Allografting effective for large tibial defects in revision TKA

Radiographic evaluations showed no complete radiolucencies, and no patients required further surgery for osteolysis.

CHICAGO — Structural allografts can be an effective option for repairing large tibial bone defects during revision total knee arthroplasty, according to a surgeon speaking here.

Gerard Anderson Engh, MD, conducted a study evaluating his experience using such allografts for repairing type 3 tibial structural defects. He presented his results at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting.

“Structural allografts are a reliable and durable method for managing severe tibial bone loss in revision TKA. Both cemented and cementless stems worked equally well with the allograft bone repair, and radiographic evidence of allograft remodeling is evident with long-term follow-up,” Engh said.

“Our Kaplan-Meier survivorship for reoperation and revision for any reason as the end point was 91% at 10 years, and these were very difficult cases,” Engh said.

”[With] reoperation or revision of the tibial component where the allograft was placed as the endpoint, [survivorship] was 93% at 10 years,” he said.

Revision procedures

The study included 49 knees of 47 patients with a mean age of 67 years. Of these, 23% had underwent previous revision procedures, and 35% required an adjunct procedure for exposure, such as a quad release tubercle osteotomy.

Indications for revision mainly included polyethylene wear and osteolysis (24 knees) as well as aseptic loosening (18 knees) and infection (five knees).

Engh used structural allografts alone in 35 knees and allografts combined with an additional metal augment in 14 knees. He mainly implanted femoral head allografts, which were prepared using a female-type reamer. The defects were cleared to create a platform to which the allograft was inserted and attached with cement.

“Most of these cases were structural femoral heads. We also had some that were complete segmental defects, such as a [type 3] fibial defect, with segmental allograft in place,” Engh said.

In conjunction with the allograft, Engh revised both femoral and tibial components in 32 knees, and revised only the tibial components in 17 knees, he said. He used a wide variety of implants, ranging from modified primary TKA components, which he used in the 1980s before the availability of modular revision systems. He used modular revision systems for the more recent patients.

Noncemented, straight stems were used in 36 knees, with cemented stems — both straight and tapered — used in another 12 knees. He noted that 80% of the tibial stems were greater than 140 mm and thus were diaphyseal filling stems. No stem was used in the remaining one knee revision.

Mean eight years follow-up

Of the 49 knees, one patient was lost to follow-up, eight patients died before the five-year follow-up interval and four knees failed within the first five years, Engh said.

At a mean follow-up of eight years (range 5 to 15 years), Knee Society Scores averaged 84 points for knees that remained in situ. Additionally, mean arc of motion had improved from 88° preoperatively to 103° at final follow-up, according to the study. “Only a few had a very small flexion contracture, and a few had a small extension lag,” Engh said.

Radiographic evaluations showed no complete radiolucencies. Two knees had osteolytic lesions identified in other areas, but no patients required further surgery for osteolysis, he noted.

Four knees required re-revisions, including one resection knee fusion for recurrent infection, one femoral revision for osteolysis in which the tibia and tibial allograft were retained, and two full revisions — one for osteolysis on the femoral side and one for infection. Five other knees required reoperations for such things as extensor mechanism clunk and a patellar component removal.

Nine knees developed complications, including two knees that required bracing and three that had restricted range of motion.

For more information:
Engh GA, Ammeen D. Structural allograft for severe tibial bone loss in revision total knee arthroplasty. #402. Presented at the American Academy of Orthopaedic Surgeons 73rd Annual Meeting. March 22-26, 2006. Chicago.