Background Lower tibial bone fracture may easily cause bone delayed union or nonunion because of lacking of dynamic mechanical load.Objective Research Group would design a new instrument as Rap System of Stress Stimulation (RSSS) to provide dynamic mechanical load which would promote lower tibial bone union postoperatively.Methods This clinical research was conducted from January 2008 to December 2010, 92 patients(male 61/female 31, age 16-70years, mean 36.3years) who suffered lower tibial bone closed fracture were given intramedullary nail fixation and randomly averagely separated into experimental group and control group(according to the successively order when patients went for the admission procedure). Then researchers analysed the clinical healing time, full weight bearing time, VAS (Visual Analogue Scales) score and callus growth score of Lane-Sandhu in 3,6,12 months postoperatively. The delayed union and nonunion rates were compared at 6 and 12 months separately.Results All the 92 patients had been followed up (mean 14 months). Clinical bone healing time in experimental group was 88.78±8.80 days but control group was 107.91±9.03days. Full weight bearing time in experimental group was 94.07±9.81 days but control group was 113.24±13.37 days respectively (P<0.05). The delayed union rate in 6 months was 4.3% in experimental group but 10.9% in control group(P<0.05). The nonunion rate in 12 months was 6.5% in experimental group but 19.6% in control group(P<0.05). In 3, 6, 12 months postoperatively, VAS score and Lane-Sandhu score in experimental group had more significantly difference than them in control group.Conclusions RSSS can intermittently provide dynamic mechanical load and stimulate callus formation, promote lower tibial bone union, reduce bone delayed union or nonunion rate. It is an adjuvant therapy for promoting bone union after lower tibial bone fracture.

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