Postoperative radiograph of the hip arthroplasty: what the radiologist should know

Insights Imaging (2015) 6:591–600 DOI 10.1007/s13244-015-0438-5 PICTORIAL REVIEW Postoperative radiograph of the hip arthroplasty: what the radiologist should know Jan Vanrusselt 1 & Milan Vansevenant 3,4 & Geert Vanderschueren 1 & Filip Vanhoenacker 2,3,4 Received: 1 May 2015 / Revised: 18 September 2015 / Accepted: 28 September 2015 / Published online: 20 October 2015 # The Author(s) 2015. This article is published with open access at Springerlink.com Abstract This pictorial review aims to provide the radiologist with simple and systematic guidelines for the radiographic evaluation of a hip prosthesis. Currently, there is a plethora of commercially available arthroplasties, making postoperative analysis not always straightforward. Knowledge of the different types of hip arthroplasty and fixating techniques is a prerequisite for correct imaging interpretation. After identification of the type of arthroplasty, meticulous and systematic analysis of the following parameters on an anteroposterior standing pelvic radiograph should be undertaken: leg length, vertical and horizontal centre of rotation, lateral acetabular inclination, and femoral stem positioning. Additional orthogonal views may be useful to evaluate acetabular anteversion. Complications can be classified in three major groups: periprosthetic lucencies, sclerosis or bone proliferation, and component failure or fracture. Geert Vanderschueren, MD, PhD and Filip Vanhoenacker, MD, PhD share senior authorship. * Jan Vanrusselt 1 Department of Radiology, University Hospital Leuven, Gasthuisberg, Herestraat 49, 3000 Leuven, Belgium 2 Department of Radiology, University Hospital Antwerp, Wilrijkstraat 10, 2650 Edegem, Belgium 3 Department of Radiology, University of Ghent, De Pintelaan 185, 9000 Ghent, Belgium 4 Department of Radiology, AZ St-Maarten Duffel/Mechelen, Rooienberg 25, 2570 Duffel, Belgium Teaching Points • To give an overview of the different types of currently used hip arthroplasties. • To provide a simple framework for a systematic approach to postoperative radiographs. • To discuss radiographic findings of the most common complications. Keywords Hip . Arthroplasty . Postoperative complications . Imaging . Radiography Introduction Hip arthroplasty is one of the most common procedures performed for the treatment of advanced osteoarthritis and is also a required in approximately one-third of hip fracture patients, with 332,000 hip replacements performed in 2010 in the United States [1]. It has been described as one of the most overall successful orthopedic procedures, allowing for early weight bearing and mobilisation, resulting in pain relief, restoration of function, and improved quality of life for many patients [2]. Total hip arthroplasty is most commonly performed for treatment of osteoarthritis. The choice whether to replace a fractured hip with a total hip arthroplasty or a hemiarthroplasty (in which the native acetabulum is spared) remains a topic of an ongoing debate [3]. Since the revolutionary development in the field of hip implants, made by Charnley in the 1960s, surgical techniques and the design of implants as well as the imaging modalities have evolved significantly [4]. Despite the widespread use of MRI, CT, and sonography in joint imaging, the postoperative radiograph remains the keystone in the assessment of hip arthroplasty, as it is readily available at a low cost, with 592 Insights Imaging (2015) 6:591–600 Fig. 3 AP radiograph. Cementless resurfacing hemiarthroplasty. Only the femoral head is replaced (arrowheads), which articulates with the native acetabulum (arrow) Fig. 1 Anteroposterior (AP) radiograph. Cemented unipolar hemiarthroplasty. The femoral stem with the fixed head (arrowheads) articulates with the native acetabulum (arrow) no metal artefact, and facilitating longitudinal comparison. Although cross-sectional studies may have an important role in evaluating and characterizing abnormalities of periprosthetic bone and juxta-articular soft tissues, they usually come at an increased cost. Artefacts still hamper MR image quality and image interpretation, although sequence modification has been shown to allow for evaluation of the bone-prosthesis interface and the surrounding soft tissues. Multidetector CT induces a higher patient radiation exposure compared to conventional radiography. Sonography is not ideally suited to evaluate the prosthesis and periprosthetic bone because of the inability of ultrasound beams to penetrate metal or bone. Fig. 2 AP radiograph. Cementless bipolar hemiarthroplasty. The femoral stem with a fixed head (arrowheads) articulates with a polyethylene lined metal cup (arrow indicates position of the radiolucent polyethylene), which articulates with the native acetabulum (dotted arrow) Different types of hip arthroplasty and fixating techniques Different types of hip arthroplasty Basically, hip arthroplasties can be classified into two major types: hemiarthroplasty and total hip arthroplasty. Hemiarthroplasty In a hemiarthroplasty, the acetabulum is spared whereas the femoral head and neck are replaced. This type of prosthesis is indicated when the native acetabulum is unaffected. A unipolar hemiarthroplasty consists of a femoral stem with a fixed head, which articulates with the native acetabulum (Fig. 1). A bipolar Fig. 4 AP radiograph. Cementless total hip arthroplasty. In a total hip arthroplasty, both femoral head and neck (arrowheads) as well as the acetabulum (dotted arrow) are replaced. The open arrow indicates the position of the radiolucent polyethylene cup at the articulation of the prosthetic femoral head and the acetabulum Insights Imaging (2015) 6:591–600 Fig. 5 AP radiograph. Cementless resurfacing total hip arthroplasty. In a resurfacing total hip arthroplasty, the femoral head (arrowheads) and acetabulum (arrow) are replaced. No radiolucent area at the femoral head—acetabulum is noted (metal—on—metal bearing surface) 593 Fig. 7 AP radiograph. Cemented total hip arthroplasty. In a reverse hybrid cemented arthroplasty, the acetabular cup is fixed with cement (arrowheads) hemiarthroplasty consists of a femoral stem with a fixed head and a polyethylene lined metal cup, accommodating motion between the cup and the prosthetic head as well as between the cup and the native acetabulum (Fig. 2). In a resurfacing hemiarthroplasty, only the femoral head is replaced (Fig. 3). in the bearing surface of the acetabulum and the femoral head. The ‘hard’ bearing surfaces consist of an alloy of metal or ceramic, the ‘soft’ bearing surfaces consist of polyethylene. Total hip arthroplasty In a total hip arthroplasty as in a hemiarthroplasty, a cemented or a cementless stem fixation can be used. In a total hip arthroplasty both the femoral head and neck as well as the acetabulum are replaced (Fig. 4). In a resurfacing total hip arthroplasty, the femoral head and acetabulum are replaced, whereas the femoral neck is spared ( (...truncated)