title: Effect of diet-induced vitamin D deficiency on rotator cuff healing in a rat model.
abstract: BACKGROUND
  Few studies have considered hormonal influences, particularly vitamin D, on healing.
  
  
  OBJECTIVE
  Vitamin D deficiency would have a negative effect on the structure of the healing tendon-bone interface in a rat model and would result in decreased tendon attachment strength.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Vitamin D deficiency was induced in 28 male Sprague-Dawley rats using a specialized vitamin D-deficient diet and ultraviolet light restriction. Serum levels of vitamin D were measured after 6 weeks. These vitamin D-deficient animals (experimental group) plus 32 rats with normal vitamin D levels (controls) underwent unilateral detachment of the right supraspinatus tendon from the greater tuberosity of the humerus, followed by immediate repair using bone tunnel suture fixation. The animals were sacrificed at 2- and 4-week intervals after surgery for biomechanical analysis. A paired t test was used to compare serum vitamin D levels at day 0 and at 6 weeks. A nonparametric Mann-Whitney U test was used to compare load-to-failure and stiffness values between the experimental group and controls. Bone density and new bone formation at the tendon insertion site on the greater tuberosity were assessed with micro-computed tomography (CT). The organization of collagen tissue, new bone formation, vascularity at the tendon-bone interface, fibrocartilage at the tendon-bone interface, and collagen fiber continuity between the tendon and bone tissue were evaluated with safranin O and picrosirius red staining.
  
  
  RESULTS
  Blood draws confirmed vitamin D deficiency at 6 weeks compared with time zero/baseline for rats in the experimental group (10.9 ng/mL vs 6.5 ng/mL, respectively; P < .001). Biomechanical testing demonstrated a significant decrease in load to failure in the experimental group compared with controls at 2 weeks (5.8 ± 2.0 N vs 10.5 ± 4.4 N, respectively; P < .006). There was no difference in stiffness at 2 weeks between the control and experimental groups. At 4 weeks, there was no significant difference in load to failure or stiffness between the control and experimental groups. Histological analysis showed less bone formation and less collagen fiber organization in the vitamin D-deficient specimens at 4 weeks as compared with controls. Micro-CT analysis showed no significant difference between groups for total mineral density and bone volume fraction of cortical, whole, or trabecular bone at 4 weeks.
  
  
  CONCLUSIONS
  The biomechanical and histological data from this study suggest that low vitamin D levels may negatively affect early healing at the rotator cuff repair site.
  
  
  CONCLUSIONS
  It is estimated that 1 billion people worldwide are vitamin D deficient. In the deficient state, acutely injured rotator cuffs may have a reduced ability for tendon healing. Further studies are needed to determine the exact mechanism by which vitamin D affects tendon healing and whether vitamin D supplementation can improve rotator cuff tendon healing and reduce the incidence of retears.
authors.affiliation: Scott A. Rodeo, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021. rodeos@hss.edu.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Angeline
authors.forename: Richard
authors.initials: R
authors.lastname: Ma
authors.forename: Cecilia
authors.initials: C
authors.lastname: Pascual-Garrido
authors.forename: Clifford
authors.initials: C
authors.lastname: Voigt
authors.forename: Xiang Hua
authors.initials: XH
authors.lastname: Deng
authors.forename: Russell F
authors.initials: RF
authors.lastname: Warren
authors.forename: Scott A
authors.initials: SA
authors.lastname: Rodeo
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D004032:Diet; D007124:Immunoenzyme Techniques; D008297:Male; D010012:Osteogenesis / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017006:Rotator Cuff / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D014808:Vitamin D Deficiency / Q000503:physiopathology*; D014945:Wound Healing / Q000502:physiology*; D055114:X-Ray Microtomography
keywords: biological augmentation; rotator cuff; tendon-to-bone healing; vitamin D