Load carriage changes tibiofemoral arthrokinematics during ambulatory tasks in recruit-aged women.

The introduction of women into U.S. military ground close combat roles requires research into sex-specific effects of military training and operational activities. Knee osteoarthritis is prevalent among military service members; its progression has been linked to occupational tasks such as load carriage. Analyzing tibiofemoral arthrokinematics during load carriage is important to understand potentially injurious motion and osteoarthritis progression. The study purpose was to identify effects of load carriage on knee arthrokinematics during walking and running in recruit-aged women. Twelve healthy recruit-aged women walked and ran while unloaded (bodyweight [BW]) and carrying additional + 25%BW and + 45%BW. Using dynamic biplane radiography and subject-specific bone models, tibiofemoral arthrokinematics, subchondral joint space and center of closest contact location between subchondral bone surfaces were analyzed over 0-30% stance (separate one-way repeated measures analysis of variance, load by locomotion). While walking, medial compartment contact location was 5% (~ 1.6 mm) more medial for BW than + 45%BW at foot strike (p = 0.03). While running, medial compartment contact location was 4% (~ 1.3 mm) more lateral during BW than + 25%BW at 30% stance (p = 0.04). Internal rotation was greater at + 45%BW compared to + 25%BW (p < 0.01) at 30% stance. Carried load affects tibiofemoral arthrokinematics in recruit-aged women. Prolonged load carriage could increase the risk of degenerative joint injury in physically active women.

Ankle and hindfoot motion of healthy adults during running revealed by dynamic biplane radiography: Side-to-side symmetry, sex-specific differences, and comparison with walking.

This study aimed to characterize ankle and hindfoot kinematics of healthy men and women during overground running using biplane radiography, and to compare these data to those previously obtained in the same cohort during overground walking. Participants ran across an elevated platform at a self-selected pace while synchronized biplane radiographs of their ankle and hindfoot were acquired. Motion of the tibia, talus, and calcaneus was tracked using a validated volumetric model-based tracking process. Tibiotalar and subtalar 6DOF kinematics were obtained. Absolute side-to-side differences in ROM and kinematics waveforms were calculated. Side-to-side and sex-specific differences were evaluated at 10 % increments of stance phase with mixed model analysis. Pearson correlation coefficients were used to assess the relationship between stance-phase running and walking kinematics. 20 participants comprised the study cohort (10 men, mean age 30.8 ± 6.3 years, mean BMI 24.1 ± 3.1). Average absolute side-to-side differences in running kinematics waveforms were 5.6°/2.0 mm or less at the tibiotalar joint and 5.2°/3.2 mm or less at the subtalar joint. No differences in running kinematics waveforms between sides or between men and women were detected. Correlations were stronger at the tibiotalar joint (42/66 [64 %] of correlations were p < 0.05), than at the tibiotalar joint (38/66 [58 %] of correlations were p < 0.05). These results provide a normative reference for evaluating native ankle and hindfoot kinematics which may be informative in surgical or rehabilitation contexts. Sex-specific differences in ankle kinematics during overground running are likely not clinically or etiologically significant. Associations seen between walking and running kinematics suggest one could be used to predict the other.

Accuracy of conventional motion capture in measuring hip joint center location and hip rotations during gait, squat, and step-up activities.

Accurate measurements of hip joint kinematics are essential for improving our understanding of the effects of injury, disease, and surgical intervention on long-term hip joint health. This study assessed the accuracy of conventional motion capture (MoCap) for measuring hip joint center (HJC) location and hip joint angles during gait, squat, and step-up activities while using dynamic biplane radiography (DBR) as the reference standard. Twenty-four young adults performed six trials of treadmill walking, six body-weight squats, and six step-ups within a biplane radiography system. Synchronized biplane radiographs were collected at 50 images per second and MoCap was collected simultaneously at 100 images per second. Bone motion during each activity was determined by matching digitally reconstructed radiographs, created from subject-specific CT-based bone models, to the biplane radiographs using a validated registration process. Errors in estimating HJC location and hip angles using MoCap were quantified by the root mean squared error (RMSE) across all frames of available data. The MoCap error in estimating HJC location was larger during step-up (up to 89.3 mm) than during gait (up to 16.6 mm) or squat (up to 31.4 mm) in all three anatomic directions (all p < 0.001). RMSE in hip joint flexion (7.2°) and abduction (4.3°) during gait was less than during squat (23.8° and 8.9°) and step-up (20.1° and 10.6°) (all p < 0.01). Clinical analysis and computational models that rely on skin-mounted markers to estimate hip kinematics should be interpreted with caution, especially during activities that involve deeper hip flexion.

