|ECR 2019 / C-0765||
|All-inside meniscal repair on MRI. Suture tracks and anchors, new findings in the evaluation of meniscal repair.|
Findings and procedure details
Magnetic resonance imaging (MRI) has demonstrated high sensibility and specificity in the diagnosis of meniscal lesions, however, accurate identification between normal cicatrization processes and re-tear is still challenging . Accurate assessment of the postoperative knee on magnetic resonance imaging (MRI) requires a proper understanding of the procedures performed, the normal postoperative imaging appearance as well as the potential complications, and their imaging appearance . In this regard, the evaluation of meniscal suture tracks and anchors location has proven in our hands to be a key element in the characterization of the operated meniscus. In our knowledge, none of these findings has been described in the medical literature.
In meniscus repaired with all-inside suture systems, suture tracks ( Fig. 4 ) can be routinely visualized in conventional magnetic resonance imaging (MRI) protocols. They can be identified and followed in all pulse sequences, but better identified in PD-FS sequences, being observed in the short and long axis as dot-like or linear images of intermediate-high signal respectively ( Fig. 5 ), in the thickness of the meniscal tissue, which can be followed on successive images from the articular surface to the periphery of the meniscus ( Fig. 6 ).
On conventional protocols, suture tracks can be viewed and evaluated routinely, however, their identification and the ability to tracking them through the meniscus are done more adequately when including DP-FS sequences with thin slices (1 mm) and imaging in 3T magnetic resonance imaging (MRI) ( Fig. 7 ).
In daily practice, different configurations of the suture tracks can be observed when evaluating images from patients with a history of all-inside meniscal repair. The suture tracks can be identified passing through the tear as expected, but also they can be seen passing through and below the tear or both tracks passing outside the plane of the tear, exiting the meniscal surface proximal to it ( Fig. 8 ).
As described in suture tracks, the peripheral anchors of the all-inside meniscal repair suture systems can also be evaluated with magnetic resonance imaging (MRI). The anchors are seen as small structures of low signal intensity in all pulse sequences, with a dot-like shape when visualized on the short axis and with linear "stick-like" morphology on the long axis ( Fig. 9 ).
These anchors are small (few millimeters), so their visualization is subject to magnetic resonance slices passing through them, which depends significantly on the slice thickness of our magnetic resonance imaging (MRI) protocols. However, in our experience, they can be routinely identified in post-surgical knees in conventional protocols.
On this regard, its identification is much favored by including pulse sequences with thin slices (1 mm), especially DP-FS sequences, either in coronal, sagittal or axial planes, depending on the acquisition times and the location of the repair in the meniscus. Also, 3T magnetic resonance imaging (MRI) substantially improves its evaluation. Under these conditions, they can be identified in several successive images, and their location can be precisely located ( Fig. 10 ).
In our center, some orthopedic surgeons perform early magnetic resonance imaging (MRI) controls on patients with anterior cruciate ligament reconstruction (ACLR), approximately 3 months after surgery, many of them concomitantly with meniscal suture. In these early examinations, small peripheral para meniscal cysts are often seen in patients with a history of all-inside meniscal repair ( Fig. 11 ). By evaluating these small cysts in greater detail, it can often be seen that they surround the suture anchors and assist in their identification ( Fig. 12, Fig. 13 and Fig. 14 ).
In magnetic resonance imaging (MRI) with intra-articular contrast, contrast filtration can be seen towards the cysts filling them, making identification of the anchors more evident, suggesting the extension of joint fluid filtering through the suture tracks towards the anchors ( Fig. 15 ).
In later controls (6-8 months) the cysts often disappear, leaving only the anchors visible ( Fig. 16 ). These findings suggest closure of the opening possibly by the process of synovialization of the meniscal surface, with subsequent reabsorption of the peri-anchor fluid.
It is the author's impression that the cysts that persist over time are those associated with a failure in meniscal healing or the development of a new tear pattern ( Fig. 17 ), this could be further evaluated in future researches.
