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Published 4/1/2016

Study Focuses on Dual Taper THA and Revision Outcomes

A study of total hip arthroplasty (THA) patients presented at the 2016 AAOS Annual Meeting found that revision surgery of dual taper THA due to taper corrosion had an early increased incidence of postoperative complications (20 percent) and a rerevision rate of 6 percent.

According to the study findings, metal ion levels and cobalt chromium ratios declined significantly in all patients after the dual taper was removed. Intraoperative tissue necrosis was the only factor associated with the complication rate, suggesting the importance of performing a systematic evaluation of these patients that includes obtaining metal ion levels and using metal artifact reduction sequences magnetic resonance imaging (MARS MRI) to optimize revision outcomes.

As noted by the study authors, dual taper modular femoral stems were introduced to provide greater flexibility and facilitate the adjustment of leg length, femoral anteversion, and offset in primary and revision THA.

"However, more recently, there has been increasing concern regarding this stem design due to the growing numbers of clinical failures and the voluntary recall requiring revision surgery in many of these patients due to fretting and corrosion," said senior author Young-Min Kwon, MD, PhD, associate professor of orthopaedic surgery at Harvard Medical School, and director of the Adult Reconstructive Surgery Fellowship Program and the Center for Metal-on-Metal and Taper Corrosion Evaluation and Treatment at Massachusetts General Hospital.

"We aimed to report early complication rates and identify any potential risk factors associated with complications to provide clinically useful information for surgeons and patients considering revision surgery," stated Dr. Kwon.

Conducting the study
The researchers evaluated a total of 198 revision surgeries in 187 patients (122 males, 65 females; average age, 59.8 years; range, 26 years to 85 years) who underwent THA with a dual taper femoral stem THA. Time between initial implantation and revision surgery for removal of the dual taper stem was 20 months (range, 13 months–116 months). The follow-up period after revision was a minimum of 12 months (range, 12 months–30 months). All patients had dual taper femoral stems with Beta-Ti alloy and a cobalt chromium modular neck.

The indication for revision surgery was the presence of symptomatic pseudotumors on MRI. The investigators generated a Kaplan Meier curve to analyze postrevision implant survivorship. Multiple logistic regression was used to identify any potential risk factors associated with complications and the rerevision rate following revision of dual taper stems.

Assessing results
At mean follow up of 18 months, at least one complication had occurred in 20 percent of 198 revisions (39 patients). A single episode of dislocation, treated with closed reduction, occurred in 16 patients, whereas two patients required rerevision due to multiple dislocations.

Infection requiring rerevision occurred in three patients, while pseudotumor recurrence requiring reoperation occurred in six patients. Implant survivorship for revision for any cause was 90 percent at 30 months. The reoperation rate of revised dual taper was 6 percent (11 out of 198 hips). The median serum levels of cobalt, chromium, and cobalt/chromium ratio decreased from 5.3μg/L (range, 0.3–48.5μg/L), 2.6 μg/L (range, 0.2–64 μg/L), and 4.7 (range, 0.1–35) prerevision to 1.4μg/L (range, 0.2–8.8 μg/L), 0.7μg/L (range, 0.1–3.9 μg/L), and 2.2mg/L (range, 0.4–8.8mg/L) postrevision (P < 0.01), respectively. Intraoperative tissue necrosis was the only factor associated with dislocation and rerevision rate.

Drawing conclusions
According to the authors, this study is one of the largest cohort follow-up studies to date on the clinical outcomes of revision due to taper corrosion in dual taper THA with associated pseudotumors. Noting that intraoperative tissue necrosis was the only factor associated with the complication rate, the investigators asserted that early diagnosis is important in ensuring patients receive appropriate treatment prior to sustaining significant adverse tissue necrosis.

Dr. Kwon's coauthors of Paper 817, "Early Outcomes of Revision Surgery for Taper Corrosion of Dual Taper THA with Pseudotumors in 187 Patients," are Dimitris Dimitriou, MD; Tsung-Yuan Tsai, PhD; William A. Leone, MD; Guoan Li, PhD; Harry E. Rubash, MD; and Andrew A. Freiberg, MD. The authors' disclosure information can be accessed at www.aaos.org/disclosure