Publications by authors named "Ashutosh Khandha"

17 Publications

  • Page 1 of 1

Knee cartilage T relaxation times 3 months after ACL reconstruction are associated with knee gait variables linked to knee osteoarthritis.

J Orthop Res 2021 Mar 30. Epub 2021 Mar 30.

Department of Mechanical Engineering, University of Delaware, Newark, Delaware, USA.

Osteoarthritis development after ACL reconstruction (ACLR) is not well understood. Investigators have examined associations between knee biomechanical alterations and quantitative MRI (qMRI) variables, reflective of cartilage health, 12-60 months following ACLR; however, none have done so early after surgery. As part of an exploratory study, 45 individuals (age, 23 ± 7 years) underwent motion analysis during walking and qMRI 3 months after ACLR. For each limb, peak knee adduction moment (pKAM) and peak knee flexion moment (pKFM) were determined using inverse dynamics and peak medial compartment force was calculated using a neuromusculoskeletal model. T relaxation times in the medial compartment and linear regressions were used to determine the associations between gait variables and deep and superficial cartilage T relaxation times in six regions. pKAM was positively associated with deep layer T relaxation times within the femoral central and posterior regions when examined in the involved limb and from an interlimb difference perspective (involved limb - uninvolved limb). After adjusting for age, the association between interlimb difference of pKAM and interlimb difference of deep layer T relaxation times in the tibial central region became significant (p = .043). Interlimb difference of pKFM was negatively associated with interlimb difference of deep layer T relaxation times within the femoral central and posterior regions. These associations suggest that degenerative pathways leading to osteoarthritis may be detectable as early as 3 months after reconstruction. Preventative therapeutic techniques may need to be employed early in the rehabilitation process to prevent cartilage degradation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.25043DOI Listing
March 2021

Sex and mechanism of injury influence knee joint loading symmetry during gait 6 months after ACLR.

J Orthop Res 2021 05 13;39(5):1123-1132. Epub 2020 Aug 13.

Department of Physical Therapy, University of Delaware, Newark, Delaware.

Early-onset knee osteoarthritis (OA) is associated with gait asymmetries after anterior cruciate ligament reconstruction (ACLR). Women have higher risks of sustaining non-contact injuries, and are more likely to present with aberrant movement patterns associated with the mechanism of injury (MOI). We hypothesized that sex and MOI would influence gait after ACLR. Seventy participants, grouped by sex and MOI, completed biomechanical testing during over-ground walking when they had full knee range of motion, trace or less knee effusion, greater than 80% quadriceps strength limb symmetry index, ability to hop on each leg without pain, and initiated running. Bilateral knee kinetics, kinematics, and joint contact forces were compared using mixed-model analysis of variance (α = .05). There was a three-way interaction effect of sex × MOI × limb for peak medial compartment contact force (P = .002), our primary outcome measure previously associated with OA development. Men with non-contact injuries walked with asymmetry characterized by underloading of the involved limb. Men with contact injuries walked with the most symmetrical loading. In women, no clear pattern emerged based on MOI. Targeting, and possibly prioritizing interventions for athletes who present with gait asymmetries after ACLR based on sex and MOI, may be necessary to optimize outcomes. Statement of Clinical Significance: Sex and MOI may influence walking mechanics, and could be considered in future interventions to target gait symmetry, as a response to interventions may vary based on differences in sex and MOI.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.24822DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7864984PMC
May 2021

Operative and nonoperative management of anterior cruciate ligament injury: Differences in gait biomechanics at 5 years.

J Orthop Res 2020 12 20;38(12):2675-2684. Epub 2020 Mar 20.

Biomechanics and Movement Science Program, University of Delaware, Newark, Delaware.

