Value of a dynamic MR scan in predicting vascular ingrowth from free vascularized scapular transplant used for treatment of avascular femoral head necrosis

Quantifying lumbar vertebral perfusion by a Tofts model on DCE-MRI using segmental versus aortic arterial input function

The purpose of this study was to investigate the influence of arterial input function (AIF) selection on the quantification of vertebral perfusion using axial dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). In this study, axial DCE-MRI was performed on 2 vertebrae in each of eight healthy volunteers (mean age, 36.9 years; 5 men) using a 1.5-T scanner. The pharmacokinetic parameters K^trans, v_e, and v_p, derived using a Tofts model on axial DCE-MRI of the lumbar vertebrae, were evaluated using various AIFs: the population-based aortic AIF (AIF_PA), a patient-specific aortic AIF (AIF_A) and a patient-specific segmental arterial AIF (AIF_SA). Additionally, peaks and delay times were changed to simulate the effects of various AIFs on the calculation of perfusion parameters. Nonparametric analyses including the Wilcoxon signed rank test and the Kruskal–Wallis test with a Dunn–Bonferroni post hoc analysis were performed. In simulation, K^trans and v_e increased as the peak in the AIF decreased, but v_p increased when delay time in the AIF increased. In humans, the estimated K^trans and v_e were significantly smaller using AIF_A compared to AIF_SA no matter the computation style (pixel-wise or region-of-interest based). Both these perfusion parameters were significantly greater using AIF_SA compared to AIF_A.

Accuracy and limitations of diagnostic methods for avascular necrosis of the hip

INTRODUCTION

Femoral head avascular necrosis (FHAVN) is the result of irreversible anoxia of the subchondral bone. The death of bone cells can cause articular collapse and pain, and in turn usually leads to degenerative arthritis. FHAVN is a common disorder, affecting mainly young male adults. Reliability, accuracy and prognostic value of any classification system are important in evaluation and treatment of FHAVN.

AREAS COVERED

Although in the past, scintigraphy and CT and more recently PET have been used for diagnosing AVN, currently the most important imaging methods included in the most widely used classification systems, consist of radiographs and magnetic resonance imaging (MRI). The latter is used in major classification systems for early detection (pre-radiographic stage) of FHAVN and for assessing lesion size and location before collapse of the articular surface occurs. The purpose of this review is to present the current data regarding the accuracy of the X-rays and MRI in diagnosing, monitoring and postoperative evaluation of FHAVN.

EXPERT OPINION

The author's opinion is that MRI may contribute to improve staging, investigate radiologically occult collapse, depict other causes of disability and pain, assess prognosis and evaluate treatment. Newer MRI techniques, such as diffusion-weighted imaging and perfusion imaging, have not yet provided additional and clinically useful information.

Recovery of the blood flow around the femoral head during early corticosteroid therapy: dynamic magnetic resonance imaging in systemic lupus erythematosus patients

Disturbance of blood supply to the femoral head is a risk factor for corticosteroid-associated osteonecrosis. The aim was to measure blood supply of the proximal femur during corticosteroid therapy in systemic lupus erythematosus (SLE) patients. We repeatedly performed 78 dynamic MRIs of 19 hip joints in 19 SLE patients after initiation of corticosteroid administration for one year. Blood supply of the femoral head (epiphysis, growth plate, and metaphysis), the femoral neck, and the medial circumflex femoral artery were measured in terms of peak percent enhancement. At the first month, blood supply of the growth plate was significantly higher in the pediatric group (<15 years old) than in the adolescent and adult group (>15 years old). At the fourth month, blood supply in every part of the femoral head (epiphysis, growth plate, and metaphysis) was significantly higher in the pediatric group than in the adolescent and adult group. Multiple regression analysis revealed that blood supply to the femoral head depended on the number of days after initiation of corticosteroid administration and the age at the time of dynamic MRI. Blood supply to the femoral head is abundant in pediatric patients and is a function of the number of days after initiation of corticosteroid administration.

