Eighty-six Percent Failure Rate of a Modular-Neck Femoral Stem Design at 3 to 5 Years: Lessons Learned.
BACKGROUND
While innovation drives advancement, it is not immune to failure. Previously, we reported a corrosion-related revision rate of 28% (23 of 81 total hip arthroplasties) among patients who received the Rejuvenate modular-neck stem implant with short-term follow-up. Because we observed a dramatic interval failure rate after our initial report, we undertook this study.


METHODS
We prospectively followed a cohort of patients who had undergone implantation of the Rejuvenate modular-neck stem, as previously reported. At a minimum of 3 years of follow-up (range, 3.0 to 5.5 years), 73 hips in 63 patients (90% of the original group) were available for analysis. The mean serum cobalt and chromium ion levels were obtained preoperatively and postoperatively. Elevated serum cobalt ion levels (>4 μg/L), pain, or abnormal magnetic resonance imaging (MRI) findings were indications for revision surgery. Patient factors and serum metal ion levels were correlated to revision surgery. Additionally, post-revision serum cobalt and chromium ion level trends were assessed.


RESULTS
An 86% clinical failure rate (63 of the 73 hips) was observed at a mean follow-up of 4.2 ± 0.6 years (range, 3.0 to 5.5 years); 57 (78%) of the hips underwent revision at a mean of 3.2 ± 1.0 years (range, 1.0 to 5.5 years), and 6 (8%) of the hips were scheduled for revision. Patients who underwent revision surgery were younger and had greater serum metal ion levels and greater pain compared with patients who did not undergo revision. An elevated serum cobalt ion level was the most important independent factor associated with revision surgery. Cobalt ion levels decreased sharply after revision; however, some patients demonstrated persistent elevation with more gradual decline.


CONCLUSIONS
Emphasizing the reporting of positive results may leave orthopaedic surgeons reticent to publicize negative results; however, the high failure rate of this implant design within 5 years prompted this report. We believe that patients and orthopaedic surgeons should be made aware of this implant's clinical problems and patients should be followed closely. Expedient revision is necessary when failure is identified, to minimize potentially severe tissue damage and metal toxicity.


METHODS
Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Department of Orthopaedic Surgery (D.T.B., M.M., and S.J.I.) and Institute for Academic Medicine (J.P.), Houston Methodist Hospital, Houston, Texas.
Derek T
DT
Bernstein
Department of Orthopaedic Surgery (D.T.B., M.M., and S.J.I.) and Institute for Academic Medicine (J.P.), Houston Methodist Hospital, Houston, Texas.
Morteza
M
Meftah
Department of Orthopaedic Surgery (D.T.B., M.M., and S.J.I.) and Institute for Academic Medicine (J.P.), Houston Methodist Hospital, Houston, Texas.
Jaya
J
Paranilam
Department of Orthopaedic Surgery (D.T.B., M.M., and S.J.I.) and Institute for Academic Medicine (J.P.), Houston Methodist Hospital, Houston, Texas SJIncavo@houstonmethodist.org.
Stephen J
SJ
Incavo
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D005260:Female; D005272:Femur Neck / Q000601:surgery*; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation
D002857:Chromium; D003035:Cobalt