The distribution in joint recesses and adjacent synovial compartments of loose bodies determined on MR and CT arthrographies of ankle joint

Abstract

Loose bodies (LBs) are intraarticular free bodies that result from various pathological processes and cause synovial inflammation. Timely and complete identification of LBs is important for appropriate treatment and prevention of possible complications such as osteoarthritis. LBs in the ankle joint can reach all the compartments that are adjacent to the joint via physiological or pathological connections. The presence, localisation, and number of LBs in the ankle joint and adjacent synovial compartments can be optimally evaluated using high-resolution magnetic resonance arthrography (MRA) and computed tomography arthrography (CTA). On this review article, we aimed to determine the LB location and distribution using high-resolution MRA and CTA of the ankle joint, and to demonstrate that it may be used as a complementary examination to guide interventional arthroscopy in difficult-to-reach areas during treatment.

Advances in knowledge

Loose bodies (LBs) are intraarticular free bodies and may cause synovial inflammation.

Accurate and complete determination of the number and location of LBs before surgery are very important for effective treatment.

The location, number and distribution of LBs in the ankle joint may be determined successfully by high-resolution magnetic resonance arthrography (MRA) and computed tomography arthrography (CTA).

For this purpose, MRA and CTA may increase the diagnostic and therapeutic success of the arthroscopy.

Introduction

Loose bodies (LBs) or missing bodies are defined as intraarticular free bodies that result from various pathological processes. LBs can be considered to be both a result and an agent in osteoarthritis. Accurate and complete determination of the number and location of LBs before surgery is important for stopping this process and for effective treatment, especially in young patients.

LBs can reach all synovial cavities that are adjacent to the joint and even the tendon synovia via physiological or pathological connections. Further imaging methods may be required to evaluate these areas preoperatively. A conventional magnetic resonance imaging (MRI) is one of these methods. However, small LBs may be overlooked in the absence of adequate effusion. Arthrographic MR images are useful and valuable for evaluating osteochondral fractures and missing bodies. ^1,2

Causes of a failed MRI or magnetic resonance arthrography (MRA) including claustrophobia, obesity, metallic surgical instrumentation, inadequate cooperation and equipment failure are the main indications for a computed tomography arthrography (CTA). ³ Compared with MRI or MRA, CT arthrography is lower cost and requires a shorter procedure time. Moreover, because of its high spatial resolution and multiplanar capability, CTA is an effective imaging modality to detect chondral and osteochondral loose bodies.

We aim to determine the location and distribution of LBs using MRA and CTA of the ankle joint, and to demonstrate that high-resolution MRA and thin section CTA may be a complementary method to guide interventional arthroscopy in difficult-to-reach areas during treatment.

Injection technique

For ankle MRA examination, injections are performed by a radiologist on an outpatient basis using an ultrasonography system equipped with a broadband 7.5-MHz linear transducer. Sedation or premedication is not usually necessary. The injection procedure is performed using a 22 G needle via an anteromedial approach (Figure 1). Diluted contrast solution at a concentration of 1:200 is injected (0.1 ml contrast medium diluted in 20 ml normal saline). A volume of 4–5.5 ml gadolinium-based solution is injected until the ankle joint capsule is appropriately expanded.

Figure 1.

Illustration showing anteromedial injection technique using ualtrasonography guidance into the tibiotalar joint.

For CTA, 12-ml iodinated contrast material mixed with 8 ml of saline is injected with a 22-gauge needle into the ankle joint via the anteromedial approach using ultrasonography guidance. Diluted iodinated contrast material solution mixed with the gadolinium contrast agent can be performed immediately for CTA together with MRA examination without an additional injection.

Mr arthrography examination

In our clinic, MRA examinations are performed using a 1.5 or 3T MRI 10–15 min after ankle joint injection. Imaging was performed using a superficial coil in the supine position. In our ankle MRA protocol, there are single plane non-supressing turbo spin-echo (SE) T1W and three plane fat-sat turbo SE T1W image sequences. In addition, we perform fat-sat T1W three-dimensional (3D) volumetric interpolated breath-hold examination (VIBE) in all ankle MRA patients.

Ct arthrography examination

CTA indications of the ankle joint in our clinic are patients who have suspected chondral or osteochondral defect and intraarticular loose bodies. For ankle CTA examination, an anteroposterior projection scout image is obtained to determine the boundaries of the ankle joint. The scanning range is planned from the upper margin of the distal tibiofibular joint to the lower margin of the calcaneus. Thin section CT arthrogram scans are obtained using multidetector CT scanner.

