Abstract
Introduction
Femoral neck fracture is a common injury in elderly patients. To restore the activity with an acceptable morbidity and to decrease of mortality, surgical procedures are thought to be superior to conservative treatments. Osteosynthesis with internal fixation for nondisplaced type, and hemiarthroplasty or total hip replacement (hip arthroplasties) for displaced type are commonly performed.
Cemented arthroplasty has been preferred over non-cemented arthroplasty because of less postoperative pain, better mobility and excellent initial fixation of the implant, especially for osteoporotic and stove-pipe bones. However, pressurizing bone cement may cause cardiorespiratory and vascular complications, and occasionally death, which has been termed as “bone cement implantation syndrome”. To avoid the occurrence of this syndrome, non-cemented implants have been developed. However, most implants with the press fit concepts and flat wedge taper designs have a risk of intraoperative and early postoperative periprosthetic fracture.
Recently, we have employed a non-cemented femoral component, which has a lateral expansion to the proximal body as compared to a conventional hip stem. Because of this shape, which is called a “lateral flare”, this stem provides a physiological loading on both the medial and lateral endosteal surfaces of the femur. This is in contrast to conventional hip stem which prioritizes loading on the medial and metaphyseal /dyaphyseal surfaces of the femur. Moreover, the cross section of this stem is trapezoid with the flat posterior surface. This shape provides the stem with rotational stability along the long axis of the femur, and maximizes loading transfer to the posterior aspect of the proximal femur. These mechanical features avoid the need for aggressive impaction of the stem at the time of insertion. It is necessary to only tap gently to achieve the secure initial implant fixation by a “rest fit”. Thus, this technique reduces the risk of fracture.
Patients and methods
We employed this technique using a non-cemented lateral flare design device for displaced femoral neck fractures since 1996. Surgical procedures were performed with posterior approach under the spinal or epidural anesthesia. Full weight bearing ambulation with a walker was allowed on post-op day one.
Results and discussion
Since that time, we have had no femoral fracture, no dislocation of the hip, nor severe complications intraoperatively and post operatively. There has been no evidence of radiographic aseptic loosening or axial migration of the stems during this time period.
Conclusions
“Rest fit” surgical technique avoids complications associated with cemented and traditional non-cemented arthroplasties for displaced femoral neck fractures. It however requires specific geometric features to be included the designs of the femoral component to assure secure initiate fixation at the time of arthroplasty. Therefore, this lateral flare implants are effective for the treatment of the displaced type of femoral neck fracture.
