Published Online First: 25 May 2007.
doi:10.1136/ard.2006.066878
Annals of the Rheumatic Diseases
2008;67:150-153
Copyright ? 2008 BMJ Publishing Group Ltd & European
League Against Rheumatism
EXTENDED REPORTS |
Departments of Orthopaedic Pathology and Radiology, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021, USA
Correspondence to:
Dr Peter G Bullough, Department of
Laboratory Medicine, Hospital for Special Surgery, 535 East 70th Street, New
York, NY 10021, USA; bulloughp{at}hss.edu
Accepted 18 May 2007
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ABSTRACT |
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Methods: We reviewed 7718 consecutive femoral heads from 7286 patients removed over a 4-year period (2001?2004). There were 4211 women and 3507 men. The age range was from 13 to 96, average age was 60. There were 7349 hips with a preoperative clinical diagnosis of osteoarthritis and 369 with a preoperative clinical diagnosis of osteonecrosis.
Results: SIF was diagnosed histologically as the primary process in 501 of 7718 resected femoral heads (6.5%). The age range in these patients was from 20 to 93, with an average age of 68, in which 79% (394 hips) were over 60. They were 305 hips in women and 196 in men. The affected side was the right one in 253 hips and left in 248. The prevalence of SIF in cases with a preoperative diagnosis of osteoarthritis was 6.3% (460 of 7349), and with osteonecrosis was 11.1% (41 of 369). In all cases, callus and granulation tissue were observed histologically along the fracture line.
Conclusions: In this large series of total hip replacements SIF as the cause of disease was diagnosed histologically in 6.5% of the surgically removed femoral heads.
Subchondral insufficiency fracture of the femoral head (SIF) is a recently recognised condition and several clinical characteristic appearances have been reported. The patients are mostly older women with osteoporosis; however few cases have been seen in renal transplantation cases.2?4 Shortly after the onset of pain, radiographic changes are unremarkable; however, magnetic resonance imaging (MRI) has been reported to show a pattern of bone marrow oedema associated with an irregular low intensity band paralleling the articular surface. MRI may thus be considered useful for the diagnosis of SIF.2 3 The concept of subchondral insufficiency fracture has now been expanded to include the knee and shoulder joint.5 6
As subchondral collapse is commonly observed in patients with symptoms of osteonecrosis in any joints, previous reports of SIF have stressed the importance of its differentiation from osteonecrosis by describing its characteristic clinical and anatomical appearances.1?6
In this study, we have investigated the prevalence of SIF in a series of surgical specimens obtained at the time of total hip replacement.
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MATERIALS AND METHODS |
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The age range was from 13 to 96, with an average age of 60. They were 4211 women and 3507 men (F:M; 1.20:1.0). The reviewed materials included gross photographs, specimen radiographs, microscopic sections in each case.
Among the 7718 hips, 7349 femoral heads had a preoperative diagnosis of osteoarthritis. The age range was from 13 to 96 (average: 61) and 4026 were women and 3323 men (F:M; 1.21:1.0). There were 369 cases that had a preoperative diagnosis of osteonecrosis, in which the age range was from 13 to 85 (average: 41) and 185 were women and 184 men (F:M; 1.01:1.0).
Tissue preparation
In our
department, all femoral heads removed at surgery are photographed
intact and then fixed in 10% formalin solution. In each case, a 5 mm
thick mid coronal section is obtained using a band saw, and is first
photographed and then radiographed using low voltage x-rays
(Faxitron, Buffalo Grove, IL, USA) and fine-grain films (Kodak,
Rochester, NY, USA). After decalcification in 5% nitric acid
solution, the sections are processed, embedded in paraffin and 5-?m
thick glass mounted sections are prepared, which are routinely
stained with haematoxylin and
eosin.
