The impact of rectification on the electrically evoked long-latency reflex of the biceps brachii muscle

Long latency reflexes (LLR) were elicited electrically and obtained by full wave rectified and non-rectified data recordings in 10 healthy subjects. After single or train stimuli (sensory radial nerve; interstimulus interval 3ms) amplitude and peak latency values were measured over the bent biceps brachii (BB) muscle, either without or with 1.5kg weight load. After rectification, mean LLR amplitude values made up 30% of the non-rectified data, independent from the stimulus type and weight load. In the non-rectified data, a significant gain in amplitude resulted from train stimuli compared with single stimuli, and from weight load compared to no weight load. No such significant difference was detected when rectified data were analysed. Furthermore, average amplitude values of rectified and non-rectified curves were studied using 11 sine waves and damped sine waves with equal phase intervals that were varied from 0° up to 34.4°. Phase shifts ranging from 10° to 25° resulted in excess amplitude decline of rectified data compared with non-rectified data. The long and polysynaptic course that LLR information takes leads to considerable overlap of responses to subsequent stimuli. This overlap of motor unit potentials forming the LLR obviously results in excess amplitude cancellation after rectification as shown for sine and damped sine waves. Rectification leads to an increase in the frequency content of the data that renders it prone to phase cancellation. In the present study, this cancellation was harmful as it prevented detection of important factors of influence such as stimulus strength and motor unit recruitment level.

An unusual case of an intramuscular lipoma of the biceps brachii

Lipomas are common benign neoplasms consisting of mature fatty tissue. They are usually of roundish or ovoid shape and are situated in a single anatomical region. They most frequently occur on the back and in the extremities. Most lipomas are subcutaneous and require no imaging evaluation. When deep, large and unusual in location, MRI can identify and localise these tumours and is the best exploration to differentiate lipoma and lipo-sarcoma. We describe a case of a patient with an intramuscular lipoma of the biceps brachii.

Relevant anatomic landmarks and measurements for biceps tenodesis

BACKGROUND

Biceps tenodesis around the pectoralis major insertion may alter resting tension on the biceps, leading to unfavorable clinical outcomes.

HYPOTHESIS

The anatomic relationship between the musculotendinous junction (MTJ) of the biceps and the pectoralis major tendon will provide guidelines for anatomic location to perform biceps tenodesis with the goal of re-establishing biceps tension.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Cadaveric dissections were performed that reflected the pectoralis major tendon and exposed the long head of the biceps tendon (LHBT). Calipers were used to measure the longitudinal width of the pectoralis major tendon at the humerus, 2 cm away from the humerus, and at its proximal expansion on the humerus. The distance from the proximal extent of the pectoralis major tendon footprint to the beginning of the MTJ of the biceps and the length of the MTJ of the biceps were recorded. The location of the distal end of the MTJ of the biceps relevant to the inferior border of the pectoralis major tendon was calculated.

RESULTS

The average longitudinal width of the pectoralis major tendon at its humeral insertion was 76.8 mm, the width 2 cm away from the humerus averaged 37.3 mm, and the proximal expansion averaged 13.3 mm. The MTJ of the biceps began an average of 32.4 mm distal from the proximal aspect of the pectoralis major footprint and extended for an average of 78.1 mm. The MTJ of the LHBT was calculated to extend 3.3 cm distal to the inferior border of the pectoralis major footprint.

CONCLUSION

The MTJ of the biceps begins further proximal than may be appreciated intraoperatively. Knowledge of the anatomic relationships between the LHBT, its MTJ, and the pectoralis major tendon provides helpful guidelines for the biceps tenodesis site. The final resting spot of the most distal aspect of the MTJ of the LHBT after tenodesis should be approximately 3 cm distal to the inferior edge of the pectoralis major tendon footprint on the humerus.

Rapid plasticity of motor corticospinal system with robotic reach training

Goal-directed reaching is important for the activities of daily living. Populations of neurons in the primary motor cortex that project to spinal motor circuits are known to represent the kinematics of reaching movements. We investigated whether repetitive practice of goal-directed reaching movements induces use-dependent plasticity of those kinematic characteristics, in a manner similar to finger movements, as had been shown previously. Transcranial magnetic stimulation (TMS) was used to evoke upper extremity movements while the forearm was resting in a robotic cradle. Plasticity was measured by the change in kinematics of these evoked movements following goal-directed reaching practice. Baseline direction of TMS-evoked arm movements was determined for each subject. Subjects then practiced three blocks of 160 goal-directed reaching movements in a direction opposite to the baseline direction (14 cm reach 180° from baseline direction) against a 75-Nm spring field. Changes in TMS-evoked whole arm movements were assessed after each practice block and after 5 min following the end of practice. Direction and the position of the point of peak velocity of TMS-evoked movements were significantly altered following training and at a 5-min interval following training, while amplitude did not show significant changes. This was accompanied by changes in the motor-evoked potentials (MEPs) of the shoulder and elbow agonist muscles that partly explained the change in direction, mainly by increase in agonist MEP, without significant changes in antagonists. These findings demonstrate that the arm representation accessible by motor cortical stimulation under goes rapid plasticity induced by goal-directed robotic reach training in healthy subjects.

Arthroscopic evaluation and treatment of biceps brachii long head tendon injuries: A survey of the MOON shoulder group

Context:

Injuries to the biceps brachii long head tendon commonly occur in conjunction with tears in the rotator cuff and glenoid labrum. Consensus on treatment of varying levels of severity is undetermined.

