Mack Gardner-Morse - Academia.edu (original) (raw)

Papers by Mack Gardner-Morse

Osteoarthritis Imaging, Jul 1, 2023

Journal of Orthopaedic Research, Sep 7, 2018

Biomechanical properties of the disc provide both flexibility and shock absorption. We hypothesis... more Biomechanical properties of the disc provide both flexibility and shock absorption. We hypothesised that frequency-dependent effects in shear and torsion deformations in which intrinsic viscoelasticity (solid phase) predominates would differ from compression and bending, in which fluid flow-mediated poroelasticity is also present. Disc-vertebra-disc preparations (N=8) from human lumbar spines were subjected to each of three displacements and three rotations (6 degrees of freedom - DOF) at each of four frequencies (0.001, 0.01, 0.1, and 1 Hz) after equilibration overnight under a 0.4 MPa preload in a bath of PBS at 37C with protease inhibitors. The forces and torques were recorded along with the applied translation or rotation. The stiffness (force/displacement or torque/rotation) and the phase angle (between each force and displacement) were calculated for each degree of freedom from recorded data. The stiffness significantly increased linearly with the log-frequency in most DOF (P 0.055). The increases over the four decades of frequency were 28%, 23% and 25% for antero-posterior (AP) shear, lateral shear and torsion respectively, and were 53%, 33% and 36% for compression, lateral bending and flexion. The phase angle (a measure of energy absorption) significantly decreased overall with increasing frequency in all DOF (P 0.057). The dynamic effects (stiffness increase, and phase angle decrease with frequency) were consistently greater for deformation modes in which fluid flow effects are thought to be greater. Both the solid phase viscoelasticity and the fluid phase poroelasticity of the tissue appear to contribute to the disc stiffness and energy absorption, although these differences become more apparent at 1 Hz compared to the slower frequencies.

European Journal of Orthopaedic Surgery and Traumatology, Jun 27, 2022

Journal of Orthopaedic Research, 2019

ABSTRACTCombined injury to the anterior cruciate ligament (ACL) and meniscus is associated with e... more ABSTRACTCombined injury to the anterior cruciate ligament (ACL) and meniscus is associated with earlier onset and increased rates of post‐traumatic osteoarthritis compared with isolated ACL injury. However, little is known about the initial changes in joint structure associated with these different types of trauma. We hypothesized that trauma to the ACL and lateral meniscus has an immediate effect on morphometry of the articular cartilage and meniscus about the entire tibial plateau that is more pronounced than an ACL tear without meniscus injury. Subjects underwent magnetic resonance imaging scanning soon after injury and prior to surgery. Those that suffered injury to the ACL and lateral meniscus underwent changes in the lateral compartment (increases in the posterior–inferior directed slopes of the articular cartilage surface, and the wedge angle of the posterior horn of the meniscus) and medial compartment (the cartilage‐to‐bone height decreased in the region located under the p...

Journal of Orthopaedic Research, 2019

ABSTRACTJoint space width (JSW), measured as the distance between the femoral and tibial subchond... more ABSTRACTJoint space width (JSW), measured as the distance between the femoral and tibial subchondral bone margins on two‐dimensional weight‐bearing radiographs, is the initial imaging modality used in clinical settings to diagnose and evaluate the progression of osteoarthritis (OA). While, JSW is the only structural outcome approved by the FDA for studying the treatment of this disease in phase III clinical trials, recent reports suggest that magnetic resonance imaging (MRI)‐based measurements of OA changes are superior due to increased sensitivity and specificity to the structural changes associated with progression of this disease. In the current study, we examined the relationship between radiographic JSW and MRI‐derived articular cartilage thickness in subjects 4 years post anterior cruciate ligament reconstruction (ACLR) who were at increased risk for the onset and early progression of post‐traumatic OA, and in uninjured subjects with normal knees (Control). In both ACLR and Co...

