DOI:10.2214/AJR.07.3592
AJR 2008; 191:1010-1015
© American Roentgen Ray Society
Comparison of Planar Scintigraphy Alone and with SPECT for the Initial Evaluation of Femoral Neck Stress Fracture
L. Ray Bryant1,
Won S. Song1,2,
Kevin P. Banks1,
Liem T. Bui-Mansfield1,2 and
Yong C. Bradley1,2
1 Department of Radiology and Nuclear Medicine, Brooke Army Medical Center, Fort
Sam Houston, TX 78234.
2 Uniformed Services University of the Health Sciences, Bethesda, MD.
Received December 27, 2007;
accepted after revision April 13, 2008.
Address correspondence to K. P. Banks
(kevin.banks{at}amedd.army.mil).
The opinions and assertions contained herein are those of the authors and
should not be construed as official or as representing the opinions of the
Department of the Army or the Department of Defense.
Abstract
OBJECTIVE. The objective of our study was to compare the accuracy of
planar scintigraphy alone versus planar scintigraphy with SPECT for the
initial evaluation of femoral neck stress fractures in a young military
population.
MATERIALS AND METHODS. We retrospectively identified 38 patients who
had undergone planar scintigraphy and 33 patients who had undergone planar
scintigraphy and SPECT before MRI of the hips over a 6-month period for
evaluation of suspected femoral neck fracture. Data were analyzed regarding
the sensitivity and specificity of bone scanning alone and with SPECT for
detecting femoral neck stress fracture and grading fractures as low grade
(grades I and II) or high grade (grades III and IV).
RESULTS. Twelve fractures were identified in the group who underwent
planar scintigraphy alone and 13 in the group who underwent planar
scintigraphy with SPECT. The sensitivities of planar scintigraphy alone and
with SPECT were 50% and 92.3%, respectively (p = 0.03). The accuracy
of each technique for the detection of high-grade fractures was 12.5% and 70%,
respectively (p = 0.025).
CONCLUSION. Planar scintigraphy with SPECT had a higher sensitivity
and accuracy in assessing the grade of femoral neck stress fractures than
planar scintigraphy alone. The results of this study suggest that SPECT should
be performed with planar bone scintigraphy for the evaluation of patients with
suspected femoral neck stress fractures.
Keywords: femoral neck • hip • nuclear medicine • planar scintigraphy • SPECT • sports medicine • stress fractures
Introduction
Stress fractures are a common occurrence in the military recruit
population, occurring most commonly in the lower extremity
[1–5].
Conventional planar scintigraphy has been considered highly sensitive in
diagnosing femoral neck stress fractures
[6,
7], but many case reports of
stress fractures with negative bone scanning findings appear in the literature
[8–12].
In one case report, investigators recommended that the addition of SPECT to
planar scintigraphy may be useful in diagnosing femoral neck stress injuries
[11]; however, this approach
has never been evaluated to our knowledge.
It is imperative that femoral neck stress fractures are discovered at the
earliest stages to begin treatment and avoid progression to displaced
fracture. In our institution, we encountered two cases of high-grade femoral
neck stress fracture with normal planar scintigraphy findings that were
diagnosed on MRI. On March 1, 2007, we began performing SPECT on all patients
with clinically suspected femoral neck stress fractures. We report our
experience with this new technique.
Materials and Methods
The study was conducted retrospectively and was approved by our
institution's committee on human research with a waiver for the requirement of
written consent. The study was compliant with HIPAA regulations. Between
September 1, 2006, and February 28, 2007, 38 patients underwent planar
scintigraphy before MRI of the hips and between March 1, 2007, and August 31,
2007, 33 patients underwent planar scintigraphy with SPECT before MRI of the
hips for suspected femoral neck stress fracture.
