Sacral insufficiency fractures OS Schindler

Journal of Orthopaedic Surgery 2007;15(3):339-46
Sacral insufficiency fractures
OS Schindler
Droitwich Knee Clinic and Birmingham Arthritis and Sports Injury Clinic, Droitwich Spa, Worcestershire, United
Kingdom
R Watura, M Cobby
Department of Musculoskeletal Radiology, Frenchay Hospital, Bristol, United Kingdom
ABSTRACT
Purpose. To highlight difficulties in the diagnostic
process and the validity of imaging techniques for
sacral insufficiency fractures.
Methods. Records of 25 women aged 68 to 95 years
with sacral insufficiency fractures were reviewed.
Baseline blood biochemistry and haematology test
results were obtained. Pelvic anterior/posterior
radiography was undertaken for all patients;
additional computed tomography, technetium
bone scanning, and magnetic resonance imaging
were used in some. Treatments were based on the
severity of the injury and the patient’s mobility and
cooperativeness.
Results. Among the 25 women, 11 had bilateral and
14 had unilateral vertical sacral fractures. Associated
fractures included horizontal sacral fracture, fractures
of the os pubis and ilium. Symptoms included lower
back or buttock pain, abdominal pain, and those
emulating radiculopathy and myelopathy, including
leg weakness, sciatica, and urinary retention. The
mean delay in diagnosis was 9 (range, 1–28) days. The
mean recovery time between bilateral and unilateral
fractures was significantly different (22 [range, 12–33]
vs 14 [range, 8–36] weeks, p=0.01). No patient with
bilateral fractures regained her pre-injury mobility,
compared to 43% among those with unilateral
fractures (p=0.02, Fisher’s exact test). Computed
tomography was the most reliable imaging technique;
technetium bone scanning was highly sensitive
but non-specific; magnetic resonance images of the
fractures may mimic metastatic disease.
Conclusion. With the increase in the elderly population,
sacral insufficiency fractures may become epidemic
in future. Primary and secondary osteoporoses are
common causes. Once a diagnosis is established, in
most cases treatment is simple but recovery may be
protracted and full mobility curtailed.
Key words: fractures, spontaneous; pelvic bones; sacrum
INTRODUCTION
Sacral insufficiency fractures were first reported in
1982.1 Awareness of these injuries is inadequate,
despite publication of several case reports since
then.1–6 Diagnosis is often delayed or missed. Most
patients are elderly and present with intractable
lower back pain; some complain of leg weakness but
neurological impairment is rarely detectable.7 The
Address correspondence and reprint requests to: Mr Oliver S Schindler, Droitwich Knee Clinic, St Andrews Road, Droitwich
Spa, Worcestershire WR9 8YX, United Kingdom. E-mail: schindler@doctors.net.uk
Journal of Orthopaedic Surgery
340 OS Schindler et al.
patients are often misdiagnosed as having spinal
stenosis, degenerative disc disease, spondylolisthesis,
spondylosis, compression fractures, or neoplasms.6,8,9
Degenerative changes of the lumbar spine are often
considered to be the only cause of the discomfort.
Routine radiography of the spine and pelvis is usually
inconclusive, and blood biochemistry may reveal
elevated alkaline phosphatase levels.8,10 Patients may
present varying signs and symptoms.2,3,11–13 Failure to
recognise a sacral insufficiency fracture can lead to
unnecessary and potentially dangerous investigations
especially if occult malignancy is suspected.3,8 We
report 25 cases of sacral insufficiency fracture without
any history of trauma. Difficulties in the diagnostic
process and the validity of imaging techniques are
highlighted.
MATERIALS AND METHODS
Records of 25 women aged 68 to 95 (mean, 83)
years with sacral insufficiency fractures presenting
between November 1999 and January 2001 were
reviewed. Only 4 patients initially presented to our
hospital, all others were first seen at community
hospitals or medical units. None had a history of
trauma. Ambulance crew found 4 patients lying on
the floor; all denied having fallen but claimed sudden
leg weakness requiring them to sit down. 12 patients
reported pain or discomfort commencing 7 to 45
(mean, 28) days before presentation.
Baseline blood biochemistry and haematology
test results were obtained. Pelvic anterior/posterior
radiography was undertaken for all patients; additional
imaging was performed in 15 patients using computed
tomography (CT), in 13 using technetium bone
scanning, and in 5 using magnetic resonance imaging
(MRI). Two patients also underwent needle biopsy
of the sacrum. The diagnoses of sacral insufficiency
fractures were based on blood analysis and pelvic
imaging, and established by exclusion of vascular,
neurological, intra-abdominal abnormalities.