Gait biomechanics after anterior cruciate ligament (ACL) injury are associated with functional outcomes and the development of posttraumatic knee osteoarthritis. However, biomechanical outcomes between patients treated nonoperatively compared with operatively are not well understood. The primary purpose of this study was to compare knee joint contact forces, angles, and moments during loading response of gait between individuals treated with operative compared with nonoperative management at 5 years after ACL injury. Forty athletes treated operatively and 17 athletes treated nonoperatively completed gait analysis at 5 years after ACL reconstruction or completion of nonoperative rehabilitation. Medial compartment joint contact forces were estimated using a previously validated, patient-specific electromyography-driven musculoskeletal model. Knee joint contact forces, angles, and moments were compared between the operative and nonoperative group using mixed model 2 × 2 analyses of variance. Peak medial compartment contact forces were larger in the involved limb of the nonoperative group (Op: 2.37 ± 0.47 BW, Non-Op: 3.03 ± 0.53 BW; effect size: 1.36). Peak external knee adduction moment was also larger in the involved limb of the nonoperative group (Op: 0.25 ± 0.08 Nm/kg·m, Non-Op: 0.32 ± 0.09 Nm/kg·m; effect size: 0.89). No differences in radiographic tibiofemoral osteoarthritis were present between the operative and nonoperative groups. Overall, participants treated nonoperatively walked with greater measures of medial compartment joint loading than those treated operatively, while sagittal plane group differences were not present. Statement of clinical relevance: The differences in medial knee joint loading at 5 years after operative and nonoperative management of ACL injury may have implications on the development of posttraumatic knee osteoarthritis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.24652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7808330PMC
December 2020

Slower Walking Speed Is Related to Early Femoral Trochlear Cartilage Degradation After ACL Reconstruction.

J Orthop Res 2020 03 18;38(3):645-652. Epub 2019 Nov 18.

Department of Mechanical Engineering, University of Delaware, Newark, Delaware.

Post-traumatic patellofemoral osteoarthritis (OA) is prevalent after anterior cruciate ligament reconstruction (ACLR) and early cartilage degradation may be especially common in the femoral trochlear cartilage. Determining the presence of and factors associated with early femoral trochlear cartilage degradation, a precursor to OA, is a critical preliminary step in identifying those at risk for patellofemoral OA development and designing interventions to combat the disease. Early cartilage degradation can be detected using quantitative magnetic resonance imaging measures, such as tissue T relaxation time. The purposes of this study were to (i) compare involved (ACLR) versus uninvolved (contralateral) femoral trochlear cartilage T relaxation times 6 months after ACLR, and (ii) determine the relationship between walking speed and walking mechanics 3 months after ACLR and femoral trochlear cartilage T relaxation times 6 months after ACLR. Twenty-six individuals (age 23 ± 7 years) after primary, unilateral ACLR participated in detailed motion analyses 3.3 ± 0.6 months after ACLR and quantitative magnetic resonance imaging 6.3 ± 0.5 months after ACLR. There were no limb differences in femoral trochlear cartilage T relaxation times. Slower walking speed was related to higher (worse) femoral trochlear cartilage T relaxation times in the involved limb (Pearson's r: -0.583, p = 0.002) and greater interlimb differences in trochlear T relaxation times (Pearson's r: -0.349, p = 0.080). Walking mechanics were weakly related to trochlear T relaxation times. Statement of clinical significance: Slower walking speed was by far the strongest predictor of worse femoral trochlear cartilage health, suggesting slow walking speed may be an early clinical indicator of future patellofemoral OA after ACLR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:645-652, 2020.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.24503DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7028512PMC
March 2020

Partial medial meniscectomy leads to altered walking mechanics two years after anterior cruciate ligament reconstruction: Meniscal repair does not.

Gait Posture 2019 10 27;74:87-93. Epub 2019 Aug 27.

University of Delaware, Newark, DE, USA.

Background: Partial meniscectomy dramatically increases the risk for post-traumatic, tibiofemoral osteoarthritis after anterior cruciate ligament reconstruction (ACLR). Concomitant medial meniscus surgery influences walking biomechanics (e.g., medial tibiofemoral joint loading) early after ACLR; whether medial meniscus surgery continues to influence walking biomechanics two years after ACLR is unknown.

Research Question: Does medial meniscus treatment at the time of ACLR influence walking biomechanics two years after surgery?

Methods: This is a secondary analysis of prospectively collected data from a clinical trial (NCT01773317). Fifty-six athletes (age 24 ± 8 years) with operative reports, two-year biomechanical analyses, and no second injury prior to two-year testing participated after primary ACLR. Participants were classified by concomitant medial meniscal status: no medial meniscus involvement (n = 36), partial medial meniscectomy (n = 9), and medial meniscus repair (n = 11). Participants underwent biomechanical analyses during over-ground walking including surface electromyography; a validated musculoskeletal model estimated medial compartment tibiofemoral contact forces. Gait variables were analyzed using 3 × 2 ANOVAs with group (medial meniscus treatment) and limb (involved versus uninvolved) comparisons.

