Magnetic resonance imaging and histopathology in femoral head necrosis

Chondrosarcoma mimicking MRI of the osteonecrosis of the femoral head: a case report

A 25-year-old female visited our hospital with an 8-year history of arthralgia in the right hip joint. Plain radiography of the hip revealed a well-demarcated radiolucent lesion with a thin sclerotic rim in the epiphysis of the femoral head. T ₁ weighted MRI revealed the demarcation line of a low-signal-intensity band in the femoral head. We were aware that this band did not split the signal of adipose tissue in the bone marrow. In cases of osteonecrosis, we usually find a low-signal-intensity band splitting the signal of normal bone marrow. However, we could not see such a low-signal-intensity band in this case. Therefore, we decided to perform other studies. Contrast-enhanced T ₁ weighted MRI showed remarkable enhancement in the segment proximal to the low-signal-intensity band, indicating that this lesion might have blood perfusion. We decided to perform a bone biopsy to clarify the diagnosis. Histopathological examination of the biopsy specimen revealed chondrosarcoma. We found that contrast-enhanced MRI plays an important role to rule out osteonecrosis of the femoral head.

Low Field Magnetic Resonance Imaging of Femoral Neck Fractures

Fourteen patients with cervical hip fractures were treated with internal fixation using titanium screws. The femoral head vitality was evaluated with 99Tcm-MDP scintigraphy and scintimetry within 2 weeks postoperatively and by serial low field magnetic resonance imaging (MR). Two patients with reduced radionuclide uptake (femoral head ratio <1.0) developed radiographic signs of femoral head necrosis. MR disclosed the definite area of the necrosis at 2 and 12 months after fracture, respectively. In three of the patients with a high scintimetric uptake (femoral head ratio ≥1.0), MR revealed a focal decrease of the signal intensity in the femoral head or neck at 2, 3 and 7 months after fracture, respectively. The radiographs in one of these patients were normal at 7 months after fracture. The second one showed signs of necrosis at 16 months and the last one developed delayed/non-union. With a non-ferromagnetic osteosynthesis the healing course after femoral neck fracture can be studied with low field MR equipment without disturbing artifacts. The time period between ischaemia and definite abnormalities on MR may embrace several months.

MRI evaluation of collapsed femoral heads in patients 60 years old or older: Differentiation of subchondral insufficiency fracture from osteonecrosis of the femoral head

OBJECTIVE

The purpose of this article is to verify the hypothesis that osteonecrosis and subchondral insufficiency fracture of the femoral head can be differentiated on the basis of their appearance on MRI.

SUBJECTS AND METHODS

Between May 1998 and February 2009, we reviewed 30 consecutive hips in 30 patients, 60 years old or older at the time of onset of hip pain, with radiologic evidence of subchondral collapse of the femoral head and with both MR images and histologic results available. Both clinical and radiologic appearances were investigated. The patients were divided into two groups according to the shape of low-intensity bands on T1-weighted images. The first group showed concavity of the articular surface, which is characteristic of osteonecrosis, and the second group showed an irregular convexity of the articular surface, which is characteristic of subchondral insufficiency fracture.

RESULTS

Sixteen hips (53.3%) showed evidence of osteonecrosis, and 14 (46.7%) showed evidence of subchondral insufficiency fracture, which was consistent with the corresponding histopathologic diagnoses. In all cases of osteonecrosis, the patient had a history of either corticosteroid intake or alcohol abuse. Among patients with subchondral insufficiency fracture, the proportion of women was significantly higher than that among patients with osteonecrosis. A crescent sign (subchondral fracture) was present radiographically in about half of all cases in both groups.

CONCLUSION

The results of the present study suggest that the shape of the low-intensity band on MRI is useful for the differentiating subchondral insufficiency fracture from osteonecrosis. In addition, among osteoporotic elderly women without any history of corticosteroid intake or alcohol abuse, a diagnosis of subchondral insufficiency fracture should be considered.