Image analysis

In routine radiologic examination, we analyse on high-resolution monitors using an image archiving and communication system all CT and MR arthrogram images for detection of ankle LBs. LBs can be classified in 12 different anatomical areas based on their location (recesses, joints, and tendon synovia). Thin slice CTA and high-resolution MRA scans such as VIBE arthrography sequence can optimally determine size and number of LBs. The anatomical areas where LBs can be seen based on their location such as joint recesses, adjacent joint compartment, and neighbour tendon synovia are as follows (Figure 2):

1. Central anterior recesses of the tibiotalar joint;

2. Posterior recesses of the tibiotalar joint;

3. Anterolateral recess of the tibiotalar joint;

4. Anteromedial recess of the tibiotalar joint;

5. Central section of tibiotalar joint space (neighbourhood of talar dom);

6. Talocalcaneal joint space;

7. Talonavicular joint space;

8. Talocalcaneocuboid joint space;

9. Distal tibiofibular syndesmosis;

10. Tibialis posterior tendon synovium;

11. Peroneal tendon synovium; and

12. Flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendon synovium.

Figure 2.

Illustration showing anatomic distributions of LBs in and around the ankle joint. A = Anteromedial recess, B = Central anterior recess, C = Anterolateral recess, D = Distal tibiofibular syndesmosis, E = Posterior resess, F = Central section of tibiotalar joint space, G = Talocalcaneal joint space, H = Talocalcaneocuboid joint space, I = Talonavicular joint space, J = Flexor hallucis longus and flexor digitorum longus tendon synovium, K = Tibialis posterior tendon synovium, L = Peroneal tendon synovium. C: Cuboid, Cl: Calcaneus, F: Fibula, N: Navicula, T: Tibia, Tl: Talus, V. MT: Fifth metatars, AMR: Anteromedial recess, AR: Anterior recess, ALS: Anterolateral recess, TFS: Tibiofibular syndesmosis, PR: Posterior resess, TTJS: Tibiotalar joint space, TCJS: Talocalcaneal joint space, TCCJS: Talocalcaneocuboid joint space, TNJS: Talonavicular joint space, FHLR-FDLR: Flexor hallucis longus recess and flexor digitorum longus recess, TPR: Tibialis posterior recess, PLR-PBR: Peroneus longus recess and peroneus brevis recess.

LBs in the ankle joint may be more than two in different anatomic sites or more than one in the same anatomical area. In our practice, we mostly observe LBs in the central anterior recess (Figure 3), posterior recess (Figure 4), and anterolateral recess (Figure 5) of the ankle joint. Flexor hallucis longus tendon synovium is second common location after these recesses (Figure 6). Locations where the LBs are less common; the talocalcaneal joint (Figure 7), the talonavicular joint, the distal syndesmosis (Figure 8), the tibialis posterior tendon synovium, the talocalcaneocuboidal joint space (Figure 9), and the peroneal tendon synovium (Figure 10).

Figure 3.

Illustration (A), axial 3D VIBE MRA (B), and axial CTA (C) images show a loose body in the central anterior recess. AR: Anterior recess, Cl: Calcaneus, F: Fibula, LB: Loose body, Tl: Talus.

Figure 4.

Illustration (A), axial and sagittal 3D VIBE MR arthrographies (B and C), and sagittal CTA (D) images show loose body in the posterior recess. AR: Anterior recess, Cl: Calcaneus, F: Fibula, LB: Loose body, T: Tibia, Tl: Talus.

Figure 5.

Illustration (A), axial 3D VIBE MRA (B), and axial CTA (C) images show a loose body in the anterolateral recess. ALR: Anterolateral recess, Cl: Calcaneus, F: Fibula, LB: Loose body, Tl: Talus.

Figure 6.

Illustration (A), sagittal CTA (B), sagittal 3D VIBE MRA (C), and medial posteroinferior projection 3D volume rendering CTA (D) images show a loose body within the flexor hallucis longus tendon synovium. Cl: Calcaneus, FHLR-FDLR: Flexor hallucis longus recess and flexor digitorum longus recess, F: Fibula, LB: Loose body, N: Navicula, T: Tibia, Tl: Talus.

Figure 7.

Illustration (A), sagittal 3D VIBE MRA (B), and sagittal CTA (C) images show a loose body in the talocalcaneal joint space. Cl: Calcaneus, C: Cuboid, LB: Loose body, N: Navicula, TCJS: Talocalcaneal joint space, Tl: Talus T: Tibia.

Figure 8.

Illustration (A), axial 3D VIBE MRA (B), and axial CTA (C) images show a loose body in the distal syndesmosis. TFS: Tibiofibular syndesmosis, F: Fibula, LB: Loose body, T: Tibia.

