Evaluation of Pain Level Reduction After Low-dose Radiation in Symptomatic Facet Joint Arthritis

The goal of this clinical trial is to compare low-dose radiation therapy (LDRT) with intra-articular steroid injections in participants suffering from chronic lower back pain as cause of facet joint arthritis (FJA).

The main question\[s\] it aims to answer are:

* Is LDRT non-inferior to intra-articular steroid injections in terms of pain reduction
* Is there a difference in long-term pain reduction between LDRT and intra-articular steroid injections Participants will be randomly assigned to one of the two treatment groups.

However, there has been no published study providing scientific evidence by prospective randomized data on the effect of LDRT in patient suffering from facet osteoarthritis. LDRT seems a viable treatment method with anti-inflammatory potential and possible long-lasting benefit in pain resolution for patients with facet joint arthritis (FJA), which can prevent from an ultimate surgical treatment.

The rationale of this trial is to generate scientific evidence that LDRT is an alternative non-invasive treatment option for FJA, whose primary outcome "pain reduction" is equivalent to the most common treatment intra-articular steroid injections.

Eligibility Criteria:
Inclusion Criteria:

* Patients with degenerative symptomatic facet joint osteoarthritis confirmed by MRI (lumbar spine) and standing X-ray
* Patients who underwent treatment for facet joint syndrome at the Dept. of Orthopaedic Surgery and Traumatology of KSA (Kantonsspital Aarau) or Dept. of Rheumatology of KSA or Dept. of Neurosurgery of KSA, onset of symptoms and treatment with pain medication and physiotherapy
* The informed consent form for participation in the study was signed
* Stated willingness to comply with all study procedures and availability for the duration of the study
* Age ≥ 45 years
* Karnofsky Performance Status (KPS) ≥ 80 %
* Ability to take steroids and bridge or pause NOAC (New oral anticoagulants) / Marcoumar
* Show a positive Tracer-Uptake in the SPECT-CT in max. 4 facet joints of the lumbar spine (regardless of radiologic changes in MRI or CT)
* Immediate ≥ 70% pain reduction after 1 positive diagnostic infiltration of the suspected facet joint(s)
* Negative middle-/long-term effect (4-12 weeks after first steroid injection, defined as "NRS 5-10 at 4-12 weeks")

Exclusion Criteria:

* Any previous infiltration therapy in the suspected spine region (+/- 3 segments) within the last 3 years
* Any previous radiotherapy, radiofrequency ablation, other pain modulating interventions (e.g. thermos/-cryoablation or spinal cord stimulators) or surgery in the suspected spine region (+/- 3 segments)
* Prior or concurrent malignancy (≤ 5 years prior to enrolment in study) except: nonmelanoma skin cancer, cervix carcinoma in situ, prostatic intraepithelial neoplasia) Contraindications to radiotherapy (for example connective tissue disorders such as scleroderma)
* Any psychological, familial, sociological or geographical condition potentially hampering compliance with the study protocol and follow-up schedule; those conditions should be discussed with the patient before registration in the trial
* Pregnancy, desire to have own children or lactation during study participation.