Results: There was a main effect of group (p = .039) for peak knee flexion angle (PKFA). Participants after partial medial meniscectomy walked with clinically meaningfully smaller PKFAs in both the involved and uninvolved limbs compared to the no medial meniscus involvement group (group mean difference [95%CI]; involved: -4.9°[-8.7°, -1.0°], p = .015; uninvolved: -3.9°[-7.6°, -0.3°], p = .035) and medial meniscus repair group (involved: -5.2°[-9.9°, -0.6°], p = .029; uninvolved: -4.7°[-9.0°, -0.3°], p = .038). The partial medial meniscectomy group walked with higher involved versus uninvolved limb medial tibiofemoral contact forces (0.45 body weights, 95% CI: -0.01, 0.91 BW, p = 0.053) and truncated sagittal plane knee excursions, which were not present in the other two groups.

Significance: Aberrant gait biomechanics may concentrate high forces in the antero-medial tibiofemoral cartilage among patients two years after ACLR plus partial medial meniscectomy, perhaps explaining the higher osteoarthritis rates and offering an opportunity for targeted interventions.

Level Of Evidence: Level III.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.gaitpost.2019.08.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6790293PMC
October 2019

Gait Mechanics in Women of the ACL-SPORTS Randomized Control Trial: Interlimb Symmetry Improves Over Time Regardless of Treatment Group.

J Orthop Res 2019 08 20;37(8):1743-1753. Epub 2019 May 20.

Biomechanics and Movement Science Program, University of Delaware, Newark, Delaware.

Women after anterior cruciate ligament (ACL) injury and ACL reconstruction (ACLR) are more likely than men to exhibit asymmetric movement patterns, which are associated with post-traumatic osteoarthritis. We developed the ACL specialized post-operative return-to-sports (ACL-SPORTS) randomized control trial to test the effect of strength, agility, plyometric, and secondary prevention (SAPP) training with and without perturbation training (SAPP + PERT) on gait mechanics in women after ACLR. We hypothesized that movement symmetry would improve over time across both groups but more so among the SAPP + PERT group. Thirty-nine female athletes 3-9 months after primary ACLR were randomized to SAPP or SAPP + PERT training. Biomechanical testing during overground walking occurred before (Pre-training) and after (Post-training) training and one and 2 years post-operatively. Hip and knee kinematic and kinetic variables were compared using repeated measures analysis of variance with Bonferroni corrections for post hoc comparisons (α = 0.05). There was a time by limb interaction effect (p = 0.028) for peak knee flexion angle (PKFA), the primary outcome which powered the study, characterized by smaller PKFA in the involved compared to uninvolved limbs across treatment groups at Pre-training, Post-training, and 1 year, but not 2 years. Similar findings occurred across sagittal plane knee excursions and kinetics and hip extension excursion at midstance. There were no meaningful interactions involving group. Neither SAPP nor SAPP + PERT training improved walking mechanics, which persisted 1 but not 2 years after ACLR. Statement of clinical significance: Asymmetrical movement patterns persisted long after participants achieved symmetrical strength and functional performance, suggesting more time is needed to recover fully after ACLR. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1743-1753, 2019.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.24314DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6824924PMC
August 2019

High muscle co-contraction does not result in high joint forces during gait in anterior cruciate ligament deficient knees.

J Orthop Res 2019 01 9;37(1):104-112. Epub 2018 Oct 9.

Biomechanics and Movement Science, University of Delaware, 540 South College Avenue, Newark 19713, Delaware.

The mechanism of knee osteoarthritis development after anterior cruciate ligament injuries is poorly understood. The objective of this study was to evaluate knee gait variables, muscle co-contraction indices and knee joint loading in young subjects with anterior cruciate ligament deficiency (ACLD, n = 36), versus control subjects (n = 12). A validated, electromyography-informed model was used to estimate joint loading. For the involved limb of ACLD subjects versus control, muscle co-contraction indices were higher for the medial (p = 0.018, effect size = 0.93) and lateral (p = 0.028, effect size = 0.83) agonist-antagonist muscle pairs. Despite higher muscle co-contraction, medial compartment contact force was lower for the involved limb, compared to both the uninvolved limb (mean difference = 0.39 body weight, p = 0.009, effect size = 0.70) as well as the control limb (mean difference = 0.57 body weight, p = 0.007, effect size = 1.14). Similar observations were made for total contact force. For involved versus uninvolved limb, the ACLD group demonstrated lower vertical ground reaction force (mean difference = 0.08 body weight, p = 0.010, effect size = 0.70) and knee flexion moment (mean difference = 1.32% body weight * height, p = 0.003, effect size = 0.76), during weight acceptance. These results indicate that high muscle co-contraction does not always result in high knee joint loading, which is thought to be associated with knee osteoarthritis. Long-term follow-up is required to evaluate how gait alterations progress in non-osteoarthritic versus osteoarthritic subjects. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.24141DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6393175PMC
January 2019

Gait Mechanics After ACL Reconstruction Differ According to Medial Meniscal Treatment.

