Fluid-fluid level in an intraosseous ganglion

Fluid-fluid Levels in Musculoskeletal Tumor Imaging

Fluid-fluid levels result from the separation of two fluids of differing densities within a cavernous space with the boundary between the two layers running in a horizontal plane at 90 degrees to the direction of gravity. Magnetic resonance imaging is the most sensitive imaging modality to identify fluid-fluid levels. Although the most common bone lesions containing fluid-fluid levels are aneurysmal bone cyst and telangiectatic osteosarcoma, fluid-fluid levels can be observed in a wide variety of bone and soft tissue lesions. Therefore, fluid-fluid levels cannot be considered diagnostic of any particular type of tumor and the diagnosis should be made on the basis of other clinical, radiological and pathological findings. This article summarizes the pathophysiology and imaging characteristics of fluid-fluid levels and discusses the differential diagnosis of tumors with this imaging sign.

The role of needle biopsy for focal bone lesions with complete fluid-fluid levels on magnetic resonance imaging

OBJECTIVE

To assess the value of image-guided needle biopsy of bone lesions completely filled with fluid-fluid levels (FFLs) on magnetic resonance imaging (MRI) and the safety of primary surgical curettage.

MATERIALS AND METHODS

The radiology database was searched for all reports containing "fluid level" from 1998 to 2011 and the imaging was reviewed retrospectively. Inclusion criteria were patients with bone lesions completely filled with FFLs on MRI (defined as FFLs on every axial and/or sagittal T2-weighted or Short Tau Inversion Recovery (STIR) sequence). The pathology database was then reviewed for the outcome of needle biopsy (n=14) and for the outcome of surgical curettage, either post-biopsy or primary (n=52).

RESULTS

There were 53 patients (mean age 18 years; M=34, F=19). Fourteen patients underwent percutaneous needle biopsy, which was diagnostic in five (36 %) and non-diagnostic in nine (64 %). Fifty-two patients had surgical curettage/resection, which was diagnostic in 50 (96 %) and non-diagnostic in two (4 %). All lesions were benign; 78 % were aneurysmal bone cysts (ABC), 8 % were lesions with ABC change, and 14 % were simple bone cysts.

CONCLUSIONS

Our results suggest that patients with bone lesions completely filled with FFLs on MRI are almost certain to be benign, provided that the clinical and radiological features are not atypical. Percutaneous needle biopsy in such cases is unlikely to be of value and these lesions can be safely managed with primary surgical curettage.

Fluid-fluid levels in bone neoplasms: variation of T1-weighted signal intensity of the superior to inferior layers--diagnostic significance on magnetic resonance imaging

The diagnostic relevance of the relative T1-weighted (T1W) and T2-weighted (T2W)/short tau inversion recovery (STIR) MRI signal intensity characteristics of the superior to inferior fluid layers within fluid-fluid levels (FFLs) found in bone tumours was investigated. A retrospective analysis was performed of MRI studies of 2,568 patients presenting with a suspected bone tumour over an 8-year period. Final diagnosis was made by biopsy/surgical resection or characteristic imaging/clinical findings. Subjects were divided by the absence/presence of FFLs and benign/malignant histology. Cases with FFLs were sub-categorised by the relative signal intensity of the superior/inferior layer as high/low or low/high on T1W and T2W/STIR sequences. Out of the total of 2,568 cases, 214 (8.3%, CI 7.3-9.5%) had FFLs and 2,354 (91.7%, CI 90.5-92.7%) had no FFLs. All 214 cases with FFLs had T2W/STIR sequences available, all demonstrating high/low signal intensity characteristics; 135/214 (63.1%, CI 56.2-69.6%) were benign and 79/214 (36.9%, CI 30.4-43.8%) were malignant. Out of the 214 patients, 151 had T1W sequences performed; 52 showed high/low signal intensity, of which 30 (57.7%, CI 34.2-71.3%) were benign and 22 (42.3%, CI 28.7-56.8%) were malignant (P = 0.06 compared with no FFL group); 50 showed low/high signal intensity, of which 40 (80%, CI 66.3-90.0%) were benign and ten (20%, CI 10.0-33.7%) were malignant (P = 0.0000, compared with the no FFL group). The low/high and high/low groups had a significantly greater proportion of benign and malignant lesions, respectively (P = 0.015). In conclusion, all FFLs showed high/low signal intensity characteristics on T2W/STIR sequences. Low/high signal on T1W was significantly associated with benign disease. Malignancy may occur slightly more frequently with high/low signal on T1W.

