Evidence-Based Practice: Hip fractures, fixation devices, and post-operative mobility

There are more than 40 000 new hip fractures occurring in people over the age of 65 each year in Canada. The increasing average life expectancy of people in our society also means that they have an increased chance of developing osteoporosis. This combined with an enhanced risk of falls due to reductions in neurological and musculoskeletal functioning indicates an increased risk of hip fractures; specifically proximal femur fractures. The surgical intervention chosen for management of proximal femur fractures in an elderly patient plays a crucial role in deciding a successful return to safe mobility and pre-operative functioning. The type of implant to achieve this must meet specific criteria including: 1) It can be inserted via a minimally invasive operation technique, 2) It has a post-operative indication of close to full body weight bearing capacity, and 3) It has a low peri and post-operative complication rate.

The dynamic hip screw (DHS) is an extramedullary device used in the treatment of proximal femur fractures. It consists of a large cannulated screw inserted through a side-plate that is fixated on the lateral aspect of the femoral shaft. The DHS has been the most popular implant choice for the treatment of proximal femur fractures over the past two decades, due to a fracture union rate of >95%. However, in the treatment of unstable fractures, mechanical failure occurs in 6-28% of the cases due to large bending moments on the implant. Intramedullary devices such as the gamma nail, and the proximal femur nail, were designed to overcome the high rate of mechanical failure associated with the DHS. These devices consist of a long nail inserted into the diaphysis of the femur, and a stabilizing locking screw advanced through the lateral femoral cortex into the head of the femur.

The insertion of the gamma nail indicates a smaller incision and requires less soft tissue disruption than with the insertion of the DHS. Estimated blood loss is also significantly less for the gamma nail than for the DHS. Thus, a smaller incision, less soft tissue disruption and a decrease in blood loss is indicative of less post-operative pain and earlier mobility. Nonetheless, a post-operative complication rate of 18% with the gamma nail has been reported, with the major complication encountered being the cutting out of the screws in the femoral head leading to instability of the fracture.

To combat the complications associated with the gamma nail the trochanteric fixation nail (TFN) was designed, and it was released for use in several US test markets in 2002. Changes made include a helical blade design, which upon insertion allows for a greater compaction of the cancellous bone in the head of the femur. The retention and compaction of cancellous bone in the femoral head indicates less of a chance of screw migration and the resulting fracture instability associated with it. For the most part, selection of the TFN in the treatment of proximal femur fractures indicates a post-operative, full body weight bearing status.

From a physiotherapy perspective, advancements in the design of the surgical implants used to fixate proximal femur fractures in the elderly, specifically the TFN, have resulted in earlier post-operative mobility which indicates a higher level of post-operative functioning and independence in patients.

Allison Burns – MSc (PT) Candidate (2010)