TO THE EDITOR:
Armstrong and Lavery, in "Elevated Peak Plantar Pressures in Patients Who Have Charcot Arthropathy" (80-A: 365—369, March 1998), make a valuable and elegant contribution by demonstrating that increased plantar pressure is associated with ulceration and arthropathy. To prevent these lesions, they recommended "therapeutic footwear and insoles to reduce pressures on the foot."
My experience in a sports-oriented general practice is that contracture of the gastrocnemius is the greatest cause of increased plantar pressure. As Armstrong and Lavery stated, "the Achilles tendon pulls the hindfoot into plantar flexion, causing the forefoot to bear a considerably increased load." I teach patients that they will have increased plantar pressure unless they stretch the gastrocnemius until they can fully dorsiflex the ankle with the knee in full extension.
Athletic patients can usually use the ipsilateral hand to hold the foot in full dorsiflexion while they extend the knee, and they understand that they have not adequately stretched the gastrocnemius until they can fully extend the knee without losing full dorsiflexion of the ankle. Other patients may need to use a towel to hold the foot in dorsiflexion. Patients learn to keep looking at the anterior aspect of the ankle to be sure that the large wrinkles that occur with dorsiflexion are not lost while the knee is extended. Other gastrocnemius-stretching exercises, such as the step stretch (during which the heel and the midfoot are lowered off the step below the level of the forefoot) and the so-called downward dog position in yoga, also may be effective. However, as these stretches do not have a clear end point, the patient is not sure when the gastrocnemius is fully stretched.
A few patients have been unable to stretch and have had successful operative treatment consisting of recession of the gastrocnemius or lengthening of the Achilles tendon if the soleus is tight as well.
Proper footwear is, of course, important. However, patients, especially those who have diabetes mellitus, need to understand the importance of stretching and what it means for the gastrocnemius to be fully stretched because, as Armstrong and Lavery said, the forefoot functions as a lever. With the mechanical advantage of a lever, forces from the gastrocnemius that are well tolerated in the heel of a supple limb may result in "collapse in the midfoot" in a limb in which the gastrocnemius is contracted.
David J. Fleiss, M.D.: Sports Injuries and Arthritis Surgery, 901 Fifth Avenue, New York, N.Y. 10021
Dr. Armstrong and Dr. Lavery reply:
We appreciate the opportunity to respond to the insightful comments made by Dr. Fleiss regarding mobility of the ankle joint in patients who have diabetes. Indeed, we agree with the importance of daily stretching for our patients, and we wholeheartedly endorse the concept of prescribing physical therapy for assistance in this endeavor. The association among glycosylation of tendon and periarticular soft tissue, limited mobility of the joint, and ulceration has been made both by our group and by others1-5. Although patients who have diabetes may receive less benefit from stretching than healthy athletes because of soft-tissue glycosylation, it stands to reason that stretching helps to retard or to reduce the impact of limited mobility of a joint. Certainly, this approach needs to be evaluated in this patient population.
In a recent case-control study3, we reported that the risk of ulceration is approximately twelve times greater for subjects who have neuropathy and limited mobility of the joints than it is for subjects who have intact sensation. In comparison, there is only a twofold increase in the risk for subjects who have neuropathy alone. We believe that early intervention, such as stretching, may prevent progression to limited mobility and commensurately reduce the risk of ulceration.
Once again, we thank Dr. Fleiss for his commentary and look forward to further discourse on this fascinating area of investigation.
David G. Armstrong, D.P.M.; Lawrence A. Lavery, D.P.M., M.P.H.: Department of Orthopaedics, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78284-7776