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Tennis Elbow Braces – A critical appraisal

A recent study shows that some people benefit from bracing for the treatment of lateral epicondylalgia and that the specific type of brace is not that important.

Study Appraised: Bisset LM, Collins NJ, Offord SS. Immediate Effects of 2 types of braces on pain and grip strength in people with lateral epicondylalgia: a randomized controlled trial. JOSPT 2014;44(2):120-128.

What question did the study ask?

Purpose:    To compare the immediate effectiveness of 2 types of counterforce braces in improving pain-free grip strength, pressure pain threshold, and wrist angle during gripping task in individuals with lateral epicondylalgia.

Patients – Eligibility criteria were clearly outlined: 34 patients with a clinical diagnosis of lateral epicondylalgia as defined by Haker¹: pain over the lateral elbow for a minimum 6 weeks that increased with palpation of the lateral epicondyle, gripping, or resisted extension of the wrist, or the second or third finger.

Exclusion criteria: bilateral elbow symptoms; cervical radiculopathy; other elbow joint pathology or peripheral nerve involvement’ past history of elbow surgery, dislocation, fracture or tendon rupture; shoulder, wrist, or hand pathology; systemic or neurological disorders; treatment for elbow pain by a health care practitioner within the preceding 3 months; corticosteroid injection for elbow pain within the previous 6 months.

 Intervention – A commercially available counterforce brace (Thermoskin tennis elbow strap with pad) that consisted of a strap applied circumferentially around the proximal forearm just distal to the lateral epicondyle.

Comparison – Another commercially available counterforce brace(Go-Strap) that consisted of a strap applied circumferentially around the proximal forearm just distal to the lateral epicondyle and an additional strap that passed from the lateral aspect of the brace anterior to the lateral epicondyle and around the posterior and medial aspects of the distal humerus, then attached back onto the counterforce brace laterally.

There was also a control where the outcome measures were taken but no brace was applied.

Outcomes –

1^o   Pain free grip strength (PFGS)    There were statistically significant immediate improvements using either brace, and no brace but no significant differences between the three conditions.

2^o   Pressure pain threshold (PPT)    There were statistically significant changes between the precondition and postcondition using either brace or the control. There was no significant difference between braces or the control.

2^o   The sagittal plane wrist angle during PFGS measurement was also used as a secondary outcome to determine changes in position during gripping pre and post application of the condition. Side-to-side differences in wrist extension angle during gripping within groups was also measured. No significant difference was found in wrist extension angle during gripping in all three conditions. A 5o difference was found when comparing the affected side to the unaffected side within groups.

 ARE THE RESULTS OF THE TRIAL VALID?

     1a.   R- Was the assignment of patients to treatments randomized?

 Yes. The author reports using a computer generated randomization sequence, created by an investigator who was not involved with either treatment or outcome assessment, that was delivered via sealed, opaque envelopes and opened in consecutive order by the treating therapist. Conditions were applied in a random order: forearm brace, forearm-elbow brace, and no brace.

      1b.  R- Were the groups similar at the start of the trial?

All 34 participants received all three interventions. This was a diverse group of individuals between the age of 28 and 67 (mean=47.8) with unilateral lateral elbow pain of duration 6 to 570 weeks (mean=64.6). Function prior to testing was quite variable on a functional scale (Patient-Rated Tennis Elbow Evaluation)5 to 100, with a mean of 76.0 (where 100 is the worst imaginable disability)²

     2a.  A- Aside from the allocated treatment, were groups treated equally?

Yes. All patients had therapist interaction for the same period of time whether a brace was applied or not prior to measurement. Braces were applied according to manufacturer’s recommendations with sufficient tension to feel supportive when gripping. This level of tension was not quantified so tension may have been variable between applications. Tension of brace application has been found to be correlated to pain threshold and functional outcomes.3 There was at least a 48 hour washout period between interventions.

      2b.  A- Were all patients who entered the trial accounted for? – and were they analysed in the groups to which they were randomized?

Yes, all patients were accounted for. After screening 149 patients, 34 met the exclusion criteria and baseline measures were recorded. No patients were lost to follow-up and all participants crossed over to receive all interventions. This 100% follow-up exceeds the 80% threshold.

3. M – Were measures objective or were the patients and clinicians kept “blind” to which treatment was being received?

 

• The therapist that applied the condition was blinded to treatment allocation. The therapist was not aware of treatment allocation until they opened the opaque envelope.
• Outcome measures were taken by a blinded assessor skilled in their application pre-intervention and post-intervention bilaterally. This physical therapist remained blinded to treatment allocation throughout the study period. Participant and assessor blinding was facilitated by visually obstructing the participants view while each brace was applied using an opaque fabric that was draped over the arm and forearm covering brace strap and leaving only the lateral epicondyle visible for measurement of PPT. Assessor blinding was examined via a questionnaire and revealed that the assessor was able to guess the intervention correctly 38% of the time. This is greater than would be expected by chance.
• Participant blinding could not be complete as they would feel which brace was placed on their arm. 60% of subjects indicated a preference for the forearm-elbow brace possibly biasing results.

