• Abstract and Figures
• Public Full-text

Levator Scapulae Action during Shoulder Movement: A Possible Mechanism for Shoulder Pain of Cervical Origin The phenomenon of shoulder pain of cervical JOHN FREDDY BEHRSIN origin being reproduced on shoulder movement is clinically recognized. The action of the shoul­ John Behrsin, B.App. Sc., Post Grad. Dip. Manip. (WAin, is currently working in private practice and der girdle muscles is a hypothetical cause of undertaking M.Sc. studies (part-time) at the University the cervical stress. of Melbourne. This study examined the mode and degree of Levator Scapulae activity during shoulder activ­ KEN MAGUIRE ity. Electromyography and x-rays were used to Ken Maguire, M.B.B.S., B. Med. Sc. (Hons), F.R.A.C.P., measure levator scapulae activity and length. is Consultant Physician at the Royal Perth (Reha­ The results of the study show that levator sca­ bilitation) Hospital, Western Australia. pulae contracts concentrically during the first 90 degrees of shoulder abduction and eccent­ rically during the second 90 degrees. The action of levator scapulae may be re­ sponsible for the application of force on the cervical spine during shoulder abduction. This force might cause cervical joi11t tissue distor­ tion and pain ifa pathological State was present. The incidence of distally referred mechanism of cervical nerve root ten­ to assess whether a possible mechanism pain arising from irritation of vertebral sion resulting from shoulder move­ for the production of stress and pain structures is a well documented phe­ ment. This mechanism does not ac­ lay in their action. nomenon (Kellgren 1939, Cloward count for those patients who have A number of studies have examined 1959, Hockaday and Whitty 1967, negative nerve root signs and symp­ shoulder girdle muscle activity electro­ Mooney and Robertson 1977, McCall toms of purely cervical joint origin. myographically (Inman et af 1944, et af 1979). The clinical picture of a Muscle actions over a joint produce Yamshon and Bierman 1948, DeFreitas patient presenting with shoulder pain forces which may result in movement et af 1979, 1980, Hagberg 1981) but which is reproduced on certain activi­ but also create compressive forces be­ none are definitive due to methodo­ ties of the shoulder, but which, on a tween the joint surfaces (White and logical flaws. No studies were found more thorough examination, is re­ Panjabi 1978). During active shoulder which examined the mode of contrac­ vealed to have a cervical origin is com­ function, cervical movement may be tion (ie concentric, eccentric or iso­ mon (Cinquegrana 1968, Maigne 1975, prevented by synergistic muscle actions metric) of the shoulder girdle muscles. Maitland 1975, Cyriax 1978, Wells over that area, but unobservable It was felt that further study of the 1982). compression forces may still be pro­ behaviour of the shoulder girdle mus­ Cyriax (1978 p226) and Bogduk duced. Scientific studies (Howe et af cles was required to assess their pos­ (1983) have hypothesized that the ac­ 1977, Shah et af 1978, Rydevik et af sible role in relation to shoulder pain tion of the shoulder girdle muscles on 1984) and clinical observations (White of cervical origin. Levator scapulae was the cervical spine has a role in pro­ and Panjabi 1978, Maitland 1980) in­ selected for this study because it di­ ducing the referred shoulder pain of dicate that compression, especially rectly connects the cervical spine to the cervical origin on shoulder movement. when asymmetrically applied, can pro­ shoulder girdle and because its fibres These hypotheses were made without duce joint tissue or radicular distortion have a discrete pattern of alignment, reference to data. A review of the lit­ and thereby stress and pain. It was allowing for tidy biomechanical as­ erature has not revealed studies which found that there was an apparent lack sessment. have established the mechanics wherein of reliable data on the possible me­ It is generally believed that with the shoulder movement could produce chanical cause ofshoulder pain ofcerv­ cervical spine fixed, levator scapulae stress on the cervical joints and thereby ical orgin produced by shoulder move­ acts to elevate the scapula and down­ cause the referred symptoms in the ment. This led to a decision to examine ward rotate it, ie the glenoid cavity shoulder. Elvey (1980) has described a studies on the shoulder girdle muscles being turned caudally. With the sca- The Australian Journal of Physiotherapy. Vol. 32, No.2, 1986 101 Levator Scapulae and Shoulder Pain of Cervical Origin pula fixed, acting unilaterally, levator A Medelec MS6 MkIlI system was and of skinlfat thickness in the EMG scapulae is believed to laterally flex and used to record the EMG activity. The volunteer subjects. These measure­ rotate the vertebrae ipsilaterally: acting apparatus was set at a gain of 500pV/ ments indicated that this site and depth bilaterally, it is believed to assist in division, a sweep speed of 10 millisec/ was the most reliable to ensure elec­ cervical extension (Kendall and Mc­ division and for a frequency range of trode placement into the belly of lev­ Creary 1983). 