The structural properties of an osteochondral cylinder graft-recipient construct on autologous osteochondral transplantation.
OBJECTIVE
The purpose of this study was to investigate the changes in structural properties of an osteochondral cylinder graft-recipient construct after autologous osteochondral transplantation.


METHODS
A full-thickness cylindrical osteochondral defect (5 mm in diameter and 3 mm in depth) was made on the femoral condyle of a mature female Japanese white rabbit using the Osteochondral Autograft Transfer System (OATS; Arthrex, Naples, FL). The defect was repaired with an osteochondral plug (6 mm in diameter and 3 mm in depth) taken from the contralateral femoral condyle using the OATS. The implanted osteochondral grafts were evaluated immediately after surgery and at postoperative weeks 1, 3, 8, and 12. The stiffness of articular cartilage was analyzed using a tactile sensor system (AXIOM, Fukushima, Japan), which measures stiffness based on changes in resonance frequency when a vibrating tactile sensor touches articular cartilage. The specimens were stained with hematoxylin and eosin and serial sections were examined microscopically.


RESULTS
The cartilage stiffness of the graft immediately after surgery was 107,695.1 N/m, which was not statistically different from the normal cartilage stiffness (100,027.5 N/m). The stiffness at postoperative weeks 1, 3, 8, and 12 was 95,386.8, 92,899.3, 95,969.8, and 104,683.7 N/m, respectively. The stiffness at postoperative weeks 1, 3, and 8 was significantly lower than the normal cartilage stiffness and the stiffness at postoperative week 12 was the same as normal cartilage. A new bone formation with an increase of bone trabeculae between the osteochondral cylinder graft and the recipient was observed at postoperative weeks 1, 3, and 8. Thereafter, at postoperative week 12, bone trabeculae decreased to the same level as observed in a normal model due to the progress of bone remodeling.


CONCLUSIONS
The stiffness of articular cartilage of the osteochondral graft was normal at the time the graft was initially placed and at postoperative week 12. However, the stiffness at postoperative weeks 1, 3, and 8 was lower than the normal cartilage stiffness.


CONCLUSIONS
Care should be taken when planning the rehabilitation program at an early phase after osteochondral transplantation.
Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, Kobe, Japan.
Noriyoshi
N
Nakaji
Hiroyuki
H
Fujioka
Issei
I
Nagura
Takeshi
T
Kokubu
Takeshi
T
Makino
Hiroshige
H
Sakai
Ryosuke
R
Kuroda
Minoru
M
Doita
Masahiro
M
Kurosaka
D000818:Animals; D001696:Biomechanical Phenomena; D016723:Bone Remodeling; D002358:Cartilage, Articular / Q000637:transplantation* / Q000648:ultrastructure; D019902:Chondrocytes / Q000637:transplantation; D005260:Female; D005269:Femur / Q000637:transplantation* / Q000648:ultrastructure; D008422:Materials Testing / Q000295:instrumentation; D018583:Pliability; D011184:Postoperative Period; D011817:Rabbits; D013314:Stress, Mechanical; D014182:Transplantation, Autologous / Q000295:instrumentation / Q000379:methods