Approximately 15% of all fractures in children involve the physis. Although the majority heal without impairment of the growth mechanism, epiphyseal growth plate fracture-seperation can lead to shortening and angulation. The physiologic events in epiphyseal growth fracture seperation that lead to growth disorders relate to 1) destruction of the epiphyseal circulation and 2) communication between the epiphyseal circulation with its osteoprogenitor cells, thus forming a bony bridge. Although the classic procedure of osreotomy, epitphysiodesis, leg shortening and leg lengthening have not lost their importance in the treatment of the sequeales of partial closure of an epiphyseal plate, the possibility of regaining growth in the affected region should be considered before other measures are taken. Simple excision of the bone bridge is ineffective, since the large cancellous surface thus produced will allow for rapid reformation of the bridge. Thus, a material has to be interposed into the defect created by removal of such a bridge in order to prevent its reformation. Langenskiold first demonstrated that a bone bridge could be effectively resected and its reformation pre- ventedby utilizing fat as an interposition material. Other investigators have used a variety of different interposition materials to prevent bone bridge recurrence following operative removal including cartilage, Silastic, Methymethacrylate, bone wax, muscle flap, Gelfoam as well as fat. Thus it is the purpose of this study to analysis and comparing shortening and angulation by resection of a bone bridge and its replacement with different interposition materials. For this study, a total of 32 rabbits with an initial weight of about 600 to 800 gm was used. Control group comprised 4 rabbits and after appmpriate preparation, the medial condyle of the pmximal tibia was exposed surgically. One plug of bone was removed at the level of the epiphyseal plate using a small curet to a depth of 5 mm. and in the other groups, we made a defect with the same curet and filled it with an interposition material directly. The following experimental groups were created. Group 1 (N-4) Control group: no interposition material Group 2 (N-4) Gelfoam interposition material Group 3 (N-4) Bone was interposition material Group 4 (N-4) Muscle flap interposition material Group 5 (N-4) Fat interposition material Group 6 (N-4) Bone cement interposition material Group 7 (N-4) Silastic interposition material Postoperatively the anirnals were sacrificed 15wks following operation. As sacrifice, tibia including fibular is removed, examined grossly and radiographed. Tibia length and angular deformity were determined by measurement of radiographs. Specimens stained with H-E stain were observed during 15 wks after operation. Through these examination, following results were obtained. l. In control group, coronal histological sections of each curetted proxirnal tibial growth plate revealed osseous bridging as early as 3 wks, and this bridging was found consistently in all control groups for the duration of the study. 2. The groups using gel foam, muscle flap and bone wax as interposition material were found effective for the prevention of the formation of epiphyseometaphyseal bone bridge to some extent. 3. The groups using Silastic or bone cement diminished both the angular deformity and growth retradation to a highly significant degree. Although the use of fat did reduce somewhat the amount of shortening and angular deformity when used as an interposition material, it was not effective as Silastic or bone cement. 4. Coronal histological section of the traumatized, margin of the growth plate, with an interposition material revealed thin fibrous layer and lose columnar orientation, foam rounded clone-like structures and randomness to growth. The injured portion of the cartilage may originate from the regeneration of the adjacent part of the growth plate. From these morphological and radiological results, it is suggested that Silastic or bone cement is better interposition material in the elimination of trahsphyseal closure after physeal damage.