Imaging features of complications following hip replacement: A pictorial assay

Transcription

1 Imaging features of complications following hip replacement: A pictorial assay Poster No.: C-2041 Congress: ECR 2014 Type: Educational Exhibit Authors: K. Pilania, B. Jankharia ; Mumbai, maharashtra/in, Mumbai/IN Keywords: Complications, MR, Musculoskeletal joint, Prostheses DOI: /ecr2014/C Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 24

2 Learning objectives To review the imaging appearances of the common complications post hip replacement with emphasis on MR imaging features. To differentiate complications from normal post arthroplasty appearances. To understand the parameter modifications required to overcome the susceptibility artefact on MRI Page 2 of 24

3 Background Hip replacement surgery helps millions of people worldwide, walk painlessly each year, and with increasing life span and decreased clinical threshold for surgery this number will continue to rise. With the increase in the number of surgeries and the longevity of implants, the incidence of failures and complications is also rising and so is the need of early and prompt diagnosis. Total hip arthroplasty involves either Total replacement of the femoral head as well as neck and the acetabulum by separate prostheses (Fig 1) or, a surface replacement or a "double cup" resurfacing arthroplasty (Fig 2) where only resurfacing of the femoral and the acetabular articular surfaces with metal cups is done. The type of replacement is further classified on the basis of the material of the prosthesis (eg. metal vs ceramic), articulating surfaces (metal on polythelene vs metal on metal vs ceramic on polythelene etc) and the technique used for fixation (cement vs cementless). The various complications following arthroplasty include: aseptic loosening, particle disease (osteolysis), infection, component wear, dislocation, fracture, heterotopic ossification, metal-induced reactive mass (ALVAL reaction), abductor muscle tear, iliopsoas impingement and muscle atrophy. Radiographs though still the first modality to evaluate a post arthroplasty hip, and reasonably reliable in detecting dislocation (Fig 3), fracture and heterotopic ossification, have vast limitations especially for soft tissue pathology. Differentiating loosening from infection, osteolysis from normal post arthroplasty appearances like stress shielding, especially in their early stages can also be tricky on radiographs and MRI complements radiographs perfectly. Cross sectional imaging in postarthroplasty hips has always been a challenge because of the susceptibility artifacts on MRI (Fig 4,6) and beam hardening on CT scan which [1,2] prevent accurate evaluation of regions of interest near the implants. Page 3 of 24

4 Lately with the advent of metal artefact reduction sequences (MARS) and newer instrumentation, the challenge of susceptibility artefacts due to metal implants have largely been overcome(fig 5,7). We intend to provide an insight especially into the MR imaging features of the various associated complications. Page 4 of 24

5 Images for this section: Fig. 1: Total hip replacement arthroplasty Page 5 of 24

6 Fig. 2: Resurfacing arthroplasty Page 6 of 24

7 Fig. 3: Frontal radiograph shows well the malaligned acetabular cups on both sides. Page 7 of 24

8 Fig. 4: Conventional T1W coronal image in a patient with left resurfacing arthroplasty precludes visualisation of the surrounding soft tissues due to the susceptibility artefacts. Page 8 of 24

9 Fig. 5: T1W coronal image of the same patient as in Fig 4, with high bandwidth (MARS) modification, shows the surrounding soft tissues better. Page 9 of 24

10 Fig. 6: Axial T2W image without bandwidth modification shows a large artefact over the left hip obscuring the soft tissues. Fig. 7: Axial T2W image with bandwidth modification shows significant reduction in the artefact and good visualization of the soft tissues. Page 10 of 24

11 Findings and procedure details This essay is based on the findings from 136 patients with 181 replaced hips, who presented for MRI. The duration of replacement ranged from 6 months to 5.5 years. All MRI studies were performed on a 1.5T scanner after obtaining an informed consent from the patients. Both hips were scanned together in a six channel body coil. All subjects underwent MRI using standard clinical protocols optimized to minimize metallic susceptibility artefact. The protocol included STIR, T1W and T2W coronal, T1W and T2W axial and T2W sagittal sequences. Ethical committee clearance was not obtained as the study was retrospective. Fast spin-echo (FSE) T1W and T2W images were obtained in the coronal, axial and sagittal planes with the frequency encoding direction oriented away from the tissues of interest. The parameters were as follows: TR range, ms; TE range, ms; bandwidth ; FOV, mm; number of signals acquired, 2; acquisition matrix, (frequency) 75-80(phase); and slice thickness, 4 mm. A fast inversion recovery sequence was performed in the coronal plane using the following parameters: TR/ TE, 4480/49; inversion time, 130 ms; bandwidth, 407; FOV, mm; number of signals acquired, 2; acquisition matrix, 256 (frequency) 100(phase); and slice thickness,4 mm. The average acquisition time was 2-4 min for each imaging plane with a total acquisition time of approximately minutes.the images from each sequence were loaded on a workstation. Structured reporting was done with comments on specific issues following hip replacement viz, Periprosthetic soft tissue mass, Periprosthetic osteolysis, Gluteal muscle atrophy, Iliopsoas atrophy, Muscle edema, Muscle / Tendon tear and Lymphadenopathy. Page 11 of 24

