title: Rotator cuff healing after continuous subacromial bupivacaine infusion: an in vivo rabbit study.
abstract: BACKGROUND
  The objective of this study was to evaluate the effects of continuous subacromial bupivacaine infusion on supraspinatus muscle and rotator cuff tendon healing using gross, biomechanical, and histologic analyses.
  
  
  METHODS
  Thirty-three New Zealand White rabbits underwent unilateral supraspinatus transection and rotator cuff repair (RCR). Rabbits were assigned to 1 of 3 groups: (1) RCR only, (2) RCR with continuous saline infusion for 48 hours, or (3) RCR with continuous 0.25% bupivacaine with epinephrine (1:200,000) infusion for 48 hours. Rabbits were euthanized postoperatively at 2 weeks (for histologic assessment) or 8 weeks (for biomechanical and histologic assessment).
  
  
  RESULTS
  Tensile testing showed a significantly higher load to failure in intact tendons compared with repaired tendons (P < .01); however, no statistical differences were detected among RCR only, RCR saline, and RCR bupivacaine groups. Histologically, the enthesis of repaired tendons showed increased cellularity and disorganized collagen fibers compared with intact tendons, with no differences between treatment groups. Muscle histology demonstrated scattered degenerative muscle fibers at 2 weeks in RCR saline and RCR bupivacaine groups, but no degeneration was noted at 8 weeks.
  
  
  CONCLUSIONS
  The healing supraspinatus tendons exposed to bupivacaine infusion showed similar histologic and biomechanical characteristics compared with untreated and saline-infused RCR groups. Muscle histology showed fiber damage at 2 weeks for the saline and bupivacaine-treated groups, with no apparent disruption at 8 weeks, suggesting a recovery process. Therefore, subacromial bupivacaine infusion in this rabbit rotator cuff model does not appear to impair muscle or tendon after acute injury and repair.
authors: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL 60612, USA.
authors: Nicole A
authors: NA
authors: Friel
authors: Vincent M
authors: VM
authors: Wang
authors: Mark A
authors: MA
authors: Slabaugh
authors: FanChia
authors: F
authors: Wang
authors: Susan
authors: S
authors: Chubinskaya
authors: Brian J
authors: BJ
authors: Cole
mesh_terms: D000779:Anesthetics, Local / Q000494:pharmacology*; D000818:Animals; D002045:Bupivacaine / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000601:surgery; D011817:Rabbits; D017006:Rotator Cuff / Q000187:drug effects* / Q000473:pathology / Q000601:surgery; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine