Osteochondral lesions at the ankle frequently occur after traumatic injuries [
In order to visualize osteochondral lesions at the ankle and to decide on the treatment strategy and ideal surgical approach, cross-sectional imaging is required. Usually conventional magnetic resonance imaging (MRI) is considered as the modality of choice [
CT arthrography (CTA) is a well-established cross-sectional imaging technique for detection of osteochondral lesions in different joints. Also postoperatively, it allows more specific evaluation of equivocal or difficult lesions [
Therefore, the purpose of this study was to determine the diagnostic value and the reliability of CTA at the ankle in the evaluation of osteochondral defects in comparison to conventional MRI. We hypothesized that assessment of osteochondral defects at the ankle is more reliable on CTA than on MRI and that CTA of the ankle has a high diagnostic relevance in order to determine the surgical approach.
The work was conducted in accordance with the Declaration of Helsinki. The study was approved by our institutional review board. The requirement for informed consent was waived. The data of patients referred for multidetector CT of the ankle at our hospital between July 2004 and July 2015 were evaluated retrospectively. Inclusion criteria for this study were CTA of the ankle performed at our institution and an available MRI examination of the same ankle performed within 12 months prior to or 3 months after the CTA (
Intra-articular injection of contrast media was performed under fluoroscopic guidance by means of a medial approach [
CT images were acquired by using either a clinical whole-body 256-row CT scanner (Philips Brilliance iCT, Philips Medical System DMC GmbH, Hamburg, Germany) or a clinical 128-row Siemens SOMATOM Definition AS (Siemens Healthcare, Erlangen, Germany). Scan parameters were as follows: tube voltage, 120 kVp; tube load, 250 mAs; interpolated voxel size, 300 × 300 × 600
MR imaging protocols varied, since some of the patients were referred to the sports orthopedics department with existing MR examinations. MR imaging was predominantly performed on 1.5 T systems (Magnetom Avanto, Siemens AG, Erlangen, Germany) or 3 T systems (e.g., Siemens Verio, Global Siemens Healthcare Headquarters, Siemens AG, Erlangen, Germany). Siemens Head/Neck 4-channel coils were used (Global Siemens Healthcare Headquarters, Siemens AG, Erlangen, Germany). Exemplary MR imaging parameters at 3 T are given in Table
Exemplary 3 T MR imaging parameters.
Sequence | 2D IM-w TSE | 2D T2-w TSE | 2D IM-w TSE | 2D T1-w TSE |
---|---|---|---|---|
Additional features | FS, BLADE | FS, BLADE | DRIVE | |
Plane | Sagittal | Transverse | Coronal | Coronal |
Echo time (TE; ms) | 46 | 77 | 47 | 13 |
Repetition time (TR; ms) | 4500 | 5360 | 4500 | 1000 |
Field of view (FOV; mm) | 140 | 120 | 140 | 140 |
Slice thickness (mm) | 3 | 3 | 3 | 3 |
In-plane resolution (mm2) | 0.44 × 0.44 | 0.38 × 0.38 | 0.36 × 0.36 | 0.36 × 0.36 |
Flip angle (°) | 90° | 90° | 90° | 90° |
Number of slices | 22 | 25 | 24 | 22 |
Receiver bandwidth (Hz/ pixel) | 182 | 147 | 181 | 171 |
Echo train length | 9 | 15 | 9 | 3 |
Phase encoding direction | AP | RL | RL | RL |
Distance factor (%) | 10 | 20 | 10 | 10 |
Acquisition time (min) | 5 : 08 | 3 : 57 | 5 : 48 | 4 : 04 |
FOV: field of view; w: weighted; TSE: turbo spin echo; IM: intermediate; fs: fat saturated; BLADE: motion correction with radial blades; DRIVE pulse: driven equilibrium pulse.
MR images were transferred on Picture Archiving Communication System (PACS) workstations (Easy Vision, Philips, Best, Netherlands) and were evaluated semiquantitatively by two musculoskeletal radiologists independently (Jan S. Kirschke and Pia M. Jungmann). Both observers evaluated all images in a randomized order; MR evaluation was performed before CTA evaluation. For cartilage evaluation and evaluation of the subchondral bone on MRI, primarily IM-w sequences and T1-w sequences were considered.
