Epigenetic differences in stress response gene FKBP5 among children with abusive vs accidental injuries.

BACKGROUND: Survivors of child abuse experience high rates of adverse physical and mental health outcomes. Epigenetic alterations in the stress response system, the FKBP5 gene specifically, have been implicated as one mechanism that may link abuse to lifelong health issues. Prior studies primarily included older individuals with a remote history of maltreatment; our objective was to test for differential methylation of FKBP5 in children with abusive vs accidental injuries at the time of diagnosis. METHODS: We conducted a cross-sectional pilot study of acutely injured children <4 years old at two children's hospitals (n = 82). Research personnel collected injury histories, buccal swabs (n = 65), and blood samples (n = 25) to measure DNA methylation. An expert panel classified the injuries as abusive, accidental, or indeterminate. RESULTS: Children with abusive as compared to accidental injuries had lower methylation of the FKBP5 promoter in buccal and blood cells, even after controlling for injury severity, socioeconomic status, and psychosocial risk factors. CONCLUSION: These findings suggest that epigenetic variation in FKBP5 may occur at the earliest indication of abuse and may be associated with delayed resolution of the HPA axis stress response. Additional testing for epigenetic differences in larger sample sizes is needed to further verify these findings. IMPACT: Children (<4 years old) with abusive compared to accidental injuries showed lower methylation of the FKBP5 promoter in buccal and blood cells at the time of initial diagnosis even after controlling for injury severity, socioeconomic status, and psychosocial risk factors. Early childhood physical abuse may impact the epigenetic regulation of the stress response system, including demethylation within promoters and enhancers of the FKBP5 gene, even at the earliest indication of abuse. The findings are important because unmitigated stress is associated with adverse health outcomes throughout the life-course.

Head biomechanics of video recorded falls involving children in a childcare setting.

The objective of this study was to characterize head biomechanics of video-recorded falls involving young children in a licensed childcare setting. Children 12 to < 36 months of age were observed using video monitoring during daily activities in a childcare setting (in classrooms and outdoor playground) to capture fall events. Sensors (SIM G) incorporated into headbands worn by the children were used to obtain head accelerations and velocities during falls. The SIM G device was activated when linear acceleration was ≥ 12 g. 174 video-recorded falls activated the SIM G device; these falls involved 31 children (mean age = 21.6 months ± 5.6 SD). Fall heights ranged from 0.1 to 1.2 m. Across falls, max linear head acceleration was 50.2 g, max rotational head acceleration was 5388 rad/s2, max linear head velocity was 3.8 m/s and max rotational head velocity was 21.6 rad/s. Falls with head impact had significantly higher biomechanical measures. There was no correlation between head acceleration and fall height. No serious injuries resulted from falls-only 1 child had a minor injury. In conclusion, wearable sensors enabled characterization of head biomechanics during video-recorded falls involving young children in a childcare setting. Falls in this setting did not result in serious injury.

Femur morphology in healthy infants and young children.

The objective of this study was to characterize femur morphology in healthy infants and young children. Anterior-posterior (AP) radiographs of the femur from children age 0-3 years with no history of bone disease were obtained from two children's hospitals and one medical examiner's office. Femur morphological measures (bone length, minimum diaphysis diameter, growth plate width, and femur radius of curvature) and sectional structural measures were determined. Measures were described and compared based on subject age and mass. Relationships between measures and age and mass were evaluated. The 169 AP femur radiographs were obtained from 99 children (59.6% males, median age = 12.0 months, IQR = 0-27.5 months, median body weight = 10.0 kg, IQR = 4.4-15.6 kg). Femur length (rs  = 0.97, p < 0.001; rs  = 0.89, p < 0.001), trochanter width (rs  = 0.86, p < 0.001; rs  = 0.85, p < 0.001), minimum diaphysis diameter (rs  = 0.91, p < 0.001; rs  = 0.87, p < 0.001), and growth plate width (rs  = 0.91, p < 0.001; rs  = 0.84, p < 0.001) increased with age and weight, respectively. Cross-sectional area (rs  = 0.87; rs  = 0.86; p < 0.01), polar moment of inertia (rs  = 0.91; rs  = 0.87; p < 0.001), moment of inertia (rs  = 0.91; rs  = 0.87; p < 0.001), polar modulus (rs  = 0.91; rs  = 0.87; p < 0.001) and medullary canal diameter (rs  = 0.83, p < 0.001; rs  = 0.73, p < 0.001) at the minimum diaphysis also increased with age and weight, respectively. Changes during rapid bone growth are important to understanding fracture risk in infants and young children as they transition to independent walking. Femur length, trochanter width, minimum diaphysis diameter and growth plate width increased with age and weight. Structural properties associated with fracture resistance also increased with age and weight.

