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Age / Sex : 65 / F
Chief complaint: right inguinal pain for 9 months
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)
Courtesy: 김여주(Yoe Ju Kim), 인하대병원(Inha University Hospital)
Diagnosis: Bisphosphonate related subtrochanteric fracture
Discussion
Findings:
(a)
Anteroposterior
radiograph of pelvis shows beaked lateral margin of cortex of the
upper portion of femoral shaft, bilaterally with focal cortical hypertrophy,
suggesting stress (insufficiency) fracture. Incidentally, calcific tendinitis
is seen near greater trochanter of both femora as the gluteus medius and
minimus tendon attachment site.
(b)
Fat
suppressed T2 weighted image of right thigh also show beaked lateral margin of cortex
with cortical hypertrophy corresponding with the anteroposterior radiograph of
pelvis. Focal T2 high signal intensity edema is seen at intramedullary cavity
around the cortical hypertrophy.
Differential Diagnosis
1) stress fractures
((fractures involving normal bone subject to a repetitive stress)
2) pseudofractures of
osteomalacia
3) pathologic fractures
Discussion:
Fractures in proximal femur usually require
high energy if the bone mineralization is normal. Insufficiency fractures in
the osteoporotic population in this region are said to be rare. Fractures, or fracture
like conditions, within this area in the of high-energy trauma can occur in
other clinical settings but are either related to unusual causes, such as
pyknodysostosis or fluoride therapy, or provide differentiating radiographic
and clinical clues. Therefore, a transverse fracture of the proximal femur with
associated localized thickening of the lateral cortex in a postmenopausal woman
after low-energy trauma receiving long-term bisphosphonate therapy should be
considered diagnostic for a bisphosphonate related insufficiency fracture. It
seems a paradox that a fracture would be associated with bisphosphonate therapy
because bisphosphonates are prescribed for generalized osteoporosis to increase
bone mineral density and de crease the chance of fracture. Bisphosphonates function
by inhibiting bone resorption by suppressing osteoclasts through apoptosis. Although
this action results in increased bone mineral density, suppressed bone turnover
prevents remodeling and healing of cracks that occur in bone as a result of
normal activity, often referred to as microdamage. The technetium-99m–labeled
methylene diphosphonate bone scan appearance is that of a focus of increased
uptake within the lateral cortex of the affected proximal femur. MRI of the
pelvis revealed a thickened lateral cortex with a focus of abnormally high
signal. Involvement of the contralateral femur varies in the literature, ranging
from 20% to 64%. When the radiologist encounters fractures involving the
proximal femur in the setting of a low-energy inciting event, demographic and historical
information should be sought. This information, in conjunction with the
radiologic findings, can lead to a correct diagnosis.
References:
1. Porrino JA Jr, Kohl CA, Taljanovic M, Rogers LF.
Diagnosis of proximal femoral insufficiency fractures in patients receiving
bisphosphonate therapy. AJR. 2010 Apr;194(4):1061-4.
2. Lenart BA, Lorich DG,
Lane JM. More on atypical fractures of the femoral diaphysis. (reply to letter)
N Engl J Med 2008; 359:317–318
3. Lenart BA, Lorich DG,
Lane JM. Atypical fractures of the femoral diaphysis in postmenopausal women
taking alendronate. N Engl J Med 2008; 358:1304–1306
4. Kwek EB, Goh SK, Koh
JS, Png MA, Howe TS. An emerging pattern of subtrochanteric stress fractures: a
long-term complication of alendronate therapy? Injury 2008; 39:224–231
5. Goh SK, Yang KY, Koh
JS, et al. Subtrochanteric insufficiency fractures in patients on alendronate therapy:
a caution. J Bone Joint Surg Br 2007; 89:349–353
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