The stabilizing mechanism of the Latarjet procedure: a cadaveric study.
BACKGROUND
The Latarjet procedure has been used commonly for extra-articular treatment of anterior glenohumeral joint instability. Recently, the technique also has been used as a bone-grafting procedure to repair large glenoid defects. The "sling effect" and the "bone-block effect" have been proposed as the stabilizing mechanisms of this procedure. The aim of this study was to determine the stabilizing mechanisms of this procedure.


METHODS
Eight fresh-frozen shoulders were prepared and tested with use of a custom testing machine instrumented with a load cell. With a 50-N axial force applied to the humerus, the humeral head was translated anteriorly. Translational force was measured at both the end-range and the mid-range arm positions, with the capsule intact, after creation of a Bankart lesion, after creation of a large glenoid defect, and after the Latarjet procedure with no load and then three different sets of loads applied to the subscapularis and conjoint tendons. Then, these two tendons were removed to observe the contribution of the sling effect to the stability. Finally, the sutures attaching the coracoacromial ligament to the capsular flap were removed in order to observe the effect of that attachment.


RESULTS
The translational force, which decreased significantly after creation of a Bankart lesion or a large glenoid defect, returned to the intact-condition level after the Latarjet procedure was performed. At the end-range arm position, the contribution of the sling effect by the subscapularis and conjoint tendons was 76% to 77% as the load changed, and the remaining 23% to 24% was contributed by the suturing of the capsular flap. At the mid-range position, the contribution of the sling effect was 51% to 62%, and the remaining 38% to 49% was contributed by the reconstruction of the glenoid.


CONCLUSIONS
The main stabilizing mechanism of the Latarjet procedure was the sling effect at both the end-range and the mid-range arm positions.


CONCLUSIONS
The Latarjet procedure remains an effective procedure for restoring stability to an unstable glenohumeral joint, particularly when there is glenoid bone deficiency.
Biomechanics Laboratory, Division of Orthopedic Research, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
Nobuyuki
N
Yamamoto
Takayuki
T
Muraki
Kai-Nan
KN
An
John W
JW
Sperling
Robert H
RH
Cofield
Eiji
E
Itoi
Gilles
G
Walch
Scott P
SP
Steinmann
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000379:methods*; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery*; D013536:Suture Techniques; D013710:Tendons / Q000601:surgery