12 Conclusion RESULTS: Diagnostic images were obtained in all patients but two. Of the 181 hips, 110 had total hip replacement (THR) and 71 had resurfacing. The following abnormalities were found. Periprosthetic osteolysis (18), Loosening (3), Periprosthetic soft tissue mass (80), Muscle atrophy - Gluteal maximus (10), Gluteal minimus and medius (25), Piriformis (41) Iliopsoas (39), Muscle edema (1), Muscle/tendon tear (2), Lymphadenopathy (12). Periprosthetic soft tissue (Fig 8) is defined as abnormal fluid/ intermediate- to lowsignal- intensity lesion adjacent to the prosthesis on T1W and T2W images. The low signal on T2-weighted images suggests possible metal deposition (Fig 8). This was [3,4] found in in 80 hips. These are reactive masses also known as pseudotumors and have been labelled histologically "aseptic lymphocyte-dominated vascular-associated [3] lesions" (ALVAL lesions). Female sex, small prosthetic cup size and poor positioning of the components are factors that possibly increase the risk of developing these reactive [5,6,7] masses. Sometimes intermediate / high T1 signal intensity was also seen (Fig 8) and this may also reflects metal deposition, though hemorrhage may also present similarly. A peripheral T1 hyperintense rim may be indicative of infection. Hence, there may be a dilemma in distinguishing juxtaarticular abscess from reactive masses on the basis of imaging features alone, especially in symptomatic patients and diagnostic confidence is best achieved by biopsy / aspiration and analysis of the material. The periprosthetic soft tissues can be classified into three types based on MRI findings: type 1 (Fig 9), cystic masses with wall < 3 mm; type 2 (Fig 10), cystic masses with wall > 3 mm but less than the diameter of the cystic component; and type 3 (Fig 11,12), [8] predominantly solid masses. The size of the mass and its relationship to surrounding structures was meticulously defined. Careful inspection for communication of collection with joint was done to avoid erroneously labelling a thickened noncommunicating trochanteric bursa as a "reactive mass." [3] Page 12 of 24

13 Osteolysis is denoted as intermediate- signal-intensity marrow replacement of the hyperintense fatty marrow (Fig 13). The presence, location (acetabular, femur or both) as well as the size was recorded. Focal well-defined area of osteolysis without surrounding edema is usually labelled as focal particle disease (Fig 13,14). Linear, long segment, fluid signal-intensity marrow replacement of > 2mm width, along the bone prosthesis interface, without significant marrow edema is suggestive of aseptic loosening of the prosthesis (Fig 15,16). An irregular ill-defined area of osteolysis with marrow edema is usually seen in cases of infection (Fig 17). Presence of enlarged lymph nodes add to the level of confidence. 18 showed periprosthetic osteolysis of which three had features suggestive of loosening of the femoral prosthesis. The gluteus, piriformis and iliopsoas muscles were assessed for the presence of atrophy (Fig 18,19), defined as loss of volume and the presence of fatty replacement, and for the presence of muscle edema (Fig 17), defined as the presence of high signal intensity on inversion recovery images. Gluteal maximus atrophy - moderate to severe was appreciated in 10 hips, gluteus medius and minimus atrophy was seen in 25 hips. 39 of 179 hips had iliopsoas atrophy and 41 had atrophy of the piriformis. The presence or absence of a tear (Fig 20) is graded as follows: 1, no tear; 2, partialthickness tear; or 3, full-thickness tear. The pelvic region was assessed for enlarged lymph nodes (Fig 19) with enlargement being defined as > 1cm in short axis diameter. Lymphadenopathy was reported in 12 patients. Abductor tendon tear was seen in 3 and muscle edema in one hip. DISCUSSION: Page 13 of 24

