Imaging evaluation of the postoperative knee ligaments

Until the advent of magnetic resonance imaging (MRI), evaluation of ligament reconstruction of the knee was largely based on clinical examination and radiographs. MRI is the modality of choice for noninvasive evaluation of reconstructed ligaments, menisco-capsular structures and soft tissues. This article reviews the surgical techniques, normal and abnormal appearances of the ACL and PCL grafts and common complications following ligament reconstruction.     

Imaging of the postoperative knee: normal and pathologic findings

Surgical management of lesions of the knee has exponentially increased over the last several years. MRI plays a major role in postoperative follow-up and evaluation of patients with residual symptoms. Familiarity with the different surgical procedures and potential complications and knowledge of normal and abnormal postoperative MRI findings are essential for evaluation of the postoperative knee. The main purpose of this article is to review the postoperative imaging features of ligaments, menisci and cartilage of the knee joint since these MRI features may lead the surgeon to consider repeat surgery.     

Imaging of the knee

MR imaging has become the primary imaging modality of the knee. Its advantages include its noninvasive nature, multiplanar imaging capability, excellent soft-tissue contrast, and high resolution. The need for multiple imaging modalities is obviated, as the menisci, cruciate ligaments, synovium, articular cartilage, marrow, and periarticular soft tissues can be simultaneously evaluated. Other imaging modalities may occasionally be helpful in the evaluation of specific problems including CT in tibial plateau fractures, real-time ultrasound for the confirmation of a popliteal cyst or popliteal artery aneurysm, and arthrography for the detection of prosthetic joint loosening.     

Imaging of the multiple-ligament-injured knee

Imaging of the multiple-ligament-injured knee requires a comprehensive assessment of ligaments, cartilage, bone, peripheral nerves, and vascular anatomy. It is imperative that the radiologist be a crucial part of the trauma team, to provide prompt diagnostic assistance without unnecessary delays in patient management. MR angiography remains a promising modality to detect vascular injury and provides arteriographic assessment with little risk to the patient in a more expeditious fashion than conventional contrast angiography.     

Imaging the postoperative spine

Imaging assessment of the postoperative spine is complex and depends on many factors. Postoperative imaging studies evaluate the position of implants, adequacy of decompression, fusion status, and potential complications. This article provides a review of various imaging techniques, with their advantages and disadvantages, for the evaluation of the postoperative spine. It also gives an overview of normal and abnormal postoperative appearances of the spine as seen via various modalities, with an emphasis on postoperative complications.     

Imaging of the postoperative spine

Spinal instrumentation techniques have expanded dramatically during the past several decades, but the search for the perfect operative approach and fixation system continues. Fixation devices are designed for the cervical, thoracic, lumbar, and sacral segments using anterior, posterior, transverse, videoarthroscopic, and combined approaches. In most cases, bone grafting also is performed, because instrument failure occurs if solid bony fusion is not achieved. Radiologists must understand the operative and instrumentation options. Knowledge of expected results, appearance of graft material, and different forms of instrumentation is critical for evaluating position of implants and potential complications associated with operative approaches and spinal fixation devices.     

Imaging of the postoperative shoulder

Imaging plays an important role in evaluation of the shoulder after surgery. In addition to being familiar with the underlying pathologic condition that leads to surgery, it is just as important to have a general understanding of the surgical procedure because it explains the expected postoperative imaging findings. Identification of postoperative complications with imaging is also improved with this information. This article reviews some of the more common surgeries of the shoulder, including rotator cuff repair, acromioplasty, labral repair, Hill-Sachs impaction fracture and glenoid bone augmentation, acromioclavicular joint repair, and shoulder arthroplasty. Each respective surgical technique is briefly reviewed, followed by discussion and examples of normal postoperative appearances and common postoperative complications. Knowledge of these common procedures and their expected postoperative imaging findings will allow an accurate assessment of complications.     

