The added value of cross-sectional imaging in the detection of additional radiographically occult fractures in the setting of a Chopart fracture

Purpose

Radiography has a low sensitivity for the detection of fractures related to the talonavicular and calcaneocuboid articulations, also known as Chopart fractures. The purpose of this study is to determine the sensitivity of radiographs for detecting additional foot and ankle fractures related to Chopart fracture using CT or MRI as the reference standard.

Method

We performed an IRB-approved, retrospective review of radiology reports between 2010 and 2014. Inclusion criteria were (1) diagnosis of a Chopart fracture and (2) at least one radiograph and subsequent cross-sectional imaging (CT or MR). CT or MRI was considered the diagnostic reference standard. Results were stratified by the energy of trauma and by type of radiograph performed (weight-bearing (WB) versus non-WB).

Results

One hundred eight patients met the inclusion criteria. The calcaneocuboid articulation was the most commonly involved type of Chopart fracture, seen in 75% of cases (81/108). Chopart fractures were detected on the initial radiographs in 67.6% of cases (73/108). Additional fractures of the ankle and midfoot were diagnosed in 34.2% of cases (37/108), with 56.7% (21/37) of these cases having at least one additional fracture seen on CT or MRI that was not seen on the initial radiographs, with fractures of the midfoot most often missed. In 56.7% (17/30) patients whose radiographs detected Chopart fractures, at least one additional fracture was missed; 30% of them demonstrated intra-articular extension and 56.7% were considered displaced. High-energy trauma was related to higher incidence of additional fractures. There was no significant difference in the sensitivity of radiographs to detect additional fractures between high versus low-energy trauma (p?=?0.3) and WB versus non-WB radiographs (p?=?0.5). Most patients were treated nonoperatively (56.5%, 61/108), with surgical intervention more frequent in patients with a high energy of trauma (51.7% versus 33.3%, p?=?0.05).

Conclusion

In the setting of a Chopart fracture, CT or MRI can add significant value in the detection of additional ankle or midfoot fractures, irrespective of the energy of trauma. Since additional fractures can have important management implications, CT or MRI should be considered as part of the standard workup for all midfoot fractures.

     

Computed tomography for occult fractures of the proximal femur,pelvis, and sacrum in clinical practice: single institution,dual-site experience

Purpose

The purpose of this study was to evaluate the diagnostic performance of CT for assessment of occult fractures of the proximal femur, pelvis, and sacrum.

Materials and methods

A retrospective review was performed on patients who received a CT of the hip or pelvis for suspected occult fracture after negative or equivocal radiographs performed within 24 h. The official radiology report was utilized for the determination of CT findings and calculation of sensitivity and specificity. Surgical reports, MRI reports, and clinical follow-up were used as the standard of reference. Sensitivity and specificity were calculated with 95% confidence intervals.

Results

Seventy-four patients received CT of the hip or pelvis for clinical concern for occult fracture after negative or equivocal radiographs. By the reference standard, a total of 40 fractures were present in 25/74 (33.8%) patients, including 35 conservatively treated fractures of the greater trochanter, pelvis, and sacrum, and 5 operatively treated proximal femoral fractures. A total of 14/74 (18.9%) of patients had an MRI within 1 day of CT. MRI identified an operatively treated femoral neck fracture not seen on CT and an operatively treated intertrochanteric fracture, which CT described as a greater trochanteric fracture. There were two false negative conservatively treated pelvic fractures not seen on CT but diagnosed on MRI. On a per-patient basis, CT had an overall sensitivity of 88% (22/25; 95% confidence intervals 69–97%), specificity of 98% (48/49; 95% confidence intervals 89–100%), and negative predictive value of 94%. For the five operative proximal femoral fractures, the sensitivity of CT was 60% (3/5; 95% confidence intervals 15–95%), specificity was 99% (68/69; 95% confidence intervals 92–100%), and negative predictive value was 97%.

Conclusions

In the clinical setting of suspected occult fracture, the sensitivity of clinical CT reports for detection of any type of fracture of the proximal femur, pelvis, or sacrum was 88%. For the small number of operatively treated proximal femoral fractures seen in the study, sensitivity of CT was 60% (3/5) and negative predictive value was 97%, although the relatively few patients needing fixation precludes statistical analysis.

