Study design
This was a case - control study. All the adult subjects with chronic lateral epicondylitis referred to Physiotherapy department in a multispecialty teaching hospital of a University were included in the study.
Ethical clearance
The study was approved by the Institutional Scientific Ethics Committee of Manipal University, Manipal and was registered in Clinical Trials Registry-India: UTRN 060144369-190420102025203.
Participant requirement
Inclusion criteria were pain and tenderness over the lateral epicondyle, at least 2 out of 3 tests for lateral epicondylitis including Cozen's test, Mill's maneuver, or resisted middle finger extension was positive, minimum duration of three months, willing to participate in the study, and ability to comprehend the instructions given by the tester. Exclusion criteria included all the subjects with history of trauma, fracture, surgery, or other medical and non-medical interventions to elbow, bilateral symptoms, polyarthritis, upper quadrant neuromusculoskeletal disorders that might affect grip strength.
Participant selection
Athlete subjects were those engaged in recreational sports involving tennis or badminton which requires repetitive use of wrist extension position. Non athletes were subjects who were not engaged in any kind of sports activity involving the use of upper extremity. The athletes were recruited from students and staff of the institution while non-athletes involved patients referred for physiotherapy treatment by a medical practitioner. After giving them a detailed explanation about the purpose of the study and its clinical significance a written informed consent was obtained from all the subjects.
Testing procedure
The test was conducted during a single session. After a verbal description of the test procedure, the method of testing was demonstrated to the subject. For each of the tests of grip strength, the standard position recommended by the American Society of Hand Therapists (ASHT) was administered. For performing the test, subjects were seated on a high plinth without supporting the forearms. The shoulder was kept in adduction and neutral rotation; elbow flexed at 90° forearm in neutral position; The wrist positions were kept static by the use of an external support .15° of wrist position was first tested with the splint, followed by 35° (Figures 1, 2). For standardization, the handle of the Jamar® dynamometer was kept at the second handle position.
Structure of the wrist splint(s)
The experimental splint used for this study was a fabricated dorsal forearm support-wrist extension splint, with dorsal metacarpal bar and ventral Velcro straps to fasten it to the forearm. Two splints were used- one of 15 degrees wrist extension and other of 35 degrees wrist extension (refer figure-1 and figure-2).
Selection of side for grip strength testing
The first side (involved or uninvolved) to be tested was chosen randomly by a -toss of a coin- method. To ensure that equal number of subjects was tested first on either of their tested side, block randomization was used for further sub-grouping under athlete or non-athlete group. The allocation method was concealed from the primary investigator (tester-1) by the use of sequentially-numbered sealed opaque envelopes.
Outcome measures
Specific instructions were given to each subject before the test. They were asked to "squeeze" the dynamometer as hard as possible, and to hold the position for 5 seconds (Figure-3). No verbal encouragements were given during the test. None of the subjects complained of any discomfort with splint during testing. Grip strength readings were recorded in kilograms. Three trials were performed at each of the15° and 35° of test positions for the uninvolved and involved extremity and the three values were recorded. Each measurement was repeated 3 times. A minimum of 1 minute rest period was allowed between efforts on the same side to minimize the effects of fatigue. To ensure minimized effects of repeated testing on fatigue in performance, random order of testing each of the two positions was done and this was selected by block randomization. The dynamometer was reset to zero prior to each reading. The grip strength was recorded in kilograms-force (kgf).
Data collection
The readings were taken by another blinded observer and the primary investigator was not aware of the subject's grip strength during the testing.
Data analysis
Sample size estimation was done using a minimum clinically important difference of 2.0 ± 1.2 kgm (mean ± SD) in grip strength measurements at 80% power and alpha (type-1 error) at 5% level, to be 24. We had an estimated prevalence of athletes (elite and recreational combined) to be one-third of total population. Hence we need to take the study population in 1:3 ratio for athletes: non-athletes. Eight athletes and 16 non-athletes would be statistically sufficient thereby requiring a sample size of 24. There was no anticipated loss to follow-up since the design was a cross-sectional one.
The within-group analysis (comparison between involved and uninvolved sides at both 15 and 35 degrees) was done using Wilcoxon signed-rank test and between-group comparison (comparison between athletes and non-athletes) for grip strength was analyzed using Mann Whitney U-test using the SPSS 11.5 for windows software. The statistical significance was set at p ≤ 0.05.