Magnetic resonance imaging of joint arthroplasty

Rupture of the ilio-psoas tendon after a total hip arthroplasty: an unusual cause of radio-lucency of the lesser trochanter simulating a malignancy

Avulsion fracture or progressive radiolucency of lesser trochanter is considered a pathognomic finding in patients with malignancies. Although surgical release of the iliopsoas tendon may be required during a total hip arthroplasty (THA), there is no literature on spontaneous rupture of the ilio-psoas tendon after a THA causing significant functional impairment. We report here such a case, which developed progressive radiolucency of the lesser trochanter over six years after a THA, simulating a malignancy. The diagnosis was confirmed by MRI. Because of the chronic nature of the lesion, gross retraction of the tendon into the pelvis, and low demand of our patient, he was treated by physiotherapy and gait training. Injury to the ilio-psoas tendon can occur in various steps of the THA and extreme care should be taken to avoid this injury. Prevention during surgery is better, although there are no reports of repair in the THA setting. This condition should be considered in patients who present with progressive radioluceny of the lesser trochanter, especially in the setting of a hip/pelvic surgery. Awareness and earlier recognition of the signs and symptoms of this condition will aid in diagnosis and will direct appropriate management.

Magnetic resonance imaging assessment of chondral lesions and repair

Standardized, validated magnetic resonance imaging sequences that are sensitive for articular cartilage are available for clinical use in magnetic resonance imaging units. Whereas two-dimensional sequences are helpful in the assessment of repair morphology, three-dimensional sequences with isotropic voxels measure cartilage volumes and provide an accurate assessment of fill following repair. Protocols should be modified so that sequences are not limited by instrumentation. The addition of quantitative magnetic resonance imaging techniques provides an objective assessment of repair-tissue biochemistry as well as of the tissue at the peripheral integration with the host hyaline cartilage.

How are wear-related problems diagnosed and what forms of surveillance are necessary?

Prospective, randomized clinical wear studies have shown significant wear reduction when highly cross-linked, e-beamed, melted polyethylene was compared with conventional polyethylene sterilized by gamma irradiation in air. More complete assessment of wear-induced osteolysis in the general total hip arthroplasty patient population must rely on registries with follow-up of large populations of patients through radiographic evaluation of wear-related factors, such as suboptimal placement of the implant components, osteolytic defects, and aseptic loosening. Follow-up radiographs should be obtained in the early postoperative period and at 1, 5, and 10 years postoperatively, and then every 1 to 5 years, thereafter depending on radiographic findings of osteolysis and its progression. When pathologic findings are present, further examinations, such as oblique Judet views and magnetic resonance imaging (MRI) with artifact minimization should be considered to provide a better determination of the extent of the osteolysis. Because conventional radiographs underestimate the prevalence and extent of osteolysis in many instances, diagnosis and surveillance should be performed with radiographic edge detection, spiral computed tomography (CT), MRI, radiostereometric analysis, and quantitation of wear and osteolysis, including bone and soft-tissue lesions. Helical CT has demonstrated excellent specificity in identifying and quantifying the extent of osteolysis. MRI can more accurately localize both osseous and soft-tissue particulate disease, and detect granuloma and compression on adjacent nerves and vessels.

What are the guidelines for the surgical and nonsurgical treatment of periprosthetic osteolysis?

Periprosthetic osteolysis is most often diagnosed by plain radiographs. Because these radiographs routinely underestimate the extent of the lesion, three-dimensional imaging should be used early in the evaluation process to confirm the presenting extent of disease. If the osteolytic process is asymptomatic, scheduled regular follow-up should be instituted until the lesion can be confirmed to be stable or until the decision is made to proceed with surgery. Nonsurgical management with pharmacologic agents has not proved to be effective. If surgery is contemplated, a three-dimensional evaluation with magnetic resonance imaging or helical computed tomography can assist in preoperative planning. Surgical intervention requires complete débridement of the lesional membrane and removal of the wear-generator--with or without component removal and with or without bone grafting, depending on the individual circumstances. A standardized follow-up evaluation mechanism for all patients should be a part of total joint arthroplasty management.

The imaging appearances of metallosis

Metallosis is an uncommon condition in which there is infiltration of periprosthetic soft tissues and bone by metallic debris resulting from wear of joint arthroplasties. It is often associated with significant osteolysis; therefore the identification of metallosis is an indication for revision arthroplasty. The radiographic, CT and MRI features of metallosis in a 63-year-old man who presented 16 years post-arthroplasty are described in this case report.

Current applications of advanced cross-sectional imaging techniques in evaluating the painful arthroplasty

Patients with a painful arthroplasty can present a clinical diagnostic dilemma. Aspirates are often negative for infection and alignment of the prosthesis on conventional radiographs is usually satisfactory. These patients can have a myriad of soft tissue as well as osseous pathologies, which may be clinically unsuspected or radiographically occult. The ability of advanced cross-sectional imaging to diagnose osseous and soft tissue injuries has been well documented, but applications to arthroplasty imaging are often limited by regional metallic artifacts. Adjustment of standard imaging parameters can make CT and MR imaging useful adjuncts in imaging the painful arthroplasty, especially in the setting of normal radiographs. Ultrasound can be used to evaluate the periprosthetic soft tissues and provide a real-time method of evaluating the dynamic relationship of the periprosthetic soft tissues to the arthroplasty components, and it also can be used as a guide for diagnostic and therapeutic interventions.