Sodium magnetic resonance imaging of ankle joint in cadaver specimens, volunteers, and patients after different cartilage repair techniques at 7 T: initial results.

OBJECTIVES: The goal of cartilage repair techniques such as microfracture (MFX) or matrix-associated autologous chondrocyte transplantation (MACT) is to produce repair tissue (RT) with sufficient glycosaminoglycan (GAG) content. Sodium magnetic resonance imaging (MRI) offers a direct and noninvasive evaluation of the GAG content in native cartilage and RT. In the femoral cartilage, this method was able to distinguish between RTs produced by MFX and MACT having different GAG contents. However, it needs to be clarified whether sodium MRI can be useful for evaluating RT in thin ankle cartilage. Thus, the aims of this 7-T study were (1) to validate our sodium MRI protocol in cadaver ankle samples, (2) to evaluate the sodium corrected signal intensities (cSI) in cartilage of volunteers, (3) and to compare sodium values in RT between patients after MFX and MACT treatment. MATERIALS AND METHODS: Five human cadaver ankle samples as well as ankles of 9 asymptomatic volunteers, 6 MFX patients and 6 MACT patients were measured in this 7-T study. Sodium values from the ankle samples were compared with histochemically evaluated GAG content. In the volunteers, sodium cSI values were calculated in the cartilages of ankle and subtalar joint. In the patients, sodium cSI in RT and reference cartilage were measured, morphological appearance of RT was evaluated using the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system, and clinical outcome before and after surgery was assessed using the American Orthopaedic Foot and Ankle Society score and Modified Cincinnati Knee Scale. All regions of interest were defined on morphological images and subsequently transferred to the corresponding sodium images. Analysis of variance, t tests, and Pearson correlation coefficients were evaluated. RESULTS: In the patients, significantly lower sodium cSI values were found in RT than in reference cartilage for the MFX (P = 0.007) and MACT patients (P = 0.008). Sodium cSI and MOCART scores in RT did not differ between the MFX and MACT patients (P = 0.185). No significant difference in sodium cSI was found between reference cartilage of the volunteers and the patients (P = 0.355). The patients showed significantly higher American Orthopaedic Foot and Ankle Society and Modified Cincinnati scores after treatment than they did before treatment. In the volunteers, sodium cSI was significantly higher in the tibial cartilage than in the talar cartilage of ankle joint (P = 0.002) and in the talar cartilage than in the calcaneal cartilage of subtalar joint (P < 0.001). Data from the cadaver ankle samples showed a strong linear relationship between the sodium values and the histochemically determined GAG content (r = 0.800; P < 0.001; R = 0.639). CONCLUSIONS: This study demonstrates the feasibility of in vivo quantification of sodium cSI, which can be used for GAG content evaluation in thin cartilages of ankle and subtalar joints at 7 T. A strong correlation observed between the histochemically evaluated GAG content and the sodium values proved the sufficient sensitivity of sodium MRI to changes in the GAG content of cartilages in the ankle. Both MFX and MACT produced RT with lower sodium cSI and, thus, of lower quality compared with reference cartilage in the patients or in the volunteers. Our results suggest that MFX and MACT produce RT with similar GAG content and similar morphological appearance in patients with similar surgery outcome. Sodium MRI at 7 T allows a quantitative evaluation of RT quality in the ankle and may thus be useful in the noninvasive assessment of new cartilage repair procedures.

Treatment of Full-Thickness Chondral Defects With Hyalograft C in the Knee: Long-term Results.

BACKGROUND: Matrix-associated autologous chondrocyte transplantation (MACT) has become an established articular cartilage repair technique. It provides good short-term and midterm results; however, long-term results are lacking. PURPOSE: To prospectively assess the clinical outcome after MACT in the knee to report long-term results. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty-three subjects (females/males, 22/31; mean age, 32 ± 12 years) were treated between 2000 and 2006 with a hyaluronan-based MACT product and were followed prospectively. The mean body mass index (BMI) was 24.5 ± 3.8 kg/m(2) and the mean defect size was 4.4 ± 1.9 cm(2). Fifty patients had single defects and 3 had multiple defects (41 medial femoral condyle, 6 lateral femoral condyle, 2 patella, 1 tibia). Two patients had 2 defects (medial femoral condyle [MFC]/lateral femoral condyle and tibial/MFC), and in 1 case, multiple defects on the MFC were treated. The patients were stratified into 23 "simple," 22 "complex," and 8 "salvage" cases. Instability or malalignment was treated before or at the time of graft implantation. For 6 patients with small defects (<2 cm(2)), microfracturing was used as first-line treatment before MACT. Clinical assessment was performed once a year with the subjective and objective International Knee Documentation Committee (IKDC) scores, Lysholm score, and a modified Cincinnati Knee Rating System. RESULTS: The mean follow-up time was 9.07 ± 2.9 years (range, 5-12 years). Treatment failure occurred in 12 of 53 cases (22.6%) an average of 2.99 ± 1.40 years after surgery. There was 1 failure (4.3%) among the simple cases, 4 failures (18.2%) in complex cases, and 7 failures (87.5%) in salvage cases. Statistically significant increases were observed in all scores at all time points compared with presurgery levels (P < .05). The subjective IKDC score improved from median 40.4 preoperatively to 74.7 at 10-year follow-up (n = 13 patients; P < .05). CONCLUSION: MACT is an excellent surgical therapy for full-thickness cartilage defects of the knee, with good long-term results for simple defects. However, it should not be used in salvage cases.

Cartilage repair of the knee with Hyalograft C:® magnetic resonance imaging assessment of the glycosaminoglycan content at midterm.

PURPOSE: The aim of this study was to assess the stability of the glycosaminoglycan (GAG) content in the long term after matrix-associated autologous chondrocyte transplantation (MACT) with Hyalograft C in the knee over a follow-up period of one year. METHODS: In this cross-sectional evaluation, 11 patients after MACT of the knee consented to delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) measurements. The mean post-operative interval before the first MR examination was 40.6 ± 22.0 months, and the second MR examination was carried out after another 12 months. The Lysholm score was assessed for clinical evaluation. Quantitative T1 measurements after intravenous negatively charged MR contrast agent administration were performed. Global post-contrast T1 of the reference cartilage and the repair tissue and a relative post-contrast T1 value were calculated. RESULTS: The Lysholm score improved significantly from 59.8 ± 12.9 at baseline to 86.1 ± 15.7 at the second visit (p < 0.01). The mean global T1 of the repair tissue (1st visit 581.3 ± 126.4 ms; 2nd visit 684.1 ± 169.9 ms; p = 0.104) and the mean relative T1 value showed stable results over one year (1st visit 0.81 ± 0.28; 2nd visit 0.76 ± 0.32; p = 0.4). CONCLUSIONS: The study demonstrated stable glycosaminoglycan content of the repair tissue after MACT at midterm.