Managing Equinus In Patients With Diabetes
Although equinus is reportedly “the most profound causal agent in foot pathomechanics,” the phenomenon has yet to be addressed fully in the diabetic foot. Accordingly, these authors discuss the definition of equinus and offer insights on the efficacy of stretching, night splints, a new bracing option, tendo-Achilles lengthening and gastrocnemius recession.
There have been remarkable strides in diabetic foot care in the past two decades with marked improvement in amputation prevention. The collaboration between the vascular community and podiatric wound care community has made a profound impact as well. Another significant improvement for our patients with diabetes has been the increased attention on preventive foot care, consisting of routine diabetic foot care, diabetic shoes and orthoses, and periodic foot exams. These preventive measures have made a significant impact in keeping the diabetic foot out of harm’s way.
However, there is one final piece to the puzzle that has yet to be formally addressed and recognized with the respect it deserves. Evaluation and management of equinus is the final step we must take to provide a comprehensive preventive care program for the diabetic foot.
For good reason, researchers have described equinus as “the most profound causal agent in foot pathomechanics and frequently linked to common foot pathology,” and “the greatest symptom producer of the human foot.”1 The devastation that equinus imparts upon the foot and lower extremity in the non-diabetic patient is well documented in the literature, but it can literally be life-threatening in the patient with diabetes. The morbidity associated with a below the knee amputation is unfortunately well known. Often, the precipitating factor to the amputation is a diabetic foot ulcer.
When one reviews the literature, it is undeniable that equinus significantly increases the risk of a diabetic foot ulcer. Therefore, the treatment of equinus can reasonably be considered a life-saving preventative measure.
In order to understand the depth of involvement of equinus in diabetic foot pathology, an understanding of the biomechanical impact of equinus on the foot is crucial. Olipa and colleagues described the center of pressure in the foot to be approximately 6 cm anterior to the ankle joint.2 Without the counterbalance of the gastroc-soleus complex, this anterior displacement of the center of pressure would make us fall forward in normal standing.
With equinus, the center of pressure moves distally and laterally, moving it farther away from the axis of the subtalar joint laterally. This increased distance from the axis of the subtalar joint results in a pronatory moment within the foot. This movement cannot be overcome by the supinatory moment created by the medially located gastroc-soleus complex insertion into the posterior aspect of the calcaneus. Besides an increase of pronatory forces due to equinus, the other results are increased pressure on the forefoot and decreased pressure on the rearfoot.
Johnson and Christensen evaluated the effect of equinus biomechanically on the medial column of the foot by using cadaver weightbearing models in their landmark series on first ray pathomechanics.1 The authors applied sensors to each of the individual bones making up the medial column of the foot. They applied loading of the Achilles tendon and then recorded three-dimensional data for each segment of the medial column.