Gadolinium-enhanced dynamic MRI of the fractured carpal scaphoid: preliminary results

Imaging of football injuries to the upper extremity

Imaging of football players is unique in many ways. Familiarity with mechanisms of injury, position of the player, and the need for rapid diagnosis and reporting will help radiologists when dealing with these athletes. Although plain radiographs are typically the first imaging modality used, MR imaging has become the cornerstone on which diagnoses and treatment decisions are based. As these athletes become stronger, faster, and more skilled, the ability to accurately assess their injuries becomes even more important, and understanding of the challenges that these patients present becomes critical.

Assessment of perfusion in normal carpal bones with dynamic gadolinium-enhanced MRI at 3 Tesla

PURPOSE

To investigate the normal enhancement patterns of the scaphoid, lunate, and capitate bones with dynamic contrast-enhanced magnetic resonance imaging (MRI).

MATERIALS AND METHODS

The study was approved by the hospital's Ethics Committee. Nineteen volunteers (13 female, 6 male; mean age 38 years) were examined and all gave written consent. Perfusion was assessed at 3 Tesla using dynamic contrast-enhanced MRI. After two-dimensional (2D) motion correction of the data set, regions of interest were placed in the capitate, lunate, and distal and proximal pole of scaphoid bone and from the mean signal intensities (SI), the enhancement was computed. The four locations were compared for time to peak, delay time, maximum enhancement, and maximum slope using Friedman's two-way analysis of variance.

RESULTS

Typical SI versus time curves revealed two components: a faster component with strong contrast enhancement and a slow component with prolonged enhancement. The mean value (standard deviation, SD) for maximum enhancement was 51 (33)% in the capitate, 54 (25)% in the lunate, 51 (34)% in the proximal pole and 51 (28)% in the distal pole of the scaphoid. The result of the Friedman test showed no significant difference (P < 0.05) in the perfusion variables between the capitate, lunate, and distal and proximal scaphoid bones.

CONCLUSION

Assessment of perfusion in normal carpal bone using contrast-enhanced MRI is possible. Optimization of the method and understanding of the normal perfusion may allow evaluation of pathological conditions such as osteonecrosis.

Diffusion MRI in ischemic epiphysis of the femoral head: an experimental study

PURPOSE

To evaluate whether line-scan diffusion-weighted imaging (LSDWI) can provide temporal information of epiphyseal ischemia.

MATERIALS AND METHODS

Ischemia was induced by ligation of arteries of the unilateral femoral head in piglets (N = 25). LSDWI was performed at several time points after ligation. A comparison of apparent diffusion coefficients (ADCs) was made between ischemic and control sides. The difference in percentage change of ADC in the ischemic hips between two neighboring time points was evaluated. A histological study was made after MR scanning.

RESULTS

Three hours after ligation, ADCs were significantly lower in the ischemic hips than in the contralateral (control) hips. At 72 hours after surgery, ADCs in the ischemic hips were significantly higher than in the control hips and continued to rise up until the sixth week after operation. Histological study revealed necrosis of chondrocytes and osteocytes and abnormal thickening of the epiphyseal cartilage in the ischemic femoral head.

CONCLUSION

The ADCs may be used as a marker of ischemia and necrosis in the femoral head; changes in the ADCs after the acute ischemia may reflect the evolution of ischemia and subsequent necrosis. LSDWI can be used for the evaluation of the duration and extent of ischemic injury in the epiphysis.

[The diagnosis of recent scaphoid fractures: review of the literature]

Fractures of the scaphoid are the most common carpal fractures. A review of the literature indicates that the prevalence of the fracture in the case of clinical suspicion is less than 50%. A quality X-ray examination remains essential as an initial diagnostic tool in the evaluation of scaphoid fractures. Its sensitivity varies from 59 to 79%. Patients with negative X-rays present with about 18.7% of scaphoid fractures; 5% of bruised scaphoid; 13% of radius fractures and 7% of miscellaneous bone lesions. If not treated promptly, a scaphoid fracture may be compounded by non-union with associated risk factors such as avascular necrosis and osteoarthritis. Considering these risks, patients with suspected scaphoid fracture with normal X-rays, routinely undergo wrist immobilization until imaging confirms or denies the presence of fracture. Consequently, more than half of the patients undergo wrist immobilization needlessly. This may have a negative impact on their professional life and personal activities while representing a high medical cost. MRI is the imaging technique of choice for suspicious or negatice X-rays. MDCT is less costly than MRI or bone scan, readily available and highly effective for trauma patients but is lacks accuracy and should be used with caution in this indication.

