The addition of rotator interval closure after arthroscopic repair of either anterior or posterior shoulder instability: effect on glenohumeral translation and range of motion.
BACKGROUND
Although the use of rotator interval closure is frequently advocated as a useful supplement to shoulder instability repairs, the addition of a rotator interval closure after arthroscopic instability repair has not been fully investigated.


OBJECTIVE
The objective of this study was to investigate whether a rotator interval closure improves glenohumeral stability in an anterior and posterior instability shoulder model.


METHODS
Controlled laboratory study.


METHODS
Fourteen fresh-frozen cadaveric shoulder specimens were dissected free of soft tissues, leaving the rotator cuff intact with simulated cuff loading. All specimens were mounted in a custom testing apparatus using infrared sensors to document glenohumeral translation and rotation. The specimens were then tested for stability in the following order: vented/subluxated state, after arthroscopic anterior (Group 1; 7 specimens) or posterior (Group 2; 7 specimens) instability repair with suture anchors, and then after rotator interval closure. For each of the 3 testing conditions, the following were measured: (1) external and internal rotation at neutral, (2) external and internal rotation at 90 degrees of abduction, (3) posterior and anterior translation at neutral rotation (15 N and 25 N), (4) anterior translation at 90 degrees of abduction and external rotation (Group 1; 15 N and 25 N), (5) posterior translation at 90 degrees of flexion and internal rotation (Group 2; 15 N and 25 N), and (6) sulcus testing in neutral (7.5 N).


RESULTS
Posterior stability was only improved after anchor capsulolabral repair (8.0 to 5.0 mm; P = .017, 25 N), but there was no improvement after rotator interval closure (5.0 to 4.6 mm; P = .453). However, anterior stability was improved after capsulolabral repair (8.6 to 4.0 mm; P = .016, 25 N) and also improved further by rotator interval closure (4.0 to 2.4 mm; P = .007). The mean loss of external rotation was significantly increased by the addition of the rotator interval closure in both neutral and abducted glenohumeral positions, with a mean external rotation loss of 28 degrees in neutral (P = .013). The addition of a rotator interval closure did not improve sulcus stability (P = .4).


CONCLUSIONS
The addition of an arthroscopic rotator interval closure after posterior capsulolabral repair did not improve posterior stability; however, anterior stability was improved further after a rotator interval closure. Inferior stability was not improved. Arthroscopic rotator interval closure significantly decreased external rotation at both neutral and abducted arm positions.


CONCLUSIONS
Arthroscopic closure may be beneficial in certain cases of anterior shoulder instability; however, posterior instability was not improved. Predictable losses of external rotation after rotator interval closure are of concern.
Mologne
Timothy S
TS
Sports Medicine Center, Appleton, Wisconsin, USA.
Zhao
Kristin
K
Hongo
Michio
M
Romeo
Anthony A
AA
An
Kai-Nan
KN
Provencher
Matthew T
MT
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001182:Arthroscopy / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008875:Middle Aged; D016059:Range of Motion, Articular; D017006:Rotator Cuff / Q000601:surgery*; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery*