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To evaluate MRI as a problem-solving tool for patients with an unexplained failed total hip replacement following conventional radiological assessment. Patients’ informed consent was obtained in all cases. Institutional review board approval was obtained. Twenty-eight patients with unexplained failed total hip replacements following conventional radiological assessment underwent additional MR imaging with an optimised turbo-spin echo sequence. Images were reviewed by two musculoskeletal radiologists by consensus and compared with findings at surgery, or following response to image-guided intervention or clinical follow-up. Of the 28 patients, MRI revealed an unsuspected diagnosis explaining the cause of prosthesis failure in 15 patients. In eight of 15 patients in this group, subsequent minimally invasive image-guided intervention obviated the need for revision total hip replacement. No cause for prosthesis failure was identified in 13 patients. MRI may be successfully undertaken in patients following total hip replacement, and, when performed, it frequently leads to an unsuspected diagnosis, allowing informed patient treatment. In this study it allowed the identification of an unsuspected diagnosis in over 50% of cases.

Bipartite patella is a known cause of anterior knee pain. Our purpose was to detail the magnetic resonance imaging (MRI) features of bipartite patella in a retrospective cohort of patients imaged at our institution.MRI exams from 53 patients with findings of bipartite patella were evaluated to assess for the presence of bone marrow edema within the bipartite fragment and for the presence of abnormal signal across the synchondrosis or pseudarthrosis. Any other significant knee pathology seen at MRI was also recorded. We also reviewed 400 consecutive knee MRI studies to determine the MRI prevalence of bipartite patella.Of the 53 patients with bipartite patella 40 (75%) were male; 35 (66%) had edema within the bipartite fragment. Of the 18 with no edema an alternative explanation for knee pain was found in 13 (72%). Edema within the bipartite fragment was the sole finding in 26 of 53 (49%) patients. Bipartite patella was seen in 3 (0.7%) of 400 patients.In patients with bipartite patella at knee MRI, bone marrow edema within the bipartite fragment was the sole finding on knee MRI in almost half of the patients in our series.