To evaluate the inflammatory involvement of lumbar interspinous bursae in patients with polymyalgia rheumatica (PMR) using magnetic resonance imaging (MRI).
Ten consecutive, untreated new patients with PMR and pain in the shoulder and pelvic girdles were investigated. Seven patients with spondyloarthritis (4 with psoriatic spondyloarthrits, one with entheropatic spondyloarthritis, and 2 with ankylosing spondylitis) as well as 2 patients with spinal osteoarthritis and 2 patients with rheumatoid arthritis with lumbar pain served as controls. MRI of lumbar spine was performed in all PMR patients and controls. Nine patients (5 PMR patients and 4 controls) also had MRI of the thoracic spine.
MRI evidence of interspinous lumbar bursitis was found in 9/10 patients with PMR and in 5/11 controls. A moderate to marked (grade ≥2 on a semiquantitative 0-3 scale) lumbar bursitis occurred significantly more frequently in patients with PMR than in control patients (60% vs. 9%, p=0.020). In most of the patients and controls lumbar bursitis was found at the L3-L5 interspaces. Only 2 patients had bursitis at a different level (one patient had widespread lumbar bursitis, and one control at L2-L4). No interspinous bursitis was demonstrated by MRI of the thoracic spine in patients and controls.
Inflammation of lumbar bursae may be responsible for the low back pain reported by patients with PMR. The prominent inflammatory involvement of bursae including those of the lumbar spine supports the hypothesis that PMR may be a disorder affecting predominantly extra-articular synovial structures.