Validation of a Clinical Decision Rule to Predict Abuse in Young Children Based on Bruising Characteristics.

Importance: Bruising caused by physical abuse is the most common antecedent injury to be overlooked or misdiagnosed as nonabusive before an abuse-related fatality or near-fatality in a young child. Bruising occurs from both nonabuse and abuse, but differences identified by a clinical decision rule may allow improved and earlier recognition of the abused child. Objective: To refine and validate a previously derived bruising clinical decision rule (BCDR), the TEN-4 (bruising to torso, ear, or neck or any bruising on an infant <4.99 months of age), for identifying children at risk of having been physically abused. Design, Setting, and Participants: This prospective cross-sectional study was conducted from December 1, 2011, to March 31, 2016, at emergency departments of 5 urban children's hospitals. Children younger than 4 years with bruising were identified through deliberate examination. Statistical analysis was completed in June 2020. Exposures: Bruising characteristics in 34 discrete body regions, patterned bruising, cumulative bruise counts, and patient's age. The BCDR was refined and validated based on these variables using binary recursive partitioning analysis. Main Outcomes and Measures: Injury from abusive vs nonabusive trauma was determined by the consensus judgment of a multidisciplinary expert panel. Results: A total of 21 123 children were consecutively screened for bruising, and 2161 patients (mean [SD] age, 2.1 [1.1] years; 1296 [60%] male; 1785 [83%] White; 1484 [69%] non-Hispanic/Latino) were enrolled. The expert panel achieved consensus on 2123 patients (98%), classifying 410 (19%) as abuse and 1713 (79%) as nonabuse. A classification tree was fit to refine the rule and validated via bootstrap resampling. The resulting BCDR was 95.6% (95% CI, 93.0%-97.3%) sensitive and 87.1% (95% CI, 85.4%-88.6%) specific for distinguishing abuse from nonabusive trauma based on body region bruised (torso, ear, neck, frenulum, angle of jaw, cheeks [fleshy], eyelids, and subconjunctivae), bruising anywhere on an infant 4.99 months and younger, or patterned bruising (TEN-4-FACESp). Conclusions and Relevance: In this study, an affirmative finding for any of the 3 BCDR TEN-4-FACESp components in children younger than 4 years indicated a potential risk for abuse; these results warrant further evaluation. Clinical application of this tool has the potential to improve recognition of abuse in young children with bruising.

Investigation of femur fracture potential in common pediatric falls using finite element analysis.

A finite element (FE) model of an 11-month-old child's femur was developed to evaluate fracture risk in short-distance feet-first falls and bed falls. Pediatric material properties were applied to the FE model. Femur loading was derived from previously conducted fall experiments using a child surrogate where fall conditions (e.g., fall height, impact surface) were varied. Fracture thresholds based on principal stress and strain were used to examine potential for fracture. Peak stress/strain were significantly greater for feet-first falls from greater heights and onto harder impact surfaces. Feet-first falls exceeded some, but not all fracture thresholds. Bed falls did not exceed any fracture thresholds.

Ramps remain a barrier to safe wheelchair user transit bus ingress/egress.

