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Lower lateral femoral compartment proteoglycan density associates with lower knee abduction moment during walking in individuals following anterior cruciate ligament reconstruction and lateral meniscus tear: a preliminary study
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Abstracts / Osteoarthritis and Cartilage 25 (2017) S76eS444
for weeks 2, 3, and 4 (p < 0.01), and left and right percent stance times were longer than controls at week 4 (p < 0.01, p < 0.05). The MIA model showed significant decreases in stride length at week 4 (p < 0.05). In addition, the MIA model used temporally asymmetric gaits with imbalanced stance time times between the left and right limbs. These temporal abnormalities (asymmetric sequence and stance time imbalance) were also found to be significantly different from saline controls at weeks 3 and 4 (p < 0.01). Dynamic gait abnormalities were also identified in both models. These changes were most apparent in peak vertical force (PVF) (Fig. 1). Interestingly, MMT animals did not show significant differences between contralateral and ipsilateral feet. Instead, PVF dropped in both limbs over time, showing differences from control at weeks 1, 2, and 3 (p < 0.01). In contrast, differences between hind limbs were found in the MIA model at all weeks (p < 0.01).
Figure 1*: difference from indicated group, 1e3: difference within group from indicated week, f: difference compared to contralateral of the same group. Conclusions: These data show unique gait profiles developing in two common rodent OA models. Data in the MMT model indicate the rodents are ‘shuffle-stepping’, using relatively symmetric gait sequences that off-load both hind limbs. Conversely, data in the MIA model indicate an antalgic gait sequence, otherwise known as limping. Combined, these compensations were more readily apparent with the combination of dynamic and spatiotemporal data, offering a gait analysis method that is more descriptive of rodent behavior than spatiotemporal gait alone. Moreover, these data indicate that different rodent OA models do not produce the same behavioral responses and it may, therefore, be useful to target model selection based on specific aspects of OA, whether they be structural damage, the acute component of OA pain, or long-term chronic pain states. 166 LOWER LATERAL FEMORAL COMPARTMENT PROTEOGLYCAN DENSITY ASSOCIATES WITH LOWER KNEE ABDUCTION MOMENT DURING WALKING IN INDIVIDUALS FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION AND LATERAL MENISCUS TEAR: A PRELIMINARY STUDY M. Harkey, J. Spang, D. Nissman, L. Stanley, H. Davis, S. Pfeiffer, G. Kamath, A. Creighton, T. Blackburn, D. Padua, S. Marshall, J. Jordan, B. Pietrosimone. Univ. of North Carolina at Chapel Hill, Chapel Hill, NC, USA Purpose: Greater internal knee abduction moment (KAM) during walking gait is theorized to increase medial tibiofemoral joint loading and is related to disease severity and progression in individuals with medial
compartment OA. Individuals with an anterior cruciate ligament (ACLR) injury and subsequent reconstruction (ACLR) are at a high risk of developing osteoarthritis (OA). Decreased articular cartilage proteoglycan density has been quantified by greater T1rho magnetic resonance imaging (MRI) relaxation times as early as 12 months following ACLR. The high incidence of traumatic bone contusions in the lateral tibiofemoral compartment following ACL injury are associated with greater alterations in composition of the overlying cartilage; oftentimes leading to the development of lateral tibiofemoral compartment OA being more of a concern than medial compartment OA following ACLR. Additionally, lateral meniscus injuries that occur concomitantly with ACL injury may further compound the increased likelihood of lateral tibiofemoral compartment OA onset. However, it is unknown how KAM (i.e. a marker of medial compartment loading) is associated with femoral cartilage proteoglycan density (i.e. T1rho relaxation times) in individuals at risk for lateral compartment OA. Therefore, the purpose of this preliminary study is to determine if KAM limb symmetry is associated with proteoglycan density of the femoral articular cartilage in individuals who are 12months removed from ACLR with a concomitant lateral meniscus tear. Methods: Ten individuals were assessed 12 months following unilateral ACLR (40% Female, 