Treatments were based on the severity of the
injury and the patient’s mobility and cooperativeness.
In cases of unilateral sacral and pubic symphysis
fractures, patients were allowed to mobilise with
crutches or a Zimmer frame. In very frail patients
and those with bilateral and/or horizontal fractures,
a period of bed rest was prescribed to control pain
and to prevent fracture displacement.9,12 Weight
bearing was not permitted for a minimum of 3 weeks.
Patients were then allowed progressive mobilisation
and followed up at least twice (3 and 6 months after
discharge) or more often if still symptomatic.
A combination of simple analgesia and intramuscular calcitonin (100–400 IU daily for up to 6
weeks) was used for pain control. Recovery time
between bilateral and unilateral fractures was
compared using the Mann-Whitney-Wilcoxon test.14
RESULTS
Of the 25 women, 11 had bilateral and 14 had unilateral
vertical sacral fractures (Table 1). Associated fractures
included horizontal sacral fracture (n=8, all occurring
with bilateral vertical sacral fractures), fractures of
the os pubis (n=14), and fracture of the ilium (n=1).
Clinical symptoms included lower back pain
(n=12), lower abdominal pain (n=5), epigastric pain
(n=3), loin pain (n=2), groin pain (n=6), dysuria (n=2),
and urinary retention (n=1). Neurological symptoms
included radiculopathy-emulating symptoms such
as limitation in straight leg raising and sciatic stretch
pain (n=5), myelopathy-emulating symptoms such as
wide-based, staggering gate, loss of proprioception,
and weakness (n=1), and generalised weakness of
both legs (n=3). Objective signs of neurological deficit
were present in 3 patients; 2 of whom had diminished
reflexes and altered sensation and one had urinary
retention.
Blood biochemistry was abnormal in 16 patients;
12 had increased serum alkaline phosphatase levels
of up to 250 IU/L; 7 of the 12 also had decreased
serum calcium levels, of whom 2 also had decreased
total serum protein levels. Other abnormal findings
included increased white blood cell count (n=3),
increased C-reactive protein level (n=7), decreased
serum vitamin-D level (n=3). Abnormal levels of
blood/plasma glucose, sodium, potassium, urea,
creatinine, and liver enzymes were related to preexisting co-morbidities and hence not reported.
Haemoglobin and haematocrit levels of most patients
were in the lower part of their reference range for age
and sex.
Diagnoses were delayed by a mean of 9 (range,
1–28) days. In one patient the sacral fractures were
missed; she was discharged but re-admitted 3 months
later with a displaced iliac wing fracture resulting in
a floating hemi-pelvis. Primary osteoporosis was the
only cause in 20 patients, 6 of whom had received
hormone replacement therapy for at least 5 years.
Three patients had osteoporosis secondary to vitaminD deficiency, hyperparathyroidism, or long-term
corticosteroid treatment. One patient had received
localised radiotherapy after surgical excision of a
rectum carcinoma.
The mean duration of hospital stay was 10 (range,
Vol. 15 No. 3, December 2007
Sacral insufficiency fractures 341
Table 1
Demographic and clinical details of 25 female patients
Patient
No.
