Tensile force in limb lengthening: histogenesis or only mechanical elongation

Although bone response can be evaluated by radiography, there have been no reports in human confirming formation of new soft tissue in limb lengthening. This study evaluated the tensile force between pin clamps in 14 lower limb lengthenings. Legs were lengthened 0.5 mm every 12 hours and the tensile was measured continuously. The tensile force increased simultaneously with each lengthening and decreased gradually. However, the reduction rate of tensile force during the nighttime (120+/-22%) was significantly higher than that during the daytime (72+/-10%). This differed from the stress relaxation phenomenon shown by viscoelastic material and suggested the presence of other phenomena such as histogenesis.