Secrets To Managing Complications Of First MPJ Fusion

By William Fishco, DPM

Arthrodesis of the great toe joint has been described for the repair of just about every problem affecting the great toe joint, including hallux valgus, hallux varus, hallux limitus/rigidus, osteoarthritis, rheumatoid arthritis and salvage of failed surgeries of the first ray. Many foot surgeons view the great toe joint fusion as a salvage procedure and will not consider it for primary repair of hallux valgus or hallux rigidus. One of the reasons for doing any type of fusion surgery is to stabilize an unstable or hypermobile joint. With that said, the great toe joint fusion can be beneficial for the patient who has a bunion deformity and a very large intermetatarsal angle. After appropriate soft tissue release, realigning the great toe joint will reduce the buckling forces that were previously encouraging the deformity. After adequate reduction, recurrence of the deformity is uncommon following a fusion. Certainly, no one would advocate a great toe joint fusion for all bunion deformities. However, in certain cases of severe deformity and instability, it works and does make sense. When it comes to surgical treatment of hallux rigidus, there are usually two groups of surgeons: the “Keller/implant” group and the “fusion” group. I personally do not recommend doing arthroplasties of the great toe joint in active individuals regardless of their age. The reason is simple. First ray destabilization is inherent to the arthroplasty procedure. When one considers that many of the forefoot pathologies are a direct result of a dysfunctional first ray, it seems counterintuitive to create such an environment that could ultimately cause new problems. Common complications following great toe joint arthroplasties include but are not limited to lesser metatarsal overload, which can lead to stress fractures and submetatarsal pain (bursitis/capsulitis), and a non-purchasing hallux, which can lead to hammering of the hallux. Moreover, if an implant arthroplasty fails and one needs to pursue reconstruction, it becomes challenging to restore the length of the first ray. This will usually involve using a bone graft with a fusion or callus distraction with a fusion. Therefore, I tend to reserve the arthroplasty for geriatric patients with apropulsive gaits and low functional demands. In my practice, active patients who have hallux rigidus are more likely to get a fusion than anything else. Why would one intentionally try to create 60 degrees of motion in a patient who has been functioning with 10 degrees of motion? It just does not make sense to me. Minimal motion converted to no motion seems more logical. How Emphasizing Key Principles Can Minimize Fusion Complications So why do many foot surgeons shy away from the first metatarsophalangeal joint (MPJ) fusion? It most likely has to do with a long list of potential complications such as delayed union, non-union, mal-union and fixation failure, as well as prolonged immobilization with the potential for cast disease requiring extensive rehabilitation and risk of deep venous thrombosis. However, if one follows sound surgical principles, it can minimize complications of the great toe joint fusion. The great toe joint fusion is no different than any other fusion of the foot or ankle. The three most important things to remember are location, location, location. An improperly positioned fusion is going to be trouble for the DPM and the patient. If the toe is too dorsiflexed, then the shoes will irritate it and a hallux malleus is likely to develop. If the toe is too plantarflexed, then it will cause pain at the plantar interphalangeal joint and will interfere with normal biomechanics of the foot. 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). Inside Insights On Fixation Hardware There are many internal fixation constructs available and, for the most part, all of them work. What did surgeons do 40 years ago? There were no screws but they got the great toe joint to fuse with large diameter pins. Sometimes, I do think we get hung up too much on technology. Always remember that good dissection, stable fixation and proper postoperative care will yield a fusion. Some examples of fixation techniques for the first MTPJ fusion include Steinman pins, crossing K-wires, bone staples, crossing screws, various plate systems and any combination thereof. Traditionally, surgeons have employed 1/3 tubular plates but these are bulky, often become irritating and have to be removed. Some have advocated maxillofacial plates because of their low profile but I have found they are generally too thin and break or fail easily. In recent years, specialty plates have been designed for the first MTPJ fusion. These plates are pre-bent and angled to facilitate application without having to fumble around with bending irons on the back table. I generally will not rely on a plate alone but will use at least one lag screw across the fusion site for compression. Then I apply the plate in a neutralization application. The ultimate goal for any fusion fixation is to maintain bone-to-bone apposition, stability and compression if possible. I personally recommend screw fixation and having at least two points of fixation. This can be crossing screws or a screw and a K-wire. This prevents axial rotation around one point of fixation. When implementing crossing screws, the concept of “stacking” screws is important so the surgeon has one screw more dorsal and the other more plantar to achieve compression over a larger surface area. The medial side of the joint is more accessible. Accordingly, the usual approach involves inserting a screw from the medial phalanx to the lateral metatarsal head and one screw from the medial metatarsal head to the lateral side of the phalanx. If feasible, it is best to have the screws cross at the fusion site for a stronger construct. I will generally use 4.0-mm cancellous screws. However, it is a perfectly acceptable to use 2.7-mm or 3.5-mm cortical screws. Plates do not provide any compression but one may use these as a neutralization application. Plates are generally recommended if clinicians are performing a revisional surgery or using an interpositional tricortical bone graft. For primary fusions, plates are not necessary but certainly can help provide a very stable fixation construct. The drawback, however, is that there is a lot of hardware in an area where there is not a lot of subcutaneous tissue so it can be a source of irritation and may need to be removed. Hardware failure may occur during the initial postoperative period. This is usually due to improper technique or surgeon error. This is true for any case using internal fixation. Examples include but are not limited to using cortical screw fixation and not purchasing the far cortex; lagging a screw without proper over drilling or failure to have screw threads beyond the fusion site; inability to get good bone purchase/compression; or inadequate stabilization. Sometimes, however, good surgery can be undermined by patient non-compliance. Always remember, if there is broken hardware or radiographic lucency around screws, there is probably motion at the fusion site. This is a recipe for a non-union. When one notes motion during the initial stages of the postoperative period, consider placing the patient in a cast and make him or her non-weightbearing. Otherwise, one will probably end up revising the fusion. How To Facilitate Post-Op Success The post-op period is critical in minimizing complications. Good surgery can be spoiled by non-compliance, smoking and unforeseen circumstances. No matter how good the fixation is, one will need to protect the great toe from bending forces. One can place compliant patients in a fracture boot and use crutches for light touch weightbearing. Remember that with a properly positioned great toe joint fusion, the great toe should not purchase the ground during midstance. Therefore, light touch ambulation in a fracture boot is acceptable. In addition, one may build up the fracture boot with felt or cork with a first ray cutout to prevent loading of the great toe joint. Instruct patients to avoid putting any pressure on the big toe. Strict non-weightbearing is recommended in certain circumstances. This includes cases that involve non-compliant patients, osteopenic bone, revisional fusions with or without bone grafting, and when one is not confident in the internal fixation construct. For fusions utilizing bone grafts, strict non-weightbearing for at least eight to 12 weeks is generally preferred. Take radiographs regularly to evaluate healing. Usually at one month, one should see initial bridging of bone across the fusion site. One may start progressive weightbearing at that time. Bone growth stimulators are generally recommended in revisions, bone grafting and for smokers. In Conclusion In my mind, the ultimate goal is getting a rapid union in the desired position. All of the other complications are relatively minor and generally will not affect the ultimate surgical outcome. Minor complications include hardware irritation, delayed union (assuming it goes on to union), prolonged cast immobilization and/or any of the inherent complications encountered in all types of foot surgery. These complications may include prolonged edema, wound dehiscence, numbness and mild postoperative infections amenable to oral antibiotics. Dr. Fishco is board-certified in foot surgery and reconstructive rearfoot and ankle surgery by the American Board of Podiatric Surgery. He is a teaching faculty member of the Phoenix Baptist Residency Program and is in private practice in Phoenix. He is also a faculty member of the Podiatry Institute.



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