Influence of Talar and Calcaneal Morphology on Subtalar Kinematics During Walking.

BACKGROUND: Cadaver biomechanical testing suggests that the morphology of articulating bones contributes to the stability of the joints and determines their kinematics; however, there are no studies examining the correlation between bone morphology and kinematics of the subtalar joint. The purpose of this study was to investigate the influence of talar and calcaneal morphology on subtalar kinematics during walking in healthy individuals. METHODS: Forty ankles (20 healthy subjects, 10 women/10 men) were included. Participants walked at a self-selected pace while synchronized biplane radiographs of the hindfoot were acquired at 100 images per second during stance. Motion of the talus and calcaneus was tracked using a validated volumetric model-based tracking process, and subtalar kinematics were calculated. Talar and calcaneal morphology were evaluated using statistical shape modeling. Pearson correlation coefficients were used to assess the relationship between subtalar kinematics and the morphology features of the talus and calcaneus. RESULTS: This study found that a shallower posterior facet of the talus was correlated with the subtalar joint being in more dorsiflexion, more inversion, and more internal rotation, and higher curvature in the posterior facet was correlated with more inversion and eversion range of motion during stance. In the calcaneus, a gentler slope of the middle facet was correlated with greater subtalar inversion. CONCLUSION: The morphology of the posterior facet of the talus was found to a primary factor driving multiplanar subtalar joint kinematics during the stance phase of gait. CLINICAL RELEVANCE: This new knowledge relating form and function in the hindfoot may assist in identifying individuals susceptible to subtalar instability and in improving implant design to achieve desired kinematics after surgery.

Tibial spine volume is smaller in ACL-injured athletes compared to healthy athletes.

PURPOSE: The aim of this study was to investigate whether the whole tibial spine volume and femoral intercondylar notch volume are risk factors for anterior cruciate ligament (ACL) injury. The hypothesis was that the whole tibial spine volume and femoral notch volume would be smaller in athletes who sustained ACL injury than in athletes with no history of ACL injury. METHODS: Computed tomography scans of both knees were acquired and three-dimensional bone models were created using Mimics to measure whole tibial spine volume and femoral notch volume. Tibial spine volume, femoral notch volume and each of these volumes normalised by tibial plateau area were compared between the ACL-injured and the ACL-intact group. RESULTS: Fifty-one athletes undergoing unilateral anatomical ACL reconstruction (17 female, 34 male: average age 22.0 ± 7.5) and 19 healthy collegiate athletes with no previous knee injury (eight female, 11 male: average age 20.1 ± 1.3) were included in this study. The whole tibial spine volume in the ACL-injured group (2.1 ± 0.5 cm3) was 20.7% smaller than in the ACL-intact group (2.7 ± 0.7 cm3) (p = 0.005). No differences were observed between the femoral notch volume in the ACL-injured group (9.5 ± 2.1 cm3) and the ACL-intact group (8.7 ± 2.7 cm3) (n.s.). CONCLUSIONS: The main finding of this study was that the whole tibial spine volume of the ACL-injured group was smaller than the ACL-intact group. A small tibial spine volume can be added to the list of anatomical risk factors that may predispose athletes to ACL injury. LEVEL OF EVIDENCE: Level Ⅲ.

A scoping review of human skeletal kinematics research using biplane radiography.

