Testing with cadaveric foot and ankle specimens began as mechanical techniques to study foot function and then evolved into static simulations of specific instances of gait, before technologies were ...eventually developed to fully replicate the gait cycle. This article summarizes the clinical applications of dynamic cadaveric gait simulation, including foot bone kinematics and joint function, muscle function, ligament function, orthopaedic foot and ankle pathologies, and total ankle replacements. The literature was reviewed and an in-depth summary was written in each section to highlight one of the more sophisticated simulators. The limitations of dynamic cadaveric simulation were also reviewed.
Abstract Diabetic subjects are at an increased risk of developing plantar ulcers. Knowledge of the physiologic compressive properties of the plantar soft tissue is critical to understanding the ...possible mechanisms of ulcer formation and improving treatment options. The purpose of this study was to determine the compressive mechanical properties of the plantar soft tissue in both diabetic and non-diabetic specimens from six relevant locations beneath the foot, namely the hallux (big toe), first, third, and fifth metatarsal heads, lateral midfoot, and calcaneus (heel). Cylindrical specimens (1.905 cm diameter) from these locations were excised and separated from the skin and bone from 4 diabetic and 4 non-diabetic age-matched, elderly, fresh-frozen cadaveric feet. Specimens were then subjected to biomechanically realistic strains of ∼50% in compression using triangle wave tests conducted at five frequencies ranging from 1 to 10 Hz to determine tissue modulus, energy loss, and strain rate dependence. Diabetic vs. non-diabetic results across all specimens, locations, and testing frequencies demonstrated altered mechanical properties with significantly increased modulus (1146.7 vs. 593.0 kPa) but no change in energy loss (68.5 vs. 67.9%). All tissue demonstrated strain rate dependence and tissue beneath the calcaneus was found to have decreased modulus and energy loss compared to other areas. The results of this study could be used to generate material properties for all areas of the plantar soft tissue in diabetic or non-diabetic feet, with implications for foot computational modeling efforts and potentially for pressure alleviating footwear that could reduce plantar ulcer incidence.
Plantar pressure, a common gait and foot biomechanics measurement, is typically analyzed using proprietary commercial software packages. Regional plantar pressure analysis is often reported in terms ...of underlying bony geometry, and recent advances in image processing and accessibility have made computed tomography, radiographs, magnetic resonance imaging, or other imaging methods more popular for incorporating bone analyses in biomechanics.
Can a computed tomography-based regional mask provide comparable regional analysis to commercial plantar pressure software and can the increased flexibility of an in-house method obtain additional insight from common measurements?
A plantar pressure analysis method was developed based on bony geometry from computed tomography scans to calculate peak pressure, pressure time integral incorporating sub-peak values, force time integral, pressure gradient, and pressure gradient angle. Static and dynamic plantar pressure were acquired for 4 subjects (male, 65 ± 2.4 years). Plantar pressure variables were calculated using commercial and computed tomography-based systems.
Dynamic peak pressure, pressure time integral, and force-time integral computed using the bone-based software was 5 % (9kPa), 7 % (0.3kPa-s) and 13 % (0.3 N-s) different than the commercial software on average. Region masks of the metatarsals and toes differed between commercial and computed tomography-based software due to subject-specific bone geometry and toe shape. Pressure time integral values incorporating sub-peak pressure were higher and demonstrated higher relative hindfoot values compared to those without. Removing step-on frames to static pressure analysis decreased forefoot pressures. Regional maps of peak pressure and maximum pressure gradient demonstrate different peak locations.
Computed tomography-based regional masks are comparable to commercial masks. Inclusion of static step-on frames and sub-peak pressures may change regional plantar pressure patterns. Differences in location of maximum pressure gradient and peak pressure may be useful for assessing subject specific injury risk.
