MRI in knee osteoarthritis. Application in diet intervention

Abstract

This thesis examines two main hypotheses: 1. Obese knee osteoarthritis (KOA) patients can achieve symptomatic improvements following diet intervention regardless of their level of structural damage and overall joint malfunctioning: 2. Rapid weight-loss in obese patients with KOA will lead to improvements in KOA related pathology that can be assessed and evaluated by MRI. Data for the studies were obtained from obese KOA patients who were recruited for a 16 week diet intervention trial, the CAROT-trial (ClinicalTrials.gov identification no.: NCT00655941). Inclusion criteria were age ≥ 50 years, BMI ≥ 30 kg/square metro plus symptomatic and verified KOA. Patients underwent a 16 weeks dietary programme with formula products and counselling. Baseline and week 16 assessments included clinical examinations, MRI and CR of the most symptomatic knee, muscle strength tests, gait analyses, blood samples and collection of patient-reported outcomes with a variety of generic and specific health status questionnaires. MRI scans were graded by the BLOKS and CR was analysed by measuring the mJSW and grading the knee as described by KL. 388 possible subjects were pre-screened, 192 were enrolled. Following the 16 weeks diet intervention 175 patients remained in the study. 187 (97%) MRI scans were completed at baseline, 172 (98 %) MRI scans obtained at week 16 and this left the study with 169 (97%) patients with complete MRI datasets at week 16. No statistical significant differences were detected between baseline characteristics of all the initially included patients (n = 192) and the 169 patients included in the per protocol analyses performed in study III (p < 0.05). In order to apply BLOKS, an extensive MRI scoring system, in study II and III we examined the inter- and intra-observer reliability of the various BLOKS items in study I. Results showed that our assessment team performed as described in the original study defining BLOKS and that the patients in the CAROT-trial were graded as expected. In study II we investigated the impact of diet intervention on KOA symptoms whatever the patient's individual level of joint damage and malfunctioning, and the explanatory variables included high-field MRI, radiographs, and muscle strength in m. quadriceps as well as measurements of the knee-joint alignment axis. Results showed that diet intervention resulted in a symptomatic relief in obese KOA patients, irrespective of their level of structural damage, measures of joint malfunctioning and general pre-study patient characteristics. The final study examined whether or not weight-loss had an immediate impact on MRI assessed BMLs. The results showed that changes seen in the total TF sum of BML scores and maximal BML scores did not differ between patients achieving a major weight loss (> 10%) and those who did not. Furthermore, changes in clinical symptoms and BML scores were not associated. The limitations of this thesis were that the MRI analyses were based on single determinations of MRI variables and that the studies did not assess between scan reliability. The MRI protocol for this study did not include all the recommended sequences for BLOKS. Analysing BMLs with the use of only coronal STIR and T1w sequences is considered adequate for a reasonable assessment of the tibial and femoral bones. However, we recognize the limitations this strategy withholds in terms of correctly assessing BMLs located at the margins of our slices when only having a single plane view included in our MRI protocol. Due to an inadequate coverage we did not analyse BMLs in patella, and this confined the thesis to only study changes in the tibial and femoral bones. BLOKS contains separate scores for effusion and synovitis and we have assessed all MRI scans according to this discrimination well knowing that this procedure is biased and that a recent paper has proposed the combination of the two scores. MRI technology allows for an excellent discrimination and delineation of synovitis and synovial effusion by performing MRI with I.V. gadolinium and post-contrast T1 FS images, but due to extensive requirements and longer scans times for such examinations we proceeded with our, in this matter, suboptimal MRI protocol. The optimal assessment of KOA would be achieved by performing three radiographic views, posteroanterior, lateral and skyline, but for this study we chose a radiographic protocol only including the first two mentioned as this procedure was somewhat similar to the routine examination for KOA applied on a daily basis at our Department of Radiology. The results of this thesis support existing guidelines suggesting that diet intervention in obese KOA patients is beneficial for symptomatic improvements. The new information from the thesis is that improvement in clinical symptoms is possible for the majority of patients, independent of their pre-study level of structural damage and measures of joint malfunctioning. The present results also demonstrated that a rapid weight-loss had no association to changes in BML scores and established that changes observed in symptoms and BML scores, following a 16 weeks diet intervention, were not related.