The rate of longitudinal bone growth in the physeal plate is modulated by the size of pool of proliferative chondrocyte, the rate of cell division of proliferative chondrocyte, the height of terminal hypertrophic chondrocyte and matrix production
in the
transverse septa. The parameters such as growth plate thickness and the rate of cell division by proliferating chondrocytes have been indentified as useful indices of longitudinal bone growth rate. Recently the height and volume of hypertrophics
have
been reported to be one of the decisive factors in modulating the longitudinal growth rate.
Fracture, osteotomy or limb lengthening have been known to affect the longitudinal growth rate and, it can be assumed, they could change the relationship betweengrowth rate andparameters.
The purposes of this study were to clarify the relationship betweenparameters and longitudinal bone growth in osteotomized and lengthened limbs and to compare the relationship between the different groups which showed changed growth rate
affectedby
the
amount of lengthening.
Sixteen eight weeks oldNew Zealand white rabbitswere allocated into four groups; Group I was osteotomized and stabilized by external fixater but without lengthening, Group II was lengthened 20% of total tibial length at a rate of 0.8mm/day with
external
fixater, Group III was lengthened 30% at a rate of 0.8mm/day andGroup IV was lengthened 40% to 50% at a rate of 3.2mm/day. Left tibia was used for that procedure and right tibia was left as acontrol. In the proximal & distalphyses ofboth tibia,
following measurements were performed. The longitudinal growth rates were determined by tetracychine labeling and indirect light fluoroscence microscopy. The physeal thickness was histomorphologically measured and the proliferative rate of
chondrocytes
in physeal plate was assessed by immunohistochemical staining using anti-bromodeoxyuridine monoclonal antibody.
@ES The results obtained were as follows ;
@EN 1) The physeal thickness and the number of proliferating chondrocytes had linearcorrelation with longitudinal growth rate in the physis of the lengthened or osteotomized tibia of rabbits.
2) The relationship of the physeal thickness and the number of proliferating chondrocytes with longitudinal growth rate had highercorrelation coefficiency and different slope of regression in the proximalphysis of lengthened or osteotomized
tibia
of
rabbits compared to that in the distal physis of lengthenedorosteotomizedtibia ofrabbits.
3) The relative contribution of the physeal thickness orthe number of proliferating chondrocytes tothe longitudinal growth rates varied following the varied amount or rate oflengtheninginthe physis of lengthened orosteotomizedtibia of rabbits.
As a conclusion, physeal thickness and the number of proliferating chondrocytes are considered to be significant parameters of longitudinal growth ratein the osteotomized orlengthened limb, but they may contribute to longitudinal growth rate
differently
according to the location, ageand local condition of the physis.
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