Histologic evaluation of osteochondral loose bodies and repaired tissues after fixation.
OBJECTIVE
The purpose of this study was to evaluate histologic changes in osteochondral loose bodies in the rabbit knee joint and histologic changes in repaired tissue after fixation of osteochondral loose bodies following isolation periods of varying length.


METHODS
We harvested osteochondral fragments from the patellar groove in rabbit knee joints and left them in the lateral gutters of the joints for periods of varying duration to create osteochondral loose bodies. We then evaluated histologic and immunohistochemical changes within these loose bodies. Next, we fixed osteochondral loose bodies that had been isolated for various periods within the joints to the osteochondral defect in the patellar groove. Twelve weeks after fixation, repaired tissues were evaluated histologically and immunohistochemically, and results were analyzed according to the varying isolation periods of fragments.


RESULTS
Extracellular matrix and type II collagen expression of osteochondral loose bodies deteriorated with increased duration of fragment isolation periods. A significantly negative correlation was noted between length of isolation periods and histologic grading scores. After osteochondral loose bodies had been fixed, repaired tissues deteriorated significantly in accordance with duration of fragment isolation periods. However, in some cases, even when osteochondral fragments had been isolated for 12 weeks, repaired tissues showed dense extracellular matrix stained by safranin O and abundant type II collagen expression, which indicated regeneration of the cartilage layer.


CONCLUSIONS
Osteochondral loose bodies and repaired tissues deteriorated after they were fixed to osteochondral defects. Although a direct correlation was noted between isolation periods of fragments and time to their deterioration, some osteochondral loose bodies showed regeneration of cartilage after fixation.


CONCLUSIONS
Clinically, reduction of osteochondral loose bodies should be performed as early as possible, if these can be found. However, even if the fragment seems to be old, fragment fixation is worthy of consideration.
Touten
Yoriko
Y
Department of Orthopaedic Surgery, Graduate School of Biomedical Sciences, Hiroshima University, Hiroshima, Japan.
Adachi
Nobuo
N
Deie
Masataka
M
Tanaka
Nobuhiro
N
Ochi
Mitsuo
M
D000818:Animals; D002358:Cartilage, Articular / Q000293:injuries / Q000473:pathology* / Q000601:surgery*; D024043:Collagen Type II / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000502:physiology; D007594:Joint Loose Bodies / Q000473:pathology* / Q000601:surgery*; D007719:Knee Joint / Q000473:pathology*; D008297:Male; D019637:Orthopedic Procedures; D011817:Rabbits; D012038:Regeneration / Q000502:physiology; D013997:Time Factors
D024043:Collagen Type II