Recommendation of minimal distal tibial length for long axis coordinate system definitions

Accurate anatomical coordinate systems for the foot and ankle are critical for interpreting their complex biomechanics. The tibial superior-inferior axis is crucial for analyzing joint kinematics, influencing bone motion analysis during gait using CT imaging and biplane fluoroscopy. However, the lack of consensus on how to define the tibial axis has led to variability in research, hindering generalizability. Even as advanced imaging techniques evolve, including biplane fluoroscopy and weightbearing CT, there exist limitations to imaging the entire foot together with the full length of the tibia. These limitations highlight the need to refine axis definitions. This study investigated various superior-inferior axes using multiple distal tibia lengths to determine the minimal field of view for representing the full tibia long-axis. Twenty human cadaver tibias were imaged and segmented to generate 3D bone models. Axes were calculated based on coordinate definitions that required user manual input, and a gold standard mean superior-inferior axis was calculated based on the population's principal component analysis axis. Four manually calculated superior-inferior tibial axes groups were established based on landmarks and geometric fittings. Statistical analysis revealed that geometrically fitting a cylinder 1.5 times the mediolateral tibial width, starting 5 cm above the tibial plafond, yielded the smallest angular deviation from the gold standard. From these findings, we recommend a minimum field of view that includes 1.5 times the mediolateral tibial width, starting 5 cm above the tibial plafond for tibial long-axis definitions. Implementing these findings will help improve foot and ankle research generalizability and impact clinical decisions.

The Effect of Knee Height Asymmetry on Gait Biomechanics

BACKGROUND

Though the primary goal for limb length discrepancy (LLD) management is to equalize the leg lengths, symmetry between corresponding long bones is usually not achieved, leading to knee height asymmetry (KHA). To date, there is minimal information on what effect KHA has on gait biomechanics and joint loading. Thus, the purpose of this study is to determine the impact of KHA on gait biomechanics.

METHODS

Seventeen subjects with KHA after limb equalizing surgery and 10 healthy controls were enrolled. Subjects participated in 3D gait analysis collected using self-selected speed. Lower extremity kinematics, kinetics, work generated/absorbed, and total work were calculated. Standing lower limb x-rays and scanograms were used to measure LLD and calculate the tibia-to-femur (TF) ratio for each limb. Two sample t tests were used to compare differences in standing LLD, TF ratio, and work between groups. Bivariate correlation using Pearson correlation coefficients was conducted between TF ratio and total mechanical work, as well as between knee height asymmetry indices and total work asymmetry (α=0.05).

RESULTS

Among participants, there were no differences between LLD; however, there were differences between TF ratio and knee height asymmetry. We found a nonsignificant relationship between TF ratio and total mechanical work for individual lower extremities. Therefore, the length of individual bones (TF ratio) relative to each other within the individual lower extremity was not associated with the amount of work produced. However, when a difference exists between sides (asymmetry, ie, TF ratio asymmetry), there were associated differences in work (work asymmetry) produced between sides (r=0.54, P=0.003). In other words, greater knee height asymmetry between limbs resulted in more asymmetrical mechanical work during walking.

CONCLUSIONS

These findings may have implications for the management of LLD. Asymmetrical total mechanical work could lead to atypical joint loading during gait. Surgeons may want to consider prioritizing achieving knee height symmetry as a postoperative goal when correcting limb length discrepancy.

LEVEL OF EVIDENCE

Level III, Case Control Study.

Creating an autoencoder single summary metric to assess gait quality to compare surgical outcomes in children with cerebral palsy: The Shriners Gait Index (SGI)

Gait for individuals with movement disorders varies widely and the variability makes it difficult to assess outcomes of surgical and therapeutic interventions. Although specific joints can be assessed by fewer individual measures, gait depends on multiple parameters making an overall assessment metric difficult to determine. A holistic, summary measure can permit a standard comparison of progress throughout treatments and interventions, and permit more straightforward comparison across varied subjects. We propose a single summary metric (the Shriners Gait Index (SGI)) to represent the quality of gait using a deep learning autoencoder model, which helps to capture the nonlinear statistical relationships among a number of disparate gait metrics. We utilized gait data of 412 individuals under the age of 18 collected from the Motion Analysis Center (MAC) at the Shriners Children's - Chicago. The gait data includes a total of 114 features: temporo-spatial parameters (7), lower extremity kinematics (64), and lower extremity kinetics (43) which were min-max normalized. The developed SGI score captured more than 89% variance of all 144 features using subject-wise cross-validation. Such summary metrics holistically quantify an individual's gait which can then be used to assess the impact of therapeutic interventions. The machine learning approach utilized can be leveraged to create such metrics in a variety of contexts depending on the data available. We also utilized the SGI to compare overall changes to gait after surgery with the goal of improving mobility for individuals with gait disabilities such as Cerebral Palsy.

