Adverse Local Tissue Reactions are Common in Asymptomatic Individuals After Hip Resurfacing Arthroplasty: Interim Report from a Prospective Longitudinal Study

Abstract

Background: The evaluation of the natural history prevalence of adverse local tissue reactions (ALTRs) using MRI has focused only on metal-on-metal (MoM) bearing surfaces without comparison to nonMoM bearing surfaces.

Questions/purposes: To determine (1) the longitudinal changes and differences in blood metal ion levels in patients with hip resurfacing arthroplasty (HRA), ceramic-on-ceramic (CoC) THA, and metal-on-polyethylene (MoP) THA compared with those undergoing ceramic-on-polyethylene (CoP) THA; (2) how the longitudinal change of synovial reaction classification in patients with HRA, CoC THA, and MoP THA compares with those undergoing CoP THA, and whether there is an association between the presence of an ALTR or metallosis on MRI with corresponding patient-reported outcomes, or the presence of capsular dehiscence; and (3) differences in blood metal ion levels between patients undergoing HRA with an ALTR or metallosis on MRI and those with HRA without these conditions.

Methods: Between March 2014 and February 2019, 22,723 patients underwent primary HRA and THA at one center. Patients received an HRA based on their desired athletic level after surgery and the presence of normal acetabular and proximal femoral bone morphology without osteopenia or osteoporosis. Two percent (342 of 22,723) of patients were contacted to participate, and 71% (243 of 342 hips in 206 patients) were enrolled for analysis at baseline. The patients underwent arthroplasty for degenerative joint disease, and 25 patients withdrew over the course of the study. We included patients who were more than 1 year postarthroplasty. All participants had an MRI examination and blood serum ion testing and completed a Hip Disability and Osteoarthritis Outcome Score survey annually for four years (baseline, year 1, year 2, year 3). Morphologic and susceptibility-reduced MR images were evaluated by a single radiologist not involved in the care of patients for the presence and classification of synovitis (Gwet AC1: 0.65 to 0.97), synovial thickness, and volume (coefficient of repeatability: 1.8 cm3). Linear mixed-effects models were used to compare the mean synovial thickness, synovial volume, and Hip Disability and Osteoarthritis Outcome Score subscales between bearing surfaces at each timepoint and within each bearing surface over time. Marginal Cox proportional hazards models were used to compare the time to and the risk of developing ALTR only, metallosis only, and ALTR or metallosis between bearing surfaces. All models were adjusted for age, sex, BMI, and length of implantation based on known confounders for hip arthroplasty. Adjustment for multiple comparisons was performed using the Dunnett-Hsu method.

Results: Patients with unilateral HRA had higher cobalt and chromium serum ion levels (baseline: 1.8 ± 0.8 ppb, year 1: 2.0 ± 1.5 ppb, year 2: 2.1 ± 1.2 ppb, year 3: 1.6 ± 0.7 ppb) than those with unilateral CoP bearings (baseline: 0.0 ± 0.1 ppb, year 1: 0.1 ± 0.3 ppb, year 2: 0.0 ± 0.2 ppb, year 3: 0.0 ± 0.0 ppb) at all timepoints (p < 0.001 for each time point). More patients who received an HRA developed ALTR or metallosis on MRI than did patients with CoP bearings (hazard ratio 4.8 [95% confidence interval 1.2 to 18.4]; p = 0.02). There was no association between the longitudinal change of synovial reaction to ALTR or metallosis on MRI with patient-reported outcomes. In addition, there was no association between the presence of dehiscence at baseline and the subsequent development of ALTR or metallosis, as seen on MRI. There were elevated cobalt (4.7 ± 3.5 ppb) and chromium (4.7 ± 2.6 ppb) serum levels in patients with unilateral HRA who had an ALTR or metallosis present on MRI at year 1 compared with patients without an ALTR or metallosis on MRI (cobalt: 1.8 ± 1.0 ppb, mean difference 4.7 ppb [95% CI 3.3 to 6.0]; p < 0.001; chromium: 2.3 ± 0.5 ppb, mean difference 3.6 ppb [95% CI 2.2 to 5.0]; p < 0.001) as well as for chromium at year 3 (3.9 ± 2.4 ppb versus 2.2 ± 1.1 ppb, mean difference 1.3 ppb [95% CI 0.3 to 2.4]; p = 0.01).

