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Glenohumeral Function of the Long Head of the Biceps Muscle: An Electromyographic Analysis.

Chalmers PN, Cip J, Trombley R, Cole BJ, Wimmer MA, Romeo AA, Verma NN - Orthop J Sports Med (2014)

Bottom Line: Optimal treatment of superior labral anterior-posterior (SLAP) tears is controversial, in part because the dynamic role of the long head of the biceps muscle (LHBM) in the glenohumeral joint is unclear.LHBM activity was significant increased by flexion and abduction (P < .049 in all cases), while SHBM activity was not.Biceps tenodesis may result in dynamic change within the glenohumeral joint with higher demand activities.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, USA.

ABSTRACT

Background: Optimal treatment of superior labral anterior-posterior (SLAP) tears is controversial, in part because the dynamic role of the long head of the biceps muscle (LHBM) in the glenohumeral joint is unclear. The aim of this study was to determine dynamic LHBM behavior during shoulder activity by studying (1) the electromyographic activity of the LHBM during shoulder motion, (2) the effect of elbow immobilization on this activity, and (3) the effect of a load applied to the distal humerus on this activity.

Hypothesis: The LHBM would not play a significant role in active glenohumeral range of motion.

Study design: Controlled laboratory study.

Methods: Thirteen normal volunteers underwent surface electromyography (EMG) measurement of the LHBM, short head biceps muscle (SHBM), deltoid, infraspinatus, and brachioradialis during shoulder motion from the neutral position (0° of rotation, flexion, and abduction) to 45° of flexion, 90° of flexion, 45° of abduction, and 90° of abduction. These motions were repeated both with and without splint immobilization of the forearm and elbow at 100° of flexion and neutral rotation and with and without a 1-kg weight placed on the lateral distal humerus.

Results: Mean EMG activity within the LHBM and the SHBM was low (≤11.6% ± 9.1%). LHBM activity was significant increased by flexion and abduction (P < .049 in all cases), while SHBM activity was not. EMG activity from the middle head of the deltoid was significantly increased by loading with the shoulder positioned away from the body (ie, in abduction or flexion). When compared with the unloaded state, the addition of a distal humeral load significantly increased LHBM activity in 45° of abduction (P = .028) and 90° of flexion (P = .033) despite forearm and elbow immobilization. The SHBM showed similar trends.

Conclusion: In normal volunteers with forearm and elbow immobilization and application of a load to the distal humerus, LHBM EMG activity is increased by both glenohumeral flexion and abduction, suggesting that this muscle plays a dynamic role in glenohumeral motion with higher demand activities.

Clinical relevance: Biceps tenodesis may result in dynamic change within the glenohumeral joint with higher demand activities.

No MeSH data available.


Related in: MedlinePlus

This series of clinical photographs shows electrode placement. (A) Anterior view demonstrating electrode placement on the long and short heads of the biceps. (B) Lateral view demonstrating electrode location on the middle head of the deltoid. (C) Posterior view showing electrode placement on the infraspinatus. A latissimus dorsi electrode is also shown, although this electrode was not used for this particular study.
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fig1-2325967114523902: This series of clinical photographs shows electrode placement. (A) Anterior view demonstrating electrode placement on the long and short heads of the biceps. (B) Lateral view demonstrating electrode location on the middle head of the deltoid. (C) Posterior view showing electrode placement on the infraspinatus. A latissimus dorsi electrode is also shown, although this electrode was not used for this particular study.

Mentions: The surface EMG (sEMG) of the muscle activity from each subject was collected using a TeleMyo transmitter and receiver, model 2400T/2400R (Noraxon Inc, Scottsdale, Arizona, USA). Prior to electrode application, the skin was cleaned using antimicrobial wipes.13 Self-adhesive dual Ag/AgCl electrodes (Noraxon Inc) were placed on the palpable muscle bellies of the brachioradialis, LHBM, SHBM, middle head of the deltoid, and infraspinatus muscles in parallel of the muscle fibers at the midpoint of the muscle with the muscle held in midflexion to optimize the signal. Figure 1 shows electrode placement. For the LHBM and short head electrodes, if the bulk of the biceps muscle was split into thirds, the LHBM electrodes lay at the junction of the lateral and middle thirds and the short head electrodes lay at the junction of the middle and medial thirds with a minimum of 3 cm between the short and long head electrodes mediolaterally to avoid cross-talk, as previous described.2,3,14 As an internal check, a cadaveric dissection was performed to confirm that the long and short heads of the biceps had entirely separate muscular fibers until their attachment at the distal tendon. This dissection is shown in Figure 2; the separate heads of the muscle have anatomically distinct fascicles without cross-weaving, with the LHBM being lateral and the SHBM being medial up until they coalesce at the distal tendon. EMG signals were preamplified (500×) near the electrodes, with the band pass filtered between 10 and 500 Hz and sampled at a rate of 1500 Hz.


