Assessment of Femoral Head Revascularization in Legg-Calvé-Perthes Disease Using Serial Perfusion MRI

BACKGROUND

Legg-Calvé-Perthes disease is a juvenile form of osteonecrosis of the femoral head. The purpose of this study was to use serial perfusion magnetic resonance imaging (MRI) to determine the pattern and rate of revascularization of the femoral heads of patients with the active stage of Legg-Calvé-Perthes disease.

METHODS

We performed a prospective study of 29 patients (30 hips) with a mean age (and standard deviation) of 8.4 ± 1.9 years who were diagnosed with Waldenström Stage-1 or 2 Legg-Calvé-Perthes disease. All patients had ≥2 perfusion MRIs, and 21 patients (22 hips) had ≥3. Perfusion percentages of the femoral epiphyses were measured by 2 independent observers. Statistical analyses included calculation of the intraclass correlation coefficient, the paired t test, the Mann-Whitney U test, and the Kruskal-Wallis test.

RESULTS

Initial perfusion MRIs showed the percent perfusion in the affected femoral heads to range from 5% to 70%. The average percent perfusion (and standard deviation) was 35% ± 16% on the first MRI, which increased to 77% ± 14% on the follow-up MRI acquired at an average of 10.5 ± 2.9 months later (p < 0.01). Serial assessment showed a general pattern of revascularization starting from the periphery of the posterior, lateral, and medial aspects of the femoral epiphysis and converging toward the anterocentral region. The average rate of revascularization was 4.9% ± 2.3% per month with a wide range among the patients (0.6% to 10.4% per month).

CONCLUSIONS

Revascularization of the necrotic femoral head increased over time in a horseshoe pattern, starting from the posterior, lateral, and medial aspects of the femoral epiphysis. The rate of revascularization was highly variable among patients.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Occult fracture of the femoral neck associated with extensive osteonecrosis of the femoral head: A case report

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Osteonecrosis of the femoral head should be included in the differential diagnosis of insufficiency fracture of the femoral neck.

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Enhanced MRI may be useful in determining the existence of extensive osteonecrosis of the femoral head.

Introduction

Although the subchondral portion of the femoral head is a common site for collapse in osteonecrosis of the femoral head (ONFH), femoral-neck fracture rarely occurs during the course of ONFH. We report a case of occult insufficiency fracture of the femoral neck without conditions predisposing to insufficiency fractures, occurring in association with ONFH.

Presentation of case

We report a case of occult fracture of the femoral neck due to extensive ONFH in a 60-year-old man. No abnormal findings suggestive of ONFH were identified on radiographs, and the fracture occurred spontaneously without any trauma or unusual increase in activity. The patient’s medical history, age, and good bone quality suggested ONFH as a possible underlying cause. Contrast-enhanced magnetic resonance imaging was useful in determining whether the fracture was caused by ONFH or was instead a simple insufficiency fracture caused by steroid use.

Discussion

The patient was treated with bipolar hemiarthroplasty, but if we had not suspected ONFH as a predisposing condition, the undisplaced fracture might have been treated by osteosynthesis, and this would have led to nonunion or collapse of the femoral head. To avoid providing improper treatment, clinicians should consider ONFH as a predisposing factor in pathologic fractures of the femoral neck.

Conclusion

ONFH should be included in the differential diagnosis of insufficiency fracture of the femoral neck.

Perfusion MRI in Early Stage of Legg-Calvé-Perthes Disease to Predict Lateral Pillar Involvement: A Preliminary Study

BACKGROUND

Current radiographic classifications for Legg-Calvé-Perthes disease cannot be applied at the early stages of the disease. The purpose of this study was to quantify the perfusion of the femoral epiphysis in the early stages of Legg-Calvé-Perthes disease with use of perfusion magnetic resonance imaging (MRI) and to determine if the extent of epiphyseal perfusion can predict the lateral pillar involvement at the mid-fragmentation stage.

METHODS

Twenty-nine patients had gadolinium-enhanced perfusion MRI at the initial stage or early fragmentation stage of Legg-Calvé-Perthes disease and were followed prospectively. The percent perfusion of the whole epiphysis and its lateral third was measured by four independent observers using image analysis software. The radiographs obtained at the mid-fragmentation stage were used for the lateral pillar classification. Intraclass correlation coefficient (ICC) and logistic regression analyses were performed.

RESULTS

The mean age (and standard deviation) at diagnosis was 7.7 ± 1.7 years (range, 5.3 to 11.3 years). The mean interval between the MRI and the time of maximum fragmentation was 8.2 ± 5.5 months. The interobserver ICC for the percent perfusion of the lateral third of the epiphysis was 0.90 (95% confidence interval [CI]: 0.83 to 0.95). The mean percent perfusion of the lateral third of the epiphysis was 92% ± 2%, 68% ± 18%, and 46% ± 12% for the hips in which the lateral pillar was later classified as A, B, and C, respectively (p = 0.001). When the perfusion level was ≥90% in the lateral third of the epiphysis, the odds ratio of the lateral pillar being later classified as group A, as opposed to B or C, was 72.0 (CI: 3.5 to 1476). With a perfusion level of ≤55% in the lateral third of the epiphysis, the odds ratio of the lateral pillar being later classified as group C, as opposed to A or B, was 33.3 (CI: 2.8 to 392). Similar results were obtained for the whole epiphysis.

