An intramedullary nail with multifunctional interlocking for all types of fracture in both femurs

Abstract

A femoral compound interlocking intramedullary nail (FCIIN) was designed to treat all types of fractures between the trochanter and epicondyle of both femurs. It could substitute for femoral interlocking intramedullary nails (FIIN) at five points. According to the morphological characteristics of the femoral medullary canal, the nail is designed to accommodate a 1250 mm radius of radian and a 135° neck-shaft angle. Three interlocking holes of 6.5 mm diameter are located at the proximal end of the FCIIN, making crossing of the screws possible. The hole is designed to be vertical (90°) or oblique (45° upper or lower). At the tip of the proximal interlocking screws, whose root diameter gradually increases from 3.5 mm to 6.5 mm, a self-tapping cancellous screw is placed. There are two types of distal interlocking screws. One is a fine thread and the other a bolt screw. Two interlocking holes and a recess 4.5 mm in diameter are located at the distal end of the FCIIN. Under biomechanical destructive testing, the proximal interlocking screw device has satisfactory strength and reasonable structure. A total of 47 patients (31 males and 16 females, with an average age of 39.83 years) with femoral fractures were assessed in this study. Fourteen cases were diagnosed as intertrochanteric, 7 as subtrochanteric, 18 as femoral shaft, and 8 as supracondylar fractures. All 47 patients were treated with the FCIIN. Of the 47 patients, anatomic reduction was achieved in 34, good reduction in 11, and forced line reduction in 2 cases. Reduction was excellent or good in 95.87% of the fractures. The removal time of the FCIIN was 12 to 21 months (average, 16.9 months). One patient with an intertrochanteric fracture who had a fixation failure combined with non-union achieved healing with an external fixator at 18 months. Failure to insert the distal interlocking screws occurred in 5 patients but did not affect bone healing. The FCIIN is a useful device in the treatment of a variety of femoral fractures.