Age Radiological
(years) tests*
Fracture
location†
Blood
chemistry‡
Symptoms§
AP#, Ca$, TP$
LBP
LAP
AP#, Ca$, TP$,
CRP#, VitD$
CRP#
LBP, RLER,
UR
LBP, LGP
1
88
XR, BS, CT
2
3
92
85
XR, BS
XR, BS, MRI
BVS, HS,
LPR
RVS, RPR
BVS, HS
4
72
XR, CT
RVS, LPR
5
85
XR
RVS/IW, RPR AP#
6
7
71
95
XR, BS
XR, MRI
RVS, RPR
LVS, LPR
8
76
XR
9
10
75
91
XR, BS, CT
XR, BS, CT
11
87
12
13
14
15
16
17
Time to Time to Follow-up Mobility Remarks
diagnosis recovery (months) Pre/post
(days)
(weeks)
injury❘❘
28
24
9
W/C
3
7
16
33
6
12
W/W
W/NW
14
12
24
W/C
RGP
-
36
6
W/F
AP#, CRP#
-
RGP
LLR
12
11
12
21
12
6
W/W
S/S
RVS, BPR
WBC#
BLEW
4
12
3
W/NW
AP#, Ca$
-
LBP, LEP
LBP, RLER
2
12
16
32
18
18
W/C
W/S
XR, BS
BVS, HS
BVS, HS,
RPR
BVS, RPR
LBP, RLER
12
24
9
S/S
90
78
79
86
70
91
XR, CT
XR, CT
XR, BS, CT
XR, MRI, CT
XR
XR, BS, CT
LVS
RVS
BVS, HS
BVS, RPR
LVS
BVS, HS
LAP
LAP
LEP, DU
LAP, RGP
LBP, LEP
BLEW, LBP
4
3
14
7
1
10
16
12
12
16
9
24
9
12
18
12
9
24
C/C
W/S
S/C
W/C
W/W
W/F
Deep vein thrombosis
18
19
20
88
68
95
XR, MRI, CT
XR, BS, MRI
XR, CT
RVS, RPR
LVS
BVS, HS,
LPR
AP#, Ca$,
CRP#
AP#, Ca$
CRP#
AP#, WBC#
AP#, Ca#,
VitD$
CRP#, WBC#
AP#, Ca$, TP#
RLER
LLP, LLT
LGP
9
21
5
12
8
-
12
9
-
S/S
W/W
F/-
21
22
23
73
77
90
XR, BS, CT
XR, CT
XR, CT
LVS, LPR
RVS
BVS, HS
LBP, BLEW
LBP, LLER
MP
9
6
11
10
8
20
21
24
W/S
W/W
S/C
24
25
85
81
XR, BS
XR, BS, CT
BVS
RVS, RPR
AP#, Ca$,
CRP#
TP$, VitD$
AP#
Died of pulmonary
embolus 21 days after
presentation
Deep vein thrombosis
8
8
16
12
18
9
F/F
C/F
LAP, DU, LBP
LBP
Osteomalacia & osteoporosis
Crush fracture of L4 one
year later
Missed diagnosis; floating hemi-pelvis after
displaced fracture
Polymyalgia rheumatica
radiotherapy after excision of rectum carcinoma
Died of pulmonary complication at 5 months
Hyperparathyroidism
Alzheimer’s disease
-
-
§
XR denotes plain radiography, CT computed tomography, BS technetium bone scanning, and MRI magnetic resonance imaging
R/L/BVS denotes right/left/bilateral vertical sacrum, R/L/BPR right/left/bilateral pubic ramus, HS horizontal sacrum, and IW iliac wing
AP denotes alkaline phosphatase, Ca calcium, TP total protein, CRP C-reactive protein, WBC white blood count, and VitD vitamin D
R/LLER denotes right/left lower extremity radiculopathy, R/L/BLEW right/left/bilateral lower extremity weakness, MP myelopathy, LAP lower
abdominal pain, R/L/BGP right/left/bilateral groin pain, R/L/BLP right/left/bilateral loin pain, R/LLT right/left loin tenderness, U/LEP upper/
lower epigastric pain, DU disuria, and UR urinary retention
❘❘
W denotes walker, S stick/cane, C crutch, F frame, and NW non-walker
*
†
‡
6–24) weeks. Two patients died, one from pneumonia
at 3 weeks, another from pulmonary embolus at 5
months. Recovery was considered complete when
the fracture had consolidated and patient’s mobility
had plateaued. The severity and complexity of sacral
insufficiency fractures correlated with the recovery
time. Patients were followed up until recovery
(mean, 13; range, 3–24 months). The mean recovery
time between bilateral and unilateral fractures was
significantly different (22 [range, 12–33] vs 14 [range,
8–36] weeks, p=0.01).
