Relationship of plasma metal ions and clinical and imaging findings in patients with ASR XL metal-on-metal total hip replacements.

BACKGROUND: Plasma metal ion levels are commonly used in the postoperative follow-up evaluation of patients who have had a metal-on-metal hip arthroplasty. However, the relationship between these levels and clinical and imaging findings is not well known. METHODS: We evaluated 156 consecutive patients who received a unilateral ASR XL total hip replacement. Patients presented, regardless of symptoms, in response to a voluntary recall of the hip replacement by the manufacturer and were assessed with regard to the presence and type of symptoms and plasma cobalt-chromium levels. In addition, radiographic and magnetic resonance imaging studies were performed and analyzed. RESULTS: Eighty patients were asymptomatic, and seventy-six patients were symptomatic. The median cobalt level was 1.8 ppb, and the median chromium level was 1.0 ppb (at or below measurement threshold). Pseudotumors that could be detected on magnetic resonance imaging were seen in 69% (107) of 156 patients, and radiographic osteolysis was evident in 7% (eleven patients). At a threshold of 5 ppb, no association was detected between abnormal metal ion levels and patient symptoms, prosthetic femoral head size, or acetabular cup inclination. An abnormal cobalt level was significantly associated with the presence of periprosthetic lucency on radiographs and pseudotumor on magnetic resonance imaging (p < 0.05). An abnormal chromium level showed a similar pattern, but the relationships did not reach significance. Both abnormal plasma cobalt and chromium levels were associated with larger sizes of pseudotumor when present (p < 0.05). CONCLUSIONS: In our sample, with a threshold of 5 ppb, abnormal plasma metal ions were associated with larger sizes of pseudotumors when present, but were not predictive of patient symptoms. Abnormal plasma cobalt levels have a significant association with periprosthetic lucency and presence of pseudotumor. Plasma chromium shows a similar pattern of association with lucency and presence of pseudotumor, although the relationships were not significant. Metal ion analysis should be used in conjunction with clinical and imaging evaluation and not as a sole indirect screening test when evaluating patients following metal-on-metal hip arthroplasty.

Metal-on-metal total hip arthroplasty: do symptoms correlate with MR imaging findings?

PURPOSE: To determine the prevalence of magnetic resonance (MR) imaging abnormalities after metal-on-metal total hip arthroplasty and to determine whether presence of symptoms correlates with findings at MR imaging. MATERIALS AND METHODS: This HIPAA-compliant study was approved by the institutional review board, and informed consent was waived. MR imaging was performed with conventional sequences and a 1.5-T clinical imager in 192 hips (174 patients) evaluated during a 15-month period. Two observers retrospectively reviewed the images for the presence and size of pseudotumor, communication with the pseudocapsule, wall thickness, synovial hypertrophy, compartmentalization, solid components, foci of wall susceptibility, osteolysis, bone marrow edema, abductor muscle or tendon abnormality, and Anderson MR grade (normal, infection, or varying severity of metal-on-metal disease). These findings were compared between asymptomatic and symptomatic patients by using the Fisher exact test or the Wilcoxon-Mann-Whitney test, as appropriate. RESULTS: Prevalence of pseudotumors per patient and per hip was 69% (120 of 174 patients, 132 of 192 hips). Bone marrow edema (present in six asymptomatic patients and 19 patients with pain, P < .01) and tendon tearing (present in five asymptomatic patients and 13 patients with pain, P < .05) were predictors of pain. Presence of symptoms was not correlated with presence (P = .4151) or size of pseudotumors. Anderson MR grade binarized into normal versus abnormal showed moderate agreement between readers (κ = 0.439) but was also not correlated with symptoms (P = .6648). CONCLUSION: The presence of bone marrow edema and abductor tendon tears but not the presence or size of pseudotumor was associated with patient pain.

New thoughts on the origin of Pellegrini-Stieda: the association of PCL injury and medial femoral epicondylar periosteal stripping.

OBJECTIVE: For the past 100 years, Pellegrini-Stieda disease has been described as calcification and ossification within the tibial collateral ligament, although these typical radiographic findings are often located more superior than the most proximal extent of the ligament. In this article, we demonstrate four magnetic resonance imaging cases of knee trauma with complete posterior cruciate ligament tear or avulsion, each demonstrating that injury to the medial collateral ligamentous complex can involve significant stripping of the tissue proximal to the medial epicondyle. CONCLUSION: Classic radiographic findings of Pellegrini-Stieda calcifications can be caused by stripping of the femoral periosteum proximal to the femoral attachment of the tibial collateral ligament, which appears to be associated with a complete posterior cruciate ligament injury.

Medial collateral ligament tear entrapped within a proximal tibial physeal separation: imaging findings and operative reduction.

Entrapped soft tissues such as periosteum and tendons have been described within joints and physeal fractures in the literature and frequently result in irreducible fractures and posttraumatic growth disturbances. We believe this case represents a novel presentation of acute, preoperative, magnetic resonance (MR) imaging diagnosis of a torn medial collateral ligament entrapped within a proximal tibial physeal separation. This case is presented with MR imaging and operative correlation of the findings.