Intramedullary pressure increase for different commercial and experimental reaming systems: an experimental investigation.
OBJECTIVE
To measure the differences in intramedullary (IM) pressure for commercial reamer systems.


METHODS
IM pressure values for the following systems were measured: AO, Biomet, Howmedica grey reamer, Richards, and Zimmer. To investigate the influence of shaft diameter, the AO reamer head was additionally connected to a small shaft (A6/A7). The pressures were measured in plexiglass tubes filled with a mixture of petroleum jelly and paraffin oil with flow properties at 20 degrees C equivalent to those of bovine medullary fat at 36 degrees C. The reaming assemblies were inserted into the tubes using a materials testing machine at a constant speed. In addition, pressure measurements were made using five pairs of human femora to compare Biomet reamers with the AO reamer with thin, flexible drives (A6/A7).


RESULTS
The following pressure distributions were obtained (millimeters of mercury; mean value +/- standard deviation): 9.5-millimeter reamer: low for Biomet (272+/-39); moderate for Richards (810+/-101); and high for Howmedica (990+/-132), AO conventional (1,000+/-97), and Zimmer (1,140+/-183); 13.0-millimeter reamer: low for Biomet (132+/-21), Howmedica (204+/-45), and Zimmer (226+/-33); moderate for AO conventional (474+/-42); and very high for Richards (1,734+/-127). The second worst system (AO conventional: 1,000+/-97) became the second best system by simple reduction of the shaft diameter (A6/A7: 378+/-33).


CONCLUSIONS
A comparison of shaft diameters and pressure increase clearly showed that the system with the thinnest shaft produced the lowest pressure values and vice versa.
Müller
C A
CA
AO/ASIF Development Institute, Davos-Platz, Switzerland.
Schavan
R
R
Frigg
R
R
Perren
S M
SM
Pfister
U
U
D004867:Equipment Design; D005269:Femur / Q000601:surgery; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D006801:Humans; D011312:Pressure