Imaging near orthopedic hardware

Abstract

Over one million total joint replacement surgeries were performed in the US in 2013 alone, and this number is expected to more than double by 2030. Traditional imaging techniques for postoperative evaluation of implanted devices, such as radiography, computerized tomography, or ultrasound, utilize ionizing radiation, suffer from beam hardening artifact, or lack the inherent high contrast necessary to adequately evaluate soft tissues around the implants, respectively. Magnetic resonance imaging (MRI), due to its ability to generate multiplanar, high-contrast images without the use of ionizing radiation is ideal for evaluating periprosthetic soft tissues but has traditionally suffered from in-plane and through-plane data misregistration due to the magnetic susceptibility of implanted materials. A recent renaissance in the interest of imaging near arthroplasty and implanted orthopedic hardware has led to the development of new techniques that help to mitigate the effects of magnetic susceptibility. This article describes the challenges of performing imaging near implanted orthopedic hardware, how to generate clinically interpretable images when imaging near implanted devices, and how the images may be interpreted for clinical use. We will also describe current developments of utilizing MRI to evaluate implanted orthopedic hardware.

Level of evidence: 3 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:24-39.

Keywords: MRI; arthroplasty; metal; susceptibility.

Figure 1

2D-FSE (1^st Row) and MAVRIC-SL (2^nd Row) images of a polycarbonate grid phantom holding cylindrical bars (1.4 cm Ø) of ultra-molecular weight polyethylene (UHMWPE), titanium, cobalt chrome, stainless steel, or blank (control). Calculated in-plane (3^rd Row) and through-plane (4^th Row) distortions between the 2D-FSE and MAVRIC-SL scans display increasing distortions as the material magnetic susceptibility increases from UHMWPE to stainless steel. Significant distortion for stainless prevented calculation of through-plane distortions. Figure adapted from (43).

Figure 2

The effects of altered receiver bandwidth and magnetic field strength on distortion artifact for a 32 year old male with anterior cruciate ligament reconstruction and a titanium interference screw in the femoral tunnel. White dashed lines indicate region of magnified inset. Image distortion is greatly amplified when acquiring images at a higher field strength (3T) and with a low receiver bandwidth (±31.25 kHz). Imaging at a lower field strength (1.5T) reduces susceptibility artifact, as does scanning with a higher receiver bandwidth (±83.3 kHz).

Figure 3

The effects of implant material composition on susceptibility effect. A volunteer with a ceramic-on-polyethylene bearing total hip arthroplasty. The fast-spin-echo (FSE) and FSE inversion recovery (IR) images have higher susceptibility artifact present as compared to the MAVRIC SL and MAVRIC SL IR sequences, specifically at the dome of the acetabular component and along the stem of the femoral component (arrows). Utilizing a gradient recalled echo (GRE) acquisition, even with ceramic-on-polyethylene bearing surfaces leads to generation of non-diagnostic images.

Figure 4

Images generated utilizing an ultra-short echo (UTE) acquisition, which is part of the GRE acquisition family, at 4 different echo times, of 32 year old man following an anterior cruciate ligament reconstruction with a titanium interference screw in the femoral tunnel (arrow) and a stainless steel button on the anterior aspect of the tibia (arrow heads) to secure the implanted graft. The images display that the use of longer echo times in a GRE acquisition results in a larger area of susceptibility artifact, which is minimized by the use of shorter echo times.

Figure 5

Schematic diagram of the multi-acquisition variable resonance image combination (MAVRIC) technique. The proton spectrum (A) is partitioned into separate frequency bins (B, 4 bins delineated) from which individual image datasets are created (C) at the specified frequency offsets. The data sets are then combined to generate a composite image (D).

Figure 6

Comparison of frequency selective (A), short tau inversion recovery (STIR) (B), and DIXON (C) fat suppression techniques in a 32 year old male subject with an anterior cruciate ligament reconstruction and a titanium interference screw in the femoral tunnel (arrow) and a stainless steel button on the anterior aspect of the tibia (arrow head) to secure the implanted graft. The presence of metallic hardware generates local B_o inhomogeneities, causing local failure of frequency selective fat suppression techniques. STIR imaging has greater uniformity of fat suppression near the implanted hardware, with the reduction of image signal-to-noise ratio. Note the DIXON technique has slightly more artifact (arrowhead) than STIR but less than the frequency selective fat suppression.