Biplane radiography has emerged as the gold standard for accurately measuring in vivo skeletal kinematics during physiological loading. The purpose of this scoping review was to map the extent, range, and nature of biplane radiography research on humans from 2004 through 2022. A literature search was performed using the terms biplane radiography, dual fluoroscopy, dynamic stereo X-ray, and biplane videoradiography. All articles referenced in included publications were also assessed for inclusion. A secondary search was then performed using the names of the most frequently appearing principal investigators among included papers. A total of 379 manuscripts were identified and included. The first studies published in 2004 focused on the native knee, followed by studies of the ankle joint complex in 2006, the shoulder in 2007, and the spine in 2008. Nearly half (180, 47.5%) of all manuscripts investigated knee kinematics. The average number of publications increased from 21.6 per year from 2012 to 2017 to 34.6 per year from 2017 to 2022. The average number of participants per study was 16, with a range from 1 to 101. A total of 90.2% of studies featured cohorts of 30 or less. The most prolific research groups for each joint were: Mass General Hospital (lumbar spine and knee), Henry Ford Hospital (shoulder), the University of Utah (ankle and hip), The University of Pittsburgh (cervical spine), and Brown University (hand/wrist/elbow). Future advancements in biplane radiography research are dependent upon increased availability of these imaging systems, standardization of data collection protocols, and the development of automated approaches to expedite data processing.

Improved joint function when reaching behind the back is associated with patient reported outcomes in individuals with rotator cuff tears following exercise therapy.

BACKGROUND: Reaching behind the back is painful for individuals with rotator cuff tears. The objectives of the study were to determine changes in glenohumeral kinematics when reaching behind the back, passive range of motion (RoM), patient reported outcomes and the relationships between kinematics and patient reported outcomes following exercise therapy. METHODS: Eighty-four individuals with symptomatic isolated supraspinatus tears were recruited for this prospective observational study. Glenohumeral kinematics were measured using biplane radiography during a reaching behind the back movement. Passive glenohumeral internal rotation and patient reported outcome measures were collected. Depending on data normality, appropriate tests were utilized to determine changes in variables. Spearman's correlations were utilized for associations, and Stuart-Maxwell tests for changes in distributions. FINDINGS: Maximum active glenohumeral internal rotation increased by 3.2° (P = 0.001), contact path length decreased by 5.5% glenoid size (P = 0.022), passive glenohumeral internal rotation RoM increased by 4.9° (P = 0.001), and Western Ontario Rotator Cuff Index and American Shoulder and Elbow Surgeons scores increased by 29.8 and 21.1 (P = 0.001), respectively. Changes in Western Ontario Rotator Cuff Index scores positively associated with changes in maximum active glenohumeral internal rotation and negatively associated with changes in contact path lengths (P = 0.008 and P = 0.006, respectively). INTERPRETATION: The reaching behind the back movement was useful in elucidating in-vivo mechanistic changes associated with patient reported outcomes. Glenohumeral joint function and patient reported outcomes improved, where changes in Western Ontario Rotator Cuff Index scores were associated with kinematics. These findings inform clinicians of functional changes following exercise therapy and new targetable treatment factors.

Individuals with rotator cuff tears unsuccessfully treated with exercise therapy have less inferiorly oriented net muscle forces during scapular plane abduction.