Imaging of the postoperative hip

A basic understanding of the surgical approach, technique, and potential complications in addition to the types of hardware used is essential in interpreting postoperative imaging of the hip. This article reviews the various surgical approaches to the hip and hardware components in total hip arthroplasty and hip preservation surgery and the potential complications that may arise. The various surgical treatments in the management of acetabular dysplasia and avascular necrosis and the imaging appearances of these on different imaging modalities are also discussed.     

MR imaging of the postoperative knee

Advances in orthopedic and arthroscopic surgical procedures of the knee such as, knee replacement, ligamentous reconstruction as well as articular cartilage and meniscus repair techniques have resulted in a significant increase in the number of patients undergoing knee arthroscopy or open surgery. As a consequence postoperative MR imaging examinations increase. Comprehensive knowledge of the normal postoperative MR imaging appearances and abnormal findings in the knee associated with failure or complications of common orthopedic and arthroscopic surgical procedures currently undertaken is crucial. This article reviews the various normal and pathological postoperative MR imaging findings following anterior and posterior cruciate ligament, medial collateral ligament and posterolateral corner reconstruction, meniscus and articular cartilage surgery as well as total knee arthroplasty with emphasis on those surgical procedures which general radiologists will likely be faced in their daily clinical routine.     

Imaging of the postoperative middle ear

The aim of this article is twofold: (a) to present the principles and the indications of surgical treatment of middle ear pathologies; and (b) to review the imaging findings after middle ear surgery, including the normal postoperative aspects and imaging findings in patients presenting with unsatisfactory surgical results or with suspicion of postoperative complications. This review is intentionally restricted to the most common diseases involving the middle ear: chronic otitis media and otosclerosis. In these specific fields of interest, CT and MR imaging play a very important role in the postoperative follow-up and in the work-up of surgical failures and complications.     

Spiral CT arthrography of the postoperative knee

Computed tomography (CT) has gained multiplanar capability and submillimeter spatial resolution due to the development of spiral acquisition mode and multidetector row technology. Multidetector spiral CT arthrography of the knee is a valuable imaging modality for the assessment of lesions of the meniscus, anterior cruciate ligament (ACL), and articular cartilage. This article presents the value of spiral CT arthrography in the assessment of the postoperative knee with emphasis on the postoperative meniscus, articular cartilage, and ACL graft. This technique may be proposed as an alternative to magnetic resonance arthrography.     

MR imaging evaluation of the postoperative knee

The increased number of patients undergoing arthroscopy or surgery of the knee for sports medicine injuries is leading to increased numbers of patients who require imaging after surgery because of failure to improve, recurrent symptoms, or new injury. As in preoperative patients, magnetic resonance (MR) imaging is the most valuable imaging method for postoperative evaluation of the knee. Surgical changes increase the difficulty of diagnosis of abnormalities in the knee with MR imaging. MR arthrography with direct intraarticular injection of contrast material can help improve evaluation of the postoperative meniscus and possibly help improve evaluation of anterior cruciate ligament grafts in patients after surgery. Recognition of the normal postoperative MR imaging appearance of the structures in the knee and of abnormalities is essential to accurate MR imaging evaluation of these patients.     

Imaging of extra-articular injuries of the knee

Imaging of the extra-articular structures of the knee is important, particularly in overuse injury. Close attention needs to be paid to these areas on magnetic resonance (MR) imaging because misdiagnosis of extra-articular pathology is common, and these lesions are important to consider when planning management. This article details the clinical and radiological aspects of extra-articular injury of the knee with particular emphasis on MR and ultrasound imaging.     

Imaging of the posterolateral corner of the knee

The structures of the posterolateral corner of the knee are increasingly recognized as fulfilling an important role in maintaining knee stability. The posterolateral aspect of the knee is stabilized by a complex anatomy of osseous, myotendinous and ligamentous structures. Unrecognized injuries to this part of the knee are a cause of failure of cruciate ligament reconstruction. This review focuses on the anatomy and common injury patterns involving the posterolateral corner of the knee, with emphasis on magnetic resonance imaging.