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Mechanical properties of lumbar spinal motion segments as affected by partial disc removal
232
C/in. Biomech.
1987; 2: No 4
The effects of medullary reaming on the torsional strength of the femur
The short-term effects of chymopapain discs
The authors have investigated the effect on the torsional strength of the bone of reaming the medulla of the femur from 12 to 16mm in steps of 1 mm. Five groups of femurs. with 10 pairs in each, were tested comparatively in torsional loading and the torque required to cause fracture and the angle through which the bone had twisted at fracture were directly recorded for each pair. The results of maximum torque at failure (expressed as a proportion of the same parameter for the unreamed femur) plotted against the ratio of bone shaft diameter to reamed diameter showed a good correlation. The proportional maximum torque was found to range from 0.63 (at 12 mm) to O-36 (at 16mm) with a sharp transition between 14 and 15 mm. The drastic reduction was felt to be important for both the surgeon and the patient.
Cadaveric lumbar discs were injected with chymopapain and subjected to a series of mechanical tests over a period of up to 19 hours. Discs from the same spine injected with saline were used as controls. The results showed that chymopapain had no measurable effect on the mechanical properties of the disc apart from the increased height and stiffening caused by fluid injection. Another series of tests on isolated pieces of disc material showed that chvmopapain could reduce the size of prolapsed nuclear material by 24% in one hour and by 80% in 48 hours. It is concluded that. in the short-term. chymopapain has a negligible effect on the mechanics of a disc but it can reduce the size of any prolapsed nuclear material with which it comes in contact.
Pratt DJ, Papagiannopoulos 1987: 18: 177-9.
Dolan P, Adams 69-B: 422-8
G, Rees PH, Quinnell
R. Injury
Effects of knee flexion on the structural properties of the rabbit femur-anterior cruciate ligament-tibia complex (FATC) Many studies have been conducted to determine the biomechanical properties of the anterior cruciate ligament (ACL). The method of holding the femur-ACL-tibia complex (FATC) test specimen, the strain rate applied, the angle of knee flexion and the direction of the applied loads have an important effect on the outcome. It is felt that the tensile properties and strength of the ligament should be measured by applying the tensile force along the axis of the ligament. A versatile clamp was designed to accomplish this purpose. Fifty-seven rabbit knee specimens were tested at angles of flexion of 0”. 30” or 90”. In addition, a comparative study of 25 pairs of rabbit legs were performed, whereby loading was either along the ligament or along the tibia1 axis. Cyclic hysteresis. ultimate load, energy absorbed, and stiffness were determined. The ultimate load values for the FATC decreased with increased knee flexion for those loaded along the tibia1 axis. while no such change was detected for FATC tested along the ligament axis. Other structural properties measured followed similar trends. It is concluded that the structural properties of the rabbit FATC change minimally with knee flexion (from 0 to 90’) when loaded along the ligament axis. but decrease significantly with knee flexion when loaded along the axis of the tibia. Therefore, the data obtained in this field of study can be compared only if the direction of loading with respect to the ACL is similar. Woo SLY. Hollis JM, Roux RD. Gomez MA, Inoue M, Kleiner JB. Akeson WH. J Biomech 1987; 20: 557-63
Mechanical properties of lumbar spinal motion segments as affected by partial diic removal The changes in the three-dimensional motion behaviour of the lumbar motion segments, as affected by partial discectomy, are presented. The injured specimens, when subjected to flexion, extension, lateral bending. or axial torsional loads, showed significant increases in their major motions when compared with the corresponding intact specimen. No significant increases in the coupled motions were observed. These results suggest that it is better to excise as little of the nucleus as possible at surgery, since it may limit the increase in motion due to the injury. Goel VK, Nishiyama 11: 1008-12.
K, Weinstein
JN. Liu YK.
Spine 1986:
MA,
Hutton
on intervertebral
WC. J Bone Joint Surg 19X7;
A study of the compressive properties of lumbar vertebral traveculae: effects of tissue characteristics The compressive material properties of human lumbar vertebral travecular bone were examined and compared to in vivo and in vitro measures of bone density and to the degree of macroscopic disc degeneration. No significant differences in the material properties were found for segment level (L I-L4) or for degeneration grade (I-IV). although trabecular bone specimens from segments with slightly degenerated disks (I-II) were stronger (24%) and stiffer (16%) on the average than specimens from segments with severely degenerated discs. Significant positive logarithmic regressions were obtained, however, between the in vivo and in vitro measures of trabecular bone density and trabecular bone mechanical properties. The results indicate that in vivo mineral measurements can accurately estimate the compressive material properties of lumbar vertebral trabeculae. Hansson TH.
Keller TS. Panjabi
MM.
Spine 1987: I?: 56-62
Method and instrument for noninvasive measurements of thoracolumbar rotation An objective method of measuring thoracolumbar vertebral rotation by using a suitable compass attached to an auxiliary tool is described. The jugular notch and xiphisternum are used ventrally and the spinous process on the same horizontal planes is used dorsally as reference points for spinal rotation. The method was tested on 39 adults. The mean of intratester and intertester correlation coefficients for the measurements was 0.79 (SD 0.1 l), with no essential difference between intratester and intertester reproducibility. The results also showed that the method is of considerable validity and, thus, is a supplement to noninvasive goniometric measurements of thoracolumbar mobility in the sagittal and frontal planes. Mellin
G. Spine 1987; 12: 28-31
Shoulder antagonistic strength ratios: a comparison between college-level baseball pitchers and nonpitchers The purpose of this study was to investigate the shoulder strength ratios obtained from college-level baseball pitchers and age- and sex-matched nonpitchers. Shoulder flexionl extension and external/internal rotation strength ratios were
C/in. Biomech.
