Trabecular Metal™ Cups for Acetabular Defects With 50% or Less Host Bone Contact

Abstract

Acetabular component revision in the context of large contained bone defects with less than 50% host bone contact traditionally have been treated with roof reinforcement or antiprotrusio cages. Trabecular Metal TM cups (Zimmer, Inc, Warsaw, IN) may offer a reasonable treatment alternative. We evaluated the clinical and radiographic outcome of this mode of treatment. We prospectively followed 53 hip revision acetabular arthroplasty procedures performed with Trabecular Metal TM cups for contained defects with 50% or less contact with native bone. All patients were clinically and radiographically evaluated for evidence of loosening or failure. Minimum followup was 24 months (average, 45 months; range, 24-71 months). Contact with host bone ranged from 0% to 50% (average, 19%). The mean postoperative Merle d'Aubigne-Postel score was 10.6 (range, 1-12), with a mean improvement of 5.2 (range, À4-10) compared to the preoperative score. Two failed cups (4%) were revised. Two additional cups (4%) had radiographic evidence of probable loosening. Complications included four dislocations and one sciatic nerve palsy. The data suggest treatment of cavitary defects with less than 50% host bone contact using Trabecular Metal TM cups, without structural support by augments or structural bone grafts, is a reasonable option.

Promising Mid-term Results With a Cup-cage Construct for Large Acetabular Defects and Pelvic Discontinuity

“…Other authors have reported similar improvements in functional scores after revision hip surgery; Lakstein et al [18] reported a significant improvement to a postoperative Merle d'Aubigné-Postel score of 10.6 with the use of TM 1 cups for complex acetabular defects. In his pelvic discontinuity series treated with a distraction technique, Sporer et al [28] reported a significant increase in Merle d'Aubigné-Postel functional score from 3.3 to 9.6 after the revision surgery.…”

“…Although this number might seem high, it is important to take into account that these cases are very complex procedures with several previous surgeries. The previously reported complication rate for complex acetabular revisions treated with TM 1 with or without augments ranges from 5% to 20% [1,7,17,18]. Additionally, in series treating pelvic discontinuities, the complication rate ranged from 16% to 29% [25,28,31].…”

“…In this group all the constructs were solidly fixed at a mean followup of 68 months, providing better results than that reported for TM 1 cups alone and in combination with augments. Lakstein et al [18] used TM 1 cups in 53 hips with Gross Type IV defects and reported a revision rate of 4% for aseptic loosening at a mean followup of 53 months and Sternheim et al [29] in the same series reported an 8% revision rate at a mean followup of 72 months. Additionally, Lachiewicz and Soileau [17] used TM 1 cups for acetabular revision in 39 hips and had a repeat revision rate of 3% at a mean followup of 3 years; however, only 26 of the 39 hips had Paprosky Type 3 acetabular defects.…”

“…The classification of the deficiency at the time of surgery remains somewhat subjective but was performed by the senior surgeon who developed the classification scheme. Only one outcome instrument was used (the Merle d'Aubigné-Postel score), but it was collected at all time periods and it has been previously used to report outcomes after complex revision hip surgery [18,28]. Also, all surgeries were done or assisted by this same experienced orthopaedic surgeon and therefore the outcomes cannot be extrapolated.…”

“…Implants in these optimal revision settings have shown excellent long-term survivorship ranging from 95% to 98% at 10 years [8,9,32]. Highly porous metal implants such as Trabecular Metal TM (TM) (Zimmer Inc, Warsaw, IN, USA) cups that offer improved bone ingrowth and biomechanical properties [3,5,14,21,33] have also shown encouraging results for acetabular revision [1,17,18,29]. However, it may be difficult or impossible to achieve stability, even with these highly porous metal implants, if the acetabular defect is large, bone quality is poor, there is limited host bone contact, or there is pelvic discontinuity.…”