Scaphoid fracture and nonunion: current status of radiological diagnostics

Scaphoid fractures, which involve approximately two-thirds of all wrist injuries, are often not detected during initial radiographic examination. By using high-resolution CT and dedicated MRI, it is possible to recognize scaphoid fractures soon at the first diagnostic approach and to assess fragment stability. CT imaging provides all the relevant information of the fracture extent and of the fracture healing in the follow-up. MRI is most sensitive in the detection of scaphoid fractures; however, fracture signs must be differentiated from those of a bone bruise. Both the initially overseen scaphoid fracture and the unsuccessful healing can lead to the natural history of scaphoid nonunion. In the injured scaphoid, CT imaging is essential for depicting the osseous morphology, whereas contrast-enhanced MRI is crucial for assessing the viability of the proximal fragment.     

Case report: False negative 16 detector multislice CT for scaphoid fracture

We discuss a case of a 19-year-old man with scaphoid trauma. We describe the imaging findings on three sets of radiographs, bone scintigraphy, CT and MRI. CT failed to identify a scaphoid fracture, which was present on 6 week radiographs, MRI and scintigraphy. The case illustrates that despite multidetector technology, CT still relies upon cortical and or trabecular displacement to demonstrate fractures.     

Occult scaphoid fractures: comparison of multidetector CT and MR imaging--initial experience

PURPOSE: To compare the diagnostic performance of multidetector computed tomography (CT) and magnetic resonance (MR) imaging in patients clinically suspected of having a scaphoid fracture and who had normal initial radiographs, with radiographs obtained 6 weeks after trauma as the reference standard. MATERIALS AND METHODS: The ethics committee approved the study, and all patients gave written informed consent. Twenty-nine patients (17 male, 12 female; age range, 17-62 years; mean age, 34 years +/- 13) underwent multidetector CT and MR imaging within 6 days after trauma. CT data were obtained with 0.5-mm collimation. For image review, 0.7-mm-thick multiplanar reformations were performed in transverse, coronal, and sagittal planes relative to the wrist. The 1.0-T MR examination consisted of coronal and transverse short inversion time inversion-recovery, coronal and transverse T1-weighted spin-echo, and coronal volume-rendered T2-weighted gradient-echo sequences. Two radiologists analyzed the CT and MR images. A binomial test was used to evaluate the significance of the differences between MR imaging and CT in detection of scaphoid fractures and cortical involvement (P < .05). RESULTS: The 6-week follow-up radiographs depicted a scaphoid fracture in 11 (38%) patients. Eight patients had a cortical fracture, while three patients had only a bandlike lucency within the trabecular portion of the scaphoid. MR imaging depicted all 11 fractures but only three [corrected] cortical fractures. Multidetector CT depicted all eight cortical fractures but failed to depict trabecular fractures. No false-positive fractures were seen on MR or CT images. Differences between MR imaging and CT were not significant for the detection of scaphoid fractures (P = .25) but were significant for cortical involvement (P = .03). CONCLUSION: Multidetector CT is highly accurate in depicting occult cortical scaphoid fractures but appears inferior to MR imaging in depicting solely trabecular injury. MR imaging is inferior to multidetector CT in depicting cortical involvement.     

Forty degree angled coronal CT scanning of scaphoid fractures through plaster and fiberglass casts

A method for obtaining coronal CT scans angled 40 degrees to the longitudinal axis of the wrist, parallel to the long axis of the scaphoid, is described. Its potential for evaluating scaphoid fractures is assessed in 10 patients with healing or clinically suspected fractures. Overlapping 3 mm thick angled coronal CT scans were obtained for each patient both in and out of cast. The CT images were compared to plain films and tomography. Comparisons were also made of CT images obtained through fiberglass and plaster casts. All fractures apparent by plain films and tomography were apparent by CT; one case suspected of fracture on initial plain films showed no evidence of fracture on CT and subsequent clinical course and plain films. Osseous union of healing fractures was more reliably assessed on CT than on plain films and plain film tomography. There was no degradation of CT images by either fiberglass or plaster casts; fiberglass casts allowed easy planning of tomographic slices from scout films. We conclude that direct 40 degree angled coronal CT examination of the scaphoid is a quick reliable method to detect scaphoid fractures and to assess their healing without the need of cast removal.     

