Neoligamentization process of BTPB used for ACL graft: histological evaluation from 6 months to 10 years

Knee. 2007 Mar;14(2):87-93. doi: 10.1016/j.knee.2006.11.006. Epub 2006 Dec 26.


Following anterior cruciate ligament (ACL) reconstruction with the middle third part patellar tendon, the graft undergoes histological rearrangement due to biomechanical action, which transforms it into a structure similar to the normal ACL. The purpose of our study was to make a qualitative and quantitative histological evaluation, by transmission electron microscopy (TEM), of the neoligamentization process of a bone-patellar tendon-bone (BTPB) graft used as pro-ACL at different follow-up times. We analysed the ultrastructure of collagen fibrils by focusing on their size and distribution with respect to a normal patellar tendon and a normal ACL used as controls. Our results showed that up to 24 months follow-up, progressive ultrastructural changes towards the normal ACL were observed. At longer times after surgery (48 and 120 months) no further changes were evident and the ultrastructure showed a marked reduction in large fibrils, which was typical of the control patellar tendon, and a significant increase in small fibrils. The ultrastructure seemed to combine fibrils from two different morphological units. The BPTB graft used as ACL underwent a transformation process for up to two years. After that period the transformation ceased and for ten years failed to reach the ultrastructural aspect of a normal ACL. However, from an architectural point of view the graft was slowly transformed into a structure similar to ACL with respect to the different mechanical stresses the ligament has to sustain.

MeSH terms

  • Adolescent
  • Adult
  • Anterior Cruciate Ligament / surgery*
  • Anterior Cruciate Ligament Injuries
  • Bone-Patellar Tendon-Bone Grafting / pathology*
  • Case-Control Studies
  • Collagen / ultrastructure
  • Elastic Tissue / ultrastructure
  • Elastin / ultrastructure
  • Extracellular Matrix Proteins / ultrastructure
  • Follow-Up Studies
  • Humans
  • Male
  • Microscopy, Electron, Transmission
  • Patellar Ligament / ultrastructure*


  • Extracellular Matrix Proteins
  • oxytalan
  • Collagen
  • Elastin