CONCLUSIONS

Perfusion MRI measurements of the total epiphysis and its lateral third obtained at the early stages of Legg-Calvé-Perthes disease were predictive of lateral pillar involvement at the mid-fragmentation stage of the disease.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

MR imaging of children and young adults with classic findings of osteonecrosis on unenhanced MR images: do contrast-enhanced sequences help?

BACKGROUND

The added value of routine contrast-enhanced MR imaging in children with classic findings of osteonecrosis on unenhanced MR images has not been determined.

OBJECTIVE

Our purpose was to determine the added value of routine contrast-enhanced MR sequences for identifying complications of osteonecrosis.

MATERIAL AND METHODS

Sixty-four patients who underwent 139 contrast-enhanced MR examinations were retrospectively identified. Unenhanced images and subsequently both unenhanced and enhanced images were reviewed in consensus. The location of osteonecrosis and the presence of complicating features (epiphyseal collapse, marrow edema, joint effusion, soft tissue edema) were recorded. Cohen's kappa coefficients (κ) were calculated to assess agreement.

RESULTS

A diagnosis of classic osteonecrosis was made in 22.3% of unenhanced examinations and 28.1% of enhanced examinations (κ = 0.734, P < 0.001). Among patients with complicated osteonecrosis, unenhanced images interpreted without and with contrast-enhanced images showed epiphyseal collapse in 51.2% and 42.5% (κ = 0.796, P < 0.001), marrow edema in 50.4% and 46.8% (κ = 0.727, P < 0.001), joint effusion in 44.9% and 51.2% (κ = 0.686, P < 0.001), and soft tissue edema in 12.2% and 10.1% (κ = 0.674, P < 0.001).

CONCLUSION

The high observed agreement between the unenhanced MR images interpreted without and with contrast-enhanced images shows little marginal benefit from the use of routine contrast-enhanced imaging in children and young adults with classic findings of osteonecrosis on unenhanced MR images.

A comparison of non-contrast and contrast-enhanced MRI in the initial stage of Legg-Calvé-Perthes disease

BACKGROUND

A prognostic indicator of outcome for Legg-Calvé-Perthes disease (LCP) is needed to guide treatment decisions during the initial stage of the disease (stage 1), before deformity occurs. Radiographic prognosticators are applicable only after fragmentation (stage II).

OBJECTIVE

We investigated pre- and postcontrast MRI in depicting stage I femoral head involvement.

MATERIALS AND METHODS

Thirty children with stage I LCP underwent non-contrast coronal T1 fast spin-echo (FSE) and corresponding postcontrast fat-suppressed T1-weighted fast spin-echo (FSE) sequences to quantify the extent of femoral head involvement. Three pediatric radiologists and one pediatric orthopedic surgeon independently measured central head involvement.

RESULTS

Interobserver reliability of percent head involvement using non-contrasted MR images had intraclass correlation coefficient (ICC) of 0.72. Postcontrast MRI improved interobserver reliability (ICC 0.82). Qualitatively, the area of involvement was more clearly visible on contrast-enhanced MRI. A comparison of results obtained by each observer using the two MRI techniques showed no correlation. ICC ranged from -0.08 to 0.03 for each observer. Generally, greater head involvement was depicted by contrast compared with non-contrast MRI (Pearson r = -0.37, P = 0.04).

CONCLUSION

Pre- and postcontrast MRI assess two different components of stage I LCP. However, contrast-enhanced MRI more clearly depicts the area of involvement.

MRI of Legg-Calve-Perthes disease

OBJECTIVE

Legg-Calvé-Perthes disease is a common cause of hip pain in children that may be initially clinically and radiographically difficult to diagnose and stage. The purpose of this article is to describe and illustrate the various MRI appearances of this condition.

CONCLUSION

MRI may show proximal femoral abnormalities before radiography in the setting of Legg-Calvé-Perthes disease, allowing appropriate diagnosis and prompt treatment. MRI can also assess for revascularization, healing, and multiple complications.

Septic Arthritis Versus Transient Synovitis of the Hip: Gadolinium-Enhanced MRI Finding of Decreased Perfusion at the Femoral Epiphysis

OBJECTIVE

The purpose of this study was to identify differences in the MRI findings of septic arthritis and transient synovitis in patients with nontraumatic acute hip pain and hip effusion.

MATERIALS AND METHODS

The MRI findings in nine patients with septic arthritis and 11 with transient synovitis were reviewed retrospectively. This study was approved by our institutional review board. The diagnoses were based on findings at physical examination, laboratory studies, and joint aspiration and bacteriologic study. The MRI findings were analyzed with emphasis on the grade of joint effusion, alterations in signal intensity in the soft tissues and bone marrow, and the presence of decreased perfusion at the femoral head.