•Plantar pressure masks can be automatically generated from computed tomography•Locations of peak pressure gradients and peak pressures may be different•Including sub-peak pressures in pressure-time integral may change regional trends
IMPORTANCE: The natural progression of symptom change and recovery remains poorly defined in children after concussion. OBJECTIVES: To describe the natural progression of symptom change by age group ...(5-7, 8-12, and 13-18 years) and sex, as well as to develop centile curves to inform families about children after injury recovery. DESIGN, SETTING, AND PARTICIPANTS: Planned secondary analysis of a prospective multicenter cohort study (Predicting Persistent Postconcussive Problems in Pediatrics). The setting was 9 pediatric emergency departments within the Pediatric Emergency Research Canada (PERC) network. Participants were aged 5 to 18 years with acute concussion, enrolled from August 1, 2013, to May 31, 2015, and data analyses were performed between January 2018 and March 2018. EXPOSURES: Participants had a concussion consistent with the Zurich Consensus Statement on Concussion in Sport diagnostic criteria and 85% completeness of the Postconcussion Symptom Inventory (PCSI) at each time point. MAIN OUTCOMES AND MEASURES: The primary outcome was symptom change, defined as current rating minus preinjury rating (delta score), at presentation and 1, 2, 4, 8, and 12 weeks after injury, measured using the PCSI. Symptoms were self-rated for ages 8 to 18 years and rated by the child and parent for ages 5 to 7 years. The secondary outcome was recovery, defined as no change in symptoms relative to current preinjury PCSI ratings (delta score = 0). Mixed-effects models incorporated the total score, adjusting for random effects (site and participant variability), fixed-effects indicators (age, sex, time, age by time interaction, and sex by time interaction), and variables associated with recovery. Recovery centile curves by age and sex were computed. RESULTS: A total of 3063 children (median age, 12.0 years interquartile range, 9.2-14.6 years; 60.7% male) completed the primary outcome; 2716 were included in the primary outcome analysis. For the group aged 5 to 7 years, symptom change primarily occurred the first week after injury; by 2 weeks, 75.6% of symptoms had improved (PCSI change between 0 and 2 weeks, −5.3; 95% CI, −5.5 to −5.0). For the groups aged 8 to 12 years and 13 to 18 years, symptom change was prominent the first 2 weeks but flattened between 2 and 4 weeks. By 4 weeks, 83.6% and 86.2% of symptoms, respectively, had improved for the groups aged 8 to 12 years (PCSI change between 0 and 4 weeks, −9.0; 95% CI, −9.6 to −8.4) and 13 to 18 years (PCSI change between 0 and 4 weeks, −28.6; 95% CI, −30.8 to −26.3). Sex by time interaction was significant only for the adolescent group (β = 0.32; 95% CI, 0.21-0.43; P < .001). Most adolescent girls had not recovered by week 12. CONCLUSIONS AND RELEVANCE: Symptom improvement primarily occurs in the first 2 weeks after concussion in children and in the first 4 weeks after concussion in preadolescents and male adolescents. Female adolescents appear to have protracted recovery. The derived recovery curves may be useful for evidence-based anticipatory guidance.
Presently, developments in weightbearing computed tomography and biplanar fluoroscopy technologies offer exciting avenues for investigating normative and pathologic foot function with increasing ...precision. Still, data quantifying sesamoid bone and proximal phalange motion are currently sparse. To express joint kinematics and compare various clinical cohorts, future studies of first ray motion will necessitate robust coordinate frames that respect the variations in underlying anatomy while also aligning closely with the functional, physiological axes of motion. These activity-dependent functional axes may be represented by a mean helical axis of the joint motion. Our cadaveric study quantified joint kinematics from weightbearing computed tomography scans during simulated toe lift and heel rise tasks. We compared the spatial orientations of the mean finite helical axes of the metatarsosesamoidal and metatarsophalangeal joints to the primary joint axis of two relevant methods for defining metatarsal coordinate frames: inertial axes and fitting of geometric primitives. The resultant kinematics exhibited less crosstalk when using a metatarsal coordinate system based on fitting cylindrical primitives to the bony anatomy compared to using principal component axes. Respective metatarsophalangeal and metatarsosesamoidal arthrokinematic contact paths and instantaneous centers of rotation were similar between activities and agree well with currently published data. This study outlines a methodology for quantitatively assessing the efficacy and utility of various anatomical joint coordinate system definitions. Improvements in our ability to characterize the shape and motion of foot bones in the context of functional tasks will elucidate their biomechanical roles and aid clinicians in refining treatment strategies.
