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In vivo technique to quantify the internal‐external rotation kinematics of the human glenohumeral joint
Author(s) -
Novotny John E.,
Woolley C. Todd,
Nichols Claude E.,
Beyn Bruce D.
Publication year - 2000
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.1100180205
Subject(s) - kinematics , range of motion , rotation (mathematics) , moment of inertia , moment (physics) , flexibility (engineering) , torque , rigidity (electromagnetism) , orthodontics , external rotation , physics , mathematics , medicine , geometry , surgery , classical mechanics , statistics , quantum mechanics , thermodynamics
Internal and external rotation of the humerus are often related to instability, injury mechanisms, and surgical and rehabilitation outcomes at the glenohumeral joint. The goal of this study was to develop a technique to quantify the internal‐external rotation kinematics of the glenohumeral joint in human subjects, including the rotational range of motion, neutral‐zone laxity, and flexibility. For both arms of 10 normal subjects, the rotational range of motion of the humerus was assessed at 45° of abduction with 4 Nm of appplied moment to produce internal and external rotations about the long axis. The neutral zone was defined as the portion of the rotational range of motion that occurred between +1 and −1 Nm of applied internal‐external rotation torque. The flexibility was determined from the slope of the moment‐rotation curve from 1 to 4 Nm of applied moment. The repeatability of the device during two trials on the same day and two trials 1 week apart was determined. There were no significant differences between the two same‐day and two across‐day trials for each outcome measure. The internal‐external rotational range of motion was 139.4° (SD 40.5°). The neutral‐zone laxity was 77.8° (SD 46.0°). With a linear approximation, the external rotation flexibility (20.1° Nm [SD 13.7°/Nm]) was four times greater than the internal rotation flexibility (5.8°/Nm [SD 5.1°/Nm]). The changes in the magnitude of the laxity, the ratio between the laxity and the range of motion, or the values for flexibility determined with this technique could be used to describe joint laxity, surgical outcome, and rehabilitation progress.