title: Low intensity pulsed ultrasound increases the matrix hardness of the healing tissues at bone-tendon insertion-a partial patellectomy model in rabbits.
abstract: BACKGROUND
  This study evaluated the low intensity pulsed ultrasound enhancement on matrix hardness of the healing tissues at the bone-tendon junction.
  
  
  METHODS
  Sixteen 18 week-old mature female rabbits were used. An established transverse partial patellectomy was performed at the distal one-third of the patella. Animals were then divided according to their body weight into ultrasound group (n = 8) with daily treatment of low intensity pulsed ultrasound and control group (n = 8) without ultrasound treatment. Animals were euthanized at week 8 and 16 postoperatively to evaluate the radiographic new bone formation and the Vickers hardness of the matrix of the healing tissues at the bone-tendon junction.
  
  
  RESULTS
  (1) Comparing with the control group, the anterior-posterior area of the new bone in the ultrasound treated group was found on average to be 3.0 and 3.1 times greater at week 8 and 16, respectively (P < 0.01). (2) The Vickers hardness of the new bone in ultrasound group was 11.3% (P < 0.05) significantly lower at week 8 but 20.0% (P < 0.05) significantly higher at week 16 as compared with that of the control group. (3) The Vickers hardness of the newly regenerated fibrocartilage zone, healing tendon, and cartilaginous metaplasia in ultrasound group was found higher than the control group at both week 8 and 16, but the difference was significant at week 16 only, being 44.1% (P < 0.05), 20.1% (P < 0.01), and 46.4% (P < 0.01) higher, respectively.
  
  
  CONCLUSIONS
  The preliminary findings suggested for the first time that low intensity pulsed ultrasound treatment resulted in the enhancement of the matrix hardness in new bone, fibrocartilage, cartilaginous metaplasia, and healing tendon at the healing bone-tendon junction. These findings can be extrapolated into clinical practice, i.e. the more rapid healing induced by low intensity pulsed ultrasound, the earlier mobilization of the affected joint. The beneficial effects on prevention of the musculoskeletal deterioration resulting from the prolonged immobilization would be therefore expected.
authors.affiliation: Musculo-Skeletal Research Laboratory, Department of Orthopaedics and Traumatology, The Chinese University of Hong Kong, Shatin, NT. Lingqin@cuhk.edu.hk
authors.forename: Ling
authors.initials: L
authors.lastname: Qin
authors.forename: Pikkwan
authors.initials: P
authors.lastname: Fok
authors.forename: Hongbin
authors.initials: H
authors.lastname: Lu
authors.forename: Sanqiang
authors.initials: S
authors.lastname: Shi
authors.forename: Yang
authors.initials: Y
authors.lastname: Leng
authors.forename: Kwoksui
authors.initials: K
authors.lastname: Leung
mesh_terms: D000818:Animals; D001857:Bone Matrix / Q000503:physiopathology* / Q000528:radiation effects; D004195:Disease Models, Animal; D005109:Extracellular Matrix / Q000528:radiation effects; D005260:Female; D017102:Fracture Healing / Q000502:physiology* / Q000528:radiation effects; D006244:Hardness / Q000528:radiation effects; D010329:Patella / Q000293:injuries* / Q000528:radiation effects*; D011817:Rabbits; D011829:Radiation Dosage; D013708:Tendon Injuries / Q000503:physiopathology* / Q000628:therapy*; D016896:Treatment Outcome; D014464:Ultrasonic Therapy / Q000379:methods*