Settings and Design:

We surveyed members of the Multicenter Orthopedic Outcomes Network (MOON) Shoulder Group, to determine a consensus on arthroscopic grading and treatment.

Aims:

We hypothesized that the Lafosse classification system would show a high level of inter- and intraobserver agreement regarding grading/treatment.

Materials and Methods:

Arthroscopic videos of 30 patients determined to have biceps brachii long head tendon injuries were viewed by 13 surgeons. The surgeons graded the severity of the injury macrostructure based on the Lafosse classification system and chose from a list of treatment options. Four months later the same surgeons viewed the same videos and repeated the survey.

Statistical Analysis Used:

Analysis with weighted and non-weighted Kappa values was performed to determine intra- and interobserver reliability for severity grading and to determine the preferred treatments for each level of severity.

Results:

Intraobserver reliability testing for the Lafosse system showed substantial agreement after two rounds (81.28%, K=0.7006). Interobserver testing demonstrated substantial agreement for Grade 0 (K=0.7152), fair agreement for Grade 1 (K=0.3803), and moderate agreement for Grade 2 (K=0.5156). Combined responses recommended no surgical treatment for 95.4% of the lesions classified as grade 0 (62/65). No surgical treatment was recommended for Grade 1 lesions in 24.1% of the cases (35/145), debridement in 38.6% (56/145), and tenotomy or tenodesis in 37.2% (54/145). Evaluators preferred tenotomy or tenodesis for 98.3% of the Grade 2 lesions (177/180).

Conclusions:

Analysis of the Lafosse system indicated substantial intraobserver reliability for all grades. As Grades 1 and 2 showed only fair and moderate agreement, a need for a reliable grading system still exists. Grade 2 lesions should be treated with tenotomy or tenodesis. A preferred treatment for Grade 1 lesions could not be determined given the high variability of responses. Higher-powered surveys may help determine the ideal treatment of Grade 1 injuries.

Muscle activation during low-intensity muscle contractions with varying levels of external limb compression

The purpose was to investigate muscle activation during low- intensity muscle contractions with various levels of external limb compression to reduce muscle perfusion/outflow. A series of unilateral elbow flexion muscle contractions (30 repetitive contractions followed by 3 sets x 15 contractions) was performed at 20% of 1RM with varying levels of external compression (0 (without compression), 98, 121, and 147 mmHg external compression) around the upper arm. Electromyography (EMG) signals were recorded from surface electrodes placed on the biceps brachii muscle and analyzed for integrated EMG (iEMG). Maximal voluntary isometric contraction (MVC) decreased similarly during the control (0 mmHg) and 98 mmHg external compression bout (~18%); the decline in MVC with 121 and 147 mmHg external compression was significantly greater (~37%). Muscle activation increased progressively throughout the contraction bout with each level of external compression, but iEMG was significantly greater during 147 mmHg external compression. In conclusion, low-intensity muscle contractions performed with external compression of 147 mmHg appears to alter muscle perfusion/outflow leading to increased muscle activation without decrements in work performed during the contraction bout. Key pointsLow-intensity muscle contractions with external compression are maintained by greater neural activation.It appears there is optimal external compression pressure for increased muscle activation without exaggerated fatigue.External compression per arm circumference was related to the neuromuscular response and fatigue.

Unilateral four-headed pectoralis muscle major

A unilateral four-headed pectoralis major muscle was observed on the left side of an 83 year-old Caucasian male cadaver. The accessory tendon arises from the lateral aspect of the pectoralis major muscle, travels along with the tendon of the long head of the biceps brachii and blends into the capsule of the shoulder joint. This anomaly is rare. A complete or partial absence of pectoralis major muscle is normally reported. Additionally, supernumerary heads of muscles other than pectoralis major have been documented. However, the existence of an accessory tendon to the pectoralis major muscle is unique. The implications of such a finding are discussed.

Rupture of the distal biceps tendon in a collegiate football player: a case report

OBJECTIVE

To provide health care personnel with guidelines for the management of a distal biceps tendon rupture.

BACKGROUND

Traumatic ruptures of the biceps tendon are rare, but serious, and usually involve the long head of the proximal insertion. Ruptures of the distal tendon account for only 3% of all biceps tendon ruptures. A history of tendinitis, overuse, or anabolic steroid abuse may predispose tendons to rupture. Surgical repair, followed by a comprehensive rehabilitation program, is indicated to regain full strength and range of motion in both flexion and supination.

DIFFERENTIAL DIAGNOSIS

Rupture of the distal head of the biceps brachii muscle at the insertion on the radial tuberosity.

TREATMENT

After the injury, the athlete continued to compete for the remainder of the collegiate football season. He then underwent surgery to repair the tendon at its insertion. Post- operatively, the athlete was immobilized in a cast and then a brace to prevent any movement of the muscle. Rehabilitation proceeded with isometric exercises and manual resistive exercises of the shoulder and wrist. At 16 weeks, the athlete was cleared for biceps curls and wrist supination. At 6 months, the athlete had regained full use of the muscle.

UNIQUENESS

This is a relatively rare injury, usually occurring at the proximal tendon insertion and in those who are middle aged (30 to 50 years old). Also, the surgical intervention in this case was delayed without detrimental effects to the patient.

CONCLUSIONS

This study shows that, while surgical intervention to repair a ruptured distal biceps tendon is necessary, appropriate conservative measures can be taken to allow surgery to be delayed without harm to the patient. The athletic trainer should be aware of how to recognize and treat this injury.