LONG-TERM OUTCOMES OF REVISION TOTAL HIP ARTHROPLASTY WITH THE ZIMMER MODULAR REVISION HIP SYSTEM: A HIGH-VOLUME SINGLE-CENTRE EXPERIENCE

There remains concern regarding prior generations of modular stems in revision total hip arthroplasty (THA). There are limited long-term studies reporting on the outcomes of the Zimmer Modular Revision (ZMR) Hip System. The purpose of this study was to determine long-term survival free from all-cause revision and stem-related failure, as well as radiographic and functional outcomes of the ZMR stem in revision THA. We retrospectively identified all patients in our institutional database who underwent revision THA using the ZMR Revision Hip system from the year 2000 to 2007 (minimum two-year follow-up). Of the 112 ZMR hips (110 patients) identified, a total of 106 hips (104 patients) met inclusion criteria. The ZMR stem design used was titanium modular tapered fluted in all hips, with the exception of two (porous coated cylindrical design). Average age at index ZMR revision was 69 years (range 37–89), 55 (52%) were female, and the mean study follow-up 13.9 years (range 2–22). Indications for index ZMR revision included aseptic loosening (72.1%), periprosthetic joint infection (17.3%), periprosthetic fracture (9.6%), and stem fracture (1.0%). Kaplan-Meier analysis was used to determine the all-cause and stem-related failure revision-free survival. Validated patient reported outcomes were collected and available radiographs were reviewed to determine implant stability. A total of 17 hips (16.0%) underwent a re-revision of any component. The indications for re-revision were stem failure (35.3%), infection (29.4%), instability (29.4%), and aseptic loosening of the acetabular component (5.9%). The average time to all-cause re-revision was 3.8 years (range 0.0–8.3). The five- and 15-year all-cause survivorship was 89.5% (95% CI 86.5–92.5) and 83.0% (95% CI 79.2–86.8), respectively. There were six re-revisions for stem failure (5.7%); five for stem fracture and one for aseptic loosening. The average time to stem failure was 4.6 years (range 1.3–8.2). The five- and 15-year survivorship free from stem-related failure was 97.2% (95% CI 95.6–98.8) and 93.9% (95% CI 91.5–96.3), respectively. At final follow-up the mean Oxford hip score was 36.9 (range 8.0–48.0) and all surviving ZMR stems were well fixed in available radiographs. Femoral revision with the ZMR stem offers satisfactory long-term all-cause revision-free survival, good survival free of stem-related failure, and promising clinical outcomes. Although uncommon, stem fracture was the most common reason for stem-related failure and occurred both early and late. Thus, we have highlighted the importance both early and continued long-term surveillance of patients with the ZMR stem for stem-related failure.