title: Medial Femoral Condyle Cartilage Defect Biomechanics: Effect of Obesity, Defect Size, and Cartilage Thickness.
abstract: BACKGROUND
  Medial femoral condyle (MFC) chondral defects cause knee pain. Clinical studies have shown worse functional outcomes and cartilage defect fill rates after microfracture in obese patients (BMI ≥30) and for defects with size ≥2 cm(2).
  
  
  OBJECTIVE
  To determine the effect of obesity, defect size, and cartilage thickness on the force sustained at the base of full-thickness MFC cartilage defects during weightbearing.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Eight human cadaveric knees were loaded in 15° of flexion. A sensor measured force across the medial compartment. The area at the base of the defect protected from load, termed the "area of containment," was quantified, and loads simulating weightbearing for BMIs of 20, 30, and 40 were applied. A full-thickness cartilage defect was created on the MFC. Cycles of loads were applied for defect sizes with diameters of 6, 8, 10, 12, 14, 16, 18, and 20 mm. A second sensor recorded force at the base of the defect for defects with diameters of 14, 16, 18, and 20 mm.
  
  
  RESULTS
  Loads simulating BMI ≥30 led to a decrease in the area of containment for all defects ≥14 mm in diameter (P ≤ .038). Base of defect force increased for defects ≥16 mm in diameter (area, ≥2 cm(2)) between loaded and unloaded states (P ≤ .042) and for loads simulating BMI ≥30 (P ≤ .045). Cartilage rim thickness <2 mm showed higher base of defect force than did thickness ≥2 mm, for all BMI groups (P ≤ .025).
  
  
  CONCLUSIONS
  Increased force at the base of MFC cartilage defects was observed for weightbearing loads simulating BMI ≥30, for defect size ≥2 cm(2), and for rim thickness <2 mm. This may lead to a biomechanically unfavorable environment after microfracture in these patient subsets.
  
  
  CONCLUSIONS
  These biomechanical findings corroborate clinical studies that have noted worse outcomes after microfracture in patients with BMI ≥30 and cartilage defects of size ≥2 cm(2). Further clinical studies are needed to compare microfracture with other cartilage restoration procedures in these patient subsets.
authors.affiliation: DMC Sports Medicine, Detroit Medical Center, Detroit, Michigan, USA kylelacymd@gmail.com.
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Lacy
authors.affiliation: DMC Sports Medicine, Detroit Medical Center, Detroit, Michigan, USA.
authors.forename: Allison
authors.initials: A
authors.lastname: Cracchiolo
authors.affiliation: DMC Sports Medicine, Detroit Medical Center, Detroit, Michigan, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Yu
authors.affiliation: DMC Sports Medicine, Detroit Medical Center, Detroit, Michigan, USA.
authors.forename: Henry
authors.initials: H
authors.lastname: Goitz
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D002357:Cartilage Diseases / Q000209:etiology / Q000473:pathology / Q000503:physiopathology*; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005269:Femur / Q000502:physiology; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications* / Q000503:physiopathology; D016059:Range of Motion, Articular / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology
keywords: medial femoral condyle; microfracture; osteochondral defects