The role of MR imaging in scaphoid disorders

The scaphoid bone of the wrist is one of the most commonly fractured bones in the body. Due to its importance in the biomechanics and functionality of the wrist, it is important to depict and characterize the type of injury. Plain radiographs and scintigraphy may fail to disclose the type and severity of the injury. In patients with normal initial plain radiographs, MR imaging can discriminate occult fractures from bone bruises and may also demonstrate ligamentous disruption. MR imaging can also discriminate the proximal pole viability versus avascular necrosis secondary to previous fracture, which is important for treatment planning. Treatment of non-united fractures with vascularized grafts can be evaluated with contrast-enhanced MR imaging. Idiopathic osteonecrosis or Preiser's disease was originally described after trauma. The non-traumatic disorders of the scaphoid include post-traumatic osteoarthritis, inflammatory bone marrow edema in patients with rheumatoid arthritis, and osteomyelitis. MR imaging is helpful in all the above disorders to demonstrate early bone marrow edema, cartilage degeneration and associated subchondral marrow changes. The most commonly found tumors in the scaphoid are usually benign and include enchondroma, osteoblastoma and osteoid osteoma. MR imaging is not mandatory for the initial diagnosis, which should be based on plain X-ray findings.

Increased Radiodensity of the Proximal Pole of the Scaphoid

OBJECTIVES

To determine whether the proximal pole (PP) of the scaphoid is denser than the distal pole (DP) in a diverse population of patients undergoing computed tomography (CT) imaging of the wrist.

METHODS

Sixty-nine patients who had CT of the wrist were retrospective reviewed. We measured CT density of the medullary bone of PP and DP of the scaphoid and calculated PP/DP ratio. To evaluate the variability of PP/DP ratio, we compared the ratios of these 3 groups. These patients were separated into 3 groups based on their diagnoses: group 1, healed scaphoids treated by casting; group 2, scaphoid nonunions; group 3, intact scaphoids.

RESULTS

Proximal pole was denser than DP in most subjects. Proximal pole/distal pole ratio was similar among groups (P < 0.05). Fracture healing, sex, and age did not affect this ratio. However, we did not study scaphoids with avascular necrosis.

CONCLUSIONS

Proximal pole was denser than DP in most of our subjects, including those with intact scaphoids, healing scaphoid fractures, and nonunions.

Role of MR imaging in chronic wrist pain

Magnetic resonance (MR) imaging for chronic wrist pain is challenging. Correct assessment of the triangular fibrocartilage, hyaline cartilage, ligaments, and tendons has become mandatory for comprehensive decision making in wrist surgery. The MR technique, potential and limits of MR imaging in patients with chronic wrist pain will be discussed. MR arthrography with injection of gadolinium-containing contrast material into the distal radioulnar joint is suggested for evaluation of the triangular fibrocartilage. The clinically meaningful ulnar-sided peripheral tears are otherwise hard to diagnose. The diagnostic performance of MR imaging for interosseous ligament tears varies considerably. The sensitivity for scapholunate ligament tears is consistently better than for lunotriquetral ligament tears. Gadolinium-enhanced MR imaging is considered to be the best technique for detecting established avascularity of bone, but the assessment of the MR results remains challenging. Most cases of ulnar impaction syndrome have characteristic focal signal intensity changes in the ulnar aspect of the lunate. Avascular necrosis of the lunate (Kienböck's disease) is characterized by signal changes starting in the proximal radial aspect of the lunate. MR imaging is extremely sensitive for occult fractures. Questions arise if occult posttraumatic bone lesions seen on MR images only necessarily require the same treatment as fractures evident on plain films or computed tomography (CT) images. MR imaging and ultrasound are equally effective for detecting occult carpal ganglia. Carpe bossu (carpal boss) is a bony protuberance of a carpometacarpal joint II and III which may be associated with pain.

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.

Normal and ischemic epiphysis of the femur: diffusion MR imaging study in piglets

PURPOSE

To evaluate normal diffusion characteristics in the femur in piglets and changes in diffusion with increasing duration of femoral head ischemia.

MATERIALS AND METHODS

Normal epiphyses, physes, and metaphyses of piglets were evaluated with line-scan diffusion imaging (n = 12) and diffusion-tensor imaging (n = 4). Apparent diffusion coefficient (ADC) differences between normal proximal and distal femoral structures, epiphyseal and physeal cartilage, and epiphyseal and metaphyseal marrow were compared (Mann-Whitney test). Short-term femoral ischemia was investigated after maximal abduction of the hips for 3 hours (n = 6); ADCs before and after abduction were compared (Wilcoxon signed rank test). Prolonged ischemia was investigated with placement of a ligature around the neck of a femur (n = 7); the ADC of the femur in this condition was compared (Wilcoxon signed rank test) with that of the normal contralateral femur. Changes in ADC ratios at three durations of ischemia (Kruskal-Wallis test) were compared.

RESULTS

ADC was greater in epiphyseal cartilage (mean +/- 1 SD, 1.62 x 10(-3) mm2/sec +/- 0.38) than it was in physeal cartilage (1.28 x 10(-3) mm2/sec +/- 0.31) (P <.007) and greater in epiphyseal marrow (1.26 x 10(-3) mm2/sec +/- 0.38) than it was in metaphyseal marrow (0.91 x 10(-3) mm2/sec +/- 0.35) (P <.001). There was columnar arrangement of tensors in the physis. ADC decreased 26% after 3 hours of maximal abduction. After femoral neck ligature, ADC increased a mean of 27% after 6 hours and a mean of 75% after 96 hours.