Osteoarthritis and Cartilage, 2017

Osteoarthritis and Cartilage, 2011

tibial subregions. WORMS score ranges from 0-6 where 6 represents cartilage loss to bone in 75% o... more tibial subregions. WORMS score ranges from 0-6 where 6 represents cartilage loss to bone in 75% of region. Analysis was performed for the compartment showing bone-on-bone appearance ("index") on radiograph and also for the other TF compartment of the same knee. Hoffa-synovitis and effusion-synovitis were assessed for the whole knee. Changes in scores at follow-up were noted for each feature. For cartilage and BML, within-grade changes were also recorded. Results: 67 knees from 63 subjects were included (51% women, 84% White, mean age 65.1±8.6 years, mean BMI 30.2±5.2 kg/m2). At baseline, in the index TF compartment, all knees showed severe cartilage loss (max WORMS score from 5 subregions was 5 in 1 knee and 6 in 66 knees), 54 knees (80%) showed moderate to large BMLs (max WORMS score 2 or 3), and 62 knees (94%) had severe meniscal lesions (i.e. displaced tear or maceration). In the other TF compartment, 12 knees (18%) had severe cartilage loss, but 47 (71%) had no BML and 57 (97%) had no meniscal damage. 39 knees (58%) had moderate to severe effusion-synovitis, 56 knees (86%) had mild or moderate Hoffa-synovitis. Longitudinally, 22 index compartments (35%) showed an increase in the sum of cartilage scores from all subregions, and 2 (3%) showed increase in the maximum cartilage score. In the other TF compartment, 22% showed an increase in the sum score for cartilage damage, while 15% showed increase in maximum score. For BMLs in the index TF compartment, 19 knees (31%) showed an increase in maximum score and 11 (18%) showed a decrease. Fluctuation of BMLs was also seen in the other TF compartment, but to a lesser extent. Meniscal status mostly remained the same in the index (98%) and other TF (95%) compartments. Effusion-synovitis worsened in 15 knees (27%) and improved in 2 knees (4%). Hoffa-synovitis worsened in 6 knees (11%) and improved in 2 knees (4%). Conclusion: In KL4 knees, MRI detected progression of cartilage loss, effusion-synovitis, and Hoffa-synovitis, and fluctuation in size of BMLs. Meniscal damage remained stable. Our findings support the idea that disease progression still occurs in KL4 knees. KL4 knees can be a potential target for assessing therapeutic interventions and should not necessarily be excluded from studies evaluating therapeutic response.

The American journal of sports medicine, Jan 27, 2014

The morphometric characteristics of the anterior cruciate ligament (ACL) and the femoral intercon... more The morphometric characteristics of the anterior cruciate ligament (ACL) and the femoral intercondylar notch within which it resides have been implicated as risk factors for injuries to this important stabilizer of the knee. Prior research has produced equivocal results with differing methodologies, and consequently, it is unclear how these characteristics affect the injury risk in male and female patients. The morphometric characteristics of the ACL and femoral intercondylar notch are individually and independently associated with the risk of suffering a noncontact ACL injury, and these relationships are different in male and female patients. Case-control study; Level of evidence, 3. Magnetic resonance imaging scans of the bilateral knees were obtained on 88 case-control pairs (27 male, 61 female) matched for age, sex, and participation on the same sports team. Patients had suffered a grade III, first-time, noncontact ACL tear. The femoral notch width at 4 locations, the thickness ...

Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 2014

Tibial plateau subchondral bone geometry has been associated with the risk of sustaining a non-co... more Tibial plateau subchondral bone geometry has been associated with the risk of sustaining a non-contact ACL injury; however, little is known regarding the influence of the meniscus and articular cartilage interface geometry on risk. We hypothesized that geometries of the tibial plateau articular cartilage surface and meniscus were individually associated with the risk of non-contact ACL injury. In addition, we hypothesized that the associations were independent of the underlying subchondral bone geometry. MRI scans were acquired on 88 subjects that suffered non-contact ACL injuries (27 males, 61 females) and 88 matched control subjects that were selected from the injured subject's teammates and were thus matched on sex, sport, level of play, and exposure to risk of injury. Multivariate analysis of the female data revealed that increased posterior-inferior directed slope of the middle articular cartilage region and decreased height of the posterior horn of the meniscus in the late...

