Tineke De Coninck

Open versus arthroscopic meniscus allograft transplantation: magnetic resonance imaging study of meniscal radial displacement

PURPOSE In this imaging study, the radial displacement of meniscal allograft transplants (MATs), inserted with 2 different techniques, namely open soft-tissue fixation and arthroscopic bone tunnel fixation, was compared 1 year postoperatively. METHODS In this study, 37 patients received MATs: 16 MATs (10 lateral and 6 medial) were inserted by an open soft-tissue technique (open MATs), whereas 21 MATs (14 lateral and 7 medial) were implanted by an arthroscopic bone tunnel procedure (arthroscopic MATs). Radial displacement, in millimeters, was evaluated 1 year postoperatively on 1.5-T magnetic resonance images. The number of MATs with radial displacement larger or smaller than 3 mm was determined. To compare radial displacement of open versus arthroscopic MATs, the Mann-Whitney U test was used. RESULTS The radial displacement of open lateral and medial MATs was significantly larger (all reported P < .02) than that of arthros-copic MATs. In all cases, both open and arthroscopic, the radial displacement of MATs was significantly larger (all reported P < .007) than that of normal menisci. Radial displacement of less than 3 mm was found in 0 of 6 patients with open medial MATs versus 6 of 7 patients with arthroscopic MATs and was found in 1 of 10 patients with open lateral MATs versus 4 of 14 patients with arthroscopic MATs. CONCLUSIONS The radial displacement of MATs arthroscopically inserted with bone tunnel fixation is significantly less than the radial displacement of MATs inserted with open soft-tissue fixation. In addition, normal menisci displace significantly less than meniscal allografts. The clinical importance of radial displacement remains to be determined. LEVEL OF EVIDENCE Level III, retrospective comparative study.

Two-Year Follow-up Study on Clinical and Radiological Outcomes of Polyurethane Meniscal Scaffolds

Background: Little is known about radial displacement (RD) of polyurethane (PU) scaffolds, intended for partial meniscus defect substitution; no data are available on whether rim thickness influences RD and whether RD correlates with clinical outcome scores. Hypotheses: The meniscus is not extruded preoperatively, but RD occurs after scaffold implantation. A thicker rim will limit RD, and there is no correlation between RD and clinical outcome. Study Design: Case series; Level of evidence, 4. Methods: Twenty-six patients were implanted with a PU scaffold (8 lateral, 18 medial). Radial displacement (mm) was evaluated on magnetic resonance images preoperatively and at 3 months, 1 year, and 2 years postoperatively. At each time point, it was determined whether a correlation existed between the rim and RD. Clinical outcome was determined using a visual analog scale (VAS) for pain as well as the Lysholm knee scoring scale, Knee Injury and Osteoarthritis Outcome Score (KOOS), and International Knee Documentation Committee (IKDC) score. Results: Radial displacement of lateral scaffolds was not significantly different (P = .178) either preoperatively (mean ± SD, 3.42 ± 0.99 mm) or at 3 months (4.82 ± 0.59 mm), 1 year (4.55 ± 0.87 mm), or 2 years postoperatively (4.10 ± 0.93 mm). No correlation was observed between the rim and lateral RD at all time points. Medial scaffold RD increased significantly (P < .001) from preoperative values (2.17 ± 0.84 mm) to those at 3 months (4.25 ± 0.89 mm), 1 year (4.43 ± 1.01 mm), and 2 years postoperatively (4.41 ± 0.96 mm). A strong negative correlation between medial RD and the rim was observed at all time points. There was no significant correlation between clinical outcome scores and RD, either preoperatively or postoperatively. Conclusion: This study demonstrated that limited medial meniscal RD was present preoperatively but increased by 2 mm after scaffold implantation. Lateral RD was also present preoperatively but did not increase after scaffold implantation. Importantly, a strong negative correlation was found between the rim and postoperative medial RD; a thicker rim limited RD. However, in the lateral compartment, rim thickness did not correlate with RD because RD was already strongly present preoperatively. Finally, no correlations were observed between scaffold RD and clinical outcome scores, either preoperatively or postoperatively.

In-vivo evaluation of the kinematic behavior of an artificial medial meniscus implant: A pilot study using open-MRI.

