The influence of age, bone quality and body mass index on periprosthetic femoral fractures: a biomechanical laboratory study.
BACKGROUND
A periprosthetic femoral fracture after total hip arthroplasty is a serious but uncommon complication, and therefore difficult to analyze clinically in scientifically and statistically valid study samples. With the aim of preventing these fractures the purpose of this study was to investigate potential risk factors associated with cementless hip arthroplasty in a standardized laboratory setup. Additionally, we aimed to clarify if the treatment with a cementless hip stem is fraught with higher risk of periprosthetic fracture for older patients compared to younger patients.


METHODS
A biomechanical setup was developed to provide analysis on sixteen femoral specimens of different age. A cementless hip stem was implanted into the specimens and loads - representing hip contact forces - were applied under standardized conditions until fracture occurred. The femurs were divided into two age groups (<70 and >or=77 years of age).


RESULTS
The elderly specimens fractured at significantly lower maximum forces (<70: Fmax=5,308N; >or=77: Fmax=2,519N; p<0.01). Maximum fracture loads were found to correlate strongly with age (p=0.01), BMD (e.g. for the Ward's triangle: p<0.01) and BMI (p=0.04).


CONCLUSIONS
In patients with advanced age treated with cementless hip stems the risk of suffering a periprosthetic fracture is significantly higher. It increases in patients with an age of 80 years or older, a Ward's triangle BMD below 0.500 g/cm2 and a BMI >33 kg/m2. Whereas one single factor must not be viewed as an exclusion criterion for a cementless hip stem treatment, cumulation of these factors should alert the orthopaedic surgeon.
University of Heidelberg, Department of Orthopaedic Surgery, Heidelberg, Germany.
Eike
E
Jakubowitz
Jörn Bengt
JB
Seeger
Jan Philippe
JP
Kretzer
Christian
C
Heisel
Jennifer Aileen
JA
Kleinhans
Marc
M
Thomsen
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D001842:Bone and Bones / Q000503:physiopathology*; D019411:Clinical Laboratory Techniques; D005260:Female; D005264:Femoral Fractures / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D057068:Periprosthetic Fractures / Q000503:physiopathology*; D014019:Tissue Donors; D016474:Weight-Bearing / Q000502:physiology