Most hip fractures are treated surgically, with use of either internal
fixation or prosthetic replacement of the femoral head. The presence
of these implants increases the risk of a later femoral fracture
in susceptible osteoporotic patients. The purpose of this study
was to analyze the incidence of and risk factors for implant-related
fractures of the femur after previous hip fracture surgery.
Over a ten-year period from January 1988 to December 1997, 6230
patients (median age, eighty-two years; male:female ratio, 1247:4983)
who sustained a total of 6696 hip fractures were admitted to the
Edinburgh Orthopaedic Trauma Unit. Demographic information on the
patients and details of the original treatment of the hip fracture
were prospectively coded and entered into a trauma database. All
subsequent readmissions due to a femoral fracture related to the
implant were prospectively audited and extracted for the purposes
of this study.
One hundred and forty-one patients sustained an ipsilateral fracture
of the femur at a median of twenty-four weeks following the original
hip fracture surgery. Survivorship analysis of the hip fracture
population revealed an overall rate of subsequent femoral fracture
of 2.9% at five years, which increased to 5.1% at ten years. The
median age and gender distribution of the patients who sustained
a subsequent femoral fracture were similar to those of the hip fracture
population as a whole. Two-thirds of the fractures propagated from
the tip of the implant.
Analysis of the subsequent fractures according to the type of implant
used to treat the original fracture revealed considerable differences
in incidence. The incidence was relatively high in the patients
initially treated with a Gamma nail (18.74 fractures per 1000 person-years)
or a cementless hemiarthroplasty (11.72 per 1000 person-years) and
was relatively low in those treated with a compression hip screw
(4.46 per 1000 person-years), cannulated screws (4.50 per 1000 person-years),
or a primary arthroplasty with cement (6.2 per 1000 person-years).
The highest incidence of fracture was seen in the patients who had
required an arthroplasty with cement as a revision procedure following
failure of a primary implant (22.39 per 1000 person-years).
Implant-related fractures following hip fracture surgery are more
common than has previously been appreciated. The risk of later ipsilateral
femoral fracture is increased by the use of a Gamma nail or a cementless
hemiarthroplasty to treat the original hip fracture.