Conditions: Achilles Tendon Pain
Keywords: Human Pain Biomechanics Anesthetics
Allocation: NON_RANDOMIZED | Intervention model: SINGLE_GROUP
Enrollment: 46
Healthy volunteers: yes

Brief summary:
The purpose of this study is to better understand how the peripheral and central nervous system interact to produce the sensation of pain and motor patterns in patients with achilles tendinopathy (AT). These findings will motivate the development of future clinical studies that incorporate knowledge about pain processing and movement strategies in patients with tendinopathy. Participants with achilles tendinopathy will receive an anesthetic injection to the achilles tendon in order to examine how reduced pain, detected by the peripheral nervous system, alters task performance and perception of pain. We hypothesize that there are factors within the central nervous system that contribute to continued pain and disability in patients with chronic AT.

Detailed description:
Twenty three people with Achilles tendinopathy (AT) and 23 people without AT will participate in this single visit clinical study. Participants will rate their pain with pressure to the heel, leg and elbow, climb stairs and perform a novel task in a motion capture system, and complete questionnaires on how pain affects their daily life. All subjects will complete these measures twice, and for participants with AT they will complete this battery of tests before and after an anesthetic injection to the area of pain. This study has 2 aims:

Specific Aim 1 compares measures of altered central processing in patients with chronic AT to adults without chronic pain; we hypothesize that patients with chronic AT will demonstrate signs of altered central processing, including central sensitization (lower pressure pain threshold), psychosocial factors (higher kinesiophobia), and/or altered motor control (lower ankle power during stair ascent).

Specific Aim 2 determines which indicators of altered central processing persist after a local anesthetic injection to the Achilles tendon in patients with chronic AT; we hypothesize chronic AT pain is perpetuated by altered central processing that persists in the absence of continued peripheral nociception.

Arms:
arm 1: Ropivacaine injection. While looking at the Achilles tendon with ultrasound, the orthopaedic physician will inject 4 mL of 0.5% ropivacaine (numbing medicine) around the area of pain. The needle may be directed just under the skin (and above the tendon) and/or deep to the tendon. arm 2: The control group did not receive an injection between test repetitions

Interventions: intervention 1: Ropivacaine injection
Intervention descriptions: intervention 1: single dose, subcutaneous injection

Protocol document:
Prot_SAP_000.pdf: 
Achilles Pain Block 
 
NCT 03316378 
 
Date of Document: 4/29/19 
 
Date study protocol initially approved by the IRB: 1/27/2016 
 
Date study was most recently approved by the IRB: 8/13/2018 
 
 


Study design 
In this mechanistic, non-randomized controlled trial, all participants repeated testing twice in the 
following order within a single laboratory-based testing session: 1) pain-rating with activity, 2) movement 
analysis during high- and low-level tasks, 3) pain psychology questionnaires; 4) quantitative sensory testing 
(See figure below). The only difference in procedure between groups was that the AT group received an 
anesthetic injection after the first set of tests. For participants with bilateral AT the more painful side was 
designated the involved side for testing and injection. A sports medicine physician used sonographic guidance 
to inject 4 mL of 0.5% ropivacaine superficial and deep to the tendon to ensure coverage of the painful region. 
This dose was chosen based on clinical experience of the amount of ropivacaine needed to numb the area for 
minimally-invasive outpatient procedures. To minimize the risk of infection sterile technique was used, 
including sterile gloves, area of injection scrubbed, sterile gel, and a sterile transducer cover. The onset for 
ropivacaine was 10-20 minutes and pain relief lasted for 6-8 hours. Repeat testing began 30 minutes after the 
injection. Participants with AT were contacted 1-day and 1-week following testing to ask about any injection-
related adverse events (e.g. increased pain, infection). All participants were contacted 1-week after testing to 
complete the pain catastrophizing scale (PCS). 
Figure 1. All participants completed two sets of testing. The group with Achilles tendinopathy pain received a 
local anesthetic injection prior to repeat testing. The control group without Achilles tendinopathy pain did not 
receive an injection prior to the second set of testing.  
 
