Extended Therapeutic Effect of 35kDa Hyaluronan Fragment Injection in Patients With Chronic Pain Caused by Myofascial Pain Syndrome

Inclusion Criteria: * Male and female, aged 18-65 years old ; * suffering from muscle strain, sprain, fall, wind and other diagnosed as myofascitis in patients with chronic back pain; * the pain reported by the subject should reach level 3 or higher on the digital rating scale of 0-10 ( 0 means no pain, 10 represents the strongest pain imaginable ); * the mental state is good, and the pain level can be evaluated independently; * be able to cooperate with the treatment independently and sign a written consent. Exclusion Criteria: * Previous severe trauma with permanent musculoskeletal dysfunction; * symptomatic lumbar disc herniation with neurological deficits; * specific spinal diseases, including rheumatoid arthritis, ankylosing spondylitis, and osteoporosis; * diagnosed with mental illness; * agree not to sign the written consent; * pregnant, lactating or fertile women; * currently participating ( or participating in the past 30 days ) in research-based treatment or equipment trials.