J Bone Joint Surg Am 2018 Jul;100(14):1209-1216

University of Delaware, Newark, Delaware.

Background: Knee osteoarthritis risk is high after anterior cruciate ligament reconstruction (ACLR) and arthroscopic meniscal surgery, and higher among individuals who undergo both. Although osteoarthritis development is multifactorial, altered walking mechanics may influence osteoarthritis progression. The purpose of this study was to compare gait mechanics after ACLR among participants who had undergone no medial meniscal surgery, partial medial meniscectomy, or medial meniscal repair.

Methods: This was a secondary analysis of data collected prospectively as part of a clinical trial. Sixty-one athletes (mean age of 21.4 ± 8.2 years) who had undergone primary ACLR participated in the study when they achieved impairment resolution (5.3 ± 1.7 months postoperatively), including minimal to no effusion, full knee range of motion, and ≥80% quadriceps-strength symmetry. Participants were classified by concomitant medial meniscal treatment: no involvement or nonsurgical management of a small, stable tear; partial meniscectomy; or meniscal repair. Participants underwent comprehensive walking analyses. Joint contact forces were estimated using a previously validated, electromyography-driven musculoskeletal model. Variables were analyzed using a mixed-model analysis of variance with group and limb comparisons (α = 0.05); group comparisons of interlimb differences in measurements (surgical minus contralateral limb) were performed to determine significant interactions.

Results: The participants in the partial meniscectomy group walked with a higher peak knee adduction moment (pKAM) in the surgical versus the contralateral limb as compared with those in the meniscal repair group and those with no medial meniscal surgery (group difference for partial versus repair: 0.10 N-m/kg-m, p = 0.020; and for partial versus none: 0.06 N-m/kg-m, p = 0.037). Participants in the repair group walked with a smaller percentage of medial to total tibiofemoral loading in the surgical limb compared with both of the other groups (group difference for repair versus partial: -12%, p = 0.001; and for repair versus none: -7%, p = 0.011). The participants in the repair group loaded the medial compartment of the surgical versus the contralateral limb 0.5 times body weight less than did the participants in the partial meniscectomy group.

Conclusions: Participants in the partial meniscectomy group walked with higher pKAM and shifted loading toward the medial compartment of the surgical limb, while participants in the repair group did the opposite, walking with lower pKAM and unloading the surgical limb relative to the contralateral limb. These findings may partially explain the conflicting evidence regarding pKAM after ACLR and the elevated risk for osteoarthritis (whether from overloading or underloading) after ACLR with concomitant medial meniscectomy or repair.

Level Of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2106/JBJS.17.01014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6636792PMC
July 2018

Gait mechanics and tibiofemoral loading in men of the ACL-SPORTS randomized control trial.

J Orthop Res 2018 09 24;36(9):2364-2372. Epub 2018 Apr 24.

Biomechanics and Movement Science, University of Delaware, Newark, Delaware.

The risk for post-traumatic osteoarthritis is elevated after anterior cruciate ligament reconstruction (ACLR), and may be especially high among individuals with aberrant walking mechanics, such as medial tibiofemoral joint underloading 6 months postoperatively. Rehabilitation training programs have been proposed as one strategy to address aberrant gait mechanics. We developed the anterior cruciate ligament specialized post-operative return-to-sports (ACL-SPORTS) randomized control trial to test the effect of 10 post-operative training sessions consisting of strength, agility, plyometric, and secondary prevention exercises (SAPP) or SAPP plus perturbation (SAPP + PERT) training on gait mechanics after ACLR. A total of 40 male athletes (age 23 ± 7 years) after primary ACLR were randomized to SAPP or SAPP + PERT training and tested at three distinct, post-operative time points: 1) after impairment resolution (Pre-training); 2) following 10 training sessions (Post-training); and 3) 2 years after ACLR. Knee kinematic and kinetic variables as well as muscle and joint contact forces were calculated via inverse dynamics and a validated electromyography-informed musculoskeletal model. There were no significant improvements from Pre-training to Post-training in either intervention group. Smaller peak knee flexion angles, extension moments, extensor muscle forces, medial compartment contact forces, and tibiofemoral contact forces were present across group and time, however the magnitude of interlimb differences were generally smaller and likely not meaningful 2 years postoperatively. Neither SAPP nor SAPP + PERT training appears effective at altering gait mechanics in men in the short-term; however, meaningful gait asymmetries mostly resolved between post-training and 2 years after ACLR regardless of intervention group. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2364-2372, 2018.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.23895DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6157011PMC
September 2018

Gait mechanics and second ACL rupture: Implications for delaying return-to-sport.