The American journal of sports medicine, Jan 12, 2015

Knee joint geometry has been associated with risk of suffering an anterior cruciate ligament (ACL... more Knee joint geometry has been associated with risk of suffering an anterior cruciate ligament (ACL) injury; however, few studies have utilized multivariate analysis to investigate how different aspects of knee joint geometry combine to influence ACL injury risk. Combinations of knee geometry measurements are more highly associated with the risk of suffering a noncontact ACL injury than individual measurements, and the most predictive combinations of measurements are different for males and females. Case-control study; Level of evidence, 3. A total of 88 first-time, noncontact, grade III ACL-injured subjects and 88 uninjured matched-control subjects were recruited, and magnetic resonance imaging data were acquired. The geometry of the tibial plateau subchondral bone, articular cartilage, and meniscus; geometry of the tibial spines; and size of the femoral intercondylar notch and ACL were measured. Multivariate conditional logistic regression was used to develop risk models for ACL inj...

Journal of Orthopaedic Research, 2013

ABSTRACTThe purpose of this study was to determine if geometry of the articular surfaces of the t... more ABSTRACTThe purpose of this study was to determine if geometry of the articular surfaces of the tibial plateau is associated with non‐contact anterior cruciate ligament (ACL) injury. This was a longitudinal cohort study with a nested case–control analysis. Seventy‐eight subjects who suffered a non‐contact ACL tear and a corresponding number of controls matched by age, sex, and sport underwent 3 T MRI of both knees. Surface geometry of the tibial articular cartilage was characterized with polynomial equations and comparisons were made between knees on the same person and between ACL‐injured and control subjects. There was no difference in surface geometry between the knees of the control subjects. In contrast, there were significant differences in the surface geometry between the injured and normal knees of the ACL‐injured subjects, suggesting that the ACL injury changed the cartilage surface profile. Therefore, comparisons were made between the uninjured knees of the ACL‐injured sub...

The American Journal of Sports Medicine, 2019

Background: The incidence of contralateral anterior cruciate ligament (CACL) injuries after recov... more Background: The incidence of contralateral anterior cruciate ligament (CACL) injuries after recovery from a first-time anterior cruciate ligament (ACL) disruption is high in women; however, little is known about the risk factors associated with this trauma. Hypothesis: Patient characteristics, strength, anatomic alignment, and neuromuscular characteristics of the contralateral uninjured leg at the time of the first ACL trauma are associated with risk of subsequent CACL injury, and these risk factors are distinct from those for a first-time ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: Sixty-one women who suffered a first-time noncontact ACL injury while participating in high school or college sports and underwent measurement of potential risk factors on their contralateral limb soon after the initial ACL injury and before reconstruction were followed until either a CACL injury or an ACL graft injury occurred, or until the last date of contact. Results:...

Journal of Orthopaedic Research, 2021

Anterior cruciate ligament injury and reconstruction (ACLR) affects articular cartilage thickness... more Anterior cruciate ligament injury and reconstruction (ACLR) affects articular cartilage thickness profiles about the tibial, femoral, and patellar surfaces; however, it's unclear whether the magnitudes of change in cartilage thickness, as well as the locations and areas over which these changes occur, differ between males and females. This is important to consider as differences exist between the sexes with regard to knee biomechanics, patellofemoral pain, and anatomic alignment, which influence risk of an index and repeated injury. Subjects underwent ACLR with a bone‐patella tendon‐bone autograft. At 4‐year follow‐up, they had asymptomatic knees; however, significant ACL injured‐to‐contralateral normal knee differences in articular cartilage thickness values were observed. Both thickening and thinning of cartilage occurred about the tibiofemoral and patellofemoral joints, relative to matched control subjects with normal knees. Further, the location of the areas and magnitudes of thickening and thinning were different between females and males. Thickening (swelling) of articular cartilage is an early finding associated with the onset of posttraumatic osteoarthritis (PTOA). Therefore, the increases in cartilage thickness that were observed in this cohort may represent early signs of the onset of PTOA that occur prior to the patient developing symptoms and radiographic evidence of this disease. The different locations of areas that underwent a change in cartilage thicknesses between males and females suggest that each sex responds differently to knee ligament trauma, reconstruction, rehabilitation, and return to activity, and indicates that sex‐specific analysis should be utilized in studies of PTOA.

