Increased co-contraction of arm adductors is associated with a favorable course in subacromial pain syndrome

Celeste L Overbeek; Arjen Kolk; Jochem Nagels; Pieter Bas de Witte; Peer van der Zwaal; Cornelis P J Visser; Marta Fiocco; Rob G H H Nelissen; Jurriaan H de Groot

doi:10.1016/j.jse.2018.06.015

Increased co-contraction of arm adductors is associated with a favorable course in subacromial pain syndrome

J Shoulder Elbow Surg. 2018 Nov;27(11):1925-1931. doi: 10.1016/j.jse.2018.06.015. Epub 2018 Sep 19.

Authors

Celeste L Overbeek¹, Arjen Kolk², Jochem Nagels², Pieter Bas de Witte³, Peer van der Zwaal⁴, Cornelis P J Visser⁵, Marta Fiocco⁶, Rob G H H Nelissen², Jurriaan H de Groot⁷

Affiliations

¹ Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: c.l.overbeek@lumc.nl.
² Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands; Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands.
³ Department of Orthopaedics, Leiden University Medical Center, Leiden, The Netherlands.
⁴ Department of Orthopaedics, Haaglanden Medical Center, The Hague, The Netherlands.
⁵ Department of Orthopaedics, Alrijne Hospital, Leiderdorp, The Netherlands.
⁶ Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, Leiden, The Netherlands.
⁷ Laboratory for Kinematics and Neuromechanics, Department of Orthopaedics and Rehabilitation, Leiden University Medical Center, Leiden, The Netherlands.

PMID: 30243903
DOI: 10.1016/j.jse.2018.06.015

Abstract

Background: Enhancement of arm adductor activity during abduction (ie, adductor co-contraction), may be effective in the treatment of subacromial pain syndrome (SAPS). We assessed whether an increase of adductor co-contraction is associated with a favorable course of SAPS.

Methods: At baseline and after nearly 4 years of follow-up, electromyography of the latissimus dorsi (LD), teres major (TM), pectoralis major, and deltoid muscle was obtained during isometric abduction and adduction tasks in 26 patients with SAPS. Changes in co-contraction were assessed with change in the activation ratio (ΔAR). The AR ranges between -1 and 1, where lower values indicate more co-contraction. Clinical course was determined from an anchor question (reduced, persistent, or increased complaints), the visual analog scale for pain (VAS), and the Western Ontario Rotator Cuff score (WORC).

Results: In patients indicating persistent complaints (31%), the VAS and WORC remained stable. In patients who indicated reduced complaints (69%), the VAS reduced (z score, -3.4; P = .001) and WORC increased (z score, 3.6; P < .001). Unchanged ARs associated with complaints persistence, whereas decreased AR of the LD (ΔAR_LD, -0.21; 95% confidence interval [CI], -0.36 to -0.06) and TM (ΔAR_TM, -0.17; 95% CI, -0.34 to -0.00) coincided with reduced complaints. There was a significant between-group difference in ΔAR_LD (-0.35; 95% CI, -0.60 to 0.10) and ΔAR_TM (-0.36; 95% CI, -0.66 to -0.05).

Conclusions: Increased co-contraction of the LD and TM is associated with a favorable course of SAPS. This may be explained by widening of the subacromial space accomplished by adductor co-contraction.

Keywords: Shoulder impingement syndrome; biomechanical phenomena; co-contraction; electromyography; latissimus dorsi; teres major.

MeSH terms

Deltoid Muscle / physiopathology*
Electromyography
Female
Follow-Up Studies
Humans
Male
Middle Aged
Muscle Contraction / physiology*
Pain Measurement
Pectoralis Muscles / physiopathology*
Range of Motion, Articular / physiology
Shoulder Pain / physiopathology
Shoulder Pain / therapy*
Superficial Back Muscles / physiopathology*
Treatment Outcome