The influence of ankle joint movement on knee joint kinesthesia at various movement velocities.

The purpose of this study was to determine if gastrocnemius elongation or shortening and direction and velocity of knee movement influenced knee kinesthesia. Healthy volunteers sat with their knee flexed (20 degrees) and was then passively rotated (flexion or extension) at three velocities (0.5, 2, or 10 degrees/s) while the ankle was either fixed or rotated (dorsiflexed or plantar flexed at 0.17, 0.65, or 3.3 degrees/s) creating gastrocnemius elongation or shortening. Subjects activated a thumb switch, stopping motion once they detected onset and direction of the motion. Detection of passive movement sense (DPMS) was the angular movement before activation of a thumb-switch. Significant differences (P=0.003) in the rate of change in DPMS across a variety of movement velocities was observed but shortening or elongation of the gastrocnemius did not affect DPMS. Gastrocnemius elongation/shortening did not affect knee DPMS, simple reaction time plays an important role in testing kinesthesia especially at faster movements. While feedback from the gastrocnemius muscle plays a limited role in healthy subjects, differences in testing velocities may incorporate higher levels of central nervous system processing. Clinical measures of kinesthesia can be affected by both movement direction and movement velocity that are speed dependent.

Scapulothoracic latent muscle reaction timing comparison between trained overhead throwers and untrained control subjects.

AIM: This study evaluated select scapulothoracic muscles for training-induced latent muscle reaction timing (LMRT) changes. Comparisons were also made between the dominant and non-dominant upper extremities and between individual muscles. MATERIALS AND METHODS: Fifteen male trained overhead throwers (college baseball pitchers) and 15 male untrained, age-matched control subjects participated in this study. Scapulothoracic muscle activation data were collected as subjects attempted to stop a variably timed, sudden glenohumeral joint internal rotation perturbation. RESULTS: Training group differences were not evident for LMRT (P=0.56), however upper extremity dominance (P=0.003) and test muscle (P=0.0002) displayed significant differences. Dominant upper extremity upper trapezius muscle LMRT (72.5+/-26 ms) occurred later than non-dominant upper trapezius muscle LMRT (60.0+/-14.1 ms, P=0.001). Dominant upper extremity middle trapezius-rhomboid muscle LMRT (60.0+/-16.2 ms) occurred later than non-dominant middle trapezius-rhomboid muscle LMRT (50.2+/-12.6 ms, P=0.004). Dominant upper extremity upper trapezius muscle LMRT also occurred later than serratus anterior (55.7+/-16.0 ms, P=0.001) and middle trapezius-rhomboid LMRT (60.2+/-16 ms, P=0.003). Mean overall dominant upper extremity LMRT (62.7+/-19.4 ms) was delayed compared with mean overall non-dominant upper extremity LMRT (53.9+/-12.4 ms, P=0.003). CLINICAL CONSEQUENCES: Although training was not found to influence scapulothoracic LMRT, differences were observed between the dominant and non-dominant upper extremities. Consistent LMRT delays at the dominant upper extremity suggest possible neuromuscular timing differences to enable prolonged glenohumeral joint and scapulothoracic articulation acceleration before deceleration through eccentric muscle activation. Both trained and untrained overhead throwers displayed this response. Variable perturbation test velocities, and in-season testing of larger subject groups may be needed to better elucidate the more subtle differences associated with training.

Open reduction internal fixation after displacement of a previously nondisplaced acromial fracture in a multiply injured patient: case report and review of literature.

SUMMARY: A twenty-eight-year-old multiple trauma patient had a nondisplaced acromion fracture that was not detected until after it had displaced. Open reduction internal fixation was performed without complication and the patient achieved excellent shoulder abduction strength. Nondisplaced acromion fractures may displace if not protected. Open reduction internal fixation of displaced acromion fractures should be considered if deltoid muscle strength is important to the patient.

Shoulder proprioception: latent muscle reaction times.

PURPOSE: The purpose of this study was to identify electromyographic (EMG) differences in the latent muscle reaction timing (LMRT) of the rotator cuff between trained overhead throwers and control subjects in response to sudden internal rotation perturbation (P < or = 0.05). METHODS: Subjects included 15 trained overhead throwers (male intercollegiate baseball players) and 15 untrained subjects (males not active in competitive throwing sports). Subjects were tested while seated, with their dominant glenohumeral joint positioned in 90 degrees abduction/external rotation (scapular plane), their elbow flexed to 90 degrees, and their forearm placed in the perturbation device. Rotator cuff LMRT was assessed as they tried to decelerate a variably timed, sudden internal rotation force. EMG sampling (2000 Hz, 2-s duration) began immediately before perturbation. RESULTS: Trained throwers had slower infraspinatus (P = 0.011) and teres minor (P = 0.024) LMRT and decreased supraspinatus (P = 0.001) and posterior deltoid (P = 0.0001) muscle activation duration compared with control subjects. CONCLUSIONS: These results suggest that the rotator cuff muscles of trained throwers may be downregulated in response to sudden internal rotation perturbation. Although these adaptations would enable greater internal rotation velocities during overhead throwing, they may also contribute to glenohumeral joint pathology. The identification of changes in rotator cuff LMRT in response to sudden internal rotation perturbation suggests an area of acquired neuromuscular imbalance warranting consideration by those involved in the rehabilitation and conditioning of the overhead throwing athlete.

Scapular avulsion fracture of a high school wrestler.

This case study details a rare injury managed conservatively with aggressive therapy with early return to competition. A 17-year-old high school wrestler suffered indirect trauma to the right upper extremity. The patient was forced to the mat where he felt pain in the posterior aspect of his shoulder and was point tender over the inferior pole of his right scapula. Radiographs reveal an avulsion fracture at the inferior angle of the scapula. Aggressive therapy included modalities to control inflammation and muscle guarding in addition to early scapular mobility. Maintenance of glenohumeral motion and upper extremity strengthening was started within a week. The patient was able to wrestle in the state tournament 3 weeks after initial injury. At the 6-month follow-up, the patient had no clinical tenderness, full range of motion, and no motor deficits. The outcome resulted in clinical and radiological healing of the fracture and no functional deficits.