Conclusion: We found a higher proportion of ALTR or metallosis on MRI in patients with HRA compared with patients with CoP, even when patient self-assessed symptomatology of those with an ALTR or metallosis on MRI was not different than the absence of these features. MRI detected ALTRs in high-function patients, emphasizing that an annual clinical assessment dependent on survey or blood ion testing alone may not detect soft tissue complications. The results of this study are in line with prior consensus recommendations of using MRI as part of a routine follow-up protocol for this patient population.

Level of evidence: Level III, therapeutic study.

Fig. 1

This STROBE flow diagram demonstrates patient recruitment during the study period.

Fig. 2

A-B Coronal multiacquisition variable resonance image combination short tau inversion recovery images of a 62-year-old woman with HRA (7.5 years after implantation at baseline) display progressive osteolysis around the femoral stem (arrows) from (A) baseline to (B) year 1. In addition, the synovium had a 33% volumetric increase between the timepoints. The patient underwent revision surgery after imaging at year 1.

Fig. 3

A-B This Kaplan-Meier estimator demonstrates the probability of developing (A) ALTR, (B) metallosis, and (C) ALTR or metallosis, as seen on MRI, over the four timepoints.

Fig. 4

A-D Coronal multiacquisition variable resonance image combination short tau inversion recovery images of a 64-year-old man with HRA (5.1 years after implantation at baseline) display longitudinal progression in synovial classification from (A) mildly abnormal at baseline by evidence of mild nonspecific synovitis (white arrowhead) decompressing into the trochanteric bursa (gray arrowhead) to (B) ALTR at year 1 to metallosis (C) at year 2 and (D) at year 3, displayed as persistent synovitis (white arrowheads) decompressing into the trochanteric bursa (gray arrowheads) with interval development of isointense-to-hypointense synovial debris (black arrowheads), consistent with metal deposition.

Fig. 5

A-D Coronal multiacquisition variable resonance image combination proton density images of a 71-year-old woman with an MoP THA (4 years after implantation at baseline) display longitudinal progression in synovial classification from normal (A) at baseline with no synovial or bursal expansion to (B) mild synovial expansion with a small amount of synovial debris (white arrowhead), consistent with polymeric wear-related synovitis at year 1 to metallosis (C) at year 2 and (D) at year 3 as evident by persistent, mild synovial expansion (white arrowheads) with interval development of low-signal-intensity deposits (black arrowheads), consistent with metal wear debris.

Fig. 6

A-D Coronal multiacquisition variable resonance image combination proton density images of a 65-year-old woman with a CoP THA implant (2.2 years implantation at baseline) display longitudinal progression in synovial classification from normal (A) at baseline and (B) year 1 with no synovial or bursal expansion to a primary classification of (C) mildly abnormal at year 2 with mild synovial expansion (black arrowhead), decompression of synovitis into the trochanteric bursa, and hypointense staining (white arrowhead) suggestive of metal deposition. (D) The primary classification at year 3 was polymeric and the secondary classification was metallosis, with evidence of progressive synovial expansion (black arrowheads) and bursal fluid distension (white arrowheads) with bulky hypointense metallic debris (gray arrowhead).

Fig. 7

A-D These multiacquisition variable resonance image combination short tau inversion recovery images at baseline and at years 1, 2, and 3 are shown of (A) a patient with a CoP implant (length of implantation at baseline = 2.0 years), (B) a patient with a CoC implant (length of implantation at baseline = 8.8 years), (C) a patient with an MoP implant (length of implantation at baseline = 1.1 years), and (D) a patient with an HRA implant (length of implantation at baseline = 6.6 years) at baseline and at the four longitudinal timepoints, each with a 1-year interval. There was adverse synovial expansion (white arrows) over time for the HRA implant and no progressive synovial expansion for the CoP and MoP implants. The low-signal intensity debris in the patient who underwent HRA indicates a metallosis synovial reaction.

Fig. 8

A-D This figure shows an example of gradual synovial expansion in a 77-year-old man with an HRA implant (length of implantation at baseline 9.6 years) at timepoints evaluated in the study. The synovial volume (green) progressed from (A) 42 cm³ at baseline to (B) 99 cm³ at year 1 to (C) 246 cm³ at year 2 to (D) 256 cm³ at year 3 based on manual segmentation of the synovial reactions, bony anatomy, and implant hardware, as rendered in Meshlab [8].