Experimental Research of Muscle Function during Leg Lengthening

Research Project

Project/Area Number	07671628
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Orthopaedic surgery
Research Institution	Osaka Medical College
Principal Investigator	ABE Muneaki Osaka Medical College, Department of Orthopedic Surgery, Professor, 医学部, 教授 (70084994)
Co-Investigator(Kenkyū-buntansha)	YAMAZAKI Hisashi Osaka Medical College, Department of Orthopedic Surgery, 医学部, 専攻医山崎久大阪医科大学, 医学部, 専攻医長岡孝恭大阪医科大学, 医学部, 専攻医
Project Period (FY)	1995 – 1996
Project Status	Completed (Fiscal Year 1996)
Budget Amount *help	¥1,700,000 (Direct Cost: ¥1,700,000) Fiscal Year 1996: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1995: ¥1,200,000 (Direct Cost: ¥1,200,000)
Keywords	Limb Lengthening / Skeletal Muscle / Morphological Study
Research Abstract	Objective : In the clinical application of callotasis, among the changes that occur in skeletal muscle during this procedure, main factors restricting limb lengthening, is still unclear. We studied the morphological changes of skeletal muscle subjected to gradual lengthening. Materials and Methods : Adult Japanese white rabbits were used. Midportion of the tibia was cut and modified Orthofix M-100 was applied. After 7 days of waiting period, the tibia was subject to 0.5mm*2per day callus distraction for 20 days. Immediately and 1 month after the completion of lengthening, the rabbits were killed, and the central parts of the anterior tibial muscles and soleus muscles were fixed by freezing, sliced into transverse sections (thickness, 7mum), and stained with ATPase and SDH.Lengthening group was compared with a normal group and an osteotomy group, with regard to changes in the distibution and diameter of different types of muscle fibers. Results : 1) Distribution of muscle fibers according … More to type : In the anterior tibial muscle, Typel fibers increased only in the lengthening group, but the type 2b fibers decreased both in the osteotomy group and the lengthening group. No discernible change was observed in the soleus muscle. 1 month after the completion of lengthening, similar changes were seen. 2) Diameter of muscle fibers according to type : In the anterior tibial muscle, only atrophy of type 2b fibers in the osteotomy group was observed, and atrophy of type 2b fibers as well as hypertrophy of type 1 fibers in the lengthening group were seen. In the soleus muscle, atrophy of both types of fibers in the lengthening group was recognized. 1 month after the completion of lengthening, these changes tended to recover. Discussion : As for the change of the diameter in different types of the anterior tibial muscle, atrophy of type2b fibers might be attributed to weight sparing. The hypertrophy of type1 fibers was ascribed to the myotactic reflex in response to extension stimulation associated with lengthening. In the soleus muscle, it resulted in the atrophy of all fiber types, because extension stimulation in the soleus muscle was less than that in the anterior tibial muscle. Regarding the distribution of the different types of muscle fibers, mechanical stimulation such as gradual lengthening, might be associated with a qualitative change in type2 fibers and a shift toward an increased proportion of type1 fibers. Conclusion : Different types of muscle fibers underwent distinct qualitative changes during limb lengthening. Such changes were different in each skeletal muscle. Less