MRI-based surgical simulation of transtrochanteric rotational osteotomy for femoral head osteonecrosis

Transtrochanteric rotational osteotomy (TRO) is one of the joint-preserving surgical treatments for osteonecrosis of the femoral head (ONFH). It can prevent collapse of the femoral head as necrotic lesions in the weight-bearing portion can be moved sufficiently to a less weight-bearing portion by anterior rotation, posterior rotation, or varus angulation. Patient selection and preoperative planning are important to determine indications for TRO. It has been reported that successful TRO requires at least 34% of the weight-bearing area supported by the intact part of the femoral head. However, this ratio is difficult to preoperatively quantify according to the rotation angle using conventional two-dimensional MR images or X-rays. Therefore, we developed a method of simulating TRO using three-dimensional (3D) models reconstructed from 3D MR images and applied it to serial patients with types C1 and C2 osteonecrosis at stage 1 or 2. The simulation visualized positional changes of the necrotic lesion in the weight-bearing area and enabled quantitation of the postoperative intact ratio. Our surgical simulation is useful for evaluating the postoperative intact ratio and for determining indications for TRO as well as the optimal angle of femoral head rotation and varus angulation.

Measurement of lesion area and volume by three-dimensional spoiled gradient-echo MR imaging in osteonecrosis of the femoral head

The purpose of this investigation is to evaluate the diagnostic ability of three-dimensional spoiled gradient-echo (3D SPGR) magnetic resonance (MR) imaging in cases of osteonecrosis of the femoral head (ONFH), and to determine the accuracy of 3D SPGR imaging in area and volume measurement of ONFH. T1-weighted spin-echo (SE) and 3D SPGR imaging were performed on 20 femoral heads obtained from patients with ONFH. After MR imaging, the femoral heads were cut parallel to the imaging plane and were evaluated histologically. Areas and volumes of necrotic lesions were measured with a computer program and the deviation between MR images and anatomical measurements was evaluated. A low signal intensity band on 3D SPGR MR images was observed in all femoral heads and corresponded histologically to repaired marrow with viable fibrous mesenchymal tissue. The area proximate to the low band area coincided with the necrotic region. Both area and volume measurements by T1-weighted SE and 3D SPGR images showed a strong correlation to histological measurements. The discrepancies between histological and imaging results were minimal in 3D SPGR imaging, especially at the anterior and posterior portions of the femoral head. Three-dimensional SPGR imaging provides more accurate measurements of the area and volume of a necrotic lesion than T1-weighted SE imaging.

Early MRI findings of rapidly destructive coxopathy

To diagnose rapidly destructive coxopathy (RDC) in its early stages and understand the pathomechanism of associated joint destruction, ten cases of RDC were followed by periodic MRI from onset of the disease. In the initial stage (stage 1) of RDC, when radiographs revealed slight narrowing of the joint space, a small subchondral area of low signal intensity was observed on T(1)-weighted images (T1WI) and inhomogeneous high intensity was observed on T(2)-weighted images (T2WI) in the antero-lateral portion of the femoral head. When radiographs showed obliteration of the joint space (stage 2), MRI revealed a diffuse area of low intensity on TIWI and high intensity on T2WI in the proximal femur, including the femoral neck and head, suggesting extensive bone marrow edema. The femoral head and acetabulum were aggressively destroyed (stage 3) in all cases 3 to 6 months after the diffuse abnormal pattern was observed on MRI. MRI in stage 3 cases showed low intensity areas on both T1WI and T2WI. RDC did not show the band-like pattern of low intensity on T1WI and high intensity on T2WI that typify MRI findings in cases of osteonecrosis. When joint space narrowing is observed radiographically, the diffuse abnormal pattern of low intensity on T1WI and high intensity on T2WI induced by a subchondral small lesion might be an early sign of RDC.