Glenohumeral Function of the Long Head of the Biceps Muscle: An Electromyographic Analysis.

Chalmers PN, Cip J, Trombley R, Cole BJ, Wimmer MA, Romeo AA, Verma NN - Orthop J Sports Med (2014)

This series of clinical photographs shows electrode placement. (A) Anterior view demonstrating electrode placement on the long and short heads of the biceps. (B) Lateral view demonstrating electrode location on the middle head of the deltoid. (C) Posterior view showing electrode placement on the infraspinatus. A latissimus dorsi electrode is also shown, although this electrode was not used for this particular study.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2 - License 3
Show All Figures
getmorefigures.php?uid=PMC4555617&req=5

fig1-2325967114523902: This series of clinical photographs shows electrode placement. (A) Anterior view demonstrating electrode placement on the long and short heads of the biceps. (B) Lateral view demonstrating electrode location on the middle head of the deltoid. (C) Posterior view showing electrode placement on the infraspinatus. A latissimus dorsi electrode is also shown, although this electrode was not used for this particular study.
Mentions: The surface EMG (sEMG) of the muscle activity from each subject was collected using a TeleMyo transmitter and receiver, model 2400T/2400R (Noraxon Inc, Scottsdale, Arizona, USA). Prior to electrode application, the skin was cleaned using antimicrobial wipes.13 Self-adhesive dual Ag/AgCl electrodes (Noraxon Inc) were placed on the palpable muscle bellies of the brachioradialis, LHBM, SHBM, middle head of the deltoid, and infraspinatus muscles in parallel of the muscle fibers at the midpoint of the muscle with the muscle held in midflexion to optimize the signal. Figure 1 shows electrode placement. For the LHBM and short head electrodes, if the bulk of the biceps muscle was split into thirds, the LHBM electrodes lay at the junction of the lateral and middle thirds and the short head electrodes lay at the junction of the middle and medial thirds with a minimum of 3 cm between the short and long head electrodes mediolaterally to avoid cross-talk, as previous described.2,3,14 As an internal check, a cadaveric dissection was performed to confirm that the long and short heads of the biceps had entirely separate muscular fibers until their attachment at the distal tendon. This dissection is shown in Figure 2; the separate heads of the muscle have anatomically distinct fascicles without cross-weaving, with the LHBM being lateral and the SHBM being medial up until they coalesce at the distal tendon. EMG signals were preamplified (500×) near the electrodes, with the band pass filtered between 10 and 500 Hz and sampled at a rate of 1500 Hz.

Bottom Line: Optimal treatment of superior labral anterior-posterior (SLAP) tears is controversial, in part because the dynamic role of the long head of the biceps muscle (LHBM) in the glenohumeral joint is unclear.LHBM activity was significant increased by flexion and abduction (P < .049 in all cases), while SHBM activity was not.Biceps tenodesis may result in dynamic change within the glenohumeral joint with higher demand activities.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, USA.

ABSTRACT

Background: Optimal treatment of superior labral anterior-posterior (SLAP) tears is controversial, in part because the dynamic role of the long head of the biceps muscle (LHBM) in the glenohumeral joint is unclear. The aim of this study was to determine dynamic LHBM behavior during shoulder activity by studying (1) the electromyographic activity of the LHBM during shoulder motion, (2) the effect of elbow immobilization on this activity, and (3) the effect of a load applied to the distal humerus on this activity.

Hypothesis: The LHBM would not play a significant role in active glenohumeral range of motion.

Study design: Controlled laboratory study.

Methods: Thirteen normal volunteers underwent surface electromyography (EMG) measurement of the LHBM, short head biceps muscle (SHBM), deltoid, infraspinatus, and brachioradialis during shoulder motion from the neutral position (0° of rotation, flexion, and abduction) to 45° of flexion, 90° of flexion, 45° of abduction, and 90° of abduction. These motions were repeated both with and without splint immobilization of the forearm and elbow at 100° of flexion and neutral rotation and with and without a 1-kg weight placed on the lateral distal humerus.

Results: Mean EMG activity within the LHBM and the SHBM was low (≤11.6% ± 9.1%). LHBM activity was significant increased by flexion and abduction (P < .049 in all cases), while SHBM activity was not. EMG activity from the middle head of the deltoid was significantly increased by loading with the shoulder positioned away from the body (ie, in abduction or flexion). When compared with the unloaded state, the addition of a distal humeral load significantly increased LHBM activity in 45° of abduction (P = .028) and 90° of flexion (P = .033) despite forearm and elbow immobilization. The SHBM showed similar trends.

Conclusion: In normal volunteers with forearm and elbow immobilization and application of a load to the distal humerus, LHBM EMG activity is increased by both glenohumeral flexion and abduction, suggesting that this muscle plays a dynamic role in glenohumeral motion with higher demand activities.

Clinical relevance: Biceps tenodesis may result in dynamic change within the glenohumeral joint with higher demand activities.

No MeSH data available.


Related in: MedlinePlus