Automatic anatomical foot and ankle coordinate toolbox

Accurate analysis of bone position and orientation in foot and ankle studies relies on anatomical coordinate systems (ACS). Reliable ACSs are necessary for many biomechanical and clinical studies, especially those including weightbearing computed tomography and biplane fluoroscopy. Existing ACS approaches suffer from limitations such as manual input, oversimplifications, or non-physiological methods. To address these shortcomings, we introduce the Automatic Anatomical Foot and Ankle Coordinate Toolbox (AAFACT), a MATLAB-based toolbox that automates the calculation of ACSs for the major fourteen foot and ankle bones. In this manuscript, we present the development and evaluation of AAFACT, aiming to provide a standardized coordinate system toolbox for foot and ankle studies. The AAFACT was evaluated using a dataset of fifty-six models from seven pathological groups: asymptomatic, osteoarthritis, pilon fracture, progressive collapsing foot deformity, clubfoot, Charcot Marie Tooth, and cavovarus. Three analyses were conducted to assess the reliability of AAFACT. Firstly, ACSs were compared between automatically and manually segmented bone models to assess consistency. Secondly, ACSs were compared between individual bones and group mean bones to assess within-population precision. Lastly, ACSs were compared between the overall mean bone and group mean bones to assess the overall accuracy of anatomical representation. Statistical analyses, including statistical shape modeling, were performed to evaluate the reliability, accuracy, and precision of AAFACT. The comparison between automatically and manually segmented bone models showed consistency between the calculated ACSs. Additionally, the comparison between individual bones and group mean bones, as well as the comparison between the overall mean bone and group mean bones, revealed accurate and precise ACSs calculations. The AAFACT offers a practical and reliable solution for foot and ankle studies in clinical and engineering settings. It accommodates various foot and ankle pathologies while accounting for bone morphology and orientation. The automated calculation of ACSs eliminates the limitations associated with manual input and non-physiological methods. The evaluation results demonstrate the robustness and consistency of AAFACT, making it a valuable tool for researchers and clinicians. The standardized coordinate system provided by AAFACT enhances comparability between studies and facilitates advancements in foot and ankle research.

A multicenter study to evaluate pain characteristics in osteogenesis imperfecta

The objective was to describe pain characteristics and treatments used in individuals with varying severity of osteogenesis imperfecta (OI) and investigate pain-associated variables. This work was derived from a multicenter, longitudinal, observational, natural history study of OI conducted at 12 clinical sites of the NIH Rare Diseases Clinical Research Network's Brittle Bone Disorders Consortium. Children and adults with a clinical, biochemical, or molecular diagnosis of OI were enrolled in the study. We did a cross-sectional analysis of chronic pain prevalence, characteristics, and treatments used for pain relief and longitudinal analysis to find the predictors of chronic pain. We included 861 individuals with OI, in 41.8% chronic pain was present, with similar frequency across OI types. Back pain was the most frequent location. Nonsteroidal anti-inflammatory drugs followed by bisphosphonates were the most common treatment used. Participants with chronic pain missed more days from school or work/year and performed worse in all mobility metrics than participants without chronic pain. The variables more significantly associated with chronic pain were age, sex, positive history of rodding surgery, scoliosis, other medical problems, assistive devices, lower standardized height, and higher body mass index. The predictors of chronic pain for all OI types were age, use of a wheelchair, and the number of fractures/year. Chronic pain is prevalent in OI across all OI types, affects mobility, and interferes with participation. Multiple covariates were associated with chronic pain.

