Midterm CT and MRI Appearance of Osteobiologic Plugs in the Knee

Objectives: The objective of this study is to evaluate the bony integration and cartilage morphology of Trufit Plugs (Smith & Nephew) placed to fill chondral defects in the knee.Methods: 17 patients underwent osteobiologic plug implantation for chondral defects of the knee. 13 plugs in 7 patients (mean age 38 years, range 21-49) were available for radiographic review. The mean follow up was 36.4 months (range 20-57 months). Each patient underwent CT for evaluation of bony integration as judged by a percentage of integration. The Hounsfield units (HU) of the plug and the native bone were recorded. A percentage of HU implant and HU native cancellous bone (HU implant/HU native bone) was calculated. MRI was used to evaluate the amount and quality of articular cartilage.Results: CT results showed percentage of bony integration to be mean 37.7% (range 0-100, SD ±30.1). HU implant/HU native bone was mean 32.2%, range 11.8-64.9. MRI showed articular cartilage fill to be: 38.5% filled 0-25% of the defect, 15.3% filled 25-50%, 23.1% filled 50-75%, and 23.1% filled 75-100%. T2 fat saturated signals were isointense in 26.9%, hyperintense in 34.6%, intermediate in 23.1%, hypointense in 23.1%, and cancellous bone in 7.7%.Conclusion: In this study bony integration of the TruFit Plug was poor. The amount of articular cartilage fill was significantly incomplete. The quality of resulting cartilage was inconsistent.