Comparison of Glenoid Version and Posterior Humeral Subluxation in Patients With and Without Posterior Shoulder Instability.
OBJECTIVE
To evaluate glenoid version and humeral subluxation on preoperative multiplanar imaging of patients who underwent surgery for posterior glenohumeral instability compared with a matched group of patients who had shoulder surgery for other pathology.


METHODS
All patients over a 2-year period who underwent surgery for posterior instability had preoperative magnetic resonance (MR) imaging or MR arthrogram reviewed. Patients undergoing shoulder surgery for reasons other than instability were identified as a control group and matched by sex, laterality, and age. Measurement of glenoid version and percentage of humeral subluxation was performed by 2 reviewers after completing a tutorial. Reviewers were blinded to diagnosis and to whether or not the patients were in the experimental or control group.


RESULTS
There were 41 patients in each group. The average glenoid version in the control group was 5.6° of retroversion (standard deviation [SD] 3.0), and the average humeral subluxation was 54% (SD 5.1%). In the experimental group, the average glenoid version was 8.1° of retroversion (SD 5.0). The average humeral subluxation in the experimental group was 56% (SD 6.8%). Student t test revealed a statistically significant difference in glenoid version (P = .009) but not humeral subluxation (P = .25). Intra- and inter-rater reliability was measured by the intraclass correlation coefficient and found to have an excellent Fleiss rating with regard to both measurements.


CONCLUSIONS
Glenoid retroversion is significantly increased in patients with symptomatic posterior labral tears compared with a control group. However, there was no statistically significant difference between the groups with regard to posterior humeral subluxation and, therefore, is not a reliable indicator of the presence or absence of symptomatic posterior shoulder instability.


METHODS
Level III, retrospective comparative study.
Department of Orthopaedic Surgery, Eisenhower Army Medical Center, Fort Gordon, Georgia, U.S.A.. Electronic address: Stephen.a.parada@gmail.com.
Stephen A
SA
Parada
Department of Orthopedic Surgery, Madigan Army Medical Center, Tacoma, Washington, U.S.A.
Josef K
JK
Eichinger
Department of Orthopaedic Surgery, University Specialty Clinics, Columbia, South Carolina, U.S.A.
Guillaume D
GD
Dumont
Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Lauren E
LE
Burton
Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Maggie S
MS
Coats-Thomas
Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Stephen D
SD
Daniels
Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Nathan J
NJ
Sinz
Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Matthew T
MT
Provencher
Department of Orthopedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Laurence D
LD
Higgins
Department of Orthopedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, U.S.A.
Jon J P
JJ
Warner
D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000000981:diagnostic imaging* / Q000601:surgery; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000601:surgery; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012785:Shoulder Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D055815:Young Adult