title: The efficacy of intra-articular hyaluronan injection after the microfracture technique for the treatment of articular cartilage lesions.
abstract: BACKGROUND
  Although the exact mechanism of action has yet to be elucidated, recent animal studies have demonstrated chondroprotective and anti-inflammatory properties of hyaluronic acid viscosupplementation.
  
  
  OBJECTIVE
  Intra-articular hyaluronic acid after microfracture improves the quality of the repair leading to a more hyaline-like repair tissue with better defect fill and adjacent area integration.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Full-thickness cartilage defects were created in the weightbearing area of the medial femoral condyle in 36 female New Zealand White rabbits. The defects were then treated with surgical microfracture. Eighteen rabbits formed the 3-month cohort and the other 18 formed the 6-month cohort. Within each cohort, 6 rabbits were randomly assigned to receive 3 weekly injections of hyaluronic acid (group A), 5 weekly injections (group B), or control injections of normal saline (group C). At 3 and 6 months postmicrofracture, the animals were sacrificed and the operative knee harvested. Repair tissue was assessed blinded- both grossly, using a modified component of the International Cartilage Repair Society (ICRS) Cartilage Repair Assessment scoring scale, and histologically, using the modified O'Driscoll histological cartilage scoring system. Comparisons were made with respect to gross and histologic findings between treatment groups at each time point. Effects of each treatment type were also evaluated longitudinally by comparing the 3-month results with the 6-month results. Statistical analysis was performed using unpaired Student t tests with significance defined as P < .05.
  
  
  RESULTS
  At 3 months, gross and histologic evaluation of the repair tissue demonstrated that the 3-injection group had significantly better fill of the defects and more normal appearing, hyaline-like tissue than controls (a mean ICRS score of 1.92 vs 1.26; P < .05 and a mean modified O'Driscoll score of 10.3 vs 7.6; P < .02). Specimens treated with 5 weekly injections were not significantly improved compared with controls. At 6 months, the mean gross appearance and histologic scores between the 3 specimen cohorts were not significantly different. However, examination of the entire operative knee demonstrated a significantly greater extent of degenerative changes (synovial inflammation and osteophyte formation) in the control group than in both hyaluronic acid treatment groups (P < .05).
  
  
  CONCLUSIONS
  Supplementing the microfracture technique with 3 weekly injections of intra-articular hyaluronic acid had a positive effect on the repair tissue that formed within the chondral defect at the early follow-up time point. This improvement was not found for the 3-injection group at 6 months or for the 5-injection group at either time point. Additionally, hyaluronic acid supplementation had a possible chondroprotective and anti-inflammatory effect, limiting the development of degenerative changes within the knee joint.
  
  
  CONCLUSIONS
  The adjunctive use of hyaluronic acid appears to hold promise in the treatment of chondral injuries and warrants further investigation.
authors.affiliation: Musculoskeletal Research Center, Department of Orthopaedic Surgery, NYU-Hospital for Joint Diseases, New York, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Strauss
authors.forename: Aaron
authors.initials: A
authors.lastname: Schachter
authors.forename: Sally
authors.initials: S
authors.lastname: Frenkel
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Rosen
mesh_terms: D000818:Animals; D054544:Arthroplasty, Subchondral; D002358:Cartilage, Articular / Q000293:injuries*; D005260:Female; D050724:Fractures, Cartilage / Q000628:therapy*; D006820:Hyaluronic Acid / Q000008:administration & dosage*; D007270:Injections, Intra-Articular; D010865:Pilot Projects; D011817:Rabbits; D055675:Viscosupplements / Q000008:administration & dosage*
chemical_list: D055675:Viscosupplements; D006820:Hyaluronic Acid