title: Collagen fibre and fibril ultrastructural arrangement of the superficial medial collateral ligament in the human knee.
abstract: OBJECTIVE
  The aim of the study was to investigate the collagen fibre ultrastructural arrangement and collagen fibril diameters in the superficial medial collateral ligament (sMCL) in the human knee. Considering sMCL's distinctive functions at different angles of knee flexion, it was hypothesized a significant difference between the collagen fibril diameters of each portion of the sMCL.
  
  
  METHODS
  Fourteen sMCL from seven fresh males (by chance because of the availability) cadavers (median age 40 years, range 34-59 years) were harvested within 12 h of death. sMCLs were separated into two orders of regions for analysis. The first order (divisions) was anterior, central and posterior. Thereafter, each division was split into three regions (femoral, intermediate and tibial), generating nine portions. One sMCL from each cadaver was used for transmission electron microscopy (TEM) and morphometric analyses, whereas the contralateral sMCL was processed for light microscopy (LM) or scanning electron microscopy (SEM).
  
  
  RESULTS
  LM and SEM analyses showed a complex tridimensional architecture, with the presence of wavy collagen fibres or crimps. TEM analysis showed significant differences in median collagen fibril diameter among portions inside the anterior, central and posterior division of the sMCL (p < 0.0001 within each division). Significant differences were also present among the median [interquartile range] collagen fibril diameters of anterior (39.4 [47.8-32.9]), central (38.5 [44.4-34.0]) and posterior (41.7 [52.2-35.4]) division (p = 0.0001); femoral (38.2 [45.0-32.7]), intermediate (40.3 [47.3-36.1]) and tibial (40.7 [55.0-32.2]) region (p = 0.0001).
  
  
  CONCLUSIONS
  Human sMCL showed a complex architecture that allows restraining different knee motions at different angles of knee flexion. The posterior division of sMCL accounted for the largest median collagen fibril diameter. The femoral region of sMCL accounted for the smallest median collagen fibril diameter. The presence of crimps in the medial collateral ligament, previously identified in the rat, was confirmed in humans (taking into consideration differences between these two species).
authors.affiliation: Istituto Ortopedico Rizzoli, Bologna, Italy. s.zaffagnini@biomec.ior.it.
authors.forename: Stefano
authors.initials: S
authors.lastname: Zaffagnini
authors.affiliation: Istituto Ortopedico Rizzoli, Bologna, Italy. marcheggianimuccioli@me.com.
authors.forename: Giulio Maria
authors.initials: GM
authors.lastname: Marcheggiani Muccioli
authors.affiliation: Faculty of Sport Sciences, University of Bologna, Bologna, Italy. marco.franchi3@unibo.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Franchi
authors.affiliation: Institute of Human Anatomy, University of Bologna, Bologna, Italy. beatrice.bacchelli@unibo.it.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Bacchelli
authors.affiliation: Istituto Ortopedico Rizzoli, Bologna, Italy. alberto.grassi@ior.it.
authors.forename: Alberto
authors.initials: A
authors.lastname: Grassi
authors.affiliation: Statistical Science Department, University of Bologna, Bologna, Italy. patrizia.agati@unibo.it.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Agati
authors.affiliation: Institute of Human Anatomy, University of Bologna, Bologna, Italy. marilisa.quaranta@unibo.it.
authors.forename: Marilisa
authors.initials: M
authors.lastname: Quaranta
authors.affiliation: Istituto Ortopedico Rizzoli, Bologna, Italy. m.marcacci@biomec.it.
authors.forename: Maurilio
authors.initials: M
authors.lastname: Marcacci
authors.affiliation: Institute of Human Anatomy, University of Bologna, Bologna, Italy. viviana.depasquale@unibo.it.
authors.forename: Viviana
authors.initials: V
authors.lastname: De Pasquale
mesh_terms: D000328:Adult; D000818:Animals; D002102:Cadaver; D003094:Collagen / Q000032:analysis / Q000648:ultrastructure*; D024022:Fibrillar Collagens / Q000648:ultrastructure*; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology / Q000648:ultrastructure*; D008297:Male; D017888:Medial Collateral Ligament, Knee / Q000033:anatomy & histology / Q000648:ultrastructure*; D008853:Microscopy; D017348:Microscopy, Electron, Scanning Transmission; D046529:Microscopy, Electron, Transmission; D008875:Middle Aged; D051381:Rats
chemical_list: D024022:Fibrillar Collagens; D003094:Collagen
keywords: Collagen fibre array; Crimps; Human; Knee; Medial collateral ligament; Ultrastructure