Israel Medical Association Journal

Background: Metal-on-metal total hip prostheses (MoM-THR) have been shown to produce hypersensitivity reactions and fluid collection (pseudotumor) by the hip as well as high blood metal ions levels (BMILs).

Objectives: To evaluate the magnetic resonance imaging (MRI) signal-to-noise ratio (S/N) in selected body tissues around the hip of patients who underwent MoM hip replacement and to correlate to BMILs.

Methods: Sixty-one MRI hip examinations in 54 post-MoM-THR patients (18 males, 36 females, mean age 65 years) were retrospectively evaluated independently by two readers. The mean S/N ratio in a region of interest was calculated for periprosthetic pseudotumor collection (PPC), the bladder, fat, and muscle on axial T1w, FSE-T2w, and short tau inversion recovery (STIR) sequences on the same location. BMILs were retrieved from patient files.

Results: PPC was detected in 32 patients (52%) with an average volume of 82.48 mm³. BMIL did not correlate with the presence of PPCs but positively correlated with the PPC's volume. A trend for positive correlation was found between BMILs and S/N levels of STIR images for muscle and bladder as well as for PPC and cobalt levels. A trend for correlation was also seen between BMIL with PPC's T1 w S/N.

Conclusions: Alteration of MRI S/N for different hip tissues showed a tendency for correlation with BMILs, possibly suggesting that metal deposition occurs in the PPC as well as in the surrounding tissues and bladder.

Background: The articular surface replacement (ASR) total hip arthroplasty (THA) was recently recalled from the market due to high failure rates. This modality was used frequently by surgeons at our medical center.

Objectives: To assess the clinical and radiographic outcomes in patients following the surgery and determine the revision rate in our cohort.

Methods: Between 2007 and 2010 139 hips were operated on and evaluated in our clinic. All patients underwent a clinical interview, function and pain evaluation, as well as physical examination and radiographic evaluation. When necessary, patients were sent for further tests, such as measuring cobalt-chromium levels and magnetic resonance hip imaging. Results: With an average follow-up of 42 months the revision rate was 2% (3/139). Patients reported alleviation of pain (from 8.8 to 1.7 on the Visual Analog Scale, P < 0.001), good functional outcomes on the Harris Hip Score, and improved quality of life. Overall satisfaction was 7.86 on the reversed VAS[1]. For patients who required further tests, clinical and radiographic outcomes were significantly poorer than for the rest of the cohort. Average blood ion levels were high above the normal (cobalt 31.39 ppb, chromium 13.32 ppb), and the rate of inflammatory collection compatible with pseudotumors on MRI was 57%.

Discussion: While our study favors the use of the ASR implant both clinically and radiographically, some patients with abnormal ion levels and inflammatory collections on MRI might require revision in the future.