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Axial, bending & torsional stiffnesses of five configurations of the Hoffmann fracture-fixation frame
481
Abstracts AXIAL, BENDING & TORSIONAL STIFFNESSES OF FIVE CONFIGURATIONS HOFFMANN FRACTURE-FIXATION FRAME
OF THE
J. B. FINLAY, J. HALPENNY,T. MOROZ, J. R. DAVEY and C. H. RORABECK(Division of Orthopaedic Surgery, University of Western Ontario, London, Ontario, Canada, N6A 5x5) Standard externally-applied Hoffmann fracture-fixation parts have been studied in five different configurations. to determine their relative stiffnesses and abilities to withstand loads applied in axial compression, bending (both AP and lateral) and torsion. The frames were studied on dressed pine-wood pylons of 400 mm length and 40 x 40 mm cross-section. A transverse osteotomy was created in mid-shaft and results were obtained with the fracture-surfaces mated and with them separated by 10 mm. Configurations tested were: unilateral half-frame; half-frame with two connecting rods; two unilateral frames oriented at 45’ to one another; a rectangular bilateral frame; and a quadrilateral frame. The stiffest frames in all modes were the double half-frame and the quadrilateral frame. Loads were applied at controlled rates as follows: up to 1200 N axial compression; up to 500 N were applied in bending to cause couples up to 25 Nm either side of the fracture; and up to 25 Nm in torsion. Although all universal joints and articulation-couplings were tightened to 10 Nm, slippage of these joints was a common occurrence and did not necessarily correlate with a low frame-stiffness.
l-i. OCCUPATIONAL
BIOMECHANlCS
CONCEPTS OF PRE-ElMPLOYMENT SCREENING AND HIRING FORCES
STANDARDS
FOR SAFETY
RICHARDMOSTARDI,JAMES PORTERFIELDand STEVENKING (Akron City Hospital, Department of Physical Fitness Testing, Akron, OH 44309, U.S.A.) 33 I Akron policemen volunteered to be part of a physiological study (cardiovascular musculoskeletal testing) for the purpose of establishing individualized risks for coronary artery disease and evaluation of musculoskeletal disorders and to establish job specific norms from which to compare incoming police candidates. The testing protocols and data reduction are discussed. The use of these data as a standard for which to hire policemen and subsequent 3 yr re-testing to monitor body weight and blood pressure is presented. The authors conclude that municipalities can be convinced as to the importance of maintaining good health to the point of utilizing the data as hiring standards for incoming police recruits.
MAXIiMUM VOLUNTARY STRENGTH AND MAXIMUM ACCEPTABLE WEIGHTS FOR ASYMMETRIC LIFTING ARUN GARG (Industrial and Systems Engineering, University of Wisconsin, Milwaukee, WI 53201. U.S.A.) The objective of this research was to study the effects of asymmetric lifting on a maximum voluntary isometric strength (MVIS) and maximum acceptable weights. Thirteen male subjects lifted three different boxes (small, medium and large) at 0,30,60 and 90” from sagittal plane. Maximum voluntary isometric strength (MVIS) was also measured to simulate the above twelve lifting tasks (three box sizes x four angles). A preliminary statistical analysis showed that there was a significant decrease in both MVIS and maximum acceptable weights with an increase in asymmetric lifting. Relative effects of box size and asymmetric lifting on MVIS and maximum acceptable weights are discussed.
