Materials and methods
The original part of this poster exhibit is a direct comparison of MRI and CBCT arthrography of a cohort of 25 patients which a talar OCL.
All patients were referred for MRI imaging due to ankle pain.
Inclusion criteria for subsequent CBCT-arthrography imaging included absence of previous surgery and the presence of a talar dome lesion on MRI. Informed consent was given by all patients after extensive explanation of the imaging procedure of the CBCT-arthrographic examination.
CBCT-arthrographic examination was performed within 1 week to maximum 1 month following the MRI examination in order to avoid signification lesion progression between the 2 examinations.
All MR examinations were performed on a 1.5T system (Siemens,
Magnetom Aera Erlangen Germany). The imaging protocol included: sagittal,
axial and coronal fat-suppressed (FS) T2-WI (intermediate weighting),
coronal PD and axial T1-WI with a slice thickness of 3 mm.
The contrast used for the CBCT arthrographic examination was 10 cc Omnipaque 240mg I/ml diluted with 10 cc saline.
A mean volume of 13cc was intra-articularly injected by a 21 Gauche needle (BD Microlance 0.8mm x 50mm).
All CBCT arthrography examinations were performed on a New Tom 5G CBCT within 15 to 25 minutes after contrast injection.
The following parameters were analyzed on both MRI and CBCT-arthrography by one observer:
1.
The maximal depth of the lesion according to the modified Outerbridge classification for cartilage lesions of the ankle (see Table 4 ,
grade 0-4).
2.
The maximal size of the OCL (anteroposterior and mediolateral).
3.
Detachment : no,
partial or complete detachment.
4.
Presence of bone marrow edema on MRI or subchondral sclerosis on CBCT.
5.
Presence of cysts and their maximal size associated with the osteochondral lesion.
6.
Visualization of additional lesions in the talus or tibia.
Upstaging of the OCL on CBCT-arthrography (CBCT-A) was defined as an increase of at least one of the imaging parameters.
Results
Twenty five patients were included with a mean age of 43 (range of 9 – 68).
A slight majority presented with an OCL in the right talus (14 patients) versus 11 patients with left sided lesion.
Fig. 18 summarizes the depth of the cartilage lesion on MR versus CBCT-A In comparison to MRI, we notice an increase in the number of grade 4 lesions on CBCT-A.
A "down-to-bone" lesion clearly visualized on CBCT-A was underdiagnosed in ten cases based on the MRI images.
Only in two patients,
CBCT-A revealed a less extensive depth of the lesion.
The mean AP size of the OCL on MR was 9.4 mm with a mean ML size of 6.252 mm.
On CBCT,
the mean AP size of the OCL was 9.46 mm and a mean ML size of 6.268 mm.
The degree of detachment is represented in Fig. 19.
If we compare the numbers based on MR with the data from the CBCT images we see an increase in lesions with a complete detachment.
An accurate knowledge of the degree of detachment is key for the further therapy as it influences the choice of treatment.
On FS T2-WI images surrounding bone marrow edema was seen in 24 patients (95%).
Subchondral sclerosis,
often subtle, on CBCT was present in all patients (100%).
In nine patients subchondral cysts were present on MRI,
compared to 11 on CBCT-A.
The mean maximal size on MR was 7.6 mm versus 7.45 on CBCT-A.
On MRI,
additional lesions included OCL in the distal tibia which were present in six patients (grade 2 n=3 and grade 4 n=3).
These additional OCL in the distal tibia were confirmed on CBCT imaging. One grade 2 lesion showed a greater extent on CBCT-A and was subsequently classified as a grade 4 lesion (grade 2 n=2,
grade 4 n=4).
Overall comparison of staging of OCL on MRI compared to CBCT-A leads to an upstaging of the OCL in eleven cases.
Only in two cases CBCT-A visualized a less extensive osteochondral lesion or downstaging (Fig. 31 Fig. 32 Fig. 33 ) in comparison to the MR images.
Based on the combination of MRI and CBCT findings one alternative diagnosis of subchondral insufficiency fracture (Fig. 35 - Fig. 36) was made.