Key words
ribs - thorax - conventional radiography - CT - trauma
Introduction
Conventional rib series (RS) are a very common routinely performed radiological examination.
It entails applying a dedicated radiographic technique to visualize and assess the
bony parts of the chest wall by one or more oblique views, with or without marking
the points of maximum tenderness. In comparison to routine chest radiographs (CRs),
RS is carried out using lower X-ray energy and a smaller field of view to optimize
the contrast of the ribs. Both diagnostic modalities are common, RS alone or in combination
with CR. Severe thoracic trauma is regularly assessed by multidetector computed tomography
(MDCT). However, minor blunt traumas are often examined by rib series [1]
[2]
[3]
[4]. The diagnostic yield of RS in evaluating thoracic injury is considered to be low
compared with MDCT [5]
[6]
[7]. Because of the lower X-ray energy, RS exposes the patient to a higher radiation
dose than CR. The clinical value of RS is not clear. Minor thoracic trauma often results
in nothing more than isolated rib fractures without any dislocation. In these cases
RS might provide insufficient diagnostic accuracy, as non-dislocated rib fractures
cannot always be detected. On the other hand, non-dislocated rib fractures are generally
treated conservatively and very seldom have significant clinical sequelae.
The purpose of this study was to reveal the clinical significance of rib series in
patients with minor thoracic trauma in a tertiary care university medical center.
Materials and Methods
Patient data
Based on a retrospective chart review we analyzed all patients who underwent a conventional
radiographic examination by rib series in our tertiary care university medical center
in a two-year period between 2008 and 2010. Out of a total of 767 examinations, we
identified 669 patients fulfilling the following criteria: the indication for examination
must be minor blunt thoracic trauma, and the clinical follow-up must be documented
in the patient’s chart.
Based on the original radiological reports, the findings were classified according
to the presence or absence of rib fractures. The number and location of the involved
ribs were documented. Additionally associated complications such as hemo- and pneumothorax
were evaluated. The CRs of 405 of the 669 abovementioned patients were further assessed
by two experienced board certified consultants to compare the diagnostic accuracy
of both techniques.
For further analysis of the clinical follow-up of the patients, all available medical
reports were assessed. Patients were followed up after undergoing rib series examinations
and classified into the following four categories: (1) no special treatment, (2) pain
therapy/requiring analgesia, (3) pain therapy and follow-up imaging and (4) requiring
hospital admission and/or immediately further diagnostic workup.
Radiographic techniques
All patients were examined on a digital radiological workstation (Axiom Aristos Multix
FDX, Software VB21B, Siemens Healthcare®, Erlangen, Germany) with 70 kV X-ray energy. Two oblique rib series were performed
as grid radiography (Pb15/80) for all patients with a focus distance of 150 cm. The
patients were examined in a standing position. Image interpretation was performed
as soft reading on a digital diagnostic workstation (Syngo Imaging Advanced, Software
Version VB36A, Siemens Healthcare®, Erlangen, Germany) using two high-performance LCD monitors (Radioforce GS 220, Eizo®, Mönchengladbach, Germany). Chest radiograph examinations were also performed as
grid radiography (Pb15/80) in a standing position on the same digital workstation
using 120 kV X-ray energy.
Statistics
WinSTAT® for Microsoft® Excel (R. Fitch Software®, Bad Krotzingen, Germany) was used for all statistic calculations. The findings of
the rib series and chest radiographs were analyzed using the McNemar test. The statistical
significance between the results of the radiographic examinations and the clinical
follow-up was analyzed by the Chi-Square test and the Kruskal-Wallis test. P-values
of < 0.05 were considered statistically significant.
Ethics
In accordance with the local ethics committee and due to the retrospective nature
of this study, institutional review board approval was not necessary.
Results
669 patients were included (61.4 % men, 38.6 % women). The mean age was 51 years (range
13 – 92 years). Considering the initial examination reports of 669 rib series performed
by residents (radiology work experience ranging between 1 and 3 years) under the supervision
of a board certified consultant, 157 (23.5 %) patients were diagnosed with at least
one fractured rib, while no rib fracture was found in 512 (76.5 %) patients. Of the
157 patients with proven fractures, 73 (46.8 %) had a single rib fracture, 38 (24.4 %)
had two broken ribs and 45 (28.8 %) had more than two broken ribs ([Table 1]). Pneumothorax and hemothorax were diagnosed in 7 and 5 cases respectively of the
patients with rib fractures ([Fig. 1]). These 12 patients received both CR and RS. In 6 patients the complications were
missed on the RS.
Table 1
Findings of rib series of 669 patients.
Tab. 1 Befunde der Hemithoraxaufnahmen von 699 Patienten.
|
no. of fractured ribs
|
no. of patients diagnosed by rib series
|
|
0
|
512 (76.5 %)
|
|
1
|
73
|
total 157
(23.5 %)
|
|
2
|
38
|
|
> = 3
|
45
|
Fig. 1 64-year-old patient with fracture of the ribs VI-IX (☆), apical pneumothorax (→)
and soft tissue emphysema (→).
