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Effects of lower extremity loads on the spine
345
Abstracts EFFECIS OF LOWER EXTREMITY LOADS ON THE SPINE
D. B. BURR, R. B. MARTIN,P. A. MARTIN and D. L. HART (Orthopedic Research Laboratory, West Virginia University, Morgantown, WV 26506, U.S.A.) Post-menopausal osteoporosis is a serious health problem ; this study examined the degree to which loads applied to the lower extremities (as in walking) may produce bone formation in the spine, the site of most osteoporotic fractures. The right hind leg of 3 female rabbits was cyclically (1 Hz) loaded to 1.5 x body weight 20 min/day for 3 weeks. Three control rabbits were “sham loaded”. Tetracycline was used to mark bone formation. It was found that thq applied loads correlated with increased osteonal bone formation in the tibiae and femurs. The humeri were qnaffected. There was increased osteonal labelling in the L6 vertebrae of the experimental animals’ spines, but no@in those of the controls. At the Ll level there was increased osteonal labelling, decreased resorption spaces, and inpreased surface formation. The results show that loads transmitted through the legs to the torso produce bone formation in the spine.
SPINE FIXATION USING PMMA-A
BIOMECHANICAL
lNVESTlGATlON
MANQHARPANJABI,VIJAYGOEL, CHARLE.S CLARK, KRISTAPSKEGGI and WAYNESOUTHWICK
(Section of Orthopaedic
Surgery, Yale Medical School, New Haven, CT 06510, U.S.A.)
Polymethylm&zrylate (PMMA) has been used in the past to stabilize spines inflicted with metastatic tumors. More recently its use has been advocated in younger patients to fix injured spines on a long term basis. The quality of Ph4MA stabilization must be measured biomechanically to assess its applicability. This paper invtotigates the three-dimensional motion behavior of an actual cervical spine surgical construct, obtained from a patient, subj&ted to different load types and utilizing the photogrammetric technique. To determine its strength the specimen was subjected to flexion load until failure. The results were compared to those obtained from an intact spine sdgment. The PMMA seems to provide effective stabilization of the cervical spine, it reduces range of motion and liray produce regions of high stress concentration.
EXPERIMENTAL
AND THEORETICAL MODELS OF CERVICAL INJURY
JOELMYKLEBUST,CHRISHOUTERMAN, ANTHONYSANCES,JR., JOSEPH CUSICK, SANFORD LARSON,THOMASPRIETOand MICHAELCHILRERT(Department of
ROBERT WEBER,
Neurosurgery and Biomedical Engineering, Medical College of Wisconsin, Marquette University, Wood VA Medical Center, Milwaukee, WI, U.S.A.) CHANNINGEWING and DANIELTHOMAS(Naval Biodynamics Laboratory, New Orleans, LA, U.S.A.) Static and dFamic axial tension forces were applied between the shoulders and the skull of living monkeys, fresh human cadayers and isolated monkey and human cadavers, cervical spinal columns and spinal cords. Forces at rates up to 150 cm/s and axial accelerations up to 40Gs were applied with a Series 810MTS system. The isolated monbcey cervical spines failed at 325 to 490N, and in the intact monkeys at 870 to 1550 N. With dynamic loading, cervical damage was observed from 1800 to 2600N. For the human isolated preparations, loads of 1400 to 1800N pr@duced failure. Dynamic failure loads for the isolated and intact human cadavers were substantially above thesevalues. Load deflection curves, Spring constants anddampingcoefficients were measured and used to develop a mathematical model of the cervical spine. The model predicts the energy and force transmitted to the cervical spine. The experimental values are similar to those calculated from the model. (This research was supported in part by the Office of Naval Research Contract No. NOOO14-77-C-0749.)
A JOINT EXAMINATION
INSTRUMENT FOR DIRECT ASSESSMENT OF KNEE JOINT MOTION
JAYNEFRANCIOSE(The Hospital for Special Surgery) A joint exaqination (JE) instrument was developed to measure the rotational and translational movement of the human kneejoint for possible use in joint diagnostics. Six degrees of freedom were employed in the instrument for relative m ovement between the femur and the tibia In the JE, a 6xed reference frame was coNlcctcIcl to a translating&d rotating linkage, which in turn was attached to a known moving reference frame. This resulted in the screw mgtion. The normal angle of motion was tested for six male subjects in normal walking, unweighted flexion and a deep knee bend, such that relative fkxion/extension, varus/valgus, internal/external rotation and the screw orienution were measured between the femur and tibia. The methods of optimum design were used to model these movements of the knee for quantification of variables that might be altered in prosthetic design.