 
 
 
 
 
 
 
Statistical Analysis 
A priori power analysis determined that a sample size of 20 per group was needed to detect effect sizes 
(between groups>0.91, between repeat tests>0.68) less than or equal to published results for ankle power 
(mean difference= 0.9 W/kg, SD=0.9 W/kg)1, kinesiophobia (minimal detectable change=5.6, SD=5.7)2, and 
pressure pain threshold (group difference=171.8 kPA, SD=174.8 kPA) 3 with a power ≥80% and statistical 
significance defined as P≤ 0.05 (Table 1). Because 3 participants with AT had insufficient pain relief from the 


anesthetic injection, an additional 3 participants were recruited per group to ensure adequate power, resulting 
in a final sample size of 46. Sample characteristics were compared between groups using independent 
samples t-test for parametric data, Mann-Whitney U test for non-parametric data, or Chi-square test for 
categorical data. Changes in Achilles tendon pain from pre-injection to post-injection were compared with 
Wilcoxon Signed Ranks tests. Mixed effects ANOVAs were used the examine the effects of group, time, and a 
group*time interaction for motor performance, pain psychology, and quantitative sensory testing. The type I 
error rate for the ANOVAs was maintained at 0.05 by using Bonferroni adjustment for multiple comparisons (3 
tests for motor performance, 2 tests for pain psychology, 3 tests for quantitative sensory testing). Post-hoc 
comparisons were performed to examine significant interaction effects and p-values were adjusted using a 
Bonferroni adjustment for the number of time points compared (2 for TSK, 3 for PCS, 4 for quantitative sensory 
test). Pearson correlations examined relationships between the magnitude of change with an anesthetic 
injection of identified indicators of altered central processing in the AT group.  
 
 
 
 
 
 
 
 
 
 
 
 
 
Table 1. Detectable effect sizes and published differences using proposed sample size and assumed SD 
Primary outcome / 
dependent variable 
Assumed 
SD 
Detectable  
difference 
Published 
difference 
Specific Aim 1.1, n=40, between groups, detectable effect size ≥0.91 
PPT (Central sensitization) 
174.8 kPa3 
158.9 kPa 
171.8 kPa3 
TSK (Psychological factor) 
5.72 
5.2 
MDC= 5.62 
Ankle power (Motor control) 
0.9 W/kg1 
0.8 W/kg 
0.9 W/kg1 
Specific Aim 1.2, n=20, repeated measures, detectable effect size ≥0.68 
PPT (Central sensitization) 
28% 
19% 
25.8%4 
TSK (Psychological factor) 
5.72 
3.8 
MDC= 5.62 
Ankle power (Motor control) 
0.9 W/kg1 
0.6 W/kg 
0.9 W/kg1 


References 
1. 
Chimenti RL, Flemister AS, Tome J, McMahon JM, Houck JR. Patients With Insertional Achilles 
Tendinopathy Exhibit Differences in Ankle Biomechanics as Opposed to Strength and Range of Motion. 
J. Orthop. Sports Phys. Ther. Dec 2016;46(12):1051-1060. 
2. 
Hapidou EG, O'Brien MA, Pierrynowski MR, de Las Heras E, Patel M, Patla T. Fear and Avoidance of 
Movement in People with Chronic Pain: Psychometric Properties of the 11-Item Tampa Scale for 
Kinesiophobia (TSK-11). Physiother. Can. Summer 2012;64(3):235-241. 
3. 
Noehren B, Shuping L, Jones A, Akers DA, Bush HM, Sluka KA. Somatosensory and Biomechanical 
Abnormalities in Females with Patellofemoral Pain. Clin. J. Pain. Nov 26 2015. 
4. 
Frey Law LA, Evans S, Knudtson J, Nus S, Scholl K, Sluka KA. Massage reduces pain perception and 
hyperalgesia in experimental muscle pain: a randomized, controlled trial. J. Pain. Aug 2008;9(8):714-
721.