22.2 ± 3.5 years old, 183.9 ± 12.1 cm, 82.8 ± 12.2 kg). T1rho MRI relaxation times were collected bilaterally on a Siemens Magnetom TIM Trio 3T scanner using a 4-channel Siemens large flex coil. We used a T1rho prepared 3D FLASH sequence with a 500 Hz spin lock power and five different spin lock durations (40, 30, 20,10, 0 ms). A single investigator manually segmented the lateral and medial femoral condyle articular cartilage into five regions of interest (ROI) within the sagittal plane: posterior, posterior meniscus, central, anterior meniscus and anterior ROI. Three-dimensional biomechanics were measured during walking at a self-selected speed. Peak KAM was calculated bilaterally during the first 50% of the stance phase of walking gait. T1rho and KAM of the ACLR limb were normalized to the contralateral limb to create limb symmetry indices (LSI) for each variable (T1rho_LSI ¼ ACLR T1rho / contralateral T1rho, for each subsection; KAM_LSI ¼ ACLR KAM / contralateral KAM). A T1rho_LSI > 1 indicates lower proteoglycan density in the ROI of the ACLR limb compared to the contralateral limb, while a KAM_LSI > 1 indicates increased medial compartment loading in the ACLR limb compared to the contralateral limb. Separate bivariate Pearson Product Moment correlations (r) were conducted between the KAM_LSI and T1rho_LSI for all five subsections of the lateral and medial femoral condyles. The level of significance was set a priori at P 0.05 for all analyses. Results: KAM_LSI and T1rho_LSI were not significantly associated with any of the ROIs in the medial femoral compartment. However, lower KAM_LSI (0.82 ± 0.24) was strongly associated with greater T1rho_LSI in the posterior (1.21 ± 0.16; r ¼ 0.72; p ¼ 0.018), posterior meniscus (1.21 ± 0.13; r ¼ 0.77; p ¼ 0.009) and central (1.16 ± 0.12; r ¼ 0.84; p ¼ 0.003) ROI of the lateral femoral compartment. KAM_LSI and T1rho_LSI were not significantly associated with the anterior and anterior meniscus ROI in the lateral femoral compartment or any of the ROI in the medial femoral compartment. Conclusions: While greater KAM is a common biomechanical variable thought to increase the likelihood of medial tibiofemoral compartment OA, KAM is not associated with medial femoral proteoglycan density in individuals at risk of lateral compartment OA. These results demonstrate that lower KAM may not always be a positive gait adaptation, as lesser KAM is related to lesser proteoglycan density in the lateral compartment of individuals with ACLR and lateral meniscus tear. While lower KAM does not provide direct evidence of greater lateral compartment loading, it is possible that individuals exhibiting lower KAM may be unloading their medial tibiofemoral compartment and distributing more load to the lateral tibiofemoral compartment. Future studies should investigate how internal knee adduction moment may be associated with femoral cartilage in individuals at high risk of lateral compartment OA, as this variable may be a more specific outcome measure related to lateral compartment loading. 167 HIGH FLEXION IS ASSOCIATED WITH KNEE OSTEOARTHRITIS - OF FOUR HIGH FLEXION POSTURES, FLAT FOOT SQUATTING MINIMIZES KNEE ADDUCTION MOMENTS H.C. Chong, L.M. Tennant, S.M. Acker. Univ. of Waterloo, Waterloo, ON, Canada Purpose: High knee flexion postures (where the knee flexion angle exceeds approximately 120 ) are commonly used for occupational
Abstracts / Osteoarthritis and Cartilage 25 (2017) S76eS444
for weeks 2, 3, and 4 (p < 0.01), and left and right percent stance times were longer than controls at week 4 (p < 0.01, p < 0.05). The MIA model showed significant decreases in stride length at week 4 (p < 0.05). In addition, the MIA model used temporally asymmetric gaits with imbalanced stance time times between the left and right limbs. These temporal abnormalities (asymmetric sequence and stance time imbalance) were also found to be significantly different from saline controls at weeks 3 and 4 (p < 0.01). Dynamic gait abnormalities were also identified in both models. These changes were most apparent in peak vertical force (PVF) (Fig. 1). Interestingly, MMT animals did not show significant differences between contralateral and ipsilateral feet. Instead, PVF dropped in both limbs over time, showing differences from control at weeks 1, 2, and 3 (p < 0.01). In contrast, differences between hind limbs were found in the MIA model at all weeks (p < 0.01).
