Relationships Among Measures of Impairment, Functional Limitation, and Disability in Patients with Shoulder Disorders.
Leggin BG, Kelley MJ, Ramsey ML, Glaser DA, Williams GR, Lannotti JP. 
University of Pennsylvania Medical Center - Presbyterian, Philadelphia , PA.

 INTRODUCTION:  Clinical research has historically focused on impairment based outcome measures such as pain, range of motion, and muscle force.  Recently, clinical research has shifted focus to self-report measures of function and disability.  Little is know about the relationship among impairments, functional limitations, and disability in patients with shoulder disorders. 

PURPOSES:  The purposes of this report were to 1) examine the relationships among measures of impairment, function, and disability in patients with shoulder disorders, and 2) attempt to predict the level of impairment associated with the ability to perform selected functional activities.  

METHOD:  Ninety-four men (mean age = 45.5) and eighty women (mean age = 52.1) with a variety of shoulder pathologies were included in the study.  All patients completed the PENN Shoulder Score (PSS).  The clinical impairment measures were active range of motion and muscle force.  Four planes of active range of motion were measured including forward elevation (FE), external rotation (ER) in adduction and at 90° abduction, and internal rotation (IR) up the back.  Muscle force measurements included internal and external rotation with the shoulder adducted and elevation at 45° in the plane of the scapula. 

RESULTS:  Correlation coefficients for the relationship between the PENN Shoulder Score and measures of range of motion and strength ranged from r = 0.30 to r = 0.63.  Forward elevation correlated with PSS total score (r = 0.63), the function subscale (0.68), and individual items of function (r = 0.37 –0.63).  External rotation in adduction did not correlate well with either PSS total score or any of the subscales.  ER at 90° correlated with PSS total score (r = 0.49), the function subscale (r = 0.55), and individual items of function (r = 0.28 – 0.54).  IR correlated with PSS total score (r = 0.53), the function subscale (r = 0.56), and individual items of function (r = 0.30 – 0.63).  Measures of muscle force did not correlate well with the total score, but had fair correlation with the function subscale (r = 0.43 – 0.47).  The pain subscale correlated with the satisfaction and function subscales (r = 0.53 & 0.70 respectively), the total score  (r = 0.86), and individual items of function (0.43 – 0.59).  Satisfaction correlated with the total score (r = 0.68), function (r = 0.54), the ability to sleep on the affected side (r = 0.50), the ability to perform usual recreational activity (r = 0.52) and the ability to use arm for overhead sports (r = 0.56).  Linear regression analysis revealed that a curvilinear relationship exists among measures of range of motion, muscle force and Penn Shoulder Score corresponding to the level of difficulty reported with selected functional measures. 

CONCLUSIONS:  Positive correlations were noted among measures of impairment, functional limitation, and disability.  A linear relationship exists between selected impairment measures and selected functional measures corresponding to the level of difficulty reported by patients.  Clinicians can use this data to help make treatment decisions in patients with shoulder disorders