     

Computed tomography compared to magnetic resonance imaging in occult or suspect hip fractures. A retrospective study in 44 patients

Background

Computed tomography (CT) for evaluation of occult and suspect hip fractures has been proposed as a good second-line investigation. The diagnostic precision compared to magnetic resonance imaging (MRI) is unclear.

Purpose

To compare the diagnostic performance of CT and MRI in a retrospective study on patients with suspect and occult hip fractures.

Material and methods

Forty-four elderly consecutive patients with low-energy trauma to the hip were identified where negative or suspect CT was followed by MRI. Primary reporting and review by two observers as well as the diagnostic performance of the two modalities were compared. Surgical treatment and clinical course were used as outcomes.

Results

Compared to the primary reports, the CT reviewers found fewer normal and no suspect cases. MRI changed the primary diagnoses in 27 cases, and in 14 and 15 cases, respectively, at review. There was no disagreement on MRI diagnoses.

Conclusion

In our patient population, MRI was deemed a more reliable modality for hip fracture diagnosis in comparison to CT. For clinical decision making, MRI seems to have a higher accuracy than CT. A negative CT finding cannot completely rule out a hip fracture in patients where clinical findings of hip fracture persevere.

Key Points

? Experience is highly influential in diagnosing occult or suspect hip fractures at CT ? Inconclusive hip CT shows high inter-rater reliability at experienced review ? There was low diagnostic accuracy via CT compared to MRI for all interpreters ? Hip fractures can readily be diagnosed at MRI regardless of radiological experience

     

Subchondral impaction fractures of the non-weight-bearing portion of the lateral femoral condyle

Objective

To document the first report of intra-articular, non-weight-bearing, impaction fractures of the lateral femoral condyle.

Materials & methods

Institutional Review Board and Regional Ethics Committee approval for this study was obtained and patient informed consent deemed unnecessary. We prospectively documented all potential cases of non-weight-bearing posterior subchondral impaction fractures of the femoral condyles diagnosed on magnetic resonance imaging (MRI) of the knee performed at our institution between January 2006 and December 2011. The cases were reviewed and discussed by three experienced musculoskeletal radiologists and only cases satisfying pre-defined MRI criteria were included.

Results

Sixteen cases of intra-articular impaction fractures in a posterior, non-weight-bearing area of the lateral femoral condyle were diagnosed in patients with a mean age of 40. Eight were associated with recreational sports activities and 4 with repeated kneeling. There were no fractures documented in the non-weight-bearing aspect of the medial femoral condyles. Proposed underlying mechanisms for development of this type of fracture are presented.

Conclusion

Awareness, along with a high level of suspicion, that non-specific knee pain, especially in patients involved in athletic activities, could be due to intra-articular impaction fractures of the non-weight-bearing posterior aspect of the lateral femoral condyle is essential and MRI is the mainstay of diagnosis.     

Survey of the initial management and imaging protocols for occult scaphoid fractures in UK hospitals

Objective

The aim of this research was to survey how occult fractures of the scaphoid bone are both imaged and managed initially.

Materials and methods

A total of 832 questionnaires were sent via e-mail to active associate members of the British Orthopaedic Association. Included was a series of questions regarding the timing of initial and subsequent orthopaedic review of this group of patients and the use of serial radiographs and second-line imaging techniques.

Results

Nearly half of the UK’s acute NHS trusts were represented (45%). The response rate was 16% (130 out of 832). Only 16% of respondents were aware of a local imaging protocol for the investigation of suspected fractures of the scaphoid. Ninety-four percent of respondents performed a second radiograph at first fracture clinic review. Fifty-eight percent used magnetic resonance imaging (MRI) as a second-line investigation; with computed tomography scan and radionuclide isotope bone scan being performed by 26% and 16% respondents, respectively.

Conclusions

The survey revealed a wide variation in the management of occult fractures of the scaphoid. MRI has been shown to be both sensitive and specific in diagnosing occult carpal bone fractures. There is a need to standardise the management of these injuries to ensure early diagnosis and limit unnecessary wrist immobilisation.     

