Mechanics of Glenohumeral Instability.
Last updated Friday, February 04, 2005
Glenoid versionAbout the version Glenoid version is the angle that the glenoid center line makes with
the plane of the scapula (see figure 22). The glenoid center line
usually points a few degrees posterior to the plane of the scapula (see
figure 22). Changing the version of the glenoid articular surface
imposes a corresponding change in the humeroscapular positions in which
the net humeral joint reaction force will be contained by the effective
glenoid arc. Glenoid version may be altered by glenoid dysplasia (see
figure 23) (Wirth et al, 1993), fractures, glenoid osteotomy, (Wirth et
al, 1994) and glenoid arthroplasty. Abnormal glenoid version positions
the glenoid fossa in an abnormal relationship to the forces generated
by the scapulohumeral muscles. Normalizing abnormal glenoid version is
often a critical step in glenohumeral reconstruction.
Apparent changes in glenoid version can arise from loss of part of
the glenoid rim (see figures 24 and 25). (Breweret al, 1986; Hurley et
al, 1992; Randelli and Gambrioli, 1986) Dias et al found no difference
in apparent glenoid version between normal subjects and recurrent
anterior dislocators. (Dias et al, 1993) Dowdy and O'Driscoll (Dowdy
and O'Driscoll, 1994) found only minor variances of radiographic
glenoid version among patients with and without recurrence following
stabilization surgery. However, Hirschfelder and Kirsten (Hirschfelder
and Kirsten, 1991) found increased glenoid retroversion in both the
symptomatic and unsymptomatic shoulders of individuals with posterior
instability; Grasshoff et al (Grasshoff et al, 1991) found increased
anteversion in shoulders with recurrent anterior instability.
Changes in version may be difficult to quantitate on axillary
radiographs unless the view is carefully standardized. Even with
optimal radiographic technique, the important contributions of the
cartilage and labrum to the depth and orientation of the fossa (Howell
and Galinat, 1989; Soslowsky et al, 1992) cannot be seen on plain
radiographs or CT scans. When it is important to know the orientation
of the cartilaginous joint surface in relation to the scapular body a
double contrast CT scan is necessary.
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