Osteochondral lesions at the tibia and talus were scored on CTA and MRI including the parameters cartilage defect depth, cartilage defect size, bony defect depth, and bony defect size. Cartilage defect depth was scored as follows: (i) no defect, (ii) partial thickness defect, and (iii) full thickness defect. Cartilage defect size was determined by measuring the largest cartilage defect diameter: one measurement was performed for full thickness parts of the lesion and a second measurement for the entire cartilage lesion. Defect size was scored as follows: no defect,
All images were assessed by one specialized orthopedic surgeon (Sepp Braun) in consensus with one musculoskeletal radiologist (Pia M. Jungmann). Changes in the therapeutical or surgical approach resulting from the additional information gained from CTA were noted as follows: (i) no additional information, (ii) influence of CTA findings on therapeutical strategy or surgical approach, and (iii) no influence on the therapeutical strategy but important information and confirmation of the chosen strategy.
By means of digital medical records, information on patient demographics, indication for CTA, and information on previous surgeries were retrieved. Surgical reports were analyzed retrospectively regarding description of cartilage integrity. Presence of cartilage defects was noted. Due to missing information on osseous involvement this parameter was not included in the analyses.
Statistical processing was performed with SPSS version 17.0 (SPSS Institute, Chicago, IL, USA) (Pia M. Jungmann and Thomas Baum). Frequencies of subscores in our analyzed cohort were calculated. Means
Between July 2004 and July 2015,
In all cases, the CTA was performed in order to detect or visualize chondral or osteochondral defects. Specific indications for CTA, previous surgeries, and surgeries after CTA are given in Table
Detailed specifications of the indications for CTA and surgeries.
A: indication | Number of cases ( |
---|---|
OCL | |
OCL | |
Subchondral cyst or ganglia | |
Subchondral BMEL | |
After cartilage repair surgery | |
Bone necrosis/infarct | |
| |
No findings on MRI but persistent complaints | |
| |
B: previous surgery | Number of cases ( |
| |
Osteochondral transplantation | |
Autologous chondrocyte implantation | |
Biomatrix implantation | |
Retrograde drilling | |
Curettage of ganglion/cyst and spongiosa graft | |
Surgical treatment of ankle fractures | |
Tumor surgery (giant cell tumor) | |
Arthroscopy (debridement, shaving) | |
| |
C: surgery after CTA | Number of cases ( |
| |
Osteochondral transplantation | |
Microfracturing/antegrade drilling | |
Spongiosa graft | |
Only chondral and osseous debridement | |
Metal implant removal | |
Syndesmosis reconstruction | |
A: indications including clinical queries (
OCL: osteochondral lesion; BMEL: bone marrow edema-like lesion.
CTA for detection of full thickness cartilage lesions at the ankle in the presence of subchondral cysts. On MRI presence of full thickness cartilage defects remain unclear. In case (a) CTA demonstrates incongruence of the cartilage surface but no full thickness defect. In case (b) CTA demonstrated a fissural full thickness cartilage defect, allowing communication between intra-articular synovial fluid and subchondral cyst.
Divergent results for presence of full thickness cartilage defects on MRI and CTA. In case (a) a full thickness cartilage defect at the talus was suggested on MRI; CTA revealed depression of the cartilage surface but no full thickness defect. In case (b) no cartilage defect was suggested on MRI but due to massive bone marrow edema at the tibia CTA was performed and revealed a fissural full thickness defect at the tibia.
Considering intraoperative findings as standard of reference. CTA showed improved sensitivity compared to MRI. Exemplarily, in this subject with an osteochondral defect at the medial talus only BMEL but no cartilage defect was depicted on MRI (a). The full thickness cartilage defect revealed by CTA (b) was confirmed with a probe intraoperatively (c).
Different presentations of osteochondral defects. (a) Patient with suspicion of an osteochondral defect on MRI but no defect on CTA. (b) Patient with an osteochondral defect without loosening (no subsequent surgery). (c) Patient with similar findings on MRI as in (b); however on CTA contrast enhanced fluid surrounds the osteochondral fragment indicating instability and the patient had to undergo subsequent surgery.
Frequencies of lesions in the assessed cohort are given in Table
Frequencies of osteochondral lesions on CTA and MRI.
CTA ( | MRI ( | |||
---|---|---|---|---|
Talus | Tibia | Talus | Tibia | |
| | | | |
| ||||
Total | | | | |
Fissure | | | | |
Small | | | | |
Medium | | | | |
Large | | | | |
Extensive | | | | |
| ||||
Total | | | | |
Fissure | | | | |
Small | | | | |
Medium | | | | |
Large | | | | |
Extensive | | | | |
Kappa values for interobserver reliability are presented in Table
Cohen’s kappa values for interobserver reliability.