Multi-segment foot kinematics during gait following ankle arthroplasty

Ankle arthritis is a debilitating disease marked by pain and limited function. Total ankle arthroplasty improves pain while preserving motion and offers an alternative to the traditional treatment of ankle fusion. Gait analysis and functional outcomes tools can provide an objective balanced analysis of ankle replacement for the treatment of ankle arthritis. Twenty-nine patients with end-stage ankle arthritis were evaluated before and after ankle arthroplasty. Multi-segment foot and ankle kinematics were assessed annually following surgery (average 3.5 years, range 1-6 years) using the Milwaukee Foot Model and a Vicon video motion analysis system. Functional outcomes (American Orthopedic Foot and Ankle Society [AOFAS] ankle/hindfoot scale, short form 36 [SF-36] questionnaire) and temporal-spatial parameters were also assessed. Kinematic results were compared to findings from a previously collected group of healthy ambulators. AOFAS and SF-36 mean scores improved postoperatively. Walking speed and stride length increased after surgery. There were significant improvements in tibial sagittal range of motion in terminal stance and hindfoot sagittal range of motion in preswing. Decreased external rotation of the tibia and increased external rotation of the hindfoot were noted throughout the gait cycle. Pain and function improved after ankle replacement as supported by better outcomes scores, increased temporal-spatial parameters, and significant improvement in tibial sagittal range of motion during terminal stance and hindfoot sagittal range of motion during preswing. While multi-segment foot kinematics were improved, they were not restored to control values. Statement of clinical significance: Total ankle arthroplasty does not fully normalize mutli-segment gait kinematics despite improved patient-reported outcomes and gait mechanics.

What are the long-term outcomes of lateral column lengthening for pes planovalgus in cerebral palsy?

BACKGROUND

Lateral column lengthening (LCL) is commonly performed on children and adolescents with cerebral palsy (CP) for correction of pes planovalgus (PPV). There are limited reports of the long-term outcomes of this procedure. The purpose of this study was to examine the long-term results of LCL for correction of PPV in individuals with CP by evaluating subjects when they had transitioned to adulthood and were entering the workforce.

METHODS

Clinical assessments, quantitative gait analysis including the Milwaukee Foot Model (MFM) for segmental foot kinematics, and patient reported outcomes were collected from 13 participants with CP treated with LCL for PPV in childhood (average age 24.4 ± 5.7 years, average 15.3 ± 8.5 years since LCL). Additionally, 27 healthy adults average age 24.5 ± 3.6 years functioned as controls.

RESULTS

Strength and joint range of motion were reduced in the PPV group (p < 0.05). Sixty nine percent showed operative correction of PPV based on radiologic criteria. Gait analysis showed reduced walking speed and stride length, as well as midfoot break and residual forefoot abduction. Patient reported outcomes indicated that foot pain was not the only factor that caused limited activity and participation. LCL surgery for PPV in childhood resulted in long-term operative correction. Decreased ankle passive range of motion and strength, subtalar joint arthritic changes, inefficient and less stable ambulation, and problems with participation (difficulties in physical function, education, and employment) were observed in the long-term.

CONCLUSION

This study identified postoperative impairments and limitations to guide future clinical decision-making. These results provide clinicians and researchers the common residual and recurrent issues for these individuals as they age. The inclusion of contextual factors that influence the disease and impairments can equip these individuals with enhanced skills they need as they transition into adulthood.

Gait Characteristics in Youth With Transverse Myelitis

Background

Transverse myelitis (TM) in childhood is a rare disorder characterized by the presence of spinal cord inflammation. Gait difficulty in children with TM is common; however, there is a paucity of literature regarding quantitative assessment of gait in children and adolescents with TM.

Objectives

To characterize gait patterns in a cohort of ambulatory children with TM and age-matched, typically developing peers in order to better understand the functional mobility of patients diagnosed with childhood TM.

Methods

This was a retrospective study of 26 ambulatory pediatric patients with a confirmed diagnosis of TM who had undergone three-dimensional, instrumented gait analysis (3D-IGA) at 3 years of age or older. A group of 38 typically developing children served as a control group.

Results

Gait in children with TM was characterized by moderate kinematic deviations as measured by the Gait Deviation Index (GDI) and a crouched gait pattern (p < .001), increased anterior pelvic tilt (p < .001), decreased motion at the knees (p < .001), and a wider base of support (foot progression angle, p < .001). The TM group had a slower walking speed (p < .001), shorter strides (p < .001), and an increased stance phase compared to controls.

Conclusion

Our study results showed moderate kinematic deviations quantified by the GDI. Overall, the gait pattern in the TM population tested had greater hip and knee flexion with wider foot progression angle. Identification of gait characteristics in children with TM is the first step in predicting changes in gait pattern as they mature over time, which may ultimately allow for targeted intervention to maintain their ambulatory function.

