Trans-arterial embolization (TAE) is a minimally invasive treatment, recently been deployed to treat various chronic painful inflammatory musculoskeletal (MSK) conditions. Through selective embolization, TAE inhibits the abnormal hypervascularity that contributes to the catabolic and inflammatory. There have been several studies suggesting that TAE has an excellent safety and efficacy profile and demonstrates promising clinical results, including decreased pain and improved function and quality of life after treatment. The authors review and introduce underlying theory, embolic agent selection, and clinical evidence for TAE in the treatment of chronic MSK pain refractory to standard therapy.

chronic musculoskeletal pain ； interventional radiology ； trans-arterial embolization

Trans-arterial embolization (TAE) is an established minimal invasive procedure used to occlude target blood vessels by infusing an embolic agent for a wide variety of conditions. It is mostly used to control bleeding or to decrease the size of hyper-vascular tumors through selective “embolization” of small arteries [1-5].

Recently, TAE techniques have been applied to treat various chronic painful infl ammatory musculoskeletal (MSK) conditions including osteoarthritis, synovitis, tendinopathy, enthesopathy, and sports injuries for the patients who were refractory to conservative treatments including oral medication, physical therapy, and local injection for at least 3 months. The mechanism by which TAE achieves pain relief is not completely understood. Based on the literature, abnormally chronic inflamed or hyper-vascular tissues stimulating angiogenesis, and the abnormal angiogenetic neovessels, accompanied by pain-related nerve fibers ingrowth have been identified [6-8]. Possible mechanisms of TAE for pain include: (1) The embolization of angiogenesis may cause damage to or decreased numbers of unmyelinated sensory nerves, resulting in reduced pain perception. (2) Neovessels are a conduit for infl ammatory cells to achieve their target. The occlusion of blood fl ow may lead to pain relief by decreasing the number of infl ammatory cells reaching the MSK structures [9].

The embolic agents in MSK embolotherapy including imipenem/cilastatin (IPM/CS) suspension, an antibiotic that has been applied as a temporary embolic agent, and the embolic characteristics and possible mechanisms of action in vitro and in vivo are also elucidated [9-11]. Permanent embolic agents are also used in genicular artery embolization [12]. It was found that while both agents appeared to be safe, minor procedure-related complications, such as skin changes and paresthesia in the region of embolization, were more likely to occur with permanent embolic agent [13,14]. Other temporary embolic agents including gelatin microsphere may also be candidates for TAE of MSK conditions, whereas under investigation [9].

Okuno et al. [15] were the first group to describe their successful treatment experience of TAE on tendinopathies and enthesopathies, published in 2013. Since then, plenty of studies have reported on the role of TAE as a potential pain management on various chronic inflammatory MSK conditions. Taguchi et al. [16] demonstrated the effect of TAE on the findings of angiography, histopathology, and physical activity using a rat model of frozen shoulder. Randomized control trials and multiple systemic reviews were published in recent years, predominately knee osteoarthritis (Figure 1), and adhesive capsulitis of shoulder (Figure 2) [13,17-22].

In a recent systematic review and meta-analysis study by Kim et al. [22], the result revealed that TAE for chronic inflammatory joint pain is technically feasible and safe, with technical success rates as high as 95.8% and no major adverse events. The pooled mean difference of pain scores at 1 week was 3.1. At 1, 3, and 6 months, the differences were 4.0, 4.2, and 5.1, respectively; at 1 year the difference was 5.5. The pooled estimates of range of motion increases in anterior elevation and abduction at 6 months after TAE among the shoulder embolization groups were 55.6° and 64.7°, respectively [22]. More studies, especially randomized placebo-controlled studies, are necessary to confirm the other MSK indication, safety, and efficacy. Regenerative injection therapy with different agents, including dextrose, platelet-rich plasma, bone marrow aspirate concentrate, stromal vascular fraction, and dehydrated human amniochorion membrane are also reported to achieve effective pain relief for chronic MSK conditions [23,24]. Nerve block and rehabilitation also have their roles in pain relief and physical function improvement. Combination of different therapy may be future application, and more research is warranted for further exploration of efficacy and mechanism of combination use of different therapeutic treatment.

Figure 1. A 69-Year-Old Woman With Severe Left Medial Knee Pain, Tenderness and Functional Limitation for 1 Year, Diagnosed Knee Osteoarthritis

(A) Abnormal angiogenesis (black arrow) located around medial upper knee joint performed from descending genicular artery. (B) Elimination of the neovessels after embolization (white arrow). Subcutaneous metallic marker for label of the location of pain (empty arrows). After embolization, the pain, stiffness, and range of motion all improved and persisted for more than 6 months.

Figure 2. A 56-Year-Old Woman With Severe Shoulder Pain, Stiffness, and Range of Motion Limitation for 1 Year, Diagnosed Adhesive Capsulitis

(A) Abnormal angiogenesis (black arrow) located at the rotator interval performed from thoracoacromial artery. (B) Elimination of the neovessels after embolization (white arrow). After emboliza- tion, the pain, stiffness, and range of motion all improved, and fully recovered after following rehabilitation.

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