Positive effect of alendronate on subchondral bone healing and subsequent cartilage repair in a rabbit osteochondral defect model.
BACKGROUND
Cartilage and subchondral bone have recently been considered an osteochondral unit. The treatment of osteochondral lesions is still challenging, but better subchondral bone repair may result in higher quality repaired cartilage.


OBJECTIVE
Alendronate accelerates bone formation in osteochondral defects and affects the quality of the repaired cartilage.


METHODS
Controlled laboratory study.


METHODS
Osteochondral defects were made on the left trochleas of 50 rabbits, which were assigned to 1 of 3 groups: control, ALN (weekly subcutaneous injection of 0.14 mg/mL alendronate), and ALN-S (alendronate injection in the first 8 weeks only). They were evaluated at 4, 8, 24, and 52 weeks. Bone repair was evaluated with microcomputed tomography and histologic evaluation. Cartilage repair was evaluated with ultrasound and histologic analyses.


RESULTS
At 4 weeks, the defects were filled, and cartilage-like repair tissue was observed in the ALN group, whereas the defects were incompletely filled in the control group. Alendronate treatment enhanced early bone formation and mineralization in the osteochondral defect for the first 8 weeks. The continuous injection of alendronate for 24 weeks resulted in delayed bone remodeling, but the rabbits in the ALN-S group showed good integrity of the subchondral bone plate, without delayed remodeling. At 52 weeks, the ALN-S group had a columnar arrangement of chondrocytes that had less fibrillation and looked superior to those in the ALN and control groups. Ultrasound analysis showed better quality of repaired cartilage of the ALN and ALN-S group than the control group.


CONCLUSIONS
Alendronate accelerated bone formation without inhibiting its mineralization but thereafter inhibited bone remodeling in an osteochondral defect. The withdrawal of alendronate at 8 weeks avoided the delayed remodeling and showed better subchondral bone repair. At 52 weeks, better subchondral bone repair resulted in better cartilage quality.


CONCLUSIONS
Alendronate administered in the early period accelerates bone formation and improves the quality of the repaired cartilage.
Nishitani
Kohei
K
Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto, Japan.
Shirai
Takaaki
T
Kobayashi
Masahiko
M
Kuroki
Hiroshi
H
Azuma
Yoshiaki
Y
Nakagawa
Yasuaki
Y
Nakamura
Takashi
T
D019386:Alendronate / Q000494:pharmacology*; D000818:Animals; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D016723:Bone Remodeling / Q000187:drug effects; D002356:Cartilage / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000293:injuries; D004164:Diphosphonates; D017102:Fracture Healing / Q000187:drug effects*; D010007:Osteochondritis / Q000601:surgery; D011817:Rabbits; D014463:Ultrasonography
D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D019386:Alendronate