Our findings may indicate a possible increased risk for instability in women, especially those participating in sports that require repetitive overhead-throwing motion. Future investigations should seek to determine the contribution of increased GH joint laxity and decreased joint stiffness to various injury states and examine these variables in other populations such as overhead-throwing athletes.

The purpose of this study was to objectively characterize in vivo glenohumeral joint laxity using an instrumented shoulder arthrometer. Secondary objectives were to examine the relationship of glenohumeral joint laxity with passive range of motion and generalized joint laxity. Fifty-one recreational athletes with no history of shoulder injury or long-term participation in overhead sports participated in this study. Anterior and posterior laxity data were obtained at displacement forces of 67, 89, 111, and 134 N. Bilateral passive shoulder range of motion measures were obtained, and a modified Beighton Mobility Score was used to quantify generalized joint laxity. There were no significant differences in glenohumeral joint laxity between the right and left shoulders (P values = 0.14 to 0.73). No significant differences in laxity were seen between directions (F(1,400) = 1.35, P = 0.25). However, significant differences were observed between force levels (F(3,400) = 27.17, P < 0.0001). No moderate or stronger correlations between laxity, passive range of motion, and generalized joint laxity were seen. These data confirm the presence of a wide spectrum of symmetric laxity in subjects that fails to correlate strongly with passive range of motion or generalized joint laxity.

This study assessed shoulder laxity using an instrumented arthrometer. We compared anterior and posterior translations at various force levels to determine the reliability of our measurement technique and to provide normative data in healthy shoulders. Fifty shoulders were assessed for glenohumeral joint laxity in two directions (anterior and posterior) and at four force levels (67, 89, 111, and 134 N). The dependent measure was joint displacement. Laxity values were widely, yet normally, distributed in our group of healthy shoulders. Intraclass correlation coefficients revealed excellent between-trial reliability (0.92) and fair between-session (0.73) and between-examiner (0.74) reliability. The average standard error of measurement between trials (0.56 mm), sessions (1.5 mm), and examiners (1.7 mm) demonstrated an unprecedentedly high degree of precision for quantifying glenohumeral joint laxity. Paired t tests revealed no significant laxity differences between sides (P>0.05), indicating bilateral symmetry. A 2 (direction) x 4 (force) analysis of variance revealed significant differences in laxity between directions (P<0.0001) and force levels (P<0.0001). Our results show that our instrumented technique for quantifying glenohumeral joint laxity is precise and reproducible. Posterior translation was significantly greater than anterior, and a significant increase in translation was observed between increasing levels of force.

No abstract

Arthrometric assessment for glenohumeral (GH) laxity is currently unprecedented in orthopedic practice. Clinical evaluation of GH laxity is based on manual tests that lack objectivity and reliability. We have developed an arthrometer that quantifies AP laxity relative to applied load. Forty healthy shoulders were assessed for AP laxity at 67-, 89-, 111-, and 134-N load levels. A factorial ANOVA revealed significant mean (± SD) differences between directions (p < .0001) and between loads (p < .001). Our results demonstrate the quantified relationship between applied directional loads and GH translation in vivo. We determined bilateral symmetry within subjects and demonstrated excellent reproducibility of the device. Frequency distributions for AP laxity revealed a bell-shaped curve, indicating a normal distribution. Anterior laxity was significantly greater then posterior laxity, and it demonstrated better compliance between the selected load levels.