Elbow flexor and extensor muscle weakness in lateral epicondylalgia. Clinical commentary

Elbow flexor and extensor muscle weakness in lateral epicondylalgia.

Coombes BK, Bisset L, Vicenzino B. Elbow flexor and extensor muscle weakness in lateral epicondylalgia. Br J Sports Med. 2012;46:449-453.

Abstract

Background

Lateral epicondylalgia (LE) is one of the common and complex elbow problems in athletes as well as in general population.1 Pain with reduced grip strength and weakness of muscles mainly wrist extensors are the cardinal signs of LE.2 Many studies have focused on the strength of upper limb (UL) kinetic chain segments such as MCP, wrist, and shoulder associated with LE.3-6 But surprisingly, elbow flexors and extensors are not evaluated by any studies yet, despite its biomechanical importance in UL kinetic chain, functional movements, and sporting activities.

Objective

To identify and evaluate the possible elbow flexor and extensor muscles weakness associated with LE compared to the healthy population.

Methods:

One hundred and fifty participants were recruited for a cross-sectional study. Inclusion criteria were: unilateral elbow pain over lateral epicondyle for longer than six weeks, pain aggravated with palpation, gripping and resisted wrist and/or finger extension. Exclusion criteria were: elbow pain due to other conditions such as carcinogenic, radiohumeral or neurological, recent fractures, corticosteroid injections or physiotherapy treatment. Fifty-four healthy participants were recruited as age and gender-matched controls.

All the participants were tested for the isometric elbow extension and flexion strength on both affected and unaffected sides with 30 seconds intervals alternatively. Controls were also tested on both sides. Strength was measured at the level of ulna styloid process in Newton(N) by using a digital dynamometer attached to a purpose-built apparatus, in a standing position with elbow flexed at 900 and forearm in neutral rotation. Participants were not allowed to do any extraneous movements like trunk or scapular movemen. They were instructed to keep their wrist and fingers relaxed during the test. Data were analyzed by performing analysis of covariance (ANCOVA) by using SPSS 19. The covariates were; age, gender, and BMI of the participants.

Results:

Strength differences (affected–unaffected) greater than 2.09 and 3.14 N for extensor and flexor respectively were considered significant with 95% confident and represent true change.

Results revealed significant side difference between LE and control groups. Elbow extensor strength (-6.54N, 95% CI, -11.43 to -1.65, p = 0.008, SMD -0.45) and flexor strength (-11.26 N, 95% CI, -11.59 to -2.94, p = -0.009, SMD -0.46). However, within LE group, only extensor strength deficit between sides was significant with -2.94 N difference results.

Conclusion

Patients with unilateral LE have weaker elbow flexor and extensor muscles strength in comparison to healthy population. This deficit should be considered for the evaluation, performance enhancement, injury prevention and better therapeutic prognosis of LE.

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