Who is more accurate in the diagnosis of neck of femur fractures, radiologists or orthopaedic trainees?

Objective

Our study aims to compare the sensitivity and specificity between orthopaedic trainees and radiologists in diagnosing occult hip fractures from pelvic radiographs.

Methods

All patients undergoing computed tomography (CT) of the hip for a suspected occult hip fracture at our two centres between November 1, 2010 and October 31, 2011 were retrospectively identified. Two orthopaedic trainees (RJ and ED) independently reviewed the initial radiographs, and if both agreed a fracture was present this was recorded. The reports from the radiologist of the initial radiograph and subsequent CT were recorded, with the CT report used as the standard of reference for comparison of performance.

Results

239 CTs were performed for suspected neck of femur fractures during the study period, compared to only 20 in 2006–07, reflecting a 1,095 % increase. The interpretation of radiographs by the orthopaedic trainees showed a sensitivity of 55.4 % and specificity of 96.6 %. In comparison, the radiologists had a sensitivity of 60.7 % and specificity of 92.9 %; this difference was shown not to be statistically significant. Radiologists and orthopaedic trainees agreed when interpreting the majority of radiographs with a Kappa co-efficient of 0.77 (a statistical measure of inter-rater agreement). In 20 of the 174 cases (11.5 %) where the radiologist and orthopaedic trainees agreed no fracture was present, the subsequent CT revealed a fracture.

Conclusion

Orthopaedic trainees and radiologists have similar accuracy at interpreting pelvic radiographs for suspected hip fractures, so the trainee’s opinion can be relied upon. If uncertainty exists, then either the orthopaedic trainee or radiologist should request further imaging urgently as we believe this will expedite diagnosis and treatment of hip fractures, and ensure judicious use of CT.     

The difficult diagnosis of cartilaginous tibial eminence fractures in young children

Purpose

Anterior tibial eminence fracture is the main mode of ACL failure in patients with open physes. In young children, purely cartilaginous avulsions of the tibial ACL insertion are possible. The aim of this study was to focus on patients referred for misdiagnosed cartilaginous tibial eminence fractures.

Methods

Ten young patients with cartilaginous tibial eminence fractures were identified in the hospital database. Six of them were misdiagnosed and included in this retrospective case series. Clinical data at the time of injury, radiographs and MRI were analysed in order to evaluate the causes which could have led to inappropriate management.

Results

The patients’ median age at the time of injury was 7 years (5–8.5). The main cause of injury was a low-energy domestic accident (n = 4). Radiographs at the time of injury were normal (n = 4) or showed a very thin ossification (n = 2). The traditional MRI findings of ACL injuries were all negative. On T2 sequences, an epiphyseal fluid signal allowed for a retrospective diagnosis. Cartilaginous tibial eminence fractures were regularly prolonged posteriorly giving a ‘double-PCL sign’ in 4 of the 6 patients. On a median of 6 months (2.5–48) after the injury, patients were referred for repeat giving ways (n = 5) and/or limitation of extension or hyperextension (n = 4). Symptoms were related to non-union, ossification and secondary enlargement of the avulsed fragment.

Conclusions

Post-traumatic knee joint effusions in children aged 9 or younger, even occurring after a low energy trauma and with normal radiographs, should suggest a cartilaginous tibial eminence fracture. Systematic MRI examinations should be mandatory in these patients in whom the avulsed fragment may appear as a double-PCL sign. During follow-up, new radiographs are recommended. A better knowledge of this rare entity should allow us to avoid misdiagnosis and to perform an early refixation of the avulsed fragment.

Level of evidence

III.     

Quantitative assessment of bone marrow attenuation values at MDCT: An objective tool for the detection of bone bruise related to occult sacral insufficiency fractures

Objectives

To prove the feasibility of using Hounsfield attenuation values at MDCT to detect bone bruises related to sacral insufficiency fractures.

Methods

Twenty-two patients with acute sacrum trauma and no fracture findings at MDCT were included in our prospective study. Two observers independently reviewed CTs regarding visual signs of bone bruises in 132 defined regions of the sacral alae. Interobserver agreement was tested by κ statistics. Subsequently, HU values were obtained in the same regions, and attenuation differences between the two sides were calculated. Validity and reliability were assessed by intraclass correlation coefficient and Bland-Altman analysis. HU differences were subjected to ROC curve analysis to determine sensitivity, specificity, PPV and NPV. MRI served as standard reference.