RESULTS

Low signal intensity on fat-suppressed gadolinium-enhanced T1-weighted coronal MRI suggesting decreased perfusion at the femoral head of the affected hip joint was seen in eight of nine patients with septic arthritis and in two of 11 patients with transient synovitis. Statistically reliable differences (p = 0.005) were found between the two groups. Alterations in signal intensity in the bone marrow were seen in three patients with septic arthritis but in none of the patients with transient synovitis. Decreased perfusion on fat-suppressed gadolinium-enhanced coronal T1-weighted MRI was seen in the six patients with septic arthritis who did not have alterations in signal intensity involving the bone marrow.

CONCLUSION

Decreased perfusion at the femoral epiphysis on fat-suppressed gadolinium-enhanced coronal T1-weighted MRI is useful for differentiating septic arthritis from transient synovitis.

Evaluation of femoral head vascularization in slipped capital femoral epiphysis before and after cannulated screw fixation with use of contrast-enhanced MRI: initial results

In this study we used contrast-enhanced magnetic resonance imaging (MRI) to evaluate the vascularization of the femoral head in children with slipped capital femoral epiphysis (SCFE) before and after cannulated screw fixation. Eleven consecutive children with SCFE, seven boys and four girls, aged 10-15 years were included in the study. There were no preslips; four children had acute, three acute-on-chronic, and four chronic SCFE. The MRI examinations were performed in a 1.5 Tesla MR scanner with use of a coronal STIR sequence, a coronal contrast-enhanced T1-weighted spin-echo sequence, and a sagittal three-dimensional gradient-echo sequence. Morphology, signal intensities, and contrast-enhancement of the femoral head were assessed by two radiologists in consensus. Morphologic distortion of the physis, bone marrow edema within the metaphysis and epiphysis, and joint effusion were the preoperative MRI findings of SCFE in each child. In nine children, the vascularization of the femoral head before and after surgery was normal. In one child, a preoperative avascular zone in the superolateral aspect of the epiphysis revascularized completely after surgery. One child with severe SCFE developed avascular necrosis of the femoral head after open reduction of the slip. We conclude that MRI allows for accurate evaluation of the femoral head vascularization before and after surgery in children with SCFE.

Imaging of traumatic dislocation of the hip in childhood

BACKGROUND

Traumatic hip dislocation in childhood is a rare consequence of violent trauma. After reduction, outcome is usually favourable although epiphyseal necrosis can occur. Reduction must be carried out as soon as possible and is achieved easily, although if the labrum is involved, surgery may be required to achieve complete reduction.

OBJECTIVE

To analyze a retrospective series of traumatic hip dislocations in children, describing the therapeutic and imaging strategy.

MATERIALS AND METHODS

A total of 42 patients were studied. Their mean age was 10 years 3 months. All relevant radiographic, CT, MRI and radionuclide bone scan examinations were reviewed. Special attention was paid to associated lesions.

RESULTS

In 22 patients the dislocation was caused by low-energy trauma. Road traffic accidents accounted for 17 dislocations. An acetabular fracture was present in six patients and the femoral head was fractured in three. Reduction was easily achieved in 31 patients. In 11 patients the postreduction radiograph and CT showed joint space asymmetry secondary to labral entrapment. Only two patients developed epiphyseal necrosis.

CONCLUSIONS

It has been difficult to define and evaluate accurate principles for a medical imaging strategy in this group of patients. Analysis of plain radiographs is essential before and after reduction of the joint, and it is important to perform postreduction CT in every patient whose joint space remains widened. A radionuclide bone scan should be performed between the second and third weeks after injury to assess epiphyseal vascularity. With the use of specific sequences, MRI may be an alternative modality to assess epiphyseal vitality.

LOW-FIELD MAGNETIC RESONANCE IMAGING OF BONE MARROW IN THE LUMBAR SPINE, PELVIS, AND FEMUR IN THE ADULT DOG

The purpose of this study was to describe the appearance of normal bone marrow in seven adult dogs using low-field (0.3T) magnetic resonance (MR) imaging. The areas imaged included the lumbar spine, pelvis, and femur. T1-weighted, fast spin-echo T2-weighted, and short tau (T1) inversion recovery (STIR) sequences were obtained at all locations. Histopathology was performed on sections from the sixth lumbar vertebral body, the wing of the ilium, and the femur (head and neck, mid-diaphysis, and condyle) for evaluation of cellularity and fat content. The lumbar spine and pelvic marrow MR images were similar in all dogs. The lumbar vertebral bone marrow was uniform, intermediate signal intensity, and isointense to muscle on all sequences. There was variation between dogs in the bone marrow distribution with MR imaging of the femur. In the proximal and mid-diaphysis of the femur there was patchy high-signal intensity on T1- and T2-weighted images, and hypointense foci on the STIR images. The distal femoral metaphysis had a variable pattern ranging from intermediate-to-high signal on T1- and T2-weighted images and intermediate-to-low signal on STIR images. The femoral condyles were uniformly high signal on T1- and T2-weighted images and hypointense on STIR images. Histopathologically there was a normal variation in the bone marrow cellularity. The marrow was normocellular (25-75% cellularity) for all sites examined except the femoral condyles, which were hypocellular (<25% cellularity).