Secrets To Managing Complications Of First MPJ Fusion

Author(s): 
By William Fishco, DPM

In the transverse plane, an improperly positioned toe can either cause irritation to the second toe (abducted) or be in constant contact with the shoe (adduction). Surgeons can minimize other complications via meticulous surgical dissection, proper application of internal fixation and appropriate postoperative management.
Adequate joint preparation is critical in any fusion. If one leaves cartilage or soft tissue debris in the fusion site, then it will certainly cause delay or failure to unite. There are two basic methods of joint preparation. One may opt for saw resection of the joint to obtain raw cancellous bone or utilize a curettage technique to remove cartilage and expose the subchondral bone. I have always been one to maintain the ball and socket relationship of the joint to aid in positioning the toe. If one has two flat surfaces, then it can be difficult to position the fusion without having to wedge and resect more bone.
More often than not, I try to preserve as much length to the first ray as possible. The joint resection technique will fuse quicker as raw cancellous bone is apposed. For the curettage technique, fenestration of the subchondral bone with a small drill or K-wire will encourage bleeding and can facilitate union.
There are surgical instruments available that can achieve the best of both techniques. Indeed, one can use specialized reamers to preserve bone length, maintain the ball and socket relationship, and remove the cartilage and subchondral bone to the level of bleeding cancellous bone.

Ensure Proper Positioning Of The Hallux
Positioning of the hallux is critical. Foot surgery textbooks have recommendations on the appropriate amount of great toe dorsiflexion and abduction. I have never found the recommended angles to be of much help for a number of reasons. First, I am not good enough to use a goniometer and cannot get accurate measurements. Second, every foot is different and one must make adjustments depending on the type of shoe and activities in which the patient is involved.

Accordingly, I follow simple rules when positioning the toe. The first rule is not to have the hallux rubbing the second toe and not positioning the toe in adduction (hallux varus) as the patient will have difficulty wearing shoes. Essentially, the hallux and the second toe should be parallel without actually touching one another. The second rule is that one should position the nail due north, which does not result in valgus or varus rotation. Finally, the third rule involves proper positioning in the sagittal plane. I use a flat surface, typically the sterilization tray cover that is on the back table, and place the foot on the tray in order to load the foot to mimic ground reactive forces.
I position the toe so I can place my finger under the toe. This seems to be a good rule of thumb. One can modify this if one knows the patient is going to be wearing a slight heel or, in my part of the county, wears Western-style boots. It is important to load the foot to visualize the position of the toe as one can easily get fooled into thinking there is more dorsiflexion than what is there. Another trap is looking at the relationship of the first metatarsal and the great toe. Remember that the first metatarsal is declinated so it can be misleading to eyeball the angle.
Another tip is to use an ink pen to draw a medial line bisecting the metatarsal and hallux in order to achieve a positional relationship. In hallux rigidus, the hallux is usually plantarflexed in relationship to the metatarsal (hallux flexus). This is probably due to spasm of the short flexor tendons and adaptation over time. Therefore, one can appreciate the line on the great toe to be inferior to the metatarsal line. After positioning the toe in proper alignment, one will notice the lines will become either parallel or close to parallel at the same level. This is not always the case but can be helpful in many instances as a guide.

Once the toe is in the desired position, use a 0.062 K-wire as temporary fixation to visualize the proposed fusion site under fluoroscopy. One can then make assessments on joint congruity, joint preparation/ apposition and metatarsal length (parabola).

Comments

EXCELLENT JOB OF EXPLAINING PROCEDURE.

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