title: Delayed early passive motion is harmless to shoulder rotator cuff healing in a rabbit model.
abstract: BACKGROUND
  Postoperative passive motion is the most widely accepted rehabilitation protocol after rotator cuff repair; however, a rotator cuff retear remains a frequent surgical complication. Clinical outcomes indicate that early passive motion is harmless to rotator cuff healing, but no laboratory evidence supports this proposition.
  
  
  OBJECTIVE
  (1) Immediate postoperative immobilization improves rotator cuff healing in rabbits. (2) Early passive motion after short-term immobilization does not harm rotator cuff healing in rabbits.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  An injury to the supraspinatus tendon was created and repaired in 90 New Zealand White rabbits, after which they were randomly separated into 3 groups: (1) nonimmobilization (NI; n = 30), (2) continuous immobilization (IM; n = 30), and (3) immobilization with early passive motion (IP; n = 30). At 3, 6, and 12 weeks postoperatively, 5 rabbits from each group were sacrificed for histological evaluation, biomechanical testing, and magnetic resonance imaging.
  
  
  RESULTS
  The histological study demonstrated better postoperative healing in the IM and IP groups, with clusters of chondrocytes accumulated at the tendon-bone junction. Magnetic resonance imaging illustrated that the tendon-bone junction was intact in the IM and IP groups. The magnetic resonance quantification analysis showed that the signal-to-noise quotient (SNQ) of the NI group was not significantly higher than that of the immobilization groups at 3 weeks (P = .232) or 6 weeks (P = .117), but it was significantly different at 12 weeks (NI vs IM, P = .006; NI vs IP, P = .009). At 12 weeks, the failure load was significantly higher in the IM and IP groups than in the NI group (NI vs IM, P = .002; NI vs IP, P = .002), but no difference was found between the IM and IP groups (P = .599).
  
  
  CONCLUSIONS
  Immediate postoperative immobilization led to better tendon-bone healing than immediate postoperative mobilization, and under immobilization, early passive motion was harmless to tendon-bone healing in this study.
  
  
  CONCLUSIONS
  The results have an implication in supporting the rehabilitation protocol of early passive motion after rotator cuff repair.
authors.affiliation: Department of Sports Medicine, Huashan Hospital, Fudan University, No. 12, Wulumuqi Zhong Road, Shanghai 200040, China.
authors.forename: Shurong
authors.initials: S
authors.lastname: Zhang
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Hongyue
authors.initials: H
authors.lastname: Tao
authors.forename: Hongyun
authors.initials: H
authors.lastname: Li
authors.forename: Samson
authors.initials: S
authors.lastname: Cho
authors.forename: Yinghui
authors.initials: Y
authors.lastname: Hua
authors.forename: Jiwu
authors.initials: J
authors.lastname: Chen
authors.forename: Shiyi
authors.initials: S
authors.lastname: Chen
authors.forename: Yunxia
authors.initials: Y
authors.lastname: Li
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005081:Exercise Therapy / Q000379:methods*; D008279:Magnetic Resonance Imaging; D008297:Male; D011182:Postoperative Care / Q000379:methods*; D011817:Rabbits; D011897:Random Allocation; D012149:Restraint, Physical; D017006:Rotator Cuff / Q000473:pathology / Q000502:physiology / Q000601:surgery*; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000534:rehabilitation / Q000601:surgery*; D053656:Tenodesis / Q000534:rehabilitation*; D016896:Treatment Outcome; D014945:Wound Healing
keywords: biomechanical testing; magnetic resonance imaging; passive motion; rotator cuff healing; signal intensity