Objectives: To determine the pathological features of sacroiliitis and the expression of cytokines in joint biopsy samples in patients with ankylosing spondylitis (AS) and to investigate the variance in single photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI) scans, and the response to intra-articular injection of anti-tumour necrosis factor (TNF) therapy.
Methods: Sixteen patients with AS were given CT-guided intra-articular injections of etanercept at 0, 4, and 8 weeks (25 mg per dose). Pathological features of sacroiliitis were observed with light microscopy and immunohistochemistry. Expression of cytokines in joint biopsy samples was estimated by reverse transcription polymerase chain reaction (RT-PCR). Imageological changes in sacroiliitis were observed by SPECT/CT and MRI. All patients were followed up clinically.
Results: In all 16 patients who received intra-articular etanercept, sacroiliac joint (SIJ) region of interest (ROI) mean values determined by SPECT improved significantly after 8 weeks (p < 0.05). Bone marrow hydropsia and fatty deposition detected on MRI were relieved significantly after 8 weeks (p < 0.05). In eight patients the expression of TNFalpha and transforming growth factor (TGF)-beta mRNA in joint tissue decreased significantly after 8 weeks (p < 0.05). The frequency of synovitis, enthesitis, chondritis, subchondral bony plate destruction, and bone marrow inflammation decreased significantly, along with the inflammatory cell index (p < 0.05). Participants showed significant clinical improvement after 8 and 12 weeks (p < 0.001) in the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score but no significant difference in spondylitis and periphery arthritis (p > 0.05). This mode of treatment had no notable adverse events.
Conclusions: This study has shown that intra-articular injection of etanercept in SIJ can improve joint function. It has a satisfactory safety profile and is cost-effective. This mode of treatment is most beneficial in local arthropathy of recent onset.