Results

MRI revealed 19 regions with bone bruises and associated sacral insufficiency fractures. HU measurements demonstrated good validity and reliability (r?=?0.989). ROC curve analysis exhibited an ideal cutoff value of 35.7 HU density difference between affected and non-affected regions. Visual evaluation revealed moderate agreement (κ?=?0.48); diagnostic accuracy was inferior to objective evaluation.

Conclusions

Assessment of differences in bone marrow density by HU measurements is an objective and reliable tool for detection of bone bruises associated with occult sacral insufficiency fractures.

Key Points

? Bone bruising is associated with occult sacral insufficiency fractures. ? Assessment of differences in bone marrow CT attenuation appears valid and reliable. ? Comparative HU measurements of bone marrow allow detection of bone bruises. ? Comparative HU measurements have high specificity and negative predictive values. ? Comparative HU measurements may make further diagnostic workup with MRI unnecessary.     

Explorative study of the sensitivity and specificity of the pronator quadratus fat pad sign as a predictor of subtle wrist fractures

Objective

To investigate the value of post-traumatic pronator quadratus (PQ) fat pad sign as a reliable predictor of subtle wrist fractures.

Materials and methods

This was a prospective study of 68 patients undergoing X-ray for traumatic wrist injuries and subsequent MRI. The reliability of a positive PQ fat pad sign on X-ray, defined as either raised, interrupted or obliterated, was evaluated in detection of subtle wrist fractures.

Results

Out of 68 patients, 28 had a positive PQ sign without any obvious bony injuries on plain radiographs; of these, the PQ fat pad was obliterated in 11, disrupted in 12, and raised in five cases. Fractures defined as cortical interruption or trabecular fractures were revealed in 13/28 (46 %) patients with a positive PQ sign but only in 7/40 (18 %) patients with a negative sign. With regards to different types of abnormal PQ fat planes, fractures were present in 7/12 patients with a disrupted plane (58 %), 6/11 patients with an obliterated plane (54 %), and none of the patients with a raised plane. The overall sensitivity and specificity of a positive PQ sign in the prediction of occult wrist fractures were 65 and 69 %, respectively.

Conclusions

Our findings indicate that a positive pronator quadratus (PQ) fat pad sign is not a reliable predictor of subtle fractures of the wrist, although we believe that it is a useful radiographic sign in justifying MRI for further clarification of possible joint abnormalities including occult fracture and cortex interruption.     

Prevalence of exclusively and concomitant pelvic fractures at magnetic resonance imaging of suspect and occult hip fractures

Pelvic fractures may occur together with hip fractures as a result of low energy trauma. It is unclear whether they do require special attention. There are conflicting results in the literature about the prevalence of both concomitant hip and pelvic fractures as well as exclusive pelvic fractures. It has been reported that hip fractures and obturator ring fractures are mutually exclusive. To retrospectively analyze the prevalence of exclusively pelvic as well as concomitant hip and pelvic fractures in patients examined with MRI after low-energy trauma in elderly. During 9 years, 316 elderly patients had been examined with MRI for suspected or occult hip fracture after a fall. A fracture was diagnosed when MRI showed focal signal abnormalities in the subcortical bone marrow, with or without disruption of adjacent cortices. One observer reviewed all studies. A second observer verified all studies with hip fractures. Follow-up was available for all but two patients that died prior to hip surgery. The prevalence of concomitant pelvic and femoral neck or trochanteric fractures was statistically compared using chi-squared test for categorical variables. Hip fractures were found in 161 (51 %) patients of which 29 (9 %) had concomitant pelvic fractures. There were exclusively pelvic fractures in 82 (26 %) patients of which 65 (79 %) were on the traumatized side only. In 73 patients, there were no fractures. Occult or suspected hip fractures are not infrequently associated with pelvic fractures. Exclusively pelvic fractures are not uncommon.     

