Importance of pre-clinical testing exemplified by femoral fractures in vitro with new bone preparation technique.
BACKGROUND
A new bone preparation technique, using smooth tamps for bone compaction, has increased crucial initial implant stability. However, preparing the femur with bulky smooth tamps, which from size to size increases the same amount in anterior to posterior as in lateral to medial dimensions, has increased the risk of a femoral fracture. This study examined whether compaction also involved an increased femoral fracture risk when using newly developed smooth tamps with a slim anterior to posterior dimension.


METHODS
One femur in each pair of 10 cadaver femurs was prepared by the compaction technique using cylindrical reamers and smooth tamps. The contralateral femur was conventionally prepared with conical reamers and toothed rasps. The tamps and rasps differed in design as a proximal lateral tip was only present on the smooth tamps. Using a standardized test protocol, the instruments were driven into the femoral canal in controlled manner by a drop tower.


RESULTS
At maximum test conditions, five of 10 femurs in the compaction group had fractured, as compared with no fractures in the rasping group. All fractures were longitudinal fissures in the greater trochanter, and these fissures were associated with the extended proximal lateral tip of the tamps.


CONCLUSIONS
Since the lateral fractures in the compaction group were associated with the extended proximal lateral tip of the tamps, it seems that fracture rates are influenced by instrumentation design. Therefore adequate pre-clinical evaluation is warranted prior to the introduction of new implantation techniques.
Kold
Søren
S
Orthopaedic Biomechanics Laboratory, Midwest Orthopaedic and Minneapolis Medical Research Foundations, Minneapolis, MN, USA. s.kold@dadlnet.dk
Bechtold
Joan E
JE
Mouzin
Olivier
O
Bourgeault
Craig
C
Søballe
Kjeld
K
D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000379:methods*; D002102:Cadaver; D019544:Equipment Failure Analysis / Q000379:methods; D005260:Female; D005264:Femoral Fractures / Q000209:etiology* / Q000473:pathology*; D005269:Femur / Q000473:pathology* / Q000601:surgery*; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000009:adverse effects / Q000379:methods