Assignment of local coordinate systems and methods to calculate tibiotalar and subtalar kinematics: A systematic review

The introduction of biplane fluoroscopy has created the ability to evaluate in vivo motion, enabling six degree-of-freedom measurement of the tibiotalar and subtalar joints. Although the International Society of Biomechanics defines a standard method of assigning local coordinate systems for the ankle joint complex, standards for the tibiotalar and subtalar joints are lacking. The objective of this systematic review was to summarize and appraise the existing literature that (1) defined coordinate systems for the tibia, talus, and/or calcaneus or (2) assigned kinematic definitions for the tibiotalar and/or subtalar joints. A systematic literature search was developed with search results limited to English Language from 2006 through 2020. Articles were screened by two independent reviewers based on title and abstract. Methodological quality was evaluated using a modified assessment tool. Following screening, 52 articles were identified as having met inclusion criteria. Methodological assessment of these articles varied in quality from 61 to 97. Included articles adopted primary methods for defining coordinate systems that included: (1) anatomical coordinate system (ACS) based on individual bone landmarks and/or geometric shapes, (2) orthogonal principal axes, and (3) interactive closest point (ICP) registration. Common methods for calculating kinematics included: (1) joint coordinate system (JCS) to calculate rotation and translation, (2) Cardan/Euler sequences, and (3) inclination and deviation angles for helical angles. The methods each have strengths and weaknesses. This summarized knowledge should provide the basis for the foot and ankle biomechanics community to create an accepted standard for calculating and reporting tibiotalar and subtalar kinematics.

Do Bisphosphonates Alleviate Pain in Children? A Systematic Review

PURPOSE OF REVIEW

The goal of this systematic review is to analyze the effectiveness of bisphosphonates (BPs) to treat bone pain in children and adolescents who have diseases with skeletal involvement.

RECENT FINDINGS

We included 24 studies (2 randomized controlled trials, 3 non-randomized controlled trials, 10 non-randomized open-label uncontrolled studies, 8 retrospective studies, and 1 study with design not specified). The majority of included studies assessed pain from a unidimensional approach, with pain intensity the most frequently evaluated dimension. Only 38% of studies used validated tools; visual analogue scale was the most frequently employed. BPs were used to alleviate bone pain in a wide variety of pediatrics conditions such as osteogenesis imperfecta, secondary osteoporosis, osteonecrosis related to chemotherapy, chronic non-bacterial osteitis, idiopathic juvenile osteoporosis, unresectable benign bone tumor, and cancer-related pain. Twenty of the 24 studies reported a positive effect of BPs for alleviating pain in different pathologies, but 58% of the studies were categorized as having high risk of bias. Intravenous BPs are helpful in alleviating bone pain in children and adolescents. It is advised that our results be interpreted with caution due to the heterogeneity of the doses used, duration of treatments, and types of pathologies included. In addition, this review shows the paucity of high-quality evidence in the available literature and further research is needed.

TRIAL REGISTRATION

Before the completion of this review, the protocol was registered to PROSPERO (International prospective register of systematic reviews), PROSPERO 2020 ID # CRD42020158316. Available from: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020158316.

A Multicenter Study of Intramedullary Rodding in Osteogenesis Imperfecta

BACKGROUND

Osteogenesis imperfecta (OI), a heritable connective tissue disorder with wide clinical variability, predisposes to recurrent fractures and bone deformity. Management requires a multidisciplinary approach in which intramedullary rodding plays an important role, especially for moderate and severe forms. We investigated the patterns of surgical procedures in OI in order to establish the benefits of rodding. The main hypothesis that guided this study was that rodded participants with moderate and severe OI would have lower fracture rates and better mobility.

METHODS

With data from the Linked Clinical Research Centers, we analyzed rodding status in 558 individuals. Mobility and fracture data in OI Types III and IV were compared between rodded and non-rodded groups. Univariate regression analyses were used to test the association of mobility outcomes with various covariates pertinent to rodding.

RESULTS

Of the individuals with OI, 42.1% had undergone rodding (10.7% of those with Type I, 66.4% with Type III, and 67.3% with Type IV). Rodding was performed more frequently and at a younger age in femora compared with tibiae. Expanding intramedullary rods were used more frequently in femora. In Type III, the rate of fractures per year was significantly lower (p ≤ 0.05) for rodded bones. In Type III, the mean scores on the Gillette Functional Assessment Questionnaire (GFAQ) and Brief Assessment of Motor Function (BAMF) were higher in the rodded group. However, Type-IV non-rodded subjects had higher mean scores in nearly all mobility outcomes. OI type, the use of expanding rods in tibiae, and anthropometric measurements were associated with mobility outcomes scores.