The rate of total ankle arthroplasty (TAA) is increasing relative to ankle arthrodesis (AA) for patients seeking surgical treatment for end-stage ankle arthritis. Patients and providers would benefit ...from a more complete understanding of the rate of improvement, the average length of time to achieve maximal function and minimal pain, and whether there is a greater decline in function or an increase in pain over time following TAA compared with AA. The objectives of this study were to compare treatment changes in overall physical and mental function and ankle-specific function, as well as pain intensity at 48 months after TAA or AA in order to determine if the improvements are sustained.
This was a multisite prospective cohort study that included 517 participants (414 TAA and 103 AA) who presented for surgical treatment. Participants were compared 48 months after surgery using the Foot and Ankle Ability Measure (FAAM) Activities of Daily Living and Sports subscales (0 to 100 points), the Short Form-36 (SF-36) Physical and Mental Component Summary (PCS and MCS) scores (0 to 100 points), and pain scores (0 to 10 points).
Both groups achieved significant improvement in the 2 FAAM measures, the SF-36 PCS score, and all of the pain measures at 48 months after surgey (p < 0.001). Mean improvements from baseline in patients undergoing TAA for the FAAM Activities of Daily Living, FAAM Sports, and SF-36 scores were at least 9 points, 8 points, and 3.5 points, respectively, which were higher than in those undergoing AA. Mean improvements in worst and average pain were at least 0.9 point higher in patients undergoing TAA than in those undergoing AA at 12, 24, and 36 months. These differences were attenuated by 48 months. For both treatments, all improvements from baseline to 24 months had been maintained at 48 months.
When both procedures are performed by the same group of surgeons, patients who undergo TAA or AA for end-stage ankle arthritis have significant improvement in overall function, ankle-specific function, and pain at 48 months after surgery, with better functional improvement in the TAA group.
Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
Weightbearing radiographs are widely used to investigate foot disorders. However, it is unclear how imaging during partial weightbearing affects foot alignment measurements. This study aimed to ...determine a partial weightbearing threshold that yields consistent measurements of various radiographic angles. Eighteen normal fresh‐frozen cadaveric foot specimens were dissected and prepared for mechanical testing using a custom‐designed, computed tomography‐compatible loading frame. Specimens were placed in a neutral ankle position and scanned in five axial loading conditions (0%, 12.5%, 25%, 37.5%, and 50% bodyweight) using weightbearing computed tomography. (Note 50% bodyweight per foot represents full bodyweight in quiet stance.) The lateral first talometatarsal and calcaneal pitch angles were measured on lateral radiographic projections, and the hallux valgus angle and first−second, fourth−fifth, and first−fifth intermetatarsal angles were measured on axial projection images. The lateral first talometatarsal angle decreased significantly with increased bodyweight loading (p < 0.01). Mean significant decreases in the lateral first talometatarsal angle compared to 0% were 6.6° for 12.5%, 7.6° for 25%, 8.8° for 37.5%, and 10.0° for 50% bodyweight loading; 12.5% to 50% was also significant. There was no significant differences between other loading condition pairings or with increased axial load at other angles. The medial longitudinal arch flattened with increasing axial load, resulting in a decreased lateral first talometatarsal angle. However, this radiographic parameter did not change between the 25% and 50% bodyweight conditions, indicating that partial weightbearing imaging (between 12.5% and 25% bodyweight) might be enough to reproduce the sagittal foot alignments observed under full weightbearing conditions in normal feet.
BACKGROUND:Newer designs and techniques of total ankle arthroplasty (TAA) have challenged the assumption of ankle arthrodesis (AA) as the primary treatment for end-stage ankle arthritis. The ...objective of this study was to compare physical and mental function, ankle-specific function, pain intensity, and rates of revision surgery and minor complications between these 2 procedures and to explore heterogeneous treatment effects due to age, body mass index (BMI), patient sex, comorbidities, and employment on patients treated by 1 of these 2 methods.
