At a recent meeting a member of a faculty panel was presenting cases and asking what the other panelists would do faced with similar situations. A case of ankle fracture was presented in which, after the fracture had healed, posttraumatic ankle arthritis developed with continuing pain; therefore, the surgeon performed an ankle arthrodesis, using fully threaded screws, at a later date. The arthrodesis failed to unite. The surgeon later revised the arthrodesis by removing the fully threaded screws and using another type of implant. Successful arthrodesis was achieved.
The panelist was asked why he thought the ankle arthrodesis had failed the first time around. Was it possible that the type of implant had something to do with the failure? Was it possible that the fully threaded screws were keeping the surfaces apart? The questions were immediately dismissed by the presenter and by other panelists, who said that the fully threaded screws are conical and achieve great compression. Yes, but we are dealing with biology, and so far as we understand, after the surfaces have been prepared for arthrodesis, in days to come there will be resorption of bone at the prepared surfaces. Therefore, even though the fully threaded feature and the conical design in these screws provided a great degree of compression across the prepared surfaces at the time of surgery, these very threads straddling the site for arthrodesis are likely to keep the surfaces apart and perhaps be an impediment to fusion. However, the presenter and other panelists were not open to entertaining this possibility. Interestingly, the same panelist presented another case in which he showed a successful ankle arthrodesis using partially threaded screws.
When there is failure with one strategy and success with another, it certainly behooves us to stop and think and analyze possible factors behind both success and failure. Apart from the implant choice there are, of course, many other variables that influence outcome. Although it is not scientifically conclusive with an n of 1, it certainly can set the stage for a trial that would perhaps be more conclusive. However, anecdotal observations such as these have led to great studies. It is helpful to have an open mind.
Vinod K. Panchbhavi, MD, FACS