title: Small subchondral drill holes improve marrow stimulation of articular cartilage defects.
abstract: BACKGROUND
  Subchondral drilling is an established marrow stimulation technique.
  
  
  OBJECTIVE
  Osteochondral repair is improved when the subchondral bone is perforated with small drill holes, reflecting the physiological subchondral trabecular distance.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  A rectangular full-thickness chondral defect was created in the trochlea of adult sheep (n = 13) and treated with 6 subchondral drillings of either 1.0 mm (reflective of the trabecular distance) or 1.8 mm in diameter. Osteochondral repair was assessed after 6 months in vivo by macroscopic, histological, and immunohistochemical analyses and by micro-computed tomography.
  
  
  RESULTS
  The application of 1.0-mm subchondral drill holes led to significantly improved histological matrix staining, cellular morphological characteristics, subchondral bone reconstitution, and average total histological score as well as significantly higher immunoreactivity to type II collagen and reduced immunoreactivity to type I collagen in the repair tissue compared with 1.8-mm drill holes. Analysis of osteoarthritic changes in the cartilage adjacent to the defects revealed no significant differences between treatment groups. Restoration of the microstructure of the subchondral bone plate below the chondral defects was significantly improved after 1.0-mm compared to 1.8-mm drilling, as shown by higher bone volume and reduced thickening of the subchondral bone plate. Likewise, the microarchitecture of the drilled subarticular spongiosa was better restored after 1.0-mm drilling, indicated by significantly higher bone volume and more and thinner trabeculae. Moreover, the bone mineral density of the subchondral bone in 1.0-mm drill holes was similar to the adjacent subchondral bone, whereas it was significantly reduced in 1.8-mm drill holes. No significant correlations existed between cartilage and subchondral bone repair.
  
  
  CONCLUSIONS
  Small subchondral drill holes that reflect the physiological trabecular distance improve osteochondral repair in a translational model more effectively than larger drill holes.
  
  
  CONCLUSIONS
  These results have important implications for the use of subchondral drilling for marrow stimulation, as they support the use of small-diameter bone-cutting devices.
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany.
authors.forename: Mona
authors.initials: M
authors.lastname: Eldracher
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany Department of Orthopaedic Surgery, Saarland University Medical Center, Homburg, Germany Cartilage Net of the Greater Region (Germany, France, Belgium, Luxembourg).
authors.forename: Patrick
authors.initials: P
authors.lastname: Orth
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany Cartilage Net of the Greater Region (Germany, France, Belgium, Luxembourg).
authors.forename: Magali
authors.initials: M
authors.lastname: Cucchiarini
authors.affiliation: Cartilage Net of the Greater Region (Germany, France, Belgium, Luxembourg) Olympic Medical Center, Centre Hospitalier de Luxembourg, Clinique d'Eich, Luxembourg, Luxembourg.
authors.forename: Dietrich
authors.initials: D
authors.lastname: Pape
authors.affiliation: Center of Experimental Orthopaedics, Saarland University, Homburg, Germany Department of Orthopaedic Surgery, Saarland University Medical Center, Homburg, Germany Cartilage Net of the Greater Region (Germany, France, Belgium, Luxembourg) henning.madry@uks.eu.
authors.forename: Henning
authors.initials: H
authors.lastname: Madry
mesh_terms: D000818:Animals; D054544:Arthroplasty, Subchondral / Q000009:adverse effects / Q000379:methods*; D001853:Bone Marrow / Q000502:physiology*; D002358:Cartilage, Articular / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D024042:Collagen Type I / Q000032:analysis; D024043:Collagen Type II / Q000032:analysis; D004838:Epiphyses / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D005260:Female; D007718:Knee Injuries / Q000601:surgery; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D054850:Osteophyte / Q000209:etiology; D012756:Sheep; D014945:Wound Healing; D055114:X-Ray Microtomography
chemical_list: D024042:Collagen Type I; D024043:Collagen Type II
keywords: articular cartilage repair; marrow stimulation; micro-CT; sheep; subchondral bone; subchondral drilling