title: Detrimental Effect of Repeated and Single Subacromial Corticosteroid Injections on the Intact and Injured Rotator Cuff: A Biomechanical and Imaging Study in Rats.
abstract: BACKGROUND
  The effect of corticosteroids on tendons is poorly understood, and current data are insufficient and conflicting.
  
  
  OBJECTIVE
  To evaluate the effects of corticosteroid injections on intact and injured rotator cuffs (RCs) through biomechanical and radiographic analyses in a rat model.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  A total of 70 rats were assigned to 7 groups. Uninjured rats (no tear) received either a single saline injection, a single methylprednisolone acetate (MTA) injection, or triple MTA injections. Injured rats (unilateral supraspinatus injury) received either a single saline injection, triple saline injections, a single MTA injection, or triple MTA injections (injections were subacromial; repeat injections were administered weekly). Rats were sacrificed 1 week after final injection. Shoulders were harvested and grossly inspected, and the supraspinatus tendon was evaluated biomechanically. Bone density at the tendon insertion site on the greater tuberosity was assessed by micro-computed tomography.
  
  
  RESULTS
  Intact RCs exposed to triple MTA injections had significantly decreased maximal load and stiffness compared with the control group (14.43 vs 21.25 N and 8.21 vs 16.6 N/mm, respectively; P < .05). Injured RCs exposed to steroid treatment had significantly lower maximal load (single saline: 10.91 N, single steroid: 8.43 N [P < .05]; triple control: 15.77 N, triple steroid: 11.65 N [P < .05]) compared with the control at 3 weeks. Greater tuberosity volume density and connectivity density were significantly lower in undamaged rats after triple MTA injection (P < .05).
  
  
  CONCLUSIONS
  The study results clearly showed that repeated doses of corticosteroids significantly weaken rat RC and negatively affect bone quality in addition to possibly causing deterioration of the osteotendinous junction. However, data retrieved from animals must be scrupulously analyzed before extrapolation to humans. As such, the potential benefits and harms of subacromial corticosteroid treatment must be considered before administration.
  
  
  CONCLUSIONS
  The potential benefit and detrimental effects of corticosteroid injection should be thoroughly considered before it is administered subacromially in patients with RC injuries.
authors.affiliation: Shoulder Unit, Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel.
authors.forename: Eran
authors.initials: E
authors.lastname: Maman
authors.affiliation: Shoulder Unit, Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel.
authors.forename: Chaim
authors.initials: C
authors.lastname: Yehuda
authors.affiliation: Shoulder Unit, Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel.
authors.forename: Tamir
authors.initials: T
authors.lastname: Pritsch
authors.affiliation: Shoulder Unit, Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Morag
authors.affiliation: Biomechanics Laboratory, School of Dental Medicine Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel.
authors.forename: Tamar
authors.initials: T
authors.lastname: Brosh
authors.affiliation: Shoulder Unit, Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Sharfman
authors.affiliation: Shoulder Unit, Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Tel Aviv University Sackler Faculty of Medicine, Tel Aviv, Israel dolkarto@gmail.com.
authors.forename: Oleg
authors.initials: O
authors.lastname: Dolkart
mesh_terms: D000305:Adrenal Cortex Hormones / Q000633:toxicity*; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D006801:Humans; D007270:Injections, Intra-Articular; D008297:Male; D008775:Methylprednisolone / Q000031:analogs & derivatives* / Q000633:toxicity; D000077555:Methylprednisolone Acetate; D017208:Rats, Wistar; D017006:Rotator Cuff / Q000000981:diagnostic imaging / Q000187:drug effects*; D000070636:Rotator Cuff Injuries; D012421:Rupture / Q000503:physiopathology; D055114:X-Ray Microtomography
chemical_list: D000305:Adrenal Cortex Hormones; D000077555:Methylprednisolone Acetate; D008775:Methylprednisolone
keywords: biomechanics; corticosteroids; greater tuberosity; rotator cuff