Bone-grafting for severe patellar bone loss during revision knee arthroplasty

Background: Severe patellar bone loss may preclude adequate fixation of another patellar prosthesis as a part of revision knee replacement. The purpose of this study was to describe the surgical technique and early clinical results of an alternative to the conventional treatment options of either patellectomy or retention of the remaining patellar osseous shell. The goals of this procedure are to restore patellar bone stock and potentially to improve the functional outcome. Methods: Severe patellar bone loss had left a "patellar shell" that precluded insertion of another patellar implant in nine of 100 consecutive knees undergoing revision total knee arthroplasty. Rather than performing a patellectomy or simply retaining the patellar osseous shell in these nine knees (eight patients), I performed a surgical procedure in which a tissue flap was secured to the patellar rim to contain cancellous bone graft inserted into the patellar bone defect. Final follow-up was at a mean of 36.7 months (range, twenty-four to fifty-five months) after the patellar bone-grafting procedure. Results: The mean preoperative Knee Society scores for function and pain were 39 points (range, 18 to 82 points) and 40 points (range, 20 to 80 points), respectively. At the time of final follow-up, the Knee Society function and pain scores had improved significantly, to a mean function score of 91 points (range, 80 to 98 points) and a mean pain score of 84 points (range, 65 to 100 points) (p < 0.05). The point of greatest patellar thickness measured intraoperatively ranged from 7 to 9 mm. Patellar thickness on immediate postoperative Merchant radiographs averaged 22 mm (range, 20 to 25 mm) whereas, at the time of final follow-up, patellar thickness averaged 19.7 mm (range, 17 to 22.5 mm). Conclusions: In contrast with other treatment alternatives, this surgical procedure imparts the potential for restoring patellar bone stock and may improve functional outcome by facilitating patellar tracking and improving quadriceps leverage. On the basis of satisfactory short-term to mid-term clinical results, this technique of patellar bone-grafting appears to be an important addition to the armamentarium of surgeons performing revision knee arthroplasties.