MRI as a reference standard for suspected scaphoid fractures

Objectives

Some have suggested that MRI might be the best reference standard for a true fracture among patients with suspected scaphoid fractures. The primary aim of this study was to determine the rate of false-positive diagnosis of an acute scaphoid fracture in a cohort of healthy volunteers.

Methods

In a prospective study, 33 healthy volunteers were recruited and both wrists of each were scanned, except for 2 volunteers for whom only one wrist was scanned. To simulate the usual clinical context the 64 scans of healthy volunteers were mixed with 60 MRI scans of clinically suspected scaphoid fractures but normal scaphoid radiographs. These 124 MRI scans were blinded and randomly ordered. Five radiologists evaluated the MRI scans independently for the presence or absence of a scaphoid fracture and other injuries according to a standard protocol.

Results

To answer the primary question, only the diagnoses from the 64 scans of healthy volunteers were used. The radiologists diagnosed a total of 13 scaphoid fractures; therefore, specificity for diagnosis of scaphoid fracture was 96% (95% confidence interval: range 94–98%). The 5 observers had a moderate interobserver agreement regarding diagnosis of scaphoid fracture in healthy volunteers (multirater κ=0.44; p<0.001).

Conclusions

The specificity of MRI for scaphoid fractures is high (96%), but false-positives do occur. Radiologists have only moderate agreement when interpreting MRI scans from healthy volunteers. MRI is not an adequate reference standard for true fractures among patients with suspected scaphoid fractures.The American College of Radiologists recommends MRI for diagnosis of true fractures among suspected scaphoid fractures [1]. A number of published studies cite sensitivities and specificities approaching 99% [2-9], but other studies have reported a lower sensitivity (80%) and substantial interobserver variation (κ=0.67) for diagnosis of a scaphoid fracture [2,8]. It has been difficult to agree upon a reliable reference standard for true fractures among suspected scaphoid fractures, and these studies often use only repeated radiographs 6 weeks after trauma as reference standard. However, it is also known that not all occult scaphoid fractures become apparent on repeated radiographs.It is not clear how to distinguish true fracture from other changes in bone signal that are detected with MRI. We propose that MRI of the wrists of healthy volunteers with no history of wrist or hand injury represents a reliable reference standard for the absence of an acute fracture of the scaphoid waist. By evaluating MRI scans of healthy volunteers, we may learn more about the diagnostic performance characteristics of MRI for suspected scaphoid fracture. A set of MRI scans with a reliable reference standard would also provide useful information about the reproducibility of the interpretation of MRI for suspected scaphoid fracture.The primary study question was to investigate the occurrence of false-positive diagnosis of an acute scaphoid fracture on MRI using a reliable reference standard (healthy volunteers). Secondarily we also investigated the interobserver variation of diagnosis of scaphoid fracture on MRI in healthy volunteers.     

MDCT findings after elbow dislocation: a retrospective study of 140 patients

Objective

To assess the number and anatomical location of fractures associated with elbow dislocation, to study the correlation between the direction of dislocation and the trauma energy, and to assess radiographs’ diagnostic performance characteristics for fractures using MDCT as a reference standard.

Materials and Methods

A retrospective study was performed at a level 1 trauma center, finding a total of 140 patients who had sustained an elbow dislocation and who had undergone a subsequent MDCT examination. The CT and radiographs of the patient were reviewed by two musculoskeletal radiologists. CT images were analyzed for the site and size of the fracture fragments. In addition, the primary direction of the dislocation, patients’ age, and gender were recorded. Trauma energy was also assessed.

Results

One hundred and thirty-four out of 140 patients (96 %) had a fracture that was seen on the correlative CT examination. The most common anatomical fracture locations were the coronoid process of the ulna 84 out of 140 (60 %), the radial head 75 out of 140 (54 %), and the humeral capitellum 57 out of 140 (41 %). Multiple fractures were seen in 71 out of 134 (53 %) patients with fractures. The left elbow was more commonly dislocated than the right one. The overall sensitivity of the radiographs was 62 % and the specificity 96 %.

Conclusion

Small fractures and impaction fractures are almost invariably present in elbow dislocations, and half of the patients have more than one fracture. Radiographs have a sensitivity of only 62 %. MDCT is an invaluable method for determining the extent of bony injury and revealing occult fractures.     