CONCLUSIONS

Current practice in 5 orthopaedic centers with extensive experience treating OI demonstrates that most individuals with moderate and severe types of OI undergo rodding procedures. Individuals with severe OI have improved mobility outcomes and lower fracture rates compared with their non-rodded peers, which suggests that early bilateral rodding benefits OI Type III. Our analysis showed a change in practice patterns in the final years of the study in the severe forms, with earlier and more simultaneous rodding procedures performed.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Effect of Bisphosphonates on Function and Mobility Among Children With Osteogenesis Imperfecta: A Systematic Review

Osteogenesis imperfecta (OI) is a rare genetic connective tissue disorder that results in bone fragility and deformity. Management is multi-disciplinary. Although pharmacologic intervention with bisphosphonates (BP) is a standard of care for individuals with severe OI, no consensus or reviews were found that focus on the effects of bisphosphonates on function and mobility. PubMed, CINAHL, Cochrane Library, Web of Science, and PEDro databases were searched for eligible articles for this review. Methodological quality was assessed using the Cochrane Collaboration's tool for risk of bias. Twenty-six studies (801 children) were reviewed and five showed a low risk of bias. Included studies showed significant variability among clinical protocols for administering BP. Randomized controlled trials did not demonstrate a significant improvement in function and mobility with oral BP administration, while non-randomized open-label uncontrolled studies demonstrated that oral and intravenous BP administration objectively improved function and mobility. The most common outcome measure used by the studies included in this review was the Bleck score. Effect sizes (d = 0.28 - 4.5) varied among studies. This systematic review also summarized the apparent confounding variables affecting results of previous studies and provided suggestions to improve the quality of future studies.

Sagittal subtalar and talocrural joint assessment between barefoot and shod walking: A fluoroscopic study

BACKGROUND

While wearing shoes is common in daily activities, most foot kinematic models report results on barefoot conditions. It is difficult to describe foot position inside shoes. This study used fluoroscopic images to determine talocrural and subtalar motion.

RESEARCH QUESTION

What are the differences in sagittal talocrual and subtalar kinematics between walking barefoot and while wearing athletic walking shoes?

METHODS

Thirteen male subjects (mean age 22.9 ± 2.9 years, mean weight 77.2 ± 6.9 kg, mean height 178.2 ± 3.7 cm) screened for normal gait were tested. A fluoroscopy unit was used to collect images during stance. Sagittal motion of the talocrural and subtalar joints of the right foot were analyzed barefoot and in an athletic walking shoe.

RESULTS

Shod talocrural position at heel strike was 6.0° of dorsiflexion and shod peak talocrural plantarflexion was 4.2°. Barefoot talocrural plantarflexion at heel strike was 4.2° and barefoot peak talocrural plantarflexion was 10.9°. Shod subtalar position at heel strike was 2.6° of plantarflexion and peak subtalar dorsiflexion was 1.5°. The barefoot subtalar joint at heel strike was in 0.4° dorsiflexion and barefoot peak subtalar dorsiflexion was 3.5°. As the result of wearing shoes, average walking speed and stride length increased and average cadence decreased. Comparing barefoot to shod walking there was a statistical significance in talocrural dorsiflexion and at heel strike and peak talocrural dorsiflexion, subtalar plantarflexion at heel strike and peak subtalar dorsiflexion, walking speed, stride length, and cadence.

SIGNIFICANCE

This work demonstrates the ability to directly measure talocrural and subtalar kinematics of shod walking using fluoroscopy. Future work using this methodology can be used to increase understanding of hindfoot kinematics during a variety of non-barefoot activities.

Mobility in osteogenesis imperfecta: a multicenter North American study

PURPOSE

Osteogenesis imperfecta (OI) is a genetic connective tissue disorder that causes bone fragility. Phenotypic severity influences ability to walk, however, little is known about ambulatory characteristics of individuals with OI, especially in more severe forms. The purpose of this work was to characterize mobility in OI using standard clinical assessment tools and determine if patient characteristics could be used to predict mobility outcomes.

METHODS

We collected mobility data at five clinical sites to analyze the largest cohort of individuals with OI (n = 491) to date. Linear mixed models were developed to explore relationships among subject demographics and mobility metrics.

RESULTS

Results showed minor limitations in the mild group while the more severe types showed more significant limitations in all mobility metrics analyzed. Height and weight were shown to be the most significant predictors of mobility. Relationships with mobility and bisphosphonates varied with OI type and type used (oral/IV).

CONCLUSION

These results are significant to understanding mobility limitations of specific types of OI and beneficial when developing rehabilitation protocols for this population. It is important for physicians, patients, and caregivers to gain insight into severity and classification of the disease and the influence of disease-related characteristics on prognosis for mobility.

Kinematic foot types in youth with pes planovalgus secondary to cerebral palsy

BACKGROUND

Kinematic variability of the foot and ankle segments exists during ambulation among individuals with pes planovalgus (PPV) secondary to cerebral palsy (CP). Clinicians have previously recognized such variability through classification schemes to identify subgroups of individuals, but have been unable to identify kinematic foot types.