Exercise therapy for individuals with rotator cuff tears fails in approximately 25.0 % of cases. One reason for failure of exercise therapy may be the inability to strengthen and balance the muscle forces crossing the glenohumeral joint that act to center the humeral head on the glenoid. The objective of the current study was to compare the magnitude and orientation of the net muscle force pre- and post-exercise therapy between subjects successfully and unsuccessfully (e.g. eventually underwent surgery) treated with a 12-week individualized exercise therapy program. Twelve computational musculoskeletal models (n = 6 successful, n = 6 unsuccessful) were developed in OpenSim (v4.0) that incorporated subject specific tear characteristics, muscle peak isometric force, in-vivo kinematics and bony morphology. The models were driven with experimental kinematics and the magnitude and orientation of the net muscle force was determined during scapular plane abduction at pre- and post-exercise therapy timepoints. Subjects unsuccessfully treated had less inferiorly oriented net muscle forces pre- and post-exercise therapy compared to subjects successfully treated (p = 0.039 & 0.045, respectively). No differences were observed in the magnitude of the net muscle force (p > 0.05). The current study developed novel computational musculoskeletal models with subject specific inputs capable of distinguishing between subjects successfully and unsuccessfully treated with exercise therapy. A less inferiorly oriented net muscle force in subjects unsuccessfully treated may increase the risk of superior migration leading to impingement. Adjustments to exercise therapy programs may be warranted to avoid surgery in subjects at risk of unsuccessful treatment.

Ankle and subtalar joint axes of rotation and center of rotation during walking and running in healthy individuals measured using dynamic biplane radiography.

The goal of this study was to determine how foot type and activity level affect ankle and hindfoot motion. Dynamic biplane radiography and a validated volumetric registration process was used to measure ankle and hindfoot motion of 20 healthy adults during walking and running. The helical axes of motion (HAM) during stance were calculated at the tibiotalar and subtalar joints. The intersection of each HAM and the rotation plane of interest defined the tibiotalar and subtalar centers of rotation (COR). Correlations between foot type and hindfoot kinematics were calculated using Pearson's correlations. The effect of activity, phase of gait, and dominant vs. non-dominant limb on HAM and COR were evaluated using linear mixed effects models. Activity and phase of gait influenced the superior location of the tibiotalar (p < 0.041) and subtalar (p < 0.044) CORs. Activity and gait phase affected tibiotalar (p < 0.049) and subtalar (p < 0.044) HAM direction during gait. Both HAM orientation and COR location changed with activity and phase of gait. These ankle and hindfoot kinematics have implications for total ankle replacement design and musculoskeletal models that estimate force and moment generating capabilities of muscles.

Bone morphology features associated with knee kinematics may not be predictive of ACL elongation during high-demand activities.

PURPOSE: Bony morphology has been proposed as a potential risk factor for anterior cruciate ligament (ACL) injury. The relationship between bony morphology, knee kinematics, and ACL elongation during high-demand activities remains unclear. The purpose of this study was to determine if bone morphology features that have been associated with ACL injury risk and knee kinematics are also predictive of ACL elongation during fast running and double-legged drop jump. METHODS: Nineteen healthy athletes performed fast running and double-legged drop jump within a biplane radiography imaging system. Knee kinematics and ACL elongation were measured bilaterally after using a validated registration process to track bone motion in the radiographs and after identifying ACL attachment sites on magnetic resonance imaging (MRI). Bony morphological features of lateral posterior tibial slope (LPTS), medial tibial plateau (MTP) depth, and lateral femoral condyle anteroposterior width (LCAP)/lateral tibial plateau anteroposterior width (TPAP) were measured on MRI. Relationships between bony morphology and knee kinematics or ACL elongation were identified using multiple linear regression analysis. RESULTS: No associations between bony morphology and knee kinematics or ACL elongation were observed during fast running. During double-legged drop jump, a greater range of tibiofemoral rotation was associated with a steeper LPTS (ß = 0.382, p = 0.012) and a deeper MTP depth (ß = 0.331, p = 0.028), and a greater range of anterior tibial translation was associated with a shallower MTP depth (ß = - 0.352, p = 0.018) and a larger LCAP/ TPAP (ß = 0.441, p = 0.005); however, greater ACL elongation was only associated with a deeper MTP depth (ß = 0.456, p = 0.006) at toe-off. CONCLUSION: These findings indicate that observed relationships between bony morphology and kinematics should not be extrapolated to imply a relationship also exists between those bone morphology features and ACL elongation during high-demand activities. These new findings deepen our understanding of the relationship between bony morphology and ACL elongation during high-demand activities. This knowledge can help identify high-risk patients for whom additional procedures during ACL reconstruction are most appropriate.

