title: Small-Diameter Awls Improve Articular Cartilage Repair After Microfracture Treatment in a Translational Animal Model.
abstract: BACKGROUND
  Microfracture is the most commonly applied arthroscopic marrow stimulation procedure.
  
  
  OBJECTIVE
  Articular cartilage repair is improved when the subchondral bone is perforated by small-diameter microfracture awls compared with larger awls.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Standardized rectangular (4 × 8 mm) full-thickness chondral defects (N = 24) were created in the medial femoral condyle of 16 adult sheep and debrided down to the subchondral bone plate. Three treatment groups (n = 8 defects each) were tested: 6 microfracture perforations using small-diameter awls (1.0 mm; group 1), large-diameter awls (1.2 mm; group 2), or without perforations (debridement control; group 3). Osteochondral repair was assessed at 6 months in vivo using established macroscopic, histological, immunohistochemical, biochemical, and micro-computed tomography analyses.
  
  
  RESULTS
  Compared with control defects, histological cartilage repair was always improved after both microfracture techniques (P < .023). Application of 1.0-mm microfracture awls led to a significantly improved histological overall repair tissue quality (7.02 ± 0.70 vs 9.03 ± 0.69; P = .008) and surface grading (1.05 ± 0.28 vs 2.10 ± 0.19; P = .001) compared with larger awls. The small-diameter awl decreased relative bone volume of the subarticular spongiosa (bone volume/tissue volume ratio: 23.81% ± 3.37% vs 30.58% ± 2.46%; P = .011). Subchondral bone cysts and intralesional osteophytes were frequently observed after either microfracture treatment. Macroscopic grading, DNA, proteoglycan, and type I and type II collagen contents as well as degenerative changes within the adjacent cartilage remained unaffected by the awl diameter.
  
  
  CONCLUSIONS
  Small-diameter microfracture awls improve articular cartilage repair in the translational sheep model more effectively than do larger awls.
  
  
  CONCLUSIONS
  These data support the use of small microfracture instruments for the surgical treatment of cartilage defects and warrant prolonged clinical investigations.
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany Department of Orthopaedic Surgery, Saarland University Medical Center, Homburg, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Orth
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Duffner
authors.affiliation: Departments of Anesthesia and Surgery, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: David
authors.initials: D
authors.lastname: Zurakowski
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany.
authors.forename: Magali
authors.initials: M
authors.lastname: Cucchiarini
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany Department of Orthopaedic Surgery, Saarland University Medical Center, Homburg, Germany henning.madry@uks.eu.
authors.forename: Henning
authors.initials: H
authors.lastname: Madry
mesh_terms: D000818:Animals; D054544:Arthroplasty, Subchondral / Q000295:instrumentation / Q000379:methods*; D001853:Bone Marrow / Q000601:surgery; D002357:Cartilage Diseases / Q000601:surgery*; D002358:Cartilage, Articular / Q000601:surgery*; D024043:Collagen Type II / Q000378:metabolism; D004195:Disease Models, Animal; D004838:Epiphyses / Q000601:surgery; D005260:Female; D005269:Femur / Q000601:surgery; D007719:Knee Joint / Q000601:surgery; D054850:Osteophyte / Q000601:surgery; D011509:Proteoglycans / Q000378:metabolism; D012756:Sheep; D014945:Wound Healing / Q000187:drug effects; D055114:X-Ray Microtomography
chemical_list: D024043:Collagen Type II; D011509:Proteoglycans
keywords: articular cartilage; marrow stimulation; microfracture; sheep; subchondral bone