Mechanical evaluation of fracture fixation augmented with tricalcium phosphate bone cement in a porous osteoporotic cancellous bone model.
OBJECTIVE
The purpose of this study was to examine the effects of resorbable bone cement on screw and plate-screw fracture fixation in a porous osteoporotic bone model.


METHODS
Experiment 1: Screw pullout strength was assessed for 4 sets of 4.5-mm cortical screws inserted into a synthetic osteoporotic cancellous bone model, including screws inserted without cement augmentation (control), screws augmented with tricalcium phosphate (TCP) bone cement (Norian SRS; Synthes USA, Paoli, PA), and screws augmented with polymethylmethacrylate. Experiment 2: The effects of cement augmentation on plate-screw fixation strength were examined by performing cantilever bending tests on 4 sets of 8 plate-screw constructions, including nonaugmented and TCP-augmented standard and locked screw-plate constructions in a similar bone model.


RESULTS
Experiment 1: Cement augmentation with both TCP and polymethylmethacrylate increased screw pullout strength from a porous osteoporotic cancellous bone model by about 4-fold (P < 0.05), and there was no significant difference between the 2 cements (P > 0.1). Experiment 2: Fixation strength was 1.5 times higher for locked plates compared with standard plates when neither was augmented with cement (P = 0.07). Cement augmentation with TCP improved fixation strength by 3.6 times for a standard plate-screw construction (P < 0.05) and 3.3 times for a locked plate-screw construction (P < 0.05). The most stable construction was the TCP-augmented locked plate, in which a 5-fold increase was observed compared with that of standard plates without TCP (P < 0.05).


CONCLUSIONS
This study indicates augmenting screws with TCP cement during osteosynthesis improves fixation strength in an osteoporotic cancellous bone model.


CONCLUSIONS
: In fracture situations in which osteoporotic bone makes screw and screw-plate fixation tenuous, screw augmentation with TCP cement should be considered as adjunct treatment.
Collinge
Cory
C
Orthopedic Trauma, Harris Methodist Fort Worth Hospital, John Peter Smith Orthopedic Surgery, Fort Worth TX, USA. ccollinge@msn.com
Merk
Bradley
B
Lautenschlager
Eugene P
EP
D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use*; D001860:Bone Plates; D001863:Bone Screws; D002130:Calcium Phosphates / Q000627:therapeutic use*; D005592:Fracture Fixation / Q000295:instrumentation* / Q000379:methods; D050723:Fractures, Bone / Q000150:complications / Q000601:surgery*; D006801:Humans; D008954:Models, Biological; D010024:Osteoporosis / Q000150:complications*
D001843:Bone Cements; D002130:Calcium Phosphates; C018392:tricalcium phosphate