Altered activity of the serratus anterior during unilateral arm elevation in patients with cervical disorders
Introduction
Normal stability of the scapula includes the ability to maintain normal orientation of the scapula with the arms by the side and during all activities of the upper limb. The muscular system is primarily responsible for scapular orientation because the sternoclavicular joint is the only bony-ligament attachment of the shoulder girdle to the trunk. All muscles that are attached to the shoulder girdle contribute to its stability, but in different degrees (Comerford and Mottram, 2010). Altered scapular orientation most frequently occurs because of altered activity or poor neuromuscular patterns in the serratus anterior and trapezius (scapular stability muscles) as well as altered activity and extensibility of the pectoralis minor, levator scapulae and rhomboids that may compromise the muscle balance (scapular mobility muscles) (Mottram, 1997, Sahrmann, 2002, Kibler and McMullen, 2003, Mottram et al., 2009, Comerford and Mottram, 2010).
The activity of the main stabilisers of the scapula, the serratus anterior and trapezius, depends not only on force production but also on neuromuscular control and recruitment that requires a precise co-ordinated activity occurring at the right moment, creating the right amount of force, maintained for the right length of time. This proper firing pattern and recruitment requires coupling of the serratus anterior muscle with the upper, middle and lower trapezius that results in “force couples” which are considered necessary for normal scapular orientation (Inman et al., 1996, Mottram, 1997, Kibler and McMullen, 2003). Appropriate activity of these muscles depends on proprioception which is linked to the sensation of position and movement of the joints, the sensation of force, effort and heaviness associated with the muscular activity; and the perceived timing of muscle contraction (Gandeviaa et al., 1992, Comerford and Mottram, 2010). Muscle recruitment deficits are manifested by an altered pattern of recruitment or an altered timing (early/delayed muscle onset) (Comerford and Mottram, 2010).
The presence of neck pain is known to alter the activity of the upper and lower trapezius during upper limb tasks (Szeto et al., 2005a, Falla et al., 2007, Wegner et al., 2010) and alter scapular orientation (Szeto et al., 2002, Szeto et al., 2005b, Yip et al., 2008, Helgadottir et al., 2010, Helgadottir et al., 2011). Biomechanical reasoning indicates that altered activity in the axioscapular muscles associated with altered scapular orientation may induce detrimental load on the cervical spine (Behrsin and Maguire, 1986, Janda, 1994, Jull et al., 2004). Studies have shown that increased tension in muscle such as the levator scapulae through its attachment to the upper four cervical segments may directly induce compressive, rotational and shear forces on cervical motion segments (Behrsin and Maguire, 1986). Altered stability of the scapula may therefore create or sustain symptomatic mechanical dysfunction in the cervical spine, and influence the recurrence of neck pain (Janda, 1994, Jull et al., 2004, Jull et al., 2008, Sahrmann, 2011).
Current therapeutic guidelines for patients with neck pain and related disorders include analyzes and correction of the function of the scapular muscles and scapular orientation (Jull, 1997, Mottram, 1997, Jull et al., 2004, Jull et al., 2008, Wegner et al., 2010, Andersen et al., 2011). These guidelines are primarily based on the results of studies on shoulder patients as investigations of the scapular stability system in patients with neck pain are sparse. The activity and recruitment properties of the serratus anterior and trapezius during arm elevation have not been investigated in patients with neck pain before. Since a difference may exist in the impairment between patients with insidious onset neck pain (IONP) and whiplash associated disorders (WAD) (Nederhand et al., 2002, Falla et al., 2004, Elliott et al., 2008, Kristjansson and Oddsdottir, 2010) this study included both groups of patients. The aim of the study was to investigate whether there is a pattern of altered activity of the serratus anterior and trapezius during arm elevation in patients with IONP and WAD compared to asymptomatic subjects. The hypothesis was that patients with neck pain will demonstrate altered activity in these muscles.
Section snippets
Participants
Twenty-two patients with IONP (20 women and 2 men) and twenty-seven patients with WAD grade II, (24 women and 3 men) following a motor vehicle accident were recruited on a voluntary basis. WAD grade II, is described as neck complaint of pain, stiffness, or tenderness and musculoskeletal signs which include decreased range of motion and point tenderness (Spitzer et al., 1995). A sample of convenience consisting of twenty-three asymptomatic people (18 women and 5 men) served as controls (Table 1
Experimental procedure
The overall flow of the experiment procedure was as follows. The subject was instructed to sit in a comfortable upright position such that the sacrum was in contact with the back of the chair with feet placed parallel on the floor. The global transmitter was attached to the back of the chair and the Fastrak sensor was placed on the posterior aspect of humerus in vertical line with olecranon. The area of EMG electrode placement was cleaned with alcohol swabs to lower the electrical impedance.
Results
There was no significant difference in age, weight and height between the three groups but a significant difference was found in the level of disability and pain between the symptomatic groups, where the WAD group had a significantly higher disability (NDI) (P = .04) and pain level (VAS) (P = .03) compared to the IONP group (Table 1).