Background: Wheelchair users (WCUs) often rely on ramps for access to transit buses. Previous studies indicate WCUs have difficulty using ramps for bus ingress/egress and many transportation-related incidents occur on ramps. However, experiences of WCU ramp usage during ingress/egress have not been fully described.Methods: Cross-sectional, internet-based survey of WCUs who ride transit buses was conducted. The participants were queried on frequency of bus usage, difficulty and incidents involving ramps, and factors contributing to difficulty and incidents. Wheelchair characteristics, primary condition, and whether participants received travel training were also captured. Chi-square was used to describe relationships between wheelchair type and frequency of difficulties and incidents, and odd ratios were used to determine likelihood of the incidents.Results: The majority (55.7%) of 384 participants reported using public transportation ≥ 1 per week. Seventy-eight percent of WCUs had ≥ 1 ramp incident over the past 3 years, with an increased likelihood of incidents occurring during ingress (OR = 1.53; CI 1.21-1.86). Of those who had an incident, 22% were injured or had damage to their wheelchair. Over 60% of those who had an incident identified steep ramp slope as being the contributing factor. Steep ramp slope, exterior ramp thresholds and wet surfaces were the most common contributing factors to difficulty using ramps.Conclusion: This is the first large-scale US study enabling WCUs to describe their experiences using transit bus ramps. Despite ADA guidelines, steep ramps remain the primary factor contributing to incidents and difficulty when using ramps to access transit buses.Implications for rehabilitationThe discrepancy between ADA maximum allowable ramp slopes for the built environment and transit buses may require an increased level of effort that is a barrier to transportation accessibility for some wheelchair users.Wheelchair users who access transit buses should be made aware of, and trained, to navigate ramp configurations found in the environment.We suggest rehabilitation therapists provide skills training specific to navigating transit bus ramp slopes that may be steeper and narrower than building ramps.

Long bone fracture characteristics in children with medical conditions linked to bone health.

BACKGROUND: Knowledge of fracture characteristics among children with medical conditions affecting bone could help to distinguish medical causes from child abuse. OBJECTIVE: Characterize long bone fracture morphology among children diagnosed with medical conditions linked to bone health. PARTICIPANTS AND SETTING: Patients <18 years at a single pediatric hospital diagnosed with a medical condition linked to bone health and ≥1 long bone fracture were studied. METHODS: This retrospective medical record review categorized underlying medical diagnoses as: metabolic bone disease, genetic disorder of connective tissue, neurologic disorder and other chronic disease. A pediatric radiologist reviewed plain films to determine fracture type and location. Descriptive statistics, as well as logistic regression were used to compare fracture types by clinical characteristics. RESULTS: Ninety-four patients were included and their diagnoses were genetic connective disorder (19; 20.2 %), metabolic bone disease (16; 17.0 %), neurologic disorder (27; 28.7 %), and other (32; 34.0 %). A total of 216 long bone fractures were sustained; 52.1 % of children had >1 long bone fracture. Of the 216 fractures, 55 (25.5 %) were in children < 1 year, 118 (54.6 %) were associated with known trauma, and 122 (56.5 %) were in non-ambulatory patients. Lower extremity fractures occurred with greatest frequency and most fractures occurred at the mid-diaphysis. Transverse was the most common fracture type in all diagnostic categories. Children with metabolic disorders had highest odds of transverse fracture (COR 3.55, CI 1.45-8.67; neurologic disorders as reference group). CONCLUSIONS: Diseases affecting bone health can influence fracture morphology. Transverse fractures were most common in bones impacted by disease.

Development of a Canine Rigid Body Musculoskeletal Computer Model to Evaluate Gait.

