***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Objective : First , to vali date an ultrasonographic measure of the acromio-humeral distance ( AHD ) ; second , to compare the AHD variation during active abduction in patients with shoulder impingement syndrome ( SIS ) and healthy subjects ; and third , to evaluate the relationship between functional status and AHD variations before and after rehabilitation in SIS subjects . Design : This study has 3 components : ( 1 ) a reliability study , ( 2 ) a case-control study , and ( 3 ) a preliminary pretreatment/posttreatment clinical trial . Setting : Primary care hospital setting . Participants : Seven SIS patients and 13 healthy subjects . Interventions : For the clinical trial , the SIS subjects participated in 12 sessions of a rehabilitation program over 4 weeks . Main Outcome Measures : First , intraclass correlation coefficient for interobserver reliability ; second , AHD measured at 0 ° , 45 ° , and 60 ° of active abduction ; and third , Western Ontario Rotator Cuff Index . Results : Intraclass correlation coefficient for interobserver reliability ranged from 0.86 to 0.92 for the 3 shoulder positions . A significant reduction of the AHD was found within groups between rest and active abduction ( P < 0.05 ) . Comparison of AHD between groups was not statistically different ( P = 0.06 ; β < 0.80 ) . In pre-post rehabilitation analysis , improvement of the Western Ontario Rotator Cuff Index score was positively correlated to the reduction of the AHD narrowing as the arm was abducted ( r = 0.86 ; P = 0.01 ) . Conclusions : The ultrasound measure of AHD is reliable and sensitive . Although a distinct pattern of AHD variation in SIS patients could not be confirmed , a strong positive relationship was found between the reduction of AHD narrowing and functional improvement following rehabilitation . Ultrasound measurement of AHD might help identify SIS patients who will benefit from rehabilitation A method for directly measuring the position of the humeral head on the face of the glenoid in different positions of abduction of the arm was developed . We studied three subject groups : 12 patients with normal shoulders ( group 1 ) , 15 patients with stage II impingement syndrome ( group 2 ) , and 20 patients with rotator cuff tears or stage III impingement ( group 3 ) . The study consisted of a series of anteroposterior roentgenograms in the plane of the scapula with the arm in neutral rotation . Roentgenograms were obtained at 20 degrees intervals as the arm was elevated in the plane of the scapula from 0 degree to 120 degrees . Patients held a weight equal to 2 1/2 % of body weight in the h and . The parameters measured were excursion of the humeral head on the glenoid face , expressed as the distance that the center of the head lies above or below the center of the glenoid , arm angle , scapulothoracic angle , and glenohumeral angle . For patients with normal shoulders ( group 1 ) , there was no significant change in position of the humeral head with arm elevation . In contrast , those with stage II impingement ( group 2 ) had significant ( p < 0.05 ) superior displacement of the center of the humeral head with arm elevation . Patients with rotator cuff tears ( group 3 ) demonstrated a significant rise ( p < 0.05 ) during the first 40 degrees of abduction . The average position of the humeral head in the two pathologic patient groups was superior ( p < 0.05 ) to the average head position in the normal patient group . There was no significant difference in head position between patients with stage II impingement and patients with rotator cuff tear . The ratio of the glenohumeral angle to the scapulothoracic angle during abduction was calculated for our patient groups . In both patient groups , arm abduction had a larger scapulothoracic component than for normal shoulders . The superior migration of the humeral head is a probable result of cuff failure , either partial or complete 
    Output:
    
There was strong evidence for the reliability of ultrasound for measuring AHD , with moderate evidence for MRI and CT measures and conflicting evidence for radiographic methods .
The reliability of AHD measurement using radiographs has not been supported by the studies review ed