Continued Good Results With Modular Trabecular Metal Augments for Acetabular Defects in Hip Arthroplasty at 7 to 11 Years

Background Reconstruction of large acetabular defects remains a substantial challenge in hip arthroplasty. There remains a paucity of data on the long-term results of acetabular trabecular metal augments.

Questions/purposes The purpose of this study was to assess the survivorship, clinical outcomes, restoration of center of rotation of the hip, and radiological signs of component fixation of trabecular metal augments in the context of reconstruction of acetabular defects.

Methods Between 2002 and 2005, we performed 56 revision (n = 53) and primary (n = 3) THAs using trabecular metal augments in combination with a trabecular metal acetabular component. Of the 56 patients, 16 (29%) died during followup. Of the 40 surviving patients, 37 (93%) had complete radiological followup, 23 (58%) had complete outcome questionnaire followup, and 17 (42%) provided partial questionnaire responses in the clinic or over the telephone. Median followup was 110 months (range, 88-128 months). During that period, we used these implants when preoperative templating indicated that an augment would be required to achieve acetabular implant stability with restoration of the hip center of rotation. We also chose during surgery to use an augment when we could not achieve a stable acetabular trial component without one. The combination of trabecular metal augments and trabecular metal shells was used in 18% (53 of 292) of our acetabular revisions during that time. Survivorship, functional outcome (WOMAC and Oxford hip score), health status (SF-12), and osseointegration according to the criteria of Moore and presence of radiolucencies were determined.

Results Survivorship of the augments at 10 years was 92% (95% confidence interval, 81%-97%). Four patients underwent cup revision, one for infection and three for loosening. The mean WOMAC global score was 79 (SD 17), the mean Oxford hip score 76 (SD 18), the mean physical component SF-12 score was 39 (SD 11), and the mean mental component SF-12 score was 52 (SD 9). The center of rotation was corrected from more than 35 mm above the inter-teardrop line in 48 of 56 patients preoperatively to only five of 46 postoperatively. One patient had radiographic findings suggestive of loosening, but this patient was asymptomatic.

Conclusions The results of the acetabular trabecular metal augments continue to be encouraging in the medium to long term with low rates of revision or loosening in this complex group of patients. We continue to recommend the use of these augments in the reconstruction of complex acetabular defects.

Level of Evidence Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.