To The Editor:
I read with interest the paper titled "Proximal tibial
osteochondroma in patients with fibrodysplasia ossificans progressiva"
seen in the current issue of the Journal of Bone and Joint Surgery(1).
The authors described an interesting ossification on the medial aspect of
the proximal tibial metaphysis in 90% of the patients with fibrodysplasia
ossificans progressiva, and they described the ossification as
osteochondroma.
Osteochondromas, cartilaginous growth arising from the ectopic growth
plate, have specific imaging features that are an ossification at the
metaphysis with the bone marrow connected to that of the host bone and a
cartilaginous cap on the surface of ossification. The cartilaginous cap
is difficult to detect by plain radiography, but may be seen using
ultrasound, CT or MR imaging. These two features are important to confirm
the diagnosis of osteochondroma based on imaging features, since reactive
ossification may have similar ossification on the bone surface. In this
paper, no connection with the bone marrow is shown at least in the Figure
1B, and it precludes osteochondroma.
The type of ossification in this paper has been described as
exostosis-like outgrowth, or "coat-hook exostosis," and it is considered
to be a normal variant(2). The location of the ossification is in the
region of pes anserinus, and it may be associated with pes anserinus
syndrome. Such ossification had been removed because it was symptomatic,
and no cartilaginous cap was demonstrated if it was not the case of
hereditary multiple exostoses(3,4). Because of the lack of cartilaginous
cap, solitary ossification arising from the medial tibial metaphysis is
probable reactive ossification related to friction, not osteochondroma.
The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated .
References:
1. Deirmengian GK, Hebela NM, O'Connell M, Glaser DL, Shore EM, Kaplan
FS. Proximal tibial oseochondromas in patients with fibrodysplasia
ossificans progressiva. J Bone Joint Surg 2008;90:366-374.
2. Fryschmidt J. Freyschmidt's "Koeller and Zimmer" Borderlands of
normal and early pathologic findings in skeletal radiography (5th ed).
Stuttugart: Thieme 2008. p 921.
3. Ugai K, Sato S, Matsumoto K, Matsubara T, Mizuno K, Hirohata K. A
clinicopathologic study of bony spurs on the pes anserinus. Clin Orthop
Rel Res 1988;231:130-134.
4. Fraser RK, Nattras GR, Chow CW, Cole WG. Pes anserinus syndrome due to
solitary tibial spurs and osteochondromas. J Pediat Orthop 1996;16:247-
248.
Letters to the Editor: ![[Read Letter to the Editor]](/icons/misc/sectionDOWN.gif){kind=icon}