BACKGROUND In this pilot study we wanted to evaluate the kinematics of a knee implanted with an artificial polycarbonate-urethane meniscus device, designed for medial meniscus replacement. The static kinematic behavior of the implant was compared to the natural medial meniscus of the non-operated knee. A second goal was to evaluate the motion pattern, the radial displacement and the deformation of the meniscal implant. METHODS Three patients with a polycarbonate-urethane implant were included in this prospective study. An open-MRI was used to track the location of the implant during static weight-bearing conditions, within a range of motion of 0° to 120° knee flexion. Knee kinematics were evaluated by measuring the tibiofemoral contact points and femoral roll-back. Meniscus measurements (both natural and artificial) included anterior-posterior meniscal movement, radial displacement, and meniscal height. FINDINGS No difference (P>0.05) was demonstrated in femoral roll-back and tibiofemoral contact points during knee flexion between the implanted and the non-operated knees. Meniscal measurements showed no significant difference in radial displacement and meniscal height (P>0.05) at all flexion angles, in both the implanted and non-operated knees. A significant difference (P ≤ 0.05) in anterior-posterior movement during flexion was observed between the two groups. INTERPRETATION In this pilot study, the artificial polycarbonate-urethane implant, indicated for medial meniscus replacement, had no influence on femoral roll-back and tibiofemoral contact points, thus suggesting that the joint maintains its static kinematic properties after implantation. Radial displacement and meniscal height were not different, but anterior-posterior movement was slightly different between the implant and the normal meniscus.

MR imaging of the anatomy of the anterior horn of the medial meniscus.

Background In cadaveric and arthroscopic studies different insertion locations of the anterior horn of the medial meniscus (AHMM) have been described. Purpose To investigate if the different insertion locations of the AHMM, as described in cadaveric studies, can be determined on magnetic resonance imaging (MRI). Material and Methods MR images of 100 patients without meniscal tears on MRI were retrospectively evaluated. Two observers classified the AHMM insertion based on its position relative to the anterior tibial edge and the medial tibial spine. The association between AHMM insertion and tibial plateau slope, meniscal radial displacement, and anterior intermeniscal ligament (AIL) presence was investigated. Results The AHMM inserted posterior to the anterior tibial edge in 93 knees and anterior to the tibial edge in seven knees (= type III). Of the 93 knees with AHMM insertion posterior to the anterior tibial edge, 63 inserted lateral to the medial tibial spine (= type I) and 30 medial (= type II). The AHMMs inserting anterior to the tibial edge had a significantly (P < 0.05) steeper anterior tibial plateau slope and a significantly (P < 0.05) higher presence of the AIL. No significant difference in radial displacement was observed between the three insertion types (P > 0.05). A strong inter- and intra-observer agreement was observed. Conclusion Three different bony insertion locations of the AHMM, as described in cadaveric studies, could be identified on MRI. All AHMMs inserting anterior to the tibial edge displayed an AIL. Whether there is a clinical correlation with these insertion patterns remains unclear.

MR-Imaging of Meniscal Substitution

More than a century ago, the menisci were considered to be the functionless remains of a leg muscle. Gradually the usefulness and function of the meniscus was investigated and proven, and the link between total meniscectomy, radiographic osteoarthritis and reduced knee function was made. Subsequently, partial meniscectomy was introduced in the clinical practice. However, the frequency of symptomatic knee osteoarthritis was not substantially lowered. Therefore, meniscal repair was introduced for younger individuals with traumatic meniscus lesions with a good healing potential. Later on in the development process, the quest for meniscal replacement strategies arose. The introduction of allogenic, xenogenic and artificial materials followed in research and clinical settings. Nowadays, a lot of research is conducted on meniscal substitutes, because meniscal injuries are a very common problem in the general population. The imaging of the meniscus is running parallel to this evolution. With the development of magnetic resonance imaging (MRI), the meniscus could be perfectly visualized. A lot of studies were published on imaging of the normal meniscus, and subsequently meniscal pathology on MRI was investigated. In the current literature, a growing number of papers describe the MRI findings in artificial meniscus replacements.

Imaging Features of Morel-Lavallée Lesions

Objectives: To review the imaging characteristics of Morel-Lavallée lesions with both ultrasound and magnetic resonance imaging (MRI). Materials and Methods: We retrospectively analyzed 31 patients (mean age = 46 years), diagnosed with a Morel-Lavallée lesion, on ultrasound (n = 15) or MRI (n = 16). On ultrasound the echogenicity, internal septations, hyperechoic fat globules, compressibility and Doppler signal were evaluated. On MRI, T1- and T2-signal intensity, capsule presence, internal septations, enhancement, mass-effect and fluid-fluid levels were assessed. The MR images were classified according to the classification of Mellado and Bencardino. Results: Most of the lesions were situated peritrochanteric, around the knee or the lower leg. The majority of the lesions had a heterogeneous hypoechoic appearance with septations and intralesional fat globules. On MRI, most of the collections were hypointense on T1-weighted images and hyperintense on T2-weighted images. Half of the collections were encapsulated, and most collections demonstrated septations. The collections were classified as seroma (n = 10), subacute hematoma (n = 2) and chronic organizing hematoma (n = 5). Conclusion: Ultrasound is the imaging method of choice to diagnose Morel-Lavallée lesions. MRI can be of use in selected cases (extension in different compartments, large collections, superinfection). Characteristic imaging features include a fusiform fluid collection between the subcutaneous fat and the underlying fascia with internal septations and fat globules. On MRI, six types of ML lesion can be differentiated, with the seroma, the subacute hematoma, and the chronic organizing hematoma being the most frequently observed lesions.