title: A comparative study of bone to bone repair and bone to tendon healing in patella-patellar tendon complex in rabbits.
abstract: OBJECTIVE
  To study the healing quality of bone to bone and bone to tendon repair in a patella-patellar tendon complex.
  
  
  METHODS
  In vivo animal experiment in 60 mature 32-week-old female rabbits.
  
  
  BACKGROUND
  Injuries of patella-patellar tendon complex are not uncommon. However, no studies are available to compare the healing quality between bone to bone and bone to tendon surgical reconstructions used for repair of patella-patellar tendon complex.
  
  
  METHODS
  A standard transverse osteotomy was performed at the distal one-third of patella of one hindlimb. Both patellar fragments were reattached for bone to bone group while the patellar tendon was reattached to the remaining patella after removing the distal one-third of patella for bone to tendon group. Patella-patellar tendon complex was harvested at 8, 12 and 24 weeks postoperatively for biomechanical and histological evaluations, with n=8 and n=2 at each healing time points in both groups. The contralateral knee served as a control.
  
  
  RESULTS
  No significant differences in the failure loads were found between two groups. However, greater ultimate stress was found in bone to bone group as compared with bone to tendon group at week 8 and 24 (both P<0.05). On average, the ultimate stress of the bone to tendon and bone to bone group only reached 20.6(4.2)% and 28.6(6.7)% of the control values at week 24, respectively. The discrepancy between findings in failure load and failure stress might be explained by an overall larger cross-sectional area of the healing interface in bone to tendon group as compared with bone to bone group. Histology revealed that the bone to bone healing was via endochondral ossification at the healing interface. In bone to tendon group, extensive scar tissue was formed to overbridge the healing interface and remodeled with healing over time. The structural integration at the tendon and bony healing interface was poor and no typical intermitted fibrocartilage zone as seen in normal bone to tendon junction was formed.
  
  
  CONCLUSIONS
  Failure load of bone to bone and bone to tendon healing interface did not differ during repair of patella-patellar tendon complex. However, the healing interface of bone to bone repair in terms of material properties as reflected by failure stress was superior to that of the bone to tendon healing.
  
  
  CONCLUSIONS
  The findings of this experimental study may suggest that the anatomical reconstruction of patella-patellar tendon complex injury may be the primary concern in decision making for selecting either bone to bone or bone to tendon repair. However whenever possible, to initial fracture (bone-to-bone) fixation for ensuring better and predictable repair at the healing interface.
authors.affiliation: Musculo-Skeletal Research Laboratory, Department of Orthopaedics & Traumatology, The Chinese University of Hong Kong, Clinical Sciences Building, Prince of Wales Hospital, Shatin, N.T., Hong Kong.
authors.forename: Kwok Sui
authors.initials: KS
authors.lastname: Leung
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Lap Kun
authors.initials: LK
authors.lastname: Fu
authors.forename: Chun Wai
authors.initials: CW
authors.lastname: Chan
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D016723:Bone Remodeling; D005260:Female; D017847:Patellar Ligament / Q000601:surgery*; D011817:Rabbits; D013314:Stress, Mechanical; D013710:Tendons / Q000601:surgery*; D014945:Wound Healing / Q000502:physiology*