In vivo quantification of capsular end-point in the nonimpaired glenohumeral joint using an instrumented measurement system.
METHODS
Single-group factorial.


OBJECTIVE
Quantify glenohumeral joint translations as a function of force using an instrumented measurement system. Our first specific aim was to compare the magnitude of force (N) required to reach capsular end-point between the anterior, posterior, and inferior directions. Our second specific aim was to compare the magnitude of translation (mm) at capsular end-point between the anterior, posterior, and inferior directions.


BACKGROUND
Manual force-displacement techniques are subjective in nature, and the clinician must rely on "feel" to determine capsular end-point. Several investigators have attempted to utilize more objective measures at the glenohumeral joint, however none have quantified the force or displacements necessary to achieve a true capsular end-point.


METHODS
An arthrometric technique was used to measure anterior, posterior, and inferior glenohumeral translations in 20 nonimpaired shoulders (11 women and 9 men with a mean age of 20.9 +/- 3.6 years).


RESULTS
The magnitude of applied force required to reach capsular end-point was significantly different between directions of translations. Anterior-directed translations required a significantly greater magnitude of applied force to reach capsular end-point than inferior-directed translations. The magnitude of translation was not significantly different between directions at capsular end-point.


CONCLUSIONS
Applied forces in the range of 181 to 203 N are necessary to reach capsular end-point in subjects with nonimpaired shoulders. Anterior translation required significantly higher forces (203.1 +/- 13.1 N) to reach capsular end-point than inferior translation (181.4 +/- 31.9 N).
Borsa
P A
PA
Division of Kinesiology, University of Michigan, Ann Arbor 48109-2214, USA. borsap@umich.edu
Sauers
E L
EL
Herling
D E
DE
Manzour
W F
WF
D000328:Adult; D000704:Analysis of Variance; D000886:Anthropometry / Q000379:methods*; D001696:Biomechanical Phenomena; D023381:Endpoint Determination; D004867:Equipment Design; D005260:Female; D006801:Humans; D017746:Joint Capsule / Q000502:physiology*; D007593:Joint Instability / Q000175:diagnosis; D008297:Male; D012785:Shoulder Joint / Q000502:physiology*