Radiologic and histologic analysis of morselized allograft in revision total knee replacement

Morselized cancellous allograft was used to fill large femoral and/or tibia l defects in 63 patients (63 knees) who had revision surgery for failed art hroplasty between September 1988 and January 1993. Firm seating of the comp onents on a rim of viable bone and rigid fixation with a medullary stem wer e achieved in all cases. One patient was lost to followup, leaving 62 patie nts with standard radiographic evaluation at 1 month, 3 months, and yearly intervals postoperatively. Fourteen patients required reoperation between 3 weeks and 37 months after revision surgery for loosening (two patients), w ound avulsion (one patient), wound hematoma (two patients), painful wires ( four patients), patellar tendon avulsion from the tibial tubercle (two pati ents), patellar subluxation (one patient), or late onset instability (two p atients). A biopsy specimen was taken from the central portion of the allog raft in each case. Evidence of healing, bone maturation, and formation of t rabeculae was seen in all allografted areas visible on radiograph at 1 year after surgery. No sign of significant bone graft loss had occurred in any case. Likewise, all biopsy specimens, including the 3-week specimen, showed evidence of active new bone formation in the allografted area. Active bone formation was found in and around the allograft pieces, and new osteoid fo rmed directly on dead allograft trabeculae. Vascular stroma was present bet ween the bone fragments deep in the allograft mass. Older biopsy specimens evidenced progressive maturation, and evidence of active osteoclastic activ ity was absent by 18 months after surgery. All patients but one had signifi cant improvement in their pain score as compared with their preoperative st atus. Although the complication rate was high (22 %), all but one patient a chieved lasting fixation to bone, adequate ligament balancing, good range o f motion, and minimal to mild pain. Two patients required revision surgery. Both had greatly improved bone stock so that new implants could be applied with minor additional grafting. This method of bone stock reconstitution a ppears to be reliable when used in conjunction with firm rim seating and ri gid intramedullary stem fixation.