Correlation between radiological assessment of acute ankle fractures and syndesmotic injury on MRI

Objective

Owing to the shortcomings of clinical examination and radiographs, injury to the syndesmotic ligaments is often misdiagnosed. When there is no indication requiring that the fractured ankle be operated on, the syndesmosis is not tested intra-operatively, and rupture of this ligamentous complex may be missed. Subsequently the patient is not treated properly leading to chronic complaints such as instability, pain, and swelling. We evaluated three fracture classification methods and radiographic measurements with respect to syndesmotic injury.

Materials and methods

Prospectively the radiographs of 51 consecutive ankle fractures were classified according to Weber, AO-Müller, and Lauge-Hansen. Both the fracture type and additional measurements of the tibiofibular clear space (TFCS), tibiofibular overlap (TFO), medial clear space (MCS), and superior clear space (SCS) were used to assess syndesmotic injury. MRI, as standard of reference, was performed to evaluate the integrity of the distal tibiofibular syndesmosis. The sensitivity and specificity for detection of syndesmotic injury with radiography were compared to MRI.

Results

The Weber and AO-Müller fracture classification system, in combination with additional measurements, detected syndesmotic injury with a sensitivity of 47% and a specificity of 100%, and Lauge-Hansen with both a sensitivity and a specificity of 92%. TFCS and TFO did not correlate with syndesmotic injury, and a widened MCS did not correlate with deltoid ligament injury.

Conclusion

Syndesmotic injury as predicted by the Lauge-Hansen fracture classification correlated well with MRI findings. With MRI the extent of syndesmotic injury and therefore fracture stage can be assessed more accurately compared to radiographs.     

Comparison of diagnostic accuracy of Magnetic Resonance Imaging and Multidetector Computed Tomography in the detection of pelvic fractures

Objective

To compare diagnostic accuracy and interobserver reliability of Magnetic Resonance Imaging (MRI) and Multidetector Computed Tomography (MDCT) in the detection of acute pelvic fractures.

Materials and methods

In 38 consecutive patients (mean age 74.7 years) with a positive finding of anterior pelvis fracture in the conventional X-rays, pelvic MRI and MDCT were performed for further evaluation of pelvic ring fractures. Two radiologists independently read all data sets. Sensitivity and specificity were calculated based on mean scores for each method. Sensitivities of CT and MRI were compared using a paired proportion test (McNemar). Diagnostic validity of both methods was assessed by the interobserver variability using kappa statistics. Combined clinical data and findings from all imaging studies served as the reference standard.

Results

122 fractures were identified in the reference standard (37 sacral, 58 pubic, 22 acetabular, 1 ischial, 4 ilial). On average, MRI detected 96.3% whereas CT detected 77% of all fractures. With regard to sensitivity, MRI proved to be significantly better compared to MDCT (observer 1, p = 0.0009; observer 2, p = 0.0003 by observer 2). In particular, MRI performed better in the depiction of sacral fractures, reaching a sensitivity of 98.6% compared to 66.1% at CT. The interobserver variability was determined to be very good (k = 0.955 for MRI and 0.902 for MDCT).

Conclusion

MRI reaches a significantly higher sensitivity than CT in the detection of acute pelvic fractures, particularly of the sacrum. Especially in elderly patients with suspicion of a sacral fracture and negative results at MDCT, MRI may be considered as the next step in diagnostic workup.     

CT characteristics of traumatic sacral fractures in association with pelvic ring injuries: correlation using the Young-Burgess classification system

Purpose

The purpose of the study is to determine the incidence of sacral fracture patterns on CT imaging of pelvic trauma patients with correlation with mechanism of injury and pelvic ring injury pattern using the Young-Burgess classification system.

Materials and methods

This is a retrospective review of all pelvic CTs with pelvic fractures performed at our level 1 trauma center during a 4-year period from July 2010 to June 2014.

