title: Assessment of glenoid chondral healing: comparison of microfracture to autologous matrix-induced chondrogenesis in a novel rabbit shoulder model.
abstract: BACKGROUND
  Management of glenohumeral arthrosis in young patients is a considerable challenge, with a growing need for non-arthroplasty alternatives. The objectives of this study were to develop an animal model to study glenoid cartilage repair and to compare surgical repair strategies to promote glenoid chondral healing.
  
  
  METHODS
  Forty-five rabbits underwent unilateral removal of the entire glenoid articular surface and were divided into 3 groups--untreated defect (UD), microfracture (MFx), and MFx plus type I/III collagen scaffold (autologous matrix-induced chondrogenesis [AMIC])--for the evaluation of healing at 8 weeks (12 rabbits) and 32 weeks (33 rabbits) after injury. Contralateral shoulders served as unoperated controls. Tissue assessments included 11.7-T magnetic resonance imaging (long-term healing group only), equilibrium partitioning of an ionic contrast agent via micro-computed tomography (EPIC-μCT), and histologic investigation (grades on International Cartilage Repair Society II scoring system).
  
  
  RESULTS
  At 8 weeks, x-ray attenuation, thickness, and volume did not differ by treatment group. At 32 weeks, the T2 index (ratio of T2 values of healing to intact glenoids) was significantly lower for the MFx group relative to the AMIC group (P = .01) whereas the T1ρ index was significantly lower for AMIC relative to MFx (P = .01). The micro-computed tomography-derived repair tissue volume was significantly higher for MFx than for UD. Histologic investigation generally suggested inferior healing in the AMIC and UD groups relative to the MFx group, which exhibited improvements in both integration of repair tissue with subchondral bone and tidemark formation over time.
  
  
  CONCLUSIONS
  Improvements conferred by AMIC were limited to magnetic resonance imaging outcomes, whereas MFx appeared to promote increased fibrous tissue deposition via micro-computed tomography and more hyaline-like repair histologically. The findings from this novel model suggest that MFx promotes biologic resurfacing of full-thickness glenoid articular injury.
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Wang
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Vasili
authors.initials: V
authors.lastname: Karas
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Andrew S
authors.initials: AS
authors.lastname: Lee
authors.affiliation: Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Ziying
authors.initials: Z
authors.lastname: Yin
authors.affiliation: Rockford Orthopedic Associates, Rockford, IL, USA.
authors.forename: Geoffrey S
authors.initials: GS
authors.lastname: Van Thiel
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Kristen
authors.initials: K
authors.lastname: Hussey
authors.affiliation: Department of Anatomy and Cell Biology, Rush University Medical Center, Chicago, IL, USA.
authors.forename: D Rick
authors.initials: DR
authors.lastname: Sumner
authors.affiliation: Department of Biochemistry, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Susan
authors.initials: S
authors.lastname: Chubinskaya
authors.affiliation: Department of Bioengineering, University of Illinois at Chicago, Chicago, IL, USA.
authors.forename: Richard L
authors.initials: RL
authors.lastname: Magin
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Nikhil N
authors.initials: NN
authors.lastname: Verma
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Romeo
authors.affiliation: Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA. Electronic address: bcole@rushortho.com.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Cole
mesh_terms: D000818:Animals; D054544:Arthroplasty, Subchondral; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D020219:Chondrogenesis; D024042:Collagen Type I / Q000008:administration & dosage; D024061:Collagen Type III / Q000008:administration & dosage; D021621:Imaging, Three-Dimensional; D023421:Models, Animal; D011817:Rabbits; D012782:Shoulder / Q000601:surgery*; D054457:Tissue Scaffolds; D014945:Wound Healing; D055114:X-Ray Microtomography
chemical_list: D024042:Collagen Type I; D024061:Collagen Type III
keywords: Glenohumeral; animal model; articular cartilage; autologous matrix-induced chondrogenesis; microfracture