Occult fractures of the carpals and metacarpals: demonstration by CT

Occult fractures of the carpals and metacarpals occur frequently and are associated with major disability. The cross-sectional display and superior resolution of CT are well suited to the demonstration of these fractures. Sixteen patients with pain and negative conventional radiographs were chosen for further evaluation by CT. Imaging was performed in two planes and showed 21 fractures. The transaxial plane was the most revealing imaging plane. Coronal imaging was equal or superior to the transaxial plane in most fractures of the scaphoid, lunate, capitate, and pisiform bones and of the bases of the metacarpal bones. The direct sagittal plane was the best imaging plane in one patient with fractures of the scaphoid and lunate bones. After discovery of the fracture on CT, surgical removal of the avulsed fracture fragment was recommended in seven patients and fusion was recommended in three. Eight patients had a marked decrease in pain after the surgical procedure. The accuracy of CT for the demonstration of occult fractures may result in earlier recognition of these fractures and a reduction in the associated disability.     

Radiological findings and healing patterns of incomplete stress fractures of the pars interarticularis

Objective The objective was to retrospectively record the CT and MRI features and healing patterns of acute, incomplete stress fractures of the pars interarticularis. Method The CT scans of 156 adolescents referred with suspected pars interarticularis stress fractures were reviewed. Patients with incomplete (grade 2) pars fractures were included in the study. Fractures were assessed on CT according to vertebral level, location of cortical involvement and direction of fracture propagation. MRI was also performed in 72 of the 156 cases. MRI images of incomplete fractures were assessed for the presence of marrow oedema and cortical integrity. Fracture healing patterns were characterised on follow-up CT imaging. Results Twenty-five incomplete fractures were identified in 23 patients on CT. All fractures involved the inferior or infero-medial cortex of the pars and propagated superiorly or superolaterally. Ninety-two percent of incomplete fractures demonstrated either complete or partial healing on follow-up imaging. Two (8%) cases progressed to complete fractures. Thirteen incomplete fractures in 11 patients confirmed on CT also had MRI, and 92% demonstrated oedema in the pars. Ten out of thirteen fractures (77%) showed a break in the infero-medial cortex with intact supero-lateral cortex, which correlated with the CT findings. MRI incorrectly graded one case as a complete (grade 3) fracture, and 2 cases as (grade 1) stress reaction. Six fractures had follow-up MRI, 67% showed partial or complete cortical healing, and the same number showed persistent marrow oedema. Conclusions Incomplete fracture of the pars interarticularis represents a stage of the evolution of a complete stress fracture. The direction of fracture propagation is consistent, and complete healing can be achieved in most cases with appropriate clinical management. CT best demonstrates fracture size and extent, and is the most appropriate modality for follow-up. MRI is limited in its ability to fully depict the cortical integrity of incomplete fractures of the pars, but the presence of marrow oedema on fat-saturated T2-weighted sequences is a useful means of detecting acute spondylolysis.     

Scaphoid and pronator fat stripes are unreliable soft tissue signs in the detection of radiographically occult fractures

AIM: To determine the clinical value of scaphoid and pronator fat stripes in identifying occult underlying scaphoid and distal radius fractures, respectively. MATERIALS AND METHODS: In our department, all patients with clinically suspected scaphoid fractures and normal scaphoid series of radiographs undergo magnetic resonance imaging (MRI) of the wrist. We selected 50 cases with unequivocal MRI evidence of scaphoid fracture, 50 cases with distal radius fracture and 50 cases with no MRI evidence of bony injury. All 150 initial plain radiographs were examined retrospectively in random order without knowledge of the MRI findings and the scaphoid and pronator fat stripes scrutinized. RESULTS: The scaphoid fat stripe was abnormal in only 25 cases (50%) with confirmed scaphoid fracture on MRI. The pronator fat stripe was abnormal in 13 cases (26%) with confirmed distal radius fracture. In the 50 cases with no MRI evidence of bony injury, the scaphoid fat stripe and pronator fat stripe were abnormal in 25 (50%) and 15 (30%) cases, respectively. The sensitivity and specificity for an abnormal scaphoid fat stripe was 50%. The sensitivity and specificity for an abnormal pronator fat stripe was 26 and 70%, respectively. CONCLUSION: Scaphoid and pronator fat stripes are poor predictors of the presence or absence of underlying occult fractures.     

