Figure 1. Coronal T1-weighted MRI of a left metal-on-metal total hip arthroplasty. Part (a) was acquired using conventional fast spin-echo parameters and (b) was acquired using metal artefact reduction parameters described in the text. Mismapping of the signal from the femoral cortex (arrowheads) is nearly completely resolved by the MARS where the stem of the prosthesis lies parallel to B₀. The mismapping of the signal from the neck and acetabulum of the prosthesis is reduced so that the superior pubic ramus (arrow) is discernible.

Figure 2. (a) Axial contrast medium-enhanced CT image through the left hip and pelvis demonstrates a peripherally enhancing lobulated mass of soft-tissue attenuation (arrow) abutting a defect in the medial wall of the left acetabulum (arrowhead) where there is osteolysis at the cement–bone interface of the acetabular cement mantle. (b) Axial T2-weighted MRI image at a similar level through the left hip demonstrates a lobulated mass that has irregular low signal margins and high signal centres (arrows) both on T1-weighted and T2-weighted sequences suggesting loculated cavities containing proteinaceous fluid. Ultrasound-guided biopsies of the wall of the lesion revealed non-specific inflammatory features only without evidence of polyethylene particles. Microbiology was negative.

Figure 3. (a) A Plain film showing osteolysis involving both the acetabular and femoral components. (b) Coronal CT showing a large defect in the medial wall of the right acetabulum, which is not appreciated on the plain radiograph. This information is important in the planning of a revision arthroplasty.

Figure 4. Coronal reformatted CT of the right hip demonstrating osteolysis at the bone–cement interface (arrowhead). The focal area of bone loss and adjacent periosteal reaction was due to infection with Staphylococcus aureus (arrow).

Figure 5. Coronal T1-weighted and T2-weighted images of a right THR with an collection arising from the joint (arrowhead) and tracking initially deep and then passing through a defect in the iliotibial tract (arrows).

Figure 6. Sagittal T2-weighted MRI images of a revision THR with collections due to infection adjacent to the femur at multiple sites (arrows).

Figure 7. A T2-weighted MARS MRI image demonstrating a fracture of the medial calcar with fluid/haemorrhage (arrow) tracking between the medial calcar and the adjacent intact cement mantle.

Figure 8. Sagittal reformatted CT through the right hip demonstrating a stress fracture (arrow) of the posterior column that was not appreciated on conventional AP and coned lateral radiographs.

Figure 9. (a) Normal conventional radiograph of a patient with symptoms of recurrent hip pain 2 years after a right metal-on-metal hip arthroplasty. (b and c) Axial T1-weighted and T2-weighted MARS MRI images within 1 month of the radiograph demonstrates a large fluid collection (arrow) with a low signal T2-weighted rim (arrowhead) surrounding the neck of the prosthesis and the right greater trochanter. The gluteal tendons, which should be visible at this level, have been avulsed.

Figure 10. Axial T1-weighted image through the pelvis in a patient with bilateral metal-on-metal hip arthroplasties demonstrating atrophy of the piriformis on the symptomatic diseased side (black arrow) whereas the piriformis muscle attached to the asymptomatic hip is preserved. Both hips were replaced using a postero-lateral approach.

Figure 11. Axial CT of the right hip in a patient with clinical features of psoas tendon irritation demonstrates a small piece of extruded cement (arrow) anterior to the acetabular component indenting the posterior psoas tendon. An ultrasound-guided local anaesthetic injection confirmed that this was the source of symptoms allowing successful treatment by surgical removal of the offending piece of cement. [Reproduced with permission and copyright of the British Editorial Society of Bone and Joint Surgery.³¹]

Figure 12. (a) Conventional radiograph of a right total hip arthroplasty demonstrating heterotopic ossification adjacent to the supero-lateral acetabular margin (arrow). (b) Two years later there is more extensive opacification inferomedial to the neck of the prosthesis, which was considered to be heterotopic ossification (arrow). The femoral head has migrated into the acetabular cup indicating a full-thickness defect of the polyethylene liner. (c) Coronal reformatted CT of the hip prosthesis demonstrates this opacity to be homogeneous without the cortico-medullary differentiation that would be expected with ossification. (d) An intra-operative photograph demonstrates a black oily liquid (arrow), containing metal debris from the articulation of the head of the prosthesis with the titanium backing of the acetabulum, within the open joint.

Figure 13. Axial CT through a right THR. CT was performed to delineate the extent of osteolysis before revision surgery. A large homogeneous mass of soft tissue surrounds the proximal femoral prosthesis and is associated with extensive osteolysis (arrows). Lymphadenopathy was noted in the right inguinal and external iliac territories. Biopsy of the periprosthetic mass showed non-specific inflammatory changes and no polyethylene debris. The patient died 3 weeks later and lymphoma was diagnosed at post-mortem examination.