RESEARCH QUESTION

The purpose of this work was to identify kinematic foot types among children with PPV secondary to CP using 3-dimensional multi-segment foot and ankle kinematics during gait as inputs for principal component analysis (PCA) and K-means cluster analysis.

METHODS

In a single assessment session, multi-segment foot and ankle kinematics using the Milwaukee Foot Model (MFM) were collected in 31 children/adolescents with pes planovalgus (49 feet) and 16 typically developing (TD) children/adolescents (31 feet). PCA was used as a data reduction technique on 34 kinematic variables. K-means cluster analysis was performed on the identified principal components (PCs) and one-way analyses of variance (ANOVA) was done to determine the effect of subgroup membership on PC scores.

RESULTS

The PCA reduced the kinematic variables to seven PCs which accounted for 91% of the total variance. Six distinct kinematic foot types were identified by the cluster analysis. The foot types showed unique kinematic characteristics in both the hindfoot and forefoot.

SIGNIFICANCE

This study provides further evidence of kinematic variability in the foot and ankle during ambulation associated with pes planovalgus secondary to CP. The specific contributions of the hindfoot and forefoot would not have been detected using a single segment foot model. The identification of kinematic foot types with unique foot and ankle characteristics has the potential to improve treatment since patients within a foot type are likely to benefit from similar intervention(s).

Effects of Spinal Fusion for Idiopathic Scoliosis on Lower Body Kinematics During Gait

STUDY DESIGN

Prospective.

OBJECTIVES

The purpose of this study was to compare gait among patients with scoliosis undergoing posterior spinal fusion and instrumentation (PSFI) to typically developing subjects and determine if the location of the lowest instrumented vertebra impacted results.

SUMMARY OF BACKGROUND DATA

PSFI is the standard of care for correcting spine deformities, allowing the preservation of body equilibrium while maintaining as many mobile spinal segments as possible. The effect of surgery on joint motion distal to the spine must also be considered. Very few studies have addressed the effect of PSFI on activities such as walking and even fewer address how surgical choice of the lowest instrumented vertebra (LIV) influences possible motion reduction.

METHODS

Individuals with scoliosis undergoing PSFI (n = 38) completed gait analysis preoperatively and at postoperative years 1 and 2 along with a control group (n = 24). Comparisons were made with the control group at each time point and between patients fused at L2 and above (L2+) versus L3 and below (L3-).

RESULTS

The kinematic results of the AIS group showed some differences when compared to the Control Group, most notably decreased range of motion (ROM) in pelvic tilt and trunk lateral bending. When comparing the LIV groups, only minor differences were observed, and the results showed decreased coronal trunk and pelvis ROM at the one-year visit and decreased hip rotation ROM at the two-year visit in the L3- group.

CONCLUSIONS

Patients with AIS showed decreased ROM preoperatively with further decreases postoperatively. These changes remained relatively consistent following the two-year visit, indicating that most kinematic changes occurred in the first year following surgery. Limited functional differences between the two LIV groups may be due to the lack of full ROM used during normal gait, and future work could address tasks that use greater ROM.

LEVEL OF EVIDENCE

Level II.

Distribution of segmental foot kinematics in patients with degenerative joint disease of the ankle

Degenerative joint disease (DJD) of the ankle is a debilitating chronic disease associated with severe pain and dysfunction resulting in antalgic gait alteration. Little information is available about segmental foot and ankle motion distribution during gait in ankle osteoarthritis. The aim of the current study was to dynamically characterize segmental foot and ankle kinematics of patients with severe ankle arthrosis requiring total ankle replacement. This was a prospective study involving 36 (19 M, 17 F) adult patients with a clinical diagnosis of ankle arthrosis ("DJD" group) and 36 (23 M, 13 F) healthy subjects ("Control" group). Motion data were collected at 120 Hz using a 3-D motion camera system at self-selected speed along a 6-m walkway and processed using the Milwaukee Foot Model (MFM). The SF-36 Health Survey and Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale were administered to evaluate functional levels. Findings include decreases in walking speed, cadence, stride length and swing phase, and reduced outcomes scores (SF-36 and AOFAS). Multisegemental motion in patients with ankle DJD demonstrates significant changes in foot mechanics characterized by altered segment kinematics and significant reduction in dynamic ROM at the tibia, hindfoot, forefoot, and hallux when compared to controls. The results demonstrate decreased temporal-spatial parameters and low outcomes scores indicative of functional limitations. Statement of clinical significance: Altered segment kinematics and reduced overall range of motion demonstrate how a single joint pathology affects kinematic distribution in the other segments of the foot and ankle and alters patients' overall gait. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1739-1746, 2018.