Figure 1*: difference from indicated group, 1e3: difference within group from indicated week, f: difference compared to contralateral of the same group. Conclusions: These data show unique gait profiles developing in two common rodent OA models. Data in the MMT model indicate the rodents are ‘shuffle-stepping’, using relatively symmetric gait sequences that off-load both hind limbs. Conversely, data in the MIA model indicate an antalgic gait sequence, otherwise known as limping. Combined, these compensations were more readily apparent with the combination of dynamic and spatiotemporal data, offering a gait analysis method that is more descriptive of rodent behavior than spatiotemporal gait alone. Moreover, these data indicate that different rodent OA models do not produce the same behavioral responses and it may, therefore, be useful to target model selection based on specific aspects of OA, whether they be structural damage, the acute component of OA pain, or long-term chronic pain states. 166 LOWER LATERAL FEMORAL COMPARTMENT PROTEOGLYCAN DENSITY ASSOCIATES WITH LOWER KNEE ABDUCTION MOMENT DURING WALKING IN INDIVIDUALS FOLLOWING ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION AND LATERAL MENISCUS TEAR: A PRELIMINARY STUDY M. Harkey, J. Spang, D. Nissman, L. Stanley, H. Davis, S. Pfeiffer, G. Kamath, A. Creighton, T. Blackburn, D. Padua, S. Marshall, J. Jordan, B. Pietrosimone. Univ. of North Carolina at Chapel Hill, Chapel Hill, NC, USA Purpose: Greater internal knee abduction moment (KAM) during walking gait is theorized to increase medial tibiofemoral joint loading and is related to disease severity and progression in individuals with medial
compartment OA. Individuals with an anterior cruciate ligament (ACLR) injury and subsequent reconstruction (ACLR) are at a high risk of developing osteoarthritis (OA). Decreased articular cartilage proteoglycan density has been quantified by greater T1rho magnetic resonance imaging (MRI) relaxation times as early as 12 months following ACLR. The high incidence of traumatic bone contusions in the lateral tibiofemoral compartment following ACL injury are associated with greater alterations in composition of the overlying cartilage; oftentimes leading to the development of lateral tibiofemoral compartment OA being more of a concern than medial compartment OA following ACLR. Additionally, lateral meniscus injuries that occur concomitantly with ACL injury may further compound the increased likelihood of lateral tibiofemoral compartment OA onset. However, it is unknown how KAM (i.e. a marker of medial compartment loading) is associated with femoral cartilage proteoglycan density (i.e. T1rho relaxation times) in individuals at risk for lateral compartment OA. Therefore, the purpose of this preliminary study is to determine if KAM limb symmetry is associated with proteoglycan density of the femoral articular cartilage in individuals who are 12months removed from ACLR with a concomitant lateral meniscus tear. Methods: Ten individuals were assessed 12 months following unilateral ACLR (40% Female, 22.2 ± 3.5 years old, 183.9 ± 12.1 cm, 82.8 ± 12.2 kg). T1rho MRI relaxation times were collected bilaterally on a Siemens Magnetom TIM Trio 3T scanner using a 4-channel Siemens large flex coil. We used a T1rho prepared 3D FLASH sequence with a 500 Hz spin lock power and five different spin lock durations (40, 30, 20,10, 0 ms). A single investigator manually segmented the lateral and medial femoral condyle articular cartilage into five regions of interest (ROI) within the sagittal plane: posterior, posterior meniscus, central, anterior meniscus and anterior ROI. Three-dimensional biomechanics were measured during walking at a self-selected speed. Peak KAM was calculated bilaterally during the first 50% of the stance phase of walking gait. T1rho and KAM of the ACLR limb were normalized to the contralateral limb to create limb symmetry indices (LSI) for each variable (T1rho_LSI ¼ ACLR T1rho / contralateral T1rho, for each subsection; KAM_LSI ¼ ACLR KAM / contralateral KAM). A T1rho_LSI > 1 indicates lower proteoglycan density in the ROI of the ACLR limb compared to the contralateral limb, while a KAM_LSI > 1 indicates increased medial compartment loading in the ACLR limb compared to the contralateral limb. Separate bivariate Pearson Product Moment correlations (r) were conducted between the KAM_LSI and T1rho_LSI for all five subsections of the lateral and medial femoral condyles. The level of significance was set a priori at P 0.05 for all analyses. Results: KAM_LSI and T1rho_LSI were not significantly associated with any of the ROIs in the medial femoral compartment. However, lower KAM_LSI (0.82 ± 0.24) was strongly associated with greater T1rho_LSI in the posterior (1.21 ± 0.16; r ¼ 0.72; p ¼ 0.018), posterior meniscus (1.21 ± 0.13; r ¼ 0.77; p ¼ 0.009) and central (1.16 ± 0.12; r ¼ 0.84; p ¼ 0.003) ROI of the lateral femoral compartment. KAM_LSI and T1rho_LSI were not significantly associated with the anterior and anterior meniscus ROI in the lateral femoral compartment or any of the ROI in the medial femoral compartment. Conclusions: While greater KAM is a common biomechanical variable thought to increase the likelihood of medial tibiofemoral compartment OA, KAM is not associated with medial femoral proteoglycan density in individuals at risk of lateral compartment OA. These results demonstrate that lower KAM may not always be a positive gait adaptation, as lesser KAM is related to lesser proteoglycan density in the lateral compartment of individuals with ACLR and lateral meniscus tear. While lower KAM does not provide direct evidence of greater lateral compartment loading, it is possible that individuals exhibiting lower KAM may be unloading their medial tibiofemoral compartment and distributing more load to the lateral tibiofemoral compartment. Future studies should investigate how internal knee adduction moment may be associated with femoral cartilage in individuals at high risk of lateral compartment OA, as this variable may be a more specific outcome measure related to lateral compartment loading. 167 HIGH FLEXION IS ASSOCIATED WITH KNEE OSTEOARTHRITIS - OF FOUR HIGH FLEXION POSTURES, FLAT FOOT SQUATTING MINIMIZES KNEE ADDUCTION MOMENTS H.C. Chong, L.M. Tennant, S.M. Acker. Univ. of Waterloo, Waterloo, ON, Canada Purpose: High knee flexion postures (where the knee flexion angle exceeds approximately 120 ) are commonly used for occupational