BACKGROUND: Kinematic and kinetic analysis have been used to gain an understanding of canine movement and joint loading during gait. By non-invasively predicting muscle activation patterns and forces during gait, musculoskeletal models can further our understanding of normal variability and muscle activation patterns and force profiles characteristic of gait. METHODS: Pelvic limb kinematics and kinetics were measured for a 2 year old healthy female Dachshund (5.4 kg) during gait using 3-D motion capture and force platforms. A computed tomography scan was conducted to acquire pelvis and pelvic limb morphology. Using the OpenSim modeling platform, a bilateral pelvic limb subject-specific rigid body musculoskeletal computer model was developed. This model predicted muscle activation patterns, muscle forces, and angular kinematics and joint moments during walking. RESULTS: Gait kinematics determined from motion capture matched those predicted by the model, verifying model accuracy. Primary muscles involved in generating joint moments during stance and swing were predicted by the model: at mid-stance the adductor magnus et brevis (peak activation 53.2%, peak force 64.7 N) extended the hip, and stifle flexor muscles (biceps femoris tibial and calcaneal portions) flexed the stifle. Countering vertical ground reaction forces, the iliopsoas (peak activation 37.9%, peak force 68.7 N) stabilized the hip in mid-stance, while the biceps femoris patellar portion stabilized the stifle in mid-stance and the plantar flexors (gastrocnemius and flexor digitorum muscles) stabilized the tarsal joint during early stance. Transitioning to swing, the iliopsoas, rectus femoris and tensor fascia lata flexed the hip, while in late swing the adductor magnus et brevis impeded further flexion as biceps femoris tibial and calcaneal portions stabilized the stifle for ground contact. CONCLUSION: The musculoskeletal computer model accurately replicated experimental canine angular kinematics associated with gait and was used to predict muscle activation patterns and forces. Thus, musculoskeletal modeling allows for quantification of measures such as muscle forces that are difficult or impossible to measure in vivo.

Characteristics of rib fractures in young abused children.

BACKGROUND: The presumed mechanism of rib fractures in abuse is violent grasping of the torso causing anterior-posterior chest compression. We hypothesized an asymmetrical distribution of rib fractures in abused infants given the greater incidence of right-hand dominance within the general population. OBJECTIVE: The objective of this study was to characterize rib fractures in abused children, particularly sidedness; additionally, we evaluated the sidedness of other abusive skeletal fractures. MATERIALS AND METHODS: We reviewed medical records from abused children (0-18 months old) with rib fractures. We also retrospectively reviewed their radiographs to determine characteristics of rib fractures (number, side, rib region, level, acuity) and other skeletal fractures (number, side, location), as well as differences in the distribution of rib and other skeletal fractures. RESULTS: A total of 360 rib fractures were identified on 273 individual ribs involving 78 abused children. Sixty-three children (81%) had multiple rib fractures. There was a significantly greater number of left-side rib fractures (67%) than right-side fractures (P<0.001). Fractures were most often identified in the posterior and lateral regions and mid level of the ribcage (Ribs 5 through 8). Fifty-four percent of subjects had other skeletal fractures; these non-rib fractures were also predominantly on the left side (P=0.006). CONCLUSION: In our study of abused children, there was a higher incidence of rib fractures in the posterior, lateral and mid-level locations. Additionally, we found a predominance of left-side rib and other skeletal fractures. Further research is needed to understand whether factors such as perpetrator handedness are associated with these unequal distributions of fractures in abused children.

Retraction Note to: Radiographic characteristics that delineate abusive from accidental skull fractures, including the significance of fracture extension to sutures.

The authors have retracted the abstract #029 "Radiographic characteristics that delineate abusive from accidental skull fractures, including the significance of fracture extension to sutures".

Manual wheelchair propulsion on ramp slopes encountered when boarding public transit buses.