Abb. 1 64-jähriger Patient mit Frakturen der Rippen VU-IX (☆), apikalem Pneumothorax (→)
und Weichteilemphysem (→).
405 patients received additional CR, and 69 (17.0 %) of these cases were diagnosed
with rib fractures. Comparing the corresponding rib series of these patients, 87 (21.5 %)
patients with fractures could be identified ([Fig. 2], [3]). None of the positive findings of a fracture in CR were negative in the RS. These
differences in the findings of CR and RS were significant ([Table 2]). This was further confirmed by the second reading that was carried out by the two
experienced consultants. In addition to the findings above, a total of 18 rib fractures,
8 in the CR group and 10 in the RS group, were newly diagnosed. In 112 (16.7 %) patients
the findings of the RS and CR were only documented in the radiology report but not
in the patient’s chart.
Fig. 2 46-year-old patient with minor blunt trauma to the thorax with an unremarkable chest
radiograph.
Abb. 2 46-jähriger Patient mit Bagatelltrauma des Thorax und unauffälliger Thoraxübersichtsaufnahme.
Fig. 3 Same patient as in [Fig. 2]. Rib series shows fractures of rib IV and V on the right side (→).
Abb. 3 Gleicher Patient wie in [Abb. 2]. Die Hemithoraxraufnahme zeigt Frakturen der Rippen IV und V auf der rechten Seite
(→).
Table 2
Findings of chest radiographs and rib series of 405 patients.
Tab. 2 Befunde der Thorax-und Hemithoraxaufnahmen von 405 Patienten.
|
p = 0.001
McNemar
|
rib series
|
|
|
fracture
|
no fracture
|
total
|
|
Chest radiograph
|
fracture
|
69
|
0
|
69
|
|
no fracture
|
18
|
318
|
336
|
|
total
|
87
|
318
|
405
|
Of all 669 patients, 429 patients received therapy. For the others no therapeutic
procedures were documented in the charts. Of the 157 patients with proven rib fractures,
63.1 % received therapy, and of those without a documented fracture 64.5 % received
therapy ([Table 3]).
Table 3
Therapeutic sequelae of rib series of 669 patients.
Tab. 3 Therapeutische Relevanz der Befunde der Hemithoraxaufnahmen von 669 Patienten.
|
p = 0.25
Chi-Square
|
therapeutic relevance
|
total
|
|
no treatment
|
treatment
|
|
rib series
|
no fracture
|
182 (35.5 %)
|
330 (64.5 %)
|
512
|
|
fracture
|
58 (36.9 %)
|
99 (63.1 %)
|
157
|
|
total
|
240 (35.9 %)
|
429 (64.1 %)
|
669
|
Regarding the clinical significance of the radiographic examinations, there was no
significant relationship with the finding of RS and the documented decision for or
against treatment of the patient.
With 92 % symptomatic pain therapy was the most common documented treatment. Follow-up
by imaging or additional examinations was performed in 3.7 % of the cases. Immediate
further diagnostic workup or hospital admission was recommended for 4.3 % of the treated
patients ([Table 4]). There was a strong correlation between the positive finding of a fracture and
the need for higher medical care. No relevant age-related differences were noted ([Table 5]). None of the evaluated patients required any kind of thoracic surgical intervention
for their injuries.
Table 4
Different medical interventions for radiographic findings in 429 patients.
Tab. 4 Therapeutische Konsequenzen in Abhängigkeit der radiologischen Befunde von 429 Patienten.
|
p < 0.001 Kruskal-Wallis
|
no fracture
|
fracture
|
total
|
|
level of therapy
|
pain therapy
|
329
|
66
|
395
|
|
pain therapy
diagnostic follow-up
|
1
|
15
|
16
|
|
pain therapy, immediate further diagnostic workup and/or stat. admission
|
0
|
18
|
18
|
|
total
|
330
|
99
|
429
|
Table 5
Confirmed fracture and specific treatment depending on the patient’s age
Tab. 5 Frakturnachweis und spezifische Therapie in Abhängigkeit vom Patientenalter
|
age
|
no. of patients
|
fracture
|
treatment
|
|
45 <
|
255
|
60 (23.5 %)
|
160 (62.7 %)
|
|
45 – 65
|
237
|
58 (24.4 %)
|
149 (62.8 %)
|
|
< 65
|
177
|
39 (22.0 %)
|
120 (67.7 %)
|
Discussion
Thoracic injury is the third most common type of trauma, following injuries of the
head and the extremities [6]. Contrast-enhanced MDCT of the chest is considered to be the diagnostic method of
choice for severe thoracic trauma. All relevant traumatic diagnoses can be made in
a short time with high accuracy providing high sensitivity and specificity in the
detection of pulmonary laceration, tracheobronchial injury, pneumothorax and aortic
lesions [8].
Rib fractures represent the most common thoracic injury, and can be found in up to
67 % of cases with blunt thorax trauma [9]. However, rib fractures may also occur without adequate trauma. Typical risk groups
are elderly patients suffering from osteoporosis or those engaging in competitive
sports [10]
[11].