In Vivo Graft Elongation After Arthroscopic Dermal Superior Capsular Reconstruction.

BACKGROUND: Superior capsular reconstruction (SCR) is a procedure purported to restore stability of the glenohumeral joint after an irreparable rotator cuff tear, but the in vivo behavior of the graft is unknown. Previous work has not evaluated the relationship between graft deformation, kinematics, and healing. PURPOSE: To (1) determine regional graft elongation after SCR, (2) determine if graft elongation is related to graft healing, and (3) identify associations between graft elongation and changes in kinematics from presurgery to postsurgery. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Ten patients who underwent SCR performed abduction and shoulder rotation with the arm at 90° of humerothoracic abduction before and 1 year after surgery while biplane radiographs were collected at 50 images per second. Kinematics was determined with submillimeter accuracy by matching patient-specific digitally reconstructed radiographs of the humerus and scapula to the biplane radiographs using a validated volumetric tracking technique. Graft elongation was calculated using motion of the graft anchors that were identified on postoperative magnetic resonance imaging. Differences in elongation between anterior and posterior regions of the graft, as well as associations between graft elongation, graft healing, and kinematics, were analyzed. RESULTS: Peak graft elongation ranged from a 3% decrease in the anterior region during rotation to up to a 171% increase in the anterior region during abduction and the posterior region during rotation. Grafts that were healed at both anterior anchors reached the intraoperative length at lower abduction angles (60°) than grafts that were not healed at 1 or both of the anterior anchors (87°) (P = .005). The posterior anchor graft origin to insertion distances were 2.1 mm farther apart after surgery compared with before surgery during both abduction and rotation. CONCLUSION: SCR dermal allografts are stretched well beyond their intraoperative length in vivo. Graft healing appears to be associated with less graft elongation. The posterior portion of the SCR graft does not appear to improve glenohumeral joint stability 1 year after surgery. Improved clinical outcomes after dermal allograft SCR may be because of the spacer effect of the graft rather than improved glenohumeral joint stability 1 year after surgery.

Symmetry in knee arthrokinematics in healthy collegiate athletes during fast running and drop jump revealed through dynamic biplane radiography.

OBJECTIVE: Changes in cartilage contact area and/or contact location after knee injury can initiate and exacerbate cartilage degeneration. Typically, the contralateral knee is used as a surrogate for native cartilage contact patterns on the injured knee. However, symmetry in cartilage contact patterns between healthy knees during high-impact activities is unknown. METHOD: Tibiofemoral kinematics were measured on 19 collegiate athletes during fast running and drop jump using dynamic biplane radiography and a validated registration process that matched computed tomography (CT)-based bone models to the biplane radiographs. Cartilage contact area and location were measured with participant-specific magnetic resonance imaging (MRI)-based cartilage models superimposed on the CT-based bone models. Symmetry in cartilage contact area and location was assessed by the absolute side-to-side differences (SSD) within participants. RESULTS: The SSD in contact area during running (7.7 ± 6.1% and 8.0 ± 4.6% in the medial and lateral compartments, respectively) was greater than during drop jump (4.2 ± 3.7% and 5.7 ± 2.6%, respectively) (95% CI of the difference: medial [2.4%, 6.6%], lateral [1.5%, 4.9%]). The average SSD in contact location was 3.5 mm or less in the anterior-posterior (AP) direction and 2.1 mm or less in the medial-lateral (ML) direction on the femur and tibia for both activities. The SSD in AP contact location on the femur was greater during running than during drop jump (95% CI of the difference: medial [1.6 mm, 3.6 mm], lateral [0.6 mm, 1.9 mm]). CONCLUSION: This study provides context for interpreting results from previous studies on tibiofemoral arthrokinematics. Previously reported differences between ligament-repaired and contralateral knee arthrokinematics fall within the range of typical SSDs observed in healthy athletes. Previously reported arthrokinematics differences that exceed SSDs found in these healthy athletes occur only in the presence of anterior cruciate ligament (ACL) deficiency or meniscectomy.

