Objective To evaluate the clinical outcome of Vancouver B2 and B3 periprosthetic femoral fractures treated with uncemented modular stems.Methods From September 2011 to April 2014,Twenty-four patients (12 males and 12 females,with the average age 63 years,ranging from 28 to 85 years) with periprosthetic femoral fractures (16 Vancouver B2 and 8 Vancouver B3) were treated with uncemented modular stems.Revision arthroplasty was conducted in all cases by using modular stems with 12 cerclage wirings and 11 great trochanter claw plates.One patient was treated with revision arthroplasty without additional fixations.Extended trochanter osteotomy was performed on 11 patients.Cortical strut allograft was used in 9 patients with severe femoral bone loss.Intraoperative complications including vascular or nerve injury and systemic complications including cardiovascular events,cerebrovascular events and deep vein thrombosis were recorded.Severe postoperative complications such as nonunion,re-fracture,periprosthetic joint infection and dislocation were recorded.The clinical outcome was evaluated by Harris score,Visual Analogue Score and Parker Mobility Score.The radiological outcome was taken to observe the healing status,stem subsidence and stability of the prosthesis.Results Two patients were lost to follow-up.Twenty-two patients were clinically followed-up.Radiological data was recorded in 16 patients.The average follow-up was 33 months (range,12-68 months).All fractures healed within 6 months.The average Harris score improved from 4.0± 1.1 preoperatively to 78.8± 16.2 postoperatively (t=-20.195,P=0.000).The mean Parker Mobility Score improved from 0.5±0.9 preoperatively to 7.0± 1.8 postoperatively (t=-14.835,P=0.000).The mean Visual Analogue Score decreased from 6.4± 1.2 preoperatively to 2.0± 1.5 postoperatively (t=10.879,P=0.000).No nonunion,infection or dislocation was found.One patient underwent re-operation because of re-fracture.Eight mm of prosthesis subsidence was observed in one case at 3 months postoperatively,and reached stable fixation at 6 months postoperatively without further subsidence.Conclusion Uncemented modular stems can achieve distal fixation and implant stability of periprosthetic femoral fractures while retaining optimal biomechanics of the hip.Assisted by femoral reconstruction techniques such as extended trochanter osteotomy,cortical strut allograft,great trochanter claw plates and cerclage wiring,revision arthroplasty using uncemented modular stems could realize optimal outcomes in treating Vancouver B2 and B3 periprosthetic femoral fractures.