Sagittal Subtalar and Talocrural Joint Assessment During Ambulation With Controlled Ankle Movement (CAM) Boots

BACKGROUND

The purpose of the current study was to determine sagittal plane talocrural and subtalar kinematic differences between barefoot and controlled ankle movement (CAM) boot walking. This study used fluoroscopic images to determine talar motion relative to tibia and calcaneal motion relative to talus.

METHODS

Fourteen male subjects (mean age 24.1 ± 3.5 years) screened for normal gait were tested. A fluoroscopy unit was used to collect images at 200 Hz during stance. Sagittal motion of the talocrural and subtalar joints were analyzed barefoot and within short and tall CAM boots.

RESULTS

Barefoot talocrural mean maximum plantar and dorsiflexion were 9.2 ± 5.4 degrees and -7.5 ± 7.4 degrees, respectively; short CAM boot mean maximum plantar and dorsiflexion were 3.2 ± 4.0 degrees and -4.8 ± 10.2 degrees, respectively; and tall CAM boot mean maximum plantar and dorsiflexion were -0.2 ± 3.5 degrees and -2.4 ± 5.1 degrees, respectively. Talocrural mean range of motion (ROM) decreased from barefoot (16.7 ± 5.1 degrees) to short CAM boot (8.0 ± 4.9 degrees) to tall CAM boot (2.2 ± 2.5 degrees). Subtalar mean maximum plantarflexion angles were 5.3 ± 5.6 degrees for barefoot walking, 4.1 ± 5.9 degrees for short CAM boot walking, and 3.0 ± 4.7 degrees for tall CAM boot walking. Mean minimum subtalar plantarflexion angles were 0.7 ± 3.2 degrees for barefoot walking, 0.7 ± 2.9 degrees for short CAM boot walking, and 0.1 ± 4.8 degrees for tall CAM boot walking. Subtalar mean ROM decreased from barefoot (4.6 ± 3.9 degrees) to short CAM boot (3.4 ± 3.8 degrees) to tall CAM boot (2.9 ± 2.6 degrees).

CONCLUSION

Tall and short CAM boot intervention was shown to limit both talocrural and subtalar motion in the sagittal plane during ambulation. The greatest reductions were seen with the tall CAM boot, which limited talocrural motion by 86.8% and subtalar motion by 37.0% compared to barefoot. Short CAM boot intervention reduced talocrural motion by 52.1% and subtalar motion by 26.1% compared to barefoot.

CLINICAL RELEVANCE

Both short and tall CAM boots reduced talocrural and subtalar motion during gait. The short CAM boot was more convenient to use, whereas the tall CAM boot more effectively reduced motion. In treatments requiring greater immobilization of the talocrural and subtalar joints, the tall CAM boot should be considered.

Segmental kinematic analysis of planovalgus feet during walking in children with cerebral palsy

Pes planovalgus (flatfoot) is a common deformity among children with cerebral palsy. The Milwaukee Foot Model (MFM), a multi-segmental kinematic foot model, which uses radiography to align the underlying bony anatomy with reflective surface markers, was used to evaluate 20 pediatric participants (30feet) with planovalgus secondary to cerebral palsy prior to surgery. Three-dimensional kinematics of the tibia, hindfoot, forefoot, and hallux segments are reported and compared to an age-matched control set of typically-developing children. Most results were consistent with known characteristics of the deformity and showed decreased plantar flexion of the forefoot relative to hindfoot, increased forefoot abduction, and decreased ranges of motion during push-off in the planovalgus group. Interestingly, while forefoot characteristics were uniformly distributed in a common direction in the transverse plane, there was marked variability of forefoot and hindfoot coronal plane and hindfoot transverse plane positioning. The key finding of these data was the radiographic indexing of the MFM was able to show flat feet in cerebral palsy do not always demonstrate more hindfoot eversion than the typically-developing hindfoot. The coronal plane kinematics of the hindfoot show cases planovalgus feet with the hindfoot in inversion, eversion, and neutral. Along with other metrics, the MFM can be a valuable tool for monitoring kinematic deformity, facilitating clinical decision making, and providing a quantitative analysis of surgical effects on the planovalgus foot.

THA Retrievals: The Need to Mark the Anatomic Orientation of the Femoral Head

The hypothesis of this study was that the rotational orientation of femoral head damage would greatly affect the volumetric wear rate of the opposing polyethylene (PE) liner. Damage on twenty retrieved cobalt-chromium femoral heads was simulated in a validated damage-feature-based finite element model. For each individual retrieval, the anatomic orientation of the femoral head about the femoral neck axis was systematically varied, in 30° increments. The PE wear rate differential between the maximum- versus minimum-wear orientations was often sizable, as high as 7-fold. Knowing the correct femoral head anatomic orientation is therefore important when analyzing the effects of femoral head damage on PE liner wear. Surgeons retrieving modular femoral heads should routinely mark the anatomic orientation of those components.