Results

Sacral fractures were very common in pelvic trauma patients, being present in 60% of patients presenting to our institution with pelvic fractures. Longitudinal fractures were almost always associated with additional pelvic ring injuries. Denis zone 1 fractures had the highest association with lateral compression pelvic ring injuries. Denis zone 2 and 3 fractures were seen with increased frequency in AP compression and vertical shear injuries. A third of transverse sacral fractures occurred in isolation, with isolated transverse sacral fractures typically occurring in the low (S3–S5) sacrum. Almost half of combined transverse and longitudinal sacral fractures occurred without an additional pelvic fracture present. Sacral avulsions almost always occurred as part of a pelvic ring fracture pattern, most commonly in AP compression injuries. Coccyx fractures frequently occurred in isolation, but were commonly seen in vertical shear injuries when associated with a pelvic ring injury pattern.

Conclusion

Avulsion fractures and longitudinal fractures of the sacrum are almost always associated with anterior pelvic ring injury. Conversely, transverse fractures of the lower sacrum and combined longitudinal and transverse sacral fractures are prone to occur in isolation.

     

Visual expertise in detecting and diagnosing skeletal fractures

Objective

Failure to identify fractures is the most common error in accident and emergency departments. Therefore, the current research aimed to understand more about the processes underlying perceptual expertise when interpreting skeletal radiographs.

Materials and methods

Thirty participants, consisting of ten novices, ten intermediates, and ten experts were presented with ten clinical cases of normal and abnormal skeletal radiographs of varying difficulty (obvious or subtle) while wearing eye tracking equipment.

Results

Experts were significantly more accurate, more confident, and faster in their diagnoses than intermediates or novices and this performance advantage was more pronounced for the subtle cases. Experts were also faster to fixate the site of the fracture and spent more relative time fixating the fracture than intermediates or novices and this was again most pronounced for subtle cases. Finally, a multiple linear regression analysis found that time to fixate the fracture was inversely related to diagnostic accuracy and explained 34 % of the variance in this variable.

Conclusions

The results suggest that the performance advantage of expert radiologists is underpinned by superior pattern recognition skills, as evidenced by a quicker time to first fixate the pathology, and less time spent searching the image.     

Association of femoral head and acetabular fractures on computerized tomography: correlation with the Judet-Letournel classification

Purpose

Tha aims of this study were to identify the incidence of femoral head fractures in the setting of acetabular fractures and to determine the relationship between acetabular fracture pattern, the degree of acetabular fracture displacement, and the incidence of femoral head fractures.

Materials and methods

This is a retrospective cross-sectional study of 274 patients with 300 acetabular fractures diagnosed on pelvic CT. Acetabular fractures were categorized using the Judet-Letournel classification system.

Results

Femoral head fractures were present in 18.0% of acetabular fractures. Fracture patterns with a posterior wall component had a very high (56.3%) incidence of femoral head fracture. Anterior column and anterior column with posterior hemitransverse fractures have a very low (3.4%) incidence of femoral head fracture. Anterior hip dislocation had a 66.7% incidence of femoral head fracture, while posterior dislocation had a 71.9% incidence. Acetabular fractures displaced by more than 5 mm had a 26.9% incidence of femoral head fracture, while acetabular fracture displaced less than 5 mm had only 4.2% incidence of femoral head fracture.

Conclusion

Femoral head fractures are a very common associated finding in patients presenting with acetabular fractures. In patients with a posterior wall component of the fracture or associated hip dislocation, a femoral head fracture is more likely than not present. Conversely, in acetabular fractures with less than 5 mm displacement or anterior column fractures without posterior acetabular involvement, femoral head fractures are very unlikely in the absence of a dislocation event.

     

Prediction of hip osteoporotic fractures from composite indices of femoral neck strength

Objective

To clarify whether composite hip strength indices improve predictive ability for hip osteoporotic fractures independent of conventional bone mineral density (BMD).

Subjects and methods

Three hundred and eighty-two health controls and 43 women with hip fractures (aged 28.2–87.7 years, mean age 59.5±9.2 years) were measured by dual energy X-ray absorptiometry for femoral neck bone mineral density (FN_BMD) and proximal femur geometry parameters of hip, and composite hip strength indices (Compression strength index, Bending strength index, and Impact strength index). The association between the studied parameters and the fractures was modelled using multiple logistic regression, including age, height, weight, and menopausal status. Fracture-predicted probability was calculated for each predictor tested. ROC curve areas (AUCs) were calculated for the fracture status, having the calculated fracture-predicted probability as a test variable. AUCs were compared by the Hanley–McNeil test.