J Orthop Res 2017 09 18;35(9):1894-1901. Epub 2016 Nov 18.

Biomechanics and Movement Science, University of Delaware, Newark, Delaware.

Second anterior cruciate ligament rupture is a common and devastating injury among young women who return to sport after ACL reconstruction, but it is inadequately understood. The purpose of this study was to compare gait biomechanics and return-to-sport time frames in a matched cohort of young female athletes who, after primary ACLR, returned to sport without re-injury or sustained a second ACL injury. Approximately 6 months after primary reconstruction, 14 young women (age 16 ± 2 years) involved in jumping, cutting, and pivoting sports underwent motion analysis testing after physical therapy and impairment resolution. Following objective return-to-sport clearance, seven athletes sustained a second ACL rupture within 20 months of surgery (13.4 ± 4.9 months). We matched them by age, sex, and sport-level to seven athletes who returned to sports without re-injury. Data were analyzed using a previously validated, EMG-informed, patient-specific musculoskeletal model. Compared to athletes without re-injury, athletes who sustained a second ACL injury received surgery sooner (p = 0.023), had post-operative impairments resolved earlier (p = 0.022), reached criterion-based return-to-sport benchmarks earlier (p = 0.024), had higher body mass index (p = 0.039), and walked with lower peak knee flexor muscle forces bilaterally (p = 0.021). Athletes who sustained a second injury also tended to walk with larger (p = 0.089) and more symmetrical peak knee flexion angles and less co-contraction, all indicative of a more normal gait pattern. Statement of Clinical Significance: Delayed return-to-sport clearance even in the absence of gait or clinical impairments following primary ACL reconstruction may be necessary to mitigate second ACL injury risk in young women. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1894-1901, 2017.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.23476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5423861PMC
September 2017

Predictors of knee joint loading after anterior cruciate ligament reconstruction.

J Orthop Res 2017 03 17;35(3):651-656. Epub 2016 Oct 17.

University of Delaware, Newark, Delaware.

Anterior cruciate ligament (ACL) injury results in altered knee joint mechanics which frequently continue even after ACL reconstruction. The persistence of altered mechanical loading of the knee is of concern due to its likely role in the development of post-traumatic osteoarthritis (OA). Joint contact forces are associated with post-traumatic OA development, but evaluation of factors influencing the magnitude of contact forces after ACL injury is needed to advance current strategies aimed at preventing post-traumatic OA. Therefore, the purpose of this study was to identify predictive factors of knee joint contact forces after ACL reconstruction. Thirty athletes completed standard gait analysis with surface electromyography 6 months after ACL reconstruction. An electromyographic-driven musculoskeletal model was used to estimate joint contact forces. External knee adduction moment was a significant predictor of medial compartment contact forces in both limbs, while vertical ground reaction force and co-contraction only contributed significantly in the uninvolved limb. The large influence of the knee adduction moment on joint contact forces provides mechanistic clues to understanding the mechanical pathway of post-traumatic OA after ACL injury. Statement of Clinical Significance: This study provides critical information in improving the understanding of mechanisms influencing the development of post-traumatic OA after ACL injury. Further work is needed to identify additional driving factors of joint loading in the ACL-injured limb and develop treatment strategies to avert the deleterious consequences of post-traumatic OA. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:651-656, 2017.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/jor.23408DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6309880PMC
March 2017

Gait mechanics in those with/without medial compartment knee osteoarthritis 5 years after anterior cruciate ligament reconstruction.

J Orthop Res 2017 03 27;35(3):625-633. Epub 2016 Apr 27.

Departmentof Biomedical Engineering, University of Delaware, 540 South College Avenue, Newark, Delaware, 19713.