Modeling polyethylene wear acceleration due to femoral head dislocation damage

Scratching, scraping, and metal transfer to femoral heads commonly accompany acetabular shell contact during dislocation and closed reduction maneuvers. While head damage conceptually leads to accelerated wear, reports on this subject are mainly anecdotal, and differ widely on the potency of such effect. Towards better understanding this relationship, a physically validated finite element (FE) model was used to compute polyethylene wear acceleration propensity of specific head damage patterns on thirteen retrievals. These FE models estimated wear increases averaging half an order of magnitude when compared to simulations for undamaged heads. There was no correlation between the number of dislocations sustained and wear acceleration. These results underscore the importance of implant-gentle closed reduction, and heightened wear monitoring of successfully reduced dislocation patients.

Distinctive damage patterns on THA metal bearing surfaces: case studies

Retrieval analysis of total joint arthroplasty components has primarily focused on assessing wear or other damage to polyethylene components. As damage to the opposing bearing surface can accelerate polyethylene wear and damage, and especially with the use of hard-on-hard articulations, retrieval analysis benefits from incorporating evaluation of hard bearing surfaces as well. The purpose of this study is to report six case studies of metal bearing surfaces with distinctive damage patterns, to interpret them in the context of adverse events plausibly responsible for their creation, and to suggest their likely clinical or scientific significance. The specific damage patterns reported here are 1) extensive scraping, 2) circumferential discoloration, 3) a long chain of periodic micro-indentations, 4) pitting with deposits, 5) scratches with small-radius directional changes, and 6) indentation with scraping.

Enhancing damage visibility on metallic bearing surfaces: a simple technique for photography and viewing

Damage to metallic bearing surfaces typically involves scratches, scrapes, metal transfer, and organic deposits. This damage can cause accelerated wear of the opposing surface and subsequent implant failure. Photography and viewing of metallic bearing surfaces, for documenting this damage, are hindered by optical reflectivity. This note demonstrates a simple, practical technique for metallic bearing surface photography and viewing that minimizes this reflectivity problem, that does not involve any modification of the bearing surface, and that allows for improved observation and documentation of overall damage. When the metallic bearing surface is placed within a tube of translucent material, the appearance of damage on that bearing surface is dramatically enhanced, showing up against a smooth, even background with excellent contrast and with fine detail achievable.

A novel formulation for scratch-based wear modelling in total hip arthroplasty

Damage to the femoral head in total hip arthroplasty often takes the form of discrete scratches, which can lead to dramatic wear acceleration of the polyethylene (PE) liner. Here, a novel formulation is reported for finite element (FE) analysis of wear acceleration due to scratch damage. A diffused-light photography technique was used to globally locate areas of damage, providing guidance for usage of high-magnification optical profilometry to determine individual scratch morphology. This multiscale image combination allowed comprehensive input of scratch-based damage patterns to an FE Archard wear model, to determine the wear acceleration associated with specific retrieval femoral heads. The wear algorithm imposed correspondingly elevated wear factors on areas of PE incrementally overpassed by individual scratches. Physical validation was provided by agreement with experimental data for custom-ruled scratch patterns. Illustrative wear acceleration results are presented for four retrieval femoral heads.

Edge-loading severity as a function of cup lip radius in metal-on-metal total hips--a finite element analysis

While favorable tribological properties and allowance for larger femoral head sizes have made metal-on-metal (MoM) bearings an increasingly popular choice for total hip arthroplasty, concerns have mounted regarding adverse reactions to metal wear debris and ions. MoM cups differ from conventional polyethylene cups in terms of edge profile design and reductions from full hemisphericity, suggesting differences in loading at or near the cup edge, especially during subluxation events. Finite element analysis was used to investigate the effects of cup orientation and lip edge curvature on damage propensity for edge or near-edge loading during subluxation. Increased cup lip radius (resulting in reduced articular arc) had a detrimental effect upon subluxation-free hip range of motion and upon dislocation resistance. Contact stresses near the cup edge demonstrated complex relationships between edge radius and cup orientation, with peak stresses being influenced by both variables. The tendency for scraping wear at the egress site demonstrated similarly complex dependencies. These data indicate that acetabular cup design is an important determinant of edge and near-edge loading damage propensity.