A three-dimensional comparative study on the scapulohumeral relationship in normal and osteoarthritic shoulders.
BACKGROUND
Eccentric loading due to humeral translation is associated with worse clinical outcomes in hemiarthroplasty and total shoulder arthroplasty. The purpose of this study was to evaluate the 3-dimensional relationship of the humeral head to the scapula (scapulohumeral relationship) in nonpathologic shoulders and in shoulders with primary osteoarthritis.


METHODS
Three-dimensional reconstructions of computed tomography scans of 151 nonpathologic shoulders (control group) and 110 shoulders with primary glenohumeral arthritis (OA group) were analyzed by measuring the anterior-posterior, inferior-superior, and medial-lateral position of the humeral head in relation to the scapula. Shoulders were classified as centered (type A) or posteriorly subluxed (type B) according to the Walch classification of glenoid morphology. Reproducibility and differences in scapulohumeral relationship were statistically analyzed.


RESULTS
The scapulohumeral relationship could be determined reliably: the intraclass correlation coefficient ranged between 0.780 and 0.978; the typical error of measurement ranged between 2.4% and 5.0%. Both type A and type B shoulders showed significant posterior translation of the humeral head (P <.001). Type B shoulders had significantly more posterior translation than type A shoulders (P <.001). A tendency of inferior translation was noted, although with only marginal statistical significance (P = .051). In each morphology class, a medial deviation of the humeral head, representing a reduced glenohumeral distance, was measured (P <.001).


CONCLUSIONS
The main characteristics of primary glenohumeral osteoarthritis are posterior humeral head translation relative to the scapula, reduced glenohumeral distance, and a tendency toward inferior humeral head translation in both type A and type B shoulders.
Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium; Department of Orthopaedic Surgery and Traumatology, University Hospital of Basel, Basel, Switzerland. Electronic address: matthijs.jacxsens@gmail.com.
Matthijs
M
Jacxsens
Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium.
Alexander
A
Van Tongel
Department of Orthopaedics and Department of Bioengineering, University of Utah, Salt Lake City, UT, USA.
Heath B
HB
Henninger
Department of Physical and Rehabilitation Medicine, Ghent University Hospital, Ghent, Belgium.
Brecht
B
De Coninck
Department of Orthopaedic Surgery and Traumatology, University Hospital of Basel, Basel, Switzerland.
Andreas M
AM
Mueller
Department of Orthopaedic Surgery and Traumatology, Ghent University Hospital, Ghent, Belgium.
Lieven
L
De Wilde
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D058430:Humeral Head / Q000000981:diagnostic imaging*; D021621:Imaging, Three-Dimensional; D008297:Male; D010003:Osteoarthritis / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012540:Scapula / Q000000981:diagnostic imaging*; D012785:Shoulder Joint / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed
3D CT reconstruction; 3D scapulohumeral relationship; glenohumeral relationship; glenohumeral subluxation; glenoid morphology; humeral head translation; total shoulder arthroplasty