Objective: To compare the kinetics of manual wheelchair (MWC) propulsion on ramps of varying slopes that may be encountered when accessing large accessible transit vehicles (LATVs). Design: Observational study. Setting: Biomechanics research laboratory. Participants: A convenience sample of able-bodied adults (n = 7) having no propulsion experience propelled a MWC on ramps of slope 3.5°, 9.5° and 15°. Interventions: Not applicable. Main outcome measures: Resultant (Fres), radial (Fr) and tangential (Ft) forces applied to the wheelchair pushrim, rate of rise of resultant force (ROR), peak power output (P), temporal characteristics and thigh to trunk angle were analyzed across three ramp slopes. Results: Pushrim forces and power output significantly increased with increasing slope, with peak Fres more than doubling from 107 N on a 3.5° slope to 230 N on a 15° slope. ROR was 1.76 times higher at 9.5° and 2.47 times higher at 15° compared to a 3.5° slope. Minimum thigh to trunk angle decreased sharply from 80° (3.5° slope) to 50° (9.5° slope) and then to 30° (15° slope) as ramp slope increased. Conclusions: Ascending bus ramps require greater power and pushrim force on steeper ramp slopes, presenting a potential barrier to transportation accessibility. Given this finding, it is imperative that bus operators minimize ramp slope to assure MWC users are able to access LATVs. Implications for Rehabilitation Although transit bus ramps are intended to provide wheelchair access to public transportation, limitations in MWC user physical strength and function may prevent safe access. Transit bus ramp slopes encountered during ingress can present a challenge to MWC users given power output and pushrim force requirements to ascend the ramp. MWC users and therapists should be aware of ramp slopes that may be encountered when boarding transit buses; wheelchair training should incorporate skills needed to ascend transit bus ramps.

A three dimensional multiplane kinematic model for bilateral hind limb gait analysis in cats.

BACKGROUND: Kinematic gait analysis is an important noninvasive technique used for quantitative evaluation and description of locomotion and other movements in healthy and injured populations. Three dimensional (3D) kinematic analysis offers additional outcome measures including internal-external rotation not characterized using sagittal plane (2D) analysis techniques. METHODS: The objectives of this study were to 1) develop and evaluate a 3D hind limb multiplane kinematic model for gait analysis in cats using joint coordinate systems, 2) implement and compare two 3D stifle (knee) prediction techniques, and 3) compare flexion-extension determined using the multiplane model to a sagittal plane model. Walking gait was recorded in 3 female adult cats (age = 2.9 years, weight = 3.5 ± 0.2 kg). Kinematic outcomes included flexion-extension, internal-external rotation, and abduction-adduction of the hip, stifle, and tarsal (ankle) joints. RESULTS: Each multiplane stifle prediction technique yielded similar findings. Joint angles determined using markers placed on skin above bony landmarks in vivo were similar to joint angles determined using a feline hind limb skeleton in which markers were placed directly on landmarks ex vivo. Differences in hip, stifle, and tarsal joint flexion-extension were demonstrated when comparing the multiplane model to the sagittal plane model. CONCLUSIONS: This multiplane cat kinematic model can predict joint rotational kinematics as a tool that can quantify frontal, transverse, and sagittal plane motion. This model has multiple advantages given its ability to characterize joint internal-external rotation and abduction-adduction. A further, important benefit is greater accuracy in representing joint flexion-extension movements.

Femur loading in feet-first fall experiments using an anthropomorphic test device.

BACKGROUND: Femur fractures are a common orthopedic injury in young children. Falls account for a large portion of accidental femur fractures in young children, but there is also a high prevalence of femur fractures in child abuse, with falls often provided as false histories. Objective information regarding fracture potential in short distance fall scenarios may aid in assessing whether a child's injuries are the result of abuse or an accidental fall. Knowledge of femur loading is the first step towards understanding likelihood of fracture in a fall. OBJECTIVE: Characterize femur loading during feet-first free falls using a surrogate representing a 12-month-old child. METHODS: The femur and hip joint of a surrogate representing a 12-month-old were modified to improve biofidelity and measure femur loading; 6-axis load cells were integrated into the proximal and distal femur. Femur modification was based upon CT imaging of cadaveric femurs in children 10-14 months of age. Using the modified 12-month-old surrogate, feet-first free falls from 69 cm and 119 cm heights onto padded carpet and linoleum were conducted to assess fall dynamics and determine femur loading. Femur compression, bending moment, shear and torsional moment were measured for each fall. RESULTS: Fall dynamics differed across fall heights, but did not substantially differ by impact surface type. Significant differences were found in all loading conditions across fall heights, while only compression and bending loads differed between carpet and linoleum surfaces. Maximum compression, bending, torsion and shear occurred in 119 cm falls and were 572 N, 23 N-m, 11 N-m and 281 N, respectively. CONCLUSIONS: Fall dynamics play an important role in the biomechanical assessment of falls. Fall height was found to influence both fall dynamics and femur loading, while impact surface affected only compression and bending in feet-first falls; fall dynamics did not differ across carpet and linoleum. Improved pediatric thresholds are necessary to predict likelihood of fracture, but morphologically accurate representation of the lower extremity, along with accurate characterization of loading in falls are a crucial first step.