The objective of the study was to evaluate differences in gait mechanics 5 years after unilateral anterior cruciate ligament reconstruction surgery, for non-osteoarthritic (n = 24) versus osteoarthritic (n = 9) subjects. For the involved knee, the osteoarthritic group demonstrated significantly lower peak knee flexion angles (non-osteoarthritic = 24.3 ± 4.6°, osteoarthritic = 19.1 ± 2.9°, p = 0.01) and peak knee flexion moments (non-osteoarthritic = 5.3 ± 1.2% Body Weight × Height, osteoarthritic = 4.4 ± 1.2% Body Weight × Height, p = 0.05). Differences in peak knee adduction moment approached significance, with a higher magnitude for the osteoarthritic group (non-osteoarthritic = 2.4 ± 0.8% Body Weight × Height, osteoarthritic = 2.9 ± 0.5% Body Weight × Height, p = 0.09). Peak medial compartment joint load was evaluated using electromyography-informed neuromusculoskeletal modeling. Peak medial compartment joint load in the involved knee for the two groups was not different (non-osteoarthritic = 2.4 ± 0.4 Body Weight, osteoarthritic = 2.3 ± 0.6 Body Weight). The results suggest that subjects with dissimilar peak knee moments can have similar peak medial compartment joint load magnitudes. There was no evidence of inter-limb asymmetry for either group. Given the presence of inter-group differences (non-osteoarthritic vs. osteoarthritic) for the involved knee, but an absence of inter-limb asymmetry in either group, it may be necessary to evaluate how symmetry is achieved, over time, and to differentiate between good versus bad inter-limb symmetry, when evaluating knee gait parameters. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:625-633, 2017.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5065735PMC
http://dx.doi.org/10.1002/jor.23261DOI Listing
March 2017

Fetal Rat Gubernaculum Mesenchymal Cells Adopt Myogenic and Myofibroblast-Like Phenotypes.

J Urol 2016 07 31;196(1):270-8. Epub 2015 Dec 31.

Pediatric Urology Research Laboratory, Nemours Biomedical Research/Alfred I. duPont Hospital for Children, Wilmington, Delaware. Electronic address:

Purpose: Gubernaculum-cremaster complex development is hormonally regulated and abnormal in a cryptorchid rat model. Using cell tracking techniques and imaging we studied myogenic phenotypes and fates in the fetal rat gubernaculum-cremaster complex.

Materials And Methods: Embryonic day 17 gubernaculum-cremaster complexes were labeled with CellTracker™ or the DNA synthesis marker EdU (5-ethynyl-2'-deoxyuridine), or immobilized in Matrigel® and grown in culture. Embryonic day 17 to 21 gubernaculum-cremaster complex sections and cells were imaged using wide field and deconvolution immunofluorescence microscopy, and muscle and/or myofibroblast specific antibodies. Deconvolved image stacks were used to create a 3-dimensional model of embryonic day 21 gubernaculum-cremaster complex muscle.

Results: PAX7 (paired box 7) positive and myogenin positive muscle precursors were visible in a desmin-rich myogenic zone between muscle layers that elongated and became thicker during development. Gubernaculum-cremaster complex inner mesenchymal cells expressed desmin and αSMA (α smooth muscle actin) at lower levels than in the myogenic zone. After pulse labeling with CellTracker or EdU mesenchymal cells became incorporated into differentiated muscle. Conversely, mesenchymal cells migrated beyond Matrigel immobilized gubernaculum-cremaster complexes, expressed PAX7 and fused to form striated myotubes. Mesenchymal gubernaculum-cremaster complex cell lines proliferated more than 40 passages and showed contractile behavior but did not form striated muscle. Our 3-dimensional gubernaculum-cremaster complex model had 2 orthogonal ventral layers and an arcing inner layer of muscle.

Conclusions: Our data suggest that mesenchymal cells in the peripheral myogenic zone of the fetal gubernaculum-cremaster complex contribute to formation of a distinctively patterned cremaster muscle. Nonmyogenic, desmin and αSMA positive gubernaculum-cremaster complex mesenchymal cells proliferate and have a myofibroblast-like phenotype in culture. Intrinsic mechanical properties of these divergent cell types may facilitate perinatal inversion of the gubernaculum-cremaster complex.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.juro.2015.12.081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4914458PMC
July 2016

In vitro assessment of serum-saline ratios for fluid simulator testing of highly modular spinal implants with articulating surfaces.

SAS J 2008 1;2(4):171-83. Epub 2008 Dec 1.

Applied Spine Technologies, New Haven, Connecticut.

Background: The increasing complexity of articulating spinal implants prohibits the use of serum-supplemented simulator fluid testing because multicomponent interfaces retain residual protein and preclude gravimetric measurement. Our original hypothesis was that simulator testing of a posterior dynamic stabilization implant that has metal-on-metal articulating bearings will not produce dramatically different wear debris when tested using pure saline versus testing in saline supplemented with 20% serum.