Journal of Biomechanics, 2016

Data from two experimental studies with eight specimens each of spinal motion segments and/or int... more Data from two experimental studies with eight specimens each of spinal motion segments and/or intervertebral discs are presented in a form that can be used for comparison with finite element model predictions. The data include the effect of compressive preload (0, 250 and 500 N) with quasistatic cyclic loading (0.0115 Hz) and the effect of loading frequency (1, 0.1, 0.01 and 0.001 Hz) with a physiological compressive preload (mean 642 N). Specimens were tested with displacements in each of six degrees of freedom (three translations and three rotations) about defined anatomical axes. The three forces and three moments in the corresponding axis system were recorded during each test. Linearized stiffness matrices were calculated that could be used in multi-segmental biomechanical models of the spine and these matrices were analyzed to determine whether off-diagonal terms and symmetry assumptions should be included. These databases of lumbar spinal mechanical behavior under physiological conditions quantify behaviors that should be present in finite element model simulations. The addition of more specimens to identify sources of variability associated with physical dimensions, degeneration, and other variables would be beneficial. Supplementary data provide the recorded data and Matlab® codes for reading files. Linearized stiffness matrices derived from the tests at different preloads revealed few significant unexpected off-diagonal terms and little evidence of significant matrix asymmetry.

The six-degrees-of-freedom elastic behavior of spinal motion segments can be approximated by a st... more The six-degrees-of-freedom elastic behavior of spinal motion segments can be approximated by a stiffness matrix. Amethod is described to measure this stiffness matrix directly with the motion segment held under physiological conditions of axial preload and in an isotonic fluid bath by measuring the forces and moments associated with each of the six orthogonal translations and rotations. The stiffness matrix was obtained from the load-displacement measurements by linear least squares assuming a symmetric matrix. Results from a pig lumbar spinal motion segment in an isotonic bath, with and without a 500 N axial preload, showed a large stiffening effect with axial preload. r 2002 Elsevier Science Ltd. All rights reserved.

Journal of Structural Engineering, 1994

Osteoarthritis Imaging, Jul 1, 2023

Journal of Orthopaedic Research, Sep 7, 2018

Biomechanical properties of the disc provide both flexibility and shock absorption. We hypothesis... more Biomechanical properties of the disc provide both flexibility and shock absorption. We hypothesised that frequency-dependent effects in shear and torsion deformations in which intrinsic viscoelasticity (solid phase) predominates would differ from compression and bending, in which fluid flow-mediated poroelasticity is also present. Disc-vertebra-disc preparations (N=8) from human lumbar spines were subjected to each of three displacements and three rotations (6 degrees of freedom - DOF) at each of four frequencies (0.001, 0.01, 0.1, and 1 Hz) after equilibration overnight under a 0.4 MPa preload in a bath of PBS at 37C with protease inhibitors. The forces and torques were recorded along with the applied translation or rotation. The stiffness (force/displacement or torque/rotation) and the phase angle (between each force and displacement) were calculated for each degree of freedom from recorded data. The stiffness significantly increased linearly with the log-frequency in most DOF (P 0.055). The increases over the four decades of frequency were 28%, 23% and 25% for antero-posterior (AP) shear, lateral shear and torsion respectively, and were 53%, 33% and 36% for compression, lateral bending and flexion. The phase angle (a measure of energy absorption) significantly decreased overall with increasing frequency in all DOF (P 0.057). The dynamic effects (stiffness increase, and phase angle decrease with frequency) were consistently greater for deformation modes in which fluid flow effects are thought to be greater. Both the solid phase viscoelasticity and the fluid phase poroelasticity of the tissue appear to contribute to the disc stiffness and energy absorption, although these differences become more apparent at 1 Hz compared to the slower frequencies.