Parameter | CTA | MRI |
---|---|---|
Interobserver agreement | Interobserver agreement | |
| ||
Presence | 0.72 | 0.55 |
Size | 0.47 | 0.55 |
| ||
Presence | 0.82 | 0.55 |
Size | 0.48 | 0.50 |
| ||
Presence | 0.70 | 0.78 |
Depth | 0.60 | 0.75 |
Size | 0.48 | 0.63 |
Considering CTA as standard of reference, MRI was able to visualize 83.1% of cartilage defects (observer 2, 67.0%; specificity, 68.1% and 85.2%); 54.2% of full thickness defects were depicted (observer 2, 47.6%; specificity, 80.2% and 86.5%). MRI was able to visualize 63.6% of defects of the subchondral bone. Considering surgical reports as standard of reference, sensitivity for detection of cartilage lesions was better for CTA than for MRI (Figure
In 12/79 cases (15.4%) CTA findings changed the further clinical management of the patient. In
The present study demonstrated the important diagnostic value of CTA with respect to osteochondral lesions at the ankle joint, particularly in case of full thickness cartilage lesions. Only about half of full thickness cartilage lesions detected on CTA were depicted on MRI. Interobserver agreement for detection of cartilage lesions and for semiquantitative ICRS and WORMS scores was superior for CTA as compared to MRI. Sensitivity for detection of intraoperatively confirmed cartilage lesions was better for CTA than for MRI. CTA findings were considered beneficial for treatment decisions. These results suggest that in indicated cases CTA of the ankle remains an extremely helpful cross-sectional imaging tool for detection, visualization, and scoring of chondral and osteochondral lesions at the ankle joint.
While there are many cohort studies on cross-sectional imaging of early knee osteoarthritis, there is a lack of imaging studies on the ankle joint. Detection of osteochondral defects at the ankle is clinically of particular importance, since these predispose for osteoarthritis [
Besides MRI, CTA has been used for detection of osteochondral lesions in many joints [
Since BMEL may only be depicted properly on MRI but frequently correlate with patients symptoms, this underlines the value of MRI in this context. In our study, BMEL frequently indicated fissural cartilage defects on CTA (Figure
Cross-sectional imaging at the ankle is required for osteochondral defects visualization and staging not only prior to surgery but also after surgery [
Another important indication for CTA was presence of subchondral cysts. On MRI it was hard or impossible to detect fissural defects that allow communication between intra-articular synovial fluid and cyst. In 66% of cases with subchondral cysts, fissures were detected on CTA (Figure
The major limitation of the present study is the retrospective design. Due to the retrospective design, there was no standardized reporting of osteochondral defects in the surgical report. Supposedly, some minor cartilage lesions, in particular at the opposing compartment, may not have been described in surgical reports since no surgical treatment was required. This may account for the relatively low specificity of both CTA and MRI, using surgical reports as standard of reference. The involvement of the subchondral bone was reported very inconsistently in the surgical reports and was therefore not included in the present study. Only indicated CTAs were performed and included in this study and indications varied. In most cases, CTA was indicated because MRI findings were inconclusive. This may have impacted the results. However, we think that this is an appropriate clinical practice. In case of indicated cases, important additional diagnostic information may be gained via CTA with respect to osteochondral lesions. In
In summary, this study underlined the important diagnostic value of CTA at the ankle. CTA showed improved sensitivity and reliability regarding detection of osteochondral lesions at the ankle compared with conventional MRI. CTA findings may influence treatment strategies and surgical decisions in many cases. In conclusion, in the appropriate clinical context, CTA is particularly helpful in patients with suspicion of osteochondral lesions at the ankle.
Sepp Braun and Andreas B. Imhoff are consultants of Arthrex Inc. (Naples, FL, USA).
All the authors except Sepp Braun and Andreas B. Imhoff declare that there is no conflict of interests regarding the publication of this paper.
Jan S. Kirschke and Sepp Braun contributed equally to this work.
This work was supported by Grants of the Deutsche Forschungsgemeinschaft (DFG BA 4085/2-1 and BA 4906/1-1), by Grants of the European Research Council ERC-StG-2014 637164 and by the Commission for Clinical Research, Technische Universität München (TUM), TUM School of Medicine, Munich, Germany (Project no. 8762152), and by Technische Universität München, Munich, Germany, within the funding program Open Access Publishing.