Figure 9.

Illustration (A) and sagittal oblique 3D VIBE MRA (B) images show a loose body in the talocalcaneocuboid joint space. VIBE sequence reveals a medial talar dome osteochondral defect (OCD) as origin of the loose body. C: Cuboid bone, Cl: Calcaneus, LB: Loose body, N: Navicula, OCD: osteochondral defect, T: Tibia, TCCJS: Talocalcaneocuboid joint space, Tl: Talus.

Figure 10.

Illustration (A), sagittal oblique 3D VIBE MRA (B), axial CTA (C), and axial 3D VIBE MRA (D) images show a loose body within the peroneal tendon synovium. Cl: Calcaneus, F: Fibula, LB: Loose body, PLR-PBR: Peroneus longus recess and peroneus brevis recess, T: Tibia, Tl: Talus, V. MT: Fifth metatars.

Discussion and literature review

LBs may be osseous, chondral, or osteochondral. X-ray, CT, and MRI may be used for radiological diagnosis. However, there are cases where all these imaging methods are inadequate to identify LBs. For example, chondral LBs may not be identified by radiography or CT scan. Chondral LBs are recognised by intermediate or lower signal intensity on MRI in the fat suppressed proton density (PD) and T2W sequences. ⁴ Osseous LBs are observed as central brightened oval or round structures with peripheral hypointense rim on T1W images. Air bubbles may imitate LBs in MRA, but most of the air bubbles can be identified by their non-dependent location and typical appearance. ⁵ Ocassionally, simultaneous CTA may be required for correct diagnosis (Figure 11A–B).

Figure 11.

Sagittal oblique 3D VIBE MRA sequence (A) shows suspicious LB (red arrow) in the anterior recess of the tibiotalar joint. Sagittal CTA scan (B) reveals that this image is an air buble (blue arrow).

In patients who have difficulty in diagnosed by conventional MRI, arthrographic examinations can be a guide for the clinician. CTA is highly sensitive for detecting osseous LBs and for identifying free air delivery. However, the ionised radiation is a disadvantage. MRA may provide more information about the diagnosis and localisation of chondral LBs and LBs in neighbouring tendon synovia with higher soft tissue sensitivity. Moreover, MR arthrographic examination reveals the association between LBs and tibiotalar soft tissue impingement syndrome. ⁶

Because articular cartilage of the ankle joint is very thin, on conventional MRI assessment of osteochondral defects and intraarticular bodies is challenging. ⁷ A 3D fat-sat T1W VIBE MRA sequence allows multiplanar reconstruction using thinner image slices with a thickness of 0.6 mm, and provides perfect contrast for the bone structures and adjacent soft tissues on MRA examinations. ⁸ This high-resolution volumetric arthrography sequence can facilitate the diagnosis of osteochondral lesions and loose bodies. Multidetector CTA is an effective technique in demonstrating stability of osteochondral lesions, chondral or osteochondral fragments and articular surface defects. In the evaluation of hyaline cartilage lesions and intraarticular free fragments, CTA technique is superior to conventional MRI and MRA. ⁹ Other advantages of CTA in ankle joint pathologies include excellent spatial resolution, brief procedure time, multiplanar capability, and limited number of metal artefacts. Apart from these, high resolution MRA and thin slice CTA can also detected successfully very small LBs.

There is a 25% connection between the ankle joint and the FHL tendon sheath in the normal population. ^10–12 LBs, resulting from either degenerative osteoarthropathies or traumatic processes, can enter the tendon sheath synovia through this connection. In addition, LBs in tendon sheaths may be the result of tenosynovial chondromatosis, especially in the FHL tendon synovium. ^13,14 In our practice, we found that 10% of LBs were located in the ankle tendon sheath synovium, and most commonly in the FHL and FDL tendon sheath synovium, with a frequency of 8%.

The conservative treatment approach is the first choice in asymptomatic cases. However, arthroscopic removal of LBs is preferred in symptomatic cases. ¹⁵ Adequate and effective arthroscopic treatment without preoperative imaging of LBs, especially in a large number of small LBs, different locations, is difficult. In addition, locating the LBs before the procedure may determine the arthroscopic approach (anterior–posterior).

Conclusion

If LBs are not treated early, they may cause early osteoarthritis via damage to the joint surfaces and chronic symptoms. Accurate determination of the number and location of LBs is important to prevent early osteoarthritis, and for appropriate and early treatment. Determining the location, number and distribution of LBs using 3D high-resolution MRA or thin section multidetector CTA before an ankle arthroscopy may increase the diagnostic and therapeutic success of the interventional arthroscopy in difficult-to-reach areas during the treatment process.