CONCLUSION

Normal line-scan diffusion imaging findings indicate relative restriction of diffusion in the metaphysis and parallel orientation of tensors in the physis. Diffusion is initially restricted with decreased blood flow but increases if ischemia lasts longer.

The relationship between proximal pole blood flow and the subjective assessment of increased density of the proximal pole in acute scaphoid fractures

The cause and importance of increased density of the proximal pole of the scaphoid seen in radiographs after an acute fracture were investigated. Blood flow to the proximal poles of 32 nonsurgically treated scaphoid fractures were assessed 1 to 2 weeks after injury by measuring their uptake of gadopentetate dimeglumine with dynamic magnetic resonance imaging and calculating its steepest slope and percentage of enhancement values. Initial (week 0) and week 8 scaphoid series radiographs were independently assessed by 2 observers for increased proximal pole density; both agreed that the density had increased during treatment in 9 fractures. All 9 fractures united, suggesting that increased proximal pole density is not a major determinant of fracture outcome. Increased density of the proximal pole was associated with low proximal pole blood flow, but this relationship was not absolute, suggesting that other factors contribute to the appearance of increased density.

Scaphoid fractures: evaluation with high-spatial-resolution US initial results

PURPOSE

To evaluate the diagnostic accuracy of high-spatial-resolution ultrasonography (US) in the diagnosis of scaphoid fractures.

MATERIALS AND METHODS

In 72 hours after acute wrist trauma, 15 consecutive patients were examined for possible scaphoid fractures clinically and with conventional radiographs, including scaphoid views. Thereafter, high-spatial-resolution US was performed by two experienced radiologists blinded to the results of the previously performed investigations. High-spatial-resolution US of the scaphoid bones was performed from the palmar, lateral, and dorsal directions in the longitudinal and transverse planes. US findings indicative of a scaphoid fracture were cortical discontinuity and/or periosteal elevation. Finally, magnetic resonance (MR) images (short inversion time inversion-recovery, T1- and T2*-weighted) (ie, the standard) of the affected wrist were obtained and evaluated for a possible scaphoid fracture by two radiologists in consensus.

RESULTS

Nine of 15 patients had scaphoid fractures. Seven (78%) of nine patients had positive findings at high-spatial-resolution US and five (56%) had such findings at conventional radiography (ie, four occult scaphoid fractures), with an accuracy of 87% and 73%, respectively. Two (50%) of four radiographically occult scaphoid fractures were depicted with high-spatial-resolution US. Sonographic findings of scaphoid fractures were either cortical discontinuity (n = 4), periosteal elevation (n = 2), or a combination of these two findings (n = 1).

CONCLUSION

High-spatial-resolution US is a reliable diagnostic tool for the evaluation of occult scaphoid fractures and should be considered an adequate alternative diagnostic tool prior to computed tomography or MR imaging.

Wrist fractures: what the clinician wants to know

With the recent improvements in diagnosis and treatment of distal radius and carpal injuries, the hand surgeons' expectations of relevant radiologic interpretation of imaging studies are heightened. Conventional radiographic examinations, as well as more sophisticated and invasive studies, have important roles in the evaluation of wrist fractures and dislocations. On the basis of physical examination results and the mechanism of injury, the onus is on the examining surgeon to pinpoint potential sites of bone or ligament disruption. After this evaluation, appropriate imaging studies appropriately performed and interpreted will help direct treatment and improve outcome with greater clarity and certainty.

Magnetic resonance imaging of the wrist: diagnostic performance statistics

AIM

To review the published diagnostic performance statistics for magnetic resonance imaging (MRI) of the wrist for tears of the triangular fibrocartilage complex, the intrinsic carpal ligaments, and for osteonecrosis of the carpal bones.

MATERIALS AND METHODS

We used Medline and Embase to search the English language literature. Studies evaluating the diagnostic performance of MRI of the wrist in living patients with surgical confirmation of MR findings were identified.

RESULTS

We identified 11 studies reporting the diagnostic performance of MRI for tears of the triangular fibrocartilage complex for a total of 410 patients, six studies for the scapho-lunate ligament (159 patients), six studies for the luno-triquetral ligament (142 patients) and four studies (56 patients) for osteonecrosis of the carpal bones.

CONCLUSIONS

Magnetic resonance imaging is an accurate means of diagnosing tears of the triangular fibrocartilage and carpal osteonecrosis. Although MRI is highly specific for tears of the intrinsic carpal ligaments, its sensitivity is low. The diagnostic performance of MRI in the wrist is improved by using high-resolution T2* weighted 3D gradient echo sequences. Using current imaging techniques without intra-articular contrast medium, magnetic resonance imaging cannot reliably exclude tears of the intrinsic carpal ligaments. Hobby, J. L. (2001). Clinical Radiology, 56, 50-57.