Imaging Protocols
The planar scintigraphy protocol included initial static images obtained 3
hours after injec tion of 25 mCi (925 MBq) of 99mTc–methylene
diphosphonate using a dual-headed gamma camera (E-Cam, Siemens Medical
Solutions) with high-resolution collimators. Before acquisition of planar
images, all patients were asked to empty their bladders. Images of the body
from the feet to the lumbar spine were immediately obtained after magnified
static images of the hips. The anterior and posterior magnification views were
obtained by decreasing the field of view to include only the bony pelvis and
hips while maintaining a 128 x 128 matrix size. Additional spot images
were also obtained, including an inferior view of the pelvis. In instances in
which significant bladder activity was identified, electronic masking was
performed during processing to improve normalization for interpretation.
The 33 patients who also underwent SPECT voided before SPECT acquisition.
Images were obtained using a dual-headed gamma camera and high-resolution
collimators (40 projections, 30 seconds per projection, 1.45 zoom, and 128
x 128 matrix).
In all patients, MRI of the hip was performed on a 1.5-T MR scanner
(Eclipse, Picker) using our institution's standard unenhanced hip
musculoskeletal protocol. The protocol includes T1-weighted (TR/TE, 576/17.0;
5-mm slice thick ness; 1-mm gap) and STIR (2,000/60; inversion time, 100
milliseconds; 5-mm slice thickness; 2-mm gap) imaging through the entire
pelvis using a body coil. The field of view for each of these sequences was 38
cm2 with a 192 x 256 matrix. The body coil was exchanged for
a 4-channel phased-array wrap coil shaped to the symptomatic hip. A small
field of view (20 cm2) with the same matrix size was used, and
axial and coronal T2-weighted sequences with fat saturation (3,000/96, 4-mm
slice thickness, 1-mm gap) as well as a sagittal proton density sequence with
fat saturation (2,000/15, 4-mm slice thickness, 1-mm gap) were performed.
Scintigraphic images were interpreted by a nuclear medicine–trained
physician and the MR images were interpreted by a fellowship-trained
musculoskeletal radiologist. Fractures were classified on the basis of MRI
findings as low grade, grade I or II, or as high grade, grade III or IV, using
the grading scale by Arendt and Griffiths
[13]
(Table 1).
Data Analysis
In this study, the independent variable is diagnostic imaging technique
(planar scinti graphy alone vs planar scintigraphy with SPECT). The dependent
variables are sensitivity, speci ficity, and fracture grading. The null
hypothesis is that there is no significant difference between the imaging
techniques in sensitivity, specificity, or fracture grading. The appropriate
test is a 2 x 2 contingency test. The 95% CI for our binomial
probability was calculated using the Wald equa tion.
Results
There were 34 women and four men in the planar scintigraphy group with an
average age of 29.2 years (range, 18–66 years). There were 28 women and
five men in the planar scintigraphy and SPECT group with an average age of
24.7 years (range, 17–64 years). This female predominance of stress
injuries in our study group is similar to other institutions treating military
trainees, according to a report by the Subcommittee on Body Composition,
Nutrition, and Health of Military Women, Committee on Military Nutrition
Research at the Institute of Medicine
[14].
View larger version (169K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A —18-year-old woman who complained of right hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show subtle increased scintigraphic activity in medial margin of right
femoral neck suspect for stress fracture.
|
|
View larger version (200K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B —18-year-old woman who complained of right hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show subtle increased scintigraphic activity in medial margin of right
femoral neck suspect for stress fracture.
|
|
View larger version (126K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C —18-year-old woman who complained of right hip pain. D,
Small-field-of-view coronal images using STIR technique (C) and
T2-weighted technique with fat saturation (D) of right hip show
subchondral bone marrow edema along compressive side of femoral neck
consistent with stress fracture.
|
|
View larger version (162K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D —18-year-old woman who complained of right hip pain.