European Journal of Orthopaedic Surgery and Traumatology, Jun 27, 2022

Journal of Orthopaedic Research, 2019

ABSTRACTCombined injury to the anterior cruciate ligament (ACL) and meniscus is associated with e... more ABSTRACTCombined injury to the anterior cruciate ligament (ACL) and meniscus is associated with earlier onset and increased rates of post‐traumatic osteoarthritis compared with isolated ACL injury. However, little is known about the initial changes in joint structure associated with these different types of trauma. We hypothesized that trauma to the ACL and lateral meniscus has an immediate effect on morphometry of the articular cartilage and meniscus about the entire tibial plateau that is more pronounced than an ACL tear without meniscus injury. Subjects underwent magnetic resonance imaging scanning soon after injury and prior to surgery. Those that suffered injury to the ACL and lateral meniscus underwent changes in the lateral compartment (increases in the posterior–inferior directed slopes of the articular cartilage surface, and the wedge angle of the posterior horn of the meniscus) and medial compartment (the cartilage‐to‐bone height decreased in the region located under the p...

Journal of Orthopaedic Research, 2019

ABSTRACTJoint space width (JSW), measured as the distance between the femoral and tibial subchond... more ABSTRACTJoint space width (JSW), measured as the distance between the femoral and tibial subchondral bone margins on two‐dimensional weight‐bearing radiographs, is the initial imaging modality used in clinical settings to diagnose and evaluate the progression of osteoarthritis (OA). While, JSW is the only structural outcome approved by the FDA for studying the treatment of this disease in phase III clinical trials, recent reports suggest that magnetic resonance imaging (MRI)‐based measurements of OA changes are superior due to increased sensitivity and specificity to the structural changes associated with progression of this disease. In the current study, we examined the relationship between radiographic JSW and MRI‐derived articular cartilage thickness in subjects 4 years post anterior cruciate ligament reconstruction (ACLR) who were at increased risk for the onset and early progression of post‐traumatic OA, and in uninjured subjects with normal knees (Control). In both ACLR and Co...

Osteoarthritis and Cartilage, 2017

Osteoarthritis and Cartilage, 2011

tibial subregions. WORMS score ranges from 0-6 where 6 represents cartilage loss to bone in 75% o... more tibial subregions. WORMS score ranges from 0-6 where 6 represents cartilage loss to bone in 75% of region. Analysis was performed for the compartment showing bone-on-bone appearance ("index") on radiograph and also for the other TF compartment of the same knee. Hoffa-synovitis and effusion-synovitis were assessed for the whole knee. Changes in scores at follow-up were noted for each feature. For cartilage and BML, within-grade changes were also recorded. Results: 67 knees from 63 subjects were included (51% women, 84% White, mean age 65.1±8.6 years, mean BMI 30.2±5.2 kg/m2). At baseline, in the index TF compartment, all knees showed severe cartilage loss (max WORMS score from 5 subregions was 5 in 1 knee and 6 in 66 knees), 54 knees (80%) showed moderate to large BMLs (max WORMS score 2 or 3), and 62 knees (94%) had severe meniscal lesions (i.e. displaced tear or maceration). In the other TF compartment, 12 knees (18%) had severe cartilage loss, but 47 (71%) had no BML and 57 (97%) had no meniscal damage. 39 knees (58%) had moderate to severe effusion-synovitis, 56 knees (86%) had mild or moderate Hoffa-synovitis. Longitudinally, 22 index compartments (35%) showed an increase in the sum of cartilage scores from all subregions, and 2 (3%) showed increase in the maximum cartilage score. In the other TF compartment, 22% showed an increase in the sum score for cartilage damage, while 15% showed increase in maximum score. For BMLs in the index TF compartment, 19 knees (31%) showed an increase in maximum score and 11 (18%) showed a decrease. Fluctuation of BMLs was also seen in the other TF compartment, but to a lesser extent. Meniscal status mostly remained the same in the index (98%) and other TF (95%) compartments. Effusion-synovitis worsened in 15 knees (27%) and improved in 2 knees (4%). Hoffa-synovitis worsened in 6 knees (11%) and improved in 2 knees (4%). Conclusion: In KL4 knees, MRI detected progression of cartilage loss, effusion-synovitis, and Hoffa-synovitis, and fluctuation in size of BMLs. Meniscal damage remained stable. Our findings support the idea that disease progression still occurs in KL4 knees. KL4 knees can be a potential target for assessing therapeutic interventions and should not necessarily be excluded from studies evaluating therapeutic response.