Prior to presentation, 16 patients were walking
unaided, 5 walked with sticks, 2 used elbow crutches,
and 2 a walking frame. At the final follow-up, of 22
patients (2 had died and one was lost to follow-up),
only 5 were able to walk unaided, 6 walked with
sticks, 7 used elbow crutches, 3 a walking frame, and
one remained wheelchair bound. Nine (38%) patients
regained their pre-injury mobility level, while 15 (65%)
dropped at least one level. No patient with bilateral
Journal of Orthopaedic Surgery
342 OS Schindler et al.
Table 2
Comparison of studies describing patients with sacral insufficiency fractures
Study
Lourie,1 1982
Ries,32 1983
Cooper et al,23 1985
De Smet and Neff,10 1985
Schneider et al,33 1985
Rawlings et al,4 1988
Leroux et al,28 1993
Weber et al,12 1993
Gotis-Graham et al,3 1994
Grasland et al,8 1996
Dasgupta et al,2 1998
Chen et al,38 1999
Verhaegen and Sauter,6 1999
Present study
No. of
patients
3
4
12
9
23
16
10
20
20
16
10
14
1
25
Mean age Hospital Follow-up
(years)
stay (days) (months)
80
80
66
62
70
71
70
79
74
81
70
70
85
83
21
23
42
71
6.2
16
6.5
6–9
30
18–41
1.5
13
Sacral
Associated Neurological
fracture (bifracture
deficit (%)
vs uni-lateral)
(%)
[%]
100/0
50/50
75/25
55/45
78/22
30/70
35/65
60/40
81/19
64/36
100/0
44/56
66
0
75
88
≥61
63
70
80
75
63
60
29
0
56
100
50
25
0
12
50
0
0
19
0
52
LBP denotes lower back pain, LP leg pain, SP sacral pain, BP buttock pain, LAP lower abdominal pain, and GP groin pain
XR denotes plain radiography, CT computed tomography, BS technetium bone scanning, and MRI magnetic resonance imaging
‡
OP denotes osteoporosis, RA rheumatoid arthritis, CS corticosteroid therapy, and RAD radiation therapy
*
†
fractures regained her pre-injury mobility, compared
to 43% of those with unilateral fractures; this difference
was significant (p=0.02, Fisher’s exact test).
DISCUSSION
Stress fractures are classified into fatigue and
insufficiency fractures.15 Fatigue fractures occur when
abnormal stress is applied to bone with normal elastic
resistance; insufficiency fractures are caused by normal
(physiological) stress applied to bone with deficient
elastic resistance.15 Sacral insufficiency fractures occur
mostly in women aged >55 years,2,7,8,16 whose bone
strength is inadequate to withstand normal repetitive
stress.17 Table 2 compares studies describing patients
with sacral insufficiency fractures.
Bone metabolism and bone remodelling capacity
decreases with age and diminished hormone
production. Henceforth, the ability of bone to react
to physiological stress through strengthening its
internal trabecular scaffold is substantially reduced,
as described by Wolff’s law.18–20 The compressive
strength of trabecular bone is proportional to the
square of its density.21 A decrease in density by a factor
of 2 consequently reduces its compressive strength by
a factor of 4.18 Therefore, involutional osteoporosis is
the main cause for sacral insufficiency fractures.7,10,22
Underlying pathologies of osteoporosis/osteopenia
include: prolonged corticosteroid or phenytoin
treatment, Cushing’s syndrome, primary bilary
cirrhosis, osteomalacia, rheumatoid arthritis,
myelomatous disease, radiotherapy, and endocrine
disorders such as hyperparathyroidism.2,3,7,8,10,16
Predominant symptoms are lumbar back or
buttock pain with some patients presenting leg
weakness and inability to walk.1,7,23 Although
neurological symptoms emulating radiculopathy
and myelopathy are present in up to 70% of patients,
objective neurological abnormalities such as sphincter
dysfunction or leg paraesthesia are uncommon (2–
14%).1,4,8,12,22,24,25 The pathophysiology of neurological
manifestations remains unknown.
According to the Denis classification, most sacral
insufficiency fractures are located within zone 1 of the
sacral body (Fig. 1), in contrast to traumatic fractures
that occur in zone 2 along the sacral foraminae.13,24,26,27
Fractures usually display a vertical pattern extending
parallel to the sacro-iliac joint and lateral to the
sacral foramina; neurological deficits are therefore
uncommon.12,23,25,28 The weight of the upper body
transmitted through the spine may be responsible
for this fracture pattern.23 Bilateral vertical sacral
fractures (present in 40% of our cases) are likely to
be connected by a horizontal fracture through the
upper sacral body (Figs. 2 and 3). This fracture is
considered a secondary development caused by
continued stress, and classified further according
to the degree of angulation and displacement in the
sagittal plain.23,29,30 In such cases, overt listhesis may
Vol. 15 No. 3, December 2007
Clinical
symptom*
Biopsy (%)
LBP, LP
LBP, LP
SP, LP
GP, SP
LBP, LP
LBP, BP
LBP
LBP, SP
SP, BP
LBP, LP
LBP, SP
LBP
LP
LBP, LAP
0
0
0
66
9
0
40
0
25
0
8
Sacral insufficiency fractures 343
Alkaline
phosphatase
increase (%)
Sensitivity† (%)
XR
CT
BS
MRI
OP
RA
CS
RAD
Others
100
33
19
44
80
48
0
25
100
100
6
15
30
5
20
31
10
36
0
12
100
100
100
100
100
100
95
58
100
100
88
100
100
100
100
100
100
100
73
100
100
100
100
100
67
100
100
83
60
100
25
33
70
25
40
65
50
62
10
57
100
80
8
22
18
5
30
60
-
16
11
4
37
40
5
10
12
20
4
50
33
10
5
12
36
-
22
4
19
20
15
5
12
10
7
16
result in neurological deficits of the saddle area.
