MR Imaging Of Cartilage At 7 Tesla -Viscosupplementation With HYMOVIS® For The Management Of Osteoarthritis Of The Knee: A Prospective Cohort Study

Background Hyaluronan acid (HA) viscosupplementation is usually employed for conservative management of early knee osteoarthritis (OA). A new HA-based product, Hymovis®, was essayed in comparison with the most used molecules with regard to several rheological features. To date a reproducible and effective method to asses HA effects on articular cartilage still remains to develop. To detect articular cartilage loss or damage, a Magnetic Resonance Imaging (MRI) of the knee can be performed. Because of the small thickness of articular cartilage and long acquisition time necessary to obtain high resolution images, the use of the ultra high field (UHF) magnets can be advantageous. So the employment of a 7 Tesla (T) magnet represents a possibility to study in vivo articular cartilage. The highest resolution of 7T imaging could allow to detect morphological data, such as initial and limited cartilaginous defects, but also and above all the structural alterations with greater accuracy and shorter acquisition times than the lower magnets field. Objectives The purpose of this study is to evaluate the efficacy of HA viscosupplementation in the management of early OA of the knee and its effect on patients symptoms and articular cartilage. Study Design & Methods 14 patients (20 knees), 7 males and 7 females, were prospectively enrolled in the present study and treated by 2 consecutive injections of Hymovis HA at one week interval, from 2017 April the 1st to 2018 May the 31st and received target knee MRI 3 times during this study. All MRI procedures were obtained with an UHF up to 7T and all Patients were clinically evaluated 5 times during the follow-up, from Visit(V)0 to V4. Knee MRIs were performed at V1, before the first HA injection; at V3, after 45 days from the second HA injection; and at V4, after 180 days from the second HA injection. Clinical evaluations consisted of WOMAC index recorded at V1 and V4, and VAS recorded at V0,V1, V3 and V4.Main inclusion criteria were: age between 40 and 80 years old, BMI<40, symptomatic and radiological knee OA (K&L grade II or III) and mean knee pain at rest > 40 mm (VAS). Results We report good clinical outcomes with statically significant reduction in symptoms with an increased knee and global activity functions.The mean WOMAC improved from 28,5 at V1 to 11,9 at V4, while mean VAS values improved from 59,3 at V0 to 11,9 at V4. To date we just report preliminary results related to MRI acquisitions. We recorded an increasing in cartilage volume and thickness in the most of the patients with fibrous tissue formation in some cartilage defects, but we didn’t found MRI signals referable to cartilage regeneration. Conclusions Hymovis HA viscosupplementation showed good clinical outcomes and the preliminary MRI results reported confirm the possibility to employ 7T magnets to evaluate early changes in cartilage structure in vivo, even if the use of HA viscossuplementation doesn’t seem to modify cartilage morphology over the time.