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To the Editor:

I found the article by Rombaut et al on physical and muscle function impairment in the hypermobility type of Ehlers-Danlos syndrome (EDS-HT) published recently in Arthritis Care & Research to be interesting and provocative (Rombaut L, Malfait F, De Wandele I, Taes Y, Thijs Y, De Paepe A, et al. Muscle mass, muscle strength, functional performance, and physical impairment in women with the hypermobility type of Ehlers-Danlos syndrome. Arthritis Care Res [Hoboken] 2012;64:1584–92). The authors noted that there was not a significant difference in muscle mass in the lower extremities of their subjects and that their technique was “validated against measurements with magnetic resonance imaging.” I wonder if, instead of measuring the muscle mass as lean tissue mass excluding fat and bone from “a diagonal line drawn outward and upward from the groin area through the femoral neck,” the authors were able to look more specifically at the muscle mass of individual muscles, which would have appropriately given a total muscle mass of the lower extremities.

Because patients with the EDS-HT typically have significant genu recurvatum, I would be most interested in knowing what the patients' vastus medialis (VMO) muscle mass was in relation to the muscle mass of the other quadriceps muscles. The VMO is only engaged and exercised in the last 10–20° of extension. For the patient whose knee extends >10°, there are fewer instances in routine daily function where complete extension is necessary. Hence, the VMO is less frequently engaged or exercised when given an opportunity to strengthen. I have found that many patients with significant genu recurvatum have an apparent imbalance of quadriceps strength and frequently have accompanying pain and impaired function secondary to patellofemoral tracking disorder. Do the authors think that a more individualized assessment of the mass of individual muscles in relation to each other might contribute to their findings, in addition to the role of the muscle extracellular matrix composition?

ACKNOWLEDGMENTS

Dr. Schikler has received consultancy fees, speaking fees, and/or honoraria (less than $10,000) from Abbott and owns stock or stock options in Biogen, Curis, Cytori, Enzon, Immunogen, Novartis, Optimer, Osiris, and Trovagene.

  • Kenneth N. Schikler, MD

  • University of Louisville School of Medicine

  • and Kosair Children's Hospital

  • Louisville, KY