WHAT WERE THE RESULTS?

1. How large was the treatment effect?

• A small treatment effect occurred in all three groups indicating that all conditions improved PFGS and PPT.
• Using baseline data they calculated a standard error of measurement (standard deviation x √1-ICC) from the 3 trials to determine magnitude of measurement error for each dependent variable (PFG, PPT, and wrist angle) and an MDC (minimal detectable change) to ensure 95% CI that the true value of measure was within this range. (1.96 x √2 x standard error of measurement) MDC for PFGS was 40.1 N. MDC for PPT was 134.3 kPa. MDC for wrist angle was 6.3o
• The improvements reported in PFGS and PPT were smaller than this MDC and may therefore be due to measurement error rather than a true clinical change.
• There was no change seen in grip angle in any of the conditions, but it consistently showed that patients with lateral epicondylalgia gripped with 5^o less wrist extension on the affected side compared to the unaffected side.

2. How precise was the estimate of the treatment effect?

PFGS: The affected side demonstrated a small improvement with use of the forearm brace of 21.9N in (95% CI:9.1,34.6) This confidence interval falls within the confidence interval of the control group 7.3N (95% CI:-1.5,16.0)

The affected side demonstrated a small improvement with the use of the forearm-elbow brace of 22.2N (95% CI:8.4, 36.0). This confidence interval falls within the confidence interval of the control group 7.3N (95% CI:-1.5,16.0).

PPT: The PPT of the affected side improved with use of the forearm brace by a mean of 67.2kPa (95% CI:26.7,107.8) This value falls with the confidence interval of the control group 14.5kPa (95% CI:-37.0,66.0)

The PPT of the affected side improved with use of the forearm-elbow brace by a mean of 40.2N (95% CI:4.4,84.7) This value falls with the confidence interval of the control group 14.5kPa (95% CI:-37.0,66.0)

Wrist Angle: Wrist angle did not change between pretreatment and post treatment interventions. The within-group difference of 5o between affected and unaffected sides falls below the 6.3o MDC.

Will the results help me in caring for my patient? (External Validity/Applicability)

Results of this study are applicable to patients presenting with lateral elbow pain that meet the diagnostic criteria for lateral epicondylalgia:  pain over the lateral elbow for a minimum 6 weeks that increased with palpation of the lateral epicondyle, gripping, or resisted extension of the wrist, or the second or third finger. Patient baseline condition is similar to that of a subgroup of patients that present to an outpatient physical therapy setting.

The addition of elbow bracing to a treatment plan is easily implemented and inexpensive, and preferable to patients over corticosteroids or other medications that may have undesirable side effects.

Pain free grip strength is a clinically relevant outcome because by reducing pain severity we can introduce pain-free exercises into the plan of care. It seems intuitive that improvements in pain-free grip strength would be correlated to changes in function.

Patients excluded from this trial included those with bilateral lateral elbow pain, cervical radiculopathy, other elbow or peripheral nerve pathology, past history of elbow surgery, dislocation, fracture, tendon rupture, shoulder, wrist, or hand pathology, systemic or neurological disorders, or prior cortisone injection within the last 6 months. One cannot necessarily apply the results of this study to those with the above listed exclusion criteria.

Results showed that there was no difference in outcomes between the braces used, allowing us to recommend the brace that offered the patient the most comfort. Because the results of this study may be due to measurement error rather than true clinical change the authors caution us that further investigation is required.

Suggested improvements to the study:

1. Larger sample size to reduce the relative size of the CI.
2. Standardize and quantify brace tension. The author states that “brace tension does not appear to influence wrist extension strength”, thereby justifying their not quantifying brace tension. The study they refer to measured isokinetic extensor peak torque, not painfree isometric strength in as the author stated a “spontaneous posture”.³ I don’t think we can correlate the two.
3. Provide patients with a training period to eliminate training effects which may account for the improvement in the control group.
4. Determine if there are other exclusion criteria that might improve outcomes and narrow the CI.
5. Effectiveness of bracing may improve over time so the author suggested a long term followup and addition of a functional outcome measure.

 References

1.Haker E. Lateral epicondylalgia: diagnosis, treatment and evaluation. Crit Rev Phys Rehabil Med. 1993;5:129-154.

2.Rompe JD, Overend TJ, MacDermid JC. Validation of the Patient-rated Tennis Elbow Evaluation Questionnaire. J Hand Ther. 2007;20:3-10.

3.Ng GYE, Chan HL. The immediate effects of tension of counterforce forearm brace on neuromuscular performance of wrist extensor muscles in subjects with lateral humeral epicondylosis” JOSPT. 2004;34(2):72-78