Imaging and treatment of scaphoid fractures and their complications

The scaphoid is the most commonly fractured carpal bone, with frequent complications that are predisposed by its anatomical location, anatomical configuration (shape and length), and vascular supply. The most common mechanism of injury is a fall onto an outstretched hand. Imaging plays a significant role in the initial evaluation and treatment of scaphoid fractures and their complications. Radiography should be the first imaging modality in the initial evaluation and follow-up of scaphoid fractures. Computed tomography with its superb spatial resolution enables better visualization and characterization of the fracture line, and the amount of displacement and angulation of the fracture fragments. Using the metal reduction artifact with computed tomography allows good follow-up of scaphoid fractures despite surgical hardware. Magnetic resonance imaging without contrast is the imaging modality of choice for depiction of radiographically occult scaphoid fracture, bone contusion, and associated soft tissue injury; contrast-enhanced imaging aids assessment of scaphoid fracture nonunion, osteonecrosis, fracture healing after bone grafting, and revitalization of the necrotic bone after bone grafting. Proper identification and classification of scaphoid fracture and its complications is necessary for appropriate treatment. This article describes the normal anatomy, mechanism of injury, and classification of stable and unstable fractures, together with the imaging and treatment algorithm of scaphoid fractures and their complications with an emphasis on magnetic resonance imaging.     

A comparison of bone scintigraphy and MRI in the early diagnosis of the occult scaphoid waist fracture

Objective. To determine the accuracy of MRI in the assessment of the radiographically occult scaphoid fracture. Design. This prospective study compared the sensitivity and specificity of MRI for detection of radiographically occult scaphoid fractures with bone scintigraphy (BS), the currently accepted imaging modality of choice. Consecutive patients with clinical signs of a scaphoid injury but no evidence of fracture on plain radiographs at presentation and after 7–10 days were evaluated by MRI and BS. All images were reported in masked fashion and the sensitivities and specificities of the imaging modalities determined. All patients with a scaphoid fracture demonstrated by MRI or BS were followed for at least a year after injury. Patients. Forty-three subjects (aged 12–74 years) had both MRI and BS carried out on average 19 days from the injury date. Results and conclusions. Six patients (14%) had scaphoid waist fractures. There were other bony injuries in a further six. In 40 patients there was agreement between the BS and MRI findings. In three cases there was discrepancy between the imaging modalities; in all three MRI was found to be the more sensitive and specific. MRI could become the investigation of choice for this injury.     

High-resolution CT of the wrist: initial experience with scaphoid disorders and surgical fusions

We performed high-resolution CT scans on 30 wrists in 27 patients with either previous surgical intercarpal fusion or known or suspected scaphoid abnormalities. Most examinations used the same protocol: contiguous 1.5-mm axial sections parallel to the long axis of the body of the scaphoid, small reconstruction circle, and bone reconstruction algorithm. Fifteen patients were evaluated for union of previous surgical carpal fusions; eight patients were evaluated for healing of scaphoid fractures; and the other four patients had miscellaneous disorders, including a midcarpal dislocation with a scaphoid fracture. High-resolution CT clearly showed whether the carpal fusions were united. In addition, metallic fixation devices were easy to locate and did not significantly degrade image quality. Osseous union of healing scaphoid fractures was reliably assessed. We conclude that high-resolution CT of the wrist is a useful method for evaluating surgical carpal fusions and various disorders of the scaphoid.     