Classifying Injuries in Young Children as Abusive or Accidental: Reliability and Accuracy of an Expert Panel Approach.

OBJECTIVE: To assess interrater reliability and accuracy of an expert panel in classifying injuries of patients as abusive or accidental based on comprehensive case information. STUDY DESIGN: Data came from a prospective, observational, multicenter study investigating bruising characteristics of children younger than 4 years. We enrolled 2166 patients with broad ranges of illnesses and injuries presenting to one of 5 pediatric emergency departments in whom bruises were identified during examination. We collected comprehensive data regarding current and past injuries and illnesses, and provided deidentified, standardized case information to a 9-member multidisciplinary panel of experts with extensive experience in pediatric injury. Each panelist classified cases using a 5-level ordinal scale ranging from definite abuse to definite accident. Panelists also assessed whether report to child protective services (CPS) was warranted. We calculated reliability coefficients for likelihood of abuse and decision to report to CPS. RESULTS: The interrater reliability of the panelists was high. The Kendall coefficient (95% CI) for the likelihood of abuse was 0.89 (0.87, 0.91) and the kappa coefficient for the decision to report to CPS was 0.91 (0.87, 0.94). Reliability of pairs and subgroups of panelists were similarly high. A panel composite classification was nearly perfectly accurate in a subset of cases having definitive, corroborated injury status. CONCLUSIONS: A panel of experts with different backgrounds but common expertise in pediatric injury is a reliable and accurate criterion standard for classifying pediatric injuries as abusive or accidental in a sample of children presenting to a pediatric emergency department.

Impact sites representing potential bruising locations associated with bed falls in children.

Bruising can occur as a result of accidental or abusive trauma in children. Bruises are an early sign of child abuse and their locations on the body can be an effective delineator of abusive trauma. Since falls are often reported as false histories in abuse, the ability to predict potential bruising locations in falls could be valuable when attempting to differentiate between abuse and accident. In our study we used an anthropomorphic test device (ATD), a surrogate representing a 12 month old child, adapted with a custom developed force sensing skin to predict potential bruising locations during simulated bed falls. The sensing skin is made of custom resistive force sensors integrated into a conformable skin, adapted to fit the contours of the ATD. The sensing skin measured and displayed recorded force data on a computerized body image mapping system when sensors were activated. Simulated bed fall experiments were performed from two initial positions (FF - facing forward and FR - facing rearward) and two fall heights of 61cm (24 in) and 91cm (36 in) onto a padded carpet impact surface. Findings indicated potential bruising primarily in two planes of the ATD body. The majority of contact regions and greater forces were recorded in one plane, with fewer regions of contact and decreased force exhibited in an adjoining second plane. Additionally, no contact was recorded in the two planes opposite the impact planes. Differences in contact regions were observed for varying heights and initial position. Limitations of ATD biofidelity and soft tissue properties must be considered when interpreting these findings.

Wheelchair tiedown and occupant restraint practices in paratransit vehicles.