Methods: This hypothesis was tested using simulator testing of 12 dynamic stabilization spinal implants, 6 in 100% saline and 6 in 20%-serum saline. Gravimetric and particle analysis were performed after every million cycles up to 10 million cycles, with flexion of 11.3°/extension of 5.6° coupled with axial rotation of ± 4°.

Results: The mean gravimetric weight loss was approximately 200 mg over 10 million cycles for the implants tested in 100% saline, while the mean weight loss for those tested in 20%-serum saline was below the method detection limits (< 10 mg over 10 million cycles). For the 100%-saline and 20%-serum simulator fluids, the average particle size over the course of 0 to 10 million cycles remained relatively constant at 0.2 µm-dia (saline) and 3.2 µm-dia (20%-serum saline). Testing in 100% saline generated > 1000-fold more particles, compared to testing in 20% serum-supplemented saline. Energy-dispersive X-ray (EDAX) analyses of particles demonstrated that the 100% saline debris was composed of Co-Cr-P-O (Cr-Co metal oxides), and for the 20%-serum saline debris only bulk metal Co-Cr was detected.

Conclusion: Our initial hypothesis was not supported. There were significant differences in gravimetric wear, average size, and type of wear debris that were mechanistically attributable to the type of simulator fluid used. The over-protective effect of serum proteins appears to underscore the importance of using both saline and serum when establishing upper and lower bounds of predictive implant debris generation modeling, where saline represents a worst-case scenario and as little as 20% serum masks all weight loss completely in highly modular articulating implants.

Clinical Relevance: Clinical Relevance = 5 (Oxford Centre for Evidence-based Medicine Levels of Evidence). Study findings are limited to a greater understanding of the science associated with predictive wear testing of articulating spinal implants.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/SASJ-2008-0013-RRDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4365664PMC
March 2015

Residual sagittal motion after lumbar fusion: a finite element analysis with implications on radiographic flexion-extension criteria.

Spine (Phila Pa 1976) 2007 Feb;32(4):417-22

Boston University School of Medicine, Department of Orthopaedic Surgery, Boston, MA, USA.

Study Design: Finite element analysis of a lumbar fusion model.

Objectives: To quantify residual sagittal angular motion following various types and levels of completeness of lumbar fusion in order to understand better the validity of current recommendations for interpreting flexion-extension radiographs to assess fusion.

Summary Of Background Data: Recommended threshold criteria for solid fusion using flexion-extension radiographs have varied from 0 degrees to 5 degrees of angular motion between vertebrae. Notwithstanding this wide variation and lack of uniform consensus, the validity of these criteria has not been previously biomechanically assessed to the authors' knowledge. To investigate this issue, the authors sought to test various types of simulated healed, noninstrumented lumbar fusions using finite element modeling to determine the amount of residual angular motion under physiologic stresses.

Methods: A validated 3-dimensional, nonlinear finite element model of an intact adult human L3-L4 motion segment was developed. Four fusion types were simulated using this model, including anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), intertransverse process fusion, and interspinous process fusion. Variations of completeness of fusion were also represented. For ALIF and PLIF, this included tests of solid bridging bone within the posterior or anterior 75%, 50%, or 25% disc space. In addition, PLIF was also tested with either a unilateral or bilateral facetectomy to simulate commonly used surgical techniques. Variations of intertransverse process fusion included unilateral or bilateral bridging bone with or without medial fusion to the pars interarticularis. Only 1 scenario of a healed, solid interspinous process fusion was tested. The intact model and all fusion models were stressed with 10.6-Nm flexion and extension moments. The angular deflections were recorded in degrees.

Results: A wide range of sagittal angular motion was recorded. For ALIF, this ranged from 0.8 degrees (complete, 100% fusion) to 3.3 degrees (solid fusion of the posterior 25% disc space). For PLIF, the numbers were more varied, ranging from 0.7 degrees (complete, 100% fusion) to 6.9 degrees (solid fusion of posterior 25% disc space with bilateral facetectomy). For intertransverse process fusion, the least motion was with a solid bilateral fusion, with medial healing to the pars (2.0 degrees); the greatest motion was found with a solid unilateral fusion without medial healing (6.0 degrees). Interspinous process fusion allowed only 1.9 degrees of motion.