Associated fractures are seen in 25 to 80% of
patients having sacral insufficiency fractures.3,8,12,23,31
Pubic rami fractures (Fig. 4) are most common,
followed by vertebral compression fractures, iliac
wing fractures (Fig. 5), and intertrochanteric hip
fractures.3,6,8,10 Plain radiography combined with
technetium bone scanning are mostly sufficient for
detecting associated fractures.
Although pain usually resolves within 4 to 6 weeks
post injury, general mobility decreases substantially.
Previous reports have failed to highlight the disability
aspect associated with sacral insufficiency fractures,
and its major socio-economic consequences.3,9,12
Blood test results are usually unremarkable, apart
from mild-to-moderate elevation of the serum alkaline
phosphatase level.2,8,10 Serum calcium, phosphorus,
alkaline phosphatase, and vitamin-D levels should be
determined in order to exclude metabolic bone disease.
Serum protein electrophoresis is recommended when
multiple myeloma is suspected.
Depending on the preference of the surgeon, a
variety of imaging techniques are used to establish
the diagnosis. On plain radiographs, stress fractures
through cancellous bone of osteoporotic patients
are difficult to detect, especially in the sacrum (Fig.
6).32,33 The radiographic signs of sclerosis due to
trabecular compression and callus formation may be
subtle, owing to trabecular rarification and delay in
the development of endosteal callus in osteoporotic
Predisposing disease‡ (%)
bone.1,23,28 Overlying bowel and calcified iliac arteries
may further obscure bony details (Fig. 5). Associated
pubic rami fractures (seen in up to 80% of patients
with sacral insufficiency fractures) are often the only
abnormality noted on pelvic radiographs. Diagnosis
based on plain radiography alone was correct in only
12% of our patients, although in retrospect 32% had
discernable sacral fractures. Whether pelvic inlet
and outlet view radiographs increase the validity of
assessment remains unresolved. In our series, such
views did not appear to be helpful.
When plain radiography is inconclusive,
technetium bone scanning is highly sensitive and able
to detect occult fractures of the pelvic ring.3,32,33 The
pattern of uptake depends on the fracture configuration.
However, due to the proximity of the sacrum to the
detector of the gamma camera, scintigraphic activity
is often increased, especially in the prone position,
which makes it easy to overlook abnormalities. The
characteristic ‘H-shape’ configuration, representing
a combined bilateral vertical and horizontal sacral
fractures (Fig. 7), was present in 32% of our patients,
and in 15 to 68% of cases reported by others.3,10,16,28,32
Due to a lack of specificity, technetium bone scan
results may be dismissed as sacroiliitis or metastatic
disease, hence, a definitive diagnosis should not be
based on scintigraphy alone.7,12,34
CT is regarded as the gold standard in diagnosing
occult insufficiency fractures, because it can delineate
bony details.23,35–37 Fracture lines and cortical disruptions
Journal of Orthopaedic Surgery
344 OS Schindler et al.
(a)
1
2
(b)
3
Figure 1 According to
the Denis classification,
most sacral insufficiency
fractures are located in
sector 1.
Figure 2 (a) Coronal computed tomographic (CT) scan
at the level of S2 of a 75-year-old woman demonstrating
sclerotic fracture lines through both sacral alae medial to
the sacro-illiac joints and lateral to the sacral foraminae. (b)
Sagittal CT scan of the lumbo-sacral junction of a 91-yearold woman demonstrating an impacted horizontal fracture
across the lower S1 vertebral body. A lucent line is present
with a sclerotic margin, indicating a non-acute process.
