PATELLAR REVISION: BRINGING BACK THE BONE

Severe patellar loss, which precludes adequate fixation of another patellar implant, may be treated by patellectomy, retention of the remaining patellar bony shell (resection arthroplasty), gull wing osteotomy, or patellar bone grafting. In contrast to other treatment alternatives, patellar bone grafting uniquely imparts the potential for restoration of patellar bone. Technique: It is helpful to retain the pseudomeniscus of scar tissue and most of the peripatellar fibrosis tissue to facilitate suture fixation of the tissue flap to the patellar rim. The patellar shell is prepared by removing all fibrous membrane in the crevices of the remaining patellar bone. The tissue flap is created from one of several sources including large flaps of peripatellar fibrotic tissue or a free tissue flap obtained from either the suprapatellar pouch or the fascia lata obtained in the lateral gutter of the knee joint. The tissue flap is sewn to the peripheral patellar rim and peripatellar fibrosis tissue with multiple, nonabsorbable size zero sutures to provide a watertight closure. A small purse string opening is left in one portion of the tissue flap repair to facilitate delivery of bone graft into the patellar defect. Cancellous autograft is harvested from the metaphyseal portion of the central femur during preparation of the femur for the revision implant. In the absence of locally available cancellous autograft, cancellous allograft bone can be used. The bone graft is prepared by morsellising the bone into small fragments of approximately 5 to 8 mm in height and width to facilitate tight impaction of the bone graft into the patellar shell-tissue flap construct. The bone graft is tightly impacted through the opening of the fascial flap into the patellar bone defect with enough volume so that the height of the final patellar construct has a final height measuring more than 20 mm. The tissue flap is then completely closed to contain the bone graft within the patellar shell. The peripatellar arthrotomy is provisionally repaired with several sutures or towel clips to mould the patellar construct in the femoral trochlea as the knee is placed through the full range of motion. Postoperative rehabilitation is not altered from the usual revision knee arthroplasty protocol. In contrast with the treatment alternatives of patellectomy or retention of the bony shell, this new surgical procedure uniquely imparts the potential for restoration of patellar bone stock and may improve the functional outcome in these patients by facilitating patellar tracking and improving quadriceps leverage. The procedure is simple to perform and does not require sophisticated instrumentation or a long learning curve. Based on the current satisfactory short-term to mid-term clinical results, this surgical procedure provides an important addition to the armamentarium of the revision knee arthroplasty surgeon.