The American journal of sports medicine, Jan 27, 2014

The morphometric characteristics of the anterior cruciate ligament (ACL) and the femoral intercon... more The morphometric characteristics of the anterior cruciate ligament (ACL) and the femoral intercondylar notch within which it resides have been implicated as risk factors for injuries to this important stabilizer of the knee. Prior research has produced equivocal results with differing methodologies, and consequently, it is unclear how these characteristics affect the injury risk in male and female patients. The morphometric characteristics of the ACL and femoral intercondylar notch are individually and independently associated with the risk of suffering a noncontact ACL injury, and these relationships are different in male and female patients. Case-control study; Level of evidence, 3. Magnetic resonance imaging scans of the bilateral knees were obtained on 88 case-control pairs (27 male, 61 female) matched for age, sex, and participation on the same sports team. Patients had suffered a grade III, first-time, noncontact ACL tear. The femoral notch width at 4 locations, the thickness ...

Journal of orthopaedic research : official publication of the Orthopaedic Research Society, 2014

Tibial plateau subchondral bone geometry has been associated with the risk of sustaining a non-co... more Tibial plateau subchondral bone geometry has been associated with the risk of sustaining a non-contact ACL injury; however, little is known regarding the influence of the meniscus and articular cartilage interface geometry on risk. We hypothesized that geometries of the tibial plateau articular cartilage surface and meniscus were individually associated with the risk of non-contact ACL injury. In addition, we hypothesized that the associations were independent of the underlying subchondral bone geometry. MRI scans were acquired on 88 subjects that suffered non-contact ACL injuries (27 males, 61 females) and 88 matched control subjects that were selected from the injured subject's teammates and were thus matched on sex, sport, level of play, and exposure to risk of injury. Multivariate analysis of the female data revealed that increased posterior-inferior directed slope of the middle articular cartilage region and decreased height of the posterior horn of the meniscus in the late...

The American journal of sports medicine, Jan 12, 2015

Knee joint geometry has been associated with risk of suffering an anterior cruciate ligament (ACL... more Knee joint geometry has been associated with risk of suffering an anterior cruciate ligament (ACL) injury; however, few studies have utilized multivariate analysis to investigate how different aspects of knee joint geometry combine to influence ACL injury risk. Combinations of knee geometry measurements are more highly associated with the risk of suffering a noncontact ACL injury than individual measurements, and the most predictive combinations of measurements are different for males and females. Case-control study; Level of evidence, 3. A total of 88 first-time, noncontact, grade III ACL-injured subjects and 88 uninjured matched-control subjects were recruited, and magnetic resonance imaging data were acquired. The geometry of the tibial plateau subchondral bone, articular cartilage, and meniscus; geometry of the tibial spines; and size of the femoral intercondylar notch and ACL were measured. Multivariate conditional logistic regression was used to develop risk models for ACL inj...

Journal of Orthopaedic Research, 2013

ABSTRACTThe purpose of this study was to determine if geometry of the articular surfaces of the t... more ABSTRACTThe purpose of this study was to determine if geometry of the articular surfaces of the tibial plateau is associated with non‐contact anterior cruciate ligament (ACL) injury. This was a longitudinal cohort study with a nested case–control analysis. Seventy‐eight subjects who suffered a non‐contact ACL tear and a corresponding number of controls matched by age, sex, and sport underwent 3 T MRI of both knees. Surface geometry of the tibial articular cartilage was characterized with polynomial equations and comparisons were made between knees on the same person and between ACL‐injured and control subjects. There was no difference in surface geometry between the knees of the control subjects. In contrast, there were significant differences in the surface geometry between the injured and normal knees of the ACL‐injured subjects, suggesting that the ACL injury changed the cartilage surface profile. Therefore, comparisons were made between the uninjured knees of the ACL‐injured sub...