Figure 3 Coronal T1-weighted magnetic resonance images
of a 79-year-old woman demonstrating bilateral vertical
sacral fractures connected by a horizontal sacral fracture.
The fractures assume a linear pattern of decreased signal
intensity alongside the sacro-iliac joints and through the
S1/2 sacral segment (arrows).
are accurately demonstrated and distinguished from
inflammatory or neoplastic processes.2,28 However,
false-negative CT results have been reported in 15 to
25% of cases.3,16 In a series of 14 patients with sacral
insufficiency fractures, sensitivity and specificity rates
of 36% for radiography and 88% for CT were reported;
for MRI, the sensitivity was 100% but specificity was
only 83%.38 Although MRI is the most sensitive tool,
fracture lines are best demonstrated using CT. Others
reported sensitivity and specificity figures of only
68% for CT while technetium bone scanning provided
a sensitivity of 100%.3 The routine use of scintigraphy
in diagnosing sacral insufficiency fractures was
therefore recommended. The presence of gas on CT
images is called the ‘vacuum phenomenon’.39 The gas
was located in the ventral part of the fractures or in
the adjacent sacro-iliac joints. It is an important sign
for differentiating between neoplasm and fracture;
the ‘vacuum phenomenon’ is generally not found in
patients with metastatic sacral disease.
Some authors considered MRI the more sensitive
diagnostic tool.16 Sacral insufficiency fractures have
decreased signal intensity on T1-weighted images
and increased signal intensity on T2-weighted
images, which are features consistent with marrow
oedema.17,16 The appearance of low signal areas in T1-
Figure 4 Anteroposterior radiograph of a 72-year-old
woman demonstrating chronic insufficiency fractures of the
right pubic rami and an acute insufficiency fracture of the
left sacrum. The left sacral ala shows buckling of its superior
cortex.
weighted sequences may mimic metastatic disease
(Fig. 8) and lead to unnecessary bone biopsies.3,8,34
Although MRI might provide an excellent account
of the fracture configuration, it is less specific and
ambiguous for the purpose of image interpretation.
The administration of calcium and vitamin-D
supplements has limited value and efficacy in the
advanced stages of osteoporosis. Bisphosphonates are
more beneficial in postmenopausal and corticosteroidinduced osteoporosis; evidence confirms an increase
in bone mineral density and a reduction in new
fractures after 2 years of bisphosphonate treatment.40,41
However, their value as long-term medication after
fractures remains controversial.
With the increase in the elderly population, sacral
insufficiency fractures may become epidemic in the
Vol. 15 No. 3, December 2007
(a)
Sacral insufficiency fractures 345
(b)
*
Figure 5 Anteroposterior radiographs of a 76-year-old
woman demonstrating (a) an undisplaced fracture through
the inferior sacro-iliac joint and the right iliac wing, which
was missed on initial assessment, (b) 3 months later, an
insufficiency fracture through the right hemi-pelvis with
gross displaced fracture is seen. The increased bone density
and sclerosis indicate that the fracture is longstanding and
not acute.
Figure 7 Delayed isotope bone scan of an 88-year-old
woman 3 hours post injection demonstrates the classic ‘Hshape’ pattern, with increased activity in both sacral alae
and within the sacral body and focal uptake around the left
symphysis pubis.
future. Primary and secondary osteoporoses are
common causes. Once a diagnosis is established the
treatment in most cases is simple, but recovery may
be protracted and full mobility curtailed.
ACKNOWLEDGEMENTS
The authors wish to thank Sylvia Louise Davies for
Figure 6 Anteroposterior radiograph of a 77-year-old
woman with bilateral vertical sacral fractures. Fractures
lines (arrows) and horizontal fracture component (asterisk)
are not clearly distinguishable.
Figure 8 T2-weighted magnetic resonance images of an
86-year-old woman with bilateral vertical sacral fractures
showing a sagittal section through the lumbo-sacral junction.
An area of inhomogeneous signal increase is present at the
S1/2 level (arrows), raising the suspicion of a neoplasm.
her help at various stages of the work. Appreciation
is expressed for support given by members of the
medical library at Southmead Hospital in Bristol,
the medical illustration departments at Frenchay
Hospital in Bristol, and Musgrove Park Hospital in
Taunton, as well as Ellen Beales of the Droitwich Knee
Foundation in Droitwich-Spa.
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