Small-field-of-view coronal images using STIR technique (C) and
T2-weighted technique with fat saturation (D) of right hip show
subchondral bone marrow edema along compressive side of femoral neck
consistent with stress fracture.
|
|
The average length of time between either planar scintigraphy alone or
planar scintigraphy with SPECT and MRI of the hips was 32.4 days (range,
1–94 days) and 20 days (range, 1–97 days), respectively. SPECT
correctly identified 12 of 13 femoral neck stress fractures (sensitivity =
92.3%) and planar scintigraphy, six of 12 femoral neck stress fractures
(sensitivity = 50%) (p = 0.03). Planar scintigraphy correctly
identified only one of eight high-grade fractures, whereas SPECT detected
seven of 10 high-grade fractures (p = 0.025). Despite p
values < 0.05, sensitivity and fracture grading did not meet statistical
significance after Bonferroni correction for multiple comparisons.
Planar scintigraphy alone and planar scintigraphy with SPECT had similar
specificity (100% and 85%, respectively) and similar accuracy for identifying
low-grade fractures (75% and 67%, respectively). One patient identified as
having a fracture by SPECT had bone marrow edema in the femoral neck on MRI
that was due to reactive changes adjacent to a herniation pit versus
femoroacetabular impingement.
Discussion
Prior studies have reported a high sensitivity for planar scintigraphy in
the detection of stress fractures of the hip
[6,
7]. However, many case reports
have documented stress injuries that were not identified on planar
scintigraphy
[8–12]
and, given the widespread use of MRI, stress fractures of the hip may be
increasingly recognized. MRI was used as the gold standard because of its high
sensitivity and specificity in the diagnosis of stress fracture. Bone
scintigraphy detects a stress fracture when the osteoblasts put down new bone.
In contrast, MRI is able to detect periosteal and bone marrow edema due to the
action of osteoclasts, which occurs before that of osteoblasts in the process
of bone remodeling.
View larger version (168K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2A —22-year-old woman who complained of left hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show mildly increased scintigraphic activity in bilateral femoral
necks; this finding was considered to be stress changes without discrete
stress fracture.
|
|
View larger version (172K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2B —22-year-old woman who complained of left hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show mildly increased scintigraphic activity in bilateral femoral
necks; this finding was considered to be stress changes without discrete
stress fracture.
|
|
View larger version (165K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2C —22-year-old woman who complained of left hip pain. Coronal
STIR MR image through bilateral hips and pelvis shows abnormal subchondral
bone marrow edema in both femoral necks, with left more significantly affected
than right.
|
|
View larger version (143K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2D —22-year-old woman who complained of left hip pain.
Small-field-of-view coronal T2-weighted images obtained using fat-saturation
technique of right (D) and left (E) hips more clearly depict
bilateral stress fractures than A–C.
|
|
View larger version (170K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 2E —22-year-old woman who complained of left hip pain.
Small-field-of-view coronal T2-weighted images obtained using fat-saturation
technique of right (D) and left (E) hips more clearly depict
bilateral stress fractures than A–C.
|
|
Although femoral neck stress fractures can show significant uptake on
planar scintigraphy, most low-grade stress fractures and some high-grade
stress fractures show subtle or mild radiotracer uptake (Figs.
1A,
1B,
1C,
1D and
2A,
2B,
2C,
2D,
2E). The benefit of the
improved contrast resolution in SPECT emphasizes these subtle findings and
illustrates the severity of these lesions more accurately, particularly in
high-grade stress fractures (Figs.
3A,
3B,
3C,
3D,
3E and
4A,
4B,
4C,
4D).
View larger version (197K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3A —25-year-old woman who complained of right hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show no focal activity suspect for stress fracture or other acute
osseous pathology.
|
|
View larger version (198K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3B —25-year-old woman who complained of right hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show no focal activity suspect for stress fracture or other acute
osseous pathology.
|
|
View larger version (110K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3C —25-year-old woman who complained of right hip pain. Coronal
SPECT image of hips and pelvis reveals abnormal focal activity
(arrow) in medial margin of right femoral neck, near lesser
trochanter.
|
|
View larger version (167K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3D —25-year-old woman who complained of right hip pain.