Histopathological criteria of subchondral
fracture
The morphological criteria for diagnosis of subchondral
fracture were based on the previously published criteria.9
10 On gross examination, a linear narrow and irregular whitish
grey zone in the bone marrow space paralleling the subchondral bone
endplate is generally seen. Microscopically, this area consists of
irregularly arranged fracture callus, reactive cartilage and
granulation tissue. It should be noted that as all fracture leads to
some bone and bone marrow necrosis on either side of the fracture
line, small segments of necrotic bone trabeculae may be observed.11 12
However, such necrotic regions will be observed only around the
fracture line and there will be no evidence of antecedent bone
infarction or its zonal pattern. (Localised microfractures often
observed in the superficial subarticular bone in osteoarthritis are
not considered as SIF. In osteoarthritis, fractured bone trabeculae
are generally thick, while those in SIF are thin and sparse.)
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RESULTS |
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The prevalence of SIF in cases with a preoperative
clinical
diagnosis of osteoarthritis was 6.3% (460 of 7349), while in
osteonecrosis it was 11.1% (41 of 369).
The prevalence of osteoarthritis, osteonecrosis and SIF in each decade is described in fig 3. From the third to seventh decades, the prevalence of SIF was about 3?6%, while that in the eight and ninth decades was about 8?9%.
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Histopathological findings
Gross examination of the resected femoral heads showed relatively
spherical femoral heads with thinning of the articular cartilage or
partially detached flaps of articular cartilage (about 0.5?2.5 cm in
the greatest dimension) on the superolateral articular surfaces. On
the examination of mid-coronal cut sections, a notched linear shaped
zone of white and grey tissue, usually paralleling the subchondral
bone endplate, was observed and consisted of fracture callus,
reactive cartilage, and granulation tissue. In the surrounding tissue
there was focal resorption of bone by active osteoclasts and
replacement by vascular granulation tissue. Thin disconnected bone
trabeculae indicative of osteopenia were observed in the remaining
area of some of the femoral heads. Histology of the articular
cartilage overlying the fractured region showed fibrillation or mild
thinning; however, the articular cartilage was viable.
On the specimen radiograph, there was patchy osteosclerosis, which was microscopically confirmed as microcallus.
A representative case is shown in fig 4.
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DISCUSSION |
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Patients with SIF clinically have generally been reported to be mostly older patients with osteopenia.2?4 However, in this study rare cases of SIF were observed in younger adults about 20?40.14
In those cases with a preoperative diagnosis of osteoarthritis, the clinical diagnosis was probably based on the clinical symptoms and radiographically by early disappearance of the joint space; however, some cases of SIF have been reported to undergo rapid joint space narrowing subsequently resulting in a rapid joint destruction.15 16
Before the concept of SIF had been introduced in 2000,9 the majority of the SIF cases reported here would have been diagnosed histologically as osteonecrosis, presumably based on the small foci of necrosis caused by the fracture. Histopathologically, the most characteristic finding of SIF is the presence of fracture callus and granulation tissue along both edges of the fracture line. Although small segments of necrotic bone trabeculae may be observed around the fracture in SIF, such necrotic regions are observed only around the fracture line and there is no evidence of antecedent bone infarction or its zonal pattern.9
In the majority of cases with osteoarthritis, isolated microfractures are often observed in the superficial eburnated lesion. However, such lesions can be distinguished from SIF based on the lack of a linear fracture line and the presence in osteoarthritis of sclerotic bony changes, loss of cartilage in the subchondral area, cysts osteophytes, etc.
Some cases of SIF have been reported to undergo collapse necessitating surgery, while other cases of SIF radiographically have been reported to heal after conservative therapy.2 3 17 The prognosis of SIF may depend on a number of variables, including the degree of osteopenia, activity, weight and the extent of fracture, as well as the initial treatment. The appropriate initial treatment of an insufficiency fracture may alter the prognosis.
The chief limitation of this study was the lack of clinical and radiographical information available to us; however, our main purpose is to document the histopathological prevalence of SIF based on a review of the surgical specimens. The significance of clinically recognising its prevalence appears to us to lie in its early recognition and management.
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FOOTNOTES |
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Competing interests: None.
Published Online First 25 May 2007
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REFERENCES |
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