External Fixation: Is It The Answer For Diabetic Limb Salvage?

By Guy R. Pupp, DPM, and Peter M. Wilusz, DPM

There has been a six-fold increase in diabetes mellitus over the last four decades in the United States.1 Indeed, 798,000 new diabetic patients are diagnosed each year in the U.S.2,3 The statistics are particularly disturbing when it comes to lower extremity amputation among people with diabetes. Lower extremity amputation among the diabetic population increased from 67,000 in 1994 to 140,000 in 2000.4 While amputation in the diabetic population is a viable option in the presence of significant peripheral arterial disease and gangrene, life expectancy after major lower extremity amputation is appalling with only a 40 percent five-year survival rate.2,3 However, many of these lower extremity amputations can be prevented via diabetic limb salvage. Granted, one must consider a realm of potential complications and the general health of the individual before proceeding with diabetic limb salvage (see “Why Appropriate Patient Selection Is Essential” below). Salvaging the diabetic foot has challenged many expert surgeons to provide a stable, predictable and reproducible method for fixating an unstable diabetic limb. However, one technique that is proving to be reliable for diabetic limb salvage is external ring fixation. Why Appropriate Patient Selection Is Essential The goals for limb salvage should be simple, focused and presented clearly to the patient. The goal is not just to prevent amputation but to provide a stable, ambulatory limb which, combined with education and glycemic control, will improve the quality of life for the patient. Optimizing patient compliance via the involvement of other specialty medical professionals will produce predictable results while achieving preset goals. One must address optimizing the diabetic patient’s emotional, psychological and physical well-being prior to surgical intervention for limb salvage. Indeed, patient selection is an extremely important factor when considering the use of external ring fixation for patients with diabetes. Discovering physical, psychological and emotional limitations during an interview process long before surgery can prevent early and profound failure. A difficult aspect of the interview process is determining the level of the patient’s intellect when discussing external fixation. Assessing the patient requires experience by the surgeon and possibly multiple interview sessions in order to ensure the patient fully understands all aspects of external ring fixation. Also keep in mind that a patient’s personal hygiene is often an under-evaluated factor during the interview process. However, a patient’s personal hygiene may play a large role in the development of pin tract infections during external ring fixation. People with poor hygiene and/or incontinence are poor candidates for external fixation and predictably experience higher rates of infection. How External Fixation Addresses The Failures Of Traditional Internal Fixation Traditional techniques of fixation in diabetic limb salvage can be unreliable.5 The use of internal screws, plates, staples coupled with a patient’s inability to remain non-weightbearing often yields inconsistent and undesirable results. For many diabetic patients, Charcot deformity is the pathological entity requiring surgical limb salvage intervention. However, two key factors lead to the failure of traditional internal fixation for reconstruction. These factors include poor bone quality and the inability to achieve adequate compression; and a deformity that limits access for proper, accurate fixation with appropriate anatomic reconstruction. External ring fixation does produce predictable and reproducible results in diabetic limb salvage.5 By using tensioned wires in external fixation adjacent to either the corrective osteotomy of the joint or the portion of the foot that you will be stabilizing, the compression you obtain will exceed that which is possible with internal fixation. There are applications for external ring fixation that cannot be addressed with internal fixation. For example, many patients have physical handicaps that prevent them from being non-weightbearing after surgery. Using an external ring fixator allows guarded weightbearing immediately after the procedure. The ability to bear weight is limited by painful stimulus so it stands to reason that neuropathic patients are often noncompliant.

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