Magnetic resonance imaging of suspected scaphoid fractures using a low field dedicated extremity MR system

AIM: To determine whether magnetic resonance imaging (MRI) using a dedicated extremity system could be utilized for the routine assessment of patients with a clinically suspected scaphoid fracture, and to determine the most cost-effective timing of MRI for these patients. MATERIALS AND METHODS: MRI of the wrist using a 0.2T extremity MR system was performed in two groups of patients. Fifty-six patients were examined within 4 days of injury and 53 with persistent symptoms at 10 days to 6 weeks following injury. A scaphoid series of radiographs was negative in both groups. RESULTS: The early MR group had seven scaphoid, six radial and four other fractures. Management was altered in 89%. The late MR group had 14 scaphoid, nine radial and three other fractures. Management was altered in 69%. A cost model showed that overall costs are less with early rather than late scanning. CONCLUSION: MRI of the wrist when scaphoid fracture is suspected can be undertaken in all patients with negative radiographs and could be performed in most departments with an MRI machine. There are significant patient benefits and overall costs would change little from conventional practice.     

Observer variation in MRI for suspected scaphoid fractures

The aim of this study was to evaluate prospectively the observer variation in the detection of pathology on MRI for suspected acute scaphoid fracture. 79 consecutive MR scans were included to calculate the inter-observer variation. All patients were suspected of having a scaphoid fracture but had no fracture on radiographs. 38 randomly chosen MR scans were used to calculate the intra-observer variation. Four observers, with varying levels of expertise, blinded scored three items: (i) scaphoid fracture, (ii) localization of a scaphoid fracture, and (iii) another fracture. The observer variation was analysed using the kappa statistic. The inter-observer variation for a scaphoid fracture showed substantial agreement. For the localization of a scaphoid fracture and another fracture, there was a moderate and substantial agreement, respectively. The intra-observer variation for a scaphoid fracture had an almost perfect agreement. For the localization of a scaphoid fracture and another fracture, there was an almost perfect and substantial agreement, respectively. In conclusion, the observer variation in MRI of suspected scaphoid fractures was low. The influence of expertise with MRI in daily practice should be taken into consideration. Observers with little experience of MRI will identify all scaphoid fractures but are likely to over-diagnose injuries. Based on these results, it is recommended that all scans are reviewed by an experienced radiologist.     

MRI diagnosis of fracture of the scaphoid bone: Impact of a new practice where the images are read by radiographers

RATIONALE AND OBJECTIVES: To investigate whether magnetic resonance imaging (MRI) radiographers are able to evaluate MRI examinations with regard to scaphoid fractures to save patients unnecessary immobilization and clinical and radiographic examinations, and to reduce the costs for the hospital as well as society in general. MATERIALS AND METHODS: Over a 1-year period 224 consecutive patients with a suspected clinical scaphoid fracture but negative radiography were referred for MRI and examined within 11 hours. The MR images were primarily evaluated by the MRI radiographer on duty. Other fractures and bone edema were not reported because these were not part of the work-up protocol agreed upon by the radiology and the orthopedic departments. The following weekday a final report was provided by a radiologist. For the economical analysis the official price-list for Danish hospital service was used. RESULTS: The MRI radiographers reported 43 scaphoid fractures, whereas the radiologist ultimately diagnosed only 36 scaphoid fractures (16.1% of patients) (sensitivity, 100%; specificity, 96.3%). Six of the seven false-positive fractures occurred in patients with edema of the scaphoid. The seventh false-positive was a fracture of the capitate. The hospital saved at least 20,000 and the social care system 70.000. CONCLUSION: It is possible to provide an acute MRI service to patients with clinically suspected fracture of the scaphoid and a normal plain radiograph. The MR images can be primarily read by sufficiently trained MR radiographers. This new work-up protocol reduces the cost for society.     

CT study of fractures and pseudarthroses of the carpal scaphoid

The authors analyze a group of 6 patients suffering from fractures and pseudoarthrosis of the carpal scaphoid; some of them were treated with Herbert bone screw. The authors emphasize the utility of CT, as proposed by Sanders (1988), in both pre- and postoperative evaluation of such conditions, since conventional X-rays can provide questionable findings as to both the state of the bone in the proximal fragment and the healing process at the fracture line.     

