an appropriate position, the hardware was stable and I learned some valuable lessons. First is patient selection. I believe the patient’s underlying increased first intermetatarsal angle was the major factor in the failure of the initial implant. I think this was also a confounding factor, which prevented us from putting the hallux in an appropriate fusion position.
The second issue was the graft size. In my opinion, is it best to be able to create your own graft out of a larger allograft than be confined to a pre-cut size. This gives one the ability to make the appropriate size graft to both fill the joint space as well as adjust the toe position with the cut of the graft.
Finally, the third lesson was to make sure to have a variety of hardware selections available. You never know when you will need to change gears.
Sometimes, it is the most challenging cases that makes us the best surgeons. We learn to think on our feet and improvise while still trying to create the best possible outcome for the patient. Things do not always go according to plan. However, hopefully we can all learn from our experiences as well as the experiences of others.
Dr. Bishop is a third-year resident at Alliance Community Hospital in Alliance, OH.
