title: The influence of compression on the healing of experimental tibial fractures.
abstract: OBJECTIVE
  Experimental studies of the effects of various mechanical conditions and stimuli on bone healing have disclosed an improvement potential in bone fracture mineralization and biomechanical properties. We therefore evaluated the effect of a clinically practicable application of a mechanical compressive interfragmentary stimulus on the healing of experimental tibial diaphyseal fractures.
  
  
  METHODS
  Sixty Male rats received a standardized tibial shaft osteotomy stabilized with a unilateral external fixator with a zero interfragmentary distance, and then randomly assigned to the compression (N=20), control (N=20) or distraction (N=20) group. From days 4 to day 14, the external fixator was either tightened (compression group) or loosened (distraction group) once daily to gradually induce a total axial displacement of the external fixator pin clamps of 1.25 mm. Evaluation at 30 and 60 days post-osteotomy included radiography, dual-energy X-ray absorptiometry (DXA), quantitative CT and mechanical testing.
  
  
  RESULTS
  All fractures healed radiographically with sparse callus. At 60 days, the compression and control groups exhibited significantly less amount of mineralized callus in terms of DXA measured callus area and bone mineral content (BMC) compared to the distraction group. These groups also demonstrated a smaller volume of low-mineralized bone tissue (callus) and a larger volume of highly mineralized bone tissue (cortical bone) measured by QCT than in the distraction group. Both mechanical strength and stiffness was significantly higher in the compression and control groups than in the distraction group at 60 days.
  
  
  CONCLUSIONS
  Compression did not enhance fracture healing in terms of mineralization, bending strength, or stiffness at the time of union, compared with the control condition. The compression and control groups exhibited improved healing in terms of mechanical strength and stiffness and a more mature callus mineralization compared with the distraction group.
authors.affiliation: Department of Orthopaedic Surgery, University of Oslo, Oslo, Norway. u.e.w.sigurdsen@medisin.uio.no
authors.forename: Ulf
authors.initials: U
authors.lastname: Sigurdsen
authors.forename: Olav
authors.initials: O
authors.lastname: Reikeras
authors.forename: Stein Erik
authors.initials: SE
authors.lastname: Utvag
mesh_terms: D015502:Absorptiometry, Photon; D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D002146:Bony Callus / Q000000981:diagnostic imaging; D018483:Diaphyses / Q000000981:diagnostic imaging; D004195:Disease Models, Animal; D016267:External Fixators; D005592:Fracture Fixation / Q000379:methods*; D017102:Fracture Healing / Q000502:physiology*; D008297:Male; D019857:Osteogenesis, Distraction; D010027:Osteotomy; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D013978:Tibial Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D013997:Time Factors; D055114:X-Ray Microtomography