The purpose of this study was to characterize wheelchair tiedown and occupant restraint system (WTORS) usage in paratransit vehicles based on observations of wheelchair and scooter (wheeled mobility devices, collectively, "WhMD") passenger trips. A retrospective review of on-board video monitoring recordings of WhMD trips was conducted. Four hundred seventy-five video recordings were collected for review and analysis. The use of all four tiedowns to secure the WhMD was observed more frequently for power WhMDs (82%) and manual WhMDs (80%) compared to scooters (39%), and this difference was significant (p< 0.01). Nonuse or misuse of the occupant restraint system occurred during 88% of WhMD trips, and was most frequently due to vehicle operator neglect in applying the shoulder belt. Despite the absence of incidents or injuries in this study, misuse and nonuse of WTORS potentially place WhMD seated passengers at higher risk of injury during transit. These findings support the need for improved vehicle operator training and passenger education on the proper use of WTORS and development of WTORS with improved usability and/or alternative technologies that can be automated or used independently.

Femur fracture biomechanics and morphology associated with torsional and bending loading conditions in an in vitro immature porcine model.

PURPOSE: The objectives of this study were to describe fracture morphology resulting from common loading mechanisms such as bending and torsion in immature bone and to identify differences in the energy required to produce various fracture types under these two loading mechanisms using an immature porcine animal model. METHODS: Twenty-six in vitro immature porcine femora were mechanically tested in 3-point-bending and torsion. Femur specimens were tested with and without soft tissue and at both quasi-static and dynamic loading rates. Bone geometry and density measures were determined for each femur using dual-energy x-ray absorptiometry and plain film x-rays. Failure load, stiffness, and energy to failure were determined for each specimen from the load-displacement history from mechanical tests. RESULTS: 3-point bending tests resulted in 10 transverse fractures and 2 oblique fractures. Torsion tests resulted in spiral fractures. Mean energy required to produce transverse fractures (3.32 Nm) was double that associated with spiral fractures (1.66 Nm). In bending, specimens with soft tissue intact required significantly greater energy to fracture (4.40 Nm) than specimens with soft tissue removed (2.92 Nm). Torsional loading rate did not significantly affect energy to fracture. CONCLUSIONS: Fracture morphology is dependent upon loading conditions. Energy to failure allows for comparison across various loading conditions, and thus offers an effective means of characterizing fracture thresholds for a wide range of scenarios. Consideration should be given to whether or not soft tissue is left intact when conducting experiments using whole bone specimens given its influence on energy to failure.

Canine cranial cruciate ligament deficient stifle biomechanics associated with extra-articular stabilization predicted using a computer model.

OBJECTIVE: To evaluate lateral fabellotibial suture (LFTS) and TightRope CCL (TR) extra-articular stabilization biomechanics in the cranial cruciate ligament (CrCL)-deficient canine stifle joint during the stance phase of gait. STUDY DESIGN: Computer simulations. ANIMALS: Healthy 33-kg Golden Retriever. METHODS: LFTS and TR were implemented in a previously developed 3-D quasi-static rigid body CrCL-deficient canine pelvic limb computer model simulating the stance phase of gait. Ligament loads, relative tibial translation, and relative tibial rotation were determined and compared across the CrCL-intact, CrCL-deficient, and extra-articular stabilized stifle joints. RESULTS: Compared to the CrCL-intact stifle, peak caudal cruciate and lateral collateral ligament (LCL) loads were increased in the LFTS-managed stifle, peak caudal cruciate and LCL loads were decreased in the TR-managed stifle, and peak medial collateral and patellar ligament (PL) loads were similar for both techniques. Compared to the CrCL-deficient stifle, peak caudal cruciate, lateral collateral, and medial collateral ligament loads decreased, and peak PL load was similar in the LFTS- and TR-managed stifle joints. Peak relative tibial translation decreased, and peak relative tibial rotation changed from internal rotation to external rotation in the LFTS- and TR-managed stifle joints compared to the CrCL-deficient stifle. CONCLUSION: Our computer model predicted controlled tibial translation, decreased cruciate and collateral ligament loads, and a change in femorotibial rotation from internal to external with LFTS and TR stifle management as compared to the CrCL-deficient stifle. This study demonstrates how computer modeling can be used to evaluate biomechanics of stifle stabilization surgical techniques.