1987; 2: No 4
The effects of medullary reaming on the torsional strength of the femur
The short-term effects of chymopapain discs
The authors have investigated the effect on the torsional strength of the bone of reaming the medulla of the femur from 12 to 16mm in steps of 1 mm. Five groups of femurs. with 10 pairs in each, were tested comparatively in torsional loading and the torque required to cause fracture and the angle through which the bone had twisted at fracture were directly recorded for each pair. The results of maximum torque at failure (expressed as a proportion of the same parameter for the unreamed femur) plotted against the ratio of bone shaft diameter to reamed diameter showed a good correlation. The proportional maximum torque was found to range from 0.63 (at 12 mm) to O-36 (at 16mm) with a sharp transition between 14 and 15 mm. The drastic reduction was felt to be important for both the surgeon and the patient.
Cadaveric lumbar discs were injected with chymopapain and subjected to a series of mechanical tests over a period of up to 19 hours. Discs from the same spine injected with saline were used as controls. The results showed that chymopapain had no measurable effect on the mechanical properties of the disc apart from the increased height and stiffening caused by fluid injection. Another series of tests on isolated pieces of disc material showed that chvmopapain could reduce the size of prolapsed nuclear material by 24% in one hour and by 80% in 48 hours. It is concluded that. in the short-term. chymopapain has a negligible effect on the mechanics of a disc but it can reduce the size of any prolapsed nuclear material with which it comes in contact.
Pratt DJ, Papagiannopoulos 1987: 18: 177-9.
Dolan P, Adams 69-B: 422-8
G, Rees PH, Quinnell
R. Injury
Effects of knee flexion on the structural properties of the rabbit femur-anterior cruciate ligament-tibia complex (FATC) Many studies have been conducted to determine the biomechanical properties of the anterior cruciate ligament (ACL). The method of holding the femur-ACL-tibia complex (FATC) test specimen, the strain rate applied, the angle of knee flexion and the direction of the applied loads have an important effect on the outcome. It is felt that the tensile properties and strength of the ligament should be measured by applying the tensile force along the axis of the ligament. A versatile clamp was designed to accomplish this purpose. Fifty-seven rabbit knee specimens were tested at angles of flexion of 0”. 30” or 90”. In addition, a comparative study of 25 pairs of rabbit legs were performed, whereby loading was either along the ligament or along the tibia1 axis. Cyclic hysteresis. ultimate load, energy absorbed, and stiffness were determined. The ultimate load values for the FATC decreased with increased knee flexion for those loaded along the tibia1 axis. while no such change was detected for FATC tested along the ligament axis. Other structural properties measured followed similar trends. It is concluded that the structural properties of the rabbit FATC change minimally with knee flexion (from 0 to 90’) when loaded along the ligament axis. but decrease significantly with knee flexion when loaded along the axis of the tibia. Therefore, the data obtained in this field of study can be compared only if the direction of loading with respect to the ACL is similar. Woo SLY. Hollis JM, Roux RD. Gomez MA, Inoue M, Kleiner JB. Akeson WH. J Biomech 1987; 20: 557-63
Mechanical properties of lumbar spinal motion segments as affected by partial diic removal The changes in the three-dimensional motion behaviour of the lumbar motion segments, as affected by partial discectomy, are presented. The injured specimens, when subjected to flexion, extension, lateral bending. or axial torsional loads, showed significant increases in their major motions when compared with the corresponding intact specimen. No significant increases in the coupled motions were observed. These results suggest that it is better to excise as little of the nucleus as possible at surgery, since it may limit the increase in motion due to the injury. Goel VK, Nishiyama 11: 1008-12.
K, Weinstein
JN. Liu YK.
Spine 1986:
MA,
Hutton
on intervertebral
WC. J Bone Joint Surg 19X7;
A study of the compressive properties of lumbar vertebral traveculae: effects of tissue characteristics The compressive material properties of human lumbar vertebral travecular bone were examined and compared to in vivo and in vitro measures of bone density and to the degree of macroscopic disc degeneration. No significant differences in the material properties were found for segment level (L I-L4) or for degeneration grade (I-IV). although trabecular bone specimens from segments with slightly degenerated disks (I-II) were stronger (24%) and stiffer (16%) on the average than specimens from segments with severely degenerated discs. Significant positive logarithmic regressions were obtained, however, between the in vivo and in vitro measures of trabecular bone density and trabecular bone mechanical properties. The results indicate that in vivo mineral measurements can accurately estimate the compressive material properties of lumbar vertebral trabeculae. Hansson TH.
Keller TS. Panjabi
MM.
Spine 1987: I?: 56-62
Method and instrument for noninvasive measurements of thoracolumbar rotation An objective method of measuring thoracolumbar vertebral rotation by using a suitable compass attached to an auxiliary tool is described. The jugular notch and xiphisternum are used ventrally and the spinous process on the same horizontal planes is used dorsally as reference points for spinal rotation. The method was tested on 39 adults. The mean of intratester and intertester correlation coefficients for the measurements was 0.79 (SD 0.1 l), with no essential difference between intratester and intertester reproducibility. The results also showed that the method is of considerable validity and, thus, is a supplement to noninvasive goniometric measurements of thoracolumbar mobility in the sagittal and frontal planes. Mellin
G. Spine 1987; 12: 28-31
Shoulder antagonistic strength ratios: a comparison between college-level baseball pitchers and nonpitchers The purpose of this study was to investigate the shoulder strength ratios obtained from college-level baseball pitchers and age- and sex-matched nonpitchers. Shoulder flexionl extension and external/internal rotation strength ratios were