Fractures are the most common form of injury of the ribs. MDCT offers high diagnostic
accuracy in evaluating the bony parts of the thorax [12]. Although the lower diagnostic sensitivity of radiography compared to MDCT is a
known fact, radiography is known as the first line investigation in evaluating minor
thorax traumas [1]. CR can depict bony injuries as well as typical complications of rib fractures such
as pneumothorax and hemothorax. Former studies revealed a sensitivity for the detection
of rib fractures by chest films of only 15 – 50 % [13]
[14]
[15]. MDCT seems to be superior in evaluating chest wall injuries [16]
[17].
The low sensitivity of chest radiography may be improved by using rib series with
optimized bony contrast. De Lucca et al. examined 100 patients after thorax trauma
with both techniques. Chest film revealed 13 patients with rib fracture while rib
series detected 28 [13]
. Our results also show that RS reveals more fractures than CR. To the best of our knowledge,
there are no studies which evaluate the diagnostic accuracy of dedicated rib series
in comparison with MDCT.
The clinical significance of the radiographic proof of a rib fracture in the case
of minor thorax trauma is a common point of discussion between radiologists and referring
physicians. Isolated fractures of the ribs without associated complications, even
with an obvious dislocation of the fracture are treated symptomatically [18]. Our results show that the decision whether to treat or not seems to be independent
from the results of the RS. This hypothesis could be supported by the fact that 16.7 %
of the results of the radiographic examination were not documented in the patient’s
chart. On the other hand, patients diagnosed with a rib fracture, who received further
therapy, received more medical care, most probably due to the higher pain scores along
with the associated complications such as developing a pneumothorax and/or a hemothorax.
The results of our study were comparable/similar to those obtained by a study of Davis
et al. However, the number of patients examined was much smaller and no RS examinations
were carried out [19].
Based on our investigation, the extra diagnostic yield provided by RS in comparison
to CR was not found to be of additional clinical relevance. In some cases the exclusion
of a fracture might be a matter of urgent necessity, for example for forensic reports
or in cases of suspected child abuse [20]. For these special situations, where the detection of bony lesions plays an important
role, one has to consider alternative imaging modalities. For example, MDCT provides
higher diagnostic accuracy for bony injury and associated complications, even cartilage
damage can be visualized [12]. An argument for using RS instead of MDCT might be the radiation dose. RS delivers
about 1 – 1.5 mSv of radiation dose, while modern low-dose MDCT protocols should reach
comparable values [21]. At this point it is important to mention ultrasonography, which is a very helpful
diagnostic tool for the detection of rib fractures. Due to its high spatial resolution,
it may even be superior to MDCT. Griffith et al. revealed in their study of 50 patients
a sensitivity of 90 % for the detection of rib fractures, while radiography showed
only a sensitivity of 15 %. The specificity of both modalities was 100 % [14]. On the other hand, ultrasonography has known limitations such as high examiner
and patient dependence, and missing standards to perform and document the examinations.
MRI may also represent a helpful tool in evaluating traumatic bony injuries of the
chest wall, but no data has been published so far, and the lower spatial resolution
might be a problem. The restricted availability is probably the most limiting factor
for its use in the diagnostic workup of emergency patients.
MDCT is the method of choice for detecting rib fractures because it simultaneously
provides a higher diagnostic yield while delivering an acceptable radiation dose [17]. However, if in cases of minor thorax trauma a rib fracture has no impact on the
therapeutic procedure, a CR to rule out complications might be enough especially because
of the lower radiation dose.
Although our study includes a high number of patients, we are of course aware of its
limitations. Due to the retrospective character, there is no defined standard for
documenting the follow-up of the patients. The grade of information given in the medical
reports shows a wide variety and a lot of the reports were not very detailed. Therefore,
it was only possible to classify three categories of therapy. Probably some therapeutic
procedures and further diagnostic workup were not documented in the charts. For example
respiratory care exercises/physiotherapy to avoid pneumonias are a common supportive
therapy [18], but on the other hand the risk of developing these complication seems to be low
[22]. 70 of the 157 patients with proven fractures in the RS did not receive an additional
CR. The reasons for this were not clear. Another bias might be the fact that in many
of the patients, who received RS and CR, both examinations were performed as one complete
procedure. This may have caused reduced attention to bony lesions in the interpretation
of the CR with consecutive significantly higher sensitivity for the detection of rib
fractures in the RS.
Conclusion
Our results suggest that RS for detecting rib fractures in patients with minor thoracic
trauma is of limited clinical value. Despite being superior to CR in diagnosing rib
fractures, the results from RS seem to have no significant influence on further clinical
management and therapeutic measures. Blunt minor thorax trauma should be evaluated
by CR to rule out dislocated fractures and associated complications such as hemothorax
and pneumothorax. If there is high clinical suspicion of rib fractures in the presence
of normal CR findings, alternative imaging modalities should be performed.