Intervertebral disk degeneration related to reduced vertebral marrow perfusion at dynamic contrast-enhanced MRI

OBJECTIVE

The purpose of this study was to use dynamic contrast-enhanced MRI to ascertain the relation between intervertebral disk degeneration and lumbar vertebral marrow blood perfusion.

SUBJECTS AND METHODS

We recruited 25 patients (50 vertebral bodies) who underwent dynamic contrast-enhanced MRI of the lumbar spine. The peak signal enhancement of each vertebral body was calculated from the time signal after curve fitting of a pharmacokinetic model. We controlled for other variables that might have affected blood perfusion by assessing two vertebral bodies in each patient. The 25 patients were divided into three groups. In group 1, one of the vertebral bodies (L1 or L3) evaluated was between two adjacent normal disks and the other was between two adjacent degenerated disks. In group 2, each of the two vertebral bodies evaluated was between two normal disks. In group 3 each of the two vertebral bodies evaluated was between two degenerated disks.

RESULTS

Without normalization by minimization of other variables, there were no statistically significant differences in original peak enhancement values among groups 1, 2, and 3 (p = 0.179). After normalization, the peak enhancement in group 1 (0.846 +/- 0.060) was significantly lower than that in group 2 (0.988 +/- 0.047) (p = 0.003) or group 3 (0.973 +/- 0.081) (p = 0.008).

CONCLUSION

After normalization, lumbar vertebral marrow perfusion correlated well with intervertebral disk degeneration evaluated with dynamic contrast-enhanced MRI. Blood perfusion was 14% less in the vertebral body marrow between two degenerated disks than in vertebral marrow between two normal disks.

Use of the scapular spine in lumbar fusion procedures: cadaveric feasibility study. Laboratory investigation

OBJECT

Graft sources for lumbar fusion include synthetic materials, donor grafts, and autologous bone such as the iliac crest. Considering the data indicating that autologous bone grafts generate the best results for fusion, the next logical step is to seek alternative donor sites in an attempt to reduce the complications associated with these procedures. To the authors' knowledge, autologous scapula has not been explored as a potential source for posterior lumbar fusion graft material. Therefore, the following study was performed to verify the utility of this bone in these procedures.

METHODS

Six adult cadavers (mean age 71 years), four formalin-fixed and two fresh specimens, were used in this study. With the cadaver in the prone position, an incision was made over the spine of the scapula. Soft tissues were stripped from the middle of this region of the scapula, and bone segments were removed with a bone saw and used for a posterior lumbar fusion procedure.

RESULTS

A mean length of 11.5 cm was measured for the spine of the scapula and the mean thicknesses of this bone at its medial part, segment just medial to the spinoglenoid notch, and acromion were 1 cm, 2.2 cm, and 2.5 cm, respectively. No obvious injury to surrounding vessels or nerves was found using this procedure, and adequate fusion was achieved with it.

CONCLUSIONS

Following clinical testing, such a bone substitute as autologous scapular spine might be a reasonable alternative to iliac crest grafts for use in posterior lumbar fusion procedures.

Use of colour duplex Doppler imaging in the postoperative assessment of buried free flaps

The postoperative assessment of free flaps is essential to identify and act on signs of incipient flap failure. Where the flap is completely buried, this becomes almost impossible unless part of the flap is exteriorised or an overlying skin window is used. Alternatively, complicated and often impractical monitoring devices have been advocated, but these have failed to gain widespread acceptance. A simpler solution to this problem has been evaluated in a series of patients using colour duplex Doppler imaging. This re-appraisal of a previously reported technique has been facilitated by updated technology in diagnostic radiology. Duplex Doppler imaging was confirmed as an accurate, non-invasive, and inexpensive tool for the postoperative measurement of blood flow within the pedicles of five buried free flaps in four patients undergoing surgery in our unit.