METHODS:This was a multisite prospective cohort study comparing outcomes of surgical treatment of ankle arthritis. Subjects who presented after nonoperative management had failed received either TAA or AA using standard-of-treatment care and rehabilitation. Outcomes included the Foot and Ankle Ability Measure (FAAM), Short Form-36 (SF-36) Physical and Mental Component Summary (PCS and MCS) scores, pain, ankle-related adverse events, and treatment success.
RESULTS:Five hundred and seventeen participants underwent surgery and completed a baseline assessment. At 24 months, the mean improvement in FAAM activities of daily living (ADL) and SF-36 PCS scores was significantly greater in the TAA group than in the AA group, with a difference between groups of 9 points (95% confidence interval CI = 3, 15) and 4 points (95% CI = 1, 7), respectively. The crude incidence risks of revision surgery and complications were greater in the AA group; however, these differences were no longer significant after adjusting for age, sex, BMI, and Functional Comorbidity Index (FCI). The treatment success rate was greater after TAA than after AA for those with an FCI of 4 (80% versus 62%) and not fully employed (81% versus 58%) but similar for those with an FCI score of 2 (81% versus 77%) and full-time employment (79% versus 78%).
CONCLUSIONS:At 2-year follow-up, both AA and TAA were effective. Improvement in several patient-reported outcomes was greater after TAA than after AA, without a significant difference in the rates of revision surgery and complications.
LEVEL OF EVIDENCE:Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
Abstract Changes in the plantar soft tissue shear properties may contribute to ulceration in diabetic patients, however, little is known about these shear parameters. This study examines the elastic ...and viscoelastic shear behavior of both diabetic and non-diabetic plantar tissue. Previously compression tested plantar tissue specimens ( n =54) at six relevant plantar locations (hallux, first, third, and fifth metatarsal heads, lateral midfoot, and calcaneus) from four cadaveric diabetic feet and five non-diabetic feet were utilized. Per in vivo data (i.e., combined deformation patterns of compression followed by shear), an initial static compressive strain (36–38%) was applied to the tissue followed by target shear strains of 50% and 85% of initial thickness. Triangle waves were used to quantify elastic parameters at both strain levels and a stress relaxation test (0.25 s ramp and 300 s hold) was used to quantify the viscoelastic parameters at the upper strain level. Several differences were found between test groups including a 52–62% increase in peak shear stress, a 63% increase in toe shear modulus, a 47% increase in final shear modulus, and a 67% increase in middle slope magnitude (sharper drop in relaxation) in the diabetic tissue. Beyond a 54% greater peak compressive stress in the third metatarsal compared to the lateral midfoot, there were no differences in shear properties between plantar locations. Notably, this study demonstrates that plantar soft tissue with diabetes is stiffer than healthy tissue, thereby compromising its ability to dissipate shear stresses borne by the foot that may increase ulceration risk.
Talonavicular (TN) fusion is a common treatment for TN arthritis or deformity correction. There is incongruous evidence regarding remaining motion at the talocalcaneal and calcaneocuboid joints after ...TN fusion. Additionally, the effects of a malaligned TN fusion are not well understood and alignment of the fusion may be important for overall foot integrity. This project assessed the kinematic and kinetic effects of neutral and malaligned TN fusions. Ten cadaveric feet were tested on a gait simulator in four conditions: unfused, fused in neutral, fused in varus, and fused in valgus. The fusions were simulated with external fixation hardware. An eight‐camera motion analysis system and a 10‐segment foot model generated kinematic data, and a pressure mat captured pressure data. Simulated TN fusion was achieved in eight feet. From unfused to fused‐neutral, range of motion (ROM) was not eliminated in the adjacent joints, but the positions of the joints changed significantly throughout stance phase. Furthermore, the ROM increased at the tibiotalar joint. Plantar pressure and center of pressure shifted laterally with neutral fusion. The malalignments marginally affected the ROM but changed joint positions throughout stance phase. Pressure patterns were shifted laterally in varus malalignment and medially in valgus malalignment. The residual motion and the altered kinematics at the joints in the triple joint complex after TN fusion may subsequently increase the incidence of arthritis. Clinical significance: This study quantifies the effects of talonavicular fusion and malalignment on the other joints of the triple joint complex.
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