Abstracts EFFECIS OF LOWER EXTREMITY LOADS ON THE SPINE
D. B. BURR, R. B. MARTIN,P. A. MARTIN and D. L. HART (Orthopedic Research Laboratory, West Virginia University, Morgantown, WV 26506, U.S.A.) Post-menopausal osteoporosis is a serious health problem ; this study examined the degree to which loads applied to the lower extremities (as in walking) may produce bone formation in the spine, the site of most osteoporotic fractures. The right hind leg of 3 female rabbits was cyclically (1 Hz) loaded to 1.5 x body weight 20 min/day for 3 weeks. Three control rabbits were “sham loaded”. Tetracycline was used to mark bone formation. It was found that thq applied loads correlated with increased osteonal bone formation in the tibiae and femurs. The humeri were qnaffected. There was increased osteonal labelling in the L6 vertebrae of the experimental animals’ spines, but no@in those of the controls. At the Ll level there was increased osteonal labelling, decreased resorption spaces, and inpreased surface formation. The results show that loads transmitted through the legs to the torso produce bone formation in the spine.
SPINE FIXATION USING PMMA-A
BIOMECHANICAL
lNVESTlGATlON
MANQHARPANJABI,VIJAYGOEL, CHARLE.S CLARK, KRISTAPSKEGGI and WAYNESOUTHWICK
(Section of Orthopaedic
Surgery, Yale Medical School, New Haven, CT 06510, U.S.A.)
Polymethylm&zrylate (PMMA) has been used in the past to stabilize spines inflicted with metastatic tumors. More recently its use has been advocated in younger patients to fix injured spines on a long term basis. The quality of Ph4MA stabilization must be measured biomechanically to assess its applicability. This paper invtotigates the three-dimensional motion behavior of an actual cervical spine surgical construct, obtained from a patient, subj&ted to different load types and utilizing the photogrammetric technique. To determine its strength the specimen was subjected to flexion load until failure. The results were compared to those obtained from an intact spine sdgment. The PMMA seems to provide effective stabilization of the cervical spine, it reduces range of motion and liray produce regions of high stress concentration.
EXPERIMENTAL
AND THEORETICAL MODELS OF CERVICAL INJURY
JOELMYKLEBUST,CHRISHOUTERMAN, ANTHONYSANCES,JR., JOSEPH CUSICK, SANFORD LARSON,THOMASPRIETOand MICHAELCHILRERT(Department of
ROBERT WEBER,
Neurosurgery and Biomedical Engineering, Medical College of Wisconsin, Marquette University, Wood VA Medical Center, Milwaukee, WI, U.S.A.) CHANNINGEWING and DANIELTHOMAS(Naval Biodynamics Laboratory, New Orleans, LA, U.S.A.) Static and dFamic axial tension forces were applied between the shoulders and the skull of living monkeys, fresh human cadayers and isolated monkey and human cadavers, cervical spinal columns and spinal cords. Forces at rates up to 150 cm/s and axial accelerations up to 40Gs were applied with a Series 810MTS system. The isolated monbcey cervical spines failed at 325 to 490N, and in the intact monkeys at 870 to 1550 N. With dynamic loading, cervical damage was observed from 1800 to 2600N. For the human isolated preparations, loads of 1400 to 1800N pr@duced failure. Dynamic failure loads for the isolated and intact human cadavers were substantially above thesevalues. Load deflection curves, Spring constants anddampingcoefficients were measured and used to develop a mathematical model of the cervical spine. The model predicts the energy and force transmitted to the cervical spine. The experimental values are similar to those calculated from the model. (This research was supported in part by the Office of Naval Research Contract No. NOOO14-77-C-0749.)
A JOINT EXAMINATION
INSTRUMENT FOR DIRECT ASSESSMENT OF KNEE JOINT MOTION
JAYNEFRANCIOSE(The Hospital for Special Surgery) A joint exaqination (JE) instrument was developed to measure the rotational and translational movement of the human kneejoint for possible use in joint diagnostics. Six degrees of freedom were employed in the instrument for relative m ovement between the femur and the tibia In the JE, a 6xed reference frame was coNlcctcIcl to a translating&d rotating linkage, which in turn was attached to a known moving reference frame. This resulted in the screw mgtion. The normal angle of motion was tested for six male subjects in normal walking, unweighted flexion and a deep knee bend, such that relative fkxion/extension, varus/valgus, internal/external rotation and the screw orienution were measured between the femur and tibia. The methods of optimum design were used to model these movements of the knee for quantification of variables that might be altered in prosthetic design.