14 This study thus underlines the fact that MR on a 1.5T scanner with its specialised metal artefact reduction sequences (MARS) is a viable technique to image the post arthroplasty hip and has vast potential in prompt and early diagnosis of complications in these patients. Page 14 of 24

15 Images for this section: Fig. 8: STIR, T1 and T2W coronal MARS images show a large high/intermediate T1 and low/intermediate T2 signal intensity periprosthetic soft tissue on the left. Fig. 9: Axial T2W and T1W MARS images showing a thin walled (< 3mm) type 1, T2 hyperintense periprosthetic soft tissue lesion anterior to the femoral neck on the right. Page 15 of 24

16 Fig. 10: Axial T2W and T1 W MARS images showing a thick-walled type 2 periprosthetic collection adjacent to the right iliopsoas. Page 16 of 24

17 Fig. 11: Axial T2W and T1 W MARS images show a heterogenous thick walled, type 3, periprosthetic soft tissue lesion in the iliopsoas bursa on the left. Fig. 12: Plain radiograph of the pelvis of the same patient as in Fig 11, shows no significant abnormality. Page 17 of 24

18 Fig. 13: Plain radiograph of the pelvis with both hips shows periprosthetic osteopenia/ osteolysis involving the greater trochanter on the left. Confidently differentiating osteopenia due to stress shielding from periprosthetic osteolysis is not always possible on radiographs. Page 18 of 24

19 Fig. 14: The MARS MRI images of the same patient as in Fig 13 clearly show the radiolucent area in the left greater trochanter to represent periprosthetic osteolysis (focal particle disease). Page 19 of 24

20 Fig. 15: Plain radiograph of the pelvis with both hips shows periprosthetic radiolucency all along the bone prosthesis interface on the lateral aspect of the femoral stem on the left. Page 20 of 24

21 Fig. 16: Linear fluid signal is clearly seen tracking along the left femoral stem on the MARS images, without surrounding edema, highly suggestive of loosening. Fig. 17: Periprosthetic osteomyelitis with fracture: T1W and T2 W coronal images show large amount of periprosthetic fluid with osteolysis. Edema of the surrounding soft tissue and muscles is seen with fluid also tracking along the bone prosthesis interface. Associated fracture of the femoral stem is seen as well. Page 21 of 24

22 Fig. 18: Coronal T1W and T2 W images show severe atrophy of the iliopsoas on the left. Fig. 19: Axial T2W and T1 W images show moderate atrophy of the gluteus medius and minimus on the left. An enlarged left external iliac lymph node (arrow) is seen as well. Page 22 of 24

23 Fig. 20: Abductor tear: Coronal STIR,T1W and T2W MARS images show a tear of the tendinous insertion of the right gluteus medius. Page 23 of 24

24 References Lee MJ, Kim S et al.overcoming Artifacts from Metallic Orthopedic Implants at High-Field-Strength MR Imaging and Multidetector CT.RadioGraphics 2007; 27: White LM, Buckwalter KA. Technical considerations: CT and MR imaging in the postoperative orthopedic patient. Semin Musculoskelet Radiol 2002;6:5-17. Ostlere S. How to image Metal-on-Metal prostheses and their complications. AJR 2011; 197: Davies AP, Willert HG, Campbell PA, Learmonth ID, Case CP. An unusual lymphocytic perivascular infiltration in tissues around contemporary metalon-metal joint replacements. J Bone Joint Surg Am 2005; 87: Grammatopoulos G, Pandit H, Murray DW, Gill HS; Oxford Hip and Knee Group. The relationship between head-neck ratio and pseudotumour formation in metal-on-metal resurfacing arthroplasty of the hip. J Bone Joint Surg Br 2010; 92: De Haan R, Campbell PA, Su EP, De Smet KA. Revision of metal-on-metal resurfacing arthroplasty of the hip: the influence of malpositioning of the components. J Bone Joint Surg Br 2008; 90: Glyn-Jones S, Pandit H, Kwon YM, Doll H, Gill HS, Murray DW. Risk factors for inflammatory pseudotumour formation following hip resurfacing. J Bone Joint Surg Br 2009; 91: Hauptfleisch J, Pandit H, Grammatopoulos G,Gill HS, Murray DW, Ostlere S. A MRI classification of periprosthetic soft tissue masses (pseudotumours) associated with metal-on-metal resurfacing hip arthroplasty. Skeletal Radiol 2012;41: Page 24 of 24