The Effects of Cervical Orthoses on Head and Intervertebral Range of Motion.

STUDY DESIGN: Prospective Cohort. OBJECTIVE: Quantify and compare the effectiveness of cervical orthoses in restricting intervertebral kinematics during multiplanar motions. SUMMARY OF BACKGROUND DATA: Previous studies evaluating the efficacy of cervical orthoses measured global head motion and did not evaluate individual cervical motion segment mobility. Prior studies focused only on the flexion/extension motion. METHODS: Twenty adults without neck pain participated. Vertebral motion from the occiput through T1 was imaged using dynamic biplane radiography. Intervertebral motion was measured using an automated registration process with validated accuracy better than 1 degree. Participants performed independent trials of maximal flexion/extension, axial rotation, and lateral bending in a randomized order of unbraced, soft collar (foam), hard collar (Aspen), and cervical thoracic orthosis (CTO) (Aspen) conditions. Repeated-measures ANOVA was used to identify differences in the range of motion (ROM) among brace conditions for each motion. RESULTS: Compared with no collar, the soft collar reduced flexion/extension ROM from occiput/C1 through C4/C5, and reduced axial rotation ROM at C1/C2 and from C3/C4 through C5/C6. The soft collar did not reduce motion at any motion segment during lateral bending. Compared with the soft collar, the hard collar reduced intervertebral motion at every motion segment during all motions, except for occiput/C1 during axial rotation and C1/C2 during lateral bending. The CTO reduced motion compared with the hard collar only at C6/C7 during flexion/extension and lateral bending. CONCLUSIONS: The soft collar was ineffective as a restraint to intervertebral motion during lateral bending, but it did reduce intervertebral motion during flexion/extension and axial rotation. The hard collar reduced intervertebral motion compared with the soft collar across all motion directions. The CTO provided a minimal reduction in intervertebral motion compared with the hard collar. The utility in using a CTO rather than a hard collar is questionable, given the cost and little or no additional motion restriction.

Dynamic Changes in Lumbar Spine Kinematics During Gait May Explain Improvement in Back Pain and Disability in Patients With Hip-Spine Syndrome.

STUDY DESIGN: Prospective cohort. OBJECTIVE: Determine if total hip arthroplasty (THA) changes lumbar spine kinematics during gait in a manner that explains the improvements in back pain seen in patients with hip-spine syndrome. SUMMARY OF BACKGROUND DATA: For patients with hip-spine syndrome, improvements in both hip and back pain have been demonstrated after THA; however, the exact mechanism of improvement in back pain remains unknown, as no corresponding changes in lumbar spine static radiographic parameters have been identified. METHODS: Thirteen patients with severe, unilateral hip osteoarthritis scheduled to undergo THA with concomitant back pain and disability were tested at baseline and 6 months after THA. Harris Hip Score (HHS) and Oswestry Disability Index questionnaires were completed; the static orientation of the spine and pelvis were measured on standing radiographs, and lumbar spine kinematics were measured during treadmill walking using a validated measurement system that matched subject-specific bone models created from CT scans to dynamic biplane radiographs. RESULTS: After THA, both the Oswestry Disability Index (36.3-11.3, P <0.001) and Harris Hip Score (55.7-77.9, P <0.001) improved; however, there were no changes in static intervertebral or pelvis orientation. During gait after THA, the overall lumbar spine (L1 to L5) was less lordotic from heel strike to contralateral toe off ( P <0.001), the L4 and L5 vertebra were less anteriorly tilted by 3.9° ( P =0.038) from midstance to contralateral heel strike and by 3.9° ( P =0.001) during stance, respectively. CONCLUSION: The decreased anterior tilt of the 2 lowest lumbar vertebrae and the corresponding loss of lumbar lordosis may reduce facet loading during the stance phase of gait after THA. This change in lumbar spine kinematics during gait is a potential mechanism to explain the observed improvements in back pain and disability after THA. LEVEL OF EVIDENCE: 4.

