In vivo assessment of AP laxity in healthy shoulders using an instrumentedarthrometer

Arthrometric assessment for glenohumeral (GH) laxity is currently unprecede nted in orthopedic practice. Clinical evaluation of GH laxity is based on m anual tests that lack objectivity and reliability. We have developed an art hrometer that quantifies AP laxity relative to applied load. Forty healthy shoulders were assessed for AP laxity at 67-, 89-, 111-, and 134-N load lev els. A factorial ANOVA revealed significant mean (+/- SD) differences betwe en directions (p < .0001) and between loads (p < .001). Our results demonst rate the quantified relationship between applied directional loads and GH t ranslation in vivo. We determined bilateral symmetry within subjects and de monstrated excellent reproducibility of the device. Frequency distributions for AP laxity revealed a bell-shaped curve, indicating a normal distributi on. Anterior laxity was significantly greater then posterior laxity, and it demonstrated better compliance between the selected load levels.