Clinical utility of tomosynthesis in suspected scaphoid fracture. A pilot study

Background  

Radiography alone will not detect all scaphoid fractures. There is a reported prevalence between 9 and 33% of occult scaphoid fractures. The evidence-based literature suggests that magnetic resonance imaging (MRI) is the most suitable secondary imaging modality due to the ability to evaluate the bone marrow directly and to also identify other injuries. However, there is no consensus on the choice of follow-up imaging strategy—computed tomography, MRI, or bone scan—across different institutions. Tomosynthesis is a new digital tomographic method creating multiple thin tomographic sections. The purpose of this study was to evaluate the clinical utility of tomosynthesis in suspected occult fracture.     

The efficacy of plain films vs MRI in the detection of scaphoid fractures

An investigation was carried out to determine whether or not professionals perceived plain film radiography to be the ‘gold-standard’ in the detection of scaphoid fractures. Literature highlighted that plain film radiography was an unreliable method for detecting such fractures and that magnetic resonance imaging (MRI) should now be regarded as the new ‘gold-standard’.Using a quantitative method, a total of 100 postal questionnaires were sent out to radiologists in 20 different imaging departments throughout the United Kingdom (UK) asking them their opinion on this controversial subject. In addition, the investigation looked into the use of MRI within each department in trying to determine whether or not it was surpassing plain film radiography as an established practice for detecting scaphoid fractures.Of the 100 questionnaires that were sent out, a total of 45 were returned from a total of 13 different departments.The results of this investigation conclude that plain film radiography is still used as a primary imaging modality to detect scaphoid fractures in all departments. There was much support for the use of plain film radiography with the modality being praised time and time again for its ease, 24-h availability, low cost and reproducibility.MRI was acknowledged as being superior in its capability to detect scaphoid fractures in comparison to plain films; its current use, however, is limited owing to high costs, lack of availability and long waiting lists. It would appear from this study that MRI is regarded as a useful modality in cases whereby plain film radiography fails to detect the presence or absence of a fracture in clinically positive patients, with great future potential.     

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.     

Scaphoid bone]

The scaphoid is the most important carpal bone due to the frequency of its pathological involvement. Two points of radiological anatomy are stressed: the presence of the scaphoid tubercle whose projection gives rise to the scaphoid ring, the solid radio-capitatum ligament which bridges the scaphoid. Scaphoid fracture represents 70% of all carpal bone fractures and its presence must therefore be meticulously investigated on appropriate x-rays or on tomographies or CT scans, rather than by the classical repeat examination a fortnight later. CT provides good analysis of scaphoid fragments when consolidation is delayed (pseudarthrosis), allowing earlier and more justified indications for surgery. The wrist ligaments are poorly visualised by MRI at the present time; but it allows study of the cartilage and, most importantly, is a decisive examination when there is a doubt about bone vitality.     

CT of fresh fractures of the carpal scaphoid with regard to attenuation changes and healing

Fourteen patients with fresh fractures through the waist of the carpal scaphoid were studied with repeated CT examinations to evaluate attenuation changes. Sclerosis, either absolute or relative, was found in a part of the proximal fragment in all cases except one. In spite of this all faractures healed without complications. Thus sclerosis of a part of the proximal fragment does not prognosticate non-union. Attenuation in the distal fragment and the area adjacent to the fracture in the proximal fragment diminished considerably. The identical reaction in these two areas suggests that the area adjacent to the fracture does not become devascularised, or is revascularised very quickly, which probably explains why the fractures heal in spite of proximal pole sclerosis.Correspondence to: P. Carlander     

Diagnosis and treatment of scaphoid fractures

The scaphoid bone in the wrist is the most frequently fractured carpal bone. This Directed Reading discusses types of scaphoid fractures, issues of special concern (eg, the risk of avascular necrosis and delayed union or non-union), steps involved in bone fracture healing and various imaging modalities used for scaphoid fracture diagnosis. Types of fracture management such as casting and surgical intervention are examined. Factors that can negatively influence bone healing, such as certain disease processes and tobacco use, are also investigated. This article is a Directed Reading. Your access to Directed Reading quizzes for continuing education credit is determined by your area of interest. For access to other quizzes, go to www.asrt.org/store.