How Many Trials Are Needed to Estimate Typical Lumbar Movement Patterns During Dynamic X-Ray Imaging?

Dynamic biplane radiographic (DBR) imaging measures continuous vertebral motion during in vivo, functional tasks with submillimeter accuracy, offering the potential to develop novel biomechanical markers for lower back disorders based on true dynamic motion rather than metrics based on static end-range of motion. Nevertheless, the reliability of DBR metrics is unclear due to the inherent variability in movement over multiple repetitions and a need to minimize radiation exposure associated with each movement repetition. The objectives of this study were to determine the margin of uncertainty (MOU) in estimating the typical intervertebral kinematics waveforms based upon only a small number of movement repetitions, and to determine the day-to-day repeatability of intervertebral kinematics waveforms measured using DBR. Lumbar spine kinematics data were collected from two participant groups who performed multiple trials of flexion-extension or lateral bending to assess the uncertainty in the mean estimated waveform. The first group performed ten repetitions on the same day. Data from that group were used to estimate MOU as a function of the number of repetitions. The second group performed five repetitions on each of two separate days. MOU was not only movement-specific, but also motion segment-specific. Using just one or two trials yielded a relatively high MOU (e.g., >4 deg or 4 mm), however, collecting at least three repetitions reduced the MOU by 40% or more. Results demonstrate the reproducibility of DBR-derived measurements is greatly improved by collecting at least three repetitions, while simultaneously minimizing the amount of radiation exposure to participants.

Recruit-aged adults may preferentially weight task goals over deleterious cost functions during short duration loaded and imposed gait tasks.

Optimal motor control that is stable and adaptable to perturbation is reflected in the temporal arrangement and regulation of gait variability. Load carriage and forced-marching are common military relevant perturbations to gait that have been implicated in the high incidence of musculoskeletal injuries in military populations. We investigated the interactive effects of load magnitude and locomotion pattern on motor variability, stride regulation and spatiotemporal complexity during gait in recruit-aged adults. We further investigated the influences of sex and task duration. Healthy adults executed trials of running and forced-marching with and without loads at 10% above their gait transition velocity. Spatiotemporal parameters were analyzed using a goal equivalent manifold approach. With load and forced-marching, individuals used a greater array of motor solutions to execute the task goal (maintain velocity). Stride-to-stride regulation became stricter as the task progressed. Participants exhibited optimal spatiotemporal complexity with significant but not meaningful differences between sexes. With the introduction of load carriage and forced-marching, individuals relied on a strategy that maximizes and regulates motor solutions that achieve the task goal of velocity specifically but compete with other task functions. The appended cost penalties may have deleterious effects during prolonged execution, potentially increasing the risk of musculoskeletal injuries.

How well does intra-operative contact path predict post-operative contact path during activities of daily living after medial unicompartmental knee arthroplasty?

Robot-assisted surgical systems can predict post-operative kinematics based upon intra-operative passive kinematics, planned implant position and alignment, and soft-tissue tension. It is currently unknown how well the intra-operative passive kinematics replicate the post-surgical weight bearing active kinematics. This study compared intra-operative and post-operative tibiofemoral implant contact paths after medial unicompartmental knee arthroplasty (mUKA). Passive intraoperative and active postoperative tibiofemoral contact path data was collected from eight patients who underwent mUKA. Intraoperative contact path data was measured using a navigation system. Postoperative contact path data was measured during walking, chair rise, stair ascent, and stair descent using a biplane radiography system and a validated tracking process. A total of 86 movement trials were included in the analysis. The contact point on the femur implant was up to 9.8 mm more medial and up to 8.3 mm less anterior at low flexion angles during activities of daily living than during passive extension intra-operatively, and the contact point on the tibia implant was up to 13.8 mm less lateral and up to 5.8 mm less posterior at low flexion angles during activities of daily living than during intra-operative passive extension. Femoral contact paths primarily differed between 3° and 42° of flexion; and tibial contact paths differed between 3° and 50° of flexion. This pilot study is the first to compare intra-operative and post-operative weight bearing contact paths. The primary conclusions from this study are that contact points on the femur implant are more medial and less anterior at low flexion angles during activities of daily living than during passive extension intra-operatively, and that the contact points on the tibia implant are less lateral at low flexion angles during activities of daily living than during intra-operative passive extension.