Musculoskeletal Lesions With Fluid-Fluid Level: A Pictorial Essay

A fluid-fluid level was identified in 11.2% of focal lesions of bone. Fluid-fluid levels are observed on cross-sectional imaging with either computed tomography (CT) or magnetic resonance (MR) imaging. They become apparent when a fluid collection containing substances of different density is allowed to settle, and when the plane of imaging is perpendicular to the fluid level. For instance, within a collection of blood, the cellular components will settle dependently, with the lower density plasma forming a layer superiorly. The difference in the density of these layers can be observed on CT imaging. With MR imaging, these layers will have different signal characteristics, allowing for visualization of the fluid-fluid level. The presence of fluid-fluid levels within a musculoskeletal lesion is an important finding, which can significantly aid in the differential diagnosis. This finding can be observed in a wide variety of lesions: osseous and soft tissue masses, neoplastic or nonneoplastic lesions, malignant or benign neoplasms, and primary or metastatic malignancies. When a fluid-fluid level is detected, in conjunction with clinical history, the differential diagnosis for a lesion can often be limited to a few choices. For this reason, it is important to be aware of the multiple lesions that can produce fluid-fluid levels, as well as their differentiating characteristics and typical presentations. We will review both osseous and soft tissue lesions, focusing on their imaging characteristics and other important findings.

Arthroscopic debridement and grafting of an intraosseous talar ganglion

We report the case of a 41-year-old man with right ankle pain and swelling who had an intraosseous talar ganglion in the medial part of talar dome. A surgical procedure was performed using the 3-portal arthroscopic approach. The softened chondral surface was removed and the content of the cyst was discharged arthroscopically. The sclerotic rim was abraded until the bleeding spongious layer was seen. A grafting procedure was also performed arthroscopically. A trocar was introduced into the defect from the superomedial portal. Autografts were impacted using a cylindrical rod through the trocar into the defect. The clinical and radiologic results at the 1-year follow-up were satisfactory. We encountered no complications postoperatively. We conclude that arthroscopic debridement and grafting of an intraosseous ganglion adjacent to the articular surface may be a better option compared with open surgery.

The prevalence and diagnostic significance of fluid-fluid levels in focal lesions of bone

OBJECTIVE

To determine the prevalence and diagnostic significance of fluid-fluid levels (FFLs) in focal bone lesions.

DESIGN AND PATIENTS

Clinical and radiological details of 738 consecutive patients referred with focal lesions of bone and who had undergone MRI were reviewed. FFLs were identified in 83 (11.2%). The proportion of the lesion occupied by FFLs was estimated, based on imaging in all available planes, as <1/3, 1/3-2/3, >2/3 but not the entire lesion, and complete. The degree of FFL change in each lesion was correlated with the final diagnosis, which was either histological (n=80) or clinicoradiological (n=3). There were 31 female and 52 male patients, mean age 25.5 years (range 5-83 years).

RESULTS

Histology revealed 46 benign, 32 malignant and 2 non-neoplastic lesions. A clinicoradiological diagnosis was made in the 3 lesions without histology: 2 were benign (simple bone cyst and intraosseous lipoma) and 1 malignant (a metastasis). Malignant neoplasms commonly showed FFLs which occupied <1/3 of the entire lesion (n=22/32, 68.8%), and 50% of all the lesions in this group were conventional intramedullary osteosarcomas (n=16). With increasing FFL change, malignancy became less frequent: with >2/3 (but incomplete) FFL change, 81% (n=13/16) of tumours were benign. If the entire tumour showed FFL change, the histology was benign in 100% (n=11).

CONCLUSIONS

The extent of FFLs within a focal bone lesion appears to be inversely related to the degree of malignancy. If at least 2/3 of the lesion shows FFL change, 89% of diagnoses are benign.