These histological findings support the possibility of a lymphocyte-dominated immunological response. Although the prevalence of this reaction is low, the persistence or early reappearance of symptoms, including a marked joint effusion and the development of osteolysis, after primary implantation may suggest the possibility of such a reaction.

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There is some evidence for the efficacy of acupuncture in chronic low-back pain (LBP), but it remains unclear whether acupuncture is superior to placebo. In a randomized, blinded, placebo-controlled trial, we evaluated the effect of traditional acupuncture in chronic LBP. A total of 131 consecutive out-patients of the Department of Orthopaedics, University Goettingen, Germany, (age=48.1 years, 58.5% female, duration of pain: 9.6 years) with non-radiating LBP for at least 6 months and a normal neurological examination were randomized to one of three groups over 12 weeks. Each group received active physiotherapy over 12 weeks. The control group (n=46) received no further treatment, the acupuncture group (n=40) received 20 sessions of traditional acupuncture and the sham-acupuncture group (n=45) 20 sessions of minimal acupuncture. Changes from baseline to the end of treatment and to 9-month follow-up were assessed in pain intensity and in pain disability, and secondary in psychological distress and in spine flexion, compared by intervention groups. Acupuncture was superior to the control condition (physiotherapy) regarding pain intensity (P=0.000), pain disability (P=0.000), and psychological distress (P=0.020) at the end of treatment. Compared to sham-acupuncture, acupuncture reduced psychological distress (P=0.040) only. At 9-month follow-up, the superiority of acupuncture compared to the control condition became less and acupuncture was not different to sham-acupuncture. We found a significant improvement by traditional acupuncture in chronic LBP compared to routine care (physiotherapy) but not compared to sham-acupuncture. The trial demonstrated a placebo effect of traditional acupuncture in chronic LBP.

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