Bone substitutes and implantation depths for subchondral bone repair in osteochondral defects of porcine knee joints.
OBJECTIVE
The purpose of this study was to identify the optimal material and implantation method for subchondral bone repair.


METHODS
Four osteochondral defects in a femoral groove were created in both knees of 12 pigs, and the total number of defects was 96. Eight defects were left empty (empty group). Beta-tricalcium phosphate (β-TCP) bone substitutes with 75 and 67 % porosity were implanted in 30 and 29 defects, respectively (β-TCP75 and β-TCP67 groups). Hydroxyapatite (HA) bone substitutes with 75 % porosity were filled in 29 defects (HA group). Bone substitutes were implanted at 0, 2, or 4 mm below the subchondral bone plate (SBP). The reparative tissue was assessed using microfocus computed tomography and histology 3 months after implantation.


RESULTS
Regardless of the kind of bone substitutes, the defects were filled almost completely after implanting them at the level of the SBP, while the defects remained after implanting them at 2 or 4 mm below the SBP. Reparative tissue of the β-TCP75 group was similar to the normal cancellous bone, while that of the β-TCP67 or HA group was not.


CONCLUSIONS
Subchondral bone defects were filled almost completely only when bone substitutes were implanted at the level of the SBP. The reparative tissue after implanting the β-TCP bone substitutes with 75 % porosity was the most similar to the normal cancellous bone. Therefore, implanting the β-TCP bone substitutes with 75 % porosity at the level of the SBP could be recommended as a treatment method for subchondral bone repair in osteochondral defects.


METHODS
I.
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Tomohiko
T
Matsuo
Department of Sports Orthopaedics, Osaka Rosai Hospital, 1179-3, Nagasone-cho, Kita-ku, Sakai, Osaka, 583-8555, Japan.
Keisuke
K
Kita
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Tatsuo
T
Mae
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Yasukazu
Y
Yonetani
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Satoshi
S
Miyamoto
Department of Orthopaedic Surgery, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka, 565-0871, Japan.
Hideki
H
Yoshikawa
Medicine for Sports and Performing Arts, Department of Health and Sports Sciences, Osaka University Graduate School of Medicine, 1-17 Machikaneyama-cho, Toyonaka, Osaka, 560-0043, Japan. ken-nakata@umin.ac.jp.
Ken
K
Nakata
D000818:Animals; D018786:Bone Substitutes / Q000494:pharmacology*; D004195:Disease Models, Animal; D005260:Female; D005264:Femoral Fractures / Q000175:diagnosis / Q000601:surgery*; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D007718:Knee Injuries / Q000175:diagnosis / Q000601:surgery*; D007719:Knee Joint / Q000601:surgery*; D019736:Prostheses and Implants; D011474:Prosthesis Design; D013552:Swine; D013556:Swine, Miniature; D014057:Tomography, X-Ray Computed
D018786:Bone Substitutes