The American Journal of Sports Medicine, 2019

Background: The incidence of contralateral anterior cruciate ligament (CACL) injuries after recov... more Background: The incidence of contralateral anterior cruciate ligament (CACL) injuries after recovery from a first-time anterior cruciate ligament (ACL) disruption is high in women; however, little is known about the risk factors associated with this trauma. Hypothesis: Patient characteristics, strength, anatomic alignment, and neuromuscular characteristics of the contralateral uninjured leg at the time of the first ACL trauma are associated with risk of subsequent CACL injury, and these risk factors are distinct from those for a first-time ACL injury. Study Design: Case-control study; Level of evidence, 3. Methods: Sixty-one women who suffered a first-time noncontact ACL injury while participating in high school or college sports and underwent measurement of potential risk factors on their contralateral limb soon after the initial ACL injury and before reconstruction were followed until either a CACL injury or an ACL graft injury occurred, or until the last date of contact. Results:...

Journal of Orthopaedic Research, 2021

Anterior cruciate ligament injury and reconstruction (ACLR) affects articular cartilage thickness... more Anterior cruciate ligament injury and reconstruction (ACLR) affects articular cartilage thickness profiles about the tibial, femoral, and patellar surfaces; however, it's unclear whether the magnitudes of change in cartilage thickness, as well as the locations and areas over which these changes occur, differ between males and females. This is important to consider as differences exist between the sexes with regard to knee biomechanics, patellofemoral pain, and anatomic alignment, which influence risk of an index and repeated injury. Subjects underwent ACLR with a bone‐patella tendon‐bone autograft. At 4‐year follow‐up, they had asymptomatic knees; however, significant ACL injured‐to‐contralateral normal knee differences in articular cartilage thickness values were observed. Both thickening and thinning of cartilage occurred about the tibiofemoral and patellofemoral joints, relative to matched control subjects with normal knees. Further, the location of the areas and magnitudes of thickening and thinning were different between females and males. Thickening (swelling) of articular cartilage is an early finding associated with the onset of posttraumatic osteoarthritis (PTOA). Therefore, the increases in cartilage thickness that were observed in this cohort may represent early signs of the onset of PTOA that occur prior to the patient developing symptoms and radiographic evidence of this disease. The different locations of areas that underwent a change in cartilage thicknesses between males and females suggest that each sex responds differently to knee ligament trauma, reconstruction, rehabilitation, and return to activity, and indicates that sex‐specific analysis should be utilized in studies of PTOA.

Journal of Biomechanics, 2016

Data from two experimental studies with eight specimens each of spinal motion segments and/or int... more Data from two experimental studies with eight specimens each of spinal motion segments and/or intervertebral discs are presented in a form that can be used for comparison with finite element model predictions. The data include the effect of compressive preload (0, 250 and 500 N) with quasistatic cyclic loading (0.0115 Hz) and the effect of loading frequency (1, 0.1, 0.01 and 0.001 Hz) with a physiological compressive preload (mean 642 N). Specimens were tested with displacements in each of six degrees of freedom (three translations and three rotations) about defined anatomical axes. The three forces and three moments in the corresponding axis system were recorded during each test. Linearized stiffness matrices were calculated that could be used in multi-segmental biomechanical models of the spine and these matrices were analyzed to determine whether off-diagonal terms and symmetry assumptions should be included. These databases of lumbar spinal mechanical behavior under physiological conditions quantify behaviors that should be present in finite element model simulations. The addition of more specimens to identify sources of variability associated with physical dimensions, degeneration, and other variables would be beneficial. Supplementary data provide the recorded data and Matlab® codes for reading files. Linearized stiffness matrices derived from the tests at different preloads revealed few significant unexpected off-diagonal terms and little evidence of significant matrix asymmetry.

The six-degrees-of-freedom elastic behavior of spinal motion segments can be approximated by a st... more The six-degrees-of-freedom elastic behavior of spinal motion segments can be approximated by a stiffness matrix. Amethod is described to measure this stiffness matrix directly with the motion segment held under physiological conditions of axial preload and in an isotonic fluid bath by measuring the forces and moments associated with each of the six orthogonal translations and rotations. The stiffness matrix was obtained from the load-displacement measurements by linear least squares assuming a symmetric matrix. Results from a pig lumbar spinal motion segment in an isotonic bath, with and without a 500 N axial preload, showed a large stiffening effect with axial preload. r 2002 Elsevier Science Ltd. All rights reserved.

Journal of Structural Engineering, 1994