Conclusions: The amount of residual flexion-extension motion with simulated lumbar fusions (presumably allowed by the bone's inherent elasticity) under physiologically comparable moments varies with fusion type and, more substantially, with varying amounts of completeness. The current study documents a range of sagittal angular motion after several types of simulated lumbar fusion that appear to have considerable overlap with previously purported radiographic criteria for solid fusion using flexion-extension radiographs. However, it also suggests the possibility that some scenarios of solid, yet incomplete, fusion may allow motion that is substantially greater than 5 degrees, which is beyond the most liberal of previously published threshold criteria.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/01.brs.0000255201.74795.20DOI Listing
February 2007

Biomechanical rationale for using polyetheretherketone (PEEK) spacers for lumbar interbody fusion-A finite element study.

Spine (Phila Pa 1976) 2006 Dec;31(26):E992-8

Engineering Center for Orthopaedic Research Excellence (E-CORE), Departments of Bioengineering and Orthopaedic Surgery, Colleges of Engineering and Medicine, University of Toledo, Toledo, OH 43606, USA.

Study Design: To determine the effect of cage/spacer stiffness on the stresses in the bone graft and cage subsidence.

Objective: To investigate the effect of cage stiffness on the biomechanics of the fused segment in the lumbar region using finite element analysis.

Summary Of Background Data: There are a wide variety of cage/spacer designs available for lumbar interbody fusion surgery. These range from circular, tapered, rectangular with and without curvature, and were initially manufactured using titanium alloy. Recent advances in the medical implant industry have resulted in using medical grade polyetheretherketone (PEEK). The biomechanical advantages of using different cage material in terms of stability, subsidence, and stresses in bone graft are not fully understood.

Methods: A previously validated 3-dimensional, nonlinear finite element model of an intact L3-L5 segment was modified to simulate posterior interbody fusion spacers made of PEEK ("E" = 3.6 GPa) and titanium ("E" = 110 GPa) at the L4/5 disc with posterior instrumentation. Bone graft ("E" = 12 GPa) packed between the spacers in the intervertebral space was also simulated. The posterior lumbar interbody fusion spacer with instrumentation and graft represent a simulation of the condition present immediately after surgery.

Results: The peak centroidal Von Mises stresses in the graft bone increased by at least 9-fold with PEEK spacers as compared to titanium spacer. The peak centroidal Von Mises stresses in the endplates increased by at least 2.4-fold with titanium spacers over the PEEK spacers. These stresses were concentrated at places where the spacer interfaced with the endplate. The stiffness of the spacer did not affect the relative motion (stability) across the instrumented (L4/5) segment.

Conclusions: Spacers less stiff than the graft will: (1) provide stability similar to titanium cages in the presence of posterior instrumentation, (2) reduce the stresses in endplates adjacent to the spacers, and (3) increase the load transfer through the graft, as evident from the increase in stresses in graft.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/01.brs.0000250177.84168.baDOI Listing
December 2006

Effect of lumbar interbody cage geometry on construct stability: a cadaveric study.

Spine (Phila Pa 1976) 2006 Sep;31(19):2189-94

Spine Research Center, Department of Bioengineering, University of Toledo, OH 43606, USA.

Study Design: Biomechanical study to investigate three-dimensional motion behavior of cadaveric spines in various surgical simulations.

Objectives: To determine the effect of cage geometry on the construct stability.

Summary Of Background Data: There is a wide variety of cage/spacer designs available for lumbar interbody fusion surgery. These range from circular, tapered, and rectangular with and without curvature. However, the effectiveness of cages with different designs and materials to stabilize a decompressed intervertebral space has not been fully studied.

Methods: Six fresh ligamentous lumbar spine specimens (L1-S2) were subjected to pure moments in the six loading directions. The resulting spatial orientations of the vertebrae were recorded using Optotrak Motion Measurement System. Measurements were made sequentially for intact, bilateral spacer placements across L4-L5 using a posterior approach, supplemented with pedicle screw-rod system fixation, and after the cyclic loading in flexion-extension mode.

Results: The stability tended to decrease after the bilateral cage placement as compared with the intact for all loading cases except flexion. In flexion, the angular displacement decreased to 80% of the intact. However, there was no significant statistical difference seen in stability between intact and after bilateral spacer placement. Following the addition of posterior fixation using pedicle screw-rod system, the stability significantly increased in all directions. Cyclic loading did not have any significant effect on the stability.

Conclusions: Stand-alone cages restore motion to near-intact levels at best, and supplement instrumentation is essential for significantly increasing the stability of the decompressed segment. The effects of cage geometry and Young's modulus of the cage material do not seem to influence the stability, as compared with the other cagedesigns, especially after supplemental fixation with a posterior system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/01.brs.0000232720.23748.ceDOI Listing
September 2006
-->