MRI of THA Correlates With Implant Wear and Tissue Reactions: A Cross-sectional Study

Abstract

Background: MRI is predictive of adverse local tissue reactions (ALTRs) after THA but how MRI directly relates to implant surface wear, fretting, and trunnion corrosion at different articulations between implant components remains unclear. MRI generates high-contrast images to display soft tissues around arthroplasty and may provide a surgeon the means to distinguish and differentiate host-related synovial patterns as a response to either polyethylene wear or metal wear and corrosion products.

Questions/purposes: The purposes of this study were (1) to correlate findings from MRI in patients who have undergone THA with direct assessment of implant wear, corrosion, and fretting from retrieved components; and (2) to distinguish the unique synovial responses on MRI in patients who have undergone THA based on bearing materials.

Methods: In this prospective study, patients undergoing THA (181 patients, 187 hips) with metal-on-metal (MoM), hip resurfacing (HRA), metal-on-polyethylene (MoP), ceramic-on-polyethylene, ceramic-on-ceramic, or modular neck designs having revision surgery (between October 2013 and June 2017) underwent preoperative MRI. A single reader blinded to the bearing surface made an assessment of the synovial response (Gwet's AC1, 0.65-0.97); these data were compared with semiquantitative histology of tissue samples by a single reader (Gwet's AC1, 0.92) and semiquantitative wear, corrosion, and fretting analysis of retrieved components using Goldberg scoring (Gwet's AC1, 0.60-0.79). Direct noncontact measurements of implant wear were also made. Correlations and analyses of variance were used to assess associations between metrics and differences by implant type, respectively.

Results: Correlations were found between MRI synovial thickness with severity of fretting and corrosion damage of the female head-neck trunnion of femoral stems in modular designs (ρ = 0.26 [95% confidence interval {CI}, 0.12-0.39]; p = 0.015, n = 185) and ALTR grade and volumetric wear in MoM bearings (ρ = 0.93 [95% CI, 0.72-0.98]; p < 0.001, n = 10). MRI synovial thickness was highest in patients identified with aseptic lymphocyte-dominated vasculitis-associated lesions and diffuse tissue necrosis. On MRI, MoP hips demonstrated a distinct polymeric synovial response, whereas HRA, MoM, and modular hips more commonly demonstrated ALTR. Hips classified as having a polymeric synovial response on MRI had a greater number of particles present in tissue samples.

Conclusions: In this study, we demonstrated that MRI of THA can distinguish synovial responses that reflect the bearing type of the implanted THA and correlate to direct measurements of implant wear, corrosion, and fretting and histologic assessment of wear particles in periprosthetic tissues. MRI provides a means of direct, noninvasive visualization of the host-generated synovial response. Patients presenting with painful arthroplasties may be evaluated for the cause of their discomfort, specifically highlighting any concerning synovial reactions that would warrant more prompt surgical intervention. Future studies would benefit from a prospective evaluation of different implants to assess the natural longitudinal history of arthroplasty complications, including the development and prevalence of ALTR across bearing constructs.

Level of evidence: Level III, diagnostic study.

Fig. 1

A STROBE flow diagram demonstrates patient recruitment during the study time period.

Fig. 2

A box-and-whisker diagram, and associated data points, display that the MRI synovial thickness of HRA implants was greater than MoP designs (p = 0.012). In addition, the synovial thickness of MoM designs was greater than the synovial thickness of CoP designs (p = 0.012).

Fig. 3

A box-and-whisker diagram, and associated data points, display that the MRI synovial thickness by the histologic classification of acellular membrane was thinner than classic ALVAL (p < 0.001) and extensive necrosis (p = 0.004). In addition, extensive necrosis had a greater synovial thickness than particle reaction (p = 0.003), and classic ALVAL had a larger synovial thickness than the classification of particle reaction (p = 0.002).

Fig. 4

A box-and-whisker diagram, and associated data points, display that the MRI synovial volume of the acellular membrane classification had the least synovial volume across all histologic categories (^*p < 0.013), and extensive necrosis had a synovial volume larger than the classifications of classic ALVAL (p = 0.019) and particle reaction (p = 0.009). In addition, classic ALVAL had a greater MRI synovial volume than particle reaction (p = 0.019).

Fig. 5

A montage of images is used to display the full assessment of MoP THAs performed in this study, including preoperative imaging (MAVRIC-SL imaging), intraoperative tissue sampling (hematoxylin and eosin staining), and postoperative wear evaluation. A traditional MoP design (first row, 68-year-old man, femoral stem: VerSys® [Zimmer, Warsaw, IN, USA], femoral head: cobalt-chrome [Zimmer], acetabular component: Harris-Galante [Zimmer], LOI: 20 years) displayed an eccentric femoral head in the polyethylene liner that produced a mild polymeric reaction in the synovium on the MR images. The corresponding histologic assessment displayed sheets of macrophages indicative of polyethylene particles, which corresponded to a large volumetric deviation measured on the polyethylene liner. In contrast to the MoP THA, a modular neck MoP THA design is shown on the second row (54-year-old woman, femoral stem: Rejuvenate [Stryker, Kalamazoo, MI, USA], femoral head: cobalt-chrome [Stryker], acetabular component: Trident [Stryker], LOI: 1.9 years). The MR images displayed a markedly thickened synovial reaction and ALTR (arrows) that correlated to corrosion products at the modular interfaces identified in the corresponding histology as well as the minimal volumetric deviation measured on the polyethylene liner.

Fig. 6

A montage of images is used to display the full assessment of MoM THA performed in this study, including preoperative imaging (MAVRIC-SL imaging), intraoperative tissue sampling (hematoxylin and eosin staining), and postoperative wear evaluation. The MoM THA on the first row (67-year-old man, femoral stem: unknown design, femoral head: cobalt-chrome [DePuy, Warsaw, IN, USA], acetabular component: Pinnacle® [DePuy], LOI: 9.8 years) displays evidence of low signal intensity deposits on transverse MR images (arrows) that corresponded to necrotic tissue and perivascular lymphocytes typical of ALVAL as displayed in the corresponding histology in addition to moderate linear and volumetric wear as measured on the femoral head and acetabular cup. In contrast to the high wear MoM, another MoM THA is displayed on the second row (52-year-old man, femoral stem: Corail® [DePuy], femoral head: cobalt-chrome [DePuy], acetabular component: Pinnacle [DePuy], LOI: 5.2 years). The MR images show evidence of stem loosening on MR (arrows) as does the corresponding radiograph (arrowheads). The histologic evaluation found no synovial reaction, which also correlated to limited wear on the retrieved components.

Fig. 7 A-B

The MR images of an enrolled patient with an MoP implant displays a thick synovium (17 mm), but low blood serum ion levels (cobalt [Co] = 1.8 ppm and chromium [Cr] = 1.4 ppm) were present. The coronal fast-spin echo image (A) and MAVRIC-SL (B) images display increased synovial thickness (arrows), indicative of an ALTR confirmed by histologic scores with tissue obtained at the time of revision.