Radiographic characterization of the B2 glenoid: the effect of computed tomographic axis orientation.
BACKGROUND
Glenoid retroversion may accelerate glenoid loosening after total shoulder arthroplasty. Accurate measurement of preoperative glenoid deformity is critical for decision-making and prognostication. The purpose of this study was to determine whether glenoid version, inclination, and depth and humeral subluxation measurements on computed tomography (CT) scan slices oriented in the plane of the body differ from those oriented in the scapular plane and those obtained by automated 3-dimensional reconstruction software in the setting of a biconcave B2-type glenoid.


METHODS
Thirty-one preoperative CT scans in patients undergoing total shoulder arthroplasty with Walch B2-type glenoids underwent a standardized measurement protocol by 3 observers. Glenoid version, inclination, and depth and humeral subluxation were measured on 2-dimensional CT images in the plane of the body, on 2-dimensional images in the plane of the scapula, and by a validated, automated 3-dimensional software program.


RESULTS
Correction of CT slice axis into the plane of the scapula decreased measured retroversion by 2.4° to 4.7° (P < .004) and inclination by 21° (P < .001). Whereas uncorrected version measurements do not differ from automated software measurements, corrected measurements do (P < .001). Whereas corrected inclination measurements do not differ from automated measurements, uncorrected measurements do (P < .001). Automated measurements differed from both corrected and uncorrected subluxation (P < .001 in both cases).


CONCLUSIONS
If CT images are not reoriented into the plane of the scapula, version and inclination will be significantly overestimated. In the setting of a retroverted, deformed glenoid, automated software may produce similar inclination measurements to corrected 2-dimensional CT, but it produces significantly altered measurements of version and subluxation.
Department of Orthopaedic Surgery, Washington University Medical Center, St. Louis, MO, USA. Electronic address: p.n.chalmers@gmail.com.
Peter N
PN
Chalmers
Department of Orthopaedic Surgery, Washington University Medical Center, St. Louis, MO, USA.
Dane
D
Salazar
Department of Orthopaedic Surgery, Washington University Medical Center, St. Louis, MO, USA.
Aaron
A
Chamberlain
Department of Orthopaedic Surgery, Washington University Medical Center, St. Louis, MO, USA.
Jay D
JD
Keener
D000072228:Arthroplasty, Replacement, Shoulder; D005260:Female; D061165:Glenoid Cavity / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D012189:Retrospective Studies; D012540:Scapula / Q000000981:diagnostic imaging*; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods
Glenohumeral osteoarthritis; computed tomography; glenoid depth; glenoid inclination; glenoid version; total shoulder arthroplasty