Figure 7

Coronal FSE image (TE/TR = 27ms/3800ms) through the patella in a 65 year-old woman status post total knee arthroplasty demonstrates obliquely oriented periprosthetic fracture line (black arrowheads) through the resurfaced patella extending along the superior pegs, with superior retraction of the proximal fracture fragment (white arrowheads).

Figure 8

Axial FSE PD image (A, TE/TR = 35ms/5833ms) in a 63 year-old man, status post total shoulder arthroplasty, demonstrate circumferential osseous resorption about the glenoid component, consistent with component loosening. Axial FSE PD image (B) in a 67 year-old woman following total shoulder arthroplasty demonstrates displacement of the glenoid component (black arrowheads).

Figure 9

Coronal MAVRIC PD (A, TE/TR = 42ms/4000ms) image in a 66 year-old woman status post total hip arthroplasty demonstrates synovial expansion with prominent intermediate signal intensity debris (black arrowheads) eroding into the periacetabular region, yielding circumferential osteolysis (white arrowheads) and acetabular component loosening, as also appreciated on corresponding coronally reformatted CT (B, white arrowheads).

Figure 10

Axial FSE image (A, TE/TR = 27ms/5150ms) in a 68 year-old man status post total knee arthroplasty demonstrates synovitis with intermediate signal intensity particulate debris (white arrowheads) consistent with polymeric wear. Coronal FSE image (B, TE/TR = 27ms/4017ms) demonstrates well circumscribed foci of osseous resorption (black arrowheads), consistent with osteolysis; while osteolysis associated with polymeric wear is classically isointense in signal, cystic osteolysis, as seen in this example, may also occur.

Figure 11

T1 post contrast axial images (A, B, TE/TR = 12ms/582ms) in a 66 year-old man status post total knee arthroplasty demonstrate soft tissue fluid collection extending to the underlying bone (A, black arrowhead) which also communicates with the skin surface via a sinus tract (B, black arrowhead). Axial FSE image (C, TE/TR=30ms/6015ms) demonstrates severe inflammatory synovitis with a hyperintense lamellated appearance (white arrowheads), consistent with infection.

Figure 12

Coronal IR (A, TE/TR=19ms/5175ms) and axial PD (B, TE/TR=35ms/2005ms) images in a 57 year-old woman status post total hip arthroplasty demonstrates proud acetabular fixation screw (black arrowhead) impinging the common iliac vein (white arrowhead), with associated deep venous thrombosis (black arrow), which was confirmed on subsequent Doppler ultrasound (C), which demonstrates lack of power Doppler flow within the common femoral vein (white arrowheads); thrombus was found to extend both proximally and distally.

Figure 13

Axial FSE (TE/TR = 21ms/4283ms) in a 60 year-old woman status post resurfacing arthroplasty demonstrates decompression of an adverse local tissue reaction into the greater trochanteric bursa via a dehiscence in the posterior pseudocapsule (white arrowheads), with debris containing low signal intensity deposits (black arrowheads) located anteriorly within the bursa. ALVAL score at revision was 10 out of 10.

Figure 14

Axial FSE (TE/TR = 22ms/5217ms) in a 55 year-old woman status post total hip arthroplasty demonstrates decompression of synovitis into the greater trochanteric bursa via a dehiscence in the posterior pseudocapsule, with prominent low signal intensity debris (white arrowheads) located anteriorly within the bursa. In contrast to the previous case, note that the synovium is hypointense (black arrowhead), reflecting metal staining, without the marked thickening characteristic of a hypersensitivity-type ALTR.

Figure 15

Axial (A, TE/TR = 25ms/5033ms) and coronal (B, TE/TR = 26ms/4000ms) FSE images, and radiograph (C), in a 33 year-old man status post total hip arthroplasty secondary to traumatic injury demonstrates encasement of the obturator nerve (black arrowheads) within an osseous tunnel (white arrowheads) formed by extensive heterotopic ossification, the extent of which is well appreciated on the concurrent radiograph.