Experimental Investigations Of The Changes Of Intramuscular Connective Tissue And Passive Range Of Motion During Limb Lengthening

Objective: To investigate the change of intramuscular connective tissue and range of joint motion under various distraction rates during limb lengthening, so as to find out an ideal scheme of lengthening. Under such scheme the changes of intramuscular connective tissue do not influence the function of whole muscle, and so as to provide theory basis for limb lengthening in clinic. Methods: Animal model was established in New Zealand white rabbits for limb lengthening. At 7 days after operation, distraction was initiated at a rate of Imm/d and 2mm/d in two steps, and proceeded until increases of 10% and 20% in the initial length of tibia was achieved. The rabbits were euthanized immediately after the distraction and an additional consolidation phase of another 28 days. The muscle samples were studied with HE staining and picrosirius-polarization method. Image analysis system was used to investigate the changes of thickness of the primary perimysium and the quantitated changes of collagen type I and type III . The ultrastructures of perimysium samples were studied by scanning electron microscope. The range of joint motion was measured using a goniometer designed by us. Results were analysed with analysisof variance. Results: Under light microscopy, the muscle was partitioned into fascicles by the perimysium. Diameters and shapes of muscle fibers were similar in the fascicle, and nucleus locatcded around the muscle fiber. Under the polarization microscopy, the perimysium mainly consisted of collagen type 1 . Under scanning electron microscope, the I'ibers of perimysium were crimped. The crimped fibers connected tightly and orderly. The axis of muscle fibers and crimped fibers formed an angle. The crimped fibers were covered by fine fibrillar collagen, which do not appear to have a regular pattern of orientation, nor do they appear to exhibit the crimp. The range of ankle joint was 9] degree. After limb lengthening, the thickness of the primary perimysium distracted at a rate of 1mm/d and 10% did not change significantly (P>0. 05). The thickness augmented obviously at 20% increase(P<0.05), and became more obviously after consolidation phase of another 28 days(P< 0.01). At a rate of 2mm/d, the thickness of the perimysium was thinner than thai of the control, and there were some signs of pathologic changes in muscle fibers. But after consolidation phase of another 28 days the thickness of the perimysium was thicker than that before consolidation phase. Under the polarization microscopy, the collagen ratio of the perimysium distracted at a rate of Imm/d was the closest to that of the normal perimysium. The percentage of collagen type III increased at a rate of 2mm/d, but after consolidation phase the percentage of collagen type III decreased gradually and The percentage of collagen type I restored. Underscanning electron microscope, the configuration of fibers of perimysium did not change significantly at a rate of Imm/d. At a rate of 2mm/d the fibers of perimysium became straight. The fibers became loosening and there were some interstices in the middle of fibers. Although the interstice disappeared after consolidation phase, fibers did not revert to the crimped one. All the distracted limbs showed a considerable loss of ankle joint motion except these distracted at a rate of Imm/d 10% increase. Conclusions: During limb lengthening, there are various changes in the perimysium under different scheme. The change of the perimysium is not obvious at rate of Imm/d 10% increase, and the distracted limbs do not show a loss of ankle joint motion. The thickness of perimysium become thicker at 20% increase and the range of ankle joint motion decreased appreciably. At rate of 2mm/d pathologic changes occur in the perimysium, and the range of ankle joint motion decreased obviously. These provide theory basis for the cl inical applicalion of lengthening rate of Imm/d in limb lengthening.