Changes on magnetic resonance images after traumatic avascular necrosis of the femoral head

SUMMARY

We describe two cases of avascular necrosis after traumatic fracture of the femoral neck. The size and signal intensity of the necrotic areas changed on follow-up magnetic resonance images. Magnetic resonance imaging is suitable for showing resolvable changes that radiographic study cannot demonstrate during the clinical course.

MRI evaluation of steroid- or alcohol-related osteonecrosis of the femoral condyle

We reviewed 30 patients (46 knees) with steroid- or alcohol-related osteonecrosis of the femoral condyle. Their average age was 35 (14-61) years and the mean observation time was 7 (3-16) years. The medio-lateral extent and the anterior-posterior (AP) location of the necrotic lesion were evaluated on T1-weighted MRI and related to the collapse of the condyle. The size of the lesion was classified into three categories on the mid-coronal MRI of the femoral condyle: there were 44 small, 20 medium, and 9 large lesions. The condyle was divided into 3 zones: anterior, middle, and posterior. The location of the lesion was evaluated on the mid-sagittal image. There were 7 anterior, 9 middle, 29 posterior, 14 middle and posterior and, in 14 cases, all 3 zones were involved. 44 small lesions did not collapse, while 6/20 medium lesions and 5/9 large lesions collapsed. No lesion involving only one zone collapsed, while 4/14 lesions involving the middle and posterior zones and 7/14 lesions involving all three zones progressed to collapse. 4/6 condyles with large necrotic lesions involving all three zones collapsed. We conclude that the extent of the necrotic lesion on both the mid-coronal and mid-sagittal planes is of importance for the prognosis of osteonecrosis of the femoral condyle.

Magnetic resonance imaging to detect avascular necrosis after open reduction and internal fixation of talar neck fractures

Twenty-one consecutive patients with displaced talar neck fractures (12 Hawkins type II, 9 Hawkins type III) were prospectively evaluated with magnetic resonance (MR) scans performed between 3 days and 12 months after surgery. All patients underwent open reduction and internal fixation with titanium screws, except two who underwent fixation with stainless steel implants that were subsequently removed. All patients had plain radiographs. We classified the scans as follows: type A, no abnormal signal changes in the body of the talus; type B, signal changes in less than 25% of the body; type C, signal changes in 25% to 50% of the body; and type D, signal changes in greater than 50% of the body. Plain anteroposterior radiographs correlated well with MR scans in patients with type D scans, but an inconsistent correlation was noted with lesser degrees of signal changes (types A-C), with the MR scans being more accurate in displaying the volume of avascular bone. Scans obtained less than 3 weeks after injury were not helpful in assessing for avascular necrosis. We found that high-quality MR images of the talus were consistently obtained in the presence of titanium screws in contrast to images obtained with stainless steel implants. We use titanium screws in all talar neck fracture repairs, because they permit high-quality MR images. We believe that further study of patients with Hawkins type III fractures and Hawkins type II fractures with equivocal radiographic evidence of avascular necrosis is warranted to try to identify those patients at risk for collapse and perhaps to guide weightbearing recommendations.

Magnetic resonance imaging of tibial shaft fracture repair

Magnetic resonance imaging (MRI) of normal fracture repair was evaluated in six randomly chosen adult patients with solitary, closed fractures of the tibial shaft by obtaining serial MRI scans until union of the fracture. The mean time to union was 14.3 weeks. Ultralow-field 0.02-Tesla magnet equipment was used. The MRI scans showed a characteristic pattern of events common for all the patients studied and compatible with the recognized histomorphology of fracture repair. The intramedullary cavity demonstrated a marked decrease in the signal intensity. In the soft tissues surrounding the fracture the initially evenly high signal intensity gradually developed a granular appearance with embedded low-intensity nodules. These nodules corresponded to the first areas to become mineralized, as could be seen on plain radiographs several weeks later. The question of whether MRI renders it possible to predict delayed union calls for continued investigations.