Copyright © 2008 by The Journal of Bone and Joint Surgery, Inc.
Commentary & Perspective
Commentary & Perspective by
Philippe Hernigou, MD, Martin Mukisi-Mukasa, MD, Paolo Filippini, MD, and Olivier Manicom, MD*,
Hôpital Henri Mondor, Créteil, France
Posted March 2008
In this issue of The Journal, Nam et al.
investigate the prognosis of untreated hips with early, asymptomatic
osteonecrosis of the femoral head. Only a few papers have been published
on this topic of clinical importance, and there is a considerable difference of
opinion in the orthopaedic community with regard to treatment. There is general
agreement that for hips that are in earlier, pre-collapse stages (Steinberg
stages I and II) of osteonecrosis
of the femoral head, it is usually preferable to perform some type of
intervention to retard or halt the progression of the disease in symptomatic
patients1-4. However, no such agreement exists for asymptomatic
hips. For example, Davidson et al.5 found that osteonecrosis, as
diagnosed with the use of magnetic resonance imaging or radiography, progressed
and became symptomatic at twenty-four months in forty-one (73%) of fifty-six
initially asymptomatic hips. They concluded that because of this high
prevalence of progression, even asymptomatic hips might benefit from early
surgical intervention. In hips treated with core decompression and grafting
before the occurrence of femoral head collapse, Belmar et al.6 found
that the outcome was correlated with the size of the necrotic lesion but not
with the preoperative pain level. Takatori et al.7, who followed
thirty-two asymptomatic hips in patients with normal plain radiographs, found
that no collapse occurred in fifteen hips with small lesions, whereas collapse
occurred in a mean of fifteen months in fourteen (82%) of seventeen hips with
moderate to large lesions. Hernigou et al.8 followed forty untreated
hips that had small asymptomatic stage-I lesions and found that thirty-five
(88%) of the forty became symptomatic and that twenty-nine (73%) of the forty went
on to femoral head collapse after a minimum ten-year follow-up. They concluded
that because these hips did collapse in a large percentage of patients, such
patients should be followed closely over a long period of time. There is
considerable variability in the risk of progression that has been reported by
the different authors9-11. This is not surprising, as asymptomatic
osteonecrosis is not common and few physicians have the opportunity to gain
substantial experience in treating it. This also explains why the literature
contains a considerable diversity of opinion on the best way to manage patients
with asymptomatic osteonecrosis.
The authors
of the current paper have attempted to better understand this problem. This
study provides clinically interesting and useful information. Importantly, they
evaluated the fate of untreated asymptomatic osteonecrosis of the femoral head with an emphasis on the size of
the lesion. In the present study, 105 asymptomatic hips with early stages of
disease were followed without any treatment. Sixty-two hips were followed until
pain developed, and the other forty-three remained painless without collapse
for five years or more. Therefore, the overall rate of progression of
asymptomatic osteonecrosis in this study was 59%. The extent of the necrotic
lesion was an important factor in predicting the prognosis of asymptomatic
osteonecrosis of the femoral head. The rate of disease progression, defined as
the development of pain, was 5% for small necrotic lesions (<30% of the area
of the femoral head), 46% for medium-sized necrotic lesions (30% to 50% of the
area), and 83% for large necrotic lesions (>50% of the area). They concluded
that no treatment is necessary for asymptomatic necrotic lesions when they
involve <30% of the area of the femoral head, as calculated with their
method.
While we
agree with the majority of their conclusions, we would offer some additional
remarks in improving the orthopaedic management of patients with asymptomatic
osteonecrosis. The authors have not reported the etiology of the
osteonecrosis, a factor which, in our experience, is probably as important as
the extent of the lesion. Patients
with sickle cell disease12 or patients with osteonecrosis related to
corticosteroid therapy9 have a higher risk of rapid progression than
others. It is sometimes difficult to obtain an accurate measurement of
the size of the lesion, and thus the determination of prognosis as based on
estimates of lesion size may lack sufficient accuracy. Furthermore, for some patients (e.g., patients
with sickle cell disease or systemic lupus erythematosus), it is impossible to determine
the difference between a total absence of pain in the hip and a paucity of pain. Thus, we believe that early prophylactic surgical procedures should not always
be withheld specifically because of the absence or paucity of pain. In some situations,
it might be advisable to undertake some form of early prophylactic surgery to
retard or reverse this progression and preserve the femoral head rather than
let it remain untreated and risk a high prevalence of progression and collapse,
especially in patients who are about to undergo a more definitive procedure on
the contralateral, symptomatic hip. An early, prophylactic, conservative
surgical procedure on the asymptomatic hip to improve the prognosis for
preserving the femoral head can usually be performed at the same time that the
patient is undergoing surgical intervention on the symptomatic, contralateral
hip. If surgery is not
performed early, patients should be followed closely because a small but
definite number of hips that have only a small area of osteonecrosis may become
symptomatic and have radiographic evidence of progression, even a long time after
the initial diagnosis8; therefore, a long period of follow-up is
needed. At the first signs of radiographic or clinical progression,
prophylactic surgery should be considered for such patients.
*The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families 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 authors, or a member of their immediate families, are affiliated or associated.
References
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