Toward the Identification of Distinct Phenotypes: Research Protocol for the Low Back Pain Biological, Biomechanical, and Behavioral (LB3P) Cohort Study and the BACPAC Mechanistic Research Center at the University of Pittsburgh.

As a member of the Back Pain Consortium (BACPAC), the University of Pittsburgh Mechanistic Research Center's research goal is to phenotype chronic low back pain using biological, biomechanical, and behavioral domains using a prospective, observational cohort study. Data will be collected from 1,000 participants with chronic low back pain according to BACPAC-wide harmonized and study-specific protocols. Participation lasts 12 months with one required in person baseline visit, an optional second in person visit for advanced biomechanical assessment, and electronic follow ups at months 1, 2, 3, 4, 5, 6, 9, and 12 to assess low back pain status and response to prescribed treatments. Behavioral data analysis includes a battery of patient-reported outcomes, social determinants of health, quantitative sensory testing, and physical activity. Biological data analysis includes omics generated from blood, saliva, and spine tissue. Biomechanical data analysis includes a physical examination, lumbopelvic kinematics, and intervertebral kinematics. The statistical analysis includes traditional unsupervised machine learning approaches to categorize participants into groups and determine the variables that differentiate patients. Additional analysis includes the creation of a series of decision rules based on baseline measures and treatment pathways as inputs to predict clinical outcomes. The characteristics identified will contribute to future studies to assist clinicians in designing a personalized, optimal treatment approach for each patient.

Preoperative quantitative pivot shift does not correlate with in vivo kinematics following ACL reconstruction with or without lateral extraarticular tenodesis.

PURPOSE: Quantitative pivot shift (QPS) testing using PIVOT technology can detect high- and low-grade rotatory knee instability following anterior cruciate ligament injury or reconstruction (ACLR). The aim of this project was to determine if preoperative QPS correlates with postoperative knee kinematics in the operative and contralateral, healthy extremity following ACLR with or without lateral extraarticular tenodesis (LET) using a highly precise in vivo analysis system. A positive correlation between preoperative QPS and postoperative tibial translation and rotation following ACLR with or without LET in the operative and healthy, contralateral extremity was hypothesized. METHODS: Twenty patients with ACL injury and high-grade rotatory knee instability were randomized to undergo anatomic ACLR with or without LET as part of a prospective randomized trial. At 6 and 12 months postoperatively, in vivo kinematic data were collected using dynamic biplanar radiography superimposed with high-resolution computed tomography scans of patients' knees during downhill running. Total anterior-posterior (AP) tibial translation and internal-external tibial rotation were measured during the gait cycle. Spearman's rho was calculated for preoperative QPS and postoperative kinematics. RESULTS: In the contralateral, healthy extremity, a significant positive correlation was seen between preoperative QPS and total AP tibial translation at 12 months postoperatively (rs = 0.6, p < 0.05). There were no additional significant correlations observed between preoperative QPS and postoperative knee kinematics at 6 and 12 months postoperatively in the operative and contralateral, healthy extremity for combined isolated ACLR and ACLR with LET patients as well as isolated ACLR patients or ACLR with LET patients analyzed separately. DISCUSSION: The main finding of this study was that there was a significant positive correlation between preoperative QPS and total AP tibial translation at 12 months postoperatively in the contralateral, healthy extremity. There were no significant correlations between preoperative QPS and postoperative in vivo kinematics at 6 and 12 months following ACLR with or without LET. This suggests that QPS as measured with PIVOT technology does correlate with healthy in vivo knee kinematics, but QPS does not correlate with in vivo kinematics following ACLR with or without LET.