THE ROLE OF DIFFERENT RADIOLOLOLGICAL IMMAGING MODALITIES IN EVALUATION OF POST - OPERATIVE HIP REPLACEMENT

Abstract

There are approximately 1.5 million hip arthroplasties performed worldwide each year. Whilst these operations are generally very successful complications can occur including aseptic loosening, osteolysis secondary to granulomatous disease, heterotopic new bone formation, infection both superficial and deep, peri-prosthetic and prosthetic fracture and infrequently local nerve damage. Some of these complications are a source of morbidity and may require revision surgery. Plain films are the first line investigation in evaluation of the painful total hip replacement. Assessment of the initial postoperative radiograph is an important part of hip replacement surgery. It is often a prerequisite before the patient’s discharge. The initial radiograph provides information for the surgeon on initial component positioning and fixation, and can be used for reference when retrospectively comparing this film with radiographs taken further on in the life of the prosthesis. Subsequent follow-up radiographs can then be assessed for changes in the appearance of the components and bone which may indicate impending failure. Plain radiography is not sensitive or specific because both infection and aseptic loosening can manifest as peri-prosthetic Lucency or migration. Alternatively infected prostheses may appear radiographically normal. Review of sequential plain radiographs increases the accuracy as there is more rapid progression of lucency or migration in infection. Sonography is not ideally suited to evaluating the prosthesis and periprosthetic bone because of the inability of sound beams to penetrate metal or bone. However, sonography is an excellent modality in evaluating for joint effusion and extra-articular fluid collections, as well as to visualize the soft tissues surrounding the hip such as the iliopsoas tendon/bursa, gluteal tendons, greater trochanteric bursa, and iliotibial band. Sonography has the added benefit of dynamic imaging, hands-on contact with the patient, which may help localize pain and tenderness to an anatomic structure, the ability to perform sonographically guided diagnostic and therapeutic procedures, and the lack of ionizing radiation Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) can be limited due to artefacts caused by the implanted metallic prosthesis. However, newer cross-sectional imaging algorithms have led to a reduction in artefact and an increased role of CT and MRI in imaging the prosthetic joint. CT is particularly useful in the evaluation of bone stock and the integrity