Efficacy of a Locoregional Anesthesia Technique During Shock Wave Therapy

Overview

Plantar fasciitis and the chronic Achilles tendinopathy are the most common causes of heel pain. The term "plantar fasciitis" implies an inflammatory condition by the suffix "itis". However, various lines of evidence indicate that this disorder is better classified as "fasciosis" or "fasciopathy", as heel pain associated with degenerative changes in the fascia and atrophy of the abductor minimi muscle. High energy shock wave therapy (HESWT) has been proposed as a potential method of treating patients with chronic disease without the need to stop weightbearing. Often a crucial complication of HESWT is the appearance of pain with the subsequent interruption of the procedure. The consequences are a reduced patient compliance, need of a deep sedation and more sessions for the treatment. Frequently, topic anesthesia (TA) (as EMLA) is applied during the therapy to decrease the pain HESWT-induced and enable sham treatment. Multiple publications focused on the evaluation of a clinically relevant effect of shock wave application on plantar heel pain, either of HESWT, applied in a single session with local or regional anesthesia or of low energy HESWT, applied repetitively without local anesthesia. Rompe JD and colleagues have demonstrated that the therapeutic success rate of HESWT with TA is significantly smaller than without TA even after 3 months. Probably, the use of anesthetic topically applied can reduce the efficacy of HESWT for increased impedance. To date, many patients interrupted the HESWT for moderate-severe pain. Consequently, this therapy, which generally is administered in three sessions, required a prolongation of procedure up to six sessions.The clinical application of Posterior Tibial nerve block (already widely used in operating room) during HESWT applied in Orthopedic Day Hospital could offer the possibility to minimize the patient discomfort and to give the therapeutic doses just in few HESWT sessions, reducing the hospital access of outpatients for the treatments and the costs related to prolonged treatment caused by pain. Furthermore, this anesthetic approach could make patients tolerate majorated doses of HESWT in few sessions, with high effectiveness of procedure after several months.

The aim of this pilot prospective observational study is to allow outpatients with chronic Achilles tendinopathy and plantar fasciitis to reduce the pain during HEWST. The study will be focused on the evaluation of a posterior tibial nerve block efficacy in patients who discontinued the first application of HESWT due to surge of moderate-severe pain. Objectives of the study Primary objective The primary objective of the study is to observe a 40% reduction in Numerical Rating Scale (NRS) from baseline (T0) to T1 during HESWT. Secondary objectives: evaluation of the number of patients that are able to complete a single session with Posterior tibial nerve block (usually, without Posterior tibial nerve block, 40% of patients can not complete the session); evaluation of the number of sessions required to complete successfully the treatment (usually, without Posterior tibial nerve block, the number of sessions required to complete successfully the treatment is 6); evaluation of the efficacy of HESWT (American Orthopedic Foot and Ankle Society Score - AOFAS, performed 1 month from the end of treatment). Design of the study This is an observational, pilot, prospective, cohort study. It will be conducted in Orthopedic Day Hospital Ward of "Fondazione-Policlinico Universitario A. Gemelli IRCCS" of Rome. The planned duration of the study is 6th months and the proposed sample size is N:21. Materials and Methods The enrollment starts after the patient interrupt his/her first HESWT treatment (T0) because the pain is unbearable with NRS\>5. Before the second HESWT session (T1) patients will receive the posterior tibial nerve block (PTNB) under ultrasound control. This anesthetic procedure will be repeated for every subsequent HESWT session. After each treatment, the patient will be monitored in Orthopedic Day hospital ward for about 2 hours or until complete sensitive recovery. At the end of each session the patient will be asked to express his/her pain intensity using the NRS. The anesthetic procedure With the patient lying supine and the foot externally rotated, an expert anesthesiologist will perform the PTNB with echo guided, finding the posterior tibial nerve between the middle and the distal third of the leg, about 6-8 cm proximally to the tibial malleolus. Once the nerve will be identified, the needle (70 millimeters long, 22 gouge, UPC Polymedic) will insert in-plain and after careful aspiration mepivacaine 1 % (3-4 ml) will injected. Measurements Intensity of pain at the end of each procedure will be measured by Numerical Rating Scale (NRS) between 0 and 10 points, where Zero usually represents 'no pain at all' whereas ten represents 'the worst pain ever possible. Evaluation of patient's adherence to the treatment, will be detected as the number of patients that manage to complete the session The sensitive block duration will be evaluated by pinprik test (defined as a test for cutaneous pain receptors. A small, clean, sharp object such as a pin or needle is gently applied to the skin and the patient is asked to describe the sensation. One must be certain the patient is reporting the sensation of pain rather than that of pressure.) The efficacy of HESWT will be evaluated by American Orthopedic Foot and Ankle Society Score (AOFAS) after 1 month from the end of treatment. Each measure of AOFAS is comprised of nine questions and cover three categories: Pain (40 points), function (50 points) and alignment (10 points). These are all scored together for a total of 100 points. Inclusion criteria Patients will be enrolled if they present all of the following criteria: History of Chronic Achilles tendinopathy and/or plantar fasciitis at least 6 months long Unsatisfying subjective result (Numeric Rating Scale (NRS) score persistently ≥ 4 points for pain during the first few steps of walking in the morning) after at least 6 months after ≥ 3 of the following 5 conventional therapy programs: ≥ 4 weeks of physical therapy; ≥4 weeks course of non-steroidal anti-inflammatory medications HEWST indication Application of HESWT at 1500 shock waves with energy of 16 Ky First treatment discontinued for surge of pain (numeric rating scale \> 5) Exclusion criteria Patient \< 18 years Peripheral circulatory disorders Arthrosis of the foot or ankle, as confirmed by X-ray diagnosis Skin lesions of the foot Allergy to local anesthetic Neurologic abnormality (changes of deep tendon reflexes, motor or sensory deficit) Routinely consumption of analgesics or history of analgesic consumption within 24 hours prior to therapy. Statistical Plan Sample size determination As a pilot study, no data is available in the literature. The proposed sample size is N:21 patients. This dimension provides a power of 0.99, with confidence level = 0.05 of detecting a 40% reduction in the NSR score from T0 to T1. Statistical analysis The sample will be described in its clinical and demographic features using descriptive statistics techniques. Quantitative variables will be described using the following measures: minimum, maximum, range, mean and standard deviation. Qualitative variables will be summarized with absolute and percentage frequency tables. Normality of data will be verified using the Kolmogorov-Smirnov test. The primary objective will be achieved performing a Student's T test for paired sample. The proportion of patients that are able to complete a single session with Posterior tibial nerve block will be evaluated and compared to the same proportion in patients without Posterior tibial nerve block (40% of patients can not complete the session); The mean and median number of sessions required to complete successfully the treatment will be calculated. The evaluation of HESWT efficacy will be performed via the AOFAS score, comparing proportions using the Chi squared test. Possible comparisons will be performed with the Student T test for paired sample (if data are normally distributed) or with the Wilcoxon test (for non normal distribution). Comparison of categorical data will be performed using a Chi-square test.