INTRAMENISCAL ANCHORS AND OTHER LOCATIONS:
The correct placement of the suture anchors it is at the level of the meniscus periphery or joint capsule.
The all-inside meniscal suture systems use a ruler to measure and predict the area of anchor placement, usually between 14-16 mm depth of penetration, to avoid possible damage of neurovascular structures. Occasionally, the penetration may be insufficient or, at the moment of applying traction to the suture, migration of the implant may occur ( Fig. 18 ). Therefore, the anchors may occasionally be found in a purely intra-meniscal location ( Fig. 19 and Fig. 20 ) or even within the plane of the tear ( Fig. 21 ). When this happens, peri anchor cysts within the meniscus may occur ( Fig. 22 ). We have also seen the development of intrasubstance cleavage with the intra-meniscal migration of the implants ( Fig. 23 ).
On the other hand, if penetration is excessive, the sutures and anchors can be placed in the periarticular soft tissues, which can generate a foreign body reaction ( Fig. 24 ). These unexpected findings can be evaluated with magnetic resonance imaging (MRI).
Interestingly, we may even be able to locate these anchors with ultrasound when they are within reach ( Fig. 25 ).
The ability to identify anchors as well as the different configurations of the suture tracks through the meniscus, allows us to evaluate the placement of the sutures indirectly. Their identification could have importance in the evaluation of its stabilizing function that requires a circumferential compression of the tear. The identification of the correct or incorrect positioning of the sutures and their respective anchoring using magnetic resonance imaging (MRI) can be an essential additional aid when evaluating the signal intensity of the repair meniscal tear when trying to determine the healing ( Fig. 26 ).
TEAR PATTERNS ASSOCIATED TO THE USE OF ALL-INSIDE MENISCAL SUTURES
As previously discussed, different configurations of the meniscal sutures can be performed with the all-inside meniscal repair systems, classically with vertical and horizontal suture dispositions, being the vertical suture the first choice for its better capacity to exert tension on the tear.
One of the roles of magnetic resonance imaging (MRI) in the evaluation of patients with meniscal suture is to determine the healing of the repaired meniscal tear. However, new tear patterns of these repaired meniscuses can occur.
We have seen the future development of tear patterns other than the initial lesion, which seems to be directly related to the repair technique.
RADIAL TEARS IN VERTICAL SUTURE:
It has been described that menisci with a history of partial meniscectomies have a higher risk of developing radial tears, but the development of these tears directly related by the suture technique in repaired menisci has not been described.
In the case of all-inside meniscal suture systems with vertical sutures, different essential elements must be taken into consideration.
The first of these is the caliber of the cannula responsible for delivering the anchor and suture, which is of a larger caliber than in the other classic meniscal suture techniques (inside-out and outside-in), which makes it more traumatic on the meniscus. Also, by having a vertical arrangement, the two suture tracks are aligned on the same radial axis on the meniscus. Moreover, from the technical point of view, if too much tension is exerted on the suture when tightening the knot, a cutting-laceration effect on the meniscus may occur.
These tears have a classic appearance, with the exception that if they are incomplete and starting to develop without separation of the segments, we could be capable of seeing their development originated from the suture tracks extending towards the femoral and tibial surface of the meniscus ( Fig. 29 ).
They can also progress to a complete tear with the involvement of the peripheral rim and the separation of the segments. The comparison with the previous studies may help us to suspect the development of these tears from the suture tracks ( Fig. 30 ), although this distinction will probably not be of greater importance at that time.
COMPLEX TEAR / HORIZONTAL FLAP IN HORIZONTAL SUTURE:
Another pattern of tear that we have been able to observe in patients with all-inside meniscal suture usually occurs in those where a horizontal configuration of the sutures had been made. In these meniscuses, it is not uncommon to find in magnetic resonance imaging (MRI) controls the appearance of intrasubstance cleavages and occasionally tears that adopt a complex morphology with displaced horizontal flap component ( Fig. 31 ). When comparing in detail with previous studies, the horizontal flap seems to develop from the suture tracks, being the starting point of the tear ( Fig. 32 and Fig. 33 ).