METABOLIC COST MODELING
FOR LIFTING
AND LOWERING
S. KUMAR (University of Alberta, Edmonton, Alberta, Canada T6G 2G4) Oxygen uptake values from sixyoung adult males (mean age 27.3 yr, mean weight 73.8 kg, mean height 179.75 cm and mean reach of 62.3 cm) were obtained while they lifted and lowered 2.5 kg, 5.0 kg and 10 kg between the floor and their respective knee, hip and shoulder level heights. These activities were performed at their half, three quarter and full reach distances in midsagittal, 30” and 60” lateral planes. The results showed that metabolic cost
Abstracts AXIAL, BENDING & TORSIONAL STIFFNESSES OF FIVE CONFIGURATIONS HOFFMANN FRACTURE-FIXATION FRAME
OF THE
J. B. FINLAY, J. HALPENNY,T. MOROZ, J. R. DAVEY and C. H. RORABECK(Division of Orthopaedic Surgery, University of Western Ontario, London, Ontario, Canada, N6A 5x5) Standard externally-applied Hoffmann fracture-fixation parts have been studied in five different configurations. to determine their relative stiffnesses and abilities to withstand loads applied in axial compression, bending (both AP and lateral) and torsion. The frames were studied on dressed pine-wood pylons of 400 mm length and 40 x 40 mm cross-section. A transverse osteotomy was created in mid-shaft and results were obtained with the fracture-surfaces mated and with them separated by 10 mm. Configurations tested were: unilateral half-frame; half-frame with two connecting rods; two unilateral frames oriented at 45’ to one another; a rectangular bilateral frame; and a quadrilateral frame. The stiffest frames in all modes were the double half-frame and the quadrilateral frame. Loads were applied at controlled rates as follows: up to 1200 N axial compression; up to 500 N were applied in bending to cause couples up to 25 Nm either side of the fracture; and up to 25 Nm in torsion. Although all universal joints and articulation-couplings were tightened to 10 Nm, slippage of these joints was a common occurrence and did not necessarily correlate with a low frame-stiffness.
l-i. OCCUPATIONAL
BIOMECHANlCS
CONCEPTS OF PRE-ElMPLOYMENT SCREENING AND HIRING FORCES
STANDARDS
FOR SAFETY
RICHARDMOSTARDI,JAMES PORTERFIELDand STEVENKING (Akron City Hospital, Department of Physical Fitness Testing, Akron, OH 44309, U.S.A.) 33 I Akron policemen volunteered to be part of a physiological study (cardiovascular musculoskeletal testing) for the purpose of establishing individualized risks for coronary artery disease and evaluation of musculoskeletal disorders and to establish job specific norms from which to compare incoming police candidates. The testing protocols and data reduction are discussed. The use of these data as a standard for which to hire policemen and subsequent 3 yr re-testing to monitor body weight and blood pressure is presented. The authors conclude that municipalities can be convinced as to the importance of maintaining good health to the point of utilizing the data as hiring standards for incoming police recruits.
MAXIiMUM VOLUNTARY STRENGTH AND MAXIMUM ACCEPTABLE WEIGHTS FOR ASYMMETRIC LIFTING ARUN GARG (Industrial and Systems Engineering, University of Wisconsin, Milwaukee, WI 53201. U.S.A.) The objective of this research was to study the effects of asymmetric lifting on a maximum voluntary isometric strength (MVIS) and maximum acceptable weights. Thirteen male subjects lifted three different boxes (small, medium and large) at 0,30,60 and 90” from sagittal plane. Maximum voluntary isometric strength (MVIS) was also measured to simulate the above twelve lifting tasks (three box sizes x four angles). A preliminary statistical analysis showed that there was a significant decrease in both MVIS and maximum acceptable weights with an increase in asymmetric lifting. Relative effects of box size and asymmetric lifting on MVIS and maximum acceptable weights are discussed.
METABOLIC COST MODELING
FOR LIFTING
AND LOWERING
S. KUMAR (University of Alberta, Edmonton, Alberta, Canada T6G 2G4) Oxygen uptake values from sixyoung adult males (mean age 27.3 yr, mean weight 73.8 kg, mean height 179.75 cm and mean reach of 62.3 cm) were obtained while they lifted and lowered 2.5 kg, 5.0 kg and 10 kg between the floor and their respective knee, hip and shoulder level heights. These activities were performed at their half, three quarter and full reach distances in midsagittal, 30” and 60” lateral planes. The results showed that metabolic cost