Effect of scapular dyskinesis on supraspinatus repair healing in a rat model.
BACKGROUND
Rotator cuff tears are common conditions that often require surgical repair to improve function and to relieve pain. Unfortunately, repair failure remains a common problem after rotator cuff repair surgery. Several factors may contribute to repair failure, including age, tear size, and time from injury. However, the mechanical mechanisms resulting in repair failure are not well understood, making clinical management difficult. Specifically, altered scapular motion (termed scapular dyskinesis) may be one important and modifiable factor contributing to the risk of repair failure. Therefore, the objective of this study was to determine the effect of scapular dyskinesis on supraspinatus tendon healing after repair.


METHODS
A rat model of scapular dyskinesis was used. Seventy adult male Sprague-Dawley rats (400-450 g) were randomized into 2 groups: nerve transection of the accessory and long thoracic nerves (SD) or sham nerve transection (Sham control). After this procedure, all rats underwent unilateral detachment and repair of the supraspinatus tendon. All rats were sacrificed at 2, 4, and 8 weeks after surgery. Shoulder function, passive joint mechanics, and tendon properties (mechanical, histologic, organizational, and compositional) were evaluated.


RESULTS
Scapular dyskinesis alters joint function and may lead to compromised supraspinatus tendon properties. Specifically, diminished mechanical properties, altered histology, and decreased tendon organization were observed for some parameters.


CONCLUSIONS
This study identifies scapular dyskinesis as one underlying mechanism leading to compromise of supraspinatus healing after repair. Identifying modifiable factors that lead to compromised tendon healing will help improve clinical outcomes after repair.
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA; Department of Biomedical Engineering, Columbia University, New York, NY, USA.
Katherine E
KE
Reuther
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Jennica J
JJ
Tucker
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA; Division of Nursing and Health Sciences, Neumann University, Aston, PA, USA.
Stephen J
SJ
Thomas
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Rameen P
RP
Vafa
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Stephen S
SS
Liu
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Joshua A
JA
Gordon
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Adam C
AC
Caro
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Sarah M
SM
Yannascoli
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
Andrew F
AF
Kuntz
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA. Electronic address: soslowsk@mail.med.upenn.edu.
Louis J
LJ
Soslowsky
D000818:Animals; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D020820:Dyskinesias / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D019637:Orthopedic Procedures / Q000379:methods*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017006:Rotator Cuff / Q000503:physiopathology; D000070636:Rotator Cuff Injuries; D012421:Rupture / Q000601:surgery; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery*; D013708:Tendon Injuries / Q000503:physiopathology / Q000601:surgery*; D013710:Tendons / Q000503:physiopathology / Q000601:surgery*; D014945:Wound Healing / Q000502:physiology
Scapular dyskinesis; animal model; rat; rotator cuff repair; shoulder; tendon