Magnetic resonance imaging (MRI) is a useful diagnostic tool in evaluating meniscus pathology in the knee. Data from available literature suggests sensitivity and specificity rates around 90% when compared to the gold standard findings at knee arthroscopy. We sought to evaluate the sensitivity, specificity and precision rate (positive predictive value) of MRI at diagnosing meniscus tears within our unit. A retrospective audit of a total of 79 MRI reports and arthroscopic findings spanning a one year period was carried out. There were 66 positive MRI reports and 13 negative reports. There were 6 false positives 4 false negatives when compared to arthroscopic findings. The sensitivity of MRI for detecting meniscus tears was 93.7% with 60 out of 64 tears detected. All 4 false negatives also had at least grade III osteoarthritic changes at arthroscopy. Specificity was rather low at 60% with MRI reporting 6 tears (false positives) out of 15 patients who had no tears found at arthroscopy. The positive predictive value (precision rate) of MRI detecting tears was 90.9%. This data shows that MRI in our unit has a comparable high sensitivity to that in various literature making it a useful tool at ruling out disease with a negative result in the clinical setting. A more useful parameter in the clinical setting is its high precision rate when faced with a positive result. However, its specificity is much lower than that in most published data. A total of 6 tears on MRI turned out not to be on arthroscopy meaning patients could have been subjected to an avoidable invasive procedure in the absence of any other indication. This highlights the importance of obtaining reports from experienced musculoskeletal radiologists and the need for surgeons to review MRI images and match them to clinical information prior to subjecting patients to surgery

Objectives

Circulating exosomes represent novel biomarkers for multiple diseases. In this study, we investigated whether circulating exosome levels could be used as a diagnostic biomarker for steroid-induced osteonecrosis of the femoral head (ONFH).

Studies on the migration of an implant may be the only way of monitoring the early performance of metal-on-metal prostheses. The Ein Bild Roentgen Analyse - femoral component analysis (EBRA-FCA) method was adapted to measure migration of the femoral component in a metal-on-metal surface arthroplasty of the hip using standard antero-posterior radiographs. In order to determine the accuracy and precision of this method a prosthesis was implanted into cadaver bones. Eleven series of radiographs were used to perform a zero-migration study. After adjustment of the femoral component to simulate migration of 3 mm the radiographs were repeated. All were measured independently by three different observers.

The accuracy of the method was found to be ± 1.6 mm for the x-direction and ± 2 mm for the y-direction (95% percentile). The method was validated using 28 hips with a minimum follow-up of 3.5 years after arthroplasty. Seventeen were sound, but 11 had failed because of loosening of the femoral component. The normal (control) group had a different pattern of migration compared with that of the loose group. At 29.2 months, the control group showed a mean migration of 1.62 mm and 1.05 mm compared with 4.39 mm and 4.05 mm in the failed group, for the centre of the head and the tip of the stem, respectively (p = 0.001). In the failed group, the mean time to migration greater than 2 mm was earlier than the onset of clinical symptoms or radiological evidence of failure, 19.1 versus 32.2 months (p = 0.001) and 24.8 months (p = 0.012), respectively.

EBRA-FCA is a reliable and valid tool for measuring migration of the femoral component after surface arthroplasty and can be used to predict early failure of the implant. It may be of value in determining the long-term performance of surface arthroplasty.

There is no diagnostic, non-invasive method for the early detection of loosening after total hip arthroplasty. In a pilot study, we have analysed two serum markers of bone remodelling, procollagen I C-terminal extension peptide (PICP) and cross-linked N-terminal telopeptide (NTx), as well as the diagnostic performance of NTx for the assessment of osteolysis. We recruited 21 patients with loosening (group I), 18 with a well-fixed prosthesis (group II) and 17 at the time of primary arthroplasty for osteoarthritis (OA) (group III). Internal normal reference ranges were obtained from 30 healthy subjects (group IV).

The serum PICP level was found to be significantly lower in patients with OA and those with loosening, when compared with those with stable implants, while the NTx level was significantly increased only in the group with loosening, suggesting that collagen degradation depended on the altered bone turnover induced by the implant. This hypothesis was reinforced by the finding that the values in the pre-surgery patients and stable subjects were comparable with the reference range of younger healthy subjects.

A high specificity and positive predictive value for NTx provided good diagnostic evidence of agreement between the test and the clinical and radiological evaluations. The NTx level could be used to indicate stability of the implant. However, further prospective, larger studies are necessary.