Learning From Failed Talonavicular Fusions

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Here is a lateral radiograph of a failed talonavicular arthrodesis.
Here one can see a postoperative radiograph of a revisional arthrodesis with autograft and compression staple fixation.
By Jesse B. Burks, DPM

Key Points About Ensuring
Adequate Fixation
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.

Final Notes
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.

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