Biomechanical Effects of Acromioplasty on Superior Capsule Reconstruction for Irreparable Supraspinatus Tendon Tears.
BACKGROUND
Acromioplasty is increasingly being performed for both reparable and irreparable rotator cuff tears. However, acromioplasty may destroy the coracoacromial arch, including the coracoacromial ligament, consequently causing a deterioration in superior stability even after superior capsule reconstruction.


OBJECTIVE
The purpose of this study was to investigate the effects of acromioplasty on shoulder biomechanics after superior capsule reconstruction for irreparable supraspinatus tendon tears. The hypothesis was that acromioplasty with superior capsule reconstruction would decrease the area of subacromial impingement without increasing superior translation and subacromial contact pressure.


METHODS
Controlled laboratory study.


METHODS
Seven fresh-frozen cadaveric shoulders were evaluated using a custom shoulder testing system. Glenohumeral superior translation, the location of the humeral head relative to the glenoid, and subacromial contact pressure and area were compared among 4 conditions: (1) intact shoulder, (2) irreparable supraspinatus tendon tear, (3) superior capsule reconstruction without acromioplasty, and (4) superior capsule reconstruction with acromioplasty. Superior capsule reconstruction was performed using the fascia lata.


RESULTS
Compared with the intact shoulder, the creation of an irreparable supraspinatus tear significantly shifted the humeral head superiorly in the balanced muscle loading condition (without superior force applied) (0° of abduction: 2.8-mm superior shift [P = .0005]; 30° of abduction: 1.9-mm superior shift [P = .003]) and increased both superior translation (0° of abduction: 239% of intact [P = .04]; 30° of abduction: 199% of intact [P = .02]) and subacromial peak contact pressure (0° of abduction: 308% of intact [P = .0002]; 30° of abduction: 252% of intact [P = .001]) by applying superior force. Superior capsule reconstruction without acromioplasty significantly decreased superior translation (0° of abduction: 86% of intact [P = .02]; 30° of abduction: 75% of intact [P = .002]) and subacromial peak contact pressure (0° of abduction: 47% of intact [P = .0002]; 30° of abduction: 83% of intact [P = .0005]; 60° of abduction: 38% of intact [P = .04]) compared with after the creation of a supraspinatus tear. Adding acromioplasty significantly decreased the subacromial contact area compared with superior capsule reconstruction without acromioplasty (0° of abduction: 26% decrease [P = .01]; 30° of abduction: 21% decrease [P = .009]; 60° of abduction: 61% decrease [P = .003]) and did not alter humeral head position, superior translation, or subacromial peak contact pressure.


CONCLUSIONS
Superior capsule reconstruction repositioned the superiorly migrated humeral head and restored superior stability in the shoulder joint. Adding acromioplasty decreased the subacromial contact area without increasing the subacromial contact pressure.


CONCLUSIONS
When superior capsule reconstruction is performed for irreparable rotator cuff tears, acromioplasty may help to decrease the postoperative risk of abrasion and tearing of the graft beneath the acromion.
Orthopaedic Biomechanics Laboratory, Veterans Affairs Long Beach Healthcare System and University of California, Irvine, Irvine, California, USA Department of Orthopedic Surgery, Osaka Medical College, Takatsuki, Japan Katsuragi Hospital, Kishiwada, Japan tmihata@poh.osaka-med.ac.jp.
Teruhisa
T
Mihata
Orthopaedic Biomechanics Laboratory, Veterans Affairs Long Beach Healthcare System and University of California, Irvine, Irvine, California, USA.
Michelle H
MH
McGarry
Orthopaedic Biomechanics Laboratory, Veterans Affairs Long Beach Healthcare System and University of California, Irvine, Irvine, California, USA.
Timothy
T
Kahn
Orthopaedic Biomechanics Laboratory, Veterans Affairs Long Beach Healthcare System and University of California, Irvine, Irvine, California, USA.
Iliya
I
Goldberg
Department of Orthopedic Surgery, Osaka Medical College, Takatsuki, Japan.
Masashi
M
Neo
Orthopaedic Biomechanics Laboratory, Veterans Affairs Long Beach Healthcare System and University of California, Irvine, Irvine, California, USA.
Thay Q
TQ
Lee
D000174:Acromion / Q000502:physiology / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D001178:Arthroplasty / Q000379:methods; D001696:Biomechanical Phenomena; D002102:Cadaver; D016022:Case-Control Studies; D005206:Fascia Lata / Q000502:physiology; D005260:Female; D006801:Humans; D058430:Humeral Head / Q000293:injuries; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery; D022125:Lacerations / Q000601:surgery; D008023:Ligaments, Articular / Q000502:physiology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011312:Pressure; D016059:Range of Motion, Articular / Q000502:physiology*; D017006:Rotator Cuff / Q000502:physiology; D000070636:Rotator Cuff Injuries; D012421:Rupture / Q000503:physiopathology / Q000601:surgery; D012540:Scapula / Q000502:physiology / Q000601:surgery; D019534:Shoulder Impingement Syndrome / Q000503:physiopathology / Q000601:surgery; D012785:Shoulder Joint / Q000601:surgery*; D013708:Tendon Injuries / Q000601:surgery*; D013710:Tendons / Q000502:physiology / Q000601:surgery; D019737:Transplants
acromioplasty; capsule; defect; shoulder; stability; superior