Small-field-of-view coronal images obtained using T2-weighted technique with
fat saturation (D) and STIR technique (E) of right hip show
subchondral bone marrow edema along compressive side of femoral neck
consistent with stress fracture.
|
|
View larger version (153K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 3E —25-year-old woman who complained of right hip pain.
Small-field-of-view coronal images obtained using T2-weighted technique with
fat saturation (D) and STIR technique (E) of right hip show
subchondral bone marrow edema along compressive side of femoral neck
consistent with stress fracture.
|
|
View larger version (100K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4B —18-year-old woman who complained of left hip pain. Coronal
SPECT image through bilateral hips and pelvis not only confirms left femoral
neck stress fracture, but also reveals unsuspected abnormal activity in right
femoral neck.
|
|
View larger version (150K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 4C —18-year-old woman who complained of left hip pain. Coronal MR
STIR image through bilateral hips and pelvis shows left femoral neck stress as
well as abnormal subchondral bone marrow edema in right femoral neck and joint
effusion, confirming presence of bilateral femoral neck stress fractures.
|
|
Our study population was composed of physically active young adults who are
very susceptible to stress fractures (Fig.
5A,
5B,
5C,
5D). The probability of a
femoral neck stress fracture in our study population is likely much higher
than in a civilian population. However, screening with MRI of the hips would
not be practical considering the large referral population. In addition, a
rapid and accurate assessment in our active population is essential to
determine treatment, prognosis, and the ability to return to duty.
View larger version (171K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5A —21-year-old woman who complained of right hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show no focal activity suspect for stress fracture or other acute
osseous abnormalities.
|
|
View larger version (185K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5B —21-year-old woman who complained of right hip pain. Anterior
(A) and posterior (B) planar magnification images of hips and
pelvis show no focal activity suspect for stress fracture or other acute
osseous abnormalities.
|
|
View larger version (125K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5C —21-year-old woman who complained of right hip pain.
Small-field-of-view coronal images obtained using T2-weighted technique with
fat saturation (C) and STIR technique (D) of right hip show
subchondral bone marrow edema along compressive side of femoral neck
consistent with stress fracture.
|
|
View larger version (128K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 5D —21-year-old woman who complained of right hip pain.
Small-field-of-view coronal images obtained using T2-weighted technique with
fat saturation (C) and STIR technique (D) of right hip show
subchondral bone marrow edema along compressive side of femoral neck
consistent with stress fracture.
|
|
SPECT showed a trend toward increased sensitivity for the detection of
stress fractures of the hip in this patient population with a p value
< 0.05 that approached but did not reach statistical significance, likely
because of the small number of fractures in each group
(Table 2). There was also a
trend toward improved accuracy of high-grade fracture detection for planar
scintigraphy with SPECT (Table
3) compared with the accuracy of planar scintigraphy alone
(Table 4). We believe this
improved accuracy was also due to the increased sensitivity of planar
scintigraphy with SPECT for identifying early stress changes. Planar
scintigraphy alone correctly identified only one of eight high-grade fractures
(grade III or IV). Of the MRI studies performed on the seven high-grade
fractures that were missed on planar imaging
(Fig. 6), five were requested
because of continued or worsening pain and two were performed to evaluate pain
despite non–weight bearing. One of the latter two patients had
previously been diagnosed with a low-grade stress fracture (grade I or II) on
planar scintigraphy.
View this table:
[in this window]
[in a new window]
|
TABLE 2: Femoral Neck Stress Fractures Identified on Planar Scintigraphy Alone
and on Planar Scintigraphy with SPECT
|
|
View larger version (21K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 6 —Bar graph shows sensitivity, specificity, and accuracy of
grading femoral neck stress fracture for planar scintigraphy alone
(white) and planar scintigraphy with SPECT (dark gray).
Difference in sensitivity, was not significant (p = 0.03, Fisher t
test) after Bonferroni correction for multiple comparisons. Difference in
grading for high-grade fracture was not significant (p = 0.025,
Fisher t test) after Bonferroni correction for multiple comparisons.
|
|
Our findings are limited by the retrospective design of this study and
because planar scintigraphy alone or with SPECT was not performed in
conjunction with MRI on initial presentation. It is possible, although
unlikely, that a patient could have sustained further injury during the time
interval between the two studies. Our study was also limited by the fact that
the sample size was nonconsecutive and was modest in the number of patients.
Because all of the patients underwent planar scintigraphy alone or planar
scintigraphy with SPECT and subsequent MRI of the hips based on a clinical
decision, selection bias is another consideration.
Early identification of femoral neck stress fracture is important to
prevent progression to a higher-grade fracture or to a displaced fracture,
which can potentially have devastating consequences such as avascular necrosis
of the femoral head necessitating early hip joint replacement with its own set
of complications. Our study results show a trend toward increased sensitivity
of planar scintigraphy with SPECT over planar imaging alone for the detection
of femoral neck stress fractures. The addition of SPECT to planar imaging
should be considered in a young active population with hip pain, although
further investigation in a prospective study is warranted.
References
- Gilbert RS, Johnson HA. Stress fractures in military recruits.
Mil Med 1966; 131:716
–721
- Haliel T, Amit S, Segal D. Fatigue fractures of tibial and femoral
shafts in soldiers. Clin Orthop 1976;118
: 35–43[Medline]
- Leveton AL. March (fatigue) fractures of the long bones of the
lower extremities and pelvis. Am J Surg1946; 71:222
–234[CrossRef]
- Proctor SE, Campbell TA, Pobelle M. March fracture of the tibia and
femur. Surg Gynecol Obstet 1944;78
: 415–422
- Wilson ES, Katz FN. Stress fractures: an analysis of 250
consecutive cases. Radiology 1969;92
: 481–486[Medline]
- Rizzo, PF, Gould ES, Lyden JP. Diagnosis of occult fractures about
the hip: magnetic resonance imaging compared with bone scanning. J
Bone Joint Surg Am 1993; 75:395
–401[Abstract/Free Full Text]
- Yasuyuki I, Okamura Y, Hironori O, et al. Comparison of
scintigraphy and magnetic resonance imaging for stress injuries of the bone.
Clin J Sport Med 2002;12
: 79–84[CrossRef][Medline]
- Milgrom C, Chisin R, Giladi M, et al. Negative bone scans in
impending tibial stress fractures: a report of three cases. Am J
Sports Med 1984; 12:488
–491[Abstract/Free Full Text]
- Keene JS, Lash EG. Negative bone scan in a femoral neck stress
fracture: a case report. Am J Sports Med1992; 20:234
–236[Free Full Text]
- Sterling JC, Webb RF Jr, Meyers MC, Calvo RD. False negative bone
scan in a female runner. Med Sci Sports Exerc1993; 25:179
–185[Medline]
- Bal BS, Sandow T. Bilateral femoral neck fractures with negative
bone scans. Orthopedics 1996;19
: 974–976[Medline]
- Wen DY, Propeck T, Singh A. Femoral neck stress injury with
negative bone scan. J Am Board Fam Med2003; 16:170
–174[Free Full Text]
- Arendt EA, Griffiths HJ. The use of MR imaging in the assessment
and clinical management of stress reactions of bone in high-performance
athletes. Clin Sports Med 1997;16
: 291–306[CrossRef][Medline]
- Subcommittee on Body Composition, Nutrition, and Health of Military
Women, Committee on Military Nutrition Research, Institute of Medicine.
Reducing stress fractures in physically active military
women. Washington, DC: National Academies Press,1998
: 9–28.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Abstract
Introduction
