Surgeons find a high failure rate using impaction allografting in acetabular revision

Failed hips showed significantly worse radiographic graft incorporation at final follow-up compared to successful hips.

Using impaction allografting during the revision of acetabular components in total hip arthroplasty patients may be associated with a higher failure rate than previously reported, according to a study by surgeons in the Netherlands.

Paul I.J.M. Wuisman, MD, PhD, and colleagues reviewed their results using impaction bone grafting to revise the acetabular component in 71 hips of 68 patients. In 59 hips, revision was necessary due to aseptic loosening and in 12 hips due to septic loosening, according to the study, published in the British edition of the Journal of Bone and Joint Surgery.

Patients averaged 69.1 years of age and follow-up averaged 7.2 years. Surgeons revised only one acetabular component in 32 patients (45%) and revised both components in 39 patients (55%), according to the study.

All grafts consisted of fresh-frozen bone broken into chips about 0.7 cm to 1 cm in diameter. After removing all cartilage from the implantation site, surgeons reamed the host bone to create a bleeding bone bed. They also drilled holes to promote revascularization when necessary. Allografts were then forcefully impacted to create a new solid bone bed, the authors reported.

In all cases, surgeons implanted the acetabular components using a pressurizing technique and cement containing gentamicin. Segmental or cavitary defects were also reconstructed using metal meshes, according to the study.

The researchers found that 25 hips in 24 patients required re-revision and thus were considered failures.

"In five hips, the reason for the reoperation was infection, although none was from the original septic loosening group. These patients were excluded from the analysis of failures, leaving 20 hips in the failed group," the authors wrote. "Taking aseptic loosening as an end-point, the overall survival was 72%."

Of the failures, seven hips failed within 1 year, two of which were due to trauma. Twelve hips failed between 1 and 5 years postrevision and one failed after 7 years.

Overall, 14 of the 20 failed hips (70%) had a type III or type IV defect based on the American Academy of Orthopaedic Surgeons classification system. But there was no significant difference in the percentage of type III or type IV defects between failed and successful hips, the authors noted.

However, surgeons used rim meshes or a combination of rim and medial wall meshes significantly more often in failed hips. Such meshes were used in 15 of the 20 failed hips (75%) and in 29 of the 51 successful hips (57%), according to the study.

Failed hips also showed significantly worse radiographic graft incorporation. At latest follow-up, only 20% of failed hips showed good graft incorporation vs. 66% of successful hips (P<.001), the authors reported.

"We found a worryingly high rate of failure for cemented impaction grafting in acetabular revision. This was associated with the extent of the bone defect, and in particular the lack of bony support behind the graft in cases of large segmental defects," the authors wrote.

"We conclude that in revisions with large acetabular bone defects or pelvic discontinuity, the impaction grafting technique carries with it a high risk of complications," they said.

For more information:

Van Haaren EH, Heyligers IC, Alexander FGM, Wuisman PIJM. High rate of failure of impaction grafting in large acetabular defects. J Bone Joint Surg Br. 2007;89-B. 296-3000.