16-16,000 Hz. The paper recorder was ator scapulae (Behrsin 1984). DeFreitas et at (1979, 1980) studied set at 2 cm/sec. The testing was carried out in an levator scapulae using needle electro­ A single coaxial needle electrode electrically screened room to minimize myography (EMG) during shoulder (2.5cm long in five subjects and 5.0cm extraneous electrical noise. movement but lack of methodological long in the other two) was used to pick In an endeavour to replicate the data, including the exact location of up the muscle activity. The subject was common clinical test procedures, the the EMG electrode, made their results earthed by a reusable rubber surface subjects were examined in standing. questionable. electrode placed over the scapula on Before each recording the subjects were Inman et at (1944) are often cited the test side. requested to relax their arms to obtain for their description of shoulder girdle The needle electrode was inserted in electical silence. muscle function including that of lev­ the right side at a point formed by the The movements of resisted right ator scapulae (ie by Basmajian 1978 insertion of a horizontal line passing shoulder girdle elevation and resisted and Norkin and Levange 1983), but through the Tl spinous process with a shoulder extension/adduction were examination of the original paper re­ vertical line passing one centimetre me­ performed to establish needle location vealed a lack of any data concerning dial to the superior angle of the scapula and function. These responses were levator scapulae activity. (Figure 1). The electrode was inserted noted but not recorded. Inman et al (1944) and Dvir and at a depth between 2.0 and 2.5 cm. The following movements were then Berme (1978) have described scapulo­ This site was based on the results of performed and recorded: thoracic movement during shoulder ac-. cadaveric measurements of trapezius 1. Free right shoulder abduction tivity but a lack of methodology and thickness and levator scapulae position through full range with the arm in neu­ data in the former paper and the small tral rotation. amount of data presented in the latter (ie the results from one subject) make 2. Free right shoulder flexion through these descriptions unreliable. full range with the arm in neutral ro­ This study was undertaken to assess tation. the EMG activity of levator scapulae 3. Maximal resisted right shoulder during shoulder movement and to de­ isometric abduction in five degrees ab­ termine the mode of contraction and duction starting position. length of the muscle during these 4. Free left shoulder abduction movements by way of measurement through full range with the arm in neu­ from x-rays. tral rotation. This data was combined to assess B how levator scapulae behaves during 5. Free right shoulder external ro­ tation in neutral flexion/extension with shoulder movements and whether its action could be responsible for the pro­ the elbow flexed 90 degrees. duction of stress on the cervical spine. The full range movements were per­ formed at a prerehearsed rate of ap­ Method proximately 60 degrees per second. EMG Examination of Levator Scapu­ The resultant EMG recordings were lae during Shoulder Movement then graded using the system described (Method A) Figure 1: Determination of the elec­ by Basmajian (1978). In this system the trode site. Seven volunteers, four male and degree of EMG activity is visually three female, with an average age of A First Thoracic vertebrae graded. The gradings are: 0, where 27 years (range 24-29 years) were stud­ B Scapula there is no activity; 1+ where there is ied electromyographically to observe C Levator Scapulae minimal activity (1-25010 of maximal the pattern of levator scapulae firing D Vertical line one centimetre medial activity); 2 + where there is mild ac­ to the superior angle of the sca­ during shoulder activity. Before comm­ pula tivity (26-50% of maximal activity); 3+ encing the procedure, informed written E Horizontal line through T1 where there is moderate activity (51­ consent was obtained from all subjects. X Electrode site 80% of maximal activity) and; 4 + 102 The Australian Journal of PhYSiotherapy. Vol. 32, No.2, 1986 Levator Scapulae and Shoulder Pain of Cervical Origin where there is strong activity (81-100070 The instantaneous axes of rotation the right arm compared with resisted of maximal activity). Tbis study used for the scapula motion between 0 and abduction. The other four subjects the activity observed during resisted 90 degrees and 90 and 180 degrees of showed the reverse. shoulder abduction were determined by shoulder girdle elevation as the basis During free shoulder abduction on using the method described by White for grading (ie the 100070 value) as this the right side there was a slight ob­ and Panjabi (1978 p479).

Load more

  6

Copy Link