BACKGROUND: T-type or linear type external fixator is applied in transcervical fracture in the elderly. Because its fixing force is weak, so it is difficult to avoid the aggravation of complication due to long term lay up in severe osteoporosis. Based on this reason,percutaneous penetrating arch tri-claw external fixator is designed to treat elderly transcervical fracture with strong fixing force for the realization of early restoration to the active status before injury to reduce complication.OBJECTIVE:To design pereutaneous penetrating arch tri-claw external fixator for the treatment of elderly transcervical fracture for the investigation of its feasibility.DESIGN: A self-controlled study by employing patients as subjects.SETTING: Department of orthopedic surgery of the first affiliated hospital of a universityPARTICIPANTS: Thirty-one cases of elderly transcervical fracture including 18 males and 13 females aged between 71 and 86 years old with an average age of 79 years were admitted by the Department of Orthopedics of the First Affiliated Hospital of Nanhua University between December 2002 and June 2004.METHODS: Percutaneous penetrating arch tri-claw external fixator was applied in the treatment of 31 cases with elderly transcervical fracture for the observation of its clinical effects, and the force-bearing situation and stability of the external fixator during application were analyzed by theoretical mechanics.MAIN OUTCOME MEASURES: ① The functional effects of percutaneous penetrating arch tri-claw external fixator applied in the therapy of transcervical fracture(sub-femoral head type,transcervical type and femoral basilar type); 2② The force-bearing situation and the stability of the fixing point on the fixator; ③ The restoration of activity in hip joint and fracture union time RESULTS: ① Patients could sit and stand immediately after the applicationof the fixator, and its fixing reinforce was analyzed by theoretic mechanics during standing(the force on upper fixing point A, B or C was 1/22, 1/2 or 1/2 of the lower fixing point) . The unidirectional flexion and extension activity of the hip joint overcame hip-inversion and rotational disposition at the distal end of the fracture. The hip-joint axial compression board caused compact embedment and insertion of the fracture end and vertical crush to simulate fracture union by stability and compressive strain. ② The stability of percutaneous penetrating arch tri-claw external fixator: No disposition was found during the application except rotational disposition during activity in sub-femoral head type fracture. The fixation was stable, the operative trauma was less,and the operation was simple with good accommodation. No complication was found due to long-term lay up and no re-disposition due to the loosening of the external fixator was found. ③ The hip-joint flexion-extension function was restored within 7 days averagely and fracture healing time was about 2 to 3 months, average of 2.4 months.CONCLUSION: No re-injury is found dter the application of percutaneous penetrating arch tri-claw external fixator, which has small force bearing at upper fixing point with strong stability. There is strain stimulation on the cross section of the fracture to promote fracture healing. The articular function status before injury could be restored at early stage.