Results

Women with hip fractures had lower FN_BMD, composite hip strength indices, and longer hip axis length than controls, and no significant difference in femoral neck width. Logistic regression showed composite hip strength indices could predict hip fractures risk. To the same extent as FN BMD, Compression Strength Index (CSI) best predicted the risk for each fracture (AUC?=?0.787?±?0.028). When CSI was added to FN_BMD, there was a small but not statistically significant increase in AUC to 0.796?±?0.027 (P?=?0.9018).

Conclusion

Composite indices of femoral neck strength may be valuable in the assessment of the biomechanics of bone fragility; however, they do not appear to add diagnostic value to the simple measurement of BMD.     

Magnetic resonance imaging of occult fractures of the proximal femur

The evaluation of the painful hip in the elderly osteoporotic patient with normal plain radiographs can be difficult. We studied 15 osteopenic patients with normal plain radiographs and suspected hip fractures with magnetic resonance (MR) imaging and found MR to be an excellent aid in detecting occult fractures. A clear fracture was seen in 10 of the 15 patients, who then underwent surgical repair based on the MR study. The remaining patients had no MR-demonstrable fracture and were successfully treated nonoperatively. Some believe that a negative bone scan in this population of patients should be repeated within 3 days prior to a definitive no fracture decision being made. Unfortunately, bone scanning lacks spatial resolution, and increased osteoblastic activity may be caused by other pathologic processes besides fracture. Two of the 15 patients had MR-demonstrated bone infarcts near the fracture. One patient also had femoral head osteonecrosis on the side of the fracture. One patient with metastatic prostatic carcinoma had a hip fracture and one patient with metastatic breast carcinoma had no fracture. Not only is MR imaging an excellent technique for delineating occult fractures, but due to its spatial resolution, associated bone disorders adjacent to fractures can be detected in most instances. From a cost perspective, rapid diagnosis and early treatment of an occult femoral fracture is advisable. A reduced hospital stay pending diagnosis and the early institution of definitive therapy also decrease the chance that a simple non-displaced fracture will displace and require more complex management with resultant increased morbidity and cost. We propose that, especially in elderly, osteopenic patients with normal plain radiographs and a high index of suspicion for hip fracture, MR can serve as the sole additional imaging study in most instances.Presented at the Annual Meeting of the American Roentgen Ray Society, San Francisco, April 1993     

Bone marrow oedema on MR imaging indicates ARCO stage 3 disease in patients with AVN of the femoral head

Objectives

To test the hypothesis that bone marrow oedema (BME) observed on MRI in patients with avascular necrosis (AVN) of the femoral head represents an indicator of subchondral fracture.

Methods

Thirty-seven symptomatic hips of 27 consecutive patients (53 % women, mean age 49.2) with AVN of the femoral head and associated BME on magnetic resonance (MR) imaging were included. MR findings were correlated with computed tomography (CT) of the hip and confirmed by histopathological examination of the resected femoral head. Imaging studies were analysed by two radiologists with use of the ARCO classification.

Results

On MR imaging a fracture line could be identified in 19/37 (51 %) cases, which were classified as ARCO stage 3 (n?=?15) and stage 4 (n?=?4). The remaining 18/37 (49 %) cases were classified as ARCO stage 2. However, in all 37/37 (100 %) cases a subchondral fracture was identified on CT, indicating ARCO stage 3/4 disease. The extent of subchondral fractures and the femoral head collapse was graded higher on CT as compared to MRI (P?Histopathological analysis confirmed bone necrosis and subchondral fractures.

Conclusions

In patients with AVN, BME of the femoral head represents a secondary sign of subchondral fracture and thus indicates ARCO stage 3 disease.

Key Points

? BME on MRI in AVN of femoral head indicates a subchondral fracture. ? BME in AVN of the femoral head represents ARCO stage 3/4 disease. ? CT identifies subchondral fractures and femoral head collapse better than MR imaging. ? This knowledge helps to avoid understaging and to trigger adequate treatment.