Abstract
Objectives:
The De Novo NT graft (®)(natural tissue) (Zimmer, Warsaw, IN) is a new technique that consists of a scaffold free allogeneic juvenile cartilage. The purpose of this study is to describe the first cases performed in our institution with De Novo NT (®) assessing both clinical outcomes and magnetic resonance imaging.
Methods:
17 patients with focal patella femoral cartilage lesions treated with De Novo NT (®) were prospectively followed. The mean age at the time of surgery was 30 years. Clinical assessment was performed with the International Knee Documentation Committee (IKDC), KOOS and MARX at baseline and most recent follow up. Magnetic resonance imaging, including T2 relaxation time maps and T1 rho in six patients, was used to evaluate the cartilage repair morphologic characteristics in 12 patients.
Results:
Fifteen patients met the study criteria with a mean follow up of 12 months (±3). The mean defect size was 217±100 mm. In 11 cases the lesion was in the patella, 3 in the trochlea and one in both patella and trochlea. Mean improvement in preoperative to postoperative score was significant for the IKDC objective score 45.8 (±28) to 73.3 (±24) (p=.009), IKDC pain score 49.1 (±20) to 69.8 (±23) (p=.003), KOOS 53.5 (±21) to 75.5 (±15) (p=.001), IKDC subjective 41.3 (±21.7) to 72.7 (±15) (p=.004). MRI demonstrated only two cases (16%) with graft hypertrophy. There was only one case with a detached graft. Mild and moderate subchondral edema was present in 90% (11 patients) of the cases. At the interface between the repaired tissue and the native cartilage, there were only two cases with a fissure of more than 2mm. Very good (66 to 100%) and good (between 33-66%) cartilage fill was present in 54% of the cases. Mild synovial reaction was present in 58% of the cases. From the 6 patients with T2 mapping, all repairs showed significantly different prolongation of quantitative T2 values in both the superficial and deep components of the repair tissue (47.18 for repair vs 28.3 for native (p=0.005) in the deep area and 58.6 for repair vs 37.4 for native in the superficial area (p=0.02). (Figure 1).
Conclusion:
De Novo NT® appears to be an effective treatment for patello-femoral chondral lesions, with significant improvement in the short-term clinical follow up. The MRI indicated implant stability with peripheral integration in most cases. As the implanted cells are allogeneic, synovial reaction is a parameter that should be considered. Only 5 patients had moderate synovial reaction, which did not affect the graft. Quantitative T2 mapping showed stratification of T2 values suggesting maturation to hyaline cartilage.