Fig. 2 and Table 2 demonstrate the mean (SEM) of the onset of muscle activation and Fig. 3 and Table 3 the mean (SEM) for duration of muscle activity in the three
Discussion
The results of the study partially support our hypothesis that patients with neck pain may demonstrate a pattern of altered activity of the scapular stabilizers as a significantly delayed onset of muscle activation and less duration of muscle activity was found in the serratus anterior in these patients compared to asymptomatic people (Fig. 2, Fig. 3 and Table 2, Table 3). This finding may have implications for scapular stability because it may reduce the quality of neuromuscular performance
Conclusions
Patients with IONP and WAD demonstrated a significantly delayed onset of muscle activation and less duration of muscle activity of the serratus anterior on both sides during arm elevation. This finding may have implications for scapular stability in these patients. No difference was revealed between the two symptomatic groups suggesting that the disturbance in the onset of muscle activation of the serratus anterior muscle may occur as a general response to chronic neck pain. However, the
Ethical approval
This study was approved by the Bioethics Committee of Landspitali University Hospital and all participants signed a consent form.
Funding
The study received a funding from the Icelandic Centre for Research www.rannis.is and from the Landspitali University Hospital Research fund. Those foundations were not in any way involved in this work.
Conflict of interest statement
The authors have no financial or personal relationship with other people or organizations that could inappropriately influence their work.
Acknowledgements
The authors wish to thank fellow colleagues that assisted in the recruitment of participants, to the Faculty of the Department of Physiotherapy and Research Centre of Movement Science, and to Asmundur Eiriksson (KINE, Hafnarfjordur, Iceland) for his contribution concerning the technical part of the study.
Harpa Helgadottir received a BS degree in Physical Therapy from the University of Iceland 1991, the Manual Therapy and the MHSc degree from the University of St. Augustine USA 2000 and 2005, and the Ph.D. degree in BioMedical Science at the University of Iceland 2010. Harpa is an adjunkt at the University of Iceland and teacher at International seminars in Movement analysis and Neuromuscular Re-education of the Neck & Shoulder Girdle.
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Cited by (0)
Harpa Helgadottir received a BS degree in Physical Therapy from the University of Iceland 1991, the Manual Therapy and the MHSc degree from the University of St. Augustine USA 2000 and 2005, and the Ph.D. degree in BioMedical Science at the University of Iceland 2010. Harpa is an adjunkt at the University of Iceland and teacher at International seminars in Movement analysis and Neuromuscular Re-education of the Neck & Shoulder Girdle.
Eythor Kristjansson, graduated in Physical Therapy in 1981(B.Sc) and specialized in Manual Therapy in Oslo, Norway 1983–1987. He was acknowledged as specialist in Manual Therapy in 1993. He received the PhD in Health Science from University of Iceland in cooperation with University of Queensland, Brisbane, Australia in 2004. He his former assistant professor in physical therapy and has been a supervisor for B.Sc, M.Sc and Ph.D. students the last 10 years. He is currently researchers at FORMI, Ullevål University Hospital in Oslo, Norway. While simultaneously working in private practice for 30 years his main interest is facilitating utilization of research results in clinical practice for patients with neck pain and its associated disorders. He is the inventor of NeckCare AS, established in 2007, delivering online musculoskeletal therapy, www.neckcare.com.
Einar Einarsson received a BS degree in Physical Therapy from the University of Iceland 1991, a Manual Therapy certification from the University of St. Augustine USA 2000 and in 2006 the M.Sc degree in BioMedical Science at the University of Aarhus Denmark. Einar is an adjunkt at the University of Reykjavik Iceland and a teacher at International seminars in movement analysis and neuormuscular re-education of the low back & pelvic and lower extremities.
Karduna Andrew, after having spent his entire life on the east coast of the United States, Dr. Karduna accepted a faculty position in the department of Human Physiology at the University of Oregon in 2002. Originally from New York, he did his undergraduate work at MIT receiving a BS in mechanical engineering. For graduate studies, he earned his MS from Johns Hopkins and his Ph.D. from the University of Pennsylvania, both in biomedical engineering. From 1996 to 2002, Dr. Karduna served as a faculty member in the department of rehabilitation sciences at MCP Hahnemann University (now Drexel University) in Philadelphia. His main research interest is in the area of upper extremity biomechanics, with an emphasis on kinematics, EMG analysis, proprioception and occupational disorders.
Halldór Jonsson Jr., became specialist in Orthopaedic Surgery in Sweden 1986 and in Iceland 1987 and received a PhD degree from the University of Uppsala in Sweden in 1992. He is to-day Chief Surgeon at the Landspitali Hospital in Reykjavík, Professor at the Medical Faculty and Chairman for the Institution of Orthopaedic Surgical Sciences at the University of Iceland.