Isolated fusions of the rearfoot have long been a choice of many podiatric foot and ankle surgeons for conditions such as coalitions, arthrosis and symptomatic flatfoot deformities. Persuasive arguments can be made for fusion of the calcaneocuboid, subtalar or talonavicular joints, especially when it comes to deformities such as the symptomatic flatfoot. While each of these procedures provide certain benefits for surgeons, they can present their own unique intraoperative and postoperative challenges as well.
With this in mind, I would like to share my thoughts as to why my talonavicular (TN) fusions have had far less successful outcomes than my other isolated rearfoot fusions. Originally, I simply labeled this arthrodesis as inferior and gravitated toward other procedures. However, after reviewing the majority of my cases and reading authors who prefer this technique, I have changed my opinion. Many of the unsuccessful outcomes I have had have come from identifiable and correctable problems.
All surgeons will agree that numerous factors can affect surgical outcomes. The patient’s health (mental and physical), social habits (i.e., smoking), occupation and compliance can all have a positive or negative impact. In reviewing my surgical results, I have divided the outcomes into short- and long-term failures. These are general categories and, naturally, several factors can work together to affect surgical outcomes. The following factors are what I feel I could specifically change to enhance the chances of a more successful case.
Poor patient selection is one of the most vague areas of failure. However, I have found less than stellar results after performing the talonavicular arthrodesis in an extremely obese patient. Even when I have addressed the ankle equinus surgically and performed adjunctive procedures, such as a first metatarsal-cuneiform arthrodesis, I have still had significant complications from persistent valgus deformity of the heel to abduction of the forefoot. Despite the fact that intraoperative alignment and immediately postoperative alignment are satisfactory, many of my cases progress to further planus deformities.
In many cases in which the patient is obese, I often prefer a triple arthrodesis. Although this is a larger procedure with a more complex postoperative course, I feel these particular patients receive a better long-term outcome with the more extensive surgery.
It is vitally important to evaluate the activity level of the patient prior to any rearfoot arthrodesis. Even if the surgery is properly indicated and performed, a fusion of the rearfoot can significantly alter function of the foot and ankle. Granted, these patients will most likely be experiencing significant pain preoperatively, but you must realistically discuss their expectations for the surgical outcome. In particular, these patients may need to consider occupational changes or changes in their athletic activity.
Why I Prefer Joint Resection Over Curettage In Most Cases
Joint preparation has been discussed numerous times over the past decade. Joint resection seems to have evolved slowly to more of an emphasis on curettage techniques. Although curettage is an excellent technique, I prefer a resection technique in most cases of talonavicular fusions for several reasons.
• Resection ensures removal of cartilage to the level of bleeding cancellous bone. The natural shape of the talonavicular joint makes it difficult to remove cartilage adequately from the lateral aspect of the joint without an ancillary incision. Instead of resecting both aspects of the joint, I often prefer to resect the distal portion of the talar head and then proceed to curettage and drilling of the navicular component.
• Performing resection shortens the medial column, which facilitates reduction of the flatfoot deformity. When you resect the distal portion of the talar head, you can reposition the TN joint and use the removed bone as an autogenous graft.
• Resection facilitates fixation with compression staples or plates.
Key Points About Ensuring
Inferior fixation is actually a term that is open to interpretation. The majority of my TN fusions are adequately fixated in compliant patients but may be fixated inferiorly in noncompliant patients.
The TN fusion, as a component of a triple arthrodesis, may be adequately held with a single lag screw. However, when performing the TN fusion as an isolated procedure, you need a second screw. In my experience, you don’t even necessarily need it to provide compression, but simply to aid in preventing rotation. I have employed very large single screws with limited success. In retrospect, the old AO adage of “two smaller screws are better than one large screw” definitely holds true in regard to this fusion.
External fixation using large and small systems is becoming increasingly popular as well. Large circular frames with tensioned wires are effective, especially in the revisional arthrodesis. The mini-rail systems have also been reported in this surgical setting, but I have found the rails useful for this fusion only as an adjunct and not as the sole source of fixation.
Addressing Post-Op Care
And Patient Expectations
Postoperative care and patient compliance are also extremely important in regard to the final surgical outcome. With the exception of cases in which external fixation is used, strict nonweightbearing for a six- to eight-week period is mandated. This may vary somewhat with the type of hardware you use and the stability of the fixation. I have heard lectures in which a surgeon discussed employing three screws and allowing immediate weightbearing to tolerance. In general though, I have found that I have far less chance of an unsuccessful fusion when I respect the six- to eight-week nonweightbearing period following TN fusions.
Poor procedure selection can result in either short- or long-term failure. In the short term, one may find that the procedure inadequately corrected the deformity. In the long term, you may find that the procedure did not maintain correction over a lengthy period of time. Specifically, you must address the need for adjunctive procedures.
In some of my own cases, as well as others I have had the opportunity to revise, the equinus was not appropriately addressed. This persistent deformity can lead to increased tension across the TN fusion site and promote non-union. It may also contribute to a more distal joint deformity, which is commonly found at the navicular-cuneiform and metatarsal-cuneiform joints. You should also carefully evaluate clinical and radiographic assessments of these two particular joints prior to surgery to judge this. One may need to achieve further medial column stability with an additional fusion.
Adjacent arthrosis in either the subtalar or calcaneocuboid joint should also cause the surgeon to consider a more extensive procedure. Even minimal arthrosis within these joints will quickly worsen due to the restriction of motion following a TN arthrodesis.
The final area that may ultimately contribute to failure of this particular fusion is patient expectation. Radiographs and clinical appearance may be perfect, but if the patient is not pleased, then the surgery will have failed. Appropriately discussing expectations and preparing the patient for a realistic outcome will increase the chances of patient satisfaction.
Dr. Burks is a Fellow of the American College of Foot and Ankle Surgeons, and is board-certified in foot and ankle surgery. Dr. Burks practices in Little Rock, Ark.