Early failure of tantalum patellar augments in the post-patellectomy knee


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Abstract

Background:Patellectomy is associated with a high rate of extensor mechanism dysfunction. Patients frequently experience weakness, pain, and instability. Patella augmentation with tantalum implants has previously been reported, but concern exists regarding early implant failure. We report our clinical experience with these implants and the effect of tantalum on fibroblast morphology, activity, and proliferation in an in vitro model.Methods:Five patellar augmentations have been performed at our center using the tantalum implant. Each case was reviewed to assess the functional outcome and need for further surgery. For the in vitro model, tantalum was placed onto petri dishes coated in a fibrin gel. Chicken tendon fibroblasts were added and then cultured for 12 days. Digital images were taken at 3, 5, 10 and 12 days. Fibroblast morphology and contraction of the area of fibrin gel were analyzed.Results:Despite initial success with clinically relevant improvements in SF-12 and Oxford Knee Scores, all five implants had failed by 2 yr. Each patient required further surgery, and has reported continuing symptoms. The in-vitro study demonstrated that the presence of tantalum resulted in negative effects on cell morphology and significantly less fibrin contraction when compared with the control dishes from day 3 onwards (P<0.05).Conclusions:Current tantalum augments do not provide a reliable treatment